JPS61185728A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To enable liquid crystal display high in density and reliability to be attained without forming black striations and bleeding by using an orientation control film obtained by applying an aq. soln. mixture contg. specified amts. of PVA and titanium alkoxide and heating it. CONSTITUTION:The orientation control film is formed by coating a base plate with an aq. soln. mixture contg. one pt.wt. of PVA and 2-4 pts.wt. of titaium alkoxide and heating it to dry it and simultaneously to cross-link both with each other and to restrain hygroscopicity. The use of a comparatively large amt. of titanium alkoxide permits this hygroscopicity restraining action to be enhanced, and practicably sufficient orientation control ability and insulating property to be obtained, and the use of such an orientation control film sufficiently rubbed, for example, for a TN liquid crystal display device, etc., to prevent black striations and bleeding and to attain good display.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to liquid crystal elements used in various displays, etc., and particularly relates to liquid crystal elements used in various displays, etc.
The present invention relates to a liquid crystal element having, as an alignment control film, a film formed by applying and heating a mixed aqueous solution of titanium alkoxide and titanium alkoxide.

[Prior Art] PVA has been known as a material that forms a film that can function as an alignment control film without using toxic or flammable organic solvents and by heating at a relatively low temperature. PV
Since A is water-soluble, using water as a solvent facilitates operational safety management. In addition, since heating during film formation can be done at a low temperature, it has many advantages, such as being able to easily use a plastic substrate or a liquid crystal display with transistors, regardless of their heat resistance. However, if an aqueous solution of PVA is directly applied to a substrate and heated to form an alignment control film, a sufficiently durable liquid crystal display cannot be obtained because the solution has hygroscopic properties. Therefore, research is being conducted to improve this and obtain a liquid crystal display that takes advantage of the advantages of PVA.

In order to improve the above, it is known that an alignment control film is formed by applying a mixed aqueous solution containing 0.5 to 2 parts by weight of titanium alkoxide to 1 part of PVA onto the substrate surface and then heating it. (Unexamined Japanese Patent Publication No. 59-45428). This is done by adding titanium alkoxide within a range that does not impair the orientation controllability and insulation properties of the PVA coating, and suppressing the hygroscopicity of the coating formed by the crosslinking reaction between PVA and titanium alkoxide. A liquid crystal display having an alignment control film made of a PVA film added with titanium alkoxide has obtained good results when used for general display with relatively large pixels.

[Problems to be Solved by the Invention] However, when the present inventor evaluated a liquid crystal display having an alignment control film formed by the above formulation,
A moisture resistance test has revealed that in a liquid crystal display having electrodes arranged at minute intervals, adjacent electrodes act as pseudo electrodes, causing a phenomenon in which non-display areas are lit.

In other words, in order to obtain a compact and high-density liquid crystal display, when the gap between the wiring lines in the display section is about 100 gm to 50 pm, even if the insulation of the substrate surface in the gap between the electrodes is relatively small, When the orientation control U4 film decreases due to moisture absorption, the surface of this gap also becomes an apparent electrode, and a voltage difference is applied between the common electrodes above the gap. As a result of this,
7g shows that the wiring which is the non-display part is lit. This condition is called a ring streak defect (a thin, stripe-like defect in the wiring). In addition, with respect to the original display lighting segment, a non-lighting substrate surface around the segment acts as an apparent electrode, and a state occurs in which the display lights up between the common electrodes, which are provided in advance larger than the segment. This is called a bleeding defect (lighting that oozes out around the original lighting display area).

Since these ring streaks and blurring occur over extremely limited distances, they do not usually pose a problem in general displays with relatively large pixels, and have been overlooked until now. This was discovered for the first time by the present inventors as a result of research aimed at obtaining fine patterns as highly reliable displays.

The present invention solves the problems found by the inventors, and
The purpose of the present invention is to obtain a high-density, highly reliable liquid crystal display that does not cause ring streaks or bleeding.

[Means for Solving the Problems] As a result of various studies on the amount of titanium alkoxide added to PVA, the present invention has discovered that 1 part by weight of PVA, which has conventionally been thought to impair orientation controllability and insulation properties, has been developed. On the other hand, even if more than 2 parts by weight of titanium alkoxide is added, there is no practical problem in alignment control or insulation, and on the contrary, it has the advantage of preventing ring streaks and bleeding when used in high-density liquid crystal displays. This was done based on the knowledge of the wood inventors that the following could be obtained.

That is, the measures taken to solve the above problems are as follows:
To provide a liquid crystal element having, as an alignment control film, a film formed by coating and heating a mixed aqueous solution containing more than 2 parts by weight of titanium alkoxide and 4 parts by weight per 1 part by weight of polyvinyl alcohol. .

The PVA used in the present invention has a polymerization degree of too much to 30
00, and those with a degree of corrosion of 98 to 100% are preferred. PVA with a low degree of polymerization and saponification has insufficient moisture resistance, while one with a high degree of polymerization has poor solubility in water,
Both are less practical. In the present invention, reactive PVA having a functional group such as an active carboxyl group in a part of the main chain is preferably used.

