JP2007334372A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which the transition from splay alignment to bend alignment can be fast performed. <P>SOLUTION: An active matrix type liquid crystal display device is provided comprising a splay-alignment liquid crystal cell in which the liquid crystal on upper and lower boundaries of a liquid crystal layer disposed between an array substrate having pixel electrodes and a counter substrate having a common electrode are subjected to parallel alignment to each other with pretilt angles in opposite signs; wherein the liquid crystal is in splay alignment when no voltage is applied and is subjected to an initialization process of inducing transition from the splay alignment to bend alignment by applying a voltage prior to driving liquid crystal display, and then liquid crystal display is driven in the initialized bend alignment state. The liquid crystal display device is characterized in that: one pixel has at least one lateral electric field application portion for transition excitation so as to generate a lateral electric field by the lateral electric field application portion; and a voltage is continuously or intermittently applied between the pixel electrode and the common electrode to generate transition seeds in each pixel to induce transition from splay alignment to bend alignment in the whole pixels. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an OCB mode liquid crystal display device with a high-speed response and a wide field of view for displaying television images, personal computers, and multimedia images, a manufacturing method thereof, and a driving method of the liquid crystal display device.

  Conventionally, as a liquid crystal display device, for example, a twisted nematic (TN) mode liquid crystal display element using a nematic liquid crystal having a positive dielectric anisotropy has been put into practical use as a liquid crystal display mode, but the response is slow. There are disadvantages such as narrow viewing angle. There are also display modes such as ferroelectric liquid crystal (FLC) and anti-ferroelectric liquid crystal that have a fast response and a wide viewing angle. However, they have major drawbacks in image sticking, shock resistance, and temperature dependence of characteristics. . In addition, although there is an in-plane switching (IPS) mode in which the viewing angle is extremely wide and the liquid crystal molecules are driven in a horizontal electric field in the plane, the response is slow, the aperture ratio is low, and the luminance is low. When trying to display full-color movies on a large screen, a liquid crystal mode with a wide field of view, high brightness, and high-speed display performance is required, but there is currently a practical liquid crystal display mode that satisfies this perfectly at the same time. do not do.

  Conventionally, as a liquid crystal display device aiming at high brightness with at least a wide field of view, there is one in which the above-mentioned TN mode liquid crystal region is divided into two orientations and the viewing angle is expanded vertically (SID92 DIGEST P798-801). That is, nematic liquid crystal having positive dielectric anisotropy is used in each display pixel of the liquid crystal display device, and two liquid crystal regions having different orientation directions of liquid crystal molecules are formed in the TN mode. It expands the viewing angle.

  FIG. 48 is a conceptual diagram of the configuration of the conventional liquid crystal display device. In FIG. 48, 701 and 702 are glass substrates, 703 and 704 are electrodes, and 705, 705 ', 706, and 706' are alignment films. In one alignment region A, nematic liquid crystal molecules 707 and 707 ′ having a slight dielectric anisotropy slightly inclined from the opposing upper and lower substrate interfaces form large and small pretilt angles, and in the other alignment region B, The size of the pretilt angle with respect to the upper and lower substrate interfaces is set opposite to that of the alignment region A. The large and small pretilt angles are set to have a difference of several degrees. As an example of a conventional manufacturing method for forming alignment regions having different pretilt angles on the upper and lower substrates, a photoresist is applied to the alignment film, masking is performed using a photolithographic technique, and a desired alignment film surface is rubbed in a predetermined direction. There is a method of repeating the work to do. In the above configuration, as shown in FIG. 48, the orientation of the liquid crystal molecules in the central portion of the liquid crystal layer is opposite to each other in the orientation regions A and B, and the liquid crystal molecules in each orientation region rise in reverse with voltage application. Thus, the refractive index anisotropy is averaged with respect to the incident light, and the viewing angle can be expanded. In the above-described conventional orientation-divided TN mode, the viewing angle is larger than in the normal TN mode, and the vertical viewing angle is about ± 35 degrees with a contrast of 10.

  However, the response speed is about 50 mS with essentially no change from the TN mode. As described above, the viewing angle and response are insufficient in the conventional two-divided TN mode.

  In addition, there is a liquid crystal display mode that uses a so-called homeotropic alignment mode in which liquid crystal molecules are aligned almost vertically at the alignment film interface, and there is a liquid crystal display device with a wide field of view and high-speed response by adding a film retardation plate and alignment division technology. However, the response speed between binary values of black and white takes about 25 ms, especially the response speed between gray gradations is slow at 50 to 80 ms, which is longer than about 1/30 s, which is called the visual speed of human eyes, and the moving image flows. Looks.

  On the other hand, a bend alignment type liquid crystal display device (OCB mode liquid crystal display device) using a change in refractive index due to a change in the rising angle of each liquid crystal molecule in a state where the liquid crystal molecules between the substrates are bend aligned has been proposed. Yes. The liquid crystal molecules with bend alignment are much faster in the on-state and off-state alignment change speed than the on-off state of the TN type liquid crystal display device, and the response speed is high. It can be a display device. Furthermore, since the liquid crystal display device of the bend alignment type is entirely bend-aligned between the upper and lower substrates, the bend alignment type liquid crystal display device can self-compensate in terms of optical phase difference, and also compensates for phase difference with a film phase difference plate. This has the potential to become a wide-field LCD device.

  By the way, the above-mentioned liquid crystal display device is usually produced by placing liquid crystal molecules in a splay alignment state between substrates under no voltage. In order to change the refractive index using bend alignment, the entire display unit needs to be uniformly transferred from the splay alignment state to the bend alignment state before the use of the liquid crystal display device is started. When a voltage is applied between the opposing display electrodes, the place where the transition nuclei from the splay alignment to the bend alignment are generated is not uniform, such as around the dispersed spacers, or alignment unevenness, scratches, etc. at the alignment film interface. . Further, since the transition nucleus is not always generated from a certain place, a display defect is likely to occur when the transition occurs or does not occur. Therefore, it is extremely important that the entire display unit is uniformly transferred from the splay alignment to the bend alignment before the start of use.

  However, conventionally, even if a simple AC voltage is applied, the transition does not occur or even if it occurs, it takes a very long transition time.

  An object of the present invention is to provide a bend alignment type liquid crystal that is capable of bend alignment transition almost certainly and has no display defects due to completion of the transition in a very short time, has a high response speed and is suitable for moving image display and has a wide field of view. A display device, a manufacturing method thereof, and a driving method of a liquid crystal display device are proposed.

  According to the first aspect of the present invention, the pretilt angles of the liquid crystal at the upper and lower interfaces of the liquid crystal layer disposed between the array substrate having pixel electrodes and the counter substrate having the common electrode are splay alignment in which the pretilt angles are opposite to each other, In this liquid crystal cell, splay alignment is applied when no voltage is applied, and prior to liquid crystal display driving, an initialization process is performed to change from splay alignment to bend alignment by applying voltage, and in this initialized bend alignment state In an active matrix type liquid crystal display device that performs liquid crystal display driving, a horizontal electric field application unit for at least one transition excitation is provided in one pixel, and a horizontal electric field is generated by the horizontal electric field application unit. A voltage is applied continuously or intermittently between the common electrodes to generate transition nuclei for each pixel and to transfer the entire pixel from splay alignment to bend alignment. It is characterized.

  With the above configuration, the following operations are performed.

  A voltage sufficiently higher than the transition voltage is applied between the pixel electrode and the common electrode, and at least one transition excitation lateral electric field application unit provided in one pixel applies a lateral electric field to the liquid crystal layer, thereby The horizontal electric field application part becomes the starting point from the splay alignment of the liquid crystal layer in the pixel to the bend alignment (that is, the transition nucleus can be surely generated in the liquid crystal layer around the horizontal electric field application part), and thus the splay alignment quickly. The transition from orientation to bend orientation can be performed.

  According to a second aspect of the present invention, in the liquid crystal display device according to the first aspect, the direction of the horizontal electric field generated by the horizontal electric field applying unit is substantially orthogonal to the alignment processing direction.

  With this configuration, a horizontal electric field is applied in a substantially orthogonal direction from the lateral electric field application unit in the alignment state direction of the liquid crystal molecules in the liquid crystal layer. Nuclei are generated, and the transition from the splay alignment to the bend alignment can be performed quickly.

  According to a third aspect of the present invention, in the liquid crystal display device according to the first aspect, the lateral electric field applying unit is an electrode deforming unit in which a peripheral portion of the pixel electrode is deformed into irregularities in a plane parallel to the substrate surface. It is characterized by being.

  With the above configuration, the following operations are performed.

  Between the horizontal electric field applying part composed of an electrode deforming part in which the periphery of the pixel electrode is deformed unevenly in a plane parallel to the substrate surface, and a signal electrode line or a gate electrode line existing on the side of the horizontal electric field applying part The electric field is concentrated, and therefore, the horizontal electric field generated in that case is stronger than the horizontal electric field generated between the pixel electrode not having the horizontal electric field applying portion and the signal electrode line or the gate electrode line. Therefore, the transition electric field can be reliably generated in the liquid crystal layer by the lateral electric field generated by the presence of the lateral electric field applying section, and the alignment transition from the splay alignment to the bend alignment can be performed quickly.

  According to a fourth aspect of the present invention, in the liquid crystal display device according to the first aspect, the lateral electric field applying unit is an electrode line obtained by deforming the signal electrode line or the gate electrode line into irregularities in a plane parallel to the substrate surface. It is a deformation part.

  With the above configuration, the following operations are performed.

  The same effect as that of the invention of claim 3 is achieved by the presence of the electrode line deforming portion of one or both of the electrode lines.

  The invention according to claim 5 is the liquid crystal display device according to claim 1, wherein the lateral electric field applying unit deforms the peripheral portion of the pixel electrode into irregularities in a plane parallel to the substrate surface, and copes with the irregularities. Thus, the electrode / electrode line deformed portion is formed by deforming the signal electrode line or the gate electrode line into irregularities.

  With the above configuration, the following operations are performed.

  An electrode / electrode line deforming portion in which at least one side of the pixel electrode is deformed into a concavo-convex portion in a plane parallel to the substrate surface, and correspondingly, the signal electrode line or the gate electrode line or both are deformed to be uneven. The lateral electric field applying unit is the same as the third aspect of the invention.

  A sixth aspect of the present invention is the liquid crystal display device according to the first aspect, wherein the lateral electric field applying section is formed by deforming the lateral electric field applying lines into irregularities in a plane parallel to the substrate surface. An application line deforming portion, and the horizontal electric field application line is disposed in the same direction through an insulating film on an upper layer or a lower layer of at least one of the signal electrode line or the gate electrode line, and the signal electrode line or the gate electrode It is characterized by being connected to a drive circuit to which a line is connected.

  By adopting the above configuration, the horizontal electric field application line is a line dedicated to horizontal electric field application, and is disposed on an upper layer or a lower layer of at least one of the signal electrode line or the gate electrode line via an insulating film. There is flexibility in the shape of continuously forming irregularities on the side portion of the horizontal electric field application line. Further, since the horizontal electric field applying line overlaps with the signal electrode line or the gate electrode line, it absorbs less light, and the aperture ratio of the pixel does not decrease. Therefore, it is possible to make a redundant design with a degree of freedom in design.

  A seventh aspect of the invention is the liquid crystal display device according to the sixth aspect of the invention, wherein the horizontal electric field applying line is cut off from the drive circuit during normal liquid crystal display after orientation transition.

  With this configuration, the horizontal electric field application line is cut off from the drive circuit during normal liquid crystal display after orientation transition. In this case, the horizontal electric field application line formed on the horizontal electric field application line A horizontal electric field does not occur between the pixel electrodes. Therefore, liquid crystal alignment is not disturbed during normal liquid crystal display, and a liquid crystal display device showing a good liquid crystal display state can be obtained.

  The invention according to claim 8 is a splay alignment liquid crystal cell in which the pretilt angles of the liquid crystal at the upper and lower interfaces of the liquid crystal layer between the array substrate and the counter substrate are opposite to each other and aligned in parallel with each other. Prior to the liquid crystal display driving, an initialization process for changing from the splay alignment to the bend alignment is performed by applying a voltage, and the active matrix liquid crystal display that drives the liquid crystal display in the initialized bend alignment state. In the apparatus, one pixel has at least one of a pixel electrode or a common electrode in which a defect portion is formed at least at one place for applying a lateral electric field for transfer excitation.

  With the above configuration, the following operations are performed.

  Since each pixel has at least one of a pixel electrode or a common electrode in which a defect portion is formed in at least one place for applying a transverse electric field for transfer excitation, an electric field distortion (an oblique electric field) is formed at the edge of the defect portion. ) Occurs. Accordingly, the oblique electric field receives a twisting force of the liquid crystal molecules, so that transition nuclei are reliably generated, and the transition from the splay alignment to the bend alignment is accelerated.

  As described above, according to the present invention, a voltage sufficiently larger than the transition voltage is applied between the pixel electrode and the common electrode, and at least one transition excitation lateral electric field application unit provided in one pixel is provided in the liquid crystal layer. By applying a lateral electric field to the liquid crystal layer, the horizontal electric field application unit becomes a starting point from the splay alignment to the bend alignment of the liquid crystal layer in the pixel (that is, the transition nucleus is surely generated in the liquid crystal layer around the horizontal electric field application unit. Therefore, the orientation transition from the splay orientation to the bend orientation can be performed quickly.

  The present invention was obtained as a result of paying attention to the transition mechanism from splay alignment to bend alignment described below in a liquid crystal display device including a bend alignment type OCB cell. Therefore, first, the transfer mechanism will be described in detail, and then the specific contents of the present invention will be described using embodiments.

  FIG. 1 is a perspective view showing a part of a liquid crystal display device having a bend-oriented OCB cell. Referring to FIG. 1, the configuration of a liquid crystal display device having a bend-oriented OCB cell will be briefly described. A liquid crystal layer 13 including liquid crystal molecules 12 is disposed between substrates 10 and 11 arranged in parallel to each other. Has been inserted. Although not shown in the drawing, display electrodes for applying an electric field to the liquid crystal layer 13 and alignment films for regulating the alignment of liquid crystal molecules are formed on the mutually opposing surfaces of the substrates 10 and 11, respectively. Yes. As shown in the figure, the alignment film is pre-tilted with about 5 to 7 degrees of liquid crystal molecules 12 in the vicinity of the substrate interface, and is aligned so that the alignment directions in the substrate surface are in the same direction, that is, parallel alignment. . As the distance from the surfaces of the substrates 10 and 11 increases, the liquid crystal molecules 12 gradually rise to a bend alignment in which the tilt angle of the liquid crystal molecules is 90 degrees at approximately the center in the thickness direction of the liquid crystal layer 13. Polarizing plates 15 and 16 and optical compensation plates 17 and 18 are arranged outside the substrates 10 and 11, and the two polarizing plates 15 and 16 are arranged such that their polarization axes are orthogonal to or parallel to each other. The axis and the orientation direction of the liquid crystal molecules are arranged at an angle of 45 degrees. Then, using the difference in refractive index anisotropy of the liquid crystal layer between the on state where a high voltage is applied and the off state where a low voltage is applied, the polarization state is changed through the polarizing plate and the optical compensator. The transmittance is controlled and displayed.

