KR100683140B1 - Transmittive liquid crystal display device - Google Patents

Abstract

The transmissive liquid crystal display device of the present invention is a transmissive liquid crystal display device having a layered liquid crystal cell having a large number of nematic liquid crystal molecules, the liquid crystal cell being disposed on one side of the liquid crystal cell along a predetermined incident side rubbing direction. An incident side alignment film for horizontally aligning molecules to have a predetermined incident side pretilt angle; An emission side alignment layer arranged to face the incident side alignment layer with the liquid crystal cell interposed therebetween to vertically align the nematic liquid crystal molecules to have a predetermined exit side pretilt angle; An incident side substrate made of a transparent material disposed to face the liquid crystal cell with the incident side alignment layer therebetween; An exit side substrate of a transparent material disposed opposite to the liquid crystal cell with the exit side alignment layer interposed therebetween; A plurality of fringe fields are formed on the incidence side substrate and generate a fringe electric field inside the liquid crystal cell to move a horizontal array direction of nematic liquid crystal molecules arranged by the incidence side alignment layer and the exit side alignment layer when a predetermined power is applied. A pair of pixel electrodes and counter electrodes of transparent material; A polarizing plate disposed on the incidence side substrate and linearly polarizing predetermined backlight light along a predetermined transmission axis to transmit the backlight to the liquid crystal cell; And an inspection plate disposed on the emission side substrate and having a transmission axis for selectively transmitting backlight light whose polarization state is changed by the nematic liquid crystal molecules while passing through the liquid crystal cell. And a phase compensation film is formed between any one of the polarizing plate and the incident side substrate and between the analyzer and the emission side substrate.

Description

Transmissive Liquid Crystal Display {TRANSMITTIVE LIQUID CRYSTAL DISPLAY DEVICE}

1 is an exploded perspective view of a transmissive liquid crystal display device according to an embodiment of the present invention;

FIG. 2 is a plan view of the incident side substrate of FIG. 1; FIG.

3 is a diagram illustrating a relationship between a fringe electric field, a transmission axis, and a rubbing direction after formation of a fringe electric field of a transmissive liquid crystal display device according to an exemplary embodiment of the present invention;

4 is an operation explanatory diagram of a transmissive liquid crystal display device according to an embodiment of the present invention, FIG. 4A is an operation explanatory diagram before forming a fringe field, and FIG. 4B is an operation explanatory diagram after forming a fringe field;

5 is a graph showing a change in transmittance according to retardation in a liquid crystal cell of a transmissive liquid crystal display according to an exemplary embodiment of the present invention;

FIG. 6 is a cross-sectional view of a main portion of a phase compensation film of a transmissive liquid crystal display device according to another exemplary embodiment of the present invention. FIG. 6A is a view when a phase compensation film is interposed between a polarizing plate and an incident side substrate. A drawing in which the phase compensation film is interposed between the analyzer and the emission substrate,

7 is an exploded perspective view of a conventional transmissive liquid crystal display device;

8 is an operation explanatory diagram of a conventional transmissive liquid crystal display device, FIG. 8A is an operation explanatory diagram before forming a fringe field, and FIG. 8B is an operation explanatory diagram after formation of a fringe field.

(Explanation of symbols for the main parts of the drawing)

10, 110: liquid crystal cell 12, 112: nematic liquid crystal molecules

21, 121: incident side alignment film 23, 123: exit side alignment film

31,131: incident side substrate 33, 133: exit side substrate

41, 141: polarizer 43, 143: detector plate

51 and 151 pixel electrodes 53 and 153 counter electrodes

61: gate bus line 63: data bus line

65: common signal line 67: thin film transistor

70, 80: phase compensation film 72, 82: liquid crystal molecules for phase compensation

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmissive liquid crystal display, and more particularly, to an FFS (Fringe Field Switching) mode transmissive liquid crystal display using a liquid crystal cell in which nematic liquid crystal molecules are arranged horizontally and a pixel electrode and a counter electrode formed on an incident side substrate. It is about.

