JP2008197522A - Method of manufacturing optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a high-quality optical film having few defects such as small alignment error, scratch and discharge mark of a birefringent layer formed on a rubbed alignment film. <P>SOLUTION: The method of manufacturing the optical film comprises a step for forming the alignment film on a base material, a step for rubbing the formed alignment film and a step for forming the birefringent layer on the rubbed alignment film. The quantity of ionic impurities in the alignment film is ≤2,000 mass ppm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical film useful in a liquid crystal display field, an optical field, an optoelectronic field, and the like, and a manufacturing method thereof.

Liquid crystalline films that use liquid crystal as a film material are useful as optical films for liquid crystal displays, etc., but the quality standards required for liquid crystalline films have become increasingly strict in recent years as the display becomes more precise. .
As a method for producing a liquid crystalline film, there is a method in which a thin film of a liquid crystal substance is formed on an alignment substrate to align the liquid crystal and fix the alignment. It is common to use a rubbing-treated substrate as this alignment substrate. The rubbing treatment is performed by rotating a roll around which a cloth (rubbing cloth) is wound and rubbing the traveling substrate. For example, a method in which a substrate on which an alignment film is formed is rubbed is used, for example, in Patent Documents 1 and 2, and a method in which a plastic film is directly rubbed and used as an alignment substrate film is disclosed in, for example, Patent Document 3. Has been. The method using the alignment film is advantageous in terms of quality, but has a problem that the formation of the alignment film is expensive and the number of steps increases. In this respect, the method using no alignment film is advantageous in terms of cost and productivity.

  The alignment of the liquid crystal is greatly influenced by the state of the plastic film or sheet serving as the alignment substrate to be used and the surface of the alignment film. The cause is that the alignment regulation force changes due to minute protrusions on the surface or a small amount of impurities on the substrate surface, causing an abnormality in the alignment, resulting in an alignment failure. Although a strong rubbing method has been proposed as a method for strengthening the alignment regulating force, there are increased defects caused by an increase in dust accompanying the rubbing and scratches on the surface to be rubbed. In order to suppress dust generation and scratches, it is desired to increase the hardness of the alignment film material. On the other hand, the impurities may be mixed from the manufacturing process, but it is also required to reduce the amount of impurities accompanying the manufacturing process of the alignment film material and reduce the alignment abnormality.

For example, polyvinyl alcohol (PVA) or polyimide is known as an organic material used as an alignment film applied on a substrate, and many improvements have been reported.
For example, in PVA, a method of controlling the orientation of liquid crystals by the degree of saponification or chemical modification is known (see, for example, Patent Documents 4, 5, and 6).
However, although various studies have been made on the amount of ionic impurities contained in liquid crystals and their removal, there is little interest in ionic impurities contained in alignment films that are expected to affect the alignment of liquid crystals. The current situation is not paid.
Japanese Patent Laid-Open No. 08-152515 Japanese Patent Laid-Open No. 08-160429 Japanese Patent Laid-Open No. 06-242316 JP-A-62-183431 Japanese Patent Laid-Open No. 08-338913 JP 2002-062427 A

  The present invention is an optical film having excellent quality with few defects such as minute misalignment and scratches on the birefringent layer formed on the alignment film rubbed by using an alignment film material with a reduced amount of impurities, scratches, and discharge traces. It is another object of the present invention to provide a manufacturing method thereof.

  The first of the present invention is an optical film comprising a step of forming an alignment film on a substrate, a step of rubbing the formed alignment film, and then a step of forming a birefringent layer on the alignment film subjected to the rubbing treatment. The method for producing an optical film, wherein an amount of ionic impurities of the alignment film is 2000 ppm by mass or less.

  2nd of this invention is a manufacturing method of the optical film as described in 1st of this invention characterized by the said ionic impurity being sodium ion.

  A third aspect of the present invention is the method for producing an optical film according to the second aspect of the present invention, wherein the sodium ion is derived from sodium acetate.

  A fourth aspect of the present invention is the method for producing an optical film according to the first aspect of the present invention, wherein the alignment film is polyvinyl alcohol.

  5th of this invention is a manufacturing method of the optical film as described in 4th of this invention that the saponification degree of the said polyvinyl alcohol is 98% or more.

  A sixth aspect of the present invention is the method for producing an optical film according to the first aspect of the present invention, wherein the substrate is a plastic film.

  A seventh aspect of the present invention is the method for producing an optical film according to the first aspect of the present invention, wherein the birefringent layer is formed of a material containing a liquid crystal compound.

  An eighth aspect of the present invention is an optical film manufactured by the manufacturing method according to any one of the first to seventh aspects of the present invention.

  A ninth aspect of the present invention is a liquid crystal display element using the optical film according to the eighth aspect of the present invention.

