KR101123156B1 - Method for preparation of photoalignment layer formed pretilt angle using peel-off process - Google Patents

Abstract

The present invention relates to a method for producing a photoalignment film having a pretilt angle formed using a peel-off process. More specifically, a photoreactive oligomer is applied to a substrate in which a solution dissolved in a solvent is removed on a substrate. Manufacturing a photo-alignment film in which photoreactive oligomers are arranged in one direction; Preparation of a photoalignment film having a pretilt angle formed by using a peel-off process comprising attaching a polymer film to the optical alignment film and then separating the optical alignment film and the polymer film using a peel-off process. The method and the manufacturing method of the optical alignment film liquid crystal cell using the optical alignment film in which the pretilt angle was formed by the said method, and the optical alignment film in which the pretilt angle was formed by the said method.

Pretilt angle, photoalignment film, peel-off, linearly polarized ultraviolet light, hydrophilic, photoreactive oligomer, polymer film, ozone

Description

Method for preparation of photoalignment layer formed pretilt angle using peel-off process}

The present invention relates to a method for producing a photoalignment film having a pretilt angle formed using a peel-off process. More specifically, a photoreactive oligomer is applied to a substrate in which a solution dissolved in a solvent is removed on a substrate. Manufacturing a photo-alignment film in which photoreactive oligomers are arranged in one direction; Preparation of a photoalignment film having a pretilt angle formed by using a peel-off process comprising attaching a polymer film to the optical alignment film and then separating the optical alignment film and the polymer film using a peel-off process. The method and the manufacturing method of the optical alignment film liquid crystal cell using the optical alignment film in which the pretilt angle was formed by the said method, and the optical alignment film in which the pretilt angle was formed by the said method.

In today's information society, large-sized and flattened displays and various displays are essential for the video industry. Among such displays, liquid crystal displays (LCDs), which display information by controlling the opening and closing of light by the alignment of liquid crystals, have an advantage of being applicable to large areas at low manufacturing costs. Therefore, the liquid crystal display device occupies most of the world flat panel display market, and has attracted much attention as a representative flat panel display device.

The principle of the liquid crystal display device is a liquid crystal alignment layer for arranging liquid crystals having an anisotropic structure in a specific direction, a backlight for providing light, a polarizer for controlling the opening and closing of light, and the implementation of color. It consists of a color filter, an electrode for generating an electric field, and a liquid crystal layer.

In the liquid crystal alignment technology, an alignment direction is determined according to whether an electric field is applied to a liquid crystal layer arranged in a specific direction on the alignment layer, and information is displayed by adjusting the transmittance of light passing through the liquid crystal layer. The liquid crystal alignment characteristic of the liquid crystal alignment film is a key point that influences display quality such as brightness and contrast ratio in the device.

The liquid crystal aligning film in the commercially available liquid crystal display device mainly uses a polymer material. The most common method is to apply a polymer, such as polyimide, to a glass substrate, and then use a rubbing method that rubs in a fixed direction using a roller wrapped in a fiber cloth. Form a groove. The liquid crystal is physically oriented parallel to the direction of the grooves formed in the alignment layer and has a relatively easy and simple process advantage. However, the rubbing method has problems such as static electricity generated when the alignment film is in contact with the roller, dust generated by a cloth wrapped in the roller, and defects caused by not forming a groove uniformly in the entire polymer area.

Therefore, in recent years, photoalignment, imprint, oblique evaporation, and the like have been proposed as liquid crystal alignment methods to replace the rubbing method. In particular, the photo-orientation method is based on the anisotropic structure formation of photoreactive materials by linearly polarized UV light, and the photoreactive materials include azobenzene, cinnamate, coumarin (coumarine), polyimide (polyimide) and the like. This orientation method has the advantage of allowing a low process temperature and having a multi-domain structure with different orientation directions within one glass substrate, but the formation of a pretilt angle and the arrangement of liquid crystals in a particular direction. In terms of limitations.

The present invention for solving the above problems is to prepare an alignment film with a photoreactive oligomer, attaching the polymer film to the alignment film, and then preparing a photoalignment film having a pretilt angle by separating the polymer film from the alignment film by a peel-off process. It is an object to provide a method.

Another object of the present invention is to provide a photoalignment film formed with a pretilt angle.

Still another object of the present invention is to provide a method of manufacturing a photoalignment film liquid crystal cell using the photoalignment film on which the pretilt angle is formed.

