JPH06324328A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display element capable of realizing a wide and uniform visual angle characteristic without generating inconvenient coloration separate from the color intrinsically desired to be expressed on images. CONSTITUTION:A second liquid crystal cell 23 which is multidomain cells twist arranged in a direction reverse from the twist direction of arrangement of the liquid crystal molecules of a first liquid crystal cell 21 which is multiedomain cells is arranged in superposition on this first liquid crystal cell 21, by which the coloration of the transmitted light of the first liquid crystal cell 21 is eliminated. Namely, the light rays having the optical rotatory angles varying with each of the respective wavelengths transmitted through the liquid crystal cell 21 are made incident on the second liquid crystal cell 23 of a multidomain system of the reverse twisted liquid crystal molecule arrangement, by which the polarization state is returned to the polarization state before the transmission of the first liquid crystal cell 21 over the light beams of the entire wavelengths and the nearly colorless image display is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device,
In particular, the present invention relates to a liquid crystal display device having improved viewing angle characteristics such as display contrast and display color of an image.

[0002]

2. Description of the Related Art Liquid crystal display elements are widely used in a wide variety of products such as wrist watches, calculators, Japanese word processors, and personal computers because they have the great features of thinness, light weight, and low power consumption. Most of these liquid crystal display devices are Twisted Nematic (hereinafter abbreviated as TN) type liquid crystal, or STN (Supe
r Twisted Nematic (hereinafter abbreviated as STN) type liquid crystal is used. For example, as a display used in a personal computer, a display having a large screen and a large display capacity is generally used, and the size of the display surface is A.
The so-called VGA display specifications with 4 or more sizes and 640 pixels in the horizontal and 480 pixels in the vertical have become the mainstream.

Liquid crystal display devices currently in the mainstream can be roughly classified into two types, an active matrix type and a simple matrix type. Both types of VG are as described above.
It is possible to realize the performance that almost satisfies the A display specifications. One of the main features of the simple matrix method is that it can be made inexpensive, and it is the two substrates with strip-shaped transparent electrodes arranged facing each other with a gap so that the transparent electrodes intersect in a matrix. This is due to the simple structure in which the liquid crystal layer is placed and sandwiched between the two. In order to realize the VGA display specifications by the simple matrix method having such a simple structure, the transmittance-applied voltage (TV) characteristic of the liquid crystal layer is required to have steepness. Here, the steepness refers to the degree of change in the transmitted light of the liquid crystal layer when the value of the voltage applied to the liquid crystal layer is changed. The TV characteristic can be made steep by increasing the total twist angle of the alignment of the liquid crystal layer (hereinafter referred to as the twist angle).

However, practically, the twist angle of a simple matrix type liquid crystal display element is required to be 180 degrees or more, and STN type liquid crystal is often used. When the twist angle becomes large like this, the display image is caused by optical rotation dispersion. However, there is a problem that it is colored in an inconvenient color different from the color of the image to be originally expressed.

On the other hand, in the active matrix system,
Thin film transistor for each pixel
Since a switching element such as r; hereinafter abbreviated as TFT) is arranged, the liquid crystal application voltage applied to the liquid crystal layer of each pixel can be set to an arbitrary voltage ratio regardless of the number of scanning lines. Therefore, the response speed is fast, and a sufficient response speed can be obtained even for a moving image of a television or a mouse used for CAD or the like. Control of voltage application to the liquid crystal layer is TF
Since a switching element such as T is used, it is not necessary to increase the steepness of the transmittance-applied voltage characteristic as in the simple matrix method, and it is not necessary to increase the twist angle. Therefore, a TN type liquid crystal having a twist angle of about 90 degrees is often used.