  In the liquid crystal display device having the bend alignment type OCB cell, since the liquid crystal layer is in the splay alignment before use, the liquid crystal layer is changed from the splay alignment state to the bend alignment state by applying a voltage before driving the liquid crystal display. It is necessary to transfer to.

  FIG. 2 schematically shows the mechanism of the alignment transition in which the liquid crystal layer transitions from the splay alignment to the bend alignment when a high voltage equal to or higher than the transition critical voltage is applied for the alignment transition.

  FIG. 2 is a cross-sectional view of a liquid crystal cell conceptually showing a liquid crystal molecule arrangement by schematically showing liquid crystal molecules when two substrates are arranged in parallel.

  FIG. 2A shows an initial spray arrangement state. When there is no electric field between the substrates, the major axis of the liquid crystal molecules 12 at the center of the liquid crystal layer 13 is in a splay alignment state with a low energy state that is substantially parallel to the substrate surface. Here, for convenience of explanation, liquid crystal molecules parallel to the substrate are denoted by reference numeral 12a.

  Next, FIG. 2B shows a liquid crystal molecule alignment state when a high voltage is started to be applied between electrodes (not shown) formed on the substrates 10 and 11. The liquid crystal molecules 12 at the center in the liquid crystal layer 13 begin to slightly tilt due to the electric field, and as a result, the liquid crystal molecules 12a oriented parallel to the substrate surface move toward one substrate surface (to the substrate 11 side in the figure). Go.

  Next, FIG.2 (c) shows a liquid crystal molecule arrangement state when time passes, after applying a voltage. The liquid crystal molecules 12 at the center of the liquid crystal layer 13 are further tilted with respect to the substrate surface. On the other hand, the liquid crystal molecules 12a oriented substantially parallel to the substrate surface come near the substrate interface and are strongly regulated from the alignment film. Receive power.

  Next, FIG.2 (d) shows the liquid crystal molecular arrangement | sequence state in which the energy state shifted to the bend alignment. The liquid crystal molecules 12 at the center of the liquid crystal layer 13 are perpendicular to the substrate surface, and the liquid crystal molecules in contact with the alignment film (not shown) interface on the substrate 10 receive a strong regulating force from the alignment film and are tilted. The state is maintained, and at this time, the liquid crystal molecules 12a oriented parallel to the substrate surface existing in FIGS.

  When a further time elapses from FIG. 2D, the alignment state shifts to the bend alignment state shown in FIG. 1 between the substrates, and the transition is completed.

  As described above, the transition from the splay alignment to the bend alignment that occurs when a voltage is applied can be considered as described above.

  However, the place where this occurs usually does not occur in the entire liquid crystal layer in the substrate surface at once, but is a part where energy is easily transferred in a part of the alignment region, and is usually a spacer dispersed in the gap. Transition nuclei are generated in the surrounding area and the alignment uneven part, and the bend alignment region is expanded therefrom. Accordingly, in order to change the alignment in the OCB cell, a transition nucleus is generated in at least a part of the liquid crystal layer in the substrate surface, and a bend alignment state having higher energy than the splay alignment state by applying energy from the outside. It is necessary to transition to and maintain this.

  As a result of considering the mechanism of such alignment transition, the present inventors have developed a liquid crystal display device that reliably generates transition nuclei and completes the transition in an extremely short time, a manufacturing method thereof, and a driving method of the liquid crystal display device. It came to be completed. Specific contents will be described based on the embodiment.

  (Reference form 1)

  FIG. 3 is a conceptual diagram of a pixel unit configuration according to the driving method of the liquid crystal display device according to the first embodiment of the present invention. First, the configuration of a liquid crystal display device related to the driving method according to the first embodiment will be described with reference to FIG. The liquid crystal display device according to the first embodiment has the same configuration as a liquid crystal display device including a general OCB cell with respect to the configuration excluding the drive circuit unit. That is, it has a pair of glass substrates 20 and 21 and a liquid crystal layer 26 sandwiched between the glass substrates 20 and 21. The glass substrates 20 and 21 are arranged to face each other with a certain interval. A common electrode 22 made of an ITO transparent electrode is formed on the inner surface of the glass substrate 20, and a pixel electrode 23 made of an ITO transparent electrode is formed on the inner surface of the glass substrate 21. Alignment films 24 and 25 made of a polyimide film are formed on the common electrode 22 and the pixel electrode 23, and the alignment films 24 and 25 are aligned so that the alignment directions are parallel to each other. A liquid crystal layer 26 made of P-type nematic liquid crystal is inserted between the alignment films 24 and 25. The pretilt angle of the liquid crystal molecules on the alignment films 24 and 25 is set to about 5 degrees, and the critical voltage for transition from the splay alignment to the bend alignment is set to 2.5V. The retardation of the optical compensator 29 is selected so that white or black is displayed in the on state. In FIG. 1, reference numerals 27 and 28 denote polarizing plates.

  In the figure, reference numeral 30 denotes an alignment transition driving circuit, and reference numeral 31 denotes a liquid crystal display driving circuit. 32a and 32b are switch circuits, and 33 is a switch control circuit for controlling switching of the switching mode of the switch circuits 32a and 32b. The switch circuit 32a includes two individual contacts P1, P2, and one common contact Q1, and the switch circuit 32b includes two individual contacts P3, P4 and one common contact Q2. Yes. The common contact Q1 is connected to one of the individual contacts P1 and P2 in response to the switch switching signal S1 from the switch control circuit 33. Similarly, the common contact Q2 is connected to any of the individual contacts P3 and P4 in response to the switch switching signal S2 from the switch control circuit 33. In a state where the common contact Q1 is connected to the individual contact P1 and the common contact Q2 is connected to the individual contact P3, the drive voltage from the alignment transition drive circuit 30 is applied to the electrodes 22 and 23. In the state where the common contact Q1 is connected to the individual contact P2 and the common contact Q2 is connected to the individual contact P4, the drive voltage from the liquid crystal display drive circuit 33 is applied to the electrodes 22 and 23.

  Next, a driving method according to the first embodiment will be described.

  First, prior to liquid crystal display driving based on the original image signal, initialization processing is performed for transition to bend alignment. First, when the power is turned on, the switch control circuit 33 outputs switch switching signals S1, S2 to the switch circuits 32a, 32b, the common contact Q1 is connected to the individual contact P1, and the common contact Q2 is connected to the individual contact P3. And As a result, the driving voltage shown in FIG. 4 is applied between the electrodes 22 and 23 from the alignment transition driving circuit 30. This drive voltage is an AC voltage in which an AC rectangular wave voltage A is superimposed on a bias voltage B as shown in FIG. 4, and the value of the drive voltage is necessary to cause a transition from a splay alignment to a bend alignment. It is set to a voltage value larger than the critical voltage, which is a minimum voltage. By applying such a drive voltage, the transition time can be significantly shortened compared to the conventional example in which a simple AC voltage is applied. The reason why the transition time is shortened will be described later. In this way, the initialization process regarding the transition to the bend alignment is completed.

  Next, when the transition time during which the entire electrode surface completely transitions to the bend orientation elapses, the switch control circuit 33 outputs a switching signal S1 for switching the common contact Q1 to the individual contact P2 side to the switch circuit 32a and the common contact Q2 individually. A switching signal S2 for switching to the contact P4 side is output to the switch circuit 32b. As a result, the common contact Q1 and the individual contact P2 are connected, and the common contact Q2 and the individual contact P4 are connected, and the drive signal voltage from the liquid crystal display drive circuit 31 is applied between the electrodes 22 and 23. The desired image is displayed. Here, the liquid crystal display driving circuit 31 maintains the bend alignment state by setting a rectangular wave voltage of 2.7 V at 30 Hz to turn it off, and turns on the rectangular wave voltage 7 V at 30 Hz to display the OCB panel. .

  Next, the present inventor manufactured a liquid crystal display device having the above-described configuration and conducted an initialization process experiment with the above driving method. The experimental conditions are as follows.

  The electrode area was 2 cm 2, the cell gap was about 6 μm, the frequency of the AC rectangular wave voltage A was 30 Hz, and the amplitude was ± 4V.

  Under the above conditions, the transition times were measured when the bias voltage B was set to four types of voltages of 0V, 2V, 4V, and 5V. The results are shown in FIG. Here, the transition time means the time required to complete the alignment transition in the entire area of the electrode area.

  As apparent from FIG. 5, when the bias voltage B is 0 V, the transition time is 140 seconds. On the other hand, when the bias voltage B is 4 V, the transition time can be shortened to 8 seconds. This is because the bias voltage overlaps the liquid crystal molecule orientation of the liquid crystal layer due to the bias voltage, causing a shift between the substrates as shown in FIG. 2 (d), generating more transition nuclei, and further increasing the effective voltage. It is thought that the transition time was increased by up.

  As described above, by continuously applying the AC voltage with bias superimposed thereon, the transition time can be shortened compared to the case of simple AC voltage application.

  In the above experimental example, the AC rectangular wave voltage signal has a frequency of 30 Hz and a value of ± 4 V. However, the present invention is not limited to this, and may be any frequency at which the liquid crystal operates. Of course, if the amplitude of the AC voltage A is increased, the transition time will be faster. At this time, the higher the bias voltage B is, the faster it is. However, in consideration of lowering the drive voltage, it is desirable to set the bias voltage to an optimum voltage level according to the desired transition time. Moreover, although the rectangular wave was used as a waveform, you may use the alternating current waveform from which duty ratio differs.

  (Reference form 2)

  FIG. 6 is a conceptual diagram of a pixel unit of the liquid crystal display device according to the second embodiment. In the second embodiment, a step of applying an alternating voltage with a bias voltage superimposed between the substrates and a step of electrically opening the substrates between the substrates are alternately repeated to open the liquid crystal layer. It is characterized in that the orientation is changed to the bend orientation.

  In the liquid crystal display device according to the second embodiment, the same components as those of the liquid crystal display device according to the first embodiment are denoted by the same reference numerals and the description thereof is omitted. In the second embodiment, the alignment transition drive circuit 40, the switch circuit 42a, and the switch control circuit 43 are used in place of the alignment transition drive circuit 30, the switch circuit 32a, and the switch control circuit 32 of the first embodiment. The switch circuit 42a is a three-terminal changeover switch circuit including an individual contact P5 in addition to the individual contacts P1 and P2. The switching of the switch circuit 42a is controlled by a switch control circuit 43. The alignment transition driving circuit 40 applies the driving voltage shown in FIG. This drive voltage is an AC voltage in which an AC rectangular wave voltage C is superimposed on a bias voltage D as shown in FIG. 7, and the value of the drive voltage is necessary to cause a transition from the splay alignment to the bend alignment. It is set to a voltage value larger than the critical voltage, which is a minimum voltage.

  The common contact Q1 of the switch circuit 42a is connected to any one of the individual contacts P1, P2, and P5 by a switch switching signal S3 from the switch control circuit 42. In a state in which the common contact Q1 is connected to the individual contact P5, the electrodes 22 and 23 are in an open state separated from the alignment transition drive circuit 40. In a state where the common contact Q1 is connected to the individual contact P1 and the common contact Q2 is connected to the individual contact P3, the drive voltage from the alignment transition drive circuit 40 is applied to the electrodes 22 and 23. In the state where the common contact Q1 is connected to the individual contact P2 and the common contact Q2 is connected to the individual contact P4, the drive voltage from the liquid crystal display drive circuit 31 is applied to the electrodes 22 and 23.

  Next, a driving method according to the second embodiment will be described.

  First, prior to liquid crystal display driving based on the original image signal, initialization processing is performed for transition to bend alignment. First, when the power is turned on, the switch control circuit 43 outputs a switch switching signal S3 to the switch circuit 42a and also outputs a switch switching signal S2 to the switch circuit 32b, thereby connecting the common contact Q1 and the individual contact P1. In addition, the common contact Q2 and the individual contact P3 are connected. As a result, the drive voltage shown in FIG. 7 is applied between the electrodes 22 and 23 from the alignment transition drive circuit 30. Then, when a certain period T2 has elapsed, the switch control circuit 43 outputs a switch switching signal S3 to the switch circuit 42a, and puts the common contact Q1 and the individual contact P5 into a connected state. As a result, the electrodes 22 and 23 are disconnected from the alignment transition drive circuit 40 and are in an open state. Such an open state is maintained for the period W2, and during this open state period W2, the electrodes 22 and 23 are in a charge holding state.

  When the open state period W2 elapses, the switch control circuit 43 outputs a switch switching signal S3 to the switch circuit 42a, and sets the common contact Q1 and the individual contact P1 in the connected state again. Then, such an alignment transition drive and an open state are alternately repeated, and when a certain period of time elapses after the power is turned on, the entire surface of the electrode is completely transitioned to bend alignment.

  When the fixed period has elapsed, the switch control circuit 43 outputs the switch switching signal S3 to the switch circuit 42a and also outputs the switch switching signal S2 to the switch circuit 32b, so that the common contact Q1 and the individual contact P2 are connected. And the common contact Q2 and the individual contact P43 are connected. As a result, the drive signal voltage from the liquid crystal display drive circuit 31 is applied between the electrodes 20 and 21, and a desired image is displayed. Here, the liquid crystal display drive circuit 31 maintains the bend alignment state by setting the rectangular wave voltage of 2.7 V to 30 Hz as in the first embodiment, and turns it off, and turns on the rectangular wave voltage 7 V of 30 Hz. As shown, the OCB panel is displayed.

  Next, the present inventor manufactured a liquid crystal display device having the above-described configuration and conducted an initialization process experiment with the above driving method. The experimental conditions are as follows.

  The electrode area was 2 cm 2, the cell gap was about 6 μm, the bias voltage B was 2 V, the frequency and amplitude of the AC rectangular wave voltage D were 30 Hz and ± 4 V, and the application time T2 was fixed at 2 seconds.

  Under the above conditions, the open state time W2 was changed to 0 seconds, 0.2 seconds, 2 seconds and 3 seconds, and the transition time when the voltage application state and the open state were alternately repeated was measured. The result is shown in FIG. Here, the transition time means the time required to complete the alignment transition in the entire area of the electrode area.

