JP3185793B2 - Liquid crystal display device - Google Patents

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, and more particularly to an optical compensation bend mode (OCB mode: opt mode).
ically self-compensated b
refringence mode) cell,
The present invention relates to a liquid crystal display device in which spray-bend transition is easy.

[0002]

2. Description of the Related Art The general principle of the principle, structure and manufacturing method of a liquid crystal and a display device using the same as a background of the present invention is described in, for example, "Color TFT" supervised by Teruhiko Yamazaki et al.
"Liquid Crystal Display" Kyoritsu Shuppan Co., Ltd., 1996, Teruo Sasaki et al., 1st edition "All about Liquid Crystal Display" Industrial Research Committee, 1993, Ichiro Nakata et al.
This is a well-known technology described in “Next-generation liquid crystal display technology” published by the Industrial Research Council in 1994.

Further, a polymer alignment film and its alignment treatment (particularly rubbing treatment) are also described in, for example, “Leading Edge of Liquid Crystal Display” edited by Young Researcher of Liquid Crystal, Sigma Publishing 1996.
It is described in annual publications, especially in "7" and "8" and in the references listed in the reference list, and the material of the cloth used therefor and the specifications of the rollers used are also well known techniques. For this reason, a detailed description of these has been omitted,
Only the technologies directly related to the present invention will be described.

As is further shown in the figures, it is well known that a liquid crystal display element has two opposing glass substrates, that a liquid crystal exists between electrodes, that the glass substrate has a rectangular cross section, and the like. For this reason, for example, in the cross-sectional view, to put a horizontal oblique line in the cross-section of the glass substrate, the figure becomes rather complicated,
In addition, since the position of the main part of the invention is more difficult to understand, other parts such as showing a vertically symmetric part in the drawing are omitted in principle.

[0005] Further, the display of parts that are not directly related to the description in the specification will be omitted in principle because the figure is complicated.

[0006] Hereinafter, the original conventional technology will be described.

[0007] The liquid crystal display element is a display which is thinner, lighter and consumes less power than a cathode ray tube or the like.
Image display device. For this reason, it is widely used for display units of office (OA) equipment such as image display devices such as televisions and videos, monitors, word processors and personal computers.

[0008] Conventionally, for example, a twisted nematic (T) using a nematic liquid crystal as a liquid crystal display element is used.
Liquid crystal display devices of the N) mode have been put to practical use, but they have disadvantages such as a low response speed and a narrow viewing angle.

Further, a ferroelectric liquid crystal (FLC) or an antiferroelectric liquid crystal (AFL) having a high response speed and a wide viewing angle is used.
C) and the like, but at present, there are major drawbacks in shock resistance, temperature characteristics, and the like, and they have not yet been put to practical use.

A display mode using a polymer-dispersed liquid crystal utilizing light scattering does not require a polarizing plate and can provide a high-luminance display, but essentially cannot control a viewing angle by a retardation plate. In addition, at present, there is a problem in response characteristics, and therefore, there is little advantage over the TN mode liquid crystal.

On the other hand, an optically compensated bend (OCB) mode has recently been proposed as a display mode having a quick response and a wide viewing angle (Japanese Patent Laid-Open No. 7-84254).

This is shown in FIG.

In FIG. 1, reference numerals 1 and 8 denote glass substrates facing each other. Reference numerals 2 and 7 are transparent electrodes facing each other. Reference numerals 3 and 6 are also alignment films. The liquid crystal layer 4 exists between the alignment films. 13 and 16 are also polarizing plates. 17 and 18 are also phase compensating plates. In this mode, as shown on the left side of the figure, liquid crystal molecules on (between) two opposing substrates are aligned in parallel and in the same direction, and a voltage is applied to the liquid crystal cell in which the splay alignment 51 is formed. As shown on the right side of the figure, a bend orientation (or a bend orientation including a twist orientation) 52 is provided at the center of the cell.
And phase compensation plates 17 and 18 are provided outside the liquid crystal cell for low-voltage driving and widening of the viewing angle. In terms of performance, the liquid crystal display element of this mode is capable of high-speed response even in a halftone display area and has wide viewing angle characteristics.