As described above, the steepness of the electro-optical characteristics of the TN type liquid crystal having a twist angle of 90 degrees is S with a larger twist angle.
Although inferior to the TN type liquid crystal, the twist angle is small, so the optical rotatory dispersion is small, and in the case of a polarizing plate arrangement (normally open) where a bright display can be obtained when no voltage is applied, the above-mentioned inconvenient coloring It is possible to obtain an image display that is almost inconspicuous. Therefore, by combining the active matrix system and the TN cell, it is possible to realize a liquid crystal display device having a large display capacity at a high speed. A full color image can be displayed by further combining this with a color filter.

[0007]

However, in the liquid crystal display elements according to these conventional techniques, there is a problem that the brightness and darkness of the display appear to be reversed depending on the direction and angle of viewing the screen, or the display image becomes dark and difficult to see. is there. Alternatively, there is a problem that the displayed image is colored inconveniently in addition to the original color of the image.

As a method of improving this problem, conventionally, a method of improving the viewing angle dependency by using a liquid crystal display element having two alignment regions in which the rising directions of liquid crystal molecules are different by about 180 degrees in one pixel ( Two Domain Twisted Nemati
c; hereinafter abbreviated as TDTN. This technique is disclosed, for example, in Japanese Patent Laid-Open No. 64-
88520), or a Domain Divided Twisted Nemat that uses a spray array to achieve the same effect as TDTN.
ic (hereinafter abbreviated as DDTN. This is, for example, Y. Koike, et.
al., 1992, SID, p798) method has been proposed. In general, in the electro-optical characteristics of a liquid crystal display element, the transmittance observed obliquely with respect to the rising direction of liquid crystal molecules is smaller than that from the front. In the case of the direction opposite to the rising direction, the transmittance observed obliquely becomes larger than that from the front. Therefore, in the above-mentioned DDTN method, one pixel is divided into two regions having different alignment directions, and the above-mentioned contradictory electro-optical characteristics observed obliquely in each region can be obtained by both alignment characteristics. The visual angle characteristics are combined and added together so as to complement each other so as to approach the electro-optical characteristics observed in the front direction.

However, in the case of manufacturing such a liquid crystal display device of the DDTN system, it is necessary to divide each pixel into regions having two different alignment directions, which makes the manufacturing process extremely complicated. There is a problem. As a result, the manufacturing yield will be significantly reduced.

As a technique similar to the above-mentioned DDTN, a technique called multi-domain has been reported in which a large number of alignment regions in which the orientations of liquid crystal molecules rising from the substrate surface are substantially ununiform are provided in one pixel ('93 Society for Informatio
n Display, Advance program, p.67). According to this multi-domain method, the azimuths in which the liquid crystal molecules rise when voltage is applied are almost random (substantially ununiform). As a result, T
The -V characteristic is almost the same in any direction, and a wide and uniform viewing angle characteristic can be realized.

However, when a large number of alignment regions in which the rising directions of the liquid crystal molecules are made substantially ununiform are provided in one pixel, the display image is colored. Therefore, in the case of performing full-color display in combination with a color filter, there is a problem that an inconvenient coloring different from the color originally intended to appear in the image occurs and the display quality is significantly deteriorated. And this coloring problem becomes particularly remarkable when the twist angle of the liquid crystal molecules is increased.

The present invention has been made to solve such a problem, and an object thereof is to provide a wide and uniform viewing angle characteristic without causing an inconvenient coloring different from the color originally desired to be expressed in an image. It is to provide a liquid crystal display device that can be realized.

[0013]

