JP5035517B2 - Liquid crystal aligning agent and liquid crystal display element using the same - Google Patents

Description

  The present invention relates to a liquid crystal alignment agent used when producing a liquid crystal alignment film, a liquid crystal alignment film obtained from the liquid crystal alignment agent, and a liquid crystal display element having the liquid crystal alignment film.

  Liquid crystal display elements used in liquid crystal televisions, liquid crystal monitors, liquid crystal displays for portable devices, etc., have excellent productivity and chemical and thermal durability. Most often used. This polyimide-based liquid crystal alignment film is produced by applying a polyimide solution or a polyamic acid solution, which is a polyimide precursor, to a substrate and firing at a temperature of about 200 to 250 ° C.

  The baking process for preparing a polyimide-based liquid crystal alignment film is a part that particularly requires a high temperature in the process of manufacturing a liquid crystal display element. A polyimide-based liquid crystal alignment film material that can be baked at a low temperature of 200 ° C. or lower has been proposed (for example, see Patent Document 1).

  Usually, after the polyimide liquid crystal alignment film is baked, the alignment treatment is performed by a so-called rubbing method in which the polyimide-based liquid crystal alignment film is rubbed with a cloth such as cotton, nylon or rayon. In recent years, as an alternative to rubbing, alignment treatment methods that irradiate polarized ultraviolet rays, etc., and liquid crystal display elements using a vertical alignment mode that do not require alignment treatment have been developed and some of them have been put into practical use. The alignment treatment by is in an important position in the process of manufacturing the liquid crystal alignment film.

In recent years, there has been a problem of insufficient mechanical strength of a film against rubbing treatment when a polyimide-based liquid crystal alignment film is fired at a low temperature. That is, when the rubbing process is performed, the surface of the liquid crystal alignment film is damaged, or a part of the film is peeled off from the substrate. In low-temperature firing, the strength of the film is insufficient as compared with a normal firing temperature, so that the problem due to the rubbing treatment becomes a more serious problem. For rubbing resistance during low-temperature firing, a method using a specific tetracarboxylic dianhydride as a raw material for polyamic acid (for example, see Patent Document 2), a method using an additive (for example, see Patent Document 3), etc. Has been proposed.
JP-A-5-158047 JP 2000-298279 A JP 2002-357831 A

  The problem to be solved by the present invention is to provide a material for a liquid crystal alignment film that does not cause film peeling or scratches during rubbing even when firing at 200 ° C. or less, and that provides a good liquid crystal alignment property. Providing a liquid crystal alignment film that can be produced by firing, does not cause film peeling or scratching during rubbing, and provides good liquid crystal alignment, and reduces the energy cost during manufacturing, and can be used for plastic substrates, etc. An object of the present invention is to provide a liquid crystal display element applicable even to a substrate having relatively low heat resistance.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained a good liquid crystal alignment property even when firing at 200 ° C. or less by using a specific diamine, and a film during rubbing. The present inventors have found that a liquid crystal alignment film that does not peel or scratch can be obtained, and have completed the present invention. That is, the present invention has the following features.

1. A polyamic acid obtained by polymerizing a diamine component represented by the following formula [1] and a tetracarboxylic dianhydride component represented by the following formula [2], or dehydrating and ring-closing this polyamic acid A liquid crystal aligning agent containing at least one polymer of the obtained polyimide, wherein the diamine component contains a diamine represented by the following formula [3].

(R ₁ is a divalent organic group)

(R ₂ is a tetravalent organic group)

(N is an integer of 1 to 20, and R ₃ is a hydrogen atom or a methyl group)

2. 2. The liquid crystal aligning agent according to 1, wherein a tetracarboxylic dianhydride having an alicyclic structure is contained in R ₂ of the formula [2] as a tetracarboxylic dianhydride component represented by the formula [2].

3. 3. A liquid crystal alignment film obtained from the liquid crystal alignment agent according to 1 or 2 above.

4). The liquid crystal aligning film obtained by apply | coating the liquid crystal aligning agent of said 1 or 2 to a board | substrate, baking at the temperature of 200 degrees C or less, and rubbing.

5). 5. A liquid crystal display element having the liquid crystal alignment film as described in 3 or 4 above.

  Even if the liquid crystal aligning agent of this invention is 200 degrees C or less baking film, neither film peeling nor a damage | wound generate | occur | produces by a rubbing process, but can obtain the liquid crystal aligning film with favorable orientation of a liquid crystal.

The present invention is described in detail below.

  The liquid crystal aligning agent of this invention is a polyamic acid obtained by carrying out the polymerization reaction of the diamine component represented by the said Formula [1], and the tetracarboxylic dianhydride component represented by the said Formula [2], or A liquid crystal aligning agent containing at least one polymer of polyimide obtained by dehydrating and ring-closing this polyamic acid, and the diamine component contains a diamine represented by the following formula [3] There are features.