[0014] A voltage at which the display becomes black is also adjustable by a phase compensator. Here, the wide viewing angle is because the bends near the upper and lower alignment films are in opposite directions as shown on the right side of FIG.

Further, by adjusting the phase compensator, it is possible to achieve a further lower voltage drive.

However, the liquid crystal in the OCB mode is, for example, 33 pages such as the Dempa Shimbun May 25, 1995, a special project "Development of a wide viewing angle and high-speed liquid crystal display", and the 26th Image Optical Conference (1995) P211. 216
"Wide viewing angle, high-speed response display using OCB type liquid crystal", flat panel display, 1994 edition, P
170 "OCB mode capable of wide viewing angle and high-speed response of TFT, key to stabilization of orientation", and others, JP-A-7-8425
No. 4, JP-A-9-96790 and the like. Therefore, further general description will be omitted.

[0017]

By the way, the above-mentioned OC
Although the B-mode liquid crystal display element is described to some extent in the above-mentioned literature, when a user uses a display device adopting this display method, a voltage is applied from the initial splay alignment state every time the display is used. It is indispensable to carry out an initialization process for making a bend orientation.

However, when a voltage of about several volts is applied,
This initialization process requires time in minutes. On the other hand, 2
In order to apply a high voltage of about 0 V, a separate circuit is required, which leads to an increase in the cost of the liquid crystal display element, a reduction in reliability, and an abnormal display, which is not preferable.

For this reason, there has been a demand for an OCB mode liquid crystal display device in which a bend alignment is easily formed by applying a voltage of about several volts and a spray-bend transition speed is high.

In the case of use in a video device such as a television which requires a high quality display, some 1,000,000 pixels may not be transferred for some reason. Leaving the proper pixels as it is may degrade the image quality.

For this reason, there has been a demand for the development of a technique capable of reliably transferring all the pixels when used.

[0022]

Means for Solving the Problems The present invention has been made in view of the above problems.

The present invention will be described in detail later. In the splay-bend transition, the liquid crystal director orientation is perpendicular to the substrate near the center of the liquid crystal layer, and the pretilt angle at one interface of the alignment film is almost zero degree. This is based on the fact that it is important to apply physical excitation to accelerate the transition from the spray state to the bend state.

For this reason, first, a liquid crystal display element having a structure in which a liquid crystal display element is directly excited by a vibrator provided at a terminal portion or the like of the liquid crystal display element.

Second, a liquid crystal display element having a structure in which a liquid crystal display element is indirectly excited by a vibrator provided in a housing of the liquid crystal display element.

The above-mentioned casing means a circuit board, a metal frame, a backlight and the like.

Third, when a vibrator or the like is fixed to a terminal portion or the like of the liquid crystal display element, the liquid crystal display element is formed using a UV-curable resin or a thermosetting resin.

Fourth, an electric circuit for mounting a vibrator that directly excites the liquid crystal display element or the like is a liquid crystal display element formed in advance in a terminal portion.

Fifth, the vibrator itself that directly excites the liquid crystal display element is formed in a terminal portion, in a display pixel, in the vicinity of the display pixel, or in a non-lighting region other than the terminal portion when the TFT array is manufactured. It is a liquid crystal display element.

Specifically, the configuration is as follows.

In the liquid crystal display device according to the first aspect of the present invention , the
Wherein the liquid crystal is a liquid crystal display element having a bend alignment.
And a mechanism for exciting the liquid crystal . According to a second aspect of the present invention, there is provided the liquid crystal display element of the first aspect.
Here, the excitation mechanism may be brought into contact with the substrate.

With the above arrangement, the alignment films on the electrodes respectively formed on the inner surfaces of the opposing substrates are subjected to alignment processing in parallel with each other,
The following operation is performed in the liquid crystal display element having the splay-aligned liquid crystal region sandwiched therebetween.