  According to the present invention, it is possible to suppress defects caused by the alignment film, which is the cause of alignment defects and scratches in the birefringent layer formed on the rubbed alignment film, so that the obtained optical film has alignment defects, scratches, There are few defects such as film thickness anomalies, and a product having optically excellent quality can be obtained.

Hereinafter, the alignment film used in the present invention will be described.
The alignment film is given a function of aligning liquid crystal molecules in one direction with a certain angle with respect to the substrate surface (orientation ability) by receiving a rubbing treatment. Liquid crystal alignment includes vertical (homeotropic) alignment when the angle at which liquid crystal molecules are aligned with respect to the alignment film surface is constant and substantially perpendicular to the substrate surface, and parallel (homogeneous) alignment when approximately parallel to the substrate surface. In addition, inclined orientation, hybrid orientation, and the like can be produced by selecting conditions.

  As the base material to be the alignment film substrate, films such as polyimide, polyphenylene sulfide, polyphenylene oxide, polyether ether ketone, polyether sulfone, polyethylene naphthalate, polyethylene terephthalate, polyarylate, triacetyl cellulose, poly (cycloolefin), etc. It can be illustrated.

Examples of the material constituting the alignment film include inorganic compounds and organic compounds. Inorganic compounds include oxides such as silicon oxide (SiO) and titanium oxide (TiO), and organic compounds include various organic silane compounds, carboxylic acid chromium complex compounds, polyimide compounds, chalcone compounds, polyetherimide compounds, polyamides. Compounds, polyvinyl alcohol and derivatives thereof, and fluorinated hydrocarbon compounds.
Among these, polyvinyl alcohol (PVA) and a derivative thereof that form an alignment film having a high alignment ability at a processing temperature as low as 180 ° C. or less are preferably used. There are many commercial products (grades) of PVA. However, when the degree of polymerization, the degree of saponification, the amount of impurities, etc. were examined in detail, the effects on the alignment of liquid crystals differed, and the degree of saponification and the amount of ionic impurities were particularly important. It turns out that it has a big influence.
Impurities present in the alignment film material vary depending on the manufacturing process, but in the case of PVA, it has been found that the residual amount of sodium ions particularly affects the alignment of the liquid crystal.

The amount of ionic impurities in the alignment film material of the present invention is 2000 ppm by mass or less, preferably 1000 ppm by mass or less, more preferably 500 ppm by mass or less. If the ionic impurities exceed 2000 ppm by mass, it is not preferable because defects such as defects that are difficult to visually confirm and observed due to a microscope during the process and an increase in discharge phenomenon due to charging during the process occur.
When PVA is used as the alignment film, the degree of saponification is 98% or more, preferably 99.5% or more, and more preferably 99.9% or more. When the degree of saponification of PVA is less than 98%, the abrasion resistance is poor in the rubbing treatment process, and the scraping of the PVA film is likely to occur, which contaminates the optical film manufacturing process.

An alignment film forming process will be described.
For the formation of the alignment film, a method in which the material for forming the alignment film is applied in a solution state is preferable in terms of controlling the alignment film thickness and surface properties. The solution can be appropriately performed using a solvent capable of dissolving the material. For example, the solvent for preparing the PVA solution is not particularly limited as long as it is a solvent capable of dissolving the PVA, and water, lower alcohols such as methanol, ethanol, isopropyl alcohol, and mixtures thereof are usually used.
In addition, various additives that do not adversely affect the coating and the alignment of the liquid crystal may be added upon dissolution. Moreover, you may heat in order to accelerate | stimulate melt | dissolution.

The coating method used to form the alignment film on the substrate is not particularly limited, and the coating method for the large-area alignment film is in particular a flexographic printing method using a soft resin plate, a dispenser method, a gravure coating method, a micro coating method. A gravure method, a screen printing method, a lip coating method, a die coating method, and the like can be given. Among these, a gravure coating method, a lip coating method and a die coating method are preferable.
The applied alignment film is dried if necessary. The drying temperature is usually limited by the heat resistance of PVA, but may be higher depending on the purpose. Generally, it is 90 to 180 ° C, preferably 100 to 160 ° C. The drying time is not particularly limited, but is usually 10 seconds to 60 minutes, preferably 1 minute to 30 minutes. The relative moving speed between the film to be dried and the drying apparatus is preferably 60 m / min to 1200 m / min in terms of relative wind speed.

Next, the alignment film is rubbed. Hereinafter, the rubbing process will be described.
In the rubbing treatment, rubbing is performed at a predetermined arbitrary angle with respect to the long direction (hereinafter referred to as 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, referring to FIG. 1 as one of the methods, the long film (12) as an alignment substrate is placed on the stage (11) for conveying the MD to the MD at an arbitrary angle with respect to the long film (12) and the MD. A rubbing roll (10) is disposed, and the rubbing roll (10) is rotated while conveying the long film (12), so that 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.
A rubbing cloth manufactured using fibers made of cotton, polyester, rayon or the like is attached to the surface of the rubbing roll.