In order to solve the above problems, a liquid crystal display element of the present invention has an image display electrode, and a substrate surface is subjected to an alignment treatment for aligning the major axis directions of liquid crystal molecules in the same direction. The two substrates, which are formed so as to avoid being squeezed, are opposed to each other with a gap therebetween, and the long-axis direction of the liquid crystal molecules is held in a substantially horizontal posture with respect to the substrate surfaces when no voltage is applied. At the same time, the major axis direction of the liquid crystal molecules is oriented in a substantially non-uniform azimuth direction on the substrate surface while maintaining the substantially horizontal posture, and the liquid crystal is separated by a gap between the two substrates in a direction perpendicular to the substrate surface. A liquid crystal layer sandwiched between the two substrates so that molecules are twisted and aligned.
And a liquid crystal cell that is combined with the first liquid crystal cell in an overlapping manner, and is formed by avoiding alignment treatment for aligning the major axis directions of the liquid crystal molecules in the same direction to be performed on each other. Are opposed to each other with a gap, and the long axis direction of the liquid crystal molecules is kept substantially horizontal with respect to the surface of each of the two substrates. The liquid crystal molecules are oriented in a substantially inhomogeneous direction on the surface of the substrate while maintaining the substantially horizontal posture, and the liquid crystal molecules are separated by the first liquid crystal in the gap between the two substrates in the direction perpendicular to the surface of the substrate. A second liquid crystal cell, which is twisted and arranged in a direction opposite to the twisting direction of the twisted arrangement of the cells and has an optical rotation angle substantially the same as the optical rotation of the first liquid crystal cell and an optical rotation in the opposite direction. It has a feature.

Alternatively, in the above liquid crystal display device,
The first liquid crystal cell is a liquid crystal cell in which a drive voltage is applied to the image display electrode, and light transmittance changes for each pixel in response to the drive voltage to display an image. The liquid crystal cell is a liquid crystal cell that compensates for coloring of light transmitted through the first liquid crystal cell, and the retardation value of the second liquid crystal cell is smaller than the retardation value of the first liquid crystal cell. It is set, and the twist of the liquid crystal molecules of the second liquid crystal cell is almost the same as the twist angle of the liquid crystal molecules of the first liquid crystal cell, and twisted in the opposite twist direction. I am trying.

Alternatively, in the above liquid crystal display device,
A polymer liquid crystal is used as a liquid crystal layer of at least one of the first liquid crystal cell and the second liquid crystal cell.

In order to twist the twist of the liquid crystal molecules of the second liquid crystal cell in the twist direction opposite to the twist of the liquid crystal molecules of the first liquid crystal cell, for example, the liquid crystal layer of the first liquid crystal cell is used. A chiral agent for left twist is mixed in the
The liquid crystal layer of the liquid crystal cell may be mixed with a right-handed chiral agent having an optical rotation angle substantially equal to that of the liquid crystal molecules of the first liquid crystal cell.

The present invention is also applicable to a so-called simple matrix type liquid crystal display device in which strip-shaped transparent electrodes are arranged on each substrate as the image display electrodes, or on one substrate as the image display electrodes. Needless to say, is also applied to a so-called active matrix type liquid crystal display element in which a counter (common) electrode is formed and a pixel electrode is arranged for each pixel on the other substrate.

Further, a horizontal alignment film using, for example, polyimide as an alignment film material is formed on the surface of each substrate of the first liquid crystal cell and the second liquid crystal cell, and subjected to alignment treatment such as rubbing alignment. It may be used without applying it, or it may be used without using the alignment treatment by using another alignment film material. In any case, an alignment film or the like is formed on the substrate surface so that the long axis direction of the liquid crystal molecules can be held in a substantially horizontal posture with respect to the substrate surface when no voltage is applied, and the surface of the alignment film or the like is rubbed. Avoiding orientation processing,
The long axis direction of the liquid crystal molecules may be kept substantially horizontal when no voltage is applied, and the orientation of the long axis of the liquid crystal molecules on the substrate surface may be substantially ununiform within one pixel.

[0019]

The function of applying a voltage is to form the substrate surface so that the liquid crystal molecules maintain a substantially horizontal posture with respect to the substrate surface of the first liquid crystal cell when no voltage is applied, and the major axes of the liquid crystal molecules are not aligned. Occasionally, the rising directions of liquid crystal molecules become random (substantially non-uniform). As a result, the TV characteristics are almost the same in any direction, and wide and uniform viewing angle characteristics can be realized.