As a liquid crystal display device using backlight light as a light source, that is, a transmissive liquid crystal display device, a TN (Twisted Nematic) mode liquid crystal display device in which nematic liquid crystal molecules use horizontally aligned liquid crystal cells such that their horizontal array direction is rotated by 90 degrees; VA (Vertical Aligned) mode liquid crystal display device in which nematic liquid crystal molecules are vertically arranged liquid crystal cell, pixel electrode made of opaque material and arranged on the incident side substrate using liquid crystal cell in which nematic liquid crystal molecules are horizontally aligned And In-Plane Switching (IPS) mode liquid crystal display device having a counter electrode and FFS (Fringe Field) having higher transmittance, higher aperture ratio, faster response speed, lower voltage drive characteristics, and wide viewing angle characteristics than the transmissive liquid crystal display device. Switching mode) A liquid crystal display device is provided. The FFS mode liquid crystal display device has been patented by the present applicant (Korean Patent Application No. 98-9243), and is shown in FIG.

7 is an exploded perspective view of a conventional transmissive liquid crystal display.

In the conventional transmissive liquid crystal display device, as shown in the drawing, a layered liquid crystal cell 110 having a plurality of nematic liquid crystal molecules 112 and an incident side alignment layer disposed on both sides of the liquid crystal cell 110 ( 121 and the incidence side substrate 131 and the outgoing side substrate of the transparent material which are disposed to face each other and are spaced apart from each other by the cell gap d between the incidence side alignment layer 123 and the incidence side alignment layer 121 and the outgoing side alignment layer 123. 133, the plurality of pairs of pixel electrodes 151 and counter electrodes 153 provided on the incident side substrate 131, and the incident side substrate 131 and the exit side substrate 133, respectively, to face each other. It has the polarizing plate 141 and the analyzer plate 143 arrange | positioned.

The dielectric anisotropy and refractive index anisotropy of the liquid crystal cell 110 are respectively positive.

The incident side alignment layer 121 horizontally orients the nematic liquid crystal molecules 112 along the predetermined incident side rubbing direction R1 to have a predetermined pretilt angle, and the exit side alignment layer 123 is formed of the nematic liquid crystal molecules 112. ) Is horizontally oriented so as to have a predetermined pretilt angle along the emission-side rubbing direction R2 which is the reverse of the incident-side rubbing direction R1. At this time, the incident rubbing direction R1 and the exit rubbing direction R2 are 45 for the liquid crystal having a dielectric constant anisotropy with respect to the fringe electric field F generated by the pixel electrode 51 and the counter electrode 53. Between 90 degrees and 90 degrees, in the case of a liquid crystal having anisotropy of dielectric anisotropy, a horizontal angle is formed between 0 degrees and 45 degrees. By doing so, the transmittance of the transmissive liquid crystal display device can be increased. The nematic liquid crystal molecules 112 of the liquid crystal cell 110 are horizontally oriented along the surface direction of the alignment layers 121 and 123 in the state where the fringe electric field F is not formed.

The transmission axis P1 of the polarizing plate 141 is parallel to the incident rubbing direction R1 and the emission side rubbing direction R2, and the transmission axis P2 of the detector plate 143 is the transmission axis of the polarizing plate 141. Perpendicular to (P1).

A plurality of gate bus lines, common signal lines, and data bus lines (not shown) are formed on the incident side substrate 131, and these bus lines form unit pixel spaces in a matrix form. A thin film transistor (not shown) having a channel layer, a drain electrode, and a source electrode is formed in the intersection region of these bus lines to act as a switching element.

In each unit pixel space, a plurality of counter electrodes 153 to which a common signal is applied are formed from a common signal line, and a pixel electrode 151 overlapping the counter electrode 153 is separated from the counter electrode 153. Formed. The pixel electrode 151 and the counter electrode 153 are made of a transparent material. These electrodes 151 and 153 may be separately formed on the incident side substrate 131 or may be formed with a stepped gap through an insulating film (not shown). A fringe electric field F is generated inside the liquid crystal cell 110 when a voltage above a threshold is applied between the electrodes 151 and 153. Accordingly, the horizontal alignment direction of the nematic liquid crystal molecules 112 is shifted. do. The width of the counter electrode 153 and the distance between each other, and the distance between the counter electrode 153 and the pixel electrode 151 are parabolic fringes inside the liquid crystal cell 110 and on the surfaces of the electrodes 151 and 153. The electric field F should be selected to be generated, and the separation distance between the pixel electrode 151 and the counter electrode 153 should be smaller than the distance d between the two substrates 131 and 133.

