JP2001117088A - Liquid crystal display element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an OCB(optically compensated bend) made type liquid crystal display element having display quality with less illuminated defect caused by thermal fluctuation due to a backlight or the like. SOLUTION: Stress relaxation glue is used in the case respective components of a polarizing plate integrated with an optical retardation plate are stuck together.

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 that can easily improve image quality.

[0002]

2. Description of the Related Art The general principles 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 are described in, for example, "Color TF" supervised by Teruhiko Yamazaki et al.
"T-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 technique described in “Next-Generation Liquid Crystal Display Technology”, Industrial Research Council, 1994, and the like.

[0003] Further, regarding the polymer alignment film and its alignment treatment (especially rubbing treatment), for example, SIGMA 199
It is described in publications in the sixth year, especially in "7" and "8", and in the references listed in the reference list, and furthermore, the material of the cloth used therefor, the specifications of the rollers used, and the like are 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] The following describes the original prior art.

[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 optical compensation 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, the 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 a result, a bend orientation (or a bend orientation including a twist orientation) 52 is induced in the center of the cell as shown on the right side of the figure, and the phase compensators 17 and 18 are driven for low voltage driving and expansion of the viewing angle. It is characterized by being arranged outside the liquid crystal cell.

In terms of performance, the liquid crystal display device of this mode is capable of high-speed response even in a halftone display region and has a wide viewing angle characteristic.

Further, a voltage at which the display becomes black can be adjusted by a phase compensator. Here, the wide viewing angle is due to mutual compensation 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 drive at a lower voltage.

However, the OCB mode liquid crystal 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.

[0018]

By the way, the above-mentioned OC
The B-mode liquid crystal display element is a birefringence mode using a phase compensator, which is described to some extent in the above literature.

In order to optically compensate the birefringence mode, a polarizing plate with a so-called film retardation plate, in which a polarizing plate and a film retardation plate are bonded together, is generally used.

However, in a liquid crystal display device manufactured using a polarizing plate with a film retardation plate, heat unevenness occurs in a backlight lighting portion where the temperature tends to rise, and as a result, light leakage occurs and display quality is deteriorated. Is not preferred because it significantly lowers

For this reason, there has been a demand for the development of a technology which is less likely to cause heat unevenness during use and which can achieve high quality image quality.

[0022]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems.

As will be described in detail later, the present invention relates to a method for manufacturing a polarizing plate, a film retardation plate, etc., which are constituent materials of a polarizing plate with a film retardation plate, wherein a stretching method, a material, and a bonding time of each constituent material are used. In the present invention, it is important that the stretching angle of the film in the stretching direction is different, and furthermore, in these bonded states, it is important that the expansion and contraction of each constituent material due to heat changes the retardation value of the film retardation plate. It is based on

For this reason, the constituent materials of the polarizing plate with a film retardation plate to be bonded to the outer surface of the glass substrate of the liquid crystal display element are as follows:
The liquid crystal display element has a structure in which the layers are laminated using a stress relaxing adhesive. Specifically, the configuration is as follows.

According to the first aspect of the present invention, when bonding the constituent material of the polarizing plate with a film retardation plate used for optical compensation of the liquid crystal display element, a liquid crystal display element using a stress relaxing adhesive is used. It is characterized by pasting.

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.

The stress relaxation adhesive layer absorbs the in-plane stress generated by the thermal expansion and contraction that differs for each constituent material of the polarizing plate with a film retardation plate, and reduces the change in the film retardation value due to a heat source such as a backlight. Thus, a uniform display with less light leakage due to heat unevenness is provided.

According to the second aspect of the present invention, when bonding the constituent material of the polarizing plate with a film retardation plate used for optical compensation of the liquid crystal display element, a liquid crystal display element using a stress relaxing adhesive is used. It is characterized by pasting.

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,
In the production of the liquid crystal display device having the sandwiched liquid crystal region of the splay alignment, the following actions are performed.

The mechanical stress unevenness generated when the polarizing plate with a film retardation plate is bonded to the liquid crystal display element is absorbed by the stress relieving glue layer, and the change in the film retardation value due to a heat source such as a backlight. Uniform display with less light leakage due to heat unevenness is performed.

According to a third aspect of the present invention, when bonding the constituent material of the polarizing plate with a film retardation plate used for optical compensation of the liquid crystal display device, a stress relaxing adhesive is used.

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,
In the production of the liquid crystal display device having the sandwiched liquid crystal region of the splay alignment, the following actions are performed.

