JPH02221928A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To uniformize the brightness at a no-picture-element part and to obtain bistable memory effect at a picture-element part by making the conditions of rubbing processing greatly different at the no-picture-element part and also setting nearly the same conditions at the picture-element part. CONSTITUTION:Substrates 10 and 11 have transparent electrodes 2a and 2b arrayed on glass substrates 1a and 1b in parallel stripes and orienting films 4a and 4b are formed thereupon across insulating films 3. The no-picture-element part of the substrate 10 is rubbed under the constant conditions after being covered with a resist layer, and then the resist layer is removed. The entire surface of the orienting film of the substrate 11 is rubbed, the substrates are arranged so that their orienting films face each other and the stripes of the transparent electrodes cross each other at right angles, and an SmC liquid crystal layer 5 is interposed to obtain a liquid crystal display element. This is sandwiched between two polarizing elements to obtain the multiplex driving type liquid crystal display device which has picture elements arranged in a matrix.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal display device using ferroelectric liquid crystal.

Among conventional liquid crystals, chiral smectic C-phase liquid crystals (hereinafter abbreviated as SmC liquid crystals) have a helical structure and exhibit ferroelectricity.

When this SmC liquid crystal is injected into a cell with a thin gap, the helical structure of the SmC liquid crystal is unraveled under the influence of the interface, and the liquid crystal molecules are tilted at an angle θ with respect to the normal to the smectic layer.
There is a coexistence of a region where the liquid crystal molecules are stabilized by tilting by an angle of −θ and a region where the liquid crystal molecules are stable by tilting in the opposite direction by a tilt angle of −θ.

By applying a voltage to the Srn C liquid crystal in this cell, the orientation of the liquid crystal molecules and their spontaneous polarization can be uniformly aligned, and by switching the polarity of the applied voltage, the orientation of the liquid crystal molecules can be kept constant. This enables switching drive to switch from one state to another constant state.

With this switching drive, the birefringent light changes in the SmC liquid crystal within the cell, so by sandwiching the cell between two polarizers, the transmitted light can be controlled. Furthermore, even if the voltage application is stopped, the orientation of the liquid crystal molecules is maintained in the state before the voltage application was stopped due to the alignment regulating force of the interface, so that a memory effect can also be obtained.

Therefore, attempts have been made in the past to utilize the memory effect of SmC liquid crystal to construct a high-duty liquid crystal display element using a multibrake 7x drive system as shown in a vertical cross-sectional view in FIG.

In the liquid crystal display element shown in FIG. 3, transparent electrodes 2a are provided on the opposing surfaces of two glass substrates 1a and lb arranged parallel to each other.

A plurality of transparent electrodes 2b are arranged parallel to each other in a stripe shape, and the transparent electrode 2a on one glass substrate 1a,
The transparent electrodes 2b on the other glass substrate 1b are arranged perpendicular to each other. On the surface of each glass substrate 1a, lb on the side where transparent electrodes 2zt, 2b are formed, alignment Jl 14a, 4b is further formed, respectively, via an insulating film 3, and an SmC liquid crystal layer 5 is interposed between these two glass substrates la lb. It's a shame.

In this liquid crystal display device, the orientation angle of liquid crystal molecules is
In order to obtain a good memory effect between the state where . In other words, for example, the glass substrate 1afl
When an alignment regulating force that attracts liquid crystal molecules is set at tl, an alignment regulating force that attracts liquid crystal molecules to the same extent as the above alignment regulating force must be set for the other glass substrate 1bllln.

Such alignment regulating force depends on the rubbing conditions of the alignments 1114a and 4b, so in order to satisfy the above conditions, in a conventional liquid crystal display device, one glass substrate 1a
A method in which the entire alignment film 4a of the ltll is subjected to a rubbing process of a constant Pl-, while the entire oriented H4b of the other glass substrate 1bll is also subjected to a rubbing process under the same or almost the same conditions as the above-mentioned rubbing process. was taken.

Problems to be Solved by the Invention However, as in the case of the conventional liquid crystal display device described above, the entire alignment film 4a on one glass substrate 1a side is subjected to a rubbing treatment under certain conditions, and the other glass substrate l
Simply performing a rubbing process on the entire alignment film 4b on the b side under certain conditions to reduce the asymmetry in alignment with the glass substrate 1a will result in a non-pixel area where no voltage is applied (transparent electrodes 4a and 4b do not intersect). There is a coexistence of regions where the orientation angle of liquid crystal molecules is +θ and regions where the orientation angle is -θ, and there is a problem in that the brightness of non-picture element areas is not uniform and the display quality is degraded.

Therefore, an object of the present invention is to provide a 21-crystal display device with uniform brightness in non-picture element areas and a good bistable memory effect.