At this time, the display image is colored in an inconvenient color different from the color desired to be expressed. Therefore, such coloring of the transmitted light can be compensated by the second liquid crystal cell so that the transmitted light becomes close to white light.

That is, the first which is a multi-domain cell
By arranging a second liquid crystal cell, which is a multi-domain cell in which liquid crystal molecules are twisted and arranged in a direction opposite to the twisting direction of the arrangement of the liquid crystal molecules of the first liquid crystal cell, in the above liquid crystal cell, It is possible to eliminate the coloring of the transmitted light. This is because light having different optical rotation angles for each wavelength transmitted through the first multi-domain liquid crystal cell is further incident on the second multi-domain liquid crystal cell having the reverse twist arrangement. The light transmitted through one liquid crystal cell can be returned to the polarization state before being transmitted through the first liquid crystal cell over all wavelengths of light, and practically almost white light (like black and white display) This is because an uncolored image display can be obtained.

Furthermore, in order to obtain a more preferable color compensation effect, the optical rotatory power of the first liquid crystal cell and the second liquid crystal cell (when light travels through the medium, the plane of polarization is adjusted to the right or left with respect to the traveling direction). It is necessary that the properties of rotating to) are almost equal. In actuality, when a display is performed by time division driving by the voltage averaging method, a voltage of a specific magnitude is applied to the liquid crystal layer in the dark state. The specific magnitude of the voltage varies depending on the relationship between the number of strike lines and the TV characteristic of the liquid crystal cell, but is generally set near the response threshold voltage of the liquid crystal layer. When a voltage of such magnitude is applied to the first liquid crystal cell, its optical rotatory power is somewhat smaller than that when no voltage is applied. Therefore, the optical rotatory power of the second liquid crystal cell for color compensation must be made smaller than that of the first liquid crystal cell when no voltage is applied. Specifically, when the first liquid crystal cell is a liquid crystal cell driven by applying a voltage, the retardation value of the first liquid crystal cell is larger than the retardation value of the second liquid crystal cell, and If the twist angle of the liquid crystal cell and the twist angle of the second liquid crystal cell are set to be substantially equal to each other, coloring of the image can be very effectively eliminated. Furthermore, when one of the first liquid crystal cell and the second liquid crystal cell is made of polymer liquid crystal,
Since the liquid crystal display element can be made thin and lightweight, a more desirable liquid crystal display element can be obtained.

Further, according to the present invention, since a complicated process such as a rubbing alignment process for the alignment film can be omitted,
There is also an advantage that the manufacturing yield can be improved and the manufacturing process can be simplified.

[0024]

Embodiments of the liquid crystal display device according to the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a diagram schematically showing a structure of a main part of a liquid crystal display device according to a first embodiment of the present invention.

The scanning line 1 and the signal line 3 are arranged so as to be substantially orthogonal to each other, and the scanning line 1 and the signal line 3 are arranged at each intersection.
The TFT 7 as a switching element that is connected to the pixel electrode 5 and controls the voltage application to the pixel electrode 5 is provided, and the alignment film 9 that is not subjected to the alignment treatment to cover them is provided. The formed TFT array substrate 11 and the counter substrate 17 on which the counter electrode 13 that is arranged to face the TFT array substrate 11 is formed, and the alignment film 15 that is not subjected to the alignment treatment so as to cover the gap are formed ( Cell substrates), both substrates 11, 1
A liquid crystal layer 19 is enclosed and sandwiched in the gap 7 to form a first liquid crystal cell 21. And this first liquid crystal cell 2
The second liquid crystal cell 23 is assembled so as to be overlaid on the first liquid crystal cell 23. And the first liquid crystal cell 21 which is overlapped
Polarizing plates 25 and 27 are attached to the outer surface side of each liquid crystal cell so as to sandwich the second liquid crystal cell 23 from above and below, and the liquid crystal display element of the first embodiment according to the present invention is formed. The main part is composed.