Since the liquid crystal molecules are oscillated by excitation during the splay-bend transition by applying a voltage for each pixel, the liquid crystal molecules are quickly shifted to the bend alignment during the initialization process.

The liquid crystal display device according to claim 3 is a liquid crystal display device according to claim 1.
In the crystal display element, the excitation mechanism contacts the substrate.
It is characterized by indirect excitation .

With the above structure, the alignment films on the electrodes respectively formed on the inner surfaces of the opposing substrates are subjected to alignment processing in parallel with each other,
The following operation is performed in the liquid crystal display element having the splay-aligned liquid crystal region sandwiched therebetween.

In each pixel, the liquid crystal molecules are oscillated by excitation at the time of the splay-bend transition by applying a voltage, so that the bend alignment is promptly shifted during the initialization process.

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

The liquid crystal display device of the fourth aspect is the liquid crystal display device of the first aspect.
In the crystal display element, the liquid crystal display element is not used for display.
And the excitation mechanism is formed in the non-lighting area.
It is characterized by doing. Claim as in claim 5
In one liquid crystal display device, the vibration frequency of the excitation mechanism is set to 2
It may be 0 kHz or more.

With the above structure, the alignment films on the electrodes respectively formed on the inner surfaces of the opposing substrates are subjected to alignment processing in parallel with each other,
The following operation is performed in the liquid crystal display element having the splay-aligned liquid crystal region sandwiched therebetween.

Since the vibrator is already formed in the non-lighting area except for the terminal portion, the liquid crystal area of the liquid crystal display element can be surely excited, and the transition to the bend alignment is promptly performed during the initialization processing. . Moreover, the electric circuit around the vibrator is simplified and the mounting of the vibrator is reduced.

[0052]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The basics of the present invention will be described below based on its embodiments.

FIG. 2 is a conceptual diagram for explaining the operation and configuration of the liquid crystal display device according to the present invention.

The left side 51 is a liquid crystal molecule showing a splay alignment, and the right side 52 is a liquid crystal molecule showing a bend alignment. Then, in an actual display, the state of the bend orientation is used.

Incidentally, the liquid crystal display device showing the splay alignment 51 shown on the left side of the figure is in a state where it is not used by a manufacturer or by a user, and the liquid crystal display device in this state is initialized when used. When a voltage is applied, a bend orientation 52 shown on the right side is formed.

However, as described above, this is not formed simultaneously with the application of the voltage for initialization.

That is, when an initialization voltage is applied, the director distribution of the liquid crystal in the liquid crystal display element changes from the splay alignment to the bend alignment through the process as described below.

FIG. 3 shows that a typical OCB mode type liquid crystal display element is supplied with a voltage of 0 → V1 → V2 → V3 → V4 → V5 (0 <
V1 <V2 <V3 <V4 <V5) schematically (approximately) showing the difference due to the applied voltage of the movement of the liquid crystal director in the liquid crystal layer when the addition is performed sequentially. is there.

In this case, left and right (in this figure, left and right,
(In actual use, front and back sides) The initial value of the liquid crystal pretilt angle (liquid crystal pretilt angle when no voltage is applied) at the interface between both alignment films is the same.

The details of this change in orientation will be described below with reference to FIG.

FIG. 3A shows the alignment state (spray state) of the liquid crystal when no voltage is applied. In this case, the liquid crystal director at the center of the cell is naturally horizontal to the substrate.

In FIG. 3A to FIG. 15G, marks (outside 1) indicate the thickness direction of the liquid crystal layer in which the liquid crystal director is horizontal to the alignment film (substrate).

[0063]

[Outside 1]

When a voltage V1 equal to or higher than the threshold value is applied to the liquid crystal display element in the state (a), the liquid crystal molecules at the center of the cell, which are most likely to move, are first moved to (b) ), The liquid crystal pretilt angle at the interface of one (left side in the figure) alignment film increases, and the liquid crystal pretilt angle at the interface of the other (right side in the figure) decreases. At this time, the position where the horizontal liquid crystal director exists on the substrate approaches the interface of the low pretilt alignment film.