Means for Solving the Problems The present invention provides a pair of transparent electrode insulating substrates each having a transparent electrode selectively formed on one surface and an alignment film formed thereon, arranged so that the alignment films face each other. In addition, in a liquid crystal display device in which a ferroelectric liquid crystal layer is interposed between these transparent insulating substrates, and the ferroelectric liquid crystal layer is driven by selectively applying a voltage to the transparent electrodes, a pair of Among the alignment films of the transparent insulating substrates, the pixel parts where the transparent electrodes of the pair of transparent insulating substrates intersect are subjected to rubbing treatment under the same conditions or under conditions with a small difference. This liquid crystal display device is characterized in that non-picture element areas where transparent electrodes of an insulating substrate do not intersect with each other are subjected to rubbing treatment under conditions that are significantly different from each other.

According to the present invention, in a non-pixel area where the transparent electrodes of a pair of transparent insulating substrates do not cross each other, a rubbing treatment is applied to the alignment film on one transparent insulating substrate side and a rubbing process is applied to the alignment film on the other transparent insulating substrate side. Since the conditions differ greatly between the rubbing process,
The asymmetry of alignment becomes large in the non-picture element part, and the alignment state of the liquid crystal molecules in this part is aligned in one state. Also,
In the pixel area where the transparent electrodes of a pair of transparent insulating substrates cross each other, the rubbing treatment for the alignment films of both transparent insulating substrates is performed under the same or nearly the same conditions, so there is no alignment asymmetry in the pixel area. becomes small, and a good memory effect can be obtained in this part.

Embodiment FIG. 1 is a longitudinal cross-sectional view showing the manufacturing process of a multiplex drive type liquid crystal display device, which is a first embodiment of the present invention.

This liquid crystal display device is a liquid crystal display device that uses SmC liquid crystal exhibiting ferroelectricity and has a memory effect.
As shown in 4.), a plurality of transparent electrodes 2a are first arranged in stripes parallel to each other on one glass substrate la, and then 4. : The insulating film 3 is formed by applying SiO* (OCD'rypE-II, manufactured by Tokyo Ohka Co., Ltd.) using a spinner and baking it. Furthermore, an orientation 1114a is formed on this insulating film 3 by applying nylon (manufactured by Toshi Co., Ltd., 1% metacresol solution) with a spinner and baking it.

Next, as shown in FIG. 1(b), a metal mask 6 having a thickness of 100 μm and having a shape corresponding to the pixel pattern is provided on the alignment film 4a, and a photoresist 7 is coated with a spinner and blotted at 90°C. After baking, by removing the metal mask 6, a resist layer 8 having a thickness of 1 μm is formed in the non-picture element portion as shown in FIG. 1(C).

Thereafter, a rubbing process is performed on the orientation 114a in a certain direction P under certain conditions as shown in FIG. 1(d). The rubbing condition in this case is, for example, a rotation speed of 400 r of the roller for the rubbing process.

11 m, pressure 105 g/cm''.

After the above-mentioned rubbing process, the resist layer 8 is removed by cleaning with ethyl cellosolve acetate as shown in FIG. 1(e).

The substrate 10 thus formed is incorporated as one substrate of a liquid crystal display element shown in FIG.

On the other hand, the other substrate 11 shown in FIG. 3 is also formed by arranging a plurality of transparent electrodes 2b in stripes parallel to each other on a glass substrate lb, and insulating lI!
3 and an alignment film 4b formed therebetween. After this substrate 11 is subjected to a rubbing treatment on the entire surface of its orientation 114b, the alignment films 4a and 4b of the other substrate 10 are faced to each other, and the transparent electrodes 2a and 2b are perpendicular to each other by 2.0 μm. The SmC liquid crystal layer 5 is interposed between these substrates 10 and 11 with an interval of .

For the alignment film 4b of the substrate 11, the other substrate 10
The rubbing conditions are substantially the same as those for the rubbing treatment for the orientation 1114a. That is, the rubbing direction is the same as or opposite to the direction P for the alignment film 4a, the number of rotations of the roller is 400 r, p, m, and the pressure is 105.
g/cm” condition.

By sandwiching the liquid crystal display element thus obtained between two polarizers, a multiplex drive type liquid crystal display device in which picture elements are arranged in a matrix is constructed.

In this liquid crystal display device, the non-pixel portion of the alignment film 4a of one substrate 10 is not subjected to rubbing treatment, while the other portions with the same orientation r144a and the alignment film 4b of the other substrate 11 are not subjected to rubbing treatment. The entire surface of the board is rubbed under almost the same conditions, so in the non-pixel area, the pair of substrates to,
The asymmetry of alignment increases between t1, and therefore the degree alignment angle of the liquid crystal molecules in the non-picture element area is aligned to either θ or -θ, and the brightness in that area becomes uniform.

In addition, since the asymmetry of alignment is small in the picture element part where the transparent types 4f+2a and 2b of the substrate 10.11 are orthogonal to each other, by selectively switching the polarity of the voltage applied to this picture element part, the alignment of the liquid crystal molecules can be adjusted. A good bistable memory effect that can be switched between a state where the angle is θ and a state where the angle is −θ can be obtained.

