JPS6131449B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a liquid crystal display element that utilizes homogeneous alignment, and more particularly to an alignment film for a liquid crystal display element. A liquid crystal display device basically has two glass substrates arranged in parallel at a certain distance, and a transparent conductive film is selectively arranged on each of the opposing surfaces of these two substrates. Moreover, both the conductive film and the glass surface are completely covered with an alignment film that orients the liquid crystal in a certain direction, and the space between these alignment films is filled with liquid crystal, so that the entire circumference of the substrate is covered with liquid crystal. The structure is such that a polarizing plate is disposed on the surface of the substrate on which the alignment film is not formed. Display methods of liquid crystal display elements with this basic configuration include (a) twisted nematic field effect display method (b) induced birefringence field effect display method (c) dynamic scattering display method (d ) Guest-host type two-color display method (e) Orientation vibration display method, etc., and method (a) is widely put into practical use. Conventionally, the alignment film of a liquid crystal display element is made of (a) an oblique vapor deposition film such as silicon oxide, and (b) a surface treatment film, a thermosetting polymer film such as a linear polymer or epoxy resin that is rubbed. (c) A polyimide film with good heat resistance and a rubbing treatment is used. However, all of the above-mentioned alignment films had the following drawbacks. (a) The orientation ability of obliquely deposited films such as silicon oxide differs depending on the liquid crystal used, and some liquid crystals do not align at all. For this reason, it is not possible to use a mixture of various liquid crystals to improve the temperature characteristics and electro-optical characteristics of the liquid crystal. Also, the viewing angle characteristics are slightly inferior. Furthermore, since the refractive index is <1.65, electrode reflection cannot be prevented even if the film is coated with an appropriate thickness. It is also inappropriate from the point of view of cost reduction. (b) The orientation ability of surface-treated films, linear polymers, thermosetting polymer films such as epoxy resins, etc. decreases when the sealant or sealant is heated to perform sealing or sealing work. (c) A polyimide film (for example, a condensate of diaminodiphenyl ether and an acid anhydride) is noticeably colored during ring closure by heating. Furthermore, recently, in order to reduce costs, the sealing method has been changing from glass frit seals to organic (epoxy resin) seals, and in order to achieve the same high reliability with organic seals as with frits, it is necessary to bond them to the glass substrate under wet conditions. However, even if a silane coupling agent is added to the above-mentioned polyimide type, the adhesion to glass deteriorates, and high reliability, which can be replaced by a frit seal, cannot be obtained. The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and (a) provide excellent moisture resistance for adhesion to glass substrates;
The object of the present invention is to provide an alignment film that (b) has good rubbing resistance, (c) is resistant to coloring during curing, (d) has strong alignment regulating power, and (e) has no visible electrode pattern. The present invention has been made in this regard, and a first feature of the present invention is that, in a liquid crystal display element having a liquid crystal layer sandwiched between a pair of substrates on which transparent electrodes are formed, As an alignment film material, the general formula (However, R ₁ is a divalent hydrocarbon group, R ₂ and R ₃ are monovalent hydrocarbon groups, m is an integer of 1 to 4) 2.5 to 20.0 mol% of diaminodisiloxane, aromatic diamine 97.5 to By using a polyimide obtained by dehydrating and ring-closing a polyamic acid obtained by reacting a diamine and a tetracarboxylic dianhydride containing 80.0 mol% as essential components, the adhesion to the glass substrate can be improved by adding the above-mentioned diaminodisiloxane. This greatly improves moisture resistance. The diaminodisiloxane used in the present invention specifically includes, for example, compounds represented by the following group. etc., and at least one kind of the above-mentioned compounds is used. The amount of the diaminodisiloxane added is preferably 2.5 to 20.0 mol%, more preferably 5.0 to 7.5 mol% of the total diamine component. If the amount is more than 20.0 mol %, the orientation force and the ultimate viscosity will be lowered, and if it is less than 2.5 mol %, sufficient adhesive strength will not be obtained. Examples of the acid anhydride used in the present invention include pyromellitic dianhydride and benzophenonetetracarboxylic dianhydride. The reaction solvent used in the present invention is N/N-dimethylformamide, N/N-dimethylacetamide,
N-methyl-2-pyrrolidone, N-ethyl-2-
These include pyrrolidone, N-cyclohexyl-2-pyrrolidone, N-benzyl-2-pyrrolidone, N-acetyl-ε-caprolactam, and the like. The second feature of the present invention is that the aromatic diamine has the general formula: (However, R ₄ , R ₅ , R ₆ , R ₇ are hydrogen atoms, methyl groups,
(ethyl group, R ₈ and R ₉ are methyl and ethyl groups), by using this, the alignment film is made colorless and the ultimate viscosity of the polyamic acid is increased. . If the viscosity does not exceed a certain level, the workability of coating methods such as printing will be poor. In addition, when performing strong rubbing, use the diamine () mentioned above. (However, R ₁₀ is -O-,