(N is an integer of 1 to 20, and R ₃ is a hydrogen atom or a methyl group)

  In the above formula [3], the bonding position of the two amino groups on the benzene ring is not particularly limited. The two amino groups are the 2,3-position, 2,4-position, 2,5-position, 2,6-position, 3,4-position with respect to the substituent having an acrylate structure at the terminal. Position, 3,5-position, preferably 2,4-position, or 3,5-position. N in Formula [3] is an integer of 1-20, Preferably it is 1-10. In the diamine component, one type of diamine represented by the formula [3] may be used, or two or more types may be mixed.

In the diamine component represented by the formula [1] used for the polymerization reaction of the polyamic acid, the ratio of the diamine represented by the formula [3] is not particularly limited, but the viewpoint of suppressing film peeling and rubbing scratches during rubbing To 10 mol% or more, more preferably 30 mol% or more. The diamine represented by the formula [3] may be 100 mol% of the diamine component. When the proportion of the diamine represented by the formula [3] is less than 100 mol%, the structure and composition of the remaining diamine component are not particularly limited. If Specific examples of the diamine component other than the diamine represented by the formula [3], there may be mentioned diamines R ₁ in the formula [1] is a divalent organic group shown in the following Table, which are 1 A kind may be sufficient and two or more kinds may be used together.

When a diamine having R ₁ of B-83 to B-104 is used as part of the diamine component, the pretilt angle of the liquid crystal can be increased when the liquid crystal alignment film is formed.

The structure and composition of the tetracarboxylic dianhydride component represented by the formula [2] used in the polymerization reaction of the polyamic acid are not particularly limited, and may be one type of compound or two or more types of compounds. You may use together. If Specific examples of the compound include a tetracarboxylic acid dianhydride R ₂ is a tetravalent organic group shown in the following Table of formula [2].

When a tetracarboxylic dianhydride in which R _{2 in} the formula [2] is an organic group having an alicyclic structure is used as the tetracarboxylic dianhydride component, rubbing resistance is further improved, which is preferable. At this time, the ratio of tetracarboxylic dianhydride in which R ₂ of the formula [2] is an organic group having an alicyclic structure in the entire tetracarboxylic dianhydride component is preferably 10 mol% or more, more preferably 20 mol%. It is above, and it is 50 mol% or more especially. Examples of R ₂ having an alicyclic structure include A-1 to A-24 in the above table.

  The polymerization reaction for obtaining a polyamic acid can be performed by mixing a diamine component and a tetracarboxylic dianhydride component in an organic solvent. The organic solvent at this time is not particularly limited as long as the polyamic acid to be generated is dissolved. For example, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N- Examples include methyl caprolactam, dimethyl sulfoxide, tetramethyl urea, pyridine, dimethyl sulfone, hexamethyl sulfoxide, and γ-butyrolactone. These may be used alone or in combination. Moreover, even if it is a solvent which does not dissolve a polyamic acid, you may mix and use it for the said solvent in the range which the produced | generated polyamic acid does not precipitate. Since water in the organic solvent inhibits the polymerization reaction of the polyamic acid and further causes hydrolysis of the generated polyamic acid, it is preferable to use a dehydrated and dried organic solvent as much as possible.

  As a method of mixing the tetracarboxylic dianhydride component and the diamine component in an organic solvent, a solution in which the diamine component is dispersed or dissolved in the organic solvent is stirred, and the tetracarboxylic dianhydride component is used as it is or in an organic solvent. A method of adding by dispersing or dissolving in a solvent, a method of adding a diamine component to a solution in which a tetracarboxylic dianhydride component is dispersed or dissolved in an organic solvent, and a tetracarboxylic dianhydride component and a diamine component. The method of adding alternately etc. are mentioned. When the tetracarboxylic dianhydride component or the diamine component is composed of a plurality of types of compounds, the plurality of types of components may be preliminarily mixed or may be individually polymerized sequentially.

  The temperature at the time of carrying out the polymerization reaction of the polyamic acid is usually -20 to 150 ° C, preferably 0 to 100 ° C, more preferably 10 to 80 ° C. When the temperature is higher, the polymerization reaction is completed earlier, but when it is too high, a high molecular weight polyamic acid may not be obtained. The polymerization reaction can be carried out at any concentration, but if the concentration is too low, it will be difficult to obtain a high molecular weight polymer, and if the concentration is too high, the viscosity of the reaction solution will become too high and uniform stirring will occur. Since it becomes difficult, Preferably it is 1-50 mass%, More preferably, it is 5-30 mass%. The initial stage of the polymerization reaction may be performed at a high concentration, and then an organic solvent may be added.

