JPH04186222A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain superior display quality by carrying out masking on a non-display area in the peripheral part of the display surface of a liquid crystal panel. CONSTITUTION:The outside surface of an upper glass substrate 12 is covered with a non-display area 7, and epoxy-related resin 8 is also printed on a display area so as not to bulge out from its range, and this resin 8 is dried up, and re-orientation of liquid crystal is also carried out. An epoxy-related resin layer (masking) 8 formed in this way has the layer thickness of 70mum and light shading ratio 81% (transmission factor 19%). Afterwards, TAB mounting is carried out on a liquid crystal driving circuit, and two sheets of polarizing plates 2 and 4, a sheet of protective glass plate 1, a single back light unit 5, a liquid crystal driving circuit 10 for scanning and a liquid crystal driving circuit 11 for driving a segment are combined together so as to complete a liquid crystal display device. Thereby, notwithstanding a frame display driving electronic circuit is not provided, by means of working of the masking 8, a domain where a bright condition and a dark condition are supposed to exist mixedly in the non-driving non-display area 7 is covered, so that a white display frame having superior display quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device using a strongly electrostatic liquid crystal having memory properties.

[Prior art] Clark and Lagerwall have developed an Applied Phys.
icsLetters Vol. 36, No. 11 (published June 1, 1980), p. 899-901, U.S. Patent No. 436
No. 7924 and U.S. Pat. No. 4,563,059, surface-stabilized ferroelectric liquid crystals
izedferroelectric 1iquid
We have revealed a bistable ferroelectric liquid crystal device based on crystal. This bistable ferroelectric liquid crystal device has a liquid crystal arranged between a pair of substrates with a spacing sufficiently small to suppress the formation of a helical alignment structure of liquid crystal molecules in the chiral smectic phase in the bulk state, and a plurality of liquid crystals. This was achieved by aligning vertical molecular layers of liquid crystal molecules in one direction.

A liquid crystal display device equipped with a display panel formed from such a strong-conductivity liquid crystal element is disclosed, for example, in U.S. Pat. No. 4,655 by Kannabe et al.
An image can be formed on a display screen with large-capacity pixels by using the multiplexing drive method described in, for example, Japanese Patent Application Publication No. 561. The above-mentioned liquid crystal display device can be used as a display screen for word processors, personal computers, micro printers, televisions, etc., but for this purpose, the liquid crystal panel must be built into the housing and the liquid crystal panel It is necessary to fix the periphery with a frame-shaped fixing member and use the inside of the frame as a display screen.

Generally, a liquid crystal panel uses a pair of thin glasses facing each other, and it is difficult to curve the liquid crystal panel itself like a CRT display screen, resulting in a flat display screen.

For this reason, when the liquid crystal panel is incorporated into the housing, the edge area of the flat liquid crystal display screen is hidden by the convex part of the frame-shaped fixing member mentioned above, and especially the upper part of the display screen from the normal viewing direction. There was also the problem that the displayed image in the lower end area could only be viewed.

Therefore, it is necessary to provide a non-display area in which no display image is formed over the edge area of the liquid crystal display panel with a width of several mm to several cm.

By the way, the above-mentioned strong-conductivity liquid crystal element at the time of initial orientation is
In the absence of an electric field, domains that produce a bright state and domains that produce a dark state coexist, and depending on the polarity of the applied voltage, the domain produces either a bright state or a dark state. Ru. The alignment state of the strongly electrostatic liquid crystal in the non-display area mentioned above is maintained at the initial alignment state or as it is, so domains that produce bright and dark states coexist, which causes display quality to deteriorate. There was a problem that the value decreased.

In order to solve this problem, in the conventional technology, electrodes similar to those in the display area are provided in the non-display area so that the non-display area is in either a bright state or a dark state. Frame display driving was performed by outputting voltage to the electrodes.

[Problems to be Solved by the Invention] However, when performing the frame display drive described above, the following problems occur.

■When placing a pair of substrates facing each other, there may be a difference between the distance between some electrodes at the periphery of the substrate and the distance between the electrodes at the center of the substrate due to manufacturing process defects such as variations in the amount of adhesive. There are cases where this occurs.

Differences in the distance between the electrodes appear as differences in the liquid crystal driving conditions, so even if frame display driving is performed, the non-display area, which is the edge area of the display screen, cannot be controlled to a bright or dark state.
A mixed domain of bright and dark states may occur.

(2) To drive a frame display, a dedicated τ circuit is required, which increases the capacity and weight of the entire liquid crystal device, and the advantage of the liquid crystal device, which is its light weight and thinness, is lost.

■The manufacturing cost increases due to the electronic circuit for driving the frame display.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to realize an inexpensive, compact liquid crystal device with high display quality.