【formula】

【formula】

【formula】

[Formula] If X is -O-, -CO-, -COO-, -CONH-, )(), an alignment film with sufficiently high film strength can be obtained. As the mixing ratio, () is the diamine component
By selecting 10.0 to 82.5 mol% and () within the range of 15.0 to 70.0 mol%, it is possible to improve the film strength with almost no coloration. () is 70 mol%
If the content exceeds 10%, the coloring of the film will be noticeable, and if the content of () is less than 15 mol%, the film will have poor strength against strong rubbing. Methods for applying the reaction condensation solution of the present invention onto a glass substrate on which a transparent conductive film is formed include a dipping method, a spin coating method, a spray method, a printing method, etc.
After application, it is cured at approximately 200-350°C to achieve intramolecular ring closure, and then rubbed. As for the rubbing method, gauze and buffing can generally be used. Liquid crystals that can be used in combination with the alignment film of the present invention include nemate liquid crystals such as Schiff base type liquid crystals, phenylcyclohexane type liquid crystals, azoxy type liquid crystals, azo type liquid crystals, biphenyl type liquid crystals, ester type liquid crystals, and phenyl-pyridine type liquid crystals. Examples include cholesteric liquid crystals in which optically active compounds such as optically active substances, cholesterol compounds, biphenyl derivatives having optically active substituents, and phenylbenzoate are added to the above-mentioned nematic liquid crystals. Further, the sealing agent that can be used in combination with the alignment film of the present invention is an organic material such as an epoxy resin. The substrate used in combination with the alignment film of the present invention is made of glass or has a glass surface coated with SiO ₂ . The transparent electrode is mainly composed of tin oxide and indium oxide, and is formed on a glass substrate by a vacuum evaporation method or the like. Hereinafter, the present invention will be explained in detail with reference to Examples. Example 1 As shown in the figure, a film with a thickness of 350 Å was deposited on a glass substrate 1.
In ₂ O ₃ +SnO ₂ (20:1) electrode 2 was formed. Then 0.0132 mole, 0.0153 mole, Put 0.0015 mol in a four-necked flask and add N-methyl-
178g of 2-pyrrolidone was added and stirred. While keeping at 0℃~5℃ with ice