Further, a color filter (not shown) for selectively transmitting red light, green light, and blue light is disposed between the emission side substrate 133 and the emission side alignment layer 123.

The operation of a conventional transmissive liquid crystal display having such a configuration will be described with reference to FIG. FIG. 8 is an operation explanatory diagram of a conventional transmissive liquid crystal display device, FIG. 8A is an operation explanatory diagram before forming a fringe field, and FIG. 8B is an operation explanatory diagram after formation of a fringe field.

After the scan signal is not applied to the gate bus line (not shown), the backlight light incident on the polarizing plate 141 passes through the transmission axis P1 and then travels along the width direction of the liquid crystal cell 110. . Here, since the transmission axis P1 of the polarizing plate 141 and the long axis direction of the nematic liquid crystal molecules 112 coincide with each other, the natural light flowing into the liquid crystal cell 110 has only the long axis component of the nematic liquid crystal molecules 112. . Therefore, natural light travels inside the liquid crystal cell 110 while maintaining the linearly polarized state when passing through the polarizer 141. Since the transmission axis P1 of the polarizer 141 and the transmission axis P2 of the analyzer 143 are perpendicular to each other, the backlight light reaching the detector 143 may not pass through the detector 143. Therefore, the screen of the transmissive liquid crystal display device becomes dark.

On the other hand, when the scan signal is applied to the gate bus line and the display signal is applied to the data bus line, the thin film transistor is turned on so that a voltage greater than the threshold voltage is applied between the counter electrode 153 and the pixel electrode 151 and the fringe field is applied. (F) is generated. In this case, the fringe electric field F has only a horizontal component in the middle of the electrodes 151 and 153, but has both a vertical component and a horizontal component in an adjacent region of the electrode. By the fringe electric field F, the nematic liquid crystal molecules 112 of the liquid crystal cell 110 are rotated in a plane, and their major axes are the transmission axis P1 of the polarizing plate 141 and the transmission axis P2 of the analyzer plate 143. And rearranged to form an inclination, respectively. At this time, the long axis of the nematic liquid crystal molecules 112 rotates clockwise when the dielectric anisotropy Δe is positive and counterclockwise when negative. However, the major axes of the nematic liquid crystal molecules 12 positioned in the adjacent regions of the alignment layers 121 and 123 coincide with the rubbing directions R1 and R2 of the alignment layers 121 and 123.

In the arrangement state of the nematic liquid crystal molecules 112, since the transmission axis P1 of the polarizing plate 141 and the long axis of the nematic liquid crystal molecules 112 cross each other at a predetermined horizontal angle, the backlight light passing through the liquid crystal cell 110 is provided. Has a major axis component and a minor axis component of the nematic liquid crystal molecule 112. The long-axis component and the short-axis component of the nematic liquid crystal molecules 112 of natural light proceed at different speeds in the liquid crystal cell 110 according to the birefringence characteristics of the nematic liquid crystal molecules 112, and reach the spectrophotometer 143. The polarization state changes. At this time, the polarization state is generally an elliptical polarization state, and only light of the component in the transmission axis direction of the analyzer plate 143 passes through the transmission axis P2. In addition, when it reaches the analyzer plate 143, when it is changed into linearly polarized light twisted by 90 degrees, the maximum transmittance is shown.

However, according to the conventional FFS mode transmissive liquid crystal display device, since the rubbing process is performed on both transparent substrates 131 and 133, the magnetic liquid crystal molecules 112 must be oriented so that defects due to rubbing exist. In this case, there is a problem in that the image quality deteriorates due to an increase in the arrangement nonuniformity of the magnetic liquid crystal molecules 112. In particular, when using the Normally Black Mode to improve the dark (Dark) state, the problem caused by the irregularity of the arrangement of the magnetic liquid crystal molecules 112 becomes serious.

Furthermore, when both the pixel electrode 151 and the counter electrode 153 are disposed on the incident side substrate 131, the fringe electric field F formed by applying a voltage to these electrodes 151 and 153 is the incident side substrate 131. Since the amount of twist of the nematic liquid crystal molecules is also reduced in the area adjacent to the emission side substrate 133 rather than the adjacent region of the (), the unevenness of the nematic liquid crystal molecules 112 is increased, resulting in poor image quality. There was a problem.

