TWI490253B - Liquid crystal alignment agent, liquid crystal alignment film. and liquid crystal display device - Google Patents

Description

Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element

The present invention relates to a polyoxyalkylene oxide, and more particularly to a liquid crystal alignment agent containing polysiloxane, a liquid crystal alignment film made of the liquid crystal alignment agent, and a liquid crystal display element comprising the liquid crystal alignment film.

The operation principle of the liquid crystal display is to change the alignment state of the liquid crystal molecules by using an external electric field, thereby causing the polarization state and direction of the light to change, thereby obtaining a display effect of light and dark contrast. Due to its small size, light weight, low power consumption and good display quality, liquid crystal displays have become the mainstream of flat panel displays in recent years.

As the size of the screen has expanded, liquid crystal display elements having thin filmed transistors (TFTs) in each of the pixels have been developed. When liquid crystal molecules are placed between a pair of substrates containing electrodes, since the liquid crystals have different electric induction rates in the direction of parallel and perpendicular molecules, the arrangement of liquid crystal molecules can be controlled by controlling the electric field. On the other hand, since the liquid crystal molecules have birefringence characteristics, the polarization direction of the polarized light can be regulated by the change in the alignment state of the liquid crystal molecules.

In order to allow the liquid crystal molecules to have a uniform tilt angle and a fixed orientation on the substrate, an alignment film is coated on the substrate, and the alignment film is used to control the alignment direction of the liquid crystal molecules and provide The liquid crystal molecules have a stable pretilt angle, and when the applied electric field is turned off, the liquid crystal molecules return to the original arrangement by the anchoring force at the interface with the alignment film and its own elasticity.

At present, the typical method for preparing an alignment film in the industry is to apply an organic film on a substrate table. On the surface, the molecules on the surface of the film are oriented by friction or other means, whereby the subsequently placed liquid crystal molecules are tilted in a fixed direction. The material of the organic film may be selected from the group consisting of polyvinyl alcohol, polyethylene glycol, polyamidamine, polyaminic acid or polyimine, wherein the polyamic acid and the polyimide have excellent thermal stability and good mechanical properties. Electrical and chemical resistance are often used as alignment film materials. Polylysine is a polymer obtained by polymerization of a diamine and a tetracarboxylic acid or a diamine and a tetracarboxylic dianhydride, and the polyimine is generally subjected to a high temperature dehydration ring closure reaction by polyamic acid. Made by.

The voltage holding ratio and the case where the voltage of the liquid crystal display element is decremented in the open state are turn off. For an active array driven liquid crystal display element, when a pixel temporarily does not display a picture, the circuit of the pixel will be in an open state and start to discharge. If the voltage holding rate of the element is not high, between the electrodes The voltage value will decrease instantaneously, causing the alignment of the liquid crystal molecules to become messy, resulting in poor image quality. Therefore, in order to present high-quality images, the voltage retention rate is an important index, which must be high and uniform.

The present invention provides a liquid crystal alignment agent, a liquid crystal alignment film produced using the liquid crystal alignment agent, and a liquid crystal display element including the liquid crystal alignment film. The voltage holding ratio of such a liquid crystal display element can be higher than that of a conventional one.

The liquid crystal alignment agent of the present invention comprises polyoxyalkylene oxide represented by the following average composition formula: R ¹ _a R ² _b R ³ _c SiZ _(4-abc)/2 , wherein Z is O, -C _n H _2n - or a combination thereof, n is an integer of 1 to 4, R ¹ is a C ₁ - C ₄₀ hydrocarbon group, R ² is a structure having an epoxy group, and R ³ is a structure having a liquid crystal group, 0 < b < 1, 0 < c < 0.5, and 0.5 < (4-abc) / 2 < 1.5.

In an embodiment of the invention, at least one hydrogen atom on the structure having a liquid crystal group is substituted with a fluorine atom.

