TW201536859A - Liquid crystal alignment composition - Google Patents

Abstract

A liquid crystal alignment composition contains at least one polymer and a mixed solvent. The polymer is selected from polyamic acid, polyimide, or a combination of both. The mixed solvent is selected from a combination of 2-butoxyethanol and N-isopropyl-2-pyrrolidone or a combination of 2-butoxyethanol, N-isopropyl-2-pyrrolidone and an auxiliary solvent, wherein the auxiliary solvent can increase the solubility of the polymer in the mixed solvent. In the process of adopting ink-jet printing method to coat the composition to the substrate, the composition can reduce the risk of polymer precipitation, and in the process of coating, the liquid crystal alignment composition can provide a stable droplet coating condition and high collimation, as well as excellent diffusion and leveling properties of the substrate.

Description

Liquid crystal alignment composition

The present invention relates to a liquid crystal alignment composition, and more particularly to a liquid crystal alignment composition suitable for an ink jet printing coating method.

The liquid crystal display mainly uses an applied electric field to change the alignment state of the liquid crystal molecules, thereby causing the polarization state and direction of the light to change, thereby obtaining a display effect of light and dark contrast.

As the size of the screen has expanded, liquid crystal displays have been developed to incorporate liquid crystal display elements of Thin-Film Transistors (TFTs) in each pixel. 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, it is necessary to control the arrangement of liquid crystal molecules 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. The change in the alignment state of the liquid crystal molecules must be achieved by allowing the liquid crystal molecules to have a uniform pretilt angle and a fixed direction alignment on the substrate. At present, a common method is to apply an alignment film on the substrate, and the alignment film controls the alignment direction of the liquid crystal molecules and provides a stable pretilt angle of the liquid crystal molecules. When the applied electric field is turned off, the liquid crystal molecules are opposed to the anchoring force and the elastic coefficient of the interface with the alignment film. Restore to the original arrangement.

At present, the method for preparing an alignment film in the industry is to apply a liquid crystal alignment composition on a surface of a substrate, and the molecules on the surface of the film are oriented by friction or other means, thereby providing liquid crystal molecules which are subsequently inserted to be tilted in a fixed direction. The alignment composition may comprise polyvinyl alcohol, polyethylene glycol, polyamidamine, polyaminic acid or polyimine, wherein polyamic acid and polyimine have excellent thermal stability and good Mechanical, electrical and chemical resistance are most commonly utilized as alignment film materials. Polylysine is a polymer obtained by polymerization of a diamine with a tetracarboxylic acid or a tetracarboxylic dianhydride, and polyimine is generally subjected to a high temperature dehydration ring-closing reaction by polylysine [ie, quinone Made by Imidization.

In the past, the alignment film coating method was mainly roll printing, and the alignment film material was transferred to the substrate by an APR plate (ASAHI KASEI photosensitive resin plate) to obtain an alignment film having a uniform film thickness. However, in addition to cleaning and replacement of APR panels, expensive Doctor Rolls and Anilox Rolls need to be replaced regularly, especially when large panels are encountered. Therefore, in order to meet the demand for a large-sized panel, the coating of the alignment film is gradually transferred from the coating method of the APR sheet transfer to the inkjet coating method.

However, existing inkjet printing technology has many advantages over rotary printing, but there are still many techniques to be overcome, such as liquid crystal alignment composition for coating on a substrate and forming a liquid crystal alignment film in inkjet printing. In addition to reducing the risk of precipitation of the alignment film material of poly-proline or polyimine, it is also necessary to have a stable droplet coating condition and high collimation, and the alignment composition It should also have excellent diffusion on the substrate. Sexuality and leveling to avoid uneven diffusion or uneven film thickness of the formed alignment film.

Accordingly, it is an object of the present invention to provide a method suitable for ink jet printing which, in addition to reducing the risk of precipitation of an alignment film material of polylysine or polyimine, is stable in the coating process. The liquid droplet alignment condition and high collimation, and the formed alignment film also has a liquid crystal alignment composition excellent in diffusibility and leveling property.

