JP4565151B2 - Liquid crystal alignment film, liquid crystal display device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a liquid crystal alignment film, a liquid crystal display device, and a manufacturing method thereof.

  Liquid crystal display elements are used in many display devices such as fixed displays and displays. In order to produce a liquid crystal display element, a liquid crystal alignment layer is necessary, and for fixed display, it is necessary to form a pattern on the alignment film. In the display application, a liquid crystal alignment film pattern forming technique is used to improve the viewing angle dependency and the contrast.

  In the case of a rubbed polyimide film often used as an alignment film, a method of forming an alignment pattern by ultraviolet light irradiation or laser drawing as a mask, a method of rubbing a part through a desired mask, a mask, a photoresist, etc. There are many methods such as patterning using rubbing multiple times, rubbing multiple times on the substrate and rubbing only on the convex part, rubbing on the polyimide that has been patterned from the beginning using printing and photocuring methods. It is used. In addition, a method using a special polymer that can be oriented by irradiation with polarized light is used, but all of them require complicated steps. Moreover, since it is necessary to use a solvent for the formation of the polyimide film, the environment is burdened.

The present inventors have invented a method for easily obtaining an alignment film by using a friction transfer method for a sigma-conjugated polymer and a pi-conjugated polymer that can easily form a pattern by light irradiation (Patent Document 1). ). Using this, it was applied to a polarizing filter (Patent Document 2), a polarized light emitting element (Patent Document 2, Patent Document 3, Patent Document 4), a polarization detector (Patent Document 5), and a field effect transistor (Patent Document 6). . Unlike the rubbing method, this method can reduce the number of steps because film formation and orientation can be performed simultaneously. Moreover, since a solvent is not used for film formation, an environmental load is not imposed.
Japanese Patent No. 2565780 Japanese Patent No. 2976026 Japanese Patent No. 3138734 Japanese Patent No. 3177640 JP2003-098343 JP2003-347568

  The present invention has been made in view of the above-described current state of the prior art, and its main purpose is to provide a method capable of producing a liquid crystal alignment film in which an alignment pattern is easily formed.

  The present inventor has intensively studied to achieve the above-described object. As a result, a liquid crystal alignment film can be obtained by forming a conjugated polymer alignment thin film on the substrate by, for example, a friction transfer method, and any liquid crystal can be aligned by using the liquid crystal alignment film. It has also been found that by irradiating the polymer alignment thin film with ultraviolet rays or the like, a part of the polymer can be decomposed or modified to change the alignment of the liquid crystal induced by the film.

  Furthermore, by using this polymer alignment thin film, it is found that a necessary pattern can be formed on the alignment film using an arbitrary light-shielding mask, and a patterned liquid crystal alignment film can be easily produced, thereby completing the present invention. It came to.

That is, the present invention provides the following liquid crystal alignment film, liquid crystal display device, and manufacturing method thereof.
1. A liquid crystal alignment film comprising an alignment thin film of at least one conjugated polymer selected from the group consisting of a sigma conjugated polymer and a pi conjugated polymer.
2. Item 2. The liquid crystal alignment film according to Item 1, wherein a pattern is formed on the alignment thin film.
3. Item 3. The liquid crystal alignment film according to Item 1 or 2, wherein the conjugated polymer is a polysilane. Item 4. A liquid crystal display device using the liquid crystal alignment film of item 1, 2 or 3.
5). At least one conjugated polymer selected from the group consisting of a sigma conjugated polymer and a pi conjugated polymer is pressure-molded, and the conjugated polymer is oriented on the substrate by friction transfer using this. A method for producing a liquid crystal alignment film, comprising forming a thin film.
6). 6. The method for producing a liquid crystal alignment film according to claim 5, further comprising irradiating the alignment thin film with ultraviolet light or visible light to form a pattern on the alignment thin film.

  Hereinafter, the present invention will be described in more detail.