In an embodiment of the invention, the structure having a liquid crystal group is a structure represented by the following formula: *-C ₂ H ₄ -Q ¹ -A ¹ -Z ¹ -A ² -Q ² , wherein A ¹ and A ² They are respectively substituted phenyl, phenyl, cyclohexyl, dicyclohexyl or cyclohexyl phenyl; Z ¹ is a single bond, -CH=CH-, -C≡C-, -O -, -COO- or a substituted C ₁ -C ₁₀ alkyl group, wherein the non-adjacent -CH ₂ - may each independently be -CH=CH-, -C≡C-, -O- or -COO -Substitution; Q ¹ is a single bond, -CH=CH-, -C≡C-, -O-, -COO- or a C ₁ -C ₁₀ alkyl group which may be substituted, wherein -CH ₂ - is not adjacent Each may independently be substituted with -CH=CH-, -C≡C-, -O- or -COO-; Q ² is H, F or a C ₁ -C ₁₀ alkyl group which may be substituted, wherein are not adjacent -CH ₂ - may each independently be substituted with -CH=CH-, -C≡C-, -O- or -COO-; and * is the structure having the liquid crystal group and the germanium atom of the polyoxyalkylene The bonding position.

In an embodiment of the invention, the structure having a liquid crystal group is a structure represented by Formula 1: Formula 1, wherein R ⁴ is a single bond or a C ₁ -C ₂₀ alkylene group, a C ₆ -C ₂₀ phenylene group, a C ₆ -C ₂₀ cyclohexylene group, a C ₆ -C ₂₀ fluorophenyl group, a C ₆ -C ₂₀ fluorocyclohexyl or a combination of the above, R ⁵ is C ₁ -C ₂₀ alkyl, C ₆ -C ₂₀ phenyl, C ₆ -C ₂₀ cyclohexyl, C ₆ -C ₂₀ fluorobenzene a group, a C ₆ -C ₂₀ fluorocyclohexyl group or a combination of the above groups, wherein m and p are each an integer of 0 to 4, and * is a bonding position of the structure represented by Formula 1 to the ruthenium atom of the polyoxyalkylene oxide; .

In an embodiment of the invention, the structure having a liquid crystal group is a structure represented by Formula 2: Formula 2, wherein * represents the bonding position of the structure represented by Formula 2 to the ruthenium atom of the polyoxyalkylene.

In an embodiment of the invention, the structure having an epoxy group is a structure represented by Formula 3 or Formula 4: Equation 3, Formula 4 wherein R ⁶ , R ⁷ and R ⁸ are each a C ₁ - C ₁₀ alkyl group, and * is a bonding position of a structure represented by Formula 3 or Formula 4 with a ruthenium atom of the polyoxyalkylene.

In an embodiment of the invention, c/b < 1.

In an embodiment of the invention, the liquid crystal alignment agent further comprises a polyimide and a polyimide precursor, wherein the polyoxyalkylene has a solid content ratio of 0.05% by weight to 5% by weight in the liquid crystal alignment agent, It is preferably from 0.1% by weight to 1% by weight.

The liquid crystal alignment film of the present invention is obtained by applying the aforementioned liquid crystal alignment agent onto a substrate.

The liquid crystal display element of the present invention includes the aforementioned liquid crystal alignment film.

In summary, the present invention provides a liquid crystal alignment agent comprising a polyoxyalkylene oxide, and a structure having an epoxy group and a structure having a liquid crystal group are grafted onto the polyoxyalkylene. By using the liquid crystal alignment agent to form a liquid crystal alignment film of a liquid crystal display element, the display performance can be improved.

The above described features and advantages of the present invention will be more apparent from the following description.

Herein, if a group is not specifically indicated to be substituted, the group may represent a substituted or unsubstituted group. For example, "alkyl" can mean a substituted or unsubstituted alkyl group. Further, when a group crown is described by "Cx", it means that the main chain of the group has X carbon atoms.

In this context, the structure of a compound is sometimes represented by a skeleton formula. This representation can omit carbon atoms, hydrogen atoms, and carbon-hydrogen bonds. Of course, if the functional group is clearly drawn in the structural formula, the manufacturer will prevail.

In the present specification, the range represented by "a value to another value" is a schematic representation that avoids enumerating all the values in the range in the specification. Therefore, the recitation of a particular range of values is intended to include any value in the range of values and the range of values defined by any value in the range of values, as in the specification. The scope is the same. For example, the range of "0.1% by weight to 1% by weight" covers the range of "0.5% by weight to 0.8% by weight" regardless of whether other values are listed in the specification.

The first embodiment of the present invention proposes a liquid crystal alignment agent containing a polyoxyalkylene represented by the following average composition formula: R ¹ _a R ² _b R ³ _c SiZ _(4-abc)/2 . In the formula, Z is O, -C _n H _2n - or a combination thereof, n is an integer of 1 to 4; R ¹ is a C ₁ - C ₄₀ hydrocarbon group; R ² is a structure having an epoxy group; and R ³ is a The structure of the liquid crystal group; 0 < b <1; 0 < c <0.5; and 0.5 < (4-abc) / 2 < 1.5.