  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 in contact, and the pushing-in degree of the bristles of the rubbing cloth may be about 100 μm to 5000 μm, preferably about 100 μm to 2000 μm. 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.

Next, the birefringent layer will be described.
In the present invention, the material for forming the birefringent layer is preferably a material containing a liquid crystalline compound (liquid crystalline composition), and the composition only needs to exhibit liquid crystallinity, and the individual components constituting the liquid crystalline composition are total. It is not necessary to show liquid crystal properties.
As a component constituting the liquid crystalline composition, a low molecular liquid crystalline compound or a high molecular liquid crystalline compound is used regardless of the presence or absence of a reactive group, preferably a high molecular liquid crystalline compound, more preferably It is a polymer liquid crystalline compound having a reactive group.
The liquid crystal molecules may be rod-shaped or disk-shaped, but rod-shaped liquid crystal molecules are preferred.
In addition, other non-liquid crystalline polymer compounds that are miscible with the low-molecular liquid crystalline compounds and high-molecular liquid crystalline compounds, various activators and various additives such as surfactants, leveling agents, antifoaming agents, Antioxidants, dyes, pigments and the like can be added without departing from the scope of the present invention.

Examples of the low-molecular liquid crystalline compound include low-molecular liquid crystalline compounds having a polymerizable group such as a vinyl group, a (meth) acryloyl group, an oxiranyl group, and an oxetanyl group.
The polymer liquid crystalline compounds are roughly classified into main chain types and side chain types.
Examples of the main chain type polymer liquid crystalline compound include polyesters, polyester amides, polyamides, polycarbonates, etc., which exhibit liquid crystallinity, among others, from the viewpoint of ease of synthesis, orientation, glass transition point, etc. Liquid crystalline polyester is preferable, and main chain type liquid crystalline polyester having a cationic polymerizable group bonded thereto is particularly preferable.

The main chain type liquid crystalline polyester includes an aromatic diol unit (hereinafter referred to as a structural unit (A)), an aromatic dicarboxylic acid unit (hereinafter referred to as a structural unit (B)) and an aromatic hydroxycarboxylic acid unit (hereinafter referred to as a structural unit (B)). A main-chain liquid crystalline polyester containing at least two of the structural units (C) as essential units, and including a structural unit having a cationically polymerizable group at least at one end of the main chain. Main chain type liquid crystalline polyester.
Hereinafter, the structural units (A), (B), and (C) will be sequentially described.

  The compound for introducing the structural unit (A) is preferably a compound represented by the following general formula (a), specifically, catechol, resorcin, hydroquinone or the like or a substituted product thereof, 4,4′-biphenol 2,2 ′, 6,6′-tetramethyl-4,4′-biphenol, 2,6-naphthalenediol, and the like, and in particular, catechol, resorcin, hydroquinone, and the like, or substituted products thereof are preferable.

However, -X in the _{formula, -H, -CH 3, -C 2} H 5, -CH 2 CH 2 CH 3, -CH (CH 3) 2, -CH 2 CH 2 CH 2 CH 3, -CH _{2 CH (CH 3) CH 3} , -CH (CH 3) CH 2 CH 3, -C (CH 3) 3, -OCH 3, -OC 2 H 5, -OC 6 H 5, -OCH 2 C 6 H ₅ , —F, —Cl, —Br, —NO ₂ , or —CN, particularly preferably a compound represented by the following formula (a ′).

  As the compound for introducing the structural unit (B), a compound represented by the following general formula (b) is preferable. Specifically, terephthalic acid, isophthalic acid, phthalic acid or the like or a substituted product thereof, 4, 4 Examples include '-stilbene dicarboxylic acid or a substituted product thereof, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and the like, and terephthalic acid, isophthalic acid, phthalic acid, and the like or substituted products thereof are particularly preferable.

However, -X in the _{formula, -H, -CH 3, -C 2} H 5, -CH 2 CH 2 CH 3, -CH (CH 3) 2, -CH 2 CH 2 CH 2 CH 3, -CH _{2 CH (CH 3) CH 3} , -CH (CH 3) CH 2 CH 3, -C (CH 3) 3, -OCH 3, -OC 2 H 5, -OC 6 H 5, -OCH 2 C 6 H ₅ , -F, -Cl, -Br, -NO ₂ , or -CN.

  As the compound for introducing the structural unit (C), a compound represented by the following general formula (c) is preferable, and specifically, hydroxybenzoic acid or a substituted product thereof, 4′-hydroxy-4-biphenylcarboxylic acid Or a substituted product thereof, 4′-hydroxy-4-stilbenecarboxylic acid or a substituted product thereof, 6-hydroxy-2-naphthoic acid, 4-hydroxycinnamic acid, and the like. Particularly, hydroxybenzoic acid and a substituted product thereof, 4 '-Hydroxy-4-biphenylcarboxylic acid or a substituted product thereof, 4'-hydroxy-4-stilbenecarboxylic acid or a substituted product thereof is preferred.

