JP2008175972A - Rubbing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubbing method by which the occurrence of discharge defects accompanying a rubbing operation is reduced. <P>SOLUTION: The rubbing method is characterized by using a velvet obtained by weaving cellulose based pile yarn containing the warp, the weft, and conductive fine particles such as carbon black, cutting the woven tissue having a woven structure with the pile yarn woven between two sheets of base cloths into two sheets, and continuously rubbing a long thermoplastic resin film with a fixed angle of 45° and with a squeeze of a rubbing nap of the rubbing cloth set to be 0.7 mm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubbing method.

  Viewing angle improvement plate, retardation plate, color compensation plate, etc. obtained by directly forming a liquid crystal polymer layer on an alignment substrate film or transferring the liquid crystal polymer layer onto a translucent substrate film The liquid crystal optical film is known. In such an oriented substrate film, a rubbing roll with a rubbing cloth attached is rotated in a certain direction, and the fiber bristle of the rubbing cloth rubs the surface of the polymer substrate film that becomes the oriented substrate film in a certain direction. Can be obtained.

  In the rubbing process, static electricity is generated by rubbing the rubbing cloth and the polymer substrate film, and the substrate film is charged. When this charging causes a discharge, the surface state on the substrate film changes, and the alignment ability of the liquid crystal changes, resulting in a defect called a discharge defect. When a discharge defect occurs, the production yield is greatly reduced, and a solution is desired.

As methods for solving such discharge defects, the following methods have been proposed.
The method proposed in Patent Document 1 is to rub in an atmosphere having a humidity of 50% or more to reduce static electricity generated by friction between the substrate and the rubbing cloth.
In the method proposed in Patent Document 2, rubbing is performed in an atmosphere having a humidity of 50 to 70%, and static electricity generated by friction between the substrate and the rubbing cloth is reduced.
The method proposed in Patent Document 3 is to reduce static electricity generated by friction between the substrate and the rubbing cloth by performing the orientation treatment with the moisture content of the rubbing cloth being 8% to 12%.
However, these methods are not sufficient in reducing discharge defects, and further improvement has been desired.
JP-A-1-225918 JP-A-5-249467 Japanese Patent Laid-Open No. 11-271776

  The present invention has been made in view of such circumstances, and provides a rubbing method in which the occurrence of discharge defects in a product is small.

  The present invention is obtained by weaving a cellulose pile yarn containing warp, weft and conductive fine particles, and cutting a woven structure having a woven structure in which a pile yarn is woven between two base fabrics into two pieces. The present invention relates to a rubbing method comprising continuously rubbing a long film using the obtained velvet fabric.

  According to the rubbing method of the present invention, the occurrence of defects in the product can be greatly suppressed, and the production yield can be improved. In addition, since the occurrence of defects can be suppressed, it is possible to cope with higher definition of liquid crystal display devices and liquid crystal optical films.

Hereinafter, the present invention will be described in detail.
In the rubbing method of the present invention, a velvet fabric obtained by weaving warp yarns, weft yarns and pile yarns and cutting a woven structure having a woven structure in which pile yarns are woven into two pieces between two base fabrics. Use. Weaving a betting fabric that weaves one weft of a base fabric obtained by weaving warp and weft to make a pile yarn, and two knitted yarns, one of which is pulled out as a pile yarn and cut Compared with the case where a knitted velor fabric made into a cut pile is used, it is preferable because the uprightness of the pile is excellent.

  Cotton, rayon, polyester, acetate, nylon and the like are used as the warp and weft, but are not particularly limited thereto. Moreover, in order to improve discharge defect tolerance, the below-mentioned cellulose conductive yarn may be used as the warp and the weft.

  Cellulose yarn is used as the pile yarn used in the present invention. The term “cellulose-based yarn” as used herein refers to filaments (long fibers) or short fibers such as viscose rayon, cupra ammonium rayon, high-strength rayon having a polymerization degree of 400 to 500, and cellulose-based fibers such as organic solvent-based cellulose fibers. Among the fiber types, viscose rayon is preferred, and the use of filaments that are long fibers is preferred from the viewpoint of dust generation.

  Examples of the conductive fine particles contained in the pile yarn include carbon black, metal powder, metal oxide and the like, and carbon black is particularly preferable.