The stress relaxation adhesive layer absorbs the mechanical stress unevenness generated when the constituent materials of the polarizing plate with a film retardation plate are bonded, and the change in the film retardation value due to a heat source such as a backlight. And the like, so that a polarizing plate with a film retardation plate having little change in characteristics with respect to thermal and mechanical stress can be obtained.

The invention of claim 4 is characterized in that when laminating a constituent material of a polarizing plate with a film retardation plate used for optical compensation of a liquid crystal display element, a stress relaxing adhesive is used.

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,
In the production of the liquid crystal display device having the sandwiched liquid crystal region of the splay alignment, the following actions are performed.

The stress-relaxing adhesive layer absorbs the mechanical stress unevenness that occurs when the constituent materials of the polarizing plate with a film retardation plate are bonded, and the characteristic change is small with respect to thermal and mechanical stress. Since a polarizing plate with a film retardation plate can be obtained, the production yield is dramatically improved.

[0037]

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

FIG. 1 is a conceptual diagram for explaining the operation and configuration of a liquid crystal display device having a splay-aligned liquid crystal region 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. In an actual display, this state of the bend orientation is used. The liquid crystal display element showing the splay alignment 51 shown on the left side of the figure is in a state not used at the time of manufacture by the manufacturer or by the user. When an initialization voltage is applied to the liquid crystal display element in this state during use, A bend orientation 52 shown on the right side is formed. When the initialization voltage is applied,
Although the director distribution of the liquid crystal in the liquid crystal display element changes from the splay alignment to the bend alignment through a certain process, this conceptual description is general and will not be described.

Reference numeral 55 in FIG. 1 indicates a polarizing plate with a film retardation plate. In this case, a stress relaxation paste 56 is used between the polarizing plate 13 and the phase difference plate 17 and between the phase difference plate 17 and the glass substrate 1.

Since the shrinkage ratios of the polarizing plate and the film retardation plate to heat are basically different, the film retardation plate is affected by the shrinkage of the polarizing plate having a relatively large shrinkage ratio, and retardation in the plane of the retardation plate is caused. Values change easily.

When heat from a backlight or the like is applied to the liquid crystal display element in such a configuration, when a normal non-stress-reducing adhesive is used, the liquid crystal display element is displayed as a change in retardation of the film retardation plate near the backlight. Unevenness occurs, and in a negative type liquid crystal display element, the phenomenon of light dropping is likely to occur.

On the other hand, when the stress relaxation paste is used in the present configuration, the retardation change of the film retardation plate hardly occurs even in the vicinity of the backlight which is a heat source, and as a result, the phenomenon of light leakage due to heat occurs. It becomes difficult to do.

That is, in order to suppress the light leakage, the present invention uses a stress-reducing glue for each constituent material of the polarizing plate with a film retardation plate to be bonded to the glass substrate of the OCB mode liquid crystal display element. It is characterized by using and laminating.

Hereinafter, the present invention will be described based on examples.

(First Embodiment) FIG. 1 conceptually shows a cross-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 (manufacturing) of the liquid crystal display element 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 (solid component 6%) was applied and cured for 1 hour in a thermostat at 180 ° C. to form an alignment film 6. Thereafter, a rubbing treatment is performed for each pixel in the direction shown in FIG. 3 using a rubbing cloth made of rayon, and a spacer and Stractbond XN-21-S (manufactured by Mitsui Toatsu Chemicals, Inc.) are manufactured. (Trade name) was used so that the substrate spacing was 6.5 μm, to produce a liquid crystal cell of this example.

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, and sealed using a sealing resin 352A (manufactured by Nippon Loctite Co., Ltd., made of a UV-curable resin).

Next, the polarization axis forms an angle of 45 ° with the rubbing direction of the alignment film, and a film phase difference plate to be bonded to the polarizing plate is arranged at an arbitrary angle. Using a No. 0 (zero number) stress-reducing glue manufactured by Co., Ltd., a polarizing plate was stuck from above and below such that the directions of the polarizing axes were orthogonal to each other, thereby producing a test cell. This test cell is designated as A.

Incidentally, the structure of the above-mentioned polarizing plate is a well-known technique described in FIG. 1.2 of the “next-generation liquid crystal display technology” described above, and is complicated in FIG. Not.

(Comparative Example) As a comparative example, a test cell R which has the same structure and the same manufacturing method as the first embodiment, but is manufactured by using a normal paste which is not made by stress relaxation is used.

The test cells A and R were set on a backlight using a cold-cathode tube, and two hours after the cold-cathode tube was turned on, light leakage near the cold-cathode tube and the central portion of the backlight were observed. Incidentally, the temperature difference between these portions was 30 ° C. in the central portion and 42 ° C. in the cold cathode tube portion.

Table 1 shows the results of visual observation on the display of the test cells A and R of the example.