  The molecular weight of the resulting polyamic acid can be controlled by the molar ratio of the tetracarboxylic dianhydride component and the diamine component used in the polymerization reaction, and the molecular weight increases as this molar ratio approaches 1: 1. The molecular weight of the polyamic acid used in the present invention or the polyimide obtained by dehydrating and ring-closing this polyamic acid is a weight average molecular weight from the viewpoint of ease of handling and stability of characteristics when used as a liquid crystal alignment film. 2,000 to 200,000 is preferable, and 5,000 to 100,000 is more preferable.

  The dehydration ring closure reaction (imidation reaction) for obtaining a polyimide from a polyamic acid can be carried out by stirring the polyamic acid in an organic solvent in the presence of a basic catalyst and an acid anhydride. Examples of the basic catalyst at this time include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Of these, pyridine is preferable because it has an appropriate basicity for proceeding with the reaction. Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, pyromellitic anhydride, and the like. Among them, acetic anhydride is preferable because the obtained polyimide can be easily purified after imidization. As an organic solvent, the solvent used at the time of the polymerization reaction of the polyamic acid mentioned above can be used.

  The imidation ratio of polyimide can be controlled by adjusting the amount of catalyst, reaction temperature, and reaction time. The amount of the basic catalyst is preferably 0.5 to 30 times mol, more preferably 2 to 20 times mol of the amic acid group. Further, the amount of the acid anhydride is preferably 1 to 50 times mol, more preferably 3 to 30 times mol of the amic acid group. The reaction temperature is preferably -20 to 250 ° C, more preferably 0 to 180 ° C. The imidation ratio of the polyimide used for the liquid crystal aligning agent of the present invention is not necessarily 100%, and may be partially imidized.

  The polyamic acid or polyimide obtained as described above can be recovered by putting the reaction solution into a poor solvent that is being stirred, precipitating, and filtering. Although it does not specifically limit as a poor solvent used in this case, Methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene etc. can be mentioned.

  The liquid crystal aligning agent of this invention can be obtained by dissolving at least one polymer of the polyamic acid obtained as described above or a polyimide obtained by dehydrating and ring-closing the polyamic acid in an organic solvent. Further, the reaction solution of polyamic acid or polyimide may be used as it is or diluted with an organic solvent.

  The organic solvent used for dissolving the polymer or diluting the reaction solution is not particularly limited as long as it dissolves the contained polymer component. Specific examples include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, Examples thereof include dimethyl sulfoxide, tetramethyl urea, pyridine, dimethyl sulfone, hexamethyl sulfoxide, and γ-butyrolactone, and these may be used alone or in combination.

  Further, even if the solvent alone does not dissolve the polymer component, it can be mixed with the liquid crystal aligning agent of the present invention as long as the polymer component does not precipitate. In particular, it is known that the coating film uniformity is improved at the time of application to a substrate by appropriately mixing a solvent having a low surface tension, and it is also suitably used in the liquid crystal aligning agent of the present invention. Specific examples of such solvents include ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, ethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-butoxy. 2-propanol, 1-phenoxy-2-propanol, propylene glycol monoacetate, propylene glycol diacetate, propylene glycol-1-monomethyl ether-2-acetate, propylene glycol-1-monoethyl ether-2-acetate, dipropylene Glycol, 2- (2-ethoxypropoxy) propanol, lactate methyl ester, lactate ethyl ester, lactate n-propyl ester, lactate n-butyl ester, lactyl isoamyl ester, etc. It can be mentioned.

  The solid content concentration of the liquid crystal aligning agent of the present invention can be appropriately changed depending on the thickness of the coating film to be formed, but it should be 1 to 10% by mass from the viewpoint of forming a uniform and defect-free thin film. preferable.

  The liquid crystal aligning agent of this invention may contain the other polyamic acid and polyimide which were superposed | polymerized separately in the range which does not impair the effect of this invention. Similarly, a resin other than polyamic acid or polyimide may be contained. In addition, in order to further improve the adhesion of the coating film to the substrate, a known additive such as a silane coupling agent may be added.

  The liquid crystal aligning agent of the present invention obtained as described above can be applied to a substrate, dried and fired to form a film, and this film surface is subjected to an alignment treatment by rubbing and used as a liquid crystal alignment film. Is done.

  The substrate on which the liquid crystal aligning agent is applied is not particularly limited as long as it has high transparency, and a glass substrate or the like can be used. Further, in the reflection type liquid crystal display element, an opaque material such as a silicon wafer can be used as long as the substrate is only on one side, and in this case, a material that reflects light such as aluminum can be used.

  Examples of the method for applying the liquid crystal aligning agent include spin coating, printing, and ink jet methods. From the viewpoint of productivity, transfer printing methods such as flexographic printing are widely used industrially. It is also preferably used in a liquid crystal aligning agent. The liquid crystal aligning agent is preferably used after being filtered through a membrane filter having a pore diameter of 0.1 μm to 1 μm.