Thus, the liquid crystal alignment composition of the present invention comprises at least one polymer and a mixed solvent.

The polymer is selected from the group consisting of polylysine, polyimine or a combination of the two.

The mixed solvent is selected from the group consisting of a combination of ethylene glycol butyl ether and nitrogen-isopropyl-2-pyrrolidone, or a combination of ethylene glycol butyl ether, nitrogen-isopropyl-2-pyrrolidone, and an auxiliary solvent, wherein The auxiliary solvent can increase the solubility of the mixed solvent to the polymer.

The effect of the present invention is to utilize the mixed solvent containing ethylene glycol butyl ether and nitrogen-isopropyl-2-pyrrolidone to allow the liquid crystal alignment composition to be applied to the substrate by inkjet printing. The polymer has a risk of precipitation, and the liquid crystal alignment composition has stable droplet discharge condition and high collimation during coating, and also has excellent diffusibility and leveling property on the substrate, and can be avoided. The formed alignment film is caused by uneven diffusion or uneven film thickness.

The contents of the present invention will be described in detail below:

[polymer]

The polymer of the liquid crystal alignment composition of the present invention is selected from the group consisting of polylysine, polyimine or a combination of the two. The polyamic acid is preferably obtained by reacting a tetracarboxylic dianhydride with a diamine. The polyimine is preferably prepared by a ruthenium imidization reaction of polylysine.

The tetracarboxylic dianhydride may be any tetracarboxylic dianhydride compound suitable for the preparation of polyamic acid. Preferably, the tetracarboxylic dianhydride is selected from 1,2,3,4-cyclobutane IV. Formic acid dianhydride, pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthyl Diacid dianhydride, 1,2,3,4-butane tetracarboxylic dianhydride, ethylene-ethylene glycol-bis(hydroper trimellitate) (TMEG-100), 2,3,5-tricarboxyl ring Pentylacetic acid dianhydride (TCA).

The diamine may be any diamine-containing compound suitable for the preparation of polyamic acid. Preferably, the diamine is selected from 5(6)-amino-1,3,3-trimethyl-1-( 4-aminophenyl)indane (TMDA), methyl 4'-propyl-bis(cyclohexane)-4-yl-3,5-diamino-2-methylbenzoate.

Preferably, the polymer content is 2 to 5 parts by weight based on 100 parts by weight of the total weight of the liquid crystal alignment composition.

[mixed solvent]

The mixed solvent is selected from the group consisting of: (1) a combination of ethylene glycol butyl ether and nitrogen-isopropyl-2-pyrrolidone, and (2) ethylene glycol butyl ether, nitrogen-isopropyl-2-pyrrolidone, and A combination of auxiliary solvents. The following two aspects will be further explained separately:

(1) The mixed solvent is a combination of ethylene glycol butyl ether and nitrogen-isopropyl-2-pyrrolidone:

Preferably, the content of the ethylene glycol butyl ether is in the range of 20 to 70% by weight based on the total weight of the mixed solvent, and the content of the nitrogen-isopropyl-2-pyrrolidone is in the range of 30 to 80% by weight. More preferably, the content of ethylene glycol butyl ether ranges from 30 to 60% by weight, and the content of nitrogen-isopropyl-2-pyrrolidone ranges from 40 to 70% by weight. Since the ethylene glycol butyl ether can increase the leveling property of the composition on the substrate, if the mixed solvent is a combination of ethylene glycol butyl ether and nitrogen-isopropyl-2-pyrrolidone, if the ethylene When the content of the butyl ether is less than 20% by weight, the leveling property of the liquid crystal alignment composition on the substrate is deteriorated; if the content is more than 70% by weight, the nitrogen-isopropyl-2 for dissolving the polymer is caused. - The pyrrolidone content is lowered, posing a risk of precipitation of the polymer.