[0055]

[Table 1]

As is evident from Table 1, in Comparative Example R, light leakage occurred in a considerably wide range, whereas in Example 1, slight light leakage occurred in the vicinity of the cold cathode tube.

The reason for this is that the heat generated by the operation of the cold cathode tube causes a strain stress due to thermal expansion and contraction between the polarizing plate and the phase difference plate, and changes the retardation value of the film phase difference plate at a portion where the temperature change is large. It is considered that light leakage occurred. On the other hand, when the stress relieving glue is used, the change in the retardation value of the film phase difference plate is reduced, and light leakage is less likely to occur.

Table 2 shows the retardation change rates of the test cells A and R of the embodiment.

[0059]

[Table 2]

As is clear from Table 2, Comparative Example R has a large retardation change rate, which is very consistent with the degree of light leakage due to the difference in paste.

As is clear from the above, the liquid crystal display device of the present invention can achieve high-quality display without sacrificing various characteristics of the conventional OCB mode at all, and its practical value is Extremely large.

As described above, the present invention has been described as an embodiment of the present invention based on the 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 a liquid crystal display device, not only the OCB mode but also a polarizing plate and a film retardation plate are bonded.
A liquid crystal display device of any mode using a so-called retardation plate-integrated polarizing plate may be used. In addition, a liquid crystal display element of any mode may be used regardless of a reflection type or a transmission type.

(2) The polarizing plate integrated with a retardation plate is sufficiently effective even when a plurality of retardation plates are bonded.

(3) There is a sufficient effect on the surface where the liquid crystal display element substrate and the polarizing plate integrated with the retardation plate are bonded.

(4) Since the portion where the distortion due to thermal shrinkage is the largest is between the polarizing plate and the retardation plate, the stress relaxation glue may be used only in this portion.

[0068]

As described above, according to the present invention, a stress-relieving adhesive is applied to each constituent material of a polarizing plate integrated with a retardation plate used in an OCB mode liquid crystal display element. By using this, it is possible to suppress a change in retardation of the retardation plate due to heat of a backlight or the like, and to obtain high-quality image. In addition, even when a polarizing plate integrated with a retardation plate is bonded to a liquid crystal display element, damage to the retardation plate due to mechanical stress can be suppressed, so that image quality can be significantly improved. I can do it.

[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 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 diagram conceptually showing a rubbing direction of a test cell used in a first embodiment of the liquid crystal display device according to the present invention.

[Explanation of symbols]

 Reference Signs List 1,8 Glass substrate 2,7 Bright 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 Plate 17, 18 Phase plate 55 Phase plate integrated polarizing plate 56 Stress relieving glue

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuharu Hattori, 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Tsuyoshi Uemura 1006 Kadoma, Kazuma, Kadoma, Osaka Pref. 72) Inventor Kenji Nakao 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Daiichi Suzuki 1006 Odaka Kadoma Kadoma City, Osaka Prefecture F-term Matsushita Electric Industrial Co., Ltd. FA11X FA11Z FD15 HA09 KA02 LA02 LA04 LA16

Claims (4)

[Claims] 1. A liquid crystal display device having a liquid crystal region of a splay alignment sandwiched between alignment films on electrodes formed on inner surfaces of opposing substrates in parallel with each other, for optical compensation of the liquid crystal display device. A liquid crystal display element characterized in that a stress relaxing adhesive is used when bonding the constituent materials of the polarizing plate with a film retardation plate to be used. 2. A liquid crystal display device having a liquid crystal region of splay alignment sandwiched between alignment films on electrodes formed on inner surfaces of opposing substrates, respectively, in a liquid crystal display device. A method for manufacturing a liquid crystal display element, comprising using a stress relaxing adhesive when laminating a constituent material of a polarizing plate with a film retardation plate to be used. 3. A liquid crystal display device having a liquid crystal region of splay alignment sandwiched between alignment films on electrodes formed on inner surfaces of opposing substrates, respectively, in order to perform optical compensation of the liquid crystal display device. What is claimed is: 1. A polarizing plate with a film retardation plate, characterized in that the property of the polarizing plate is improved by using a stress relieving glue when laminating a constituent material of the polarizing plate with a film retardation plate to be used. 4. A liquid crystal display device having a liquid crystal region of splay alignment sandwiched between alignment films on electrodes formed on opposing inner surfaces of a substrate in parallel with each other, for optical compensation of the liquid crystal display device. The production of a polarizing plate with a film retardation plate, characterized in that, when bonding the constituent materials of the polarizing plate with a film retardation plate to be used, the properties of the polarizing plate are improved by using a stress relaxing adhesive. Method.