In the liquid crystal cell 21, as described above, the alignment films 9 and 1 for performing horizontal alignment so as to cover almost the entire surface of the substrate.
No. 5 is formed, the surfaces of these alignment films 9 and 15 are not rubbed, and spacers (not shown) made by Sekisui Fine Chemical Co., Ltd. having a particle size of 5.0 μm are interposed as a gap material between both substrates. The cell gap is maintained at about 5.0 μm, and a sealing material (not shown) is applied to the periphery of the substrate to form both substrates 11 and 17 in combination.

As the liquid crystal layer 19, ZLI-4287 (E.
A liquid crystal composition was used in which a chiral agent S811 for left-handed twist (manufactured by E. Merck) was mixed with (Merck Co., Ltd.) so that the twist of the liquid crystal molecules between the substrates was about 90 degrees. This liquid crystal composition was injected into an empty cell in an isotropic phase state, and a liquid crystal layer 19 was enclosed and sandwiched between the substrates 11 and 17. The retardation value Δnd of the first liquid crystal cell thus formed is
It became about 460 nm. The twist pitch is about 90 degrees as described above.

The second liquid crystal cell 23 has a structure similar to that of the first liquid crystal cell 21, and its retardation value Δnd is about the same as that of the first liquid crystal cell.
The cell gap is set to 460 nm and the cell gap is set to about 5.0 μm as in the first liquid crystal cell. However, no drive voltage is applied, and the liquid crystal layer 33 enclosed and sandwiched between the substrates 29 and 31 is A chiral agent R for right-handed twist so that the twist of liquid crystal molecules between the surfaces of the alignment films 35, 37 of the substrates 29, 31 (cell gap) becomes a right-handed twist at about 90 degrees.
Mixing 811 (manufactured by E. Merck) into ZLI-4287 (manufactured by E. Merck) means that the first liquid crystal cell 21 described above is used.
Is different from.

As the polarizing plates 25 and 27, crossed Nicols polarizing plates (G1220DU, manufactured by Nitto Denko) were used and were arranged so that their light absorption axes were orthogonal to each other.

Although not shown, the first liquid crystal cell 21
A scanning signal voltage and a video signal voltage input from an external liquid crystal drive circuit are supplied to the electrode lead-out portion of the liquid crystal display element to drive the liquid crystal display element.

Here, there are roughly two types of arranging methods of the polarizing plates used in the TN cell. One is a method of arranging the light absorption axes of the upper and lower polarizing plates in parallel with each other.
There is a method of arranging the light absorption axes of the upper and lower polarizing plates at right angles. In the former method, light is not transmitted when a voltage is not applied to the liquid crystal cell, and a light transmission state is obtained when a voltage is applied (normally closed). In the latter method, light is transmitted when a voltage is not applied to the liquid crystal cell, and light is blocked when a voltage is applied (normally open). FIG. 2 is a diagram showing the viewing angle dependence of the contrast ratio when the viewing angle is tilted to the left and right directions up to 60 degrees from the normal to the normally open and normally closed display surface of the conventional TN method. Comparing with, it can be seen that normally closed has less viewing angle dependence of contrast ratio than normally open. The contrast ratio is a value obtained by dividing the luminance in a state where light is transmitted (bright state) by the luminance in a state where light is blocked (dark state), and the contrast ratio greatly affects the luminance in a dark state. Then, when the viewing angle dependency in the left-right direction of the luminance in the dark state of both the normally open type and the normally closed type is measured, the characteristics shown in FIG. 3 are obtained. As is clear from the figure, normally closed has a smaller viewing angle dependence in the dark state than normally open, and as a result, normally closed has a better viewing angle characteristic of contrast ratio than normally open. Considering the difference between the normally open and normally closed dark states, a voltage above the threshold is applied to the liquid crystal layer in the case of normally open, and a threshold voltage is applied to the liquid crystal layer in the case of normally closed. Only the following voltages are applied. When a voltage above the threshold value is applied to the liquid crystal layer, the liquid crystal molecules are aligned in the cell thickness direction and the twisted arrangement is released. In such an array state, the viewing angle change of the appearance of the array is large as compared with the array state in which the voltage is applied below the threshold value and the substrate is twisted substantially horizontally. Therefore, for the above reasons, it has been found that normally closed is better for widening the viewing angle.

