JP2010020207A - Method for producing optical laminate - Google Patents

Abstract

The present invention provides a method for manufacturing an optical laminate having a liquid crystal alignment layer, which is free from fibrous foreign matter and has excellent productivity.
A method of manufacturing an optical laminate including a liquid crystal alignment layer formed on a surface of a base material, the adhesive tape being attached to the surface of the base material, and then peeling the adhesive tape in one direction. A method for producing an optical laminate comprising: removing step A; and applying a coating liquid containing a liquid crystal compound to the surface of the substrate from which the adhesive tape has been removed to form a liquid crystal alignment layer.
[Selection] Figure 1

Description

  The present invention relates to a method for producing an optical laminate having a liquid crystal alignment layer on the surface of a substrate.

A method is known in which a polarizing film is produced by applying an aqueous solution containing a tabular dye on the surface of a rubbed substrate, drying it, and orienting the tabular dye (Patent Document 1). However, the rubbing treatment used in the conventional method adds orientation regulating force by rubbing the surface of the substrate with a fiber cloth. Since this fibrous foreign matter has a size of several tens of μm, if it is present on the surface of the base material, it causes alignment failure when a coating liquid containing a liquid crystal compound is applied, for example. On the other hand, if the substrate is washed to remove the fibrous foreign matter, the manufacturing process becomes longer and the productivity deteriorates.
JP 2002-311246 A

  An object of the present invention is to provide a method for producing an optical laminate having a liquid crystal alignment layer, which does not generate a fibrous foreign matter and is excellent in productivity.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors applied an adhesive tape to the surface of the base material and peeled it in one direction to remove it, thereby imparting an alignment regulating force to the surface of the base material. As a result of finding the orientation, the present invention was completed. The orientation regulating force obtained by peeling the adhesive tape is because the adhesive component having an anisotropic shape remains slightly on the substrate surface after peeling the adhesive tape, or the molecules on the surface of the substrate (for example, polymer film) This may be due to orientation in one direction or both.

一般式（１）中、Ｒは水素原子、炭素数１〜３のアルキル基、アセチル基、ベンゾイル基、または置換基を有していてもよいフェニル基を表わし、Ｍは水素原子、アルカリ金属原子、またはアルカリ土類金属原子からなる対イオンを表わし、Ｘは水素原子、ハロゲン原子、ニトロ基、シアノ基、炭素数１〜４のアルキル基、炭素数１〜４のアルコキシ基、または−ＳＯ_３Ｍ基を表わす。 The gist of the present invention is as follows.
(1) The manufacturing method of the optical laminated body of this invention is a manufacturing method of the optical laminated body provided with the base material and the liquid crystal aligning layer formed in the surface of a base material, Comprising: Adhesive tape is provided on the surface of a base material. Step A after peeling and removing the adhesive tape in one direction, and Step B for forming a liquid crystal alignment layer by applying a coating liquid containing a liquid crystal compound to the surface of the substrate from which the adhesive tape has been removed It is characterized by that.
(2) The method for producing an optical laminate of the present invention is characterized in that the liquid crystal compound is an azo compound represented by the following general formula (1).

In general formula (1), R represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an acetyl group, a benzoyl group, or an optionally substituted phenyl group, and M represents a hydrogen atom or an alkali metal atom. Or a counter ion composed of an alkaline earth metal atom, wherein X is a hydrogen atom, a halogen atom, a nitro group, a cyano group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or —SO _3. Represents the M group.

  According to the manufacturing method of the present invention, since no rubbing treatment using a fiber cloth is performed, no fibrous foreign matter is generated, and a cleaning step for removing the fibrous foreign matter is unnecessary. For this reason, the manufacturing method with high quality and excellent productivity can be obtained.

[Production method of the present invention]
The production method of the present invention is a method for producing an optical laminate comprising a substrate and a liquid crystal alignment layer formed on the surface of the substrate, and includes a step A and a step B described later. The production method of the present invention may include any other step as long as it includes step A and step B. As such other steps, after sticking the adhesive tape on the surface of the base material and peeling it in one direction, the surface on which the adhesive tape is stuck is subjected to a hydrophilic treatment (for example, corona treatment, plasma treatment), etc. Is mentioned.

  FIG. 1 compares the conventional method and the production method of the present invention. When the substrate is not cleaned after the rubbing process according to the conventional method, the productivity is good, but alignment failure due to the fibrous foreign matter is likely to occur. When the substrate is cleaned after the rubbing process according to the conventional method, poor alignment due to fibrous foreign matter does not occur, but productivity is poor. The production method of the present invention, which replaces the rubbing treatment, has good productivity and no orientation failure due to fibrous foreign matter.