  The fineness of the pile yarn can be selected in the range of 0.5 to 8 denier, preferably 0.8 to 6 denier, and more preferably 2 to 6 denier. If the fineness is less than 0.5 denier, the yarn is likely to be cut during rubbing, and if it exceeds 7 denier, the fiber diameter becomes large and scratches are generated on the oriented substrate film during rubbing.

Examples of the weaving structure of the rubbing cloth used in the present invention include structures usually used as velvet weaving such as V weaving and W weaving, but are not particularly limited thereto.
A typical method for producing a rubbing cloth using the pile yarn thus obtained will be described below.
After warping the pile yarn, weaving with a loom with the desired weaving structure, cutting it into two pieces, adjusting the pile length by shirring, and passing through the back coat resin forming step, the present invention A rubbing cloth to be used can be obtained.
Examples of the back coat resin include rubber systems such as vinyl acetate, acrylic, and SBR. It is preferable that the back coat resin be conductive in order to provide conductivity with a rubbing cloth.

The filament density of the rubbing cloth cannot be determined unconditionally depending on the fineness, material, strength, etc. of the pile yarn, but is usually 100 to 600 (unit: 1,000 filaments / inch ² ; the same applies hereinafter), preferably 120 to 400, more preferably 150. It can be selected in the range of ~ 250. If the filament density is less than 100, the rubbing density is small, which causes rubbing streaks. If the filament density is more than 600, the filament density is too high, and there is a possibility that the hair may be disturbed.

The pile length including the base cloth thickness of the rubbing cloth can be selected in the range of 1.0 mm to 7.0 mm, preferably 1.5 mm to 6.5 mm. If the pile length is less than 1.0 mm, the rubbing roll body and the alignment substrate may come into contact if the rubbing roll is slightly decentered, and if it is greater than 7.0 mm, the alignment may be disturbed. Therefore, it is not desirable.
Note that the rubbing cloth of the present invention may be subjected to a washing step or a resin impregnation step, if necessary.

Next, the rubbing method of the present invention will be described.
First, a rubbing treatment is performed on a polymer substrate film (long film) serving as an alignment substrate using the rubbing cloth obtained above. This rubbing treatment can be performed at an arbitrary angle with respect to the length direction (MD) of the long film.

  The polymer that becomes a long film is such that the surface is physically or physicochemically modified by rubbing treatment, and then liquid crystal molecules that come into contact with the rubbing treatment surface can be aligned corresponding to the rubbing treatment. Any of these may be employed, and may be either a thermosetting resin or a thermoplastic resin. For example, thermosetting resins such as polyimide, epoxy resin, phenol resin, polyamide, polyether imide, polyether ketone, poly Polyester such as ether ether ketone (PEEK), polyketone, polyether sulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polycarbonate, poly (meth) acrylate, triacetylce Cellulose resins such as loin (TAC), and thermoplastic resins such as polyvinyl alcohol.

  The polymer film itself can be rubbed, and the surface activity of these polymer films having a base material on the surface thereof, such as polyvinyl alcohol, polyimide, and various long-chain alkyl groups. The thing formed by forming organic thin films (alignment film), such as an agent, is also illustrated. In addition to the polymer film, the base material on which such an alignment film is formed may be a metal foil such as copper, stainless steel, and steel.

  The method for forming the alignment film on the long film can be based on a method such as a roll coater or a die coater because the substrate is a long film. For example, a method of coating a thermosetting resin solution such as polyimide and then heat-curing to obtain an alignment film, or a method of coating a thermoplastic resin solution such as polyvinyl alcohol and then removing the solvent to obtain an alignment film Can be adopted.

Particularly preferable as the polymer constituting the long film or alignment film subjected to the rubbing treatment is a thermosetting resin such as polyimide or a thermoplastic resin such as polyethylene terephthalate, polyphenylene sulfide, PEEK, or polyvinyl alcohol. These are preferable because they have high heat resistance and the rubbing treatment is stably stored even in a heating operation for aligning liquid crystal molecules described later.
Such a film can be easily obtained as a long continuous film by a molding method such as a normal T-die extrusion method. Although thickness can be selected suitably, it can employ | adopt from the range of 10 micrometers-1 mm, for example. Although the width is also appropriate, it is usually selected from the range of 1 to 500 cm.
Moreover, said film can be a film suitably extended | stretched to the uniaxial direction or the biaxial direction by the well-known method in the range which does not prevent the effect by the rubbing process mentioned later.

  In the rubbing process, rubbing is performed at a predetermined arbitrary angle with respect to the MD of the long film, preferably at an angle of 0 to 45 degrees. This angle (rubbing angle) is an angle in the clockwise direction from the MD when the rubbing surface is viewed from above.