In addition, according to the conventional FFS mode transmissive liquid crystal display device, when the voltage is applied to the pixel electrode 151 and the counter electrode 153 to form the fringe electric field F, the nematic liquid crystal molecules 112 are in a horizontal state. There is a problem that the response time is relatively slow because it is twisted.

Accordingly, an object of the present invention is to reduce the irregularity of arrangement of nematic liquid crystal molecules, and to transmit nematic liquid crystal molecules along a vertical direction when driving voltage is applied to the pixel electrode and the counter electrode. To provide.

In order to achieve the above object, the present invention, in the transmissive liquid crystal display device having a layered liquid crystal cell having a plurality of nematic liquid crystal molecules, disposed on one side of the liquid crystal cell along a predetermined incident side rubbing direction An incident side alignment layer which horizontally aligns the nematic liquid crystal molecules to have a predetermined incident side pretilt angle; An emission side alignment layer arranged to face the incident side alignment layer with the liquid crystal cell interposed therebetween to vertically align the nematic liquid crystal molecules to have a predetermined exit side pretilt angle; An incident side substrate made of a transparent material disposed to face the liquid crystal cell with the incident side alignment layer therebetween; An exit side substrate of a transparent material disposed opposite to the liquid crystal cell with the exit side alignment layer interposed therebetween; A plurality of fringe fields are formed on the incidence side substrate and generate a fringe electric field inside the liquid crystal cell to move a horizontal array direction of nematic liquid crystal molecules arranged by the incidence side alignment layer and the exit side alignment layer when a predetermined power is applied. A pair of pixel electrodes and counter electrodes of transparent material; A polarizing plate disposed on the incidence side substrate and linearly polarizing predetermined backlight light along a predetermined transmission axis to transmit the backlight to the liquid crystal cell; And an inspection plate disposed on the emission side substrate and having a transmission axis for selectively transmitting backlight light whose polarization state is changed by the nematic liquid crystal molecules while passing through the liquid crystal cell. A transmissive liquid crystal display device having a biaxial property and a phase compensation film having a value between 0.05 and 1.5 of an absolute value of the difference in refractive index in three directions. To provide.

Here, when the dielectric anisotropy of the nematic liquid crystal molecules is positive so that the transmittance is improved, the incidence side rubbing direction forms a horizontal angle between 45 degrees and 90 degrees with respect to the fringe field, and the dielectric anisotropy of the nematic liquid crystal molecules is In the negative case, the incidence side rubbing direction may be a horizontal angle between 0 degrees and 45 degrees with respect to the fringe electric field.

And, the transmission axis of the polarizing plate forms a horizontal angle between -10 degrees to +10 degrees and 170 degrees to 190 degrees with respect to the rubbing direction of the incident side alignment layer, and the transmission axis of the analyzer is perpendicular to the transmission axis of the polarizing plate. Or a horizontal angle between -10 degrees and +10 degrees and 170 degrees to 190 degrees with respect to the direction, or the transmission axis of the polarizing plate is -10 degrees to +10 degrees and 170 degrees to the rubbing direction of the incident side alignment layer. A horizontal angle between 190 degrees and the transmissive axis of the analyzer may be configured to achieve a horizontal angle between −10 degrees and +10 degrees and 170 degrees to 190 degrees with respect to a direction parallel to the transmissive axis of the polarizer.

In addition, the incident side pretilt angle may be configured to have a value between 0 degrees and 15 degrees, and the exit side pretilt angle may have a value between 65 degrees and 90 degrees.

In addition, it is preferable that a dopant is added to the liquid crystal cell so that d / p < 0.5 (where d is the gap of the liquid crystal cell and p is the pitch of the liquid crystal cell).

In addition, the emission side alignment layer may be subjected to a rubbing treatment in a direction parallel to the incident side rubbing direction.

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Here, the phase compensation film may be inclined at a predetermined angle in the direction of the smallest refractive index from the direction of the largest refractive index along the incident side rubbing direction.

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In addition, it is preferable that the retardation dΔn of the liquid crystal cell has a value between 0.45 and 0.75 so that the transmittance is improved.

Here, the cell gap d of the liquid crystal cell is preferably 5 μm or less so that the response speed is improved.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is an exploded perspective view of a transmissive liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a plan view of an incident side substrate of FIG. 1, and FIG. 3 is a fringe of a transmissive liquid crystal display device according to an embodiment of the present invention. The relationship between the fringe electric field after the electric field formation, the transmission axis, and the rubbing direction.