As the titanium alkoxide, chelated titanium alkoxide is preferable in terms of obtaining good solubility in water. Titanium alkoxide having a structure of T i (OR) 4 using a lower alcohol is not preferable because it is hydrolyzed when it is made into an aqueous solution, resulting in clouding. Specific examples of titanium alkoxides preferably used in the present invention include Jimmy propoxy bis(acetylacetonate).
Examples include titanium, di-n-butoxy bis(triethanolamineto) titanium, dihydroxy bis(lactato) titanium, and the like.

The above mixing ratio of PVA and titanium alkoxide is PVA
It is necessary that the amount of titanium alkoxide is more than 2 parts by weight and less than 4 parts by weight per 1 part by weight. If the amount of titanium alkoxide added is less than 2 parts by weight, it is not possible to sufficiently prevent ring streaks and blurring when used in a high-density liquid crystal display. On the contrary, 4
If the amount exceeds 1 part by weight, the resulting orientation control film will have inadequate orientation control properties and insulation properties.

The solvent for PVA and titanium alkoxide is water, but
Add water-soluble colcols to this to adjust the viscosity to HJ”M.
This is preferable because it improves the applicability to the substrate, and in particular allows the coating to be applied to the substrate surface by printing. Specific examples of alcohols include alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol, and glycols such as ethylene glycol and propylene glycol.

After applying the mixed aqueous solution of PVA and titanium alkoxide, heating is preferably performed at about 180°C to 220°C for 30 to 90 minutes. In addition, the thickness of the coating is 8008~2
Approximately 00OA is preferable.

[Function] When heated, PVA and titanium alkoxide undergo a crosslinking reaction, thereby suppressing the hygroscopicity of the formed film. In particular, in the present invention, since the amount of titanium alkoxide added is larger than in the conventional case, this hygroscopicity suppressing 1F effect is strong. On the other hand, according to the research conducted by the present inventors, despite the addition of such a large amount of titanium alkoxide, the resulting orientation control film can have orientation control properties and insulation properties that are comparable to those found in the past.

[Example] The liquid crystal display according to the present invention is the same as the conventional one except for the composition of the alignment control film.
TN) Suitable for use as a liquid crystal display. Prior to the embodiment, its basic structure will be explained with reference to FIG.

In the figure, 1 is a transparent insulating substrate, 2 is a transparent conductive film, 3 is an alignment control film, 4 is a liquid crystal, 5 is a sealant that also serves as a spacer, and 6 is a polarizing plate.

The alignment control film 3 is rubbed in a certain direction so that the molecules of the liquid crystal 4 are oriented in a certain direction. LCD 4
The area to be filled is surrounded with a sealant 5, and the liquid crystal 4 is infiltrated through an opening provided at the negative position, and then sealed. Although this example has a transmission type structure, one polarizing plate 6 may have a reflection type structure in which a reflection plate is added. Further, although the present invention is suitable for those using TN liquid crystal,
It can be widely applied to liquid crystal displays that use homogeneous alignment that undergoes alignment treatment by rubbing.

Example 1 The effective display size is 20 mm x 30 mm, and has a 7-segment display consisting of 40 segments and a stylized pattern display. A TN-type liquid crystal display of type a shown in FIG. As shown in Table 1, the orientation control film is made of dihydroxy bis(lactato) titanium 100 and PV.
After forming a coating film with a solution in which 48 parts by weight of A was mixed and dissolved in water and ethylene glycol as a solvent,
It was baked for 0 minutes to obtain an orientation control film with a thickness of 1000A. After placing this indicator in the pressure Kutzker tester, 6
When a lighting test was conducted using V, there were no black lines or blurring out of 20 even after 24 cycles, and the display condition was good.

Examples 2 to 5 Tests were conducted in the same manner as in Example 1, except that the coating solution had the composition shown in Table 1. Even after 24 hours, only O out of 20 samples had black streaks or blemishes. The display condition was also good.

Comparative Example 1 Inspection was conducted in the same manner as in Example 1 except that the coating solution had the composition shown in Table 1. In the lighting test after 24 hours, 7 out of 10 had black streaks and rainbow spots. Occurrence was observed.

Table 1 A; dihydroxy bis(lactato)titanium B; G1
-Propoxy bis(acetylacetonato) titanium C; di-n-butoxy bis(triethanolaminato) titanium In addition to the above-mentioned TN liquid crystal, the present invention also applies to US Pat.
A ferroelectric liquid crystal described in No. 67924 can also be used.

[Effects of the Invention] According to the present invention, moisture resistance is improved, and even when a high-density liquid crystal display is used, the display is not disturbed by ring streaks or blurring, and a highly reliable liquid crystal display can be obtained. A vessel is obtained. Additionally, since the adhesion of the alignment control film to the substrate is increased, the durability against thermal shock, etc. is increased, and the benefits of forming the alignment control film using low-temperature processes and non-polluting materials can be obtained. .

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing the basic structure of a liquid crystal display according to the present invention. 1: Transparent insulating substrate, 2: Transparent conductive film, 3: Alignment control film, 4: Liquid crystal, 5: Sealing agent also used as varnish spacer, 6: Polarizing plate.

Claims (1)

[Claims] 1) A liquid crystal characterized by having a film formed by coating and heating a mixed aqueous solution containing more than 2 parts by weight of titanium alkoxide and less than 4 parts by weight of titanium alkoxide per 1 part by weight of polyvinyl alcohol as an alignment control film. element.