[Step A]
Step A used in the present invention is a step in which the adhesive tape is adhered to the surface of the substrate and then removed in one direction. According to this step, the orientation regulating force can be applied without subjecting the surface of the substrate to a rubbing treatment. The liquid crystal compound can be aligned when the coating liquid containing the liquid crystal compound is applied to the surface of the substrate by this alignment regulating force.

  The substrate is not particularly limited, and any substrate such as a glass plate or a polymer film is used. However, the production method of the present invention is particularly suitable for a hydrophobic polymer film having few hydrophilic functional groups. A typical example of the hydrophobic polymer film is a norbornene polymer film. The thickness of the substrate is preferably 10 μm to 200 μm.

  The pressure-sensitive adhesive tape has a pressure-sensitive adhesive formed on at least one surface. The adhesive is a viscoelastic body having an adhesive tack. The pressure-sensitive adhesive may be a rubber-based pressure-sensitive adhesive mainly composed of natural rubber or synthetic rubber, or may be an acrylic pressure-sensitive adhesive mainly composed of a copolymer of an acrylic monomer and a functional group-containing monomer. The thickness of the adhesive tape is preferably 10 μm to 80 μm.

  There is no restriction | limiting in particular in the method of sticking an adhesive tape on the base-material surface, For example, a commercially available laminator (sticking apparatus) is used. The adhesive strength of the adhesive tape varies depending on the adherend. For example, when the adherend is a norbornene-based polymer film and measured by a 90 ° peel test method according to JIS Z 0237-1980, preferably 4N / 18 mm to 10 N / 18 mm.

  There is no restriction | limiting in particular in the method of peeling an adhesive tape in one direction, You may peel once and may peel in multiple times. The peel angle of the adhesive tape is preferably 90 ° to 180 ° with respect to the substrate plane. The peeling speed of the adhesive tape is preferably 1 mm / second to 5 m / second. Under such conditions, a liquid crystal alignment layer with better uniformity can be obtained.

[Step B]
Step B used in the present invention is a step of forming a liquid crystal alignment layer by applying a coating liquid containing a liquid crystal compound to the surface of the substrate to which the adhesive tape has been attached in Step A.

  The coating solution used in the present invention preferably contains a solvent and a liquid crystal compound, and preferably contains 0.1 to 40% by weight of the liquid crystal compound based on the total weight of the coating solution.

  The liquid crystal compound is not particularly limited, and any liquid crystal compound such as a thermotropic liquid crystal compound or a lyotropic liquid crystal compound can be used. However, the production method of the present invention is particularly effective for a lyotropic liquid crystal compound having poor alignment.

  Examples of the lyotropic liquid crystal compound include those described in JP2007-126628A and JP2006-323377A. The lyotropic liquid crystal compounds described in these publications exhibit light absorption in at least one wavelength in the visible light region (wavelength of 380 nm to 780 nm), and thus can be used as a polarizing film by being oriented.

The lyotropic liquid crystal compound is preferably an azo compound represented by the following general formula (1). Such an azo compound exhibits stable liquid crystallinity and excellent orientation when dissolved in a solvent. Furthermore, since the azo compound of the general formula (1) has a —SO ₃ M group at a specific position as shown in the general formula (1), the steric hindrance between the —SO ₃ M groups is reduced, and the molecules before and after the water resistance treatment. Thus, a polarizing film having a high degree of orientation is obtained.

In general formula (1), R represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an acetyl group, a benzoyl group, or an optionally substituted phenyl group. M represents a counter ion, preferably a hydrogen atom, an alkali metal atom, or an alkaline earth metal atom. X represents a hydrogen atom, a halogen atom, a nitro group, a cyano group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an —SO ₃ M group.
The lyotropic liquid crystal compound typically forms a supramolecular aggregate in a solvent. When a coating liquid containing a lyotropic liquid crystal compound is applied onto an alignment-treated substrate, the major axis direction of the supramolecular aggregate is aligned in the alignment treatment direction in the process of evaporation of the solvent. As a result, an alignment layer of the lyotropic liquid crystal compound is obtained.
The method for applying the coating liquid is not particularly limited, and a slide coater, a slot die coater, a tension web coater, a bar coater, or the like is used. As a method for evaporating the solvent, any means such as natural drying, reduced pressure drying, and heat drying may be used. The residual water content in the alignment layer of the lyotropic liquid crystal compound is preferably 5% by weight or less of the total weight of the alignment layer.