In the transmissive liquid crystal display device according to the exemplary embodiment of the present invention, as shown in the drawing, a layered liquid crystal cell 10 having a plurality of nematic liquid crystal molecules 12 and both sides of the liquid crystal cell 10 are respectively shown. The incidence side substrate of a transparent material disposed so as to be spaced apart from the incidence side alignment layer 21 and the outgoing side alignment layer 23 and the incidence side alignment layer 21 and the outgoing side alignment layer 23 by a cell gap d. 31 and the emission side substrate 33, a plurality of pairs of pixel electrodes 51 and the counter electrode 53 provided on the incident side substrate 31, the incident side substrate 31 and the emission side substrate 33 The polarizing plate 41 and the analyzer 43 are respectively arrange | positioned so that it may mutually oppose.

The dielectric anisotropy and refractive index anisotropy of the liquid crystal cell 10 are positive, respectively, and dopants are added to the liquid crystal cell such that d / p < 0.5, where d is the gap of the liquid crystal cell and p is the pitch of the liquid crystal cell.

The incident side alignment layer 21 horizontally orients the nematic liquid crystal molecules 12 to have a predetermined pretilt angle along the predetermined incident side rubbing direction R1, and the exit side alignment layer 23 has predetermined nematic liquid crystal molecules. Vertically align so as to have an exit side pretilt angle of. At this time, the incident side rubbing direction R1 forms a horizontal angle α between 45 degrees and 90 degrees with respect to the fringe field F generated by the pixel electrode 51 and the counter electrode 53. By doing so, the transmittance of the transmissive liquid crystal display device can be increased. The nematic liquid crystal molecules 12 of the liquid crystal cell 10 are horizontally oriented along the surface direction of the incident side alignment layer 21 in the adjacent region of the incident side substrate 31 while the fringe field F is not formed. In the adjacent region of the emission-side substrate 33, the alignment direction is vertically aligned along the surface direction of the emission-side alignment layer 23. At this time, the pretilt angle in the adjacent region of the incident side alignment layer 21 has a value between 0 degrees and 15 degrees, and the pretilt angle in the adjacent region of the exit side alignment layer 23 is between 65 degrees and 90 degrees. It can be configured to have a value.

The transmission axis P1 of the polarizing plate 41 is parallel to the rubbing direction R1 of the incident side alignment film 21, and the transmission axis P2 of the analyzer 43 is the transmission axis P1 of the polarizing plate 41. Is perpendicular to At this time, the transmission axis P1 of the polarizing plate 41 forms an angle between -10 degrees to +10 degrees and 170 degrees to 190 degrees with respect to the rubbing direction R1 of the incident side alignment layer 21, and the analyzer The transmission axis P2 of 43 may be configured to form a horizontal angle between −10 degrees and +10 degrees and 170 degrees to 190 degrees with respect to the direction perpendicular to the transmission axis P1 of the polarizing plate 41.

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On the incidence side substrate 31, a plurality of gate bus lines 61a and 61b are spaced apart at regular intervals, and adjacent to the gate bus line 61b, the common signal line 65 is formed without a step difference. It is arrange | positioned in the same direction as 61a, 61b).

A plurality of data bus lines 63a and 63b are spaced apart at regular intervals along the transverse direction of these gate bus lines 61a and 61b. These bus lines 61a, 61b, 63a, and 63b form a unit pixel space in a matrix form, and a thin film transistor 67 serving as a switching element is formed in an intersection area of these bus lines 61a and 63a. . The thin film transistor 67 includes a channel layer (not shown) formed outside the gate bus line 61a, a drain electrode overlapping one side of the channel layer and extending from the data bus line 63a (not shown), A source electrode (not shown) overlaps with the other side of the channel layer and is in electrical contact with the pixel electrode 51.