  As is clear from FIG. 8, when the open state time W2 was 0 seconds, that is, when an alternating voltage superimposed with a bias voltage was continuously applied, the transition time required 80 seconds. On the other hand, when the open state time W2 was set to 0.2 seconds and the AC voltage superimposed with the bias was alternately switched, the transition time was shortened to 40 seconds. However, when the open state time W2 is 2 seconds, the transition time is as long as 420 seconds, and when W2 is 3 seconds, the transition cannot be completed.

  Further, when the transition time was measured under the same conditions as in the above experimental example except that the application time T2 was 0.3 seconds and the open state period W2 was 0.3 seconds, the transition time was 28 seconds.

  Incidentally, when T2 was fixed to 2 seconds and W2 was set to 0.1 second or more and 0.5 second or less, good results were obtained.

  It can be considered that the state transition time from the splay alignment to the bend alignment became extremely short by repeatedly switching the biased alternating voltage and the open state as described above for the following reason. That is, by applying an alternating voltage with a bias superimposed, the liquid crystal molecule orientation of the liquid crystal layer is shaken and is displaced between the substrates as shown in FIG. 2D, and then the transition nucleus is formed by switching to the short open state. It is thought that this occurred and the transition time became faster.

  The effect can be obtained even if another voltage signal is further added and then the open state is entered next before or after the step of applying the AC voltage on which the bias is superimposed.

  Further, the voltage value of the bias voltage and the AC voltage, the application time, the open state maintenance time, and the like can be selected according to the desired transition time. The frequency of the AC voltage may be a frequency at which the liquid crystal operates, and may be a value such as 10 kHz. Although a rectangular wave is used as the waveform, alternating waveforms with different duty ratios may be used.

  (Reference form 3)

  FIG. 9 is a conceptual diagram of a pixel unit of the liquid crystal display device according to the third embodiment. In the third embodiment, the step of applying an alternating voltage with a bias voltage superimposed between the substrates and the step of applying a zero voltage or a low voltage between the substrates are alternately repeated, and the liquid crystal layer is bent from the splay alignment. It is characterized by being transferred to orientation.

  In the liquid crystal display device according to the third embodiment, the same components as those of the liquid crystal display device according to the second embodiment are denoted by the same reference numerals and the description thereof is omitted. In the third embodiment, a switch circuit 42b and a switch control circuit 53 are used instead of the switch circuit 32b and the switch control circuit 43 in the second embodiment. In the third embodiment, in addition to the alignment transition drive circuit 40, an alignment transition drive circuit 50 for applying a low voltage between the electrodes 22 and 23 is provided.

  The switch circuit 42b is a three-terminal changeover switch circuit provided with individual contacts P6 in addition to the individual contacts P3 and P4. The switch switching of the switch circuit 42b is controlled by the switch control circuit 53. The common contact Q2 of the switch circuit 42b is connected to any one of the individual contacts P3, P4, and P6 by the switch switching signal S4 from the switch control circuit 53.

  In the state where the common contact Q1 is connected to the individual contact P5 and the common contact Q2 is connected to the individual contact P3, the drive voltage from the alignment transition drive circuit 40 is applied to the electrodes 22 and 23. In the state where the common contact Q1 is connected to the individual contact P5 and the common contact Q2 is connected to the individual contact P6, the drive voltage from the alignment transition drive circuit 50 is applied to the electrodes 22 and 23. . Further, in the state where the common contact Q1 is connected to the individual contact P2 and the common contact Q2 is connected to the individual contact P4, the drive voltage from the liquid crystal display drive circuit 31 is applied to the electrodes 22 and 23.

  Next, a driving method according to the third embodiment will be described.

  First, prior to liquid crystal display driving based on the original image signal, initialization processing is performed for transition to bend alignment. First, when the power is turned on, the switch control circuit 53 outputs a switch switching signal S3 to the switch circuit 42a and also outputs a switch switching signal S4 to the switch circuit 42b, thereby connecting the common contact Q1 and the individual contact P1. In addition, the common contact Q2 and the individual contact P3 are connected. Accordingly, the drive voltage shown in FIG. 10 is applied between the electrodes 22 and 23 from the alignment transition drive circuit 40. When a predetermined period T3 elapses, the switch control circuit 53 outputs the switch switching signal S3 to the switch circuit 42a and also outputs the switch switching signal S4 to the switch circuit 42b, and the common contact Q1 and the individual contact P5 are connected. And the common contact Q2 and the individual contact P6 are connected. Accordingly, the low voltage shown in FIG. 10 is applied between the electrodes 22 and 23 from the alignment transition drive circuit 50. Such low voltage application is maintained for the period W3.

  Next, when the low voltage application period W3 elapses, the switch control circuit 53 outputs the switch switching signal S3 to the switch circuit 42a and also outputs the switch switching signal S4 to the switch circuit 42b, and again connects the common contact Q1 and the individual contact P1. The connection state is set and the common contact Q2 and the individual contact P3 are connected. Then, such an alternating voltage application process and a low voltage application process are alternately repeated, and when a certain period of time elapses after the power is turned on, the entire surface of the electrode completely transitions to bend alignment.

  When this fixed period has elapsed, the switch control circuit 53 outputs the switch switching signal S3 to the switch circuit 42a and also outputs the switch switching signal S4 to the switch circuit 42b, and the common contact Q1 and the individual contact P2 are connected. And the common contact Q2 and the individual contact P43 are connected. As a result, the drive signal voltage from the liquid crystal display drive circuit 31 is applied between the electrodes 20 and 21, and a desired image is displayed. Here, the liquid crystal display drive circuit 31 maintains the bend alignment state by setting the rectangular wave voltage of 2.7 V to 30 Hz as in the first embodiment, and turns it off, and turns on the rectangular wave voltage 7 V of 30 Hz. As shown, the OCB panel is displayed.

  Next, the present inventor manufactured a liquid crystal display device having the above-described configuration and conducted an initialization process experiment with the above driving method. The experimental conditions are as follows.

The electrode area was 2 cm ² , the cell gap was about 6 μm, the bias voltage D was 2 V, the frequency and amplitude of the AC rectangular wave voltage C were 30 Hz and ± 4 V, and the application time T3 was fixed to 1 second. The applied voltage during the low voltage application period W3 was a DC voltage of -2V.

  Under the above conditions, the transition time when the low voltage application period W3 was changed and the alternating voltage application state and the application voltage application state were alternately repeated was measured, and the result is shown in FIG.

  As is clear from FIG. 11, when the low voltage application time was 0 seconds, that is, when an alternating voltage superimposed with a bias voltage was continuously applied, the transition time required about 80 seconds. On the other hand, when the low voltage application time W3 was set to 0.1 second and the AC voltage superimposed with the bias was alternately switched, the transition time was shortened to 60 seconds. However, when the low voltage application time W3 is 1 second, the transition time becomes 360 seconds, and when W3 is 3 seconds, the transition cannot be completed.

  In addition, the transition was completed within 50 seconds at the shortest in repeated switching between the AC voltage ± 4 V with the bias voltage superimposed on 2 V and the DC voltage 0 V. In addition, the transition time within 50 seconds at the shortest was obtained by repeated switching between the AC voltage ± 4 V superimposed with the bias 2 V and the AC low voltage ± 2 V.

  Incidentally, when T3 was fixed to 1 second and W2 was set to 0.1 second or more and 0.5 second or less, good results were obtained.

  As described above, the transition time from the splay alignment to the bend alignment is shortened by repeatedly switching between the bias voltage-applied AC voltage application and the low voltage application, rather than simply applying the AC voltage with the bias superimposed. . This is due to the application of an alternating voltage with bias superimposed, and the liquid crystal molecule orientation of the liquid crystal layer is shaken and is displaced between the substrates as shown in FIG. 2 (d), and then switched to a short low voltage application state. It is thought that transition nuclei were generated and the transition time was faster.

  Further, the voltage value of the bias voltage and the AC voltage, the application time, the low voltage value, the application time, and the like can be selected and changed depending on the desired transition time, not the above values. The frequency of the AC voltage may be a frequency at which the liquid crystal operates, and may be a value such as 10 kHz. Although a rectangular wave is used as the waveform, alternating waveforms with different duty ratios may be used.

  In the above example, a low voltage of −2V is applied during the low voltage application period W3, but 0V may be applied.

  Next, the ratio between the AC voltage application period T3 and the low voltage application period W3 and the number of repetitions of AC voltage application and low voltage application per second will be described. Here, for convenience of explanation, the voltage in the low voltage application period W3 is assumed to be 0V, and alternating repetition of alternating voltage application and 0V application is considered as one transition voltage as indicated by a broken line L in FIG. In such a case, in order to shorten the transition time, it is necessary to set the frequency of the transition voltage L in the range of 0.1 Hz to 100 Hz and the duty ratio of the transition voltage L in the range of 1: 1 to 1000: 1. There is. Further, it is desirable that the frequency of the transition voltage L is in the range of 0.1 Hz to 10 Hz, and the duty ratio of the transition voltage L is in the range of 2: 1 to 1000: 1. The reason will be described in detail below.

  In a duty ratio range (for example, a duty ratio range of 1: 1 to 1:10, etc.) in which the duty ratio of the repetitively applied voltage is larger in the voltage application pause period than in the voltage application period, the transition nucleus is obtained by applying the pulse width. Even if this occurs, it is considered that the transition is relieved in the voltage application pause state at the subsequent pulse interval, and returns to the splay alignment, and the transition is not completed. Therefore, it is necessary to set the duty ratio so that the voltage application period is larger than the voltage application pause period. In order to enlarge the transition region, the duty ratio is in the range of 1: 1 to 1000: 1 where the pulse width is wider than the pulse interval, preferably 2: 1 to 100: 1. When DC is continuously applied from 1000: 1, it is considered that the pulse repetitive application is almost eliminated, so that the opportunity for generation of transition nuclei decreases and the transition becomes slightly longer.

The repetition frequency of the voltage application for transition may be from continuous to about 100 Hz. Desirably, a pulse interval of about 10 ms or more with a duty ratio of 1000: 1 from 10 Hz at which a pulse width of about 100 ms or more is obtained for transition expansion. Up to 0.1 Hz is preferable.

  As is clear from Table 1, when the frequency is in the range of 0.1 Hz to 10 Hz and the duty ratio is in the range of 2: 1 to 1000: 1, the transition time is extremely small, and the frequency is in the range of 0.1 Hz to 100 Hz. Even when the duty ratio is in the range of 1: 1 to 1000: 1, it is recognized that the transition time is sufficiently small.

  (Reference form 4)

  FIG. 12 is a conceptual diagram of a pixel unit of the liquid crystal display device according to the fourth embodiment. In the fourth embodiment, an example in which the present invention is applied to a driving method of an active matrix liquid crystal display device is shown.

  First, the configuration of the liquid crystal display device related to the driving method according to the fourth embodiment will be described with reference to FIG. The liquid crystal display device according to the fourth embodiment has the same configuration as that of an active matrix liquid crystal display device including a general OCB cell with respect to the configuration excluding the drive circuit unit. That is, it has a pair of glass substrates 60 and 61 and a liquid crystal layer 66 sandwiched between the glass substrates 60 and 61. The glass substrates 60 and 61 are arranged to face each other with a certain interval. A common electrode 62 made of an ITO transparent electrode is formed on the inner surface of the glass substrate 60, and a thin film transistor (TFT) 70 as a pixel switching element and a transparent ITO ITO connected to the TFT 70 are formed on the inner surface of the glass substrate 61. A pixel electrode 63 made of an electrode is formed. Alignment films 64 and 65 made of a polyimide film are formed on the common electrode 62 and the pixel electrode 63, and the alignment films 64 and 65 are subjected to an alignment process so that the alignment directions are parallel to each other. A liquid crystal layer 66 made of P-type nematic liquid crystal is inserted between the alignment films 64 and 65. The pretilt angle of the liquid crystal molecules on the alignment films 64 and 65 is set to about 5 degrees, and the critical voltage for transition from the splay alignment to the bend alignment is set to 2.6V. The retardation of the optical compensator 67 is selected so that white or black is displayed in the on state. In the figure, reference numerals 68 and 69 denote polarizing plates.

  In the figure, reference numerals 71 and 72 denote alignment transition drive circuits. The alignment transition drive circuit 71 applies a drive voltage to the common electrode 62 with reference to the center of the common electrode shown in FIG. It works to apply 0V. As another configuration, the alignment transition drive circuit 72 functions to apply 0 V to the common electrode 62 and the pixel electrode 63. Reference numeral 73 denotes a liquid crystal display driving circuit. The liquid crystal display driving circuit 73 serves to apply a driving voltage having a voltage waveform shown in FIG. 13 to the common electrode 62 and the pixel electrode 63. That is, the liquid crystal display driving circuit 73 applies the voltage indicated by the reference symbol M1 in FIG. 13 to the pixel electrode 63, and applies the voltage indicated by the reference symbol M2 in FIG. In the above configuration, 0 V is applied to the pixel electrode 63 during the alignment transition period, but instead, the pixel electrode voltage is applied from the liquid crystal display driving circuit 73 during the alignment transition period. It may be.

  Reference numerals 74a and 74b denote switch circuits, and reference numeral 75 denotes a switch control circuit that controls switching of the switching mode of the switch circuits 74a and 74b. The switch circuit 74a includes three individual contacts P7, P8, P9 and one common contact Q1, and the switch circuit 74b includes three individual contacts P10, 11, 12 and one common contact Q2. It has. In a state where the common contact Q1 is connected to the individual contact P7 and the common contact Q2 is connected to the individual contact P10, the drive voltage from the alignment transition drive circuit 71 is applied to the electrodes 62 and 63. In the state where the common contact Q1 is connected to the individual contact P2 and the common contact Q2 is connected to the individual contact P4, the drive voltage from the liquid crystal display drive circuit 73 is applied to the electrodes 62 and 63.

  Next, a driving method according to the fourth embodiment will be described.

  First, prior to liquid crystal display driving based on the original image signal, initialization processing is performed for transition to bend alignment. First, when the power is turned on, the switch control circuit 75 outputs a switch switching signal to the switch circuit 74a and also outputs a switch switching signal to the switch circuit 74b, thereby connecting the common contact Q1 and the individual contact P7, and The contact Q2 and the individual contact P10 are connected. Thereby, the drive voltage shown in FIG. 14 is applied to the common electrode 62 from the alignment transition drive circuit 71. In other words, an alternating voltage synchronized with the vertical synchronizing signal on which the bias voltage −GV is superimposed is applied to the common electrode 62 with the common electrode center as a reference. Note that 0 V is applied to the pixel electrode. The application of the AC voltage is maintained for a period T4.