Next, the configuration of a liquid crystal display device according to a second embodiment of the present invention will be described.

In the case of this liquid crystal display device, in the previous embodiment, the substrate 1 shown in FIG.
0, the non-picture element portion of the alignment film 4a is subjected to rubbing treatment under conditions different from those for the picture element portion. That is, using a mask having the opposite shape to the metal mask 6 in FIG. 1(b) (a pattern that covers the non-picture element part and releases the picture element part),
A resist layer is formed on the picture element part of the alignment film 4a by the same steps as shown in FIGS. 4(b) and 4(c), and the above-mentioned rubbing process is performed on the non-picture element part. As conditions different from the rubbing process for the picture element part, this rubbing process for the non-picture element part is performed at a roller rotation speed of 800 r, p, m, and a pressure of 200.
It is carried out under the conditions of g / cm 2. The rubbing treatment for the alignment film 4b of the other substrate 11 and other conditions are the same as in the first embodiment.

In this liquid crystal display device, the non-pixel portions of the alignment film 4a of the substrate 10 are not subjected to rubbing treatment as in the first embodiment, but the pixel portions of the alignment film 4a and the other substrate are not rubbed. Since the rubbing process is performed on the alignment film 4b of No. 11 so as to have an asymmetrical alignment characteristic, not only the brightness of the non-pixel area becomes uniform, but also the brightness level is also the same as that of the first implementation. The level is darker than the example. The fact that a good bistable level effect can be obtained in the picture element portion is the same as in the first embodiment.

FIG. 2 is a longitudinal sectional view showing the manufacturing process of a liquid crystal display device according to a third embodiment of the present invention.

In this embodiment as well, the structure of the liquid crystal element is as shown in FIG. 3, similar to the first and second embodiments, but the rubbing process for orientation M4a of the substrate 10 is different here.

That is, in this embodiment, after the transparent electrode 2a, the insulating film 3, and the alignment film 4a are formed on one glass substrate la, the alignment film 4a is formed in a certain direction over the entire surface of the alignment film 4a as shown in FIG. P and certain conditions (roller rotation speed 400r,
Rubbing treatment is performed at a pressure of 100 g/cm2).

Next, as shown in FIG. 2(b), the non-picture element part of the alignment film 4a is released, and a resist JIW9 having a pattern covering the picture element part is formed. The conditions were different from the rubbing process in the process shown in Figure 2 (a) (roller rotation speed 800 r, p, m, pressure 200 g/c).
The rubbing process is performed on the alignment film 4b of the other substrate 11 as shown in FIG. .

In the case of this liquid crystal display device, as in the second embodiment, the non-picture element portion of the orientation 1!4a of the substrate IO is asymmetrical with respect to the pixel portion of the same alignment film 4a and the alignment film 4b of the other substrate 11. Since the rubbing process is performed so that the orientation characteristics are uniform, the brightness of the non-pixel area is not only uniform, but also the brightness level is the same as in the second embodiment. It becomes a dark level.

As in the first and second embodiments, a good bidirectional stable memory effect can be obtained in the picture element portion.

Effects of the Invention As described above, according to the liquid crystal display device of the present invention, the conditions of the rubbing treatment are greatly different in the non-pixel areas between the alignment films of a pair of opposing transparent insulating substrates, while the rubbing conditions in the pixel areas are significantly different. Since the rubbing process was configured to be performed under the same conditions or under conditions with a small difference from each other, the asymmetry of the alignment regulating force between the pair of opposing transparent insulating substrates becomes large in the non-pixel area, causing the alignment of liquid crystal molecules to increase. are uniformly aligned, the brightness in this area is uniform, and the asymmetry of the alignment regulating force is reduced between a pair of opposing transparent insulating substrates in the pixel area, resulting in a bistable memory effect. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing the manufacturing process of a liquid crystal display device according to the first embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view showing the manufacturing process of a liquid crystal display device according to the third embodiment of the present invention. 3 are longitudinal cross-sectional views showing essential parts of the liquid crystal display device. la, lb...Glass substrate, 2a, 2b...Transparent electrode, 4a, 4b...Alignment film, 5...S,mC liquid crystal layer, 89...Resist layer, 10.11...・Substrate agent Patent attorney Keiichi Kazuzu

Claims (1)

[Claims] A pair of transparent electrode insulating substrates having transparent electrodes selectively formed on their surfaces and alignment films formed thereon are arranged so that the alignment films face each other, and these In a liquid crystal display device in which a ferroelectric liquid crystal layer is interposed between transparent insulating substrates, and the ferroelectric liquid crystal layer is driven by selectively applying a voltage to the transparent electrodes, each of the pair of transparent insulating substrates is Among the alignment films, in the pixel parts where the transparent electrodes of a pair of transparent insulating substrates intersect with each other, rubbing treatment is performed under the same conditions or under conditions with a small difference. 1. A liquid crystal display device characterized in that non-picture element areas where the dots do not intersect are subjected to rubbing processing under conditions that are significantly different from each other.