In each unit pixel space, a plurality of counter electrodes 53 to which a common signal is applied from the common signal line 65 are formed, and the pixel electrodes 51 overlapping with the counter electrodes 53 include the counter electrodes 53. Correspondingly formed separately. The pixel electrode 51 and the counter electrode 53 are both made of a transparent material, and these electrodes 51 and 53 are separately formed on the incident side substrate 31 or interposed through an insulating film (not shown). It can be formed with a step. When a voltage equal to or greater than a threshold is applied between the electrodes 51 and 53, a fringe electric field F is generated inside the liquid crystal cell 10, and the arrangement state of the nematic liquid crystal molecules 12 is changed. The width of the counter electrode 53 and the distance between each other, and the distance between the counter electrode 53 and the pixel electrode 51 are parabolic fringes inside the liquid crystal cell 10 and on the surfaces of the electrodes 51 and 53. The electric field F should be selected to be generated, and the separation distance between the pixel electrode 51 and the counter electrode 53 should be smaller than the distance d between the two substrates 31 and 33.

Further, a color filter (not shown) for selectively transmitting red light, green light, and blue light is disposed between the emission side substrate 33 and the emission side alignment layer 23.

The operation of the transmissive liquid crystal display having the above configuration will be described with reference to FIGS. 4 and 5. 4 is an operation explanatory diagram of a transmissive liquid crystal display device according to an embodiment of the present invention, FIG. 4A is an operation explanatory diagram before forming a fringe field, FIG. 4B is an operation explanatory diagram after forming a fringe field, and FIG. A graph showing a change in transmittance according to retardation in a liquid crystal cell of a transmissive liquid crystal display according to an exemplary embodiment.

In the state where the scan signal is not applied to the gate bus line 61a, the backlight light incident on the polarizing plate 41 passes through the transmission axis P1 and then travels along the width direction of the liquid crystal cell 10. Here, since the transmission axis P1 of the polarizing plate 41 and the long axis direction of the nematic liquid crystal molecules 12 coincide with each other, the natural light flowing into the liquid crystal cell 10 has only the long axis component of the nematic liquid crystal molecules 12. . Therefore, the natural light travels inside the liquid crystal cell 10 while maintaining the linearly polarized state when passing through the polarizing plate 41. Since the transmission axis P1 of the polarizing plate 41 and the transmission axis P2 of the analyzer 43 are perpendicular to each other, the backlight light reaching the detector 43 does not pass through the detector 43. Therefore, the screen of the transflective liquid crystal display device becomes dark.

On the other hand, when a scan signal is applied to the gate bus line 61a and a display signal is applied to the data bus line 63a, the thin film transistor 67 (see FIG. 2) is turned on to conduct the counter electrode 53 and the pixel electrode 51. A voltage greater than the threshold voltage is applied between the fringes to generate the fringe field F. At this time, the fringe electric field F has only a horizontal component in the center of the electrodes 51 and 53, but has both a vertical component and a horizontal component in the adjacent region of the electrode. The nematic liquid crystal molecules 12 positioned in the adjacent region of the incident side alignment film 21 are rotated on the plane by the fringe field F, and the major axis of the nematic liquid crystal molecules 12 is the transmission axis P1 and the analyzer 43 of the polarizing plate 41. Rearranged to form an inclination with the transmission axis (P2) of each. At this time, the long axis of the nematic liquid crystal molecules 12 rotates clockwise because the dielectric anisotropy Δe is positive. On the other hand, the nematic liquid crystal molecules 12 positioned in the region adjacent to the emission side alignment layer 23 maintain their vertical alignment almost despite the formation of the fringe electric field F. FIG.