The present invention comprises the steps of applying a solution in which the photoreactive oligomer is dissolved in a solvent on a substrate and then removing the solvent to prepare a photoalignment film in which the photoreactive oligomer is arranged in one direction by irradiation of linearly polarized ultraviolet light; Preparation of a photoalignment film having a pretilt angle formed by using a peel-off process comprising attaching a polymer film to the optical alignment film and then separating the optical alignment film and the polymer film using a peel-off process. It may provide a method.

The present invention can provide a photoalignment film having a pretilt angle formed by the above method.

The present invention can provide a method for manufacturing a photoalignment liquid crystal cell comprising the step of preparing two optical alignment film having a pretilt angle formed by the above method and injecting a liquid crystal between the two optical alignment film.

The present invention is a peel-off process comprising the step of separating the photoalignment film and the polymer film using a peel-off process after attaching the polymer film to the photoalignment film arranged in one direction the photoreactive oligomer It is possible to provide a method for producing a photo-alignment film having a pretilt angle formed by using.

According to the present invention, an alignment layer is formed by controlling the adhesive force between an oligomeric material on the surface of the photoalignment layer and a polymer film whose hydrophilicity is controlled by using a hydrophilicity controlled surface of the polymer film and introducing a peel-off process to prepare a photoalignment layer. By aligning the molecules on the surface in a specific direction, the formation of the pretilt angle in the photo-alignment film can be induced.

The present invention shows a method for producing a photoalignment film having a pretilt angle.

The present invention comprises the steps of applying a solution in which the photoreactive oligomer is dissolved in a solvent on a substrate and then removing the solvent to prepare a photoalignment film in which the photoreactive oligomer is arranged in one direction by irradiation of linearly polarized ultraviolet light; Preparation of a photoalignment film having a pretilt angle formed by using a peel-off process comprising attaching a polymer film to the optical alignment film and then separating the optical alignment film and the polymer film using a peel-off process. Indicates the method.

In the photoreactive oligomer may be used cinnamate (cinnamate) series.

As the photoreactive oligomer, 1,4-Butanediyl dicinnamoyl ether oligomer (2Ci-BD), which is a cinnamate series, may be used.

In the photoreactive oligomer may be used coumarine (coumarine) series.

As the photoreactive oligomer, azobenzene series may be used.

In the above, the photoreactive oligomer may use a chalcone series.

The solvent used to dissolve the photoreactive oligomer to obtain a solution may be used cyclohexanone (cyclohexanone).

Tetrahydrofuran (THF) may be used as the solvent used to dissolve the photoreactive oligomer to obtain a solution.

As the solvent used to dissolve the photoreactive oligomer to obtain a solution, pyridine may be used.

The solvent may be a mixed solvent in which cyclohexanone, tetrahydrofuran (THF), and pyridine are mixed.

The solvent may be a mixed solvent in which cyclohexanone, tetrahydrofuran (THF), and pyridine are mixed in the same weight ratio.

As the solution in which the photoreactive oligomer is dissolved, a solution containing 1 to 50% by weight of the photoreactive oligomer can be used.

As the solution in which the photoreactive oligomer is dissolved, a solution containing 1 to 40% by weight of the photoreactive oligomer can be used.

As the solution in which the photoreactive oligomer is dissolved, a solution containing 1 to 30% by weight of the photoreactive oligomer can be used.

As the solution in which the photoreactive oligomer is dissolved, a solution containing 1 to 20% by weight of the photoreactive oligomer can be used.

As the solution in which the photoreactive oligomer is dissolved, a solution containing 1 to 10% by weight of the photoreactive oligomer can be used.

As the solution in which the photoreactive oligomer is dissolved, a solution containing 1 to 5% by weight of the photoreactive oligomer can be used.

The substrate may be a glass substrate.

The substrate may be a plastic substrate.

The plastic substrate may be a polyether sulfone substrate.

The plastic substrate may be a polycarbonate substrate.

The plastic substrate may be a polyethylene naphthalate substrate.

The solvent may be removed by cold air, hot air, or free baking.

In the above, the solvent may be removed by a process for 1 to 2 hours in a cold air of -20 ℃ to -5 ℃.

In the above, the solvent may be removed by a process of treatment for 1 hour with cold air of -15 ℃.

In the above, the solvent may be removed by a process for 1 to 2 hours with hot air at 40 to 50 ℃.

In the above, the solvent may be removed by a process for 1 hour with hot air at 45 ℃.