In this embodiment, the structure R ² having an epoxy group means any structure containing an epoxy group, for example, a structure represented by Formula 3 or Formula 4: Equation 3, Formula 4, wherein R ⁶ , R ⁷ and R ⁸ are each a C ₁ - C ₁₀ alkyl group, and * is a bonding position of a structure represented by Formula 3 or Formula 4 with a certain argon atom in the polyoxyalkylene. In the embodiment, the "mesogenic unit" in the "structure having a liquid crystal group" means a structure capable of causing a molecule to form a liquid crystal state in a molecular structure, which may have a ring composed of a benzene ring or a cyclohexane ring. Double loop structure. For example, the structure having a liquid crystal group may be a structure represented by the following formula: *-C ₂ H ₄ -Q ¹ -A ¹ -Z ¹ -A ² -Q ² , wherein A ¹ and A ² are respectively replaceable Phenyl, phenyl, cyclohexyl, dicyclohexyl or cyclohexylphenyl; Z ¹ is a single bond, -CH=CH-, -C≡C-, -O-, -COO- or Substitutable C ₁ -C ₁₀ alkyl, wherein the non-adjacent -CH ₂ - may each independently be -CH=CH-, -C≡C-, -O- or -COO-substituted; Q ¹ is a single bond, -CH=CH-, -C≡C-, -O-, -COO- or a C ₁ -C ₁₀ alkyl group which may be substituted, wherein the non-adjacent -CH ₂ - may each independently be - CH=CH-, -C≡C-, -O- or -COO-substituted; Q ² is H, F or a C ₁ -C ₁₀ alkyl group which may be substituted, wherein the non-adjacent -CH ₂ - may each Independently substituted with -CH=CH-, -C≡C-, -O- or -COO-; and * is the bonding position of the liquid crystal group structure to the germanium atom of the polyoxyalkylene.

More specifically, the structure having a liquid crystal group may be a structure represented by Formula 1: Formula 1, wherein R ⁴ is a single bond or a C ₁ -C ₂₀ alkylene group, a C ₆ -C ₂₀ phenylene group, a C ₆ -C ₂₀ cyclohexylene group, a C ₆ -C ₂₀ fluorophenyl group, a C ₆ -C ₂₀ fluorocyclohexyl or a combination of the above, R ⁵ is C ₁ -C ₂₀ alkyl, C ₆ -C ₂₀ phenyl, C ₆ -C ₂₀ cyclohexyl, C ₆ -C ₂₀ fluorobenzene a group, a C ₆ -C ₂₀ fluorocyclohexyl group or a combination of the above groups, wherein m and p are each an integer of 0 to 4, and * is a bond of a structure represented by Formula 1 to a certain ruthenium atom in the polysiloxane. position.

A specific example of the "liquid crystal-based structure" is a structure represented by Formula 2: Formula 2, wherein * represents the bonding position of the structure represented by Formula 2 to a certain atom of a polyoxyalkylene.

The above polyoxaxane represented by the average composition formula R ¹ _a R ² _b R ³ _c SiZ _(4-abc)/2 can be used to impart an epoxy group-containing compound and a liquid crystal group-containing compound by a general grafting method. The reaction is carried out with any polyoxyalkylene to graft an "epoxy structure" and a "liquid crystal group structure" onto the main chain of the polyoxyalkylene. The grafting method is, for example, a hydrogenation reaction by hydrazine. Under this premise, the polyoxyalkylene to be grafted should contain a hydrogen bond (or alkenyl group), and the compound having an epoxy group and the compound having a liquid crystal group should contain Alkenyl (or hydrazine hydrogen).

In the present embodiment, the liquid crystal alignment agent may contain other alignment polymers in addition to polyoxymethane, such as polyglycine (also known as polyimine precursor), polyimine, polyfluorene. Mixture of aminic acid and polyimine, polyphthalate, polyester, polyamine, cellulose derivative, polyacetal, polystyrene derivative, poly(styrene-phenyl malayan Amine derivatives, poly(meth)acrylates, and the like.

Further, the liquid crystal alignment agent may also contain an organic sulfonium (oxy) alkane compound different from the above polysiloxane and an epoxy compound.