  The drying process after applying the liquid crystal aligning agent is not necessarily required, but if the time from application to baking is not constant for each substrate, or if baking is not performed immediately after application, a drying process is included. Is preferred. The drying is not particularly limited as long as the solvent is evaporated to such an extent that the shape of the coating film is not deformed by the conveyance of the substrate or the like. If a specific example is given, the method of drying on a hotplate of 50-150 degreeC, Preferably 80-120 degreeC for 0.5 to 30 minutes, Preferably it is 1 to 5 minutes is taken.

  Although baking after apply | coating a liquid crystal aligning agent can be performed at 100-350 degreeC arbitrary temperatures, Preferably it is 120 to 300 degreeC, More preferably, it is 150 to 250 degreeC. Moreover, even if the liquid crystal aligning agent of this invention is 200 degrees C or less baking, a favorable liquid crystal aligning film can be obtained. This baking can be performed with a hot plate, a hot-air circulating furnace, an infrared furnace, or the like.

  If the thickness of the coating after baking is too thick, it is disadvantageous in terms of power consumption of the liquid crystal display element, and if it is too thin, the reliability of the liquid crystal display element may be lowered. Therefore, it is preferably 5 to 300 nm, and more preferably 10 nm. ~ 100 nm.

  Examples of the material of the rubbing cloth used for the rubbing treatment include cotton, nylon, and rayon.

  The liquid crystal display element of the present invention is a liquid crystal display element obtained by obtaining a substrate with a liquid crystal alignment film from the liquid crystal aligning agent of the present invention by the method described above, and then preparing a liquid crystal cell by a known method.

  To give an example of creating a liquid crystal cell, prepare a pair of substrates on which a liquid crystal alignment film is formed, and spray spacers on the liquid crystal alignment film on one substrate so that the liquid crystal alignment film surface is on the inside. Examples include a method in which the other substrate is bonded and liquid crystal is injected under reduced pressure, or a method in which liquid crystal is dropped on the liquid crystal alignment film surface on which spacers are dispersed and then the substrate is bonded and sealed. The thickness of the spacer at this time is preferably 1 to 30 μm, more preferably 2 to 10 μm.

  The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.

  Abbreviations and structures of tetracarboxylic dianhydrides and diamines used in the synthesis examples are shown below.

The abbreviations of organic solvents used in Synthesis Examples, Examples, etc. are as follows.
NMP: N-methyl-2-pyrrolidone BCS: Butyl cellosolve GBL: γ-butyrolactone DPM: Dipropylene glycol monomethyl ether

<Measurement of molecular weight of polymer>
The molecular weight of the polyimide or polyamic acid in the synthesis example is as follows using a room temperature gel permeation chromatography (GPC) apparatus (GPC-101) manufactured by Shodex Co., Ltd. and a column (KD-803, KD-805) manufactured by Shodex. And measured.
Column temperature: 50 ° C
Eluent: N, N-dimethylformamide (as additives, lithium bromide-hydrate (LiBr • H2O) is 30 mmol / L, phosphoric acid / anhydrous crystal (o-phosphoric acid) is 30 mmol / L, tetrahydrofuran (THF ) Is 10ml / L)
Flow rate: 1.0 mL / standard sample for preparing a calibration curve: TSK standard polyethylene oxide (molecular weight: about 900,000, 150,000, 100,000, 30,000) manufactured by Tosoh Corporation, and polyethylene glycol (molecular weight: about 12,000, 4,000, 1,000) manufactured by Polymer Laboratory.

<Measurement of imidization ratio>
The imidation ratio of polyimide in the synthesis example was measured as follows. Add 20 mg of polyimide powder to an NMR sample tube (NMR sampling tube standard φ5 made by Kusano Kagaku), add 0.53 ml of deuterated dimethyl sulfoxide (DMSO-d ₆ , 0.05% TMS mixture), and completely apply ultrasonic waves. Dissolved. This solution was measured for proton NMR at 500 MHz with an NMR measuring instrument (JNM-ECP500) manufactured by JEOL Ltd. For the imidization rate, protons derived from structures that do not change before and after imidation are determined as reference protons, and the peak integrated value of these protons and the proton peak integrated value derived from the NH group of the amic acid that appears near 10.0 ppm are used. It calculated | required with the following formula | equation.
Imidation ratio (%) = (1−α · x / y) × 100
In the above formula, x is the proton peak integrated value derived from the NH group of the amic acid, y is the peak integrated value of the reference proton, and α is one NH group proton of the amic acid in the case of polyamic acid (imidation rate is 0%). The number ratio of the reference protons.