[Means for Solving the Problems] The liquid crystal display device of the present invention is a liquid crystal panel formed by disposing a pair of substrates on which transparent electrodes are formed and sandwiching a bistable ferroelectric liquid crystal therebetween. In a liquid crystal display device comprising a liquid crystal panel in which at least one of the pair of substrates is formed with an alignment film and has a non-display area in the peripheral area of the display surface, the non-display area is masked. It is a feature.

It is preferable that such masking has a light shielding rate of 70% or more.

This masking can be performed on one surface of at least one of the pair of substrates.

Furthermore, when the liquid crystal display device includes a pair of polarizing plates arranged with the liquid crystal panel in between, the masking can be performed on at least one of these polarizing plates.

Further, when the liquid crystal display device includes a backlight unit for uniformly illuminating the entire surface of the liquid crystal panel from the rear surface, the masking can be performed on the backlight unit.

Furthermore, when the liquid crystal display device includes a protective plate placed in front of the liquid crystal panel, the masking can be applied on at least one of the front and back sides of the protective plate.

[Operations] According to the present invention, a non-display area provided around the display screen of a liquid crystal panel is masked to prevent light from passing through this non-display area. Therefore, even if a mixed domain exists in a non-display area, the display content of this non-display area is no longer visible, and display quality is not adversely affected even if frame display driving is not performed. Therefore, all of the problems of the prior art described above can be solved.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, in this example, the ferroelectric liquid crystal material is as follows:
A liquid crystal consisting of the following two components was used.

Liquid crystal material component ratio (approx.) /18
' 47.4° 60.8° 7°, 3°mB Example 1 An experiment was conducted using a ferroelectric liquid crystal material having the structure shown in FIG. In the figure, 1 is a protective glass plate, 2
3 is an upper polarizing plate, 3 is a liquid crystal panel, 4 is a lower polarizing plate, and 5 is a backlight unit.

The liquid crystal panel 3 has a layered structure when viewed in a cross-sectional view, and consists of a glass substrate/transparent electrode/polyimide film/liquid crystal/polyimide film/transparent electrode/glass substrate. The transparent electrode is made of indium-sin-oxide (ITO) at 1000%
A striped transparent electrode having a width of 80 μm and a pitch of 100 μm was formed by photoetching. In the upper and lower glass substrates 12 and 12, the striped transparent electrodes were orthogonally crossed to form a matrix structure consisting of a matrix electrode group. The polyimide alignment film was formed by forming a polyimide forming liquid to a layer thickness of 70 mm, and after baking, was subjected to a rubbing treatment using a terene cloth.

The liquid crystal layer thickness is 2. 2 to keep it uniform with OAtm.
．． Spread 0 μm alumina spacers on the substrate and
The two substrates were bonded together using adhesive 6, and liquid crystal was injected.

After that, epoxy resin (Selicol PS-611 manufactured by Teikoku Ink, mixing ratio 8.2 white) is applied to the outer (upper) surface of the upper glass substrate 12 to cover the non-display area 7 and not to protrude into the display area 9. Printed. The method for printing the epoxy resin on the non-display area 7 was to protect the display area 9 with polyimide tape and then screen print with nylon 200 mesh. The epoxy resin was left in an atmosphere at 80° C. for 30 minutes to dry. Thereafter, by slowly lowering the temperature to room temperature, the reorientation of the liquid crystal was also completed at the same time.

The formed epoxy resin layer (masking) 8 has a layer thickness of 7
At 0μ, the light shielding rate was 81% (transmittance 19%).

After that, the liquid crystal drive circuit was TAB mounted, and the two polarizing plates 2.4, one protective glass plate 1, one backlight unit 5, the liquid crystal drive circuit (for row scanning) IO, and the liquid crystal drive circuit ( (for segment drive) 11 to complete a liquid crystal display device.

When this liquid crystal display device was driven, although it did not have a frame display drive electronic circuit, due to the epoxy resin masking 8, the bright and dark states that should exist in the non-display area 7 that was not driven were The mixed domains were covered and a high quality display with a white display frame could be obtained.

Example 2 In Example 1, screen printing of epoxy resin was applied not to the outer surface of the glass substrate 12 but to the upper polarizing plate 2 as shown in FIG. A liquid crystal display device was completed in the same manner as in Example 1, except that conventional reorientation (after being left at 80° C. for 20 minutes, the temperature was gradually lowered to room temperature) was carried out.

When this liquid crystal display device was driven, it was possible to obtain the same good display quality as in Example 1.

Example 3 The screen printing of the epoxy resin in Example 1 was performed not on the outer surface of the glass substrate 12 but on the diffusion plate 5a of the backlight unit 5 as shown in FIG. , main agent ER-111, curing agent ER-
All configurations were the same as in Example 1 except that 176) was used. However, resin drying only applies to the backlight unit.
The liquid crystal panel 3 was left to stand in an atmosphere at 0°C for 2 hours, and the liquid crystal panel 3 was reoriented as usual by leaving it at 80°C for 20 minutes and then gradually lowering the temperature to room temperature. The formed epoxy resin had a layer thickness of 70 μm and a light shielding rate of 94% (transmittance of 6%).