The organic oxime (oxy) alkane compound may, for example, be aminopropyltrimethoxydecane, aminopropyltriethyldecane, vinylmethylnonane, N-(2-aminoethyl)-3-aminopropyl Methyldimethoxydecane, N-(2-aminoethyl)-3-aminopropyltrimethoxydecane, vinyltriethoxydecane, 3-methylpropenyloxypropyltrimethyl Oxydecane, 3-glycidoxypropyltrimethoxydecane, 3-glycidoxypropylmethyldimethoxydecane, 2-(3,4-epoxycyclohexyl)ethyl Trimethoxydecane, 3-ureidopropyltrimethoxydecane, 3-ureidopropyltriethoxydecane, N-ethoxycarbonyl-3-aminopropyltrimethoxydecane, N-ethoxycarbonyl 3-aminopropyltriethoxyamine decane, N-triethyl Oxymethyl methacrylate propyl triethylamine, N-trimethoxymethyl propyl propyl triethylamine, N-bis (oxyethyl)-3-aminopropyl trimethoxy Decane, N-bis(oxyethyl)-3-aminopropyltriethyldecane.

The epoxy compound may be, for example, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin. Diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, 1,3,5,6-tetraglycidyl-2,4-hexanediol, N,N,N ' ,N ' -tetraglycidyl-m-phenylene, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N ' ,N ' -tetraglycidyl-4 , 4 ' -diaminodiphenylmethane, 3-(N-allyl-N-glycidyl)aminopropyltrimethoxydecane, 3-(N,N-diglycidyl)amine Propyltrimethoxydecane.

Further, the liquid crystal alignment agent may also contain a solvent such as N-methyl-2-pyrrolidinone (NMP), γ-butyrolactone or butylcellosolve.

The proportion of the polyoxyalkylene represented by the above average composition formula in the liquid crystal alignment agent is not limited in principle, but in view of the effect of the polyoxyalkylene on the alignment film (described in detail below), the amount is not suitable. Too low; considering that polyoxyalkylene may reduce the wettability of the liquid crystal alignment agent as a whole, the amount thereof is not too high, therefore, it is preferable that the ratio of the solid content is between 0.05% by weight and 5% by weight. For example, 0.1% by weight to 1% by weight.

A second embodiment of the present invention provides a liquid crystal alignment film which can be produced by applying the liquid crystal alignment agent according to the first embodiment to a substrate.

In general, the film thickness of the liquid crystal alignment film formed by the above method is preferably from 0.005 μm to 0.5 μm. The thickness of the liquid crystal alignment film is usually adjusted according to the viscosity of the liquid crystal alignment agent and the coating method of the liquid crystal alignment agent. Further, the thickness of the liquid crystal alignment film can be measured by a conventional film thickness measuring device such as a step meter or an ellipsometer.

In the present embodiment, any conventionally known substrate can be used as the substrate, and it is preferable to be able to withstand the processing conditions described later. For example, a plastic substrate, a glass epoxy substrate, a glass substrate, a ceramic substrate, a metal substrate, etc. are mentioned.

Examples of the material of the plastic substrate include a thermosetting resin (for example, an epoxy resin, a phenol resin, a polyimide resin, a polyester resin, etc.), and a thermoplastic resin (for example, phenoxy resin, polyether oxime, polyfluorene, polyphenylene). Polyphenylene sulfone, etc.).

Examples of the material of the ceramic substrate include alumina, aluminum nitride, zirconium oxide, ruthenium, tantalum nitride, tantalum carbide, and the like.

Examples of the material of the glass substrate include soda glass, potassium glass, borosilicate glass, quartz glass, aluminosilicate glass, lead glass, and the like.

Examples of the material of the metal substrate include aluminum, zinc, copper, and the like.

Further, the substrate may have a structure in which two or more layers of the above-mentioned plastic substrate, glass substrate, ceramic substrate, and metal substrate are laminated. Of course, it may be a substrate having a patterned transparent conductive film.

In the present embodiment, examples of the method of applying the liquid crystal alignment agent onto the substrate include a roll coating method, a spin coating method, a printing method, and the like.