  The rubbing process can be performed by any method. For example, as one of the methods, a long film (12) as an alignment substrate is placed on a stage (11) that conveys the long film (12) to the MD, and a rubbing roll at an arbitrary angle with respect to the MD (12) and the MD. (10) is placed, the rubbing roll (10) is rotated while the long film (12) is being conveyed, and the surface of the film (12) is rubbed. The angle formed by the rubbing roll (10) and the moving direction of the stage (11) is a mechanism that can be freely adjusted.

On the surface of the rubbing roll, the rubbing cloth of the present invention is stuck.
In the rubbing treatment, it is important to rub the alignment substrate surface in a certain direction in consideration of the hardness of the alignment substrate surface. From this point of view, the rubbing pressure, the number of rotations of the rubbing roll, etc. are set appropriately. Usually, the alignment substrate is moved at a speed of 0.5 to 100 m / min, preferably 1 to 30 m / min, and the number of rotations of the rubbing roll is selected from the range of 1 to 1000, preferably 5 to 200 as the peripheral speed ratio. The The rubbing pressure may be such that the surface of the rubbing cloth is slightly touched, and the pushing-in degree of the bristles of the rubbing cloth is 0.1 mm to 5.0 mm, preferably about 0.1 mm to 2.0 mm. If necessary, a cleaning treatment may be performed by spraying a pressurized gas on the rubbed surface, contacting with an adhesive roll, or the like.

The long film subjected to the rubbing treatment is then laminated so that the rubbing surface is in contact with the liquid crystal molecules. The liquid crystal molecules are aligned according to the rubbing surface that has been subjected to the rubbing treatment.
The liquid crystal molecules to be laminated are preferably thermotropic liquid crystals that exhibit liquid crystallinity when melted. The structure of the liquid crystal phase at the time of melting may be any molecular arrangement structure of smectic, nematic, twisted nematic (cholesteric), or discotic. The thermotropic liquid crystal molecules selected here include, for example, a low molecular rod-like liquid crystal having a reactive group such as an acryloyl group, an oxiranyl group, an oxetanyl group, a vinyloxy group, an acid anhydride group, and a group having active hydrogen. Discotic liquid crystals, main-chain and side-chain liquid crystalline polymers (polymers) having these reactive groups, and especially those having no reactive groups, but the temperature is lower than the glass transition temperature from the liquid crystal phase formation temperature A liquid crystalline polymer that becomes a glass state while maintaining the molecular alignment state of the liquid crystal phase when cooled to a temperature can also be used. A low-molecular liquid crystal and a liquid crystalline polymer can be used in a suitable mixture. Further, the optically active group required for the expression of the cholesteric liquid crystal phase may be a form bonded to the liquid crystal molecule or a form in which another compound having an optically active group is added.
Examples of the main chain type liquid crystalline polymer include polyester, polyamide, polyester amide, and polycarbonate, and examples of the side chain type liquid crystalline polymer include poly (meth) acrylate, polymalonate, and polysiloxane.
Among these liquid crystal molecules, those mainly composed of a liquid crystalline polymer are preferable.

In particular, in the case of a liquid crystalline polymer having no reactive group, the number average molecular weight in terms of polystyrene by GPC is preferably 1000 to 100,000, more preferably 3000 to 20000, regardless of the main chain type or the side chain type. Some liquid crystalline polymers are sparingly soluble in solvents and difficult to measure molecular weight by GPC. In such a case, the logarithmic viscosity measured at 30 ° C in various solvents for dissolving the liquid crystalline polymer, for example, a mixed solvent of phenol / tetrachloroethane (60/40 mass ratio), is 0.05 to 3.0. Preferably, 0.07 to 2.0 is more preferable.
When the number average molecular weight is less than 1000 or the logarithmic viscosity is less than 0.05, the strength of the obtained liquid crystalline polymer is low, and when the number average molecular weight exceeds 100,000 or the logarithmic viscosity exceeds 3.0 Since the viscosity at the time of liquid crystal phase formation is too high, problems such as a decrease in alignment and an increase in time required for alignment occur, which is not preferable.
In addition, the liquid crystalline polymer having a reactive group does not have to be limited as described above because the liquid crystal phase can be easily retained after the alignment due to an increase in molecular weight or crosslinking due to the reaction. Those within this range are preferred.