(C) and (d) are the cases where the voltage is further applied (increased), and the pretilt angle at the interface of the high pretilt alignment film 3 on the left side in the figure is further increased, and the right side in the figure. The pretilt angle at the interface of the low pretilt alignment film 4 is further reduced. The voltage was further increased (d)
In (2), liquid crystal molecules having a director orientation horizontal to the substrate are almost present near the interface of the low pretilt alignment film.

(E) shows the alignment state immediately before the bend transition by the application of the voltage V4, and (f) shows the alignment state at the time of the bend alignment by the application of the voltage V5. In (e), there are liquid crystal molecules having a director orientation parallel to the alignment film, but in (f), no liquid crystal molecules have it.

The liquid crystal display element once in the alignment state (f) is quickly shifted to the alignment state (steady state) shown in (g).

According to the above-described transition mechanism, in order for rapid splay-bend transition to be performed, the liquid crystal director orientation near the center of the liquid crystal layer is perpendicular (orthogonal) to the alignment film (substrate).
And that the pretilt angle at one interface of the alignment film is small. Conversely, this will result in a rapid splay-bend transition.

However, as described above, when a voltage of about several volts is applied, this initialization process requires a time in minutes.

On the other hand, in order to apply a high voltage such as 20 V, a separate circuit is required, which leads to an increase in the cost of the liquid crystal display element, a reduction in reliability, and an abnormal display, which is not preferable.

That is, for this reason, the present invention provides this spray-
In order to cause the bend transition to occur promptly, the present invention is characterized in that a vibrator for exciting an OCB mode liquid crystal display element is provided in a terminal portion, a polarizing plate, a liquid crystal panel, or the like.

[0072]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

(First Embodiment) FIG. 1 conceptually shows a sectional structure of a first embodiment of a liquid crystal display device according to the present invention, and shows a test cell used in an experiment of a spray-bend transition time. It is. In the figure, the same components (members, configurations) as those of the liquid crystal display element shown in FIG. 2 are denoted by the same reference numerals. In addition, 5 is a spacer.

In the production (manufacture) of the liquid crystal display device of this embodiment, first, an alignment film paint SE-74 manufactured by Nissan Chemical Industries, Ltd. is formed on two glass substrates 1 and 8 having transparent electrodes 2 and 7.
92 was applied by a spin coat method and cured for 1 hour in a constant temperature layer at 180 ° C. to form alignment films 3 and 6.

Thereafter, a rubbing process is performed for each pixel in the direction shown in FIG. 4A using a rubbing cloth made of rayon.
Using a spacer manufactured by Sekisui Fine Chemical Co., Ltd. and Struct Bund 352A (trade name of seal resin manufactured by Mitsui Toatsu Chemicals, Inc.) so that the substrate spacing becomes 6.5 μm, a liquid crystal cell of this example is manufactured. did.

At this time, the upper and lower rubbing directions in FIG. 1 were the same for both substrates as shown in FIG.

Next, a liquid crystal MJ96 manufactured by Merck Japan KK
435 was injected into the liquid crystal cell by a vacuum injection method.

Next, a polarizing plate was attached from above and below such that its polarization axis was at an angle of 45 ° with the rubbing direction of the alignment film, and the directions of the polarization axes were orthogonal to each other. This polarizing plate configuration is a well-known technology described in FIG. 1.2 of the “next-generation liquid crystal display technology” described above, and is not shown in this drawing because it is complicated.

Finally, as shown in FIG. 1, an ultrasonic vibrator was fixed to the terminal portion of the test cell using a UV curable resin 352A manufactured by Loctite Japan Co., Ltd. to produce a test cell. This test cell is designated as A.