Further, in the present embodiment, the liquid crystal alignment agent may be fired after being applied onto the substrate, and the firing method is, for example, heat baking, and the heating baking method may be exemplified by an oven or an infrared oven. A method of performing heat treatment, a method of performing heat treatment on a hot plate, or the like. The organic solvent in the liquid crystal alignment agent can be removed by heat baking, and if the liquid crystal alignment agent contains polylysine, it can also be subjected to a dehydration ring closure reaction. In the present embodiment, the heating and baking temperature is preferably from 80 ° C to 300 ° C, more preferably from 100 ° C to 240 ° C, and most preferably from 120 ° C to 220 ° C.

A third embodiment of the present invention provides a liquid crystal display element including a second implementation The liquid crystal alignment film described in the mode. As for the method for producing a liquid crystal display device, for example, the liquid crystal alignment agent described in the first embodiment is applied to a substrate, and then the substrate is heated and baked to form a liquid crystal alignment film. The substrate is, for example, a substrate for a liquid crystal display element, and the material thereof is, for example, the material exemplified in the second embodiment. Further, the method of coating and the method of heat baking may be carried out using the methods exemplified in the second embodiment, and any other conventional methods may be used.

Next, in the present embodiment, after the liquid crystal alignment film is formed, for example, rubbing can be performed by a roller wound with a nylon or cotton fiber cloth, so that the liquid crystal alignment film can provide liquid crystal molecular alignment.

Then, in the present embodiment, a sealant is coated on a substrate having the liquid crystal alignment film, and a spacer is sprayed on another substrate having the liquid crystal alignment film, and then the two liquid crystal alignment film substrates are brushed toward each other. The liquid crystal display elements are initially formed by combining liquid crystal display elements by injecting liquid crystals into the gaps and sealing the injection holes. The process of subsequently completing the liquid crystal display element is well known to those skilled in the art and will not be described herein.

<experiment>

The present invention will be more specifically described below with reference to experimental examples. Although the following experiments are described, the materials used, the amounts and ratios thereof, the processing details, the processing flow, and the like can be appropriately changed without departing from the scope of the invention. Therefore, the invention should not be construed restrictively by the experiments described below.

In the experimental examples, various epoxy group-containing compounds and various liquid crystal group-containing compounds were used, and an epoxy group-containing structure and a liquid crystal group-containing structure were grafted to various commercially available polyfluorenes by a hydrogenation reaction. On the oxane, the polydecane oxide of Synthesis Example 1 to Synthesis Example 6 is obtained, wherein the product name, composition formula or structural formula of a commercially available polysiloxane, a compound having an epoxy group, and a compound having a liquid crystal group are as follows : Polyoxane

In each of the synthesis examples, the hydrazine hydrogenation reaction was carried out to such an extent that the hydrazine hydrogen bond on the initial polyoxane was depleted. If a compound having an epoxy group and a compound having a liquid crystal group are simultaneously added, the molar ratio of the former and the latter is 9:1 in all the synthesis examples. The synthesis example 6 will be described below, and the synthesis scheme of the other synthesis examples is similar to the synthesis example 6.

In a reactor equipped with a magnet, a dropping funnel, a thermometer and a reflux condenser, 21.76 g (containing 0.166 mole Si-H) of H3 (weight average molecular weight of 7380), 0.01536 was added. Pt of g and 16.61 g of toluene were heated to 120 ° C and mixed well. Next, 5.25 g (0.0166 mole) of V2PGP1 was slowly dropped from the dropping funnel at a rate of 0.5 g per minute, and after completion of completion, the hydrogenation reaction was carried out at 120 ° C for 5 hours. Next, 17.07 g (0.15 mole) of AGE was slowly added from the dropping funnel to the reaction vessel, and a hydrogenation reaction was carried out at 125 ° C for 3 hours. After completion of the reaction, the reaction vessel was cooled to room temperature, vacuumed, and further heated to 110 ° C for purification, and toluene was distilled off.

IR analysis of the organic oxane product showed no absorption signal near the absorption peak at 2100 cm ^-1 , confirming that the Si-H position has been replaced by a liquid crystal group and an epoxy group. The polystyrene-equivalent weight average molecular weight was measured by a gel permeation method using dimethylformamide (DMF) as a developing solvent, and it was confirmed that there were no small molecules (epoxy-based compounds and liquid crystal-based compounds). Residual.

Table 1 lists the raw materials of the polysiloxanes of Synthesis Examples 1 to 6 and the weight average molecular weight after the reaction. Among them, the polysiloxanes of Synthesis Example 1 and Synthesis Example 2 include a structure having an epoxy group, and the polysiloxanes of Synthesis Examples 3 to 6 include both an epoxy group-containing structure and a liquid crystal group-containing structure.