  Next, when the AC voltage application period T4 elapses, the switch control circuit 75 outputs a switch switching signal to the switch circuit 74a and also outputs a switch switching signal to the switch circuit 74b to connect the common contact Q1 and the individual contact P9. And the common contact Q2 and the individual contact P12 are connected. As a result, 0 V is applied from the alignment transition drive circuit 72 to the common electrode 62 and the pixel electrode 63 as shown in FIG. Then, this 0V voltage application is maintained for a period W4.

  Next, when the 0 V voltage application period W4 elapses, the switch control circuit 75 outputs a switch switching signal to the switch circuit 742a and outputs a switch switching signal to the switch circuit 74b, and again connects the common contact Q1 and the individual contact P7. And the common contact Q2 and the individual contact P10 are connected. Then, the AC voltage application process and the 0V voltage application process are alternately repeated, and after a certain period of time has elapsed since the power was turned on, the entire surface of the electrode completely transitions to bend alignment.

  Then, when this fixed period has elapsed, the switch control circuit 75 outputs a switch switching signal to the switch circuit 74a and also outputs a switch switching signal to the switch circuit 74b so that the common contact Q1 and the individual contact P8 are connected, In addition, the common contact Q2 and the individual contact P11 are connected. As a result, the drive signal voltage from the liquid crystal display drive circuit 73 is applied to the electrodes 62 and 63, and a desired image is displayed. Here, the liquid crystal display driving circuit 73 sets the driving voltage 2.7V for maintaining the bend alignment state between both electrodes to the lowest value to turn it off, and sets the upper limit voltage to 7V to turn it on, Display the panel.

  By the above driving method, the OCB active matrix type liquid crystal display device of the bend alignment type with a wide field of view and high-speed response was able to display a high quality drive without any alignment defects.

  Next, the present inventor manufactured a liquid crystal display device having the above-described configuration and conducted an initialization process experiment with the above driving method. The experimental conditions are as follows.

  The cell gap was about 6 μm, the bias voltage G was −6 V, the frequency and amplitude of the AC rectangular wave voltage were 7.92 kHz, ± 10 V, and the application time T3 was 0.5 seconds. The 0V voltage application period W4 was set to 0.5 seconds.

  According to the experimental result, the alignment transition in all the pixels of the panel of the liquid crystal display device could be completed within about 2 seconds.

  When the bias voltage is not superimposed, it takes about 20 seconds to shift the alignment state of the entire display surface. Therefore, it is recognized that in the fourth embodiment as well, driving with the bias voltage superimposed can achieve a reduction in transition time.

  (Reference form 5)

  As a driving method related to the orientation transition of the OCB mode active matrix liquid crystal display device, the driving voltage waveform shown in FIG. 14 may be used instead of the driving voltage waveform shown in FIG. That is, in the AC voltage application period T4, a DC voltage of −15 V is applied to the common electrode 62 with respect to the center of the common electrode for 0.5 seconds. Next, in the 0V voltage application period W4, 0V is applied for 0.2 seconds. And DC voltage -15V application and 0V voltage application are repeated alternately. Even in such a driving method, the transfer can be completed reliably and in a very short time.

  In addition, when this inventor experimented using the said drive method, the transition time within 2 second was obtained.

  (Reference form 6)

  In the sixth embodiment, instead of the active matrix type liquid crystal display device used in the fourth and fifth embodiments, a flattening film is arranged on a switching element and a pixel electrode is formed thereon. The driving method of Reference Embodiments 4 and 5 is applied to the liquid crystal display device having the above configuration. The driving method will be described in detail. The bias-superposed alignment transition voltage in Reference Embodiment 4 was applied for 0.5 seconds, and then the open state was set to 0.5 seconds, which was alternately repeated. According to this driving method, the transition time was within 1 second, and the transition could be performed more smoothly. This is thought to be due to the smooth transition from the splay alignment to the bend alignment as a result of being able to reduce the pixel electrode spacing due to the planarization film configuration.

  (Other matters)

  (1) In the above-described reference embodiment, an AC voltage on which a bias voltage is superimposed is applied. However, a DC voltage may be applied. In this case, a unipolar voltage may be used. It can be simplified.

  (2) In the above reference embodiment, the AC voltage signal on which the bias voltage is superimposed is described as the DC bias voltage. However, a low frequency AC signal may be used to improve reliability.

  (3) The optimum range of the frequency and duty ratio of the repetitive voltage can be applied to other reference forms other than the reference form 3.

  (4) In the above reference embodiment, the driving method of the liquid crystal display device of the invention has been described for the transmissive liquid crystal display device, but a reflective liquid crystal display device may be used. These may be a full-color liquid crystal display device using a color filter or a color filter-less liquid crystal display device.

  (Reference form 7)

  FIG. 16 is a schematic sectional view of a liquid crystal display device according to Reference Embodiment 7 of the present invention, and FIG. 17 is a schematic plan view thereof. The liquid crystal display device shown in FIG. 16 includes polarizing plates 101 and 102, a phase compensation plate 103 for optical compensation disposed inside the polarizing plate 101, and an active matrix disposed between the polarizing plates 101 and 102. Type liquid crystal cell 104. The liquid crystal cell 104 includes an array substrate 106 made of glass or the like, and a counter substrate 105 facing the array substrate 106. A pixel electrode 108, which is a transparent electrode, is formed on the inner surface of the array substrate 106. A common electrode 107 is formed on the inner surface of the counter substrate 105. Further, an alignment film 110 is formed on the pixel electrode 108, and an alignment film 109 is formed on the common electrode 107.

  A switching element 111 made of, for example, an a-Si TFT element is disposed on the array substrate 106, and the switching element 111 is connected to the pixel electrode 108.

  Further, between the alignment films 109 and 110, a spacer (not shown) having a diameter of 5 microns and a liquid crystal layer 112 made of a nematic liquid crystal material having a positive dielectric anisotropy are disposed. The alignment films 109 and 110 are subjected to parallel alignment treatment in the same direction so that the pretilt angles of the liquid crystal molecules on the surfaces thereof have positive and negative values and are substantially parallel to each other. Therefore, the liquid crystal layer 112 forms a so-called splay alignment composed of alignment regions in which liquid crystal molecules spread obliquely when no voltage is applied.

  The alignment film 110 includes an alignment film 110a having a large pretilt angle B2 (third pretilt angle) and an alignment film 110b having a small pretilt angle A2 (first pretilt angle). The alignment film 109 includes an alignment film 109a having a small pretilt angle D2 (fourth pretilt angle) and an alignment film 109b having a large pretilt angle C2 (second pretilt angle). The pretilt angle C2 is disposed opposite to the pretilt angle B2, and the pretilt angle D2 is disposed opposite the pretilt angle B2.

  Further, the alignment films 109 and 110 are subjected to parallel alignment processing in the same direction as the signal electrode lines 113 by rubbing cross in the same direction of the upper and lower substrates (from the left side to the right side in FIG. 16).

  Although not shown, the liquid crystal display device is provided with an alignment transition driving circuit including a first voltage applying unit and a second voltage applying unit in addition to the liquid crystal display driving circuit. Then, a first voltage is applied between the pixel electrode 108 and the common electrode 107 by the first voltage applying means, and a discretion is made in the vicinity of the boundary between the first liquid crystal cell region and the second liquid crystal cell region. Forming a transition line in the disclination line by forming a nation line and applying a second voltage higher than the first voltage between the pixel electrode 108 and the counter electrode 107 by the second voltage applying means. The splay alignment is changed to the bend alignment.

  Next, a method for manufacturing the liquid crystal display device will be described.

  First, the signal scanning line 113, the switching element 111 and the pixel electrode 108 were formed on the inner surface of the array substrate 106.

  Next, a polyimide alignment film material having a pretilt angle B2 as a third pretilt angle having a large value of about 5 degrees of a polyamic acid type manufactured by Nissan Chemical Industries, Ltd. is applied on the pixel electrode 108, After drying, firing was performed to form an alignment film 110 a on the pixel electrode 108.

  Next, the alignment film 110b was formed by irradiating the left side region on the paper surface of the alignment film 110a with ultraviolet rays to change the pretilt angle A2 as the first pretilt angle to a small value of about 2 degrees.

  A common electrode 107 was formed on the inner surface of the counter substrate 105.

  Next, on the common electrode 107, a polyimide alignment that imparts to the interface liquid crystal molecules a pretilt angle C2 as a second pretilt angle having a large value of about 5 degrees of a polyamic acid type manufactured by Nissan Chemical Industries, Ltd. A film material was applied, dried, and baked to form an alignment film 109 b on the common electrode 107.

  Next, the right side of the alignment film 109b on the right side of the paper (region facing the pretilt angle B2 having a large pretilt angle) is irradiated with ultraviolet rays to obtain a pretilt angle D2 of about 2 degrees as a fourth pretilt angle. Thus, the orientation film 109a was formed.

  As described above, a large pretilt angle C2 (second pretilt angle) is arranged opposite to a small pretilt angle A2 (first pretilt angle) as shown in FIG. A small pre-tilt angle D2 (fourth pre-tilt angle) could be arranged opposite to (third pre-tilt angle).

  In addition, the pretilt angle can be controlled as follows.

  That is, as shown in FIG. 18A, an active matrix type switching element (not shown) made of an a-Si TFT element and the like and a pixel electrode 108 are formed on the array substrate 106 and connected thereto. .

  Next, as shown in FIG. 18B, the left side region of the pixel electrode 108 is irradiated with ultraviolet rays in an ozone atmosphere to flatten it compared to the right side region of the pixel electrode 108 to form a flattened region 108a. did.

  Next, as shown in FIG. 18C, an alignment film 110 was formed by applying and drying or baking a premide type polyimide alignment material manufactured by JSR on the pixel electrode 108.

  When formed in this manner, the pretilt angle of the liquid crystal molecules 140 positioned on the planarized region 108a of the pixel electrode 108 is set to a value smaller than the pretilt angle of the liquid crystal molecules 140 positioned on the non-planarized region 108b. it can. Further, by performing the same process on the common electrode, a liquid crystal display device having the first liquid crystal cell region and the second liquid crystal cell region in the same pixel can be obtained as in FIG. .

  Next, as shown in FIG. 16, the surfaces of the alignment film 109 and the alignment film 110 that are formed as described above and that give a pretilt angle of the same size are rubbed with the upper and lower substrates in the direction perpendicular to the signal electrode line 113. A liquid crystal layer 112 made of a positive nematic liquid crystal material was disposed by parallel alignment in the direction (from left to right in FIG. 16).

  In the liquid crystal display device thus produced, a small pretilt angle A2 is arranged at the orientation source (upstream side in the rubbing processing direction) of the pixel electrode 108, and a large pretilt angle C2 is arranged on the opposite side. Then, when 2.5 V is applied as a first voltage between the common electrode 107 and the pixel electrode 108 to the (a) region (first liquid crystal cell region) of the pixel in FIG. The b-spray alignment 120 with the splay alignment on the side and the t-spray alignment 121 with the liquid crystal molecules splayed on the counter substrate 105 side are easily formed in the (b) region (second liquid crystal cell region) of the pixel. Become.

  That is, as shown in FIGS. 16 and 17, when 2.5 V as the first voltage is applied between the common electrode 107 and the pixel electrode 108 through the switching element 111 of the liquid crystal cell 104, the b-spray orientation is formed in the pixel. A region (first liquid crystal cell region) and a t-spray alignment region (second liquid crystal cell region) are formed, and a disclination line 123 is formed along the signal electrode line 113 and a gate electrode line 114. 114 'was clearly formed (disclination line forming step).

  Further, by repeatedly applying a voltage −15 V pulse as the second voltage between the common electrode 107 and the pixel electrode 108, a transition nucleus is generated from the disclination line 123 as shown in FIG. The transition to the bend alignment 124 was expanded, and the entire TFT panel pixel was quickly transitioned in about 3 seconds (alignment transition step).

  This is because the discnation line region that is the boundary between the b-spray alignment state and the t-spray alignment region has higher strain energy than the surroundings, and a high voltage is applied between the upper and lower electrodes in this state. It is considered that energy was further applied and the splay alignment was changed to the bend alignment.

  (Reference form 8)

  FIG. 19 is a schematic view of a liquid crystal display device according to Reference Embodiment 8 of the present invention.

  At the time of normal display, the gate electrode lines are turned on and scanned in sequence, but before normal display, the gate electrode lines are sequentially turned on and a second voltage is applied between the common electrode 107 and the pixel electrode. As a result, by repeatedly applying the voltage −15V pulse, a horizontal electric field caused by the potential difference is generated between the pixel electrode 108 and the gate electrode lines 114 and 114 ′. Then, due to the lateral electric field, as shown in FIG. 19, transition nuclei are generated from the vicinity of the disclination line 123 and the gate electrode lines 114 and 114 ′, and the transition is expanded to bend alignment, and the entire TFT panel pixel is further accelerated in about 1 second. Expanded transition to crab bend alignment (alignment transition process).

  This is because the disclination line region, which is the boundary between the b-spray alignment state and the t-spray alignment region, has higher strain energy than the surroundings, and in this state also from the gate electrode line arranged horizontally It is considered that energy was given further by applying a lateral electric field to the disclination line, and the energy was transferred quickly. After the transfer is completed, the gate electrode lines 114 and 114 'return to the normal scanning state.

  The second voltage applied between the pixel electrode and the common electrode may be applied continuously. Further, when a pulsed voltage is repeatedly applied, the frequency is in the range of 0.1 Hz to 100 Hz, and the duty ratio of the second voltage is at least 1: 1 to 1000: 1. Is obtained.

  (Other matters)

  In Reference Embodiments 7 and 8, the pretilt angle D2 of the alignment destination region of the common electrode is set to a small value, but may be a large value. Further, although the pretilt angle B2 of the alignment destination region of the pixel electrode is set to a large value, the effect is obtained even with a small value because the t-spray alignment is caused by the influence of the lateral electric field.

  Further, although the opposing pretilt angle C2 is set to 5 degrees with respect to the pretilt angle A2 of one substrate side, if the ratio is large, the transition time can be shortened and the transition time can be further increased.

  In the above description, the value of the smaller pretilt angle A2 is set to 2 degrees. However, in order to make b-spray alignment and easy transition to bend alignment, the values of the small pretilt angles A2 and D2 are 3 degrees or less. The pretilt angles B2 and C2 having large values may be 4 degrees or more.

  In addition, the alignment processing direction is the direction perpendicular to the signal electrode line 113 and parallel alignment processing in the same direction of the upper and lower substrates, but the direction perpendicular to the gate electrode line 114 (that is, the direction perpendicular to the paper surface in FIG. 16). Alternatively, parallel alignment treatment may be performed in the same direction on the upper and lower substrates. At that time, the formation place of the disclination line is different.