(Synthesis Example 1)
A polyamic acid solution was prepared by reacting 19.22 g (0.098 mol) of CBDA and 26.43 g (0.1 mol) of DA1 in 259 g of NMP at room temperature for 5 hours. This polyamic acid had a number average molecular weight of about 17,000 and a weight average molecular weight of about 47,000. NMP and BCS are added to 40 g of this polyamic acid solution and stirred. After preparing so that the polyamic acid is 6% by mass, NMP is 74% by mass and BCS is 20% by mass, pressure filtration is performed with a membrane filter having a pore size of 1 μm. And the liquid crystal aligning agent of this invention was obtained.

(Synthesis Example 2)
A polyamic acid solution was prepared by reacting 18.83 g (0.096 mol) of CBDA, 2.64 g (0.01 mol) of DA1, and 17.84 g (0.09 mol) of DA2 in 223 g of NMP at room temperature for 5 hours. This polyamic acid had a number average molecular weight of about 22,000 and a weight average molecular weight of about 55,000. NMP and BCS are added to 40 g of this polyamic acid solution and stirred. After preparing so that the polyamic acid is 6% by mass, NMP is 74% by mass and BCS is 20% by mass, pressure filtration is performed with a membrane filter having a pore size of 1 μm. And the liquid crystal aligning agent of this invention was obtained.

(Synthesis Example 3)
A polyamic acid solution was prepared by reacting 19.02 g (0.097 mol) of CBDA, 7.93 g (0.03 mol) of DA1, and 13.88 g (0.07 mol) of DA2 in 231 g of NMP at room temperature for 5 hours. This polyamic acid had a number average molecular weight of about 20,000 and a weight average molecular weight of about 52,000. NMP and BCS are added to 40 g of this polyamic acid solution and stirred. After preparing so that the polyamic acid is 6% by mass, NMP is 74% by mass and BCS is 20% by mass, pressure filtration is performed with a membrane filter having a pore size of 1 μm. And the liquid crystal aligning agent of this invention was obtained.

(Synthesis Example 4)
A polyamic acid solution was prepared by reacting 19.22 g (0.098 mol) of CBDA, 13.21 g (0.05 mol) of DA1, and 9.91 g (0.05 mol) of DA2 in 240 g of NMP at room temperature for 5 hours. This polyamic acid had a number average molecular weight of about 19,000 and a weight average molecular weight of about 50,000. NMP and BCS are added to 40 g of this polyamic acid solution and stirred. After preparing so that the polyamic acid is 6% by mass, NMP is 74% by mass and BCS is 20% by mass, pressure filtration is performed with a membrane filter having a pore size of 1 μm. And the liquid crystal aligning agent of this invention was obtained.

(Synthesis Example 5)
A polyamic acid solution was prepared by reacting 15.30 g (0.078 mol) of CBDA, 4.36 (0.02 mol) of PMDA, and 26.43 g (0.1 mol) of DA1 in 261 g of NMP at room temperature for 5 hours. This polyamic acid had a number average molecular weight of about 20,000 and a weight average molecular weight of about 53,000. NMP and BCS are added to 40 g of this polyamic acid solution and stirred. After preparing so that the polyamic acid is 6% by mass, NMP is 74% by mass and BCS is 20% by mass, pressure filtration is performed with a membrane filter having a pore size of 1 μm. And the liquid crystal aligning agent of this invention was obtained.

(Synthesis Example 6)
A polyamic acid solution was prepared by reacting 30.03 g (0.1 mol) of TDA, 13.21 g (0.05 mol) of DA1, and 9.91 g (0.05 mol) of DA2 in 301 g of NMP at 50 ° C. for 24 hours. This polyamic acid solution was diluted to 5% by mass with NMP, and 47.4 g of pyridine and 102.0 g of acetic anhydride were further added as an imidization catalyst, followed by reaction at 40 ° C. for 3 hours. This solution was put into 4.2 L of methanol, and the resulting precipitate was filtered off and dried to obtain a white polyimide powder. The resulting polyimide had a number average molecular weight of about 8,000 and a weight average molecular weight of about 24,000. The imidation ratio was 84%. 34.5 g of γ-BL was added to 3 g of the above polyimide powder and dissolved by stirring at 50 ° C. for 20 hours. Γ-BL and DPM are added to this polyimide solution and stirred. After preparing the polyimide to be 6% by mass, γ-BL to be 79% by mass and DPM to be 15% by mass, press with a membrane filter with a pore size of 1 μm. The liquid crystal aligning agent of this invention was obtained by filtering.

(Synthesis Example 7)
A polyamic acid solution was prepared by reacting 19.22 g (0.098 mol) of CBDA, 13.21 g (0.05 mol) of DA1, and 6.11 g (0.05 mol) of DA3 in 218 g of NMP at room temperature for 5 hours. This polyamic acid had a number average molecular weight of about 15,000 and a weight average molecular weight of 39,000. NMP and BCS are added to 40 g of this polyamic acid solution and stirred. After preparing so that the polyamic acid is 6% by mass, NMP is 74% by mass and BCS is 20% by mass, pressure filtration is performed with a membrane filter having a pore size of 1 μm. And the liquid crystal aligning agent of this invention was obtained.