Voltage retention

Taking the polyoxyalkylene of Synthesis Example 1 at 0% (Comparative Example 1-1) and 0.1% (Experimental Example) The relative solid contents of 1-1), 0.3% (Experimental Example 1-2), 0.5% (Experimental Example 1-3), and 1% (Experimental Example 1-4) were respectively added to polyamic acid solution RA 9002-N2 And RA 9002-V4 (produced by Daxing Materials), and diluted with N-methylpyrrolidone (NMP) / ethylene glycol butyl ether (BC) in a weight ratio of 1:1 to a solid content of 6.5 wt% Liquid crystal alignment agent. The liquid crystal alignment agent prepared as described above was coated on a glass substrate with an ITO transparent electrode, prebaked on a hot plate at 85 ° C for 135 seconds, and then placed in an oven at 230 ° C for 30 minutes to form a thickness of 1000 ± 100. Å film (ie liquid crystal alignment film). Finally, a pair of substrates on which the liquid crystal alignment film is formed are combined with a liquid crystal (purchased from Merck, model LCT11506) by a conventional method to obtain a liquid crystal layer containing a pair of alignment films sandwiched between the pair of alignment films and a pair of respectively A liquid crystal display element disposed on the pair of electrode layers on the side of the liquid crystal layer.

The liquid crystal display elements of Comparative Example 1-2 and Experimental Example 1-5 to Experimental Example 1-8 were prepared in the same manner, but in the course of the process, the polyoxoxane of Synthesis Example 1 was replaced with the polyoxoxane of Synthesis Example 2, The polyaminic acid solution RA 9002-N2 was replaced by a poly-proline solution RA 9002-V4 (manufactured by Daxing Materials).

The liquid crystal display elements of Comparative Example 1-1, Comparative Example 1-2, and Experimental Example 1-1 to Experimental Example 1-8 were placed in an oven at 60 ° C, and a frequency of 0.6 Hz and a wave height of ±5 V (or ±1 V) were applied to the source. A rectangular wave with a pulse width of 60 microseconds is measured, and the voltage value after the application is released to 1667 milliseconds is measured. The voltage holding ratio (VHR) of the liquid crystal display element = the voltage value/applied voltage value × 100% from the release of the application to 1667 msec, and the results are summarized in Table 1.

Comparing the results of Table 2, it is understood that the addition of the polydecane oxide of Synthesis Example 1 or Synthesis Example 2 to the polyaminic acid solution increases the VHR of the liquid crystal display element at 1 V and 5 V as the addition ratio increases. . It is apparent that the polyoxyalkylene having an epoxy group in the alignment film can enhance the electrical performance of the liquid crystal display element.

The polyoxane of the above Synthesis Example 3 was separately added to the polyproline solution DA-1109 (manufactured by Daxing Materials), and N-methylpyrrolidone/ethylene glycol butylate was used in a weight ratio of 10:55:35. The ether/γ-butyrolactone mixed solvent was diluted to a liquid crystal alignment agent having a solid content of 5.12 wt%, and the liquid crystal alignment agent was coated on a glass substrate with an ITO transparent electrode, and prebaked on a hot plate at 85 ° C. After the second, it was placed in an oven at 230 ° C for 30 minutes to form a film having a thickness of 1000 ± 100 Å. A rubbing orientation is then performed on the film to form a horizontal alignment film. Finally, a pair of substrates on which the alignment film is formed are combined with a liquid crystal (available from Merck, model number 84546) by a conventional method to obtain a liquid crystal layer containing a pair of alignment films sandwiched between the pair of alignment films, and a pair. Liquid crystal display elements respectively disposed on the pair of electrode layers on the side of the liquid crystal layer of the alignment film (Experimental Example 1-9).

The liquid crystal display element of Experimental Example 1-10 was produced in the same manner as Experimental Example 1-9, except that the polyoxoxane of Synthesis Example 3 was replaced with the polyoxoxane of Synthesis Example 4 in the process. Further, a liquid crystal display element of Comparative Example 1-3 was produced in the same manner as in Experimental Example 9, except that polyoxymethane was not added to the polyamic acid solution DA-1109.

The above liquid crystal display element was placed in an oven at 60 ° C, and the voltage holding ratio (VHR) of 1 V and 5 V was measured as described above, and the results are summarized in Table 3 below.