(2) Combination of ethylene glycol butyl ether, nitrogen-isopropyl-2-pyrrolidone and an auxiliary solvent:

The auxiliary solvent may be any solvent capable of increasing the solubility of the mixed solvent to the polymer. Preferably, the auxiliary solvent is selected from the group consisting of nitrogen-methyl-2-pyrrolidone, γ-butyrolactone, nitrogen, and nitrogen-two. Methylacetamide, dimethyl hydrazine or a combination of the foregoing. More preferably, the auxiliary solvent is nitrogen-methyl-2-pyrrolidone.

Preferably, the content of the ethylene glycol butyl ether ranges from 20 to 70% by weight based on the total weight of the mixed solvent, and the total content of the nitrogen-isopropyl-2-pyrrolidone and the auxiliary solvent ranges from 30 to 80 wt%. %, and the content ratio of the auxiliary solvent to nitrogen-isopropyl-2-pyrrolidone ranges from more than 0 to less than 4. When the content ratio of the auxiliary solvent to the nitrogen-isopropyl-2-pyrrolidone is not less than 4, the diffusibility of the liquid crystal alignment composition on the substrate and the leveling property are lowered.

[Liquid alignment compound]

The liquid crystal alignment composition is obtained by dissolving the polymer in the mixed solvent.

The liquid crystal alignment composition is applied to the surface of the substrate by inkjet printing using a printer to form a liquid crystal alignment film.

Other features and effects of the present invention will be apparent from the following description of the drawings, wherein: FIG. 1 is a photograph of the embodiment 1 after inkjet printing onto a substrate (the ink jet spacing is 230 μm, the applied voltage was 22 V); and FIG. 2 is a photograph (the ink jet pitch was 230 μm and the applied voltage was 22 V) after the inkjet printing method of Comparative Example 1 was applied to the substrate.

The present invention will be further illustrated by the following examples, but it should be understood that this embodiment is intended to be illustrative only and not to be construed as limiting.

<Examples 1 to 4, Comparative Examples 1 to 2>

Preparation of liquid crystal alignment composition

Nitrogen-methyl-2-pyrrolidone (NMP), nitrogen-isopropyl-2-pyrrolidone (NIP) and ethylene glycol butyl ether (BC) were mixed according to the ratios shown in Tables 1 and 2, respectively, to prepare a mixed solvent.

The polyamic acid solution RA9002 (sold by Daxing material) was drained to remove the original solvent, and then added to the above mixed solvent, and diluted to a polyglycine content concentration of 3.5% by weight to obtain Examples 1 to 4 and Comparative example 1~2 The liquid crystal alignment composition.

<Coating test of liquid crystal alignment composition on substrate>

The liquid crystal alignment compositions of Examples 1 to 4 and Comparative Examples 1 and 2 were inkjet-printed using a Fujifilm Dimatix nanotechnology printer [drop spacing setting of 230 μm and application voltage of 22 V]. The method is applied to the surface of the substrate and dried to form a liquid crystal alignment film. The difference in height between the droplet diffusion diameter and the film surface and the center of the formed alignment film after the composition was observed was as shown in Tables 1 and 2. Further, in comparison with Example 1 and Comparative Example 1, respectively, the inkjet pitch was 230 μm and the applied voltage was 22 V, and the film was applied to the surface of the substrate using the above-mentioned Fujifilm Dimatix nanotechnology printer, and photographed by an optical microscope. 1 (Example 1) and the photograph of Figure 2 (Comparative Example 1).

As can be seen from Table 1, Figure 1 and Figure 2, the mixed solvent used in Example 1 in combination with nitrogen-isopropyl-2-pyrrolidone (NIP) and ethylene glycol butyl ether (BC), and with nitrogen-methyl-2- In Comparative Example 1 in which pyrrolidone (NMP) was substituted with nitrogen-isopropyl-2-pyrrolidone (NIP), the droplet diffusion diameter of the composition of Comparative Example 1 after application was shortened (that is, the diffusibility of the composition was deteriorated). It is confirmed that the liquid crystal alignment composition of the present invention needs to contain both nitrogen-isopropyl-2-pyrrolidone (NIP) and ethylene glycol butyl ether (BC), and the composition is coated by inkjet printing. Excellent diffusibility in the process to the substrate.