[Optical laminate]
The optical laminate obtained by the production method of the present invention includes a substrate and a liquid crystal alignment layer formed on the surface of the substrate. The liquid crystal alignment layer preferably exhibits absorption dichroism in at least one wavelength in the visible light region (wavelength 380 nm to 780 nm). Such a liquid crystal alignment layer can be used as a polarizing film. In this case, the degree of polarization of the liquid crystal alignment layer obtained from the Y value corrected for visibility is preferably 95% or more. Although there is no restriction | limiting in particular in the thickness of a liquid crystal aligning layer, Preferably it is 0.1 micrometer-10 micrometers.

[Use of liquid crystal alignment film]
The liquid crystal alignment layer obtained by the production method of the present invention is suitably used as a polarizing element for a liquid crystal television, a computer display, a mobile phone, a game machine, a digital camera, a video camera, a car navigation, a copying machine, and the like.

[Example 1]
Diazotization of 4-nitroaniline and 8-amino-2-naphthalenesulfonic acid according to a conventional method (Toyo Hosoda, “Theoretical Manufacturing, Dye Chemistry, 5th Edition”, issued July 15, 1968, Technique Hall, pages 135-152) And a coupling reaction to obtain a monoazo compound. Similarly, this monoazo compound is diazotized by a conventional method, and is further subjected to a coupling reaction with 1-amino-8-naphthol-2,4-disulfonic acid lithium salt to obtain a crude product containing an azo compound of the following structural formula (2). Obtained. The crude product was salted out with lithium chloride to obtain an azo compound of the following structural formula (2). This azo compound is a lyotropic liquid crystal compound.

  The azo compound of the structural formula (2) was dissolved in ion exchange water to prepare an aqueous solution having an azo compound concentration of 20% by weight. This aqueous solution was collected with a poly dropper, sandwiched between two glass slides, and observed with a polarizing microscope at room temperature (23 ° C.), and a nematic liquid crystal phase was observed. The aqueous solution was further diluted with ion-exchanged water to prepare a liquid crystalline coating solution having an azo compound concentration of 5% by weight.

  A masking tape (product name “No. 7239” manufactured by Nitto Denko Corporation), which is an adhesive tape, is applied to the surface of the norbornene polymer film (product name “ZEONOR” manufactured by Nippon Zeon Co., Ltd.). Was peeled off in one direction at a peeling angle of 90 °. The adhesive strength of the adhesive tape at this time was 3 N / 18 mm, and the peeling speed was 10 mm / second.

  The film surface on which the adhesive tape was stuck was subjected to corona treatment as a hydrophilic treatment. The above liquid crystalline coating solution was applied to the corona-treated surface using a bar coater (trade name “Mayerrot HS4” manufactured by BUSCHMAN). This was naturally dried in a constant temperature room at 23 ° C. to produce an optical laminate including a norbornene polymer film and a liquid crystal alignment layer formed on the surface thereof. This liquid crystal alignment layer was a polarizing film having a light absorption axis in a direction perpendicular to the peeling direction of the adhesive tape. The liquid crystal alignment layer had a uniform alignment state and almost no alignment failure was observed.

[Example 2]
A norbornene-based polymer film and a liquid crystal alignment layer formed on the surface thereof are provided in the same manner as in Example 1 except that the adhesive tape is replaced with a damplon tape (trade name “No. 3705 Super” manufactured by Nitto Denko Corporation). An optical laminate was prepared. The liquid crystal alignment layer had a uniform alignment state and almost no alignment failure was observed.

[Measuring method]
[Observation of liquid crystal phase]
A small amount of the coating solution was sandwiched between the two slide glasses, and observation was performed using a polarizing microscope (trade name “OPTIPHOT-POL” manufactured by Olympus).

[Alignment state of liquid crystal alignment layer]
The liquid crystal alignment layer was sandwiched between two polarizing plates, and the uniformity of transmitted light that changed when the liquid crystal alignment layer was rotated was evaluated visually.

Comparison diagram of conventional method and manufacturing method of the present invention

Claims (2)

A method for producing an optical laminate comprising a substrate and a liquid crystal alignment layer formed on the surface of the substrate, the adhesive tape being attached to the surface of the substrate, and then peeling the adhesive tape in one direction And removing process A,
And a step B of forming a liquid crystal alignment layer by applying a coating liquid containing a liquid crystal compound to the surface of the base material from which the adhesive tape has been removed. The method for producing an optical laminate according to claim 1, wherein the liquid crystal compound is an azo compound represented by the following general formula (1).

(In General Formula (1), R represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an acetyl group, a benzoyl group, or an optionally substituted phenyl group, and M represents a hydrogen atom or an alkali metal. X represents a hydrogen atom, a halogen atom, a nitro group, a cyano group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or -SO ₃ represents an M group.)

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