Since the transmission axis P1 of the polarizing plate 41 and the long axis of the nematic liquid crystal molecules 12 intersect at a predetermined horizontal angle α in the arrangement state of the nematic liquid crystal molecules 12, the liquid crystal cell 10 is opened. The backlight light passing through has the major axis component and the minor axis component of the nematic liquid crystal molecule 12. The long-axis component and the short-axis component of the nematic liquid crystal molecules 12 of the backlight light proceed at different speeds in the liquid crystal cell 10 according to the birefringence characteristics of the nematic liquid crystal molecules 12, and reach the analyzer plate 43. When a predetermined phase difference occurs. At this time, since the short axis of the nematic liquid crystal molecules 12 corresponds to the optical axis as well as the long axis, the nematic liquid crystal molecules 12 adjacent to the emission side alignment layer 23 that maintain the vertical alignment state do not disturb the progress of the backlight light. Do not. Here, the polarization state of the backlight light reaching the analyzer 43 depends on the phase difference and the magnitude of the major axis component and minor axis component of the nematic liquid crystal molecule 12 of the backlight light. For example, when the phase difference is 90 degrees and the magnitude of the major axis component and the minor axis component of the nematic liquid crystal molecule 12 of the backlight light are the same, it becomes right circularly polarized light, and the long axis component of the nematic liquid crystal molecule 12 of the backlight light is formed. If the magnitude of the unidirectional component is different from that of the right elliptical polarization. The detector plate 43 transmits light having such a polarization state to only components in the transmission axis direction. At this time, the change in transmittance according to the retardation of the transmitted light is shown in FIG. The horizontal axis of FIG. 5 represents the retardation, and the vertical axis represents the transmittance, respectively. The pretilt angle is 90 degrees on the exit side substrate 33, 2 degrees on the incident side substrate 31, the rubbing angle is 12 degrees, and the liquid crystal cell 10 ), The cell gap d is 4 µm and the dielectric anisotropy is -4. As shown in Fig. 5, the largest transmittance can be obtained between 0.45 and 0.75.

In the above-described embodiment, the transmission axis P1 of the polarizing plate 41 is parallel to the rubbing direction R1 of the incident side alignment film 21, and the transmission axis P2 of the analyzer 43 is of the polarizing plate 41. Although it is configured to be perpendicular to the transmission axis P1 to operate in NB, that is, Normally Black mode, the transmission axis P1 of the polarizing plate 41 is parallel to the rubbing direction R1 of the incident side alignment film 21, The transmission axis P2 of the analyzer 43 may be configured to be parallel to the transmission axis P1 of the polarizer 41, and thus may be operated in NW, that is, normally white mode. Since the short axis of the nematic liquid crystal molecules 12 corresponds to the optical axis like the long axis, the operation of the transmissive liquid crystal display according to the present invention may be described in the same manner as described above. At this time, the transmission axis P1 of the polarizing plate 41 forms a horizontal angle between −10 degrees and +10 degrees and 170 degrees to 190 degrees with respect to the rubbing direction R1 of the incident side alignment layer 21. The transmission axis P2 of 43 may be configured to form a horizontal angle between −10 degrees and +10 degrees and 170 degrees to 190 degrees with respect to the direction parallel to the transmission axis P2 of the polarizing plate 41.

In the embodiment described above, the dielectric anisotropy of the nematic liquid crystal molecules 12 is positive, and the incident-side rubbing direction R1 is a fringe electric field F generated by the pixel electrode 51 and the counter electrode 53. Although the horizontal angle of 45 degrees to 90 degrees with respect to the relative angle, the dielectric anisotropy of the nematic liquid crystal molecules 12 is negative, and the incident side rubbing direction R1 is formed by the pixel electrode 51 and the counter electrode 53. It can be configured to achieve a horizontal angle between 0 degrees and 45 degrees with respect to the generated fringe electric field (F).

In addition, since the nematic liquid crystal molecules 12 are partially horizontally aligned in the above-described embodiment, a biaxial or uniaxial phase compensation film may be provided on at least one of the polarizing plate 41 and the analyzer 43 to obtain a wide viewing angle. Of course it can be used. When the retardation film is biaxially configured, the absolute value of the difference in the refractive indexes in the three directions may be in a range of 0.05 to 1.5, wherein the refractive index is the largest along the incident side rubbing direction R1. Can be configured to be inclined at a predetermined angle in the direction of the smallest refractive index. On the other hand, when the phase compensation film is configured to have a short axis, as shown in Fig. 6, the incident side alignment film 21 adjacent to the arrangement state of the nematic liquid crystal molecules 12 of the liquid crystal cell 10 formed by the fringe field is formed. ) And the exit side alignment layer 23 can be symmetrically inclined. FIG. 6 is a cross-sectional view of a main portion of a phase compensation film of a transmissive liquid crystal display according to another exemplary embodiment of the present invention. FIG. 6A is a view when a phase compensation film is interposed between a polarizing plate and an incident substrate, and FIG. 6B. FIG. 7 is a diagram when the phase compensation film is interposed between the analyzer and the emission side substrate. 6A and 6B, the substrates 31 and 33 and the alignment layers 21 and 23 interposed between the liquid crystal cells 10 of the phase compensation films 70 and 80 are omitted, and reference numerals 72 and 82 denote phase compensation. For each liquid crystal molecule.