Comparing the results of Table 3, it was found that the liquid crystal display elements of Experimental Examples 1-9 and Experimental Examples 1-10 exhibited better VHR performance than the liquid crystal display elements of Comparative Examples 1-3 when 5 V DC was applied to the liquid crystal display element. It is apparent that the polysiloxane having both an epoxy group and a liquid crystal group in the alignment film can also enhance the electrical performance of the liquid crystal display element.

Liquid crystal pretilt angle

The liquid crystal display elements of Comparative Example 1-3, Experimental Example 1-9, and Experimental Example 1-10 were taken and the liquid crystal pretilt angle was measured. The results are shown in Table 4 below:

As is clear from the results of Table 4, the pre-tilt angle of the liquid crystal can be appropriately adjusted by adding a polyoxyalkylene having a structure having an epoxy group and a liquid crystal group to the alignment film.

Liquid crystal wettability

The polyaluminoxane of the above Synthesis Example 5 was separately added to the polyaminic acid solution RA 9002-V4 at a relative solid content of 0.1%, and N-methylpyrrolidone/ethylene glycol butyl was used in a weight ratio of 1:1. ether The mixed solvent was diluted to a liquid crystal alignment agent having a solid content of 6.5 wt%, and the liquid crystal alignment agent was coated on a glass substrate with an ITO transparent electrode, prebaked on a hot plate at 85 ° C for 135 seconds, and then displaced at 230 ° C. The oven was baked for 30 minutes to form a film having a thickness of 1000 ± 100 Å (liquid crystal alignment film of Experimental Example 2-1).

The liquid crystal alignment films of Experimental Example 2-2 and Experimental Example 2-3 were produced in the same manner, but the polydecane oxide of Synthesis Example 5 was replaced with the polyoxoxane of Synthesis Example 4 and Synthesis Example 6.

The dynamic contact angle of the liquid crystal on the aforementioned alignment film was measured to evaluate the wettability, and the results are shown in Table 5 below:

Comparing the results of Table 5, it is understood that if the liquid crystal structure of the polyoxyalkylene in the alignment film is substituted by the F atom, the dynamic contact angle of the liquid crystal on the alignment film will decrease. That is, the substitution of the liquid crystal based structure by F can improve the problem of poor liquid crystal wetting of the alignment film.

LCD response time

The polyaluminoxane of the above Synthesis Example 5 was separately added to the polyaminic acid solution RA 9002-V4 at a relative solid content of 0.1%, and N-methylpyrrolidone/ethylene glycol butyl was used in a weight ratio of 1:1. The ether mixture solvent was diluted to a liquid crystal alignment agent having a solid content of 6.5 wt%, and the liquid crystal alignment agent was coated on a glass substrate with an ITO transparent electrode, prebaked on a hot plate at 85 ° C for 135 seconds, and then displaced at 230 ° C. The oven was baked for 30 minutes to form a film (liquid crystal alignment film) having a thickness of 1000 ± 100 Å. Finally, a pair of substrates on which the alignment film is formed are combined with a liquid crystal (purchased from Merck, model LCT11506) by a conventional method to obtain a liquid crystal containing a pair of alignment films sandwiched between the pair of alignment films. A layer and a pair of liquid crystal display elements respectively disposed on the electrode layer on the side of the pair of alignment films away from the liquid crystal layer (Experimental Example 3-1).

The liquid crystal display elements of Comparative Example 3-1 and Experimental Example 3-2 were produced in the same manner, but in Comparative Example 3-1, no polyoxyalkylene was added to the polyamic acid solution RA 9002-V4, but in the experimental example In 3-2, the polyoxyalkylene of Synthesis Example 5 was replaced with the polyoxyalkylene of Synthesis Example 4.

The liquid crystal display element was taken and the liquid crystal response speed (liquid crystal response time) was measured. The results are shown in Table 6 below:

As is clear from the results of Table 6, when the alignment film contains polysiloxane and the polysiloxane has a liquid crystal group structure and an epoxy group structure, the liquid crystal response time can be increased.

In summary, the present invention provides a liquid crystal alignment agent comprising a polyoxyalkylene oxide, and a structure having an epoxy group and a structure having a liquid crystal group are grafted onto the polyoxyalkylene. The use of the liquid crystal alignment agent to form a liquid crystal alignment film in a liquid crystal display element can improve the voltage holding ratio of the liquid crystal display element, improve the wettability of the liquid crystal alignment film, adjust the pretilt angle of the liquid crystal alignment, and even shorten the liquid crystal response. time. Thereby, the display performance of the liquid crystal display element can be improved.