When this liquid crystal display device was driven, although it did not have a frame display drive electronic circuit, the backlight light did not pass through to the non-display area 7 that was not driven due to the epoxy resin masking 8. It was possible to obtain high quality display with a black display frame.

Example 4 In Example 1, epoxy resin screen printing was performed not on the outer surface of the glass substrate 12 but on the back surface of the protective glass plate 1 as shown in FIG. A liquid crystal display device was completed in the same manner as in Comparative Example 1, except that the liquid crystal panel 3 was left in an atmosphere at 80°C for 30 minutes, and the liquid crystal panel 3 was reoriented as usual at 80°C for 20 minutes, and then the temperature was gradually lowered to room temperature. I let it happen.

When this liquid crystal display device was driven, it was possible to obtain the same good display quality as in Example 1.

Comparative Example 1 In Example 1, the screen printing of the epoxy resin on the non-display area 7 was stopped, and the conventional frame display drive circuit was used.
The non-display section 7 was driven to a bright state.

Compared to Examples 1 to 4, this liquid crystal display device is not only larger and more expensive due to the frame display drive circuit, but also has a mixed domain of bright and dark states in a part of the non-display area 7. It was done. This is because, despite spraying 20 μm alumina spacers, the thickness of the liquid crystal layer in a part of the peripheral area of the liquid crystal panel is thicker than that in the center due to variations in the amount of adhesive 6 when bonding the two substrates together. This is probably because it has grown larger.

[Effects of the Invention] As explained above, the strong electroconductive liquid crystal display device of the present invention provides the following effects.

■High-quality display quality is achieved by masking the mixed domain of bright and dark states that may occur in the non-display area around the LCD panel due to defects in the manufacturing process that could not be avoided with conventional frame drive technology. can be obtained.

■As is clear from a comparison between FIG. 5 (liquid crystal display system using the liquid crystal display device of the present invention) and FIG. 6 (conventional liquid crystal display system), the conventional frame display drive circuit 21 can be abolished. , it is possible to reduce the weight and size of the entire liquid crystal display device.

(2) Furthermore, since the frame display drive circuit 21 can be eliminated, the manufacturing cost of the liquid crystal display device can be reduced.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the configuration of a liquid crystal display element according to Example 1 of the present invention, FIG. 2 is an explanatory diagram showing the configuration of a liquid crystal display element according to Example 2 of the present invention, and FIG. , FIG. 4 is an explanatory diagram showing the configuration of a liquid crystal display element according to Example 4 of the present invention, and FIG. 5 is an explanatory diagram showing the configuration of a liquid crystal display element according to Example 4 of the present invention. A block diagram of the liquid crystal display system after eliminating the frame display drive electronic circuit in the embodiment,
FIG. 6 is a block diagram of a conventional liquid crystal display system that employs a frame display drive electronic circuit (frame drive unit). 1: Protective glass plate 2, upper polarizing plate 3 Night crystal panel 4: Lower polarizing plate 5 Backlight unit 5a, diffusion plate 6: Adhesive layer 7: Non-display area 8: Masking (epoxy resin layer) 9 : Display area 10: Liquid crystal drive circuit (for common row drive) 11: Liquid crystal drive circuit (for segment drive) 12. Glass substrate. Patent Applicant Canon Co., Ltd. Agent Patent Attorney Tetsuya Ito Agent Patent Attorney Tatsuo Ito

Claims (6)

[Claims] (1) A liquid crystal panel consisting of a pair of substrates on which transparent electrodes are formed, at least one of which has an alignment film formed thereon, which are placed facing each other, and a bistable ferroelectric liquid crystal is sandwiched therein. What is claimed is: 1. A liquid crystal display device comprising: a non-display area in a periphery of a display surface of the liquid crystal panel, wherein the non-display area is masked. (2) The liquid crystal display device according to claim 1, wherein the masking has a light shielding rate of 70% or more. (3) The liquid crystal display device according to claim 1, wherein the masking is performed on one surface of at least one of the pair of substrates. (4) The liquid crystal display device according to claim 1, further comprising a pair of polarizing plates arranged with the liquid crystal panel sandwiched therebetween, and the masking is performed on at least one of the pair of polarizing plates. . (5) A backlight unit for uniformly illuminating the entire surface of the liquid crystal panel from the back side, and the masking
2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is provided on the backlight unit. (6) The liquid crystal display device according to claim 1, further comprising a protective plate disposed in front of the liquid crystal panel, and the masking is applied on at least one of the front and back sides of the protective plate.