 In addition, although the emission side alignment layer 23 is not subjected to the rubbing treatment in the above-described embodiment, rubbing treatment may be performed in a direction parallel to the incident side alignment layer 21.

As described above, according to the present invention, the arrangement nonuniformity of the nematic liquid crystal molecules can be reduced to improve image quality, and the nematic liquid crystal molecules along the vertical direction when the driving voltage is applied to the pixel electrode and the counter electrode. By turning, the response speed can be improved.

Claims (14)

A transmissive liquid crystal display device having a layered liquid crystal cell having a plurality of nematic liquid crystal molecules, An incident side alignment layer disposed on one side of the liquid crystal cell to horizontally align the nematic liquid crystal molecules along a predetermined incident side rubbing direction to have a predetermined incident side pretilt angle; An emission side alignment layer arranged to face the incident side alignment layer with the liquid crystal cell interposed therebetween to vertically align the nematic liquid crystal molecules to have a predetermined exit side pretilt angle; An incident side substrate made of a transparent material disposed to face the liquid crystal cell with the incident side alignment layer therebetween; An exit side substrate of a transparent material disposed opposite to the liquid crystal cell with the exit side alignment layer interposed therebetween; A plurality of fringe fields are formed on the incidence side substrate and generate a fringe electric field inside the liquid crystal cell to move a horizontal array direction of nematic liquid crystal molecules arranged by the incidence side alignment layer and the exit side alignment layer when a predetermined power is applied. A pair of pixel electrodes and counter electrodes of transparent material; A polarizing plate disposed on the incidence side substrate and linearly polarizing predetermined backlight light along a predetermined transmission axis to transmit the backlight to the liquid crystal cell; And And an analyzer disposed on the exit side substrate and having a transmission axis for selectively transmitting backlight light whose polarization state is changed by the nematic liquid crystal molecules while passing through the liquid crystal cell. A phase compensation film is formed between any one of the polarizing plate and the incident side substrate and between the analyzer and the exit side substrate, and having a biaxial property and having an absolute value of the difference in refractive index in three directions between 0.05 and 1.5. A transmissive liquid crystal display device. The method of claim 1, The dielectric anisotropy of the nematic liquid crystal molecules is positive; The incidence side rubbing direction forms a horizontal angle between 45 degrees and 90 degrees with respect to the fringe electric field. The method of claim 1, The dielectric anisotropy of the nematic liquid crystal molecules is negative; And said incident side rubbing direction forms a horizontal angle between 0 degrees and 45 degrees with respect to said fringe electric field. The method of claim 1, The transmission axis of the polarizing plate forms a horizontal angle between -10 degrees and +10 degrees and 170 degrees and 190 degrees with respect to the rubbing direction of the incident side alignment layer; And a transmissive axis of the spectroscopic plate forms a horizontal angle between -10 degrees and +10 degrees and 170 degrees to 190 degrees with respect to a direction perpendicular to the transmissive axis of the polarizing plate. The method of claim 1, The transmission axis of the polarizing plate forms a horizontal angle between -10 degrees and +10 degrees and 170 degrees and 190 degrees with respect to the rubbing direction of the incident side alignment layer; And a transmissive axis of the spectrophotometer forms a horizontal angle between -10 degrees and +10 degrees and 170 degrees to 190 degrees with respect to a direction parallel to the transmissive axis of the polarizing plate. The method of claim 1, The incident side pretilt angle has a value between 0 degrees and 15 degrees; The emission-side pretilt angle has a value between 65 degrees and 90 degrees. The method of claim 1, A dopant is added to said liquid crystal cell so that d / p <0.5 (where d is a gap of a liquid crystal cell and p is a pitch of a liquid crystal cell). The method of claim 1, The emission type alignment layer is subjected to a rubbing treatment in a direction parallel to the incident side rubbing direction. delete delete The method of claim 1, The phase compensation film is a transmissive liquid crystal display device characterized in that inclined at a predetermined angle in the direction of the smallest refractive index from the direction of the largest refractive index along the incident side rubbing direction. delete The method of claim 1, And a retardation dΔn of the liquid crystal cell having a value between 0.45 and 0.75. The method of claim 13, A cell gap d of the liquid crystal cell is 5 μm or less.

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