  In addition, when the alignment process is performed with the parallel alignment process shifted by, for example, about 2 degrees from the perpendicular direction of the electrode line along the pixel electrode, a lateral electric field is obliquely applied from the electrode to the disclination line formed in the pixel. Therefore, a twisting force is applied to the splay-aligned liquid crystal molecules and the transition to bend alignment is facilitated, so that a liquid crystal display device in which the transition is surely fast can be obtained.

  Note that the first voltage may be equal to or higher than a voltage at which a disclination line can be formed. In addition, although the second voltage is applied between the pixel electrode and the common electrode, it may be applied to the common electrode.

  Further, although a polyimide material is used as the alignment film material, other materials such as a monomolecular film material may be used.

  In other liquid crystal display devices, for example, the substrate can be formed from a plastic substrate. Further, one of the substrates may be formed from a reflective substrate, for example, silicon.

  (Embodiment 1)

  In this embodiment, concaves and convexes having shapes to be fitted to the signal electrode line and the pixel electrode, and the gate electrode line and the pixel electrode, respectively, are formed.

  20 and 21 conceptually show the main part of the liquid crystal display device of this embodiment.

  This figure shows a pixel of an active matrix type OCB mode liquid crystal display device as viewed from above the display surface (user side).

  In FIG. 20, 206 is a signal electrode line (bus line), 207 is a gate electrode line, and 208 is a switching transistor (element).

  In the figure, the signal electrode line 206 and the gate electrode line 207 intersect, but it goes without saying that both electrode lines are three-dimensionally arranged via an insulating film (not shown).

  In addition, the switching transistor 208 made of TFT is connected to a pixel electrode 202a having a substantially square shape in the drawing. The functions, operations, and actions of the signal electrode line 206, the gate electrode line 207, the switching transistor 208, and the pixel electrode 202a are not different from those of the conventional liquid crystal display device as well as the OBC mode.

  In addition, the alignment treatment using the rubbing cloth or the like is performed on the upper and lower alignment films 203a and 203b in order to first splay align the liquid crystal molecules 211.

  Further, together with the action of the polarizing plates 204a, 204b, etc., light and dark display is achieved by the action of transferring the entire liquid crystal molecules in the pixel from the splay alignment state in the pixel to the bend alignment region in which the liquid crystal molecules are bent between the opposing substrates. It is the same that is done.

  However, as shown in FIG. 20A, a concave portion 221a and a convex portion 222a are formed at substantially the center of each side of the substantially square pixel electrode 202a. On the other hand, the signal electrode line 206 and the gate electrode line 207 which are wired in the vicinity of the wiring line are deformed into convex portions 261 and 271 and concave portions 262 and 272 so as to be fitted into the concave portions 221a and the convex portions 222a. Has been. For this reason, it is different from a conventional liquid crystal display device in that a deformed lateral excitation application unit for transition excitation is formed above and below the pixel electrode 202a and on the left and right positions (on the paper surface in FIG. 20A). .

  Next, a method for manufacturing the liquid crystal display device will be described.

  A polyimide alignment film material having a pretilt angle of about 5 degrees of polyamic acid type manufactured by Nissan Chemical Industries, Ltd. is applied and dried on the surface of the pixel electrode 202a including the lateral electric field applying portion and the surface of the common electrode 202b. Baking was performed to form alignment films 203a and 203b on the liquid crystal layer 210 side of the respective electrode surfaces.

  Next, both the surfaces of the alignment films 203a and 203b were subjected to an alignment process in a direction substantially orthogonal to the signal electrode lines 206 as shown in FIG.

  Under the above conditions, a liquid crystal layer 210 was formed by vacuum injection of a positive nematic liquid crystal material between the upper and lower substrates.

  For this reason, although not shown, the liquid crystal molecules 211 are aligned on the surfaces of the upper and lower alignment films 203a and 203b so that the pretilt angles have positive and negative values and the perpendicular directions of the molecules are substantially parallel to each other. The liquid crystal layer 210 has a so-called splay alignment in which liquid crystal molecules spread obliquely in a so-called no-voltage application state.

  Next, an operation for display of the liquid crystal display device will be described.

  Based on the above, in the liquid crystal field of −15 V between the common electrode 202b and the pixel electrode 202a, a pulse voltage having a relatively high voltage is repeatedly applied, and the gate electrode line 207 is in a normal scanning state or almost all. Turn it on. Thereby, a lateral electric field stronger than the surrounding normal lateral electric field is applied between the gate electrode line 207, the signal electrode line 206, and the pixel electrode 202a by the lateral electric field applying unit. As a result, in the splay alignment region in the pixel region, when rubbing in a direction substantially orthogonal to the signal electrode line 206, the liquid crystal layer 299 mainly based on the lateral electric field application portion between the gate electrode line 207 and the pixel electrode 202a is formed. Transition nuclei to bend alignment are generated. In addition, as shown in FIG. 21, when rubbing in a direction orthogonal to the gate electrode line 207, the liquid crystal layer 298 mainly having a lateral electric field application portion between the signal electrode line 206 and the pixel electrode 202a has a bend alignment. A transition nucleus is generated.

  Further, the bend alignment region was expanded based on the transition nucleus, and as a result, the entire pixel region could be completed to bend alignment in about 0.5 seconds.

  The entire TFT panel was quickly transferred in about 2 seconds.

  In this mechanism, a high voltage is applied between the upper and lower electrodes, and as shown in FIG. 20 (b), the liquid crystal layer 210 is in a b-splay alignment state, and the strain energy is higher than the surroundings. Since the lateral electric field is applied at a substantially right angle (vertical direction in FIG. 20B) in the orientation state direction, the force for twisting the liquid crystal molecules on the lower substrate side in the b-spray orientation of FIG. It is thought that the generation of transition nuclei occurs.

  In the above description, the horizontal electric field applying portion is formed so that the pixel electrode portion deformed into the concave and convex portions and the concavo-convex portions of both signal electrode lines are fitted to each other, as shown in FIG. Of course, only the pixel electrode 202a, only the signal electrode line 206, and only the gate electrode line 207 may be formed.

  That is, in this figure, the convex portion 263 of the signal electrode line 206, the convex portion 273 of the gate electrode line 207, and the convex portions 223a and 224a of the pixel electrode 202a are only in one of them, and are not of a fitting type. Is different from that shown in FIG.

  Of course, the planar shape of the concavo-convex portion may be a shape other than the triangular shape or the quadrangular shape shown in FIGS. 20 to 22, for example, a trapezoidal shape, a semicircular shape, a circular shape, an elliptical shape, or the like.

  Furthermore, in FIG. 20 to FIG. 22, a total of four horizontal electric field application units are provided on the top, bottom, left and right of one pixel. However, depending on the size of the pixel, only the top and bottom two or only one may be provided. Of course, irregularities may be formed continuously along the electrode edge. Further, until now, the rubbing direction is almost orthogonal to the signal electrode line or the gate electrode line, but the rubbing direction may be an oblique direction. In this case, transition from the liquid crystal layer of the lateral electric field application portion between the signal and gate electrode line and the pixel electrode to bend alignment occurs. In addition, it is desirable that at least one lateral electric field applying unit that can apply a lateral electric field in a direction substantially orthogonal to the rubbing direction is arranged for each pixel.

  20 to 22 are plan views, both electrode lines (the signal electrode line 206 and the gate electrode line 207) and the pixel electrode 202a appear to be on the same plane. This is because at least one of the electrode lines is The pixel electrode and the array substrate may be arranged at different heights.

  As described above, the lateral electric field applying unit composed of the electrode deformed portion in which a part of the periphery of the pixel electrode is deformed into a concavo-convex shape in a plane parallel to the substrate surface is separated by about 0.5 to 10 μm in plan view. A lateral electric field is generated by the presence of a convex portion of the signal electrode line or gate electrode line present on the side of the application portion or a concave portion recessed by about 0.5 to 10 μm.

  (Embodiment 2)

  In the present embodiment, an electrode wire for applying a lateral electric field is provided.

  Hereinafter, the present embodiment will be described with reference to FIG.

  (A) of this figure is the top view seen from the board | substrate upper surface. FIG. 6B is a cross-sectional view taken along a plane parallel to the gate electrode line 207 of the liquid crystal display device.

  In (a) and (b) of this figure, reference numeral 209 denotes an electric wire provided exclusively for applying a lateral electric field in a portion almost directly below the signal electrode line 206 on the array substrate 201a. A transparent insulating film 212 insulates the horizontal electric field applying line 209 from the signal electrode line 206, the gate electrode line 207, and the like. Therefore, when this pixel is viewed from above (in the direction of the user side orthogonal to the display surface), as shown in FIG. 23A, the horizontal electric field application line 209 is viewed in plan view at the left and right central portions of the pixel. A convex portion 291 having a shape protrudes to the side of the signal electrode line 206. The signal electrode line 206 and the pixel electrode 202a are not different from those of the prior art.

  The horizontal electric field applying line 209 is connected to a driving circuit to which the signal electrode line 206 or the gate electrode line 207 is connected. Further, the horizontal electric field applying line 209 is used for normal liquid crystal display after orientation transition. It is configured to be disconnected from the drive circuit.

  Further, the horizontal electric field applying line 209 is an upper signal electrode line with respect to the signal electrode line 206, and is provided close to the pixel electrode through the transparent insulating film to increase the effect of applying the horizontal electric field, and at the same time, the transparent insulating film It may be electrically connected through a contact hole (not shown). In this case, since there are two signal electrode lines, there is an effect that the redundancy is increased and the electric resistance is lowered.

  That is, as shown in FIG. 23C, the horizontal electric field applying line 209 a is provided directly above the signal electrode line 206 via the transparent insulating film 213. It is the same that there is a convex portion 291a having a triangular shape in plan view at the center of the pixel.

  FIG. 23D shows another example of this embodiment. As shown in the figure, the horizontal electric field applying line 209b is covered with the flattened transparent insulating film 212b, and further, the signal electrode line 206 is covered with the flattened transparent insulating film 212c under the dedicated line 209b, and the pixel electrode 202a is formed. It is provided on the planarized transparent insulating film 212b. It is the same that there is a triangular protrusion 291b to the center of the pixel.

  In the figure, the convex portion of the dedicated line for applying the horizontal electric field has a triangular shape, but this may be provided with a continuous convex portion on all the portions facing the pixel electrode, or a convex portion protruding upward. Of course, it may have a three-dimensional structure.

  In addition, the dedicated line for applying the horizontal electric field may be provided directly below or directly above the gate electrode line instead of the signal electrode line. Further, it may be provided directly below both electrode lines.

  (Embodiment 3)

  In this embodiment, a defective portion is formed by providing at least one notch in a pixel electrode.

  FIG. 24 conceptually shows the plane and features of the pixel unit of the liquid crystal display device of the present embodiment. As shown in this figure, the pixel electrode 202a made of an ITO film is removed by etching with a width of, for example, several μm to form an electrode defect portion 225 having a crank shape in plan view.

  In addition, on the pixel electrode 202a surface including the electrode defect portion 225 and the common electrode surface (not shown), a polyamic acid type polyimide having a pretilt angle of about 5 degrees manufactured by Nissan Chemical Industries, Ltd. Alignment film materials are applied, dried, and fired to form alignment films (not shown), and the surface of the alignment films is rubbed in a direction perpendicular to the gate electrode lines 207. Therefore, pretilt of liquid crystal molecules is performed. As in the ninth and tenth embodiments, the corners have positive and negative values and are parallel-oriented in the same direction so as to be substantially parallel to each other.

  Therefore, the liquid crystal layer forms a so-called splay alignment liquid crystal cell composed of alignment regions in which liquid crystal molecules spread obliquely in a so-called no-voltage application state.

  However, when a pulse of a voltage of 15 V or -15 V is repeatedly applied between the common electrode and the pixel electrode of the pixel before display, and the gate electrode is in a normal scanning state or almost all turned on. Since the electrode defect portion 225 exists in the pixel unit, as shown in FIG. 24B, an oblique lateral electric field 280 having a strong distortion is generated at the edge of the electrode defect portion 225.

  For this reason, in the splay alignment in the pixel area, transition nuclei to bend alignment are generated in the liquid crystal layer 299 of the electrode defect portion 225, and the bend alignment area is further expanded to make the entire pixel area in about 0.5 seconds. Complete to bend alignment. In addition, the entire TFT panel transitions quickly in about 2 seconds.

  This is because a horizontal electric field is applied to the horizontal electric field applying portion composed of the electrode defect portion 225, and the liquid crystal molecules in the vicinity thereof are aligned in a horizontal state on the substrate surface, so that a so-called b-spray alignment state is obtained. In this state, a high voltage is applied between the upper and lower electrodes, so that further energy is applied. As a result, transition nuclei are generated in the electrode defect portion 225 and the bend alignment region is expanded. It is done.

  In FIG. 24, one electrode defect portion 225 having a crank shape in plan view is formed, but it is needless to say that two or more electrode defect portions 225 may be formed.

  Of course, the shape may be a straight line, a square, a circle, an ellipse, or a triangle.

  Further, the electrode defect portion 225 may be formed on the common electrode side.

  Of course, it may be formed on both the pixel electrode and the common electrode.

  (Embodiment 4)

  In the present embodiment, a lateral electric field is generated, and in conjunction with this, regions having different tilt angles are formed in advance in the pixel plane.

  FIG. 25 conceptually shows the configuration and characteristics of each pixel of the liquid crystal display device of this embodiment. (A) of this figure is a cross-sectional view of a pixel in a direction parallel to the gate electrode line. Although it is the same pixel, the left (A) and the right (B) have different tilt angles. Show the state.

  FIG. 25B is a plan view of the pixel viewed from the upper (user side) direction. The pixel electrode 202a is provided with concave and convex portions 221a and 222a, and further, the signal electrode line 206 and the gate electrode line 207. Are provided with concavo-convex portions 261, 262, 271 and 272 so as to be phase-fitted with the concavo-convex portions 221a and 222a, and the first voltage is the same as in the seventh embodiment. A disclination line 226 is formed at the boundary between (a) and (b) in FIG.

  Hereinafter, a method for manufacturing the liquid crystal display device of the present embodiment will be described.

  Alignment films 203am and 203bm are formed on the opposing substrate inner surfaces of the active matrix type liquid crystal cell, respectively, and the alignment films 203am and 203bm are processed to form a splay alignment in a state where no voltage is applied to the liquid crystal layer 210. That is, the formation of a transverse electric field application section for transfer excitation in the pixel electrode 202a or the gate electrode line 207 or the like wired close to the pixel electrode 202a is the same as in the first embodiment.

  However, the treatment of the alignment film is different. That is, in FIG. 25A, on the surface of the pixel electrode 202a including the lateral electric field applying portion, a polyimide orientation with a pretilt angle B2 having a large value of about 5 degrees of a polyamic acid type manufactured by Nissan Chemical Industries, Ltd. The film material is applied, dried, and baked to form the alignment film 203am.