In the above, the solvent can be removed by prebaking for 1 to 2 hours at 60 ~ 70 ℃.

In the above, the solvent may be removed by prebaking at 65 ° C. for 1 hour.

Irradiation of linearly polarized ultraviolet light in the above can be carried out for 30 minutes to 1 hour.

In the above, the linearly polarized ultraviolet light can be irradiated having a wavelength range of 250 ~ 400nm.

That is, in the present invention, the photoreactive oligomer reacts to linearly polarized ultraviolet light having a wavelength range of about 280 nm for cinnamate-based material, about 300 nm for coumarin-based material, about 350 to 400 nm for azobenzene-based material, and about 310 nm for chalcone-based material. Therefore, in the present invention, the linear flat ultraviolet light may use a linear flat ultraviolet light having a wavelength range of 250 to 400 nm.

The linearly polarized ultraviolet light may be irradiated at an angle of 0 ° with respect to the normal direction of the substrate coated with the photoreactive oligomer.

As the polymer film, a hydrophilic polymer film may be used.

In the polymer film, hydrophilic polydimethylsiloxane (polydimethylsiloxane, PDMS) may be used.

The polymer film may be used as a hydrophilic polyvinyl alcohol (polyvinyl alcohol).

In the polymer film, the treatment time (UVO time / min) of UV and ozone to polydimethylsiloxane is within 5 minutes, preferably 0.5 minutes to 5 minutes, or plasma treatment to control hydrophilicity. Can be used.

In the polymer film, UV and ozone treatment time (UVO time / min) of polyvinyl alcohol may be used within 5 minutes, preferably 0.5 minutes to 5 minutes, or plasma treatment to control hydrophilicity. have.

In order to control the hydrophilicity of the polymer film, the treatment time of UV and ozone on the polymer film is set to 5 minutes or less, so that the adhesion work between the polymer film and the photo-alignment film causes the molecules to stand in a specific direction without loss of material on the surface of the alignment film. Because it is suitable. In the case where the polymer film is treated with ultraviolet rays and ozone for more than 5 minutes, the adhesion of the photo-alignment film may increase due to the high hydrophilicity of the polymer film, resulting in the loss of the alignment film material.

In the peel-off process, the optical alignment layer and the polymer film may be separated by performing a uniform peel-off process using a roller rotating at a constant speed.

In the peel-off process, the optical alignment layer and the polymer film may be separated by performing a uniform peel-off process using a roller rotating at 0.1 to 1 rpm.

By the peel-off process, photoreactive oligomer molecules may be erected on the surface of the photoalignment layer to form a pretilt angle.

The present invention includes a photoalignment film having a pretilt angle formed by the above-mentioned method.

The present invention includes a method of manufacturing a photoalignment film liquid crystal cell using a photoalignment film having a pretilt angle formed by the above-mentioned method.

The present invention includes a method of manufacturing a photoalignment film liquid crystal cell comprising preparing two optical alignment films having a pretilt angle formed by the above-mentioned method and injecting a liquid crystal between the two optical alignment films. .

According to the present invention, a liquid crystal cell is prepared by preparing two optical alignment films having a pretilt angle formed by the above-mentioned method and using polystyrene beads as a spacer between the two optical alignment films. And then injecting a nematic liquid crystal to prepare a liquid crystal cell of an optical alignment layer, characterized in that the liquid crystal is arranged in a specific direction.

The liquid crystal injection method using a capillary force may be used between two photoalignment layers in which molecules are induced on the alignment layer surface when the photoalignment layer liquid crystal cell is manufactured.

Hereinafter, the content of the present invention will be described in detail through examples. However, these are intended to explain the present invention in more detail, and the scope of the present invention is not limited thereto.

≪ Example 1 >

(1) Preparation of photoreactive oligomer alignment film

A photoreactive cinnamate oligomer solution was prepared by dissolving 2% by weight of 1,4-Butanediyl dicinnamoyl ether oligomer (2Ci-BD) (see FIG. 1), which is a photoreactive cinnamate series, in 98% by weight of cyclohexanone.

The photoreactive cinnamate oligomer solution was applied on a glass substrate by spin-coating, followed by prebaking at 60 ° C. for 1 hour to remove the solvent by evaporation to prepare a photoreactive alignment layer substrate. .

The photoreactive alignment layer substrate was irradiated with linearly polarized ultraviolet light for 30 minutes to align cinnamate dimers in a direction perpendicular to the linearly polarized ultraviolet light through [2 + 2] dimerization reaction between cinnamate molecules.

