JPS63223727A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To eliminate unevenness of background color improving thus electrooptic characteristic such as storage characteristic, etc., by forming orientation films having different polarity to each other on an electrode surface and another surface the electrode surface. CONSTITUTION:In a liquid crystal display element of this invention, bistability of electrooptic characteristic such as storage characteristic is secured by the formation of orientation films 3 having equal polarity to each other on the surface of each confronting electrode 2, and an orientation film 4 having different polarity to the orientation film 3 on the electrode surface is formed on the surface of a display element substrate 1 other than the electrode surface. Thus, the unevenness of background color is eliminated by producing preferentially only either one of UP 18 or DOWN 19. By this method, the unevenness of background color is eliminated by using an orientation film on electrode surface having different polarity to that of an orientation film on another surface. Moreover, the difference between the level of the electrode and other part is lessened, thus electrooptic characteristics such as storage characteristic are improved.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid crystal display element.

[Conventional technology]

In a display element using ferroelectric liquid crystal, an alignment agent made of a uniform material is coated on a substrate to form an alignment film, without distinguishing between electrode surfaces and other surfaces.

[Problem 3 to be solved by the invention The principle of the conventional liquid crystal display element using ferroelectric liquid crystal is
- Shown in Figure 6.

FIG. 3 shows the switching principle of a display element using ferroelectric liquid crystal. Picture as shown in Figure 3 (b)) *
At t3, when the electric field 17 is applied from the opposite side to the front side, 1
The spontaneous polarization 15 of the ferroelectric liquid crystal molecules 14 also faces toward you, (
This state is called up) This force ferroelectric liquid crystal molecule 1
The molecular axis (i.e., optical axis) 16 of 4 is oriented counterclockwise with respect to the layer normal 12, and the transmission axis of the polarizer 11 (or any of the analyzers 10) is aligned with the optical axis of this liquid crystal molecule. If you leave it on, the light will be blocked and you will be in a dark state.

When the electric field 17 is applied from the front side to the opposite side as shown in FIG. 3 (6), the spontaneous polarization of the ferroelectric liquid crystal molecules 14 also faces toward
This state is called down) The molecular axis (i.e., optical axis) 16 of the ferroelectric liquid crystal is oriented clockwise with respect to the layer property [12. At this time, the optical axis lG of the molecule is It is off from both transmission axes of the analyzer 10, and light leaks out to create a bright state.

FIG. 4 is a sectional view of a substrate in a conventional liquid crystal display element. A striped transparent electrode 2 is formed on the substrate 1.1 by a method such as vapor deposition.

Historically, an alignment film 3 has been formed from the ox.

In conventional liquid crystal display elements, the alignment material of the same material is applied to the substrate and the lower substrate to form an alignment @, and there is no distinction between the electrode surface and the substrate surface other than the electrode, and the alignment material is uniformly aligned with the substrate. An alignment film of the material is formed.

Therefore, the energy is equal between up and down, and since ferroelectric liquid crystals are bistable.

It does not fit with intermediate orientations other than up and down.

Therefore, when the liquid crystal is slowly cooled without applying an electric field after heating to orient the ferromagnetic liquid crystal, an up region 18 and a down region 19 are generated as shown in FIG. 3(C).

Since no electric field is applied between the substrate surfaces other than the pixels, two regions, up and tarran, are formed as shown in FIG. 3(C).

Therefore, in the element part other than the pixel which is the background color, a hierarchical pattern part and a bright state part are generated.

In the case of an 8-character segment display, etc., as shown in Figure 5, if the background color has a hierarchy B20 and a bright state 21, it may not be possible to distinguish between the background color and the lighting section B, making it impractical. becomes.

Also, 6th r! Even when a matrix voltage is used as in JJ, the element portion where the background color is in the dark state is always darker than the element portion where the background color is in the bright state, resulting in display unevenness, which is inconvenient.

To solve the above drawbacks, it is possible to monostabilize the liquid crystal molecules only in either the up or down direction by changing the polarity of the alignment agent between the upper and lower substrates. However, since the polarity of the alignment film on the pixel is also different between the upper and lower substrates, only either the up or down direction is stabilized, which is a characteristic of liquid crystal display elements using ferroelectric liquid crystals. This is thought to cause problems such as inability to obtain IJ-characteristics.

It is an object of the present invention to solve these problems and provide a liquid crystal display element that eliminates unevenness in background color and has excellent electro-optical characteristics such as memory.

Means for Solving All Problems C] The present invention secures bistability in electro-optical properties such as memory property by forming orientations [-] having the same polarity on opposing electrode surfaces, By forming an oriented mt shadow with a polarity different from that of the oriented film on the 11L pole surface on the display element substrate other than the electrode surface, only one of the amplifier or down f: background color can be created preferentially. This eliminates the unevenness.

[Iro row]

FIG. 4 is a cross-sectional view of one of a pair of substrates of a conventional liquid crystal display element having a simple matrix structure. l is a substrate made of glass.

IT Off transparent electrodes 2 are formed in a row.

An alignment material made of polyimide is applied to the entire surface of the substrate and the electrodes, and is fired to form the entire alignment film 3.

In the present invention, a further step is performed.

First, a positive type photoresist is applied, and only the portions other than the electrodes are exposed to t-light using the same photomask used when forming the electrodes, and then the resist in the portions J: other than the electrodes is removed using a developer. Polyvinyl alcohol (PVa) is used as a highly polar alignment agent for the front substrate, and polyethylene (PE) is used as a less polar alignment agent for the opposite substrate.
) in a highly resistant organic solvent, apply the solution and dry.