  The liquid crystal molecules are formed on the rubbing surface of the long film by an arbitrary method. For example, it is possible to use a method of forming a film by dissolving in an appropriate solvent and applying and drying, or a method of directly melting and extruding liquid crystal molecules with a T die or the like. From the viewpoint of quality such as film thickness uniformity, a method of applying a solution and drying is suitable. As described above, the meaning of the long film in the present invention means a continuous film having a certain length, and industrially means a continuous film that can be supplied in a rolled form. Of course, the form of roll winding is not essential, and a continuous film folded appropriately may be used. In some cases, the length of the long film may reach a length of 10,000 m.

  In the formation of the liquid crystal molecular layer, first, liquid crystal molecules are dissolved in a solvent at a predetermined ratio to prepare a solution. The solvent used here varies depending on the type of liquid crystal, but usually ketones such as acetone, methyl ethyl ketone and cyclohexanone, ethers such as tetrahydrofuran and dioxane, halogenated carbonization such as chloroform, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene and orthodichlorobenzene. Hydrogen, various phenols, amide solvents such as dimethylformamide and dimethylacetamide, solvents such as dimethyl sulfoxide and N-methylpyrrolidone, and mixed solvents thereof can be used. The concentration of the solution varies depending on the viscosity of the solution, but is usually in the range of 5 to 50% by mass, and preferably in the range of 10 to 30% by mass. In addition, various additives, for example, various polymers that can improve the film-forming property, various surfactants, photoreaction initiators, radical initiators, and the like as long as liquid crystallinity is not disturbed during solution preparation (Initiator) agents, crosslinking agents, fluidity improvers, dyes, and the like may be added.

Next, this solution is applied onto a long film formed by rubbing the MD at a predetermined angle.
The coating method is not particularly limited, and for example, a die coating method, a slot die coating method, a slide die coating method, a roll coating method, a bar coating method, a dip pulling method, or the like can be employed. After coating, the solvent is appropriately removed by drying.

After the liquid crystal molecular layer is formed on the rubbed long film, it is heated at a predetermined temperature for a predetermined time to align the liquid crystal and, if necessary, reacted under conditions suitable for the reactive group to react. By cooling, the alignment of the liquid crystal molecules is fixed.
The temperature at which the liquid crystal is aligned is preferably such that the viscosity of the coating layer is low in order to assist the alignment by the interface effect. That is, the heating temperature is preferably higher if it is lower than the isotropic phase transition temperature of the liquid crystal molecules. However, an excessively high temperature is not preferable because the workability deteriorates with the deformation of the long film and the thermal decomposition of the liquid crystal molecules. From this viewpoint, it is generally selected from the range of 50 to 300 ° C., preferably 80 to 250 ° C., and 10 seconds to 60 minutes, preferably 30 seconds to 30 minutes. The heating means can be appropriately employed, and examples thereof include hot air heating, infrared heating, dielectric heating, heating by an electric heater, heating by a hot roll, and the like.
In any case, it is important to perform a heat treatment for a time during which the liquid crystal molecules are sufficiently aligned at a temperature higher than the glass transition temperature and lower than the transition temperature to the isotropic phase.
After alignment by heating and, if necessary, reacting a reactive group, the alignment is fixed by cooling to the glass transition temperature or lower of the liquid crystal molecules.
The cooling rate is not particularly limited and is arbitrarily selected. For example, the heated liquid crystal molecular layer is fixed only by moving from the heating region to an atmosphere below the glass transition point. For the purpose of improving production efficiency, air cooling or cooling of coolant such as water can be employed.

  The film thickness of the liquid crystal molecular layer after immobilization is not particularly limited as long as it is a range that functions depending on the use and purpose of the liquid crystal molecular layer. Although it varies depending on the wavelength of light, it is 0.05 μm or more, preferably 0.3 μm or more in a field where visible light is important, for example, for display applications. If the thickness is less than 0.05 μm, it is difficult to adjust the film thickness with high accuracy. The upper limit of the film thickness is not particularly limited, but if it is too thick, the regulating power as an optical element is weakened, which is not preferable. From this viewpoint, a range of 100 μm or less, preferably 30 μm or less is appropriate.

  The liquid crystal optical film of the present invention obtained by the method as described above is a substrate in which the long film as a substrate itself is a translucent substrate, and a laminated body in which a liquid crystal molecular layer is fixed is used as it is or appropriately. It can be used for an optical element by combining with other optical materials such as a polarizing plate. In addition, when the long film exhibits unfavorable light absorption and optical anisotropy in the final use of the liquid crystal optical film, the liquid crystal molecular layer aligned and fixed on the appropriate translucent substrate as the support is transferred. Finally, it can be used as an optical element.