(2) Peel-off process of polymer film on photo-alignment film

As shown in FIG. 2, a flexible polymer film was attached onto the cinnamate dimer alignment layer arranged in one direction by irradiation of linearly polarized ultraviolet light. Thereafter, the polymer film was peeled off at a constant speed of 1 rpm in a direction parallel to the direction in which the cinnamate dimers were arranged to induce the erecting of molecules in a specific direction on the surface of the alignment film, thereby preparing an optical alignment film having a pretilt angle.

At this time, the flexible polymer film used in the peel-off process was used polydimethylsiloxane (polydimethylsiloxane, PDMS). In the polydimethylsiloxane film, the hydrophilicity on the surface of the polymer film was controlled by adjusting the treatment time when UV and ozone were treated on the film. The contact angle immediately after dropping water droplets on the surface of the polymer film by adjusting the treatment time of ultraviolet rays and ozone was measured. Measured values and images are shown in FIG. 3. As shown in FIG. 3, the contact angle of the polymer film decreased as the treatment time of UV and ozone was increased, which means that the hydrophilicity of the polymer film was increased as a result of UV and ozone treatment.

The peel-off process of the hydrophilic controlled polymer film on the cinnamate dimer surface arranged in one direction used a roller moving at a specific speed of 1 rpm to maintain uniformity. The polymer film was sufficiently flexible and durable to cover the surface of the roller, thus enabling a uniform peel-off process.

Example 2 Preparation of Optical Alignment Film Liquid Crystal Cell and Measurement of Pretilt Angle

Two photo-alignment films prepared in Example 1 were prepared, and a liquid crystal cell was prepared using two photo-alignment film substrates using polystyrene beads as a spacer. Then, a nematic liquid crystal was injected at 65 ° C., and then cooled at a temperature of 1 ° C./min at room temperature to arrange liquid crystals in a specific direction on the alignment layer.

The pretilt angle of the prepared liquid crystal cell was measured by a crystal rotation method and the results are shown in FIG. 4. This is the result of pretilt angle according to the change of UV and ozone treatment time in the polymer film used in the peel-off process for the photoreactive cinnamate oligomer and cinnamate polymer, respectively. In the graph of FIG. 4, 2Ci-BD (-●-) means 2Ci-BD which is a photoreactive cinnamate oligomer, and PVCi (-○-) means poly (vinyl cinnamate) which is a photoreactive cinnamate polymer.

In the case of cinnamate polymers, the pretilt angles close to 0 ° were almost similar regardless of the hydrophilic properties of the polymer film surface used during peel-off. On the other hand, in the case of cinnamate polymer, the pretilt angle increased as the treatment time was increased when the UV and ozone treatment time was 5 minutes or less. However, in the subsequent ultraviolet and ozone treatment times, the pretilt angle decreased with increasing treatment time. That is, the maximum pretilt angle at peel-off of the polymer film treated with UV and ozone for 5 minutes was shown on the surface of the photo-alignment layer.

Example 3 Calculation of Bonding Date for Analysis of Pretilt Results

For the analysis of the pretilt results shown in Example 2, the ratio of work of adhesion was determined on the following three surfaces, namely, the glass substrate surface, the cinnamate oligomer alignment layer surface, and the ultraviolet and ozone treated polymer film surfaces. At this time, since the ratio of the adhesion work is a function of the surface tension, it can be obtained from the contact angle of the dispersion component and the polar component. The ratio of the adhesion days shown in FIG. 5 is represented by R, and R is the ratio of the adhesion day between the glass substrate and the alignment film and the adhesion day between the alignment film and the polymer film.

In the polymer film, the ratio of the adhesion days according to the change of UV and ozone treatment time is less than 1 in the treatment time of 5 minutes or less and greater than 1 in the subsequent treatment time.

When the adhesion work ratio is greater than 1, since the adhesion work between the alignment film and the polymer film is greater than the adhesion work between the glass substrate and the alignment film, it means that the alignment film material may fall off and be lost by the polymer film. Therefore, the pretilt angle is reduced when peeling off the UV and ozone treated polymer film after 5 minutes.

On the other hand, when the ratio of the adhesion work is less than 1, since the adhesion work between the glass substrate and the alignment film is larger than the adhesion work between the alignment film and the polymer film, the adhesion force between the alignment film and the polymer film without loss of the alignment film material is used. The build up of molecules in the peel-off direction is induced. In particular, when peeling off the polymer film treated for 5 minutes, which exhibits the largest R value when the ratio of adhesion days is less than 1, molecules are effectively erected on the surface of the alignment film, thereby exhibiting the maximum pretilt angle.