At this time, since the positive resist is hydrophobic, the highly polar organic solvent that dissolved %PTA or PE is repelled and accumulates in areas where there is no resist, that is, areas other than the electrodes on the substrate, and some parts on the resist. It is applied very thinly and roughly.

The entire substrate is heated to 100 degrees Celsius or higher to increase the degree of polymerization of PVa or 1'E, thereby increasing the corrosion resistance to the developer. By irradiating the entire substrate with light again and developing it, all of the food resist can be removed. In this way, a durable board as shown in Fig. 1 is obtained.1 In a normal board, P
1 After forming the model, the difference in level between the electrode and other parts is 100
~100 OA, whereas in the present invention, the area other than the electrode is further filled with a structured film other than the P material, so the OA is approximately 100 OA.
The height difference was kept to 500Δ or less, and it was possible to make it approximately OL depending on one condition.

After rubbing the substrate of the present invention in a certain direction with a cotton cloth so that the rubbing direction is vertical when both substrates face each other, silica balls with a particle size of about 2 microns are sprayed and dispersed as spacers around one periphery. A sealant was applied to the panel, and the opposite and front substrates were assembled so that the electrodes were perpendicular to each other, crimped, and heated to solidify to produce a panel. Furthermore, a strong visit 'fI1. A liquid crystal display element of the present invention was obtained by enclosing a liquid crystal composition.

In the pixel portion where the electrodes face each other, alignment films are formed of Pl on both substrates, as in the conventional case.

Furthermore, since the height difference between the electrode and other parts is smaller than that of the conventional one, there are fewer defects, the optical uniformity is high, and the amount of leaked light in the dark state is less than 80 inches compared to the conventional one. In addition, because there are fewer disclinations (defects), spontaneous reversal of molecules during memory is less likely to occur, resulting in high memory stability.

The polarity of the alignment film on the front substrate is always high in areas other than the electrode on the electrode, or in areas where the other parts face each other, so that the spontaneous polarization of the crystal always tends towards the opposite substrate. I'm aiming.

Therefore, by setting the transmission optical axis of the polarizer and the transmission optical axis of the analyzer as shown in Figure 2, it is possible to make all the background colors bright, and it is possible to eliminate uneven background colors. Ta.

Note that the polarity of the alignment film formed on the parts other than the electrodes is opposite to that of this example, and a highly polar alignment film is placed on the opposite side.

It is also possible to arrange an alignment film with low polarity on the front side. Furthermore, by changing the absorption axes of the polarizer and analyzer, it is possible to darken the background color.

〔Effect of the invention〕

In a liquid crystal display element using a strongly electrostatic liquid crystal, by changing the polarity of the alignment film between the electrode surface and the other surfaces, it was possible to eliminate uneven background color.

Furthermore, since the difference in level between the electrode and other parts can be reduced, electro-optical properties such as memory properties can be improved.

Although the number of steps has increased compared to the conventional method, there is no need to newly manufacture expensive equipment such as photo masks, so the yield is good considering orientation defects, and it is actually more cost-effective. It became.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a substrate in the present invention. Figure 2 is a front view of the matrix panel in the present invention;
Ca) represents the dark state, and (b) represents the time of switching to the bright state. Figure 3 is a diagram showing the switching principle of a display element using a conventional liquid crystal, where (α) is up (dark state), (
b) is a down (closed shape 9), and (C) is a diagram when there are two regions, up and down. FIG. 4 is a sectional view of a substrate in a conventional display element. Fig. 5 is a diagram showing the display state of an 8-character segment using a conventional display element, (ω is the hierarchy a, (6) is a diagram showing a bright state. Fig. 6 is a diagram showing a matrix using a conventional display element. , a front view of the panel, (cL) is the level VI4. [b) is a diagram showing the state when switched to the bright state. l... Substrate 2... Electrode 3... Alignment film (Pl) 4... Alignment film (high polarity or low orientation [) 5... Substrate 6... Signal electrode 7... Scanning electrode 8... Pixel 9. Portions other than pixels lO.. Analyzer 11.. Polarizer 12.. Normal to the ferroelectric liquid crystal layer 13.. Ferroelectric liquid crystal molecules 14.. Ferroelectric liquid crystal molecules 15. Spontaneous polarization Direction 16... Direction of ferroelectric liquid crystal molecules (direction of optical axis) 17.
・Direction of applied potential 18...Up (dark state) 19.Fist down/(bright state) Added force Dark state region 21--Bright state region ρ...Segments e Dark state region and more Person Seiko Hei Epson Co., Ltd. Agent Tsutomu Mogami, patent attorney, and one other person Figure 1 (α) (Figure 3 Figure 51!l)

Claims (2)

[Claims] (1) A liquid crystal display element using ferroelectric liquid crystal, characterized in that alignment films having different polarities are formed on electrode surfaces and other surfaces. (2) In a pair of opposing substrates, alignment films of equal polarity are formed on each pair of opposing electrodes, and the alignment film formed on the electrodes is formed on the surface of one substrate other than the electrodes. Claim 1, characterized in that an alignment film having a high polarity is formed, and an alignment film having a lower polarity than the alignment film formed on the electrode is formed on a surface of the other substrate other than the electrode. liquid crystal display element.