  Next, only the left side region 203ah of the alignment film 203am, that is, only the direction shown in (a) is irradiated with ultraviolet rays so that the pretilt angle E2 is changed to an alignment film having a small value of about 2 degrees.

  On the other hand, on the counter substrate 201b, a polyimide alignment film material that imparts a pretilt angle F2 of about 5 degrees of a polyamic acid type manufactured by Nissan Chemical Industries, Ltd. to the interface liquid crystal molecules is applied, dried and fired. An alignment film 203bh is formed on the common electrode 202b.

  In this way, as shown in FIG. 25A (a), the left half alignment film 203bh on the counter substrate 201b side is larger than the small pretilt angle E2 of the alignment film 203ah on the left half side of the array substrate 201a. The pretilt angle F2 of the value is arranged, and the small value of the alignment film 203bm of the right half of the counter substrate 201b is opposed to the large pretilt angle B2 of the alignment film 203am of the right half of the array substrate side 201a as shown in (b). A pretilt angle D2 is arranged.

  Further, the surfaces of the alignment films formed in this way giving a large and small pretilt angle are rubbed with a parallel alignment process in the same direction of the upper and lower substrates in a direction substantially perpendicular to the signal electrode 6 as shown in FIG. did. Thereafter, a positive nematic liquid crystal material was filled, and a liquid crystal layer 210 made of the same was disposed.

  Under the above, a small pretilt angle E2 is arranged at the orientation source (the rubbing root direction) of the pixel electrode 202a, and a large pretilt angle F2 is arranged on the side facing the pretilt angle E2, and FIG. The b-splay alignment 227b in which liquid crystal molecules are splay-oriented on the lower substrate side is provided in the area indicated by (a) of the pixel, and the liquid crystal molecules are splay-oriented on the upper substrate side in the area indicated by (b) of the pixel. The t-spray orientation 227t is easily formed.

  Next, when 2.5 V near the transition critical voltage is applied between the opposing electrodes through the switching transistor 208 of the liquid crystal cell, a b-spray alignment region and a t-spray alignment region are formed in the same pixel for the above-described reason. The disclination line 226 is clearly formed along the signal electrode line 206 and across the gate electrode line 207 at the boundary.

  A pulse of −15 V was repeatedly applied between the common electrode and the pixel electrode of this pixel. Then, as shown in FIG. 25 (b), transition nuclei are generated from the disclination line 226 and the liquid crystal layer 299 in the vicinity of the lateral electric field applying portion, and the transition is expanded to the bend alignment region. Transitioned quickly in seconds.

  This is because, in the declination line 226 region, which is the boundary between the b-spray alignment state and the t-spray alignment region, the strain energy is higher than that of the surroundings. Thus, it is considered that twisting occurs in the splay alignment and the transition easily occurs, and a high voltage is applied between the upper and lower electrodes to further apply energy and bend transition.

  As mentioned above, although this invention has been demonstrated based on some embodiment, of course this invention is not limited to these at all. That is, for example, the following may be performed.

  1) The voltage applied between the pixel electrode and the common electrode is continuous or intermittent.

  2) When a high voltage pulse is repeatedly applied, the frequency is in the range of 0.1 Hz to 100 Hz, and the duty ratio of the second voltage is at least in the range of 1: 1 to 1000: 1. Select.

  3) The substrate to be used is made of plastic, and an organic conductive film is adopted as an electrode.

  4) One of the substrates is formed of a reflective substrate, for example, silicon, or a reflective substrate made of a reflective electrode such as aluminum to form a reflective liquid crystal display device.

  5) A means for providing a projection for generating a strong electrode electric field in a direction orthogonal to the substrate surface is also used in combination with the pixel electrode and the common electrode.

  6) Instead of spherical glass or silica that keeps the distance between both substrates constant, means for forming a protrusion for the purpose and providing the protrusion with a function of aligning liquid crystal molecules is also used.

  7) The upper part or the lower part of the protrusion is also used as the strong electrode generating protrusion.

  8) The shape of the pixel electrode is not square but rectangular or triangular.

  9) The pixel is not divided into two regions with different liquid crystal orientations, but three or four.

  10) In order to increase or decrease the pretilt angle, means such as changing the surface state of the transparent electrode with an O2 asher and forming an alignment film on the transparent electrode is employed.

  (Embodiment 5)

  FIG. 26 is a structural external view of a liquid crystal cell used in the liquid crystal display device according to Embodiment 5, and FIGS. 27 and 28 are a part of a manufacturing process for explaining the production of a convex object.

  A PC-based resist material manufactured by JSR Corporation is applied and formed on a glass substrate 308 to form a resist thin film having a thickness of 1 μm. Next, the resist thin film 320 is exposed and irradiated with parallel ultraviolet rays 323 through a photomask 321 provided with a rectangular pattern of openings 322. The resist thin film 320 exposed with the parallel light is developed and rinsed, and pre-baked at 90 ° C. to form a shape 310 having a convex cross section as shown in FIG.

  Next, 2000 A of ITO electrode 7 was formed on the substrate according to a conventional method to obtain a glass substrate 308 with an electrode. Thereafter, an alignment film coating SE-7492 manufactured by Nissan Chemical Industries, Ltd. was applied by spin coating on the glass substrate 301 having the transparent electrode 302 and the glass substrate 308 on which the above-mentioned convex shape was formed. The alignment films 303 and 306 are formed by curing for 1 hour. After that, rubbing treatment was performed in the direction shown in FIG. 29 using a rayon-made rubbing cloth, and spacer 5 made by Sekisui Fine Chemical Co., Ltd. and Structbond 352A (trade name of Mitsui Toatsu Chemical Co., Ltd. seal resin) were used. Thus, a liquid crystal cell 309 (referred to as a liquid crystal cell A) was prepared by bonding the substrates so that the distance between the substrates was 6.5 μm.

  At this time, the rubbing process was performed so that the liquid crystal pretilt angle at the alignment film interface was about 5 degrees.

  Next, a liquid crystal MJ96435 (refractive index anisotropy Δn = 0.138) was injected into the liquid crystal cell A by a vacuum injection method to obtain a test cell A.

  Next, a polarizing plate is bonded to test cell A so that the polarization axis forms an angle of 45 degrees with the rubbing treatment direction of the alignment film and the polarization axis directions are orthogonal to each other, and a 7 V rectangular wave is applied. Then, when the transition from the splay alignment to the bend alignment was observed, the entire electrode region transitioned from the splay alignment to the bend region in about 5 seconds.

  In the region where the convex object 310 is formed, the liquid crystal layer thickness is smaller than that of the surrounding liquid crystal layer region, and the electric field strength is effectively large, and the bend transition surely occurs from this portion. The generated bend orientation quickly spreads to other regions.

  That is, a reliable and fast spray-to-bend transition can be achieved.

  Needless to say, the convex shape may have a trapezoidal shape, a triangular shape, or a semicircular shape as well as a rectangular shape as in this embodiment.

  As a comparative example, a splay alignment liquid crystal cell R was produced by the same process except that a glass substrate with a transparent electrode having no convex portion 310 was used, and a liquid crystal MJ96435 was sealed to obtain a test cell R. When a 7V rectangular wave is applied to the test cell R, the time required for the entire electrode region to transition from the splay alignment to the bend region is 42 seconds, and the effect of the present invention is clear.

  (Embodiment 6)

  FIG. 30 is a structural external view of a liquid crystal cell used in the liquid crystal display device according to Embodiment 6, and FIG. 31 is a plan view thereof. 30 is a cross-sectional view seen from the arrow X1-X1 in FIG. The sixth embodiment is characterized in that the convex object 310 is provided on the transparent electrode 307a formed outside the display pixel region. The production procedure will be described below.

  An alignment film coating SE-7492 manufactured by Nissan Chemical Industries, Ltd. is applied by spin coating on a glass substrate 301 having a transparent electrode 302 and a glass substrate 308 on which convex shapes are formed, and cured at 180 ° C. for 1 hour in a thermostatic bath. Alignment films 303, 306, and 306a are formed. After that, rubbing treatment was performed in the direction shown in FIG. 29 using a rayon-made rubbing cloth, and spacer 5 made by Sekisui Fine Chemical Co., Ltd. and Structbond 352A (trade name of Mitsui Toatsu Chemical Co., Ltd. seal resin) were used. Thus, a liquid crystal cell (referred to as liquid crystal cell B) was prepared by bonding the substrates so that the distance between the substrates was 6.5 μm.

  At this time, the rubbing process was performed so that the liquid crystal pretilt angle at the alignment film interface was about 5 degrees.

  Next, liquid crystal MJ96435 (refractive index anisotropy Δn = 0.138) was injected into liquid crystal cell B by vacuum injection.

  Next, a polarizing plate is bonded to the liquid crystal cell B so that its polarization axis forms an angle of 45 degrees with the rubbing treatment direction of the alignment film, and the polarization axis directions are orthogonal to each other, and a 7 V rectangular wave is applied. Then, when the transition from the splay alignment to the bend alignment was observed, the entire electrode region shifted from the splay alignment to the bend region in about 7 seconds.

  In the present embodiment, a convex portion is provided outside the display pixel area and bend transition nuclei are generated outside the display pixel area. The generated bend orientation is quickly generated from outside the display pixel area into the display pixel area. It was confirmed to spread to.

  Between the display pixel region and the bend nucleus generating electrode region, there is a region to which no electric field is applied (having no electrode part), but the bend orientation develops beyond this region as long as it is a minute region. .

  (Embodiment 7)

  FIG. 32 is a structural external view of a liquid crystal cell used in the liquid crystal display device according to Embodiment 7, and FIGS. 27, 28, and 33 are a part of a manufacturing process for explaining the production of a convex object. .

  A PC-based resist material manufactured by JSR Corporation is applied and formed on a glass substrate 308 to form a resist thin film having a thickness of 1 μm. Next, the resist thin film 320 is exposed and irradiated with parallel ultraviolet rays 323 through a photomask 321 provided with a rectangular pattern of openings 322. The resist thin film 20 exposed with parallel light is developed, rinsed, and pre-baked at 90 ° C. to form a shape 310 having a convex cross section as shown in FIG.

  Next, post-baking is performed at 150 ° C. above the glass transition point of the resist thin film material, and the shoulder of the convex object 310 is gently inclined in the forward direction, so that the cross-sectional shape is formed in a mountain shape as shown in FIG. Manufactured in the process of.

  Next, an ITO electrode having a thickness of 2000 mm was formed on the substrate according to a conventional method to obtain a glass substrate 308 with an electrode. Thereafter, an alignment film coating SE-7492 manufactured by Nissan Chemical Industries, Ltd. was applied by spin coating on the glass substrate 301 having the transparent electrode 302 and the glass substrate 308 on which the above-mentioned convex shape was formed. The alignment films 303 and 306 are formed by curing for 1 hour. After that, rubbing treatment was performed in the direction shown in FIG. 29 using a rayon rubbing cloth, and spacers 305 made by Sekisui Fine Chemical Co., Ltd. and Structbond 352A (trade name of seal resin made by Mitsui Toatsu Chemical Co., Ltd.) were used. Thus, a liquid crystal cell 309 (referred to as a liquid crystal cell C) was prepared by bonding the substrates so that the distance between the substrates was 6.5 μm.

  At this time, the rubbing process was performed so that the liquid crystal pretilt angle at the alignment film interface was about 5 degrees.

  Next, a liquid crystal MJ96435 (refractive index anisotropy Δn = 0.138) was injected into the liquid crystal cell C by a vacuum injection method to obtain a test cell C.

  Next, a polarizing plate is bonded to the test cell C so that its polarization axis forms an angle of 45 degrees with the rubbing treatment direction of the alignment film, and the polarization axis directions are orthogonal to each other, and a 7 V rectangular wave is applied. Then, when the transition from the splay alignment to the bend alignment was observed, the entire electrode region shifted from the splay alignment to the bend region in about 7 seconds.

  In this test cell C, electric field concentration occurs at the triangular tip, and bend alignment occurs from this portion. In addition, at the upper part of the triangular object 60, there are a rubbing portion and a rubbing portion due to the rubbing process, and as a result, regions having opposite signs of the liquid crystal pretilt angle are formed. That is, in the vicinity of the convex portion, the liquid crystal director is horizontal to the substrate surface, which also seems to contribute to the high-speed spray-bend transition.

  In this embodiment, the electric field concentration portion is provided in the pixel region. However, the same effect is recognized even if it is provided outside the pixel region. Further, in this embodiment, the electric field concentration portion is only disposed on one side of the substrate, but it goes without saying that it may be disposed on both sides of the substrate.

  (Embodiment 8)

  FIG. 34 is a structural external view of a liquid crystal cell used in the liquid crystal display device according to Embodiment 8, and FIG. 35 shows an electrode pattern of the glass substrate 302 used in this embodiment.

  An alignment film coating SE-7492 manufactured by Nissan Chemical Industries, Ltd. is applied by spin coating on two glass substrates 301 and 308 having a transparent electrode 302 having an opening 380 and a transparent electrode 307 having no opening. The alignment films 303 and 306 are formed by curing in a bath at 180 ° C. for 1 hour. After that, rubbing treatment was performed in the direction shown in FIG. 29 using a rayon rubbing cloth, and spacers 305 made by Sekisui Fine Chemical Co., Ltd. and Structbond 352A (trade name of seal resin made by Mitsui Toatsu Chemical Co., Ltd.) were used. Thus, a liquid crystal cell 309 (referred to as a liquid crystal cell D) was prepared by bonding the substrates so that the distance between the substrates was 6.5 μm.

  At this time, the rubbing process was performed so that the liquid crystal pretilt angle at the alignment film interface was about 5 degrees.

  Next, a liquid crystal MJ96435 (refractive index anisotropy Δn = 0.138) was injected into the liquid crystal cell D by a vacuum injection method to obtain a test cell D.

  Next, a polarizing plate is bonded so that the polarization axis forms an angle of 45 degrees with the rubbing treatment direction of the alignment film, and the polarization axis directions are orthogonal to each other, and from the splay alignment to the bend alignment while applying a voltage. The transition to was observed.

  When 2 V, 30 Hz, rectangular wave is applied to the glass substrate 8 side electrode and 7 V, 30 Hz, rectangular wave is applied to the glass substrate 1 side electrode, the entire electrode region transitions from the splay alignment to the bend region. The time required for this was 5 seconds, and an extremely fast bend transition was realized.

  In this embodiment, an electric field of 5V (= 7V-2V) is applied to the liquid crystal layer sandwiched between two electrodes, but an effective voltage of 7V (= 7V-0V) is applied to the liquid crystal layer in the electrode opening. Since an electric field is applied, bend alignment occurs from here.