  FIG. 1 schematically shows a method of forming a pattern on the alignment film of the present invention. In the present invention, a polymer alignment film 2 obtained by friction transfer of a conjugated polymer on a substrate 1 is used. In this case, the method for producing an oriented thin film using friction transfer reduces the number of steps because film formation and orientation can be performed simultaneously. Furthermore, when the alignment thin film is formed by friction transfer, the film pressure becomes very thin (for example, about 2 to 100 nm in the case of polysilanes), and the response time for switching the liquid crystal display when a voltage is applied is shortened. This is preferable because the required drive voltage can be reduced. Furthermore, since polysilanes are very thin and have high transparency, it is possible to obtain a liquid crystal display device that is highly visible, thin, and lightweight. Further, it is possible to obtain a liquid crystal display device having high light transmittance and a long lifetime with less burden on a light source device (backlight, sidelight, etc.).

  The thickness of the polymer liquid crystal alignment film of the present invention is usually about 50 to 200 nm.

  Friction transfer can be performed under known conditions as described in Patent Document 1. For example, the temperature of the substrate or conjugated polymer is about 20 to 300 ° C., the pressure when the conjugated polymer is pressed against the substrate is 0.1 to 2 MPa, and the sweep rate is about 30 to 100 cm / min.

  The condition of pattern formability by light (visible light, ultraviolet ray) irradiation is such that light having a wavelength that can be absorbed by a conjugated polymer of about 300 to 500 nm is used for 3 to 90 minutes, for example, using a 100 W xenon lamp, and 10 to 150 ° C. Can be done to the extent.

  When polysilanes are used as the conjugated polymer, a pattern can be formed by cutting polysilane or bonding between silanes (Si-Si) to form a polysiloxane structure (Si-O-Si). Therefore, it is preferable to carry out in the presence of air or oxygen.

  The line width, thickness, etc. of the pattern can be arbitrarily adjusted with a mask.

  The alignment film 2 is molecularly oriented uniaxially in the direction of friction. The alignment thin film 2 of the conjugated polymer is partially decomposed by light irradiation to become a film 4 having an orientation different from that of the unirradiated portion 3. By using the light-shielding mask 5, it is possible to easily form an arbitrary alignment pattern, and it can be used as a liquid crystal alignment film for a liquid crystal display element. In the polymer oriented thin film, a uniform thin film layer may be formed on the substrate. However, even if a defective portion or a very thin portion exists in a part of the thin film, there is no problem as long as the liquid crystal is oriented.

As the conjugated polymer, for example, σ-conjugated polymers such as polysilanes and polygermanes, and π-conjugated polymers such as polyphenylene vinylenes, polyphenylenes, polythiophenes, and polyfluorenes can be used. These monomer components can be used alone or in combination of two or more. Furthermore, derivatives in which an alkyl group, an aryl group, an alkoxy group or the like is bonded to the side chain of these polymers can also be used.

For example, poly (dimethylsilane) (-(Si (CH ₃ ) ₂ )-) can be preferably used as polysilanes.

  These alignment films of conjugated polymers have the ability to align general liquid crystal directors in the direction of the molecular chain, and when sandwiched between two vertically aligned alignment films, the liquid crystal is uniformly horizontal. Orient.

  Conjugated polymers have light absorption in the ultraviolet or visible light region, and chemical changes such as molecular chains are broken or modified by light irradiation or partially heated. At this time, unlike the unirradiated portion, disorder of orientation occurs. The liquid crystal is vertically aligned in the portion irradiated with light.

  Pattern formation by UV irradiation of conjugated polymers (especially polysilanes) is easier than conventional polyimide liquid crystal alignment films, and can form fine and complex patterns. It can respond enough.

  Any liquid crystal can be used as long as it can be aligned by this alignment film.