(Synthesis Example 8)
A polyamic acid solution was prepared by reacting 19.22 g (0.098 mol) of CBDA, 13.21 g (0.05 mol) of DA1, and 6.81 (0.05 mol) of DA4 in 222 g of NMP at room temperature for 5 hours. This polyamic acid had a number average molecular weight of about 21,000 and a weight average molecular weight of about 55,000. NMP and BCS are added to 40 g of this polyamic acid solution and stirred to prepare a polyamic acid of 5 mass%, NMP of 75 mass%, and BCS of 20 mass%, followed by pressure filtration with a membrane filter having a pore diameter of 1 μm. And the liquid crystal aligning agent of this invention was obtained.

(Synthesis Example 9)
A polyamic acid solution was prepared by reacting 19.22 g (0.098 mol) of CBDA, 13.21 g (0.05 mol) of DA1, and 24.83 g (0.05 mol) of DA5 in 325 g of NMP at room temperature for 5 hours. This polyamic acid had a number average molecular weight of about 30,000 and a weight average molecular weight of about 69,000. NMP and BCS are added to 40 g of this polyamic acid solution and stirred. After preparing so that the polyamic acid is 4% by mass, NMP is 76% by mass and BCS is 20% by mass, pressure filtration is performed with a membrane filter having a pore size of 1 μm. And the liquid crystal aligning agent of this invention was obtained.

(Synthesis Example 10)
30.03 g (0.1 mol) of TDA, 7.93 g (0.03 mol) of DA1, and 13.88 g (0.07 mol) of DA2 were reacted in 294 g of NMP at 50 ° C. for 24 hours to prepare a polyamic acid solution. This polyamic acid solution was diluted to 5% by mass with NMP, 47.5 g of pyridine and 102.1 g of acetic anhydride were further added as an imidization catalyst, and the mixture was reacted at 40 ° C. for 3 hours. This solution was put into 4.2 L of methanol, and the resulting precipitate was filtered off and dried to obtain a white polyimide powder. The resulting polyimide had a number average molecular weight of about 9,000 and a weight average molecular weight of about 46,000. The imidation ratio was 80%. 34.5 g of γ-BL was added to 3 g of the above polyimide powder and dissolved by stirring at 50 ° C. for 20 hours. Γ-BL and DPM are added to this polyimide solution and stirred. After preparing the polyimide to be 6% by mass, γ-BL to be 79% by mass and DPM to be 15% by mass, press with a membrane filter with a pore size of 1 μm. The liquid crystal aligning agent of this invention was obtained by filtering.

(Comparative Synthesis Example 1)
A polyamic acid solution was prepared by reacting 18.63 g (0.095 mol) of CBDA and 19.83 g (0.1 mol) of DA2 in 218 g of NMP at room temperature for 5 hours. This polyamic acid had a number average molecular weight of about 38,000 and a weight average molecular weight of about 67,000. NMP and BCS are added to 40 g of this polyamic acid solution and stirred. After preparing so that the polyamic acid is 6% by mass, NMP is 74% by mass and BCS is 20% by mass, pressure filtration is performed with a membrane filter having a pore size of 1 μm. Thus, a liquid crystal aligning agent for comparison was obtained.

(Comparative Synthesis Example 2)
A polyamic acid solution was prepared by reacting 30.03 g (0.1 mol) of TDA and 19.83 g (0.1 mol) of DA2 in 283 g of NMP at 50 ° C. for 24 hours. This polyamic acid solution was diluted to 5% by mass with NMP, 47.5 g of pyridine and 102.1 g of acetic anhydride were further added as an imidization catalyst, and the mixture was reacted at 40 ° C. for 3 hours. This solution was put into 4.0 L of methanol, and the resulting precipitate was filtered off and dried to obtain a white polyimide powder. The resulting polyimide had a number average molecular weight of about 14,000 and a weight average molecular weight of about 49,000. The imidation ratio was 81%. 34.5 g of γ-BL was added to 3 g of the above polyimide powder and dissolved by stirring at 50 ° C. for 20 hours. Γ-BL and DPM are added to this polyimide solution and stirred. After preparing the polyimide to be 6% by mass, γ-BL to be 79% by mass and DPM to be 15% by mass, press with a membrane filter with a pore size of 1 μm. Filtration was performed to obtain a liquid crystal aligning agent for comparison.

Example 1
Using the liquid crystal aligning agent obtained in Synthesis Example 1, the following evaluation was performed.