While the invention has been described above in terms of embodiments, it is not intended to limit the invention. Any changes and modifications may be made without departing from the spirit and scope of the invention. Therefore, the scope of protection of this application is subject to the definition of the scope of the patent application attached.

Claims (10)

A liquid crystal alignment agent comprising polyoxyalkylene oxide, which is represented by the following average composition formula: R ¹ _a R ² _b R ³ _c SiZ _(4-abc)/2 , wherein Z is O, -C _n H _2n - or a combination thereof, n is an integer of 1 to 4, R ¹ is a C ₁ - C ₄₀ hydrocarbon group, R ² is a structure having an epoxy group, and R ³ is a structure having a liquid crystal group, 0 < b < 1, 0 < c < 0.5, and 0.5 < (4-abc) / 2 < 1.5. The liquid crystal alignment agent according to claim 1, wherein at least one hydrogen atom of the liquid crystal group-containing structure is substituted with a fluorine atom. The liquid crystal alignment agent according to claim 1, wherein the liquid crystal group structure is a structure represented by the following formula: *-C ₂ H ₄ -Q ¹ -A ¹ -Z ¹ -A ² -Q ² , wherein A ¹ and A ² are respectively a substituted phenyl group, a biphenyl group, a cyclohexylene group, a dicyclohexyl group or a cyclohexyl group; Z ¹ is a single bond, -CH=CH-, -C≡C-, -O-, -COO- or a C ₁ -C ₁₀ alkyl group which may be substituted, wherein the non-adjacent -CH ₂ - may independently be -CH=CH-, -C≡C -, -O- or -COO-substituted; Q ¹ is a single bond, -CH=CH-, -C≡C-, -O-, -COO- or a substituted C ₁ -C ₁₀ alkyl group, wherein Non-adjacent -CH ₂ - may each independently be -CH=CH-, -C≡C-, -O- or -COO-substituted; Q ² is H, F or a substituted C ₁ -C ₁₀ An alkyl group, wherein the non-adjacent -CH ₂ - may each independently be -CH=CH-, -C≡C-, -O- or -COO-substituted; and * is the structure and the liquid crystal group The bonding position of the germanium atom of the polyoxyalkylene. The liquid crystal alignment agent according to claim 1, wherein the liquid crystal group structure is a structure represented by Formula 1: Formula 1, wherein R ⁴ is C ₁ -C ₂₀ alkylene, C ₆ -C ₂₀ phenyl, C ₆ -C ₂₀ cyclohexyl, C ₆ -C ₂₀ fluorophenyl, C ₆ -C ₂₀ a fluorocyclohexyl group or a combination of the above groups, R ⁵ is C ₁ -C ₂₀ alkyl, C ₆ -C ₂₀ phenyl, C ₆ -C ₂₀ cyclohexyl, C ₆ -C ₂₀ fluorophenyl, C ₆ - C ₂₀ fluorocyclohexyl or a combination of the above groups, m and p are each an integer of 0 to 4, and * is a bonding position of the structure represented by Formula 1 to the fluorene atom of the polyoxyalkylene. The liquid crystal alignment agent according to claim 1, wherein the liquid crystal group structure is a structure represented by Formula 2: Formula 2, wherein * represents the bonding position of the structure represented by Formula 2 to the ruthenium atom of the polyoxyalkylene. The liquid crystal alignment agent according to claim 1, wherein the epoxy group-containing structure is a structure represented by Formula 3 or Formula 4: Equation 3, Formula 4 wherein R ⁶ , R ⁷ and R ⁸ are each a C ₁ - C ₁₀ alkyl group, and * is a bonding position of a structure represented by Formula 3 or Formula 4 with a ruthenium atom of the polyoxyalkylene. The liquid crystal alignment agent according to claim 1, wherein c/b<1. The liquid crystal alignment agent according to claim 1, further comprising a polyimine or a polyimide precursor, wherein the ratio of the solid content of the polyoxyalkylene in the liquid crystal alignment agent is 0.05. Weight%~5 wt%. A liquid crystal alignment film obtained by applying the liquid crystal alignment agent according to any one of claims 1 to 8 to a substrate. A liquid crystal display element comprising the liquid crystal alignment film according to claim 9 of the patent application.