  In this embodiment, the shape of the opening is rectangular, but it is needless to say that other shapes such as a circle and a triangle may be used.

  (Embodiment 9)

  FIG. 36 is a fragmentary cross-sectional view of a liquid crystal cell used in the liquid crystal display device according to Embodiment 9, and FIG. 37 is a partial enlarged view thereof. In this liquid crystal cell, a pixel switching element 380, a signal electrode line 381, and a gate signal line (not shown) are formed on a glass substrate 308, and covers the switching element 380, the signal electrode line 381, and the gate signal line. A planarizing film 382 is formed. A display electrode 307 is formed on the planarization film 382. The display electrode 307 and the switching element 380 are electrically connected via a relay electrode 384 inserted through the contact hole 383 opened in the planarization film 382. It is connected to the. In the relay electrode 384, a portion on the upper opening side of the contact hole 383 is a recess 384a as shown in FIG. Such a recess 384a forms an opening in the display electrode 307, and an electric field can be concentrated in the vicinity of the recess 384a. Therefore, shortening of the transition time can be achieved.

  (Embodiment 10)

  FIG. 38 is a structural external view of the liquid crystal display device according to the tenth embodiment.

  Phase difference plates 312 and 315, negative uniaxial phase difference plates 311 and 314, and positive uniaxial layers made of an optical medium having negative refractive index anisotropy in which main axes are arranged in a hybrid manner in test cell D created in the eighth embodiment The phase difference plate 319 and the polarizing plates 313 and 316 were bonded together in the arrangement shown in FIG. 39 to produce a liquid crystal display device.

  The retardation values of the retardation films 312, 315, 311, 314, and 319 at this time were 26 nm, 26 nm, 350 nm, 350 nm, and 150 nm, respectively, with respect to light having a wavelength of 550 nm.

  FIG. 40 shows voltage-transmittance characteristics in front of the liquid crystal display device at 25 ° C. A 10 V rectangular wave voltage was applied for 10 seconds to confirm the bend orientation, and the measurement was performed while decreasing the voltage. In the present liquid crystal display element, the transition from the bend alignment to the splay alignment occurs at 2.1 V, so that it is necessary to effectively display at a voltage of 2.2 V or more.

  Next, when the viewing angle dependency of the contrast ratio when the white level voltage is 2.2 V and the black level voltage is 7.2 V is measured, the contrast ratio is 10: 1 or more in the range of 126 degrees up and down and 160 degrees left and right. It has been achieved, and it has been confirmed that sufficient wide viewing angle characteristics can be maintained even when a part of the liquid crystal director direction different from the surrounding is provided on the substrate alignment film surface. Further, even in visual observation, neither orientation failure nor display quality failure was observed.

  Moreover, when the response time between 3V-5V was measured, the rise time was 5 milliseconds and the fall time was 6 milliseconds.

  As is clear from the above, the liquid crystal display device of the present invention can achieve a high-speed splay-bend alignment transition without sacrificing the wide viewing angle characteristics and response characteristics of the conventional OCB mode, and its practical use. The value is extremely great.

  (Reference form 9)

  FIG. 41 is a cross-sectional view of a main part of the liquid crystal display device according to the ninth embodiment. A liquid crystal cell operated as a bend alignment type cell is a so-called sandwich cell in which a liquid crystal layer 402 is sealed between two parallel substrates 400 and 401. Usually, a transparent electrode is formed on one substrate, and a pixel electrode including a thin film transistor is formed on the other substrate.

  FIG. 41 (a) is a schematic diagram showing the orientation in the initial state where no electric field is applied. The alignment in the initial state is a state in which the molecular axes of the liquid crystal molecules are aligned substantially in parallel and substantially uniformly while having a slight inclination with respect to the planes of the substrates 400 and 401, that is, homogeneous alignment. Liquid crystal molecules present at the interface with the substrate are inclined in opposite directions in the upper and lower substrates 400 and 401. That is, the alignment angles θ1 and θ2 (that is, the pretilt angle) of the liquid crystal molecules present at the interface with the substrate are adjusted to have different signs. In the following description, the orientation angle and the pretilt angle are angles that represent the inclination of the molecular axes of liquid crystal molecules with respect to a plane parallel to the substrate as positive in the counterclockwise direction with respect to the plane parallel to the substrate.

  When an electric field with a strength exceeding a certain value in a direction perpendicular to the substrate plane is applied to the liquid crystal layer 402 in the state of FIG. 41A, the alignment state of the liquid crystal changes, as shown in FIG. Transition to orientation.

  The orientation shown in FIG. 41B is called bend orientation, and the inclination of the molecular axis of the liquid crystal molecules relative to the substrate plane, that is, the absolute value of the orientation angle is small in the vicinity of the surfaces of both substrates. In, the absolute value of the orientation angle of the liquid crystal molecules is large. In addition, the entire liquid crystal layer has substantially no twisted structure.

  When the transition from the homogeneous alignment to the bend alignment is observed in detail, first, a bend alignment nucleus is generated in a part of the liquid crystal layer 402, and this nucleus engulfs another region having the homogeneous alignment. However, it gradually grows and finally the entire liquid crystal layer becomes bend alignment. In other words, the transition from the liquid crystal layer to the bend alignment requires the generation of nuclei, that is, the transition from the homogeneous alignment to the bend alignment in a minute region.

  Therefore, the inventors analyzed the transition to the bend alignment in a minute region by solving the equation of motion of the liquid crystal molecular alignment unit vector (hereinafter referred to as “director”), and the nucleus was easily generated. We found the conditions to obtain. The method will be described below.

The alignment state of the liquid crystal is described by the director. Director n is a function represented by [Equation 1].

  Here, k11, k22, and k33 are Frank's elastic constants, which respectively represent the splay, twist, and bend elastic constants. Δε represents the difference between the dielectric constant in the molecular axis direction of the liquid crystal and the dielectric constant in the direction orthogonal thereto, that is, dielectric anisotropy. E is an external electric field.

  In [Equation 2], the first term, the second term, and the third term respectively represent elastic energy due to the spread, twist, and bend of the liquid crystal. The fourth term represents the electrical energy due to the electrical interaction between the external electric field and the liquid crystal. The electrical energy is minimized when n is parallel to E if Δε> 0, and is minimized when n is orthogonal to E if Δε <0. Therefore, when an electric field E exceeding a certain intensity is applied, the liquid crystal molecules are oriented so that the molecular long axis is parallel to the electric field direction if Δε> 0, and the molecular length if Δε <0. Oriented so that the axis is orthogonal to the electric field direction.

The total free energy F of the liquid crystal when the initial molecular orientation is deformed by an external electric field can be expressed as a volume integral of f.

  As shown in [Formula 3], the total free energy F is a function (that is, a functional) defined with an unknown function n (x) representing the director as a variable. The alignment state of the liquid crystal that appears under the application of an external electric field is described by n (x) that minimizes the total free energy F under appropriate boundary conditions. That is, if n (x) that minimizes F is determined, the alignment state of the liquid crystal can be predicted. Furthermore, if the director n (x, t) considering the time change that minimizes F under an appropriate boundary condition can be determined, all behaviors of the device such as optical constants can be predicted. it can. This is the principle of typical minimum action in physical terms, and it is a small variable polarization problem with boundary values in mathematical terms.

  Therefore, [Equation 3] is solved in principle. However, for example, in an analytical method using Euler's equation, since a complicated nonlinear equation appears, it is difficult to easily determine the functional form of the director n (x).

Therefore, in order to easily solve [Equation 3], the following method is adopted. First, the integration space is discretized by the same method as the finite element method. That is, the entire integration space is divided into np elements, and [Equation 3] is expressed as the sum of the integrals of each element.

  Here, the following approximation is performed on the director n (x) in the partial integration space ΔV. It is assumed that nx, ny, and nz are functions of x, y, and z as originally shown in [Expression 2], but are constant in ΔV. Further, it is approximated as dnx, j / dx = (nx, j + 1−dnx, j) / Δx. Note that nx, j is nx in the j-th element, and as described above, although ΔV is constant, it is an unknown number. The approximation of n (x) in this partial integration space ΔV is rough, but this can be covered by making the division of the integration space fine, and the approximation can be enhanced.

  According to the above approximation, in [Equation 4], nx, j, ny, j, nz, j are constants in one element, so that the integration itself can be easily calculated. However, even at this stage, the expression representing the total free energy F is still complicated because there are a large number of unknown terms nx, j, ny, j, nz, j that are proportional to the number of divisions and nonlinear terms. However, values such as nx, 0, ny, 0, nz, 0 can be easily given as boundary conditions.

According to the above approximation, the total free energy F is
Is converted into the form. That is, the total free energy F is converted from a functional defined with the unknown function n (x) as a variable into a function of unknowns nx, j, ny, j, nz, j. The unknowns nx, j, ny, j, nz, j are values that minimize the function F in a multidimensional parameter space.
It is represented by Here, θ is the inclination of the liquid crystal molecules with respect to the plane parallel to the substrate, that is, the orientation angle. Also, θ depends only on the distance z of the liquid crystal molecules from the substrate. FIG. 2 is a schematic diagram showing this director.

Substituting [Formula 6] into [Formula 4], dividing it into np elements, and performing discretization, find θj that minimizes F for each element. That is, for each element
Find θj that satisfies the following equation. Here, d is L / np, and L is the distance between the substrates.

However, it is not easy to solve a complex nonlinear equation such as [Equation 7] by np simultaneous equations. Therefore, [Equation 7] is solved by performing the following circuit analogy. Director's equation of motion is
It is represented by Note that η is the viscosity of the liquid crystal. For [Equation 8], the following circuit analogy is performed.

[Equation 8] is
Is converted to As shown in FIG. 3, the circuit corresponding to [Equation 10] is composed of np CR circuits. The second term of [Expression 10] represents the current flowing through the CR circuit. Rj is a resistance for discharge mitigation, and is a voltage control resistor that defines the current (i) flowing through the CR circuit as i = ∂F (Vj) / ∂Vj.

  The current i (= ∂F / ∂Vj) converges to zero at a specific Vj. That is, Vj can be automatically obtained by obtaining a voltage when the current flowing through the CR circuit becomes zero by a circuit simulator.

  Thus, by replacing the director's equation of motion with an equivalent circuit, the nonlinear simultaneous equations expressing the liquid crystal orientation phenomenon are analyzed on the circuit simulator, and the relationship between the external electric field E and the orientation state (orientation angle θj) is shown. Can be sought.

  In the above method, the nonlinear simultaneous equations expressing the orientation phenomenon are replaced with circuits by analogy of electric circuits and analyzed on the circuit simulator. The calculation process for solving is not included. Therefore, simplification and reduction of the program can be realized.

  Furthermore, if the change in the orientation angle θj accompanying the increase in the external electric field E is calculated based on the above method, the critical electric field Ec of the liquid crystal transition can be obtained as the external electric field E when the orientation angle θj changes suddenly. .

FIG. 44 is an example of a calculation result based on the above method, and represents a time change of θj when the external electric field E is increased with time. The results shown in FIG. 4 indicate that the boundary conditions are fixed as θ0 = + 0.1 rad, θnp−1 = −0.1 rad, k11 = 6 × 10 ⁻⁷ dyn, k33 = 12 × 10 ⁻⁷ dyn, Δε = 10 As a result of calculation. As shown in FIG. 4, it can be seen that at the initial stage of electric field application, the orientation angle θj is relatively small, and the orientation state of the liquid crystal is homogeneous orientation. However, after a lapse of a certain time, that is, when the external electric field E exceeds a certain value (E> Ec), the orientation angle θj suddenly changes and a transition occurs. The orientation angle θj after the transition increases from the vicinity of both substrates toward the center of the liquid crystal layer, and it can be seen that the orientation state of the liquid crystal after the transition is bend orientation.

  As the critical electric field Ec is smaller, the alignment state of the liquid crystal can be quickly transferred from the homogeneous alignment to the bend alignment. Therefore, based on the above method, the critical electric field Ec under each condition was calculated by changing various conditions for determining the alignment of the liquid crystal. As a result, it has been found that the critical electric field Ec is particularly affected by the elastic constant (splay elastic constant) of the liquid crystal and the asymmetry of the pretilt angle.

FIG. 45 shows the result of determining the relationship between the splay elastic constant k11 and the critical electric field Ec. FIG. 45 shows the calculation results with the boundary conditions θ0 = + 0.1 rad, θnp−1 = −0.1 rad, k33 = 12 × 10 ⁻⁷ dyn, and Δε = 10. As shown in FIG. 45, the critical electric field Ec increases as the splay elastic constant k11 increases. In particular, in the range of k11> 10 × 10 ⁻⁷ dyn, Ec increases rapidly as k11 increases.

Therefore, in order to realize quick liquid crystal transition, it is effective that the splay elastic constant k11 is less than 10 × 10 ⁻⁷ dyn, preferably 8 × 10 ⁻⁷ dyn or less. The lower limit of the splay elastic constant k11 is not particularly limited, but is preferably 6 × 10 ⁻⁷ dyn or more. This is because it is usually difficult to synthesize or prepare a liquid crystal material of k11 <6 × 10 ⁻⁷ dyn.

  The liquid crystal material having the splay elastic constant k11 as described above is not particularly limited, and examples thereof include pyrimidine liquid crystal, dioxane liquid crystal, and biphenyl liquid crystal.

  The asymmetry of the pretilt angle can be expressed by the difference (Δθ) in absolute value of the pretilt angle between the upper and lower substrates. As described above, since the pretilt angles θ0 and θnp-1 are different from each other, the difference between the absolute values of the pretilt angles (Δθ) can be expressed by Δθ = | θ0 + θnp-1 |.

FIG. 46A shows the result of obtaining the relationship between the absolute value difference (Δθ) of the pretilt angle between the upper and lower substrates and the critical electric field Ec. FIG. 6A shows the calculation results with k11 = 6 × 10 ⁻⁷ dyn, k33 = 12 × 10 ⁻⁷ dyn, and Δε = 10. As shown in FIG. 46A, the critical electric field Ec decreases as the pretilt angle difference Δθ increases. In particular, in the range of Δθ ≧ 0.0002 rad, Ec rapidly decreases as Δθ increases.

  Therefore, in order to realize quick liquid crystal transition, it is effective to set the difference Δθ in the pretilt angle to 0.0002 rad or more, preferably 0.035 rad or more. The upper limit of the difference Δθ in the pretilt angle is not particularly limited, but is usually less than 1.57 rad, preferably 0.785 rad or less.