<Evaluation of rubbing resistance>
A liquid crystal aligning agent is spin-coated on a glass substrate with an ITO electrode, dried on a hot plate at 80 ° C. for 5 minutes, and then baked in a 120 ° C. hot air circulating oven for 60 minutes to form a coating film having a thickness of 100 nm. I let you. Using a rubbing machine with a roll diameter of 120 mm, to which the rayon cloth YA-20-R (manufactured by Yoshikawa Chemical Co., Ltd.) was attached, this coating surface was rolled at a rotational speed of 300 rpm, a roll traveling speed of 20 mm / sec, and an indentation amount of 0.5 mm The substrate was rubbed under the above conditions to obtain a substrate with a liquid crystal alignment film. When this liquid crystal alignment film surface was observed with a real-time scanning laser microscope 1LM21D (objective lens 10 times, magnification on the monitor 340 times) manufactured by Lasertec Co., Ltd., no abnormalities such as scratches and film peeling were observed. .

<Evaluation of liquid crystal alignment>
A liquid crystal aligning agent is spin-coated on a glass substrate with an ITO electrode, dried on a hot plate at 80 ° C. for 5 minutes, and then baked in a 120 ° C. hot air circulating oven for 60 minutes to form a coating film having a thickness of 100 nm. I let you. Using a rubbing machine with a roll diameter of 120 mm, to which the rayon cloth YA-20-R (manufactured by Yoshikawa Chemical Co., Ltd.) was attached, this coating surface was rolled at a rotational speed of 300 rpm, a roll traveling speed of 20 mm / sec, and an indentation amount of 0.5 mm The substrate was rubbed under the above conditions to obtain a substrate with a liquid crystal alignment film.

  Two substrates with this liquid crystal alignment film are prepared, and a 6 μm spacer is sprayed on the surface of one liquid crystal alignment film, and then a sealant is printed thereon. After laminating so that the facing rubbing direction was orthogonal, the sealing agent was cured to produce an empty cell. Liquid crystal MLC-2003 (Merck Japan Co., Ltd.) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain a twisted nematic liquid crystal cell. When this liquid crystal cell was observed under a microscope under crossed Nicols (200 times), it was confirmed that the liquid crystal was uniformly aligned without alignment failure.

<Measurement of pretilt angle>
The liquid crystal cell produced above was evaluated using a liquid crystal pretilt angle measuring device TBA-107 (manufactured by Autronic-MELCHERS GmbH). As a result, the pretilt angle of the liquid crystal was 0.7 degrees.

(Example 2)
Evaluation was performed in the same manner as in Example 1 except that the liquid crystal aligning agent obtained in Synthesis Example 1 was used and the firing temperature was set to 150 ° C. As a result, abnormalities such as scratches and film peeling were not observed on the surface of the liquid crystal alignment film after rubbing. Further, it was confirmed that the liquid crystal cell had no alignment defect and the liquid crystal was uniformly aligned. The pretilt angle of the liquid crystal was 0.8 degrees.

(Example 3)
Evaluation was performed in the same manner as in Example 1 except that the liquid crystal aligning agent obtained in Synthesis Example 1 was used and the baking temperature was set to 180 ° C. As a result, abnormalities such as scratches and film peeling were not observed on the surface of the liquid crystal alignment film after rubbing. Further, it was confirmed that the liquid crystal cell had no alignment defect and the liquid crystal was uniformly aligned. The pretilt angle of the liquid crystal was 0.8 degrees.

Example 4
Evaluation was performed in the same manner as in Example 1 except that the liquid crystal aligning agent obtained in Synthesis Example 2 was used and the firing temperature was set to 150 ° C. As a result, abnormalities such as scratches and film peeling were not observed on the surface of the liquid crystal alignment film after rubbing. Further, it was confirmed that the liquid crystal cell had no alignment defect and the liquid crystal was uniformly aligned. The pretilt angle of the liquid crystal was 1.0 degree.

(Example 5)
Evaluation was performed in the same manner as in Example 1 except that the liquid crystal aligning agent obtained in Synthesis Example 3 was used and the baking temperature was set to 150 ° C. As a result, abnormalities such as scratches and film peeling were not observed on the surface of the liquid crystal alignment film after rubbing. Further, it was confirmed that the liquid crystal cell had no alignment defect and the liquid crystal was uniformly aligned. The pretilt angle of the liquid crystal was 1.0 degree.

(Example 6)
Evaluation was performed in the same manner as in Example 1 except that the liquid crystal aligning agent obtained in Synthesis Example 4 was used and the baking temperature was set to 150 ° C. As a result, abnormalities such as scratches and film peeling were not observed on the surface of the liquid crystal alignment film after rubbing. Further, it was confirmed that the liquid crystal cell had no alignment defect and the liquid crystal was uniformly aligned. The pretilt angle of the liquid crystal was 1.0 degree.