  The translucent substrate is not particularly limited as long as it has transparency and optical isotropy and can support the liquid crystal molecular layer, but is preferably a long one, such as a plastic film such as polymethyl methacrylate, polystyrene, Examples include polycarbonate, polyether sulfone, polyarylate, amorphous polyolefin, triacetyl cellulose (TAC) and the like. The thickness of these translucent substrates is not particularly limited, but is usually selected from the range of 1 to 500 μm.

Transition to the translucent substrate can be performed by any method, for example, by a transfer method.
This method is a method in which a liquid crystal molecular layer is adhered and transferred with an appropriate adhesive. Any adhesive layer can be used as long as it is translucent and optically isotropic, and acrylic, epoxy, ethylene-vinyl acetate, rubber, and the like can be used. Preferably, the acrylic adhesive is used.

  Examples of the present invention are shown below, but the present invention is not limited to these embodiments.

  Weaving long fiber viscose rayon containing carbon black as pile yarn, weave viscose rayon, warp yarn and weft yarn, and weaving structure with V weave structure in which pile yarn is woven between two base fabrics A velvet fabric obtained by cutting into sheets is subjected to rubbing using a rubbing cloth having a filament density of 200 and a pile length of 2.6 mm obtained through a back coating resin forming step, and a method for producing a liquid crystal optical film described later When the liquid crystal optical film was manufactured according to the above, no discharge defects occurred.

[Comparative Example 1]
Weaving long fiber viscose rayon, warp and weft yarns with a fineness of 3.0 denier as pile yarn, and cutting the weaving structure having a V-weaving structure with pile yarn between the two base fabrics into two pieces The obtained velvet fabric is rubbed and rubbed with a rubbing cloth having a filament density of 180 and a pile length of 2.6 mm obtained through the back coat resin forming step, and a liquid crystal optical film according to a method for producing a liquid crystal optical film described later. As a result, discharge defects occurred.

[Comparative Example 2]
Weaving long fiber viscose rayon, warp and weft yarns with a fineness of 3.0 denier as pile yarn, and cutting the weaving structure having a V-weaving structure with pile yarn between the two base fabrics into two pieces The obtained velvet fabric is subjected to rubbing using a rubbing cloth having a filament density of 220 and a pile length of 2.6 mm obtained through a process of forming a back coat resin, and a liquid crystal optical film according to a method for producing a liquid crystal optical film described later. As a result, discharge defects occurred.

(Manufacturing method of liquid crystal optical film)
With the apparatus shown in Fig. 1, the rubbing roll having a diameter of 150 mm around which the rubbing cloth of Example 1 or Comparative Examples 1 and 2 is wound is conveyed against the MD of the thermoplastic resin long film while conveying the long film made of thermoplastic resin. The rubbing cloth was continuously rubbed at a peripheral speed ratio of 28 with the tip of the rubbing cloth pushed in at 0.7 mm and wound on a roll.
The polymer solution containing the liquid crystalline polyester was applied on the above-mentioned rubbing-treated polymer long film and then dried, heat-treated and cooled to room temperature to fix the orientation of the liquid crystalline polymer.
From the laminate of the liquid crystalline polymer layer and the long film, the liquid crystalline polymer layer was transferred to the TAC film by an acrylic adhesive using a conventional method.
Next, an overcoat layer was laminated on the liquid crystalline polymer layer of the obtained liquid crystalline polymer / TAC long laminate sheet to obtain a liquid crystal optical film.

  According to the rubbing method of the present invention, it is possible to reduce defects in a liquid crystal display device or a liquid crystal optical film such as a viewing angle improving plate, a retardation plate, a color compensation plate, etc. derived from the rubbing of the alignment substrate. It can cope with high definition of the device and the liquid crystal optical film.

It is a top view of the apparatus which rubs a long film-like orientation board | substrate at arbitrary angles with respect to the MD.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Rubbing roll 11 Stage 12 which conveys alignment board Long film-like alignment board

Claims (1)

  Velvet fabric obtained by weaving cellulose pile yarn containing warp, weft and conductive fine particles, and cutting the weave structure having a weave structure with pile yarn between two base fabrics into two pieces A rubbing method comprising continuously rubbing a long film using

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