  Note that the pretilt angles θ0 and θnp-1 are adjusted so that their absolute values are usually greater than 0 rad and less than 1.57 rad, preferably 0.017 rad to 0.785 rad. The adjustment of the pretilt angle can be controlled by forming an appropriate liquid crystal alignment film on the substrate surface by a method such as oblique vapor deposition or Langmuir-Blodget (LB). The liquid crystal alignment film is not particularly limited, and examples thereof include polyimide resin, polyvinyl alcohol, polystyrene resin, polycinnamate resin, chalcone resin, polypeptide resin, and polymer liquid crystal. In addition to selecting the material for the liquid crystal alignment film, by adjusting the inclination of the deposition direction with respect to the substrate surface when using the oblique deposition method, adjusting the conditions such as the substrate pulling rate when using the LB method. Thus, the pretilt angle can be controlled.

  In addition, the critical electric field Ec is affected by the non-uniformity of the electric field in the liquid crystal layer. This is because the distortion of the electric field generated in the liquid crystal layer affects the stability of the alignment state of the liquid crystal molecules. The non-uniformity of the electric field can be expressed by a ratio (E1 / E0) between the main electric field E0 applied to the liquid crystal layer substantially uniformly and the sub-electric field E1 applied nonuniformly. E1 is the maximum value of the applied sub electric field.

FIG. 47 is an example of calculation results obtained by calculating the critical electric field Ec under each condition by changing the value of E1 / E0 variously based on the above method. The results shown in FIG. 7 indicate that the boundary conditions are fixed as θ0 = + 0.26 rad, θnp−1 = −0.25 rad, k11 = 6 × 10 ⁻⁷ dyn, k33 = 12 × 10 ⁻⁷ dyn, Δε = 10 As a result of calculation. As shown in FIG. 47, the greater E1 / E0, that is, the greater the electric field non-uniformity, the greater the critical electric field Ec. Ec becomes infinitely small in the vicinity of E1 / E0 = 1. This is presumably because when the electric field of the liquid crystal layer is distorted, the homogeneous alignment becomes unstable as compared with the case where the electric field is uniform, and as a result, the transition to the bend alignment is rapidly developed.

  Therefore, in order to realize quick liquid crystal transition, it is effective to apply a spatially nonuniform electric field E1 to the liquid crystal layer together with a substantially uniform main electric field E0. In particular, it is effective to satisfy 0.01 <E1 / E0 <1. In the range of E1 / E0 ≦ 0.01, it is difficult to sufficiently obtain the effect of promoting the liquid crystal transition due to the application of the non-uniform electric field. In the range of E1 / E0 ≧ 1, the applied voltage becomes too large, so that the actual voltage is too high. This is because there is a problem that it is not suitable for use. Furthermore, it is preferable that 0.5 ≦ E1 / E0 ≦ 1.

  The non-uniform electric field E1 can be applied in a direction perpendicular to the substrate with respect to the liquid crystal layer by using a voltage applied between the source electrode (or gate electrode) of the thin film transistor and the transparent electrode. Further, the non-uniform electric field E1 is preferably an alternating electric field having a frequency of 100 kHz or less, and further, the amplitude is preferably attenuated in terms of time.

  A combination of two or three conditions among the three conditions that reduce the critical electric field Ec: the spray elastic constant (k11), the pretilt angle asymmetry (Δθ), and the electric field non-uniformity (E1 / E0). It is preferable to satisfy. This is because by combining these conditions, the critical electric field Ec can be more reliably reduced more reliably than when only one of the conditions is satisfied.

  For example, FIG. 46B shows the result of calculation under the same conditions as FIG. 46A except that the non-uniform electric field E1 is applied together with the substantially uniform external electric field E0. FIG. 46B shows the result when E1 / E0 = 0.03. As can be seen from the comparison between FIGS. 46 (a) and 46 (b), the critical electric field Ec is further reduced by satisfying a combination of the two conditions of asymmetry of the pretilt angle and non-uniformity of the electric field, and more rapid liquid crystal. Transition can be realized.

  The present invention provides a liquid crystal display device capable of rapidly changing the orientation from the splay alignment to the bend alignment.

It is a perspective view which shows a part of liquid crystal display device provided with the bend alignment type OCB cell. It is sectional drawing of the liquid crystal cell explaining a mode that it transfers from a splay alignment to a bend alignment. FIG. 3 is a conceptual diagram of a pixel unit according to a driving method of a liquid crystal display device according to Reference Embodiment 1 of the present invention. It is the voltage waveform figure for orientation transition used by the reference form 1 of this invention. It is a relationship figure of the bias voltage and transition time in the reference form 1 of this invention. It is a composition conceptual diagram of the pixel unit by the drive method of the liquid crystal display device which concerns on the reference form 2 of this invention. It is the voltage waveform figure for orientation transition used by the reference form 2 of this invention. It is a related figure of the bias voltage and transition time in the reference form 2 of this invention. It is a structure conceptual diagram of the pixel unit by the drive method of the liquid crystal display device which concerns on the reference form 3 of this invention. It is the voltage waveform figure for orientation transition used by the reference form 3 of this invention. It is a related figure of the bias voltage and transition time in the reference form 3 of this invention. It is a structure conceptual diagram of the pixel unit by the drive method of the liquid crystal display device which concerns on the reference form 4 of this invention. It is a normal drive voltage waveform figure of the liquid crystal display device which concerns on the reference form 4 of this invention. It is the voltage waveform figure for orientation transition used by the reference form 4 of this invention. It is the voltage waveform figure for orientation transition used by the reference form 5 of this invention. It is a schematic sectional drawing of the liquid crystal display device which concerns on the reference form 7 of this invention. It is a schematic plan view of the liquid crystal display device which concerns on the reference form 7 of this invention. It is a figure which shows the manufacturing method of the liquid crystal display device which concerns on the reference form 7 of this invention. It is a figure which shows the liquid crystal display device which concerns on the reference form 8 of this invention, Fig.19 (a) is a schematic sectional drawing of a liquid crystal display device, FIG.19 (b) is a schematic plan view of a liquid crystal display device. It is the figure which showed notionally the structure of the liquid crystal display device which concerns on Embodiment 1 of this invention, Fig.20 (a) is a schematic plan view of a liquid crystal display device, FIG.20 (b) is a schematic cross section of a liquid crystal display device. FIG. It is the figure which showed notionally the structure of the liquid crystal display device which concerns on Embodiment 1 of this invention. It is a figure which shows the other example of the liquid crystal display device which concerns on Embodiment 1 of this invention. It is the figure which showed notionally the structure of the liquid crystal display device which concerns on Embodiment 2 of this invention, Fig.23 (a) is a schematic plan view of a liquid crystal display device, FIG.23 (b) is a schematic cross section of a liquid crystal display device. FIG. 23C is a schematic sectional view of a liquid crystal display device of another example, and FIG. 23D is a schematic sectional view of a liquid crystal display device of another example. It is the figure which showed notionally the structure of the liquid crystal display device which concerns on Embodiment 3 of this invention, Fig.24 (a) is a schematic plan view of a liquid crystal display device, FIG.24 (b) is the outline which shows the distortion of an electric field. FIG. It is the figure which showed notionally the structure of the liquid crystal display device based on Embodiment 4 of this invention, Fig.25 (a) is a schematic sectional drawing of a liquid crystal display device, FIG.25 (b) is a schematic plan view. It is a figure which shows notionally the cross-sectional structure of the liquid crystal display device which concerns on Embodiment 5 of this invention. It is a figure for demonstrating the manufacturing process of the convex-shaped object formed on the glass substrate of Embodiment 5, 6 of the liquid crystal display device concerning this invention. It is a figure for demonstrating the manufacturing process of the convex-shaped object following FIG. 27 concerning this invention. It is a figure which shows the rubbing direction of the board | substrate used for Embodiment 5 of this invention. It is a structure external view of Embodiment 6 concerning this invention. It is a top view of Embodiment 6 concerning the present invention. It is a structure external view of the liquid crystal cell with which the liquid crystal display device which concerns on Embodiment 7 of this invention is equipped. It is a figure for demonstrating the manufacturing process of the convex-shaped object of the liquid crystal cell which concerns on Embodiment 7 of this invention. It is a figure which shows notionally the cross-sectional structure of the liquid crystal cell with which the liquid crystal display device which concerns on Embodiment 8 of this invention is equipped. It is a figure which shows notionally the pattern of the transparent electrode used for the liquid crystal cell which concerns on Embodiment 8 of this invention. It is principal part sectional drawing of the liquid crystal cell with which the liquid crystal display device which concerns on Embodiment 9 of this invention is equipped. FIG. 37 is a partially enlarged view of FIG. 36. It is principal part sectional drawing of the liquid crystal cell with which the liquid crystal display device which concerns on Embodiment 10 of this invention is equipped. It is a figure for demonstrating arrangement | positioning of the optical element in the liquid crystal cell with which the liquid crystal display device which concerns on Embodiment 10 of this invention is equipped. It is a figure which shows the voltage-transmittance characteristic of the liquid crystal cell with which the liquid crystal display device which concerns on Embodiment 10 of this invention is equipped. FIG. 41 (a) is a schematic diagram (a) showing a motivated orientation, and FIG. 41 (b) is a schematic diagram (b) showing a bend orientation according to the ninth embodiment of the present invention. It is a figure which shows the director of a liquid-crystal layer. It is a figure which shows CR equivalent circuit. It is a figure which shows the time change of the orientation angle ((theta) j) of the liquid crystal under the external electric field which increases with time. It is a figure which shows the relationship between a spray elastic constant (k11) and a critical electric field (Ec). It is a figure which shows the relationship between the absolute value difference ((DELTA) (theta)) of a pretilt angle, and a critical electric field (Ec). It is a figure which shows the relationship between the nonuniformity (E1 / E0) of an electric field, and a critical electric field (Ec). It is sectional drawing of a prior art example.

Explanation of symbols

20, 21 Substrate 22, 23 Electrode 24, 25 Alignment film 26 Liquid crystal layer 30, 40, 50, 71, 72 Alignment transition drive circuit 31 Liquid crystal display drive circuit 101/102 Polarizer 103 Phase compensation plate 104 Liquid crystal cell 105 Opposite substrate 106 array substrate 107 common electrode 108 pixel electrode 109/110 alignment film 111 switching element 112 liquid crystal layer 113 signal electrode line 114/114 'gate electrode line 120 b-spray alignment 121 t-spray alignment 123 disclination line 124 bend alignment A2 Pre-tilt angle 201a Array substrate 201b Counter substrate 202a Pixel electrode 221a Concave portion of pixel electrode 222a Convex portion of pixel electrode 223a Non-fitting convex portion of pixel electrode 224a Non-fitting convex portion of pixel electrode 202b Common Electrode 203a Alignment film 203am Alignment film 203ah Alignment film 203b Alignment film 203bm Alignment film 203bh Alignment film 204a Polarizer 204b Polarizer 205 Phase compensator 206 Signal electrode line 261 Signal electrode line convex part 262 Signal electrode line concave part 263 Fitting type convex portion 207 Gate electrode line 271 Gate electrode line convex portion 272 Gate electrode line concave portion 273 Gate electrode line non-fitting type convex portion 208 Switching transistor (element)
209 Horizontal electric field application line 291 Horizontal electric field application line convex part 209a Lateral electric field application line 291a Lateral electric field application line convex part 210 Liquid crystal layer 298 Liquid crystal layer 299 Liquid crystal layer 211 Liquid crystal molecule 212 Transparent insulating film 225 Electrode defect part 226 Disclination line 227b b-spray alignment 227t t-spray alignment 301,308 glass substrate 302,307 transparent electrode 303,306 alignment film 304 liquid crystal layer 304a liquid crystal alignment when no voltage is applied (spray alignment)
304b Liquid crystal alignment during voltage application (bend alignment)
305 Spacer 309 Test cell 310 Convex-shaped object 311, 314 Negative uniaxial film phase plate 312, 315 Retardation plate 313, 316 Polarizing plate 317 made of optical medium having negative refractive index anisotropy in which main axes are hybrid-arranged 318 Phase compensation plate 319 Positive uniaxial film phase plate 320 Resist thin film 321 Photomask 322 Photomask opening 323 Parallel ultraviolet ray 360 Triangular object 380 Electrode opening

Claims (8)

A liquid crystal cell with splay alignment in which the pretilt angles of the liquid crystal layer at the upper and lower interfaces of the liquid crystal layer arranged between the array substrate having pixel electrodes and the counter substrate having a common electrode are positive and negative, and aligned in parallel with each other, no voltage applied In some cases, it is splay alignment. Prior to the liquid crystal display drive, an initialization process is performed to shift from the splay alignment to the bend alignment by applying a voltage, and the active matrix type performs liquid crystal display drive in this initialized bend alignment state. In the liquid crystal display device of
In one pixel, there is at least one transverse electric field applying unit for transition excitation, and the horizontal electric field is generated by the horizontal electric field applying unit, and a voltage is applied continuously or intermittently between the pixel electrode and the common electrode. A liquid crystal display device characterized in that a transition nucleus is generated for each pixel and the entire pixel is shifted from a splay alignment to a bend alignment.   2. The liquid crystal display device according to claim 1, wherein the direction of the horizontal electric field generated by the horizontal electric field applying unit is substantially orthogonal to the alignment processing direction.   The liquid crystal display device according to claim 1, wherein the lateral electric field applying unit is an electrode deforming unit in which a peripheral part of the pixel electrode is deformed into irregularities in a plane parallel to the substrate surface.   2. The liquid crystal display device according to claim 1, wherein the lateral electric field applying unit is an electrode line deforming unit in which a signal electrode line or a gate electrode line is deformed into irregularities in a plane parallel to the substrate surface.   The lateral electric field applying unit deforms the periphery of the pixel electrode into irregularities in a plane parallel to the substrate surface, and deforms the signal electrode line or the gate electrode line into irregularities corresponding to the irregularities. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a portion.   The horizontal electric field applying unit is a horizontal electric field applying line deforming unit obtained by deforming a horizontal electric field applying line into irregularities in a plane parallel to the substrate surface, the horizontal electric field applying line being a signal electrode line or 2. The gate electrode line is disposed in the same direction through an insulating film on at least one upper layer or lower layer of the gate electrode line, and is connected to a drive circuit to which the signal electrode line or gate electrode line is connected. The liquid crystal display device described.   7. The liquid crystal display device according to claim 6, wherein the horizontal electric field applying line is cut off from a driving circuit during normal liquid crystal display after orientation transition. A liquid crystal cell with splay alignment in which the pretilt angle of the liquid crystal layer at the upper and lower interface of the liquid crystal layer between the array substrate and the counter substrate is positive / negative and aligned in parallel with each other. Prior to the active matrix type liquid crystal display device that performs a liquid crystal display drive in the initialized bend alignment state, an initialization process is performed to transition from splay alignment to bend alignment by voltage application.
A liquid crystal display device comprising at least one of a pixel electrode or a common electrode in which a defective portion is formed in at least one place for applying a transverse electric field for transition excitation in one pixel.