Example 4 Orientation Characteristics of Photoalignment Film Introduced by Peel-Off Process

6 shows the results of observing the alignment characteristic of the optical alignment film having the pretilt angle formed in Example 1 with a polarized optical microscope. The optical alignment film having the pretilt angle formed in Example 1 has a black direction (see FIG. 6 (a)) between two vertical polarizers and a white direction (see FIG. 6 (b)) between parallel polarizers. It confirmed that the liquid crystal was orientated uniformly.

As described above, although described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and modified within the scope of the present invention without departing from the spirit and scope of the invention described in the claims below. It will be appreciated that it can be changed.

Figure 1 shows the chemical structure of the photoreactive cinnamate oligomer of Example 1 and the ¹ H NMR spectrum results of the oligomer.

Figure 2 shows a schematic diagram of a photo-alignment film forming process introduced the peel-off process of the flexible polymer film of Example 1.

Figure 3 shows the results of measuring the contact angle of the surface of the flexible polymer film treated with ultraviolet and ozone of Example 2.

Figure 4 shows the pretilt angle according to the ultraviolet and ozone treatment time of the polymer film in the photoalignment film introduced the peel-off process of the polymer film of Example 3.

Figure 5 shows the ratio of the adhesion days between the three surfaces according to the ultraviolet and ozone treatment time of the polymer film used in the peel-off process of Example 4.

FIG. 6 shows a polarization micrograph of a liquid crystal cell in which a peel-off process of Example 5 is introduced.

Claims (16)

Cinamate-based photoreactive oligomer is applied to a substrate in which a solution dissolved in a solvent is removed on the substrate, the solvent is removed and photoreactive oligomer by irradiation of linearly polarized ultraviolet light at an angle of 0 ° to the normal direction of the substrate to which the photoreactive oligomer is applied Manufacturing an optical alignment film arranged in one direction; Peel-off after attaching the polymer film of hydrophilicity controlled by UV and ozone treatment for 0.5 to 5 minutes or plasma treatment to the polymer film of polydimethylsiloxane or polyvinyl alcohol on the optical alignment film A method of manufacturing an optical alignment film having a pretilt angle formed by using a peel-off process comprising the step of separating the optical alignment film and the polymer film using a peel-off process. delete The method of claim 1, wherein the solvent is cyclohexanone, tetrahydrofuran (THF), or pyridine. The method of claim 1, wherein the substrate is a glass, polyether sulfone (polyether sulfone) substrate, polycarbonate (polycarbonate) substrate or polyethylene naphthalate (polyethylene naphthalate) substrate characterized in that the pretilt angle using a peel-off process Method for producing a photo-alignment film formed. Claim 5 was abandoned upon payment of a set-up fee. The method of claim 1, wherein the solvent is removed by prebaking at 60 to 70 ° C. for 1 to 2 hours. Claim 6 was abandoned when the registration fee was paid. The method of claim 1, wherein the linearly polarized ultraviolet light is irradiated for 30 minutes to 1 hour. delete delete delete delete The method of claim 1, wherein the peel-off process is performed by using a roller that rotates at a constant speed to perform a uniform peel-off process. Claim 12 was abandoned upon payment of a registration fee. The method of claim 1, wherein the peel-off process is performed by separating the optical alignment film and the polymer film by using a roller rotating at 0.1 to 1 rpm. The method of claim 1, wherein the pretilt angle is formed by forming the photoreactive oligomer molecules on the surface of the photoalignment layer by the peel-off process. Claims 1, 3, 4, 5, 6, 11, 12, and 13 wherein the pre-tilt formed by the method of any one of the selected method. Claims 1, 3, 4, 5, 6, 11, 12 and 13, wherein the optical alignment film having a pretilt angle formed by the method of any one selected from claim Preparing a dog and injecting a liquid crystal between the two photo-alignment layer manufacturing method of a photo-alignment layer liquid crystal cell. The liquid crystal cell of claim 15, wherein a polystyrene bead is used as a spacer between the two optical alignment layers to manufacture a liquid crystal cell, and then nematic liquid crystal is injected to arrange the liquid crystal in a specific direction. Method for producing a photo-alignment film liquid crystal cell, characterized in that.

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