On the other hand, as a technique for making the viewing angle uniform over a wide range, there is a technique called a so-called multi-domain system in which a large number of alignment regions in which the rising directions of liquid crystal molecules are substantially ununiform are provided in one pixel. This is because the long axes of the liquid crystal molecules maintain a substantially horizontal posture with respect to the substrate surface when no voltage is applied, and by avoiding alignment treatment, the long axes of the liquid crystal molecules are not aligned. The orientation in which the liquid crystal molecules rise when voltage is applied becomes random, and as a result,
The TV characteristics are almost the same in any direction. As an example, FIGS. 4 and 5 show the TV characteristics in the up and down left azimuth directions at an incident angle of 60 degrees in the case of a conventional normally closed TN cell and the case of a multi-domain cell, respectively. It can be seen that in the multi-domain cell, the TV characteristic has almost no azimuth angle dependence. However, when a multi-domain cell is manufactured under the same cell conditions (retardation value and twist angle (twist angle)) as the conventional TN cell, the display image is colored. Such coloring becomes more remarkable as the twist angle increases.

Therefore, the coloring of such transmitted light is compensated by the second liquid crystal cell 23 so that the transmitted light becomes close to white light. That is, the second liquid crystal which is a multi-domain cell in which the liquid crystal molecules are twisted and arranged in the direction opposite to the twist direction of the arrangement of the liquid crystal molecules of the first liquid crystal cell 21 which is the multi-domain cell. By arranging the cells 23 in an overlapping manner, the coloring of the transmitted light can be eliminated. This is because light having different optical rotation angles for respective wavelengths transmitted through the first multi-domain type liquid crystal cell 21 is further incident on the second multi-domain type liquid crystal cell 23 having an inverse twist arrangement. , The light transmitted through the first liquid crystal cell 21 can be returned to the polarization state before being transmitted through the first liquid crystal cell 21 over all wavelengths, and practically almost white light (like black and white display). This is because an uncolored image display can be obtained.

Further, in order to perform color compensation more effectively, the first liquid crystal cell 21 and the second liquid crystal cell 23 have optical rotatory power (when light propagates in the medium, a plane of polarization is set in the traveling direction. It is necessary that the properties of rotating to the right or left) are almost equal. In practice, when a display is performed by time division driving by the voltage averaging method, a voltage of a specific magnitude is applied to the liquid crystal layer in the dark state. The magnitude of the voltage is
Although it depends on the relationship between the number of scanning lines 1 and the TV characteristic of the first liquid crystal cell 21, it is generally set near the response threshold voltage Vth of the liquid crystal layer 19. When a voltage of such a magnitude is applied to the first liquid crystal cell 21, its optical activity becomes somewhat smaller than that when no voltage is applied. Therefore, the optical activity of the second liquid crystal cell 23 for color compensation is also adjusted to the first
It is necessary to make it smaller than when no voltage is applied to the liquid crystal cell 21. Specifically, when the first liquid crystal cell 21 is a liquid crystal cell driven by applying a voltage, the retardation value of the first liquid crystal cell 21 is larger than the retardation value of the second liquid crystal cell 23, and By setting the twist angle of the first liquid crystal cell 21 and the twist angle of the second liquid crystal cell 23 to be substantially equal to each other, it is possible to extremely effectively eliminate the coloring of the image.