(Comparative Example) As a comparative example, the test cell R is a liquid crystal display element itself having the same structure and manufacturing method as the first embodiment, but without fixing the ultrasonic vibrator. When a 7 V rectangular wave was applied to these test cells A and R, the time required for all electrode regions to transition from splay alignment to bend alignment was observed. The oscillation frequency of the ultrasonic transducer was 20 KHz, and a voltage was applied to the ultrasonic transducer at the timing of applying a rectangular wave. Table 1 shows the time required for all the electrode regions to transition from the splay alignment to the bend alignment when a 7 V rectangular wave is applied to the test cells A and R of the example.

[0081]

[Table 1]

As is clear from (Table 1), Comparative Example 7
Although the time is seconds, the liquid crystal display device according to the first embodiment of the present invention rapidly changes to less than 1 second.

The reason for this is as shown in FIGS. 3D and 3E.
In this state, the excitation energy for the liquid crystal layer acts to oscillate the liquid crystal molecules as a result, and the liquid crystal director tends to be orthogonal to the test cell substrate surface and the alignment film surface due to the synergistic effect with the electric field. is there. Therefore, the displacement of the liquid crystal director proceeds extremely smoothly, so that a high-speed spray-bend transition is realized.

Table 2 shows the change in transition time when a 5 V rectangular wave was applied in the same voltage application test.

[0085]

[Table 2]

As is clear from (Table 2), Comparative Example 3
It was confirmed that the untransferred state remained in 80 seconds and the transition did not progress even if the liquid crystal display was left for longer than this, whereas the liquid crystal display device according to the first embodiment of the present invention completely transferred in the plane in 20 seconds. Was done. In the same voltage application test, test cell A
Paying attention only to this, Table 3 shows the change in transition time when the frequency of the vibrator is changed and a rectangular wave of 5 V is applied. Further, (Table 3) also shows the results of a test cell B having the same cell configuration as the test cell A and having a different size.
(Area ratio 4A = B)

[0087]

[Table 3]

As is clear from Table 3, it was confirmed that the lower the frequency of the vibrator, the shorter the transition time. However, on the other hand, it was confirmed that the movement of the spacer in the test cell and the accompanying scratches on the alignment film often occurred, resulting in display defects. At 20 KHz or more, it was confirmed that the transition time was slightly longer in the test cell B, and the transition was slower as the distance from the vibrator was larger.

The reason for this is the propagation loss of the excitation energy in the glass substrate. In order to cope with this, a structure having the vibrator at several places in the liquid crystal display element may be used.

From these contents, it is practical that a vibrator combined with the liquid crystal display element of the present invention has a frequency band of 20 KHz or more.

(Second Embodiment) The test cell used in the experiment of the splay-bend transition time of the liquid crystal display element of the present embodiment has the same mechanical structure, structure, cell manufacturing method, and materials used. This is the same as the comparative example of Example 1. As shown in FIG. 5, this liquid crystal display element was modularized with a metal frame, a printed board, rubber for fixing, and the like, and an ultrasonic transducer was fixed to the printed board. This test cell is C.

Comparative Example As a comparative example, the test cell R of the first embodiment was used. These test cells R, C
When a 7 V rectangular wave was applied to (C is specifically a module shape), the time required for all electrode regions to transition from splay alignment to bend alignment was observed. The oscillation frequency of the ultrasonic transducer was 20 KHz, and a voltage was applied to the ultrasonic transducer at the timing of applying a rectangular wave.

Table 4 shows the time required for all the electrode regions to transition from the splay alignment to the bend alignment when a 7 V rectangular wave was applied to the test cells C and R of the example.

[0094]

[Table 4]

As is clear from Table 4, the liquid crystal display device according to the second embodiment of the present invention shifts within 3 to 4 seconds and shows almost half the value of the test cell R of the first embodiment. It was confirmed that the spray-bend transition was accelerated even when the vibrator was fixed to the housing or the like.

As is clear from the above, the liquid crystal display device of the present invention can achieve a high-speed and reliable spray-bend alignment transition without sacrificing the characteristics of the conventional OCB mode at all. , Its practical value is extremely large.

As described above, the present invention has been described as embodiments of the present invention based on some embodiments. However, it goes without saying that the present invention is not limited to the above embodiments.