[Formula] 0.0303 mol was added, and the reaction temperature was kept below 5° C. and stirred for 6 hours. The thus obtained polymer solution was stirred at 70°C for about 2 hours to lower its viscosity, and then printed and coated on the electrode formation side of the substrate (8 wt%, 500 cp at 25°C), and heated at 300°C for 30 minutes to complete ring closure. . Thereafter, a rubbing treatment was performed to obtain an alignment film 3. (Alignment film thickness = 800 Å) Next, the alignment film surfaces were placed parallel to each other and sealed with epoxy resin except for the liquid crystal injection port, and heated at 180° C. for 2 hours to form a sealed portion 4. After that, liquid crystal 5 was sealed. The encapsulated liquid crystal is a mixture of azoxy type (CH ₃ O− wt ratio 1:1), ester mixture ( wt ratio 1:1:1), biphenyl type liquid crystal mixture wt ratio 1:1:1), cyclohexane phenyl type mixture wt ratio 1:1:1), Schiff base type mixture There are five types with a wt ratio of 1:1:1). The sealing port was sealed with NiCrAu vapor-deposited solder. Furthermore, a polarizing plate 6 was attached in accordance with the rubbing direction of the alignment film. The orientation was extremely good, and reflection from the transparent electrode was completely prevented. Heat the above element at 70℃
When the film was placed in a 95% RH environment and the creepage resistance decreased due to film peeling, it remained unchanged even after 1000 hours. To examine the coloring properties, an 800 Å thick alignment film was formed on a glass substrate without transparent electrodes, and a liquid crystal was sandwiched between the layers to create a device. Using a spectrometer without a polarizing plate, the ratio of transmittance at wavelengths of 400 nm and 600 nm was 0.86. As a comparative example, a coupling agent (NUC A-1100) was added to a polyamic acid obtained by condensing 4,4'-diaminodiphenyl ether and pyromellitic dianhydride.
When 5.0 wt% of the solid content was added and the film was applied by printing and ring-closing by heating at 300°C for 30 minutes and used as an alignment film, the alignment was good, but
In the 70℃95%RH life test, it lasted only up to 100 hours. Regarding coloring, the wavelength is 400nm.
The transmittance ratio at 600 nm was 0.75 at a film thickness of 800 Å, and the yellow coloration was actually noticeable even when visually observed. Example 2 Polymers were synthesized with the compositions shown in Table 1, and elements were prepared and coloring properties were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2. In No. 1, the adhesion was insufficient, and in No. 5, the ultimate viscosity did not increase and the orientation regulating force was partially weakened. Also
No. 10 has noticeable coloring. Everything else is fine.

【table】

[Table] This table satisfies the purpose of the present invention. especially
No. 8 and No. 9 have high film strength and have sufficient work margin during rubbing.

[Table] As described above, by using the present invention in a liquid crystal alignment film, an element with excellent alignment properties, resistant to coloring, and excellent adhesion to substrates was obtained. [1000h in 70℃95%RH humidity life test
More than good. T400nm/T600nm ratio 0.85 (film thickness 800
Å)〕Furthermore The product containing 20% of diamine has a sufficient working margin during rubbing.

[Brief explanation of the drawing]

The figure is a cross-sectional view of a liquid crystal display element. However, the liquid crystal filling port is omitted and not shown. DESCRIPTION OF SYMBOLS 1...Glass substrate, 2...Transparent electrode, 3...Alignment film, 4...Sealing agent, 5...Liquid crystal, 6...Polarizing plate.

Claims (1)

[Scope of Claims] 1. In a liquid crystal display element having a liquid crystal layer sandwiched between a pair of substrates on which transparent electrodes are formed, an alignment film made of the following general formula as diaminosiloxane is provided on the opposing surface of the substrates. (However, R ₁ is a divalent hydrocarbon group, R ₂ and R ₃ are monovalent hydrocarbon groups, and m is an integer of 1 to 4) 2.5 to 20.0 mol% of the compound represented by the following general aromatic diamine: formula (However, R ₄ , R ₅ , R ₆ , and R ₇ are hydrogen atoms, methyl groups, and ethyl groups, and R ₈ and R ₉ are methyl groups and ethyl groups.)
A liquid crystal display element characterized by using a polyimide obtained by dehydrating and ring-closing a polyamic acid obtained by reacting a diamine containing 97.5 to 80.0 mol% of the compound represented by the formula with tetracarboxylic dianhydride as an essential component. 2 The aromatic diamine described in claim 1 has the general formula (R ₄ , R ₅ , R ₆ , R ₇ are hydrogen atoms, methyl groups, ethyl groups, R ₈ , R ₉ are methyl groups, ethyl groups) 10.0 to 82.5 mol%, general formula (R ₁₀ is -O-, [formula] [formula] [Formula] X is -O-, -CO-, -COO-, -CONH-,)
A liquid crystal display element comprising 15.0 to 70.0 mol%.