A TFT active matrix type liquid crystal display device having the above-mentioned structure and a screen size of 9.5 inches was manufactured, and a test pattern image was displayed on the liquid crystal display device to verify the image display quality. As a result, it was confirmed that a liquid crystal display device having a wide viewing angle in black and white display can be realized. Further, when the halftone display was performed, it was confirmed that a good display can be realized without causing the display image to be reversed in brightness regardless of the azimuth direction.

(Comparative Example to First Example) First Example
In the liquid crystal display element according to the embodiment, the second liquid crystal cell 23
To remove the polarizing plate 2 using only the first liquid crystal cell 21.
A liquid crystal display device was manufactured in which the absorption axes of Nos. 5 and 27 were arranged in parallel to each other so as to be normally closed, and other settings were the same as those of the first embodiment.

When the liquid crystal display device of such a comparative example was driven under the same driving condition as that of the first embodiment to display an image of the same test pattern, a purple color was obtained when the color filter was not used. The image will be colored in
When full-color display is performed using a color filter, the image display is colored in an inconvenient color different from the color originally desired to be expressed, and the display quality is significantly deteriorated.

Example 2 In the first example, the liquid crystal material used for the first liquid crystal cell 21 and the second liquid crystal cell 23 was changed to ZLI-1132 (manufactured by E. Merck), and In the first liquid crystal cell 21, the concentration of the chiral agent S811 (manufactured by E. Merck & Co., Inc.) was made higher than that in the first embodiment to prepare a left-twisted orientation of about 270 degrees,
In the second liquid crystal cell 23, the concentration of the chiral agent R811 (manufactured by Merck & Co., Inc.) was made higher than that in the second embodiment to prepare a right-handed twisted orientation of about 270 degrees, and the mixture was injected into each liquid crystal cell and sandwiched. Let

As a result, the color of the display image without the color filter was almost black and white, which was confirmed to be suitable for full-color display with the color filter.

Further, the transmittance-applied voltage characteristic is also steeper than that of the first embodiment. As a result, the first liquid crystal cell 21 and the second liquid crystal cell 23, which are set to the above-described twist condition of the liquid crystal molecules, have a simple matrix type liquid crystal cell configuration, and a full-color liquid crystal display using a color filter. It was confirmed that it is possible to perform multi-digit display with excellent viewing angle characteristics, contrast characteristics, and color reproducibility by performing multiplex driving as an element. So, in fact, 6
When a simple matrix type liquid crystal display device with 40 × 480 pixels was manufactured and driven at 1/240 duty in multiplex, a wide viewing angle was obtained compared with the conventional ST type liquid crystal display device, and contrast characteristics and An image display with extremely good color reproducibility could be obtained.

(Embodiment 3) The second liquid crystal cell 23 in the above second embodiment has a liquid crystal layer 33 which is a polymer copolymer liquid crystal having a polysiloxane main chain and a side chain of biphenylbenzoate and a cholesteryl group. A liquid crystal display device was produced in which the liquid crystal cell using the composition was changed. When this liquid crystal display device was driven and the viewing angle characteristics were measured, it was possible to obtain a contrast ratio of 14: 1 or more with a 60 degree cone. Also, when the intermediate gradation is displayed, the incident angle is
It was confirmed that good black-and-white display without display reversal was obtained even at 60 degrees or more. Further, since the liquid crystal cell can be made thin and lightweight by using the liquid crystal composition of such a high molecular weight copolymer, there is also an advantage that a more desirable liquid crystal display device which is thin and lightweight can be obtained. is there.

In the first embodiment, T
The case where the present invention is applied to the FT active matrix type liquid crystal display element has been described, but the application of the present invention is not limited to such a TFT active matrix type liquid crystal display element. Other than this, such as MIM element
It goes without saying that the present invention can also be applied to an active matrix type liquid crystal display element using a two-terminal element and a simple matrix type liquid crystal display element.

In addition, it goes without saying that various changes can be made to the material for forming each part (eg, alignment film material) of the liquid crystal display device of the present invention without departing from the scope of the present invention.