(Example 7)
Evaluation was performed in the same manner as in Example 1 except that the liquid crystal aligning agent obtained in Synthesis Example 5 was used and the baking temperature was set to 150 ° C. As a result, abnormalities such as scratches and film peeling were not observed on the surface of the liquid crystal alignment film after rubbing. Further, it was confirmed that the liquid crystal cell had no alignment defect and the liquid crystal was uniformly aligned. The pretilt angle of the liquid crystal was 0.7 degrees.

(Example 8)
Evaluation was performed in the same manner as in Example 1 except that the liquid crystal aligning agent obtained in Synthesis Example 6 was used and the baking temperature was set to 150 ° C. As a result, abnormalities such as scratches and film peeling were not observed on the surface of the liquid crystal alignment film after rubbing. Further, it was confirmed that the liquid crystal cell had no alignment defect and the liquid crystal was uniformly aligned. The pretilt angle of the liquid crystal was 1.0 degree.

Example 9
Evaluation was performed in the same manner as in Example 1 except that the liquid crystal aligning agent obtained in Synthesis Example 7 was used and the baking temperature was set to 150 ° C. As a result, abnormalities such as scratches and film peeling were not observed on the surface of the liquid crystal alignment film after rubbing. Further, it was confirmed that the liquid crystal cell had no alignment defect and the liquid crystal was uniformly aligned. The pretilt angle of the liquid crystal was 0.8 degrees.

(Example 10)
Evaluation was performed in the same manner as in Example 1 except that the liquid crystal aligning agent obtained in Synthesis Example 8 was used and the firing temperature was 150 ° C. As a result, abnormalities such as scratches and film peeling were not observed on the surface of the liquid crystal alignment film after rubbing. Further, it was confirmed that the liquid crystal cell had no alignment defect and the liquid crystal was uniformly aligned. The pretilt angle of the liquid crystal was 0.8 degrees.

(Example 11)
Evaluation was performed in the same manner as in Example 1 except that the liquid crystal aligning agent obtained in Synthesis Example 9 was used and the firing temperature was set to 150 ° C. As a result, abnormalities such as scratches and film peeling were not observed on the surface of the liquid crystal alignment film after rubbing. Further, it was confirmed that the liquid crystal cell had no alignment defect and the liquid crystal was uniformly aligned. The pretilt angle of the liquid crystal was 1.0 degree.

(Example 12)
Evaluation was performed in the same manner as in Example 1 except that the liquid crystal aligning agent obtained in Synthesis Example 10 was used and the baking temperature was set to 150 ° C. As a result, abnormalities such as scratches and film peeling were not observed on the surface of the liquid crystal alignment film after rubbing. Further, it was confirmed that the liquid crystal cell had no alignment defect and the liquid crystal was uniformly aligned. The pretilt angle of the liquid crystal was 1.0 degree.

(Comparative Example 1)
Evaluation was performed in the same manner as in Example 1 except that the liquid crystal aligning agent obtained in Comparative Synthesis Example 1 was used and the firing temperature was set to 150 ° C. As a result, many scratches were observed on the surface of the liquid crystal alignment film after rubbing.

(Comparative Example 2)
Evaluation was performed in the same manner as in Example 1 except that the liquid crystal aligning agent obtained in Comparative Synthesis Example 2 was used and the firing temperature was set to 150 ° C. As a result, many scratches were observed on the surface of the liquid crystal alignment film after rubbing.

  The liquid crystal aligning agent of the present invention is excellent in rubbing resistance even at a low temperature baking of 200 ° C. or lower, and a liquid crystal alignment film having uniform alignment of liquid crystals and no alignment failure can be obtained. It can also be suitably used for a liquid crystal display element using a plastic substrate.

Claims (4)

A polyamic acid obtained by polymerizing a diamine component represented by the following formula [1] and a tetracarboxylic dianhydride component represented by the following formula [2], or dehydrating and ring-closing this polyamic acid A liquid crystal aligning agent containing at least one polymer of the obtained polyimide, wherein the tetracarboxylic dianhydride component includes tetracarboxylic dianhydride having an alicyclic structure in R2 of the formula [2]. And a diamine represented by the following formula [3] is contained in the diamine component.

(Wherein R1 is a divalent organic group)

(Wherein R2 is a tetravalent organic group)

(In the formula, n is an integer of 1 to 20, and R3 is a hydrogen atom or a methyl group)   The liquid crystal aligning film obtained from the liquid crystal aligning agent of Claim 1. The liquid crystal aligning film obtained by apply | coating the liquid crystal aligning agent of Claim 1 to a board | substrate, baking at the temperature of 200 degrees C or less, and rubbing.   The liquid crystal display element which has a liquid crystal aligning film of Claim 2 or Claim 3.