  A known element structure may be used as the liquid crystal display device. For example, referring to FIG. 2, in order to perform fixed display, a polymer alignment film is formed on two substrates 1A and 1B, a spacer is sandwiched between them, and light is irradiated through a desired light-shielding mask. Thereafter, a liquid crystal is sandwiched between patterned alignment films, and further, a display element is formed by sandwiching the outside with a polarizer (not shown) oriented in an orthogonal direction. In the irradiated portions 4A and 4B, the liquid crystal molecules are vertically aligned and do not transmit light. In the unirradiated portions 3A and 3B, the light deflection direction is changed by the horizontally aligned liquid crystal, and the light passes therethrough. In addition, by using a transparent electrode substrate as the substrate to which the alignment film is provided and using liquid crystal having dielectric anisotropy, the alignment of the liquid crystal only in the horizontal alignment portion is changed by voltage application, and display can be turned on / off.

  The substrate may be a transparent substrate, and a substrate such as glass, plastic, or ITO can be used.

  As described above, it is possible to form a pattern on the liquid crystal alignment film with a simple process compared to the conventional method, and it can be used for an element using liquid crystal such as a liquid crystal display device. For example, it can be used for the manufacture of a simple fixed display element and for the improvement of the viewing angle and the contrast in a liquid crystal display.

Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
This will be described with reference to FIG. Polydimethylsilane (PDMS) powder, which is a kind of polysilanes, was press-molded to make the end faces square and flat. This was crimped and swept onto a glass substrate 1 to form a PDMS thin film 2 on the glass substrate. At this time, the temperature of the glass substrate was 250 ° C., the sweep rate was 1 m / min, and the pressure was 2 MPa. In addition, it is desirable that the atmosphere be dry nitrogen or reduced pressure when forming a PDMS film. The PDMS thin film was oriented so that the molecular chain direction was parallel to the sweep direction.

  Ultraviolet rays were irradiated for 5 minutes through a mask 5 having a linear pattern on the PDMS alignment film. As a result, in the portion 4 irradiated with light, the PDMS partially became a polysiloxane structure by photooxidation. There was no change in the unirradiated part 3. The minimum pattern line width implemented was 0.03 mm.

A description will be given with reference to FIG. Two glass substrates 1A, 1B with the same patterned PDMS alignment films 3A, 3B, 4A, 4B are made to face each other so that the alignment directions are almost the same, and a nematic liquid crystal 6 such as pentylcyanobiphenyl is interposed therebetween. I sandwiched (5CB). This was sandwiched between two polarizers whose deflection directions were orthogonal to each other for observation. In the portion sandwiched between the light-irradiated PDMS films 4A and 4B, 5CB was vertically aligned and did not transmit light. On the other hand, in the part sandwiched between the non-irradiated parts 3A and 3B, 5CB in the orientation direction of PDMS
When light is horizontally aligned and the PDMS alignment direction and the linearly polarized light form an angle of 45 °, light is transmitted.

  In addition, as shown in FIG. 3, when the alignment directions of the two PDMS alignment films are arranged orthogonally and patterned, and the liquid crystal is sandwiched, the liquid crystal 6 is twisted in the portion sandwiched between the non-irradiated portions 3A and 3C. Even when the polarizer was crossed Nicol, it was normally white and allowed light to pass through, and the portion sandwiched between the non-irradiated portions 4A and 4C did not pass light.

It is a figure which shows the method of forming a pattern in a liquid crystal aligning film. It is a figure which shows the orientation of the liquid crystal by the orientation film in which the pattern was formed. It is a figure which shows the orientation of the liquid crystal by the orientation film in which the pattern was formed.

Explanation of symbols

1, 1A, 1B Substrate 2 Conjugated polymer alignment film 3, 3A, 3B, 3C alignment film (unirradiated part)
4, 4A, 4B, 4C alignment film (irradiation part)
5 Shading object (mask)
6 Liquid crystal

Claims (2)

Polysilanes are pressure-molded, and a thin film in which the polysilanes are uniaxially oriented is formed on a substrate by using a friction transfer method. The irradiated thin film is irradiated with ultraviolet rays or visible light, and the irradiation is performed. A method for producing a liquid crystal alignment film, wherein a pattern is formed on the alignment thin film by changing the alignment of the polysilanes in the portion .   The method for producing a liquid crystal alignment film according to claim 1, wherein the polysilane is polydimethylsilane.

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