It can be seen from Table 2 that when the mixed solvent contains ethylene glycol butyl ether (BC), nitrogen-isopropyl-2-pyrrolidone (NIP), and nitrogen-methyl-2-pyrrolidone (NMP, auxiliary solvent), the comparative example The droplets of the composition after coating The dispersion diameter becomes shorter (that is, the diffusibility of the composition is deteriorated), and the difference in the height of the liquid crystal alignment film formed from the surface of the liquid crystal alignment film becomes large (that is, the flatness of the composition flow becomes poor), and the liquid crystal alignment composition of the present invention is confirmed. When the mixed solvent is a combination of ethylene glycol butyl ether (BC), nitrogen-isopropyl-2-pyrrolidone (NIP), and an auxiliary solvent [nitrogen-methyl-2-pyrrolidone (NMP)], the mixed solvent The total weight is 100% by weight, the content of ethylene glycol butyl ether is required to be 20 to 70% by weight, and the total content of nitrogen-isopropyl-2-pyrrolidone and auxiliary solvent is required to be 30 to 80% by weight, auxiliary solvent and nitrogen- The content ratio of isopropyl-2-pyrrolidone needs to be less than 4, and the liquid crystal alignment composition has stable droplet coating condition and high collimation in the process of being applied to the substrate by inkjet printing. It also has excellent diffusibility and leveling properties on the substrate.

In summary, the liquid crystal alignment composition can be applied to the substrate by inkjet printing by using the mixed solvent containing ethylene glycol butyl ether and nitrogen-isopropyl-2-pyrrolidone. Stable droplet coating condition and high collimation, and excellent diffusibility and leveling property on the substrate, thus avoiding uneven diffusion or uneven thickness of the alignment film formed on the substrate, so It is indeed possible to achieve the object of the invention.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and patent specification content of the present invention, All remain within the scope of the invention patent.

Claims (7)

A liquid crystal alignment composition comprising: at least one polymer selected from the group consisting of polylysine, polyamidiamine or a combination of the two; and a mixed solvent selected from the group consisting of ethylene glycol butyl ether a combination with nitrogen-isopropyl-2-pyrrolidone, or a combination of ethylene glycol butyl ether, nitrogen-isopropyl-2-pyrrolidone, and an auxiliary solvent, wherein the auxiliary solvent can increase the mixed solvent to the polymer Solubility. The liquid crystal alignment composition according to claim 1, wherein the auxiliary solvent is selected from the group consisting of nitrogen-methyl-2-pyrrolidone, γ-butyrolactone, nitrogen, nitrogen-dimethylacetonitrile, and dimethyl hydrazine. Or a combination of the foregoing. The liquid crystal alignment composition according to claim 1, wherein the mixed solvent is a combination of ethylene glycol butyl ether and nitrogen-isopropyl-2-pyrrolidone. The liquid crystal alignment composition according to claim 3, wherein the content of the ethylene glycol butyl ether is in the range of 20 to 70% by weight based on the total weight of the mixed solvent, and the nitrogen-isopropyl-2-pyrrolidone The content ranges from 30 to 80% by weight. The liquid crystal alignment composition according to claim 1, wherein the mixed solvent is a combination of ethylene glycol butyl ether, nitrogen-isopropyl-2-pyrrolidone, and an auxiliary solvent. The liquid crystal alignment composition according to claim 5, wherein the content of the ethylene glycol butyl ether is 20 to 70% by weight based on the total weight of the mixed solvent, and the nitrogen-isopropyl-2-pyrrolidone and The total content of the auxiliary solvent ranges from 30 to 80% by weight, and the auxiliary solvent and nitrogen-isopropyl-2-pyridyl The content ratio of the cyanones is in the range of more than 0 to less than 4. The liquid crystal alignment composition according to claim 1, wherein the polymer content is 2 to 5 parts by weight based on 100 parts by weight of the total composition.