[0045]

As has been clearly described in the detailed description above, according to the present invention, a liquid crystal display which realizes a wide and uniform viewing angle characteristic without causing inconvenient coloring different from the color originally intended to be expressed in an image. An element can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a main part of a liquid crystal display element according to the present invention.

FIG. 2 is a diagram showing a viewing angle characteristic of a normally open and normally closed contrast ratio of a TN cell in the left-right direction.

FIG. 3 is a diagram showing viewing angle characteristics of luminance in a normally open and normally closed dark state of a TN cell in a dark state.

FIG. 4 is a diagram showing the transmittance-applied voltage characteristics of a normally closed TN cell at an incident angle of 60 degrees in the vertical and leftward directions.

FIG. 5 is a diagram showing the transmittance-applied voltage characteristics of a normally closed multi-domain cell at an incident angle of 60 degrees in the upper and lower left directions.

[Explanation of symbols]

 1 ... Scan line 3 ... Signal line 5 ... Pixel electrode 7 ... TFT 9, 15 ... Alignment film 11 ... TFT array substrate 13 ... Counter electrode 17 ... Counter substrate 19, 33 ... Liquid crystal layer 21 ... First liquid crystal cell 23 ... Liquid crystal cell 25, 27 ... Polarizing plates 29, 31 ... Glass substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Hato 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Incorporated company Toshiba Yokohama Office

Claims (3)

[Claims] 1. An electrode for image display, which is formed so as not to be subjected to an alignment treatment for aligning the major axis directions of liquid crystal molecules in the same direction, and is arranged to face each other with a gap. The two substrates, the liquid crystal molecule major axis direction being held substantially horizontally with respect to the substrate surface when no voltage is applied, and the liquid crystal molecule major axis direction being held substantially horizontally. The liquid crystal molecules are oriented in a substantially non-uniform orientation on the surface, and are sandwiched between the two substrates so that the liquid crystal molecules are twisted and aligned in the space between the two substrates in a direction perpendicular to the substrate surface. A first liquid crystal cell having a liquid crystal layer, and a liquid crystal cell that is combined with the first liquid crystal cell in an overlapping manner, wherein the substrate surface is subjected to an alignment treatment for aligning the major axis directions of liquid crystal molecules in the same direction. Formed to avoid each other and have a gap between them and face each other And two substrates are location, the
The major axis direction of the liquid crystal molecules is kept substantially horizontal with respect to the substrate surface of each of the two substrates, and the major axis direction of the liquid crystal molecules is substantially ununiform on the substrate surface while maintaining the substantially horizontal posture. And the liquid crystal molecules are twisted and arranged in a direction opposite to the twisting direction of the twisting arrangement of the first liquid crystal cell in a gap between the two substrates in a direction perpendicular to the substrate surface. A liquid crystal display device comprising: a second liquid crystal cell having an optical rotation angle substantially the same as that of the first liquid crystal cell and having an optical rotation in the opposite direction. 2. The liquid crystal display element according to claim 1, wherein a drive voltage is applied to the image display electrode of the first liquid crystal cell, and the light transmittance of each pixel is corresponding to the drive voltage. A liquid crystal cell that changes to display an image, the second liquid crystal cell is a liquid crystal cell that compensates for coloring of light that has passed through the first liquid crystal cell, and a retardation value of the second liquid crystal cell. Is set to a value smaller than the retardation value of the first liquid crystal cell, and the liquid crystal molecules of the second liquid crystal cell have twist angles substantially the same as those of the liquid crystal molecules of the first liquid crystal cell in opposite directions. A liquid crystal display element characterized by being twisted in the twisting direction. 3. The liquid crystal display device according to claim 1, wherein a polymer liquid crystal composition is used as a liquid crystal layer of at least one of the first liquid crystal cell and the second liquid crystal cell. Liquid crystal display device.