That is, for example, the following may be performed.

(1) As the liquid crystal display device, not only the OCB mode but also a liquid crystal display element of any mode for accelerating the phase transition of the liquid crystal layer may be used.

(2) The mounting and fixing of the vibrator may be performed not only on the terminal portion or inside the liquid crystal display element but also on the polarized light.

(3) The vibrator and the like are not limited to the ultrasonic vibrator and the like, and a sound source such as a speaker may be used instead.

(4) The frequency band of the vibrator and the like is 20 KH
It is preferable to use z or more, but if a spacer or the like for maintaining a gap disposed between the substrates is fixed to the substrate, or a method that does not cause internal flaws or the like for the movement of the spacer or the like can be secured by an alternative method. Any frequency band may be used.

(5) The method of fixing the vibrator to the liquid crystal display element is as follows: a terminal portion is formed by using a thermosetting resin, a UV curable resin, or the like.
Although it may be fixed directly on a polarizing plate other than the visible region, as described above, a COG mounting pattern is formed on the terminal portion and the like,
The application of a protective resin after mounting the chip type vibrator may be substituted.

(6) The fixing of the vibrator to the terminal portion of the liquid crystal display element can be performed by a method other than the method of mounting chip components or the like.
When manufacturing the array, the vibrator itself may be formed in a terminal portion, in an actual display pixel, in the vicinity of a display pixel, or in a non-lighting region other than the visible region. When formed inside a liquid crystal display element, the formation of a vibrator in a display pixel may cause a decrease in aperture ratio or the like. Preferably, it is formed.

[0105]

As described above, according to the present invention, the splay-bend transition easily occurs even when a relatively low voltage is applied by applying a physical vibration to the OCB mode liquid crystal display element. Become.

Further, since the phase transition by the normal voltage application can be performed reliably and quickly, the image quality can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram conceptually showing a cross-sectional configuration of a test cell used in a first embodiment and a second embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a conceptual diagram for explaining a splay-bend transition caused by application of an initialization voltage in an OCB mode liquid crystal display device.

FIG. 3 is a conceptual diagram for explaining the movement of a liquid crystal director from a splay alignment to a bend alignment in an OCB mode liquid crystal display device.

FIG. 4 is a diagram showing a rubbing direction and a state as an alignment treatment for an alignment film on a substrate in a first embodiment and a second embodiment of the liquid crystal display device according to the present invention.

FIG. 5 is a view conceptually showing a cross-sectional view of a test cell (module form) of a liquid crystal display device according to a second embodiment of the present invention.

[Explanation of symbols]

 1,8 Glass substrate 2,7 Transparent electrode 3,6 Alignment film 4 Liquid crystal layer 5 Spacer 51 Liquid crystal alignment when no voltage is applied (spray alignment) 52 Liquid crystal alignment when voltage is applied (bend configuration) 9 Test cell 13,16 Polarized light Plates 17, 18 Phase compensator 19 Metal frame 20 Printed circuit board 21 Fixing rubber 22 Backlight 53 Vibrator

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-84254 (JP, A) JP-A-60-247622 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/139 G02F 1/1333

Claims (5)

(57) [Claims] A liquid crystal is provided between substrates, and the liquid crystal has a bend arrangement.
A liquid crystal display element, and a device for exciting the liquid crystal.
A liquid crystal display device having a structure . 2. The method according to claim 1 , wherein said excitation mechanism contacts said substrate.
2. The liquid crystal display device according to claim 1, wherein: 3. The indirect excitation without contacting the excitation mechanism with the substrate.
The liquid crystal display device according to claim 1, wherein the liquid crystal device is vibrated . 4. The liquid crystal display element is not lit for display.
Having an area and forming the excitation mechanism in a non-lighting area
The liquid crystal display device according to claim 1, wherein: 5. When the vibration frequency of the excitation mechanism is 20 kHz or more,
The liquid crystal display element according to claim 1, wherein the wherein there.