However, -X in the formula, -X _1, -X ₂ are each _{individually, -H, -CH 3, -C 2} H 5, -CH 2 CH 2 CH 3, -CH (CH 3) 2, _{-CH 2 CH 2 CH 2 CH 3} , -CH 2 CH (CH 3) CH 3, -CH (CH 3) CH 2 CH 3, -C (CH 3) 3, -OCH 3, -OC 2 H 5, -OC ₆ H _5, represents _{-OCH 2 C 6 H 5, -F} , -Cl, -Br, any group of -NO _2, or -CN,.

  The main-chain liquid crystalline polyester has, as structural units, at least two of (A) aromatic diol units, (B) aromatic dicarboxylic acid units, and (C) aromatic hydroxycarboxylic acid units, preferably further Any structural unit may be used as long as it includes a structural unit having a cationically polymerizable group (hereinafter referred to as structural unit (D)) at least at one end of the main chain and exhibits thermotropic liquid crystallinity. Other structural units satisfy these conditions. As long as it does, it is not specifically limited.

  The proportion of the structural units (A), (B) and (C) constituting the main chain type liquid crystalline polyester in the total structural units is such that the structural units (A), (B) and (C) are diols or dicarboxylic acids or When expressed as a ratio of the sum of the weights of all the monomers as the hydroxycarboxylic acid, it is usually 20 to 99%, preferably 30 to 95%, particularly preferably 40 to 90%. If the amount is less than 20%, the temperature range in which the liquid crystallinity is exhibited may be extremely narrow. If the amount exceeds 99%, the number of units having a cationic polymerizable group is relatively small, and the orientation retention ability is reduced. The mechanical strength may not be improved.

  Next, the structural unit (D) having a cationic polymerizable group will be described. As the cationic polymerizable group, a functional group selected from the group consisting of an epoxy group, an oxetanyl group, and a vinyloxy group is preferable, and an oxetanyl group is particularly preferable. The compound for introducing the structural unit (D) is selected from an epoxy group, an oxetanyl group, and a vinyloxy group as an aromatic compound having a phenolic hydroxyl group or a carboxyl group, as shown in the following general formula (d). It is a compound to which a functional group having cationic polymerizability is bonded. Moreover, you may have a suitable spacer part between an aromatic ring and the said cation polymeric group.

However, -X in the formula, -X _1, -X _2, -Y, -Z represents any of the following groups each independently for each structural unit.
_{(1) -X, -X 1,} -X 2: -H, -CH 3, -C 2 H 5, -CH 2 CH 2 CH 3, -CH (CH 3) 2, -CH 2 CH 2 CH 2 _{CH 3, -CH 2 CH (CH} 3) CH 3, -CH (CH 3) CH 2 CH 3, -C (CH 3) 3, -OCH 3, -OC 2 H 5, -OC 6 H 5, - _{OCH 2 C 6 H 5, -F} , -Cl, -Br, -NO 2 or -CN,
(2) -Y: single _{bond, - (CH 2) n -} , - O -, - O- (CH 2) n -, - (CH 2) n -O -, - O- (CH 2) n - O -, - O-CO - , - CO-O -, - O-CO- (CH 2) n -, - CO-O- (CH 2) n -, - (CH 2) n -O-CO- , — (CH ₂ ) _n —CO—O—, —O— (CH ₂ ) _n —O—CO—, —O— (CH ₂ ) _n —CO—O—, —O—CO— (CH ₂ ) _{n -O -, - CO-O-} (CH 2) n -O -, - O-CO- (CH 2) n -O-CO -, - O-CO- (CH 2) n -CO-O- _{, -CO-O- (CH 2)} n -O-CO- or _{-CO-O- (CH 2) n} -CO-O-, ( where, n is an integer of 1-12.)
(3) Z:

  In the structural unit (D), the bonding position of the cationic polymerizable group or the substituent containing the cationic polymerizable group and the phenolic hydroxyl group or carboxylic acid group is 1 when the skeleton to which these groups are bonded is a benzene ring. From the viewpoint of liquid crystallinity, the 4-positional position is preferably a 2,6-positional position in the case of a naphthalene ring, and a 4,4′-positional position in the case of a biphenyl skeleton or a stilbene skeleton. More specifically, 4-vinyloxybenzoic acid, 4-vinyloxyphenol, 4-vinyloxyethoxybenzoic acid, 4-vinyloxyethoxyphenol, 4-glycidyloxybenzoic acid, 4-glycidyloxyphenol, 4- (oxetanyl) Methoxy) benzoic acid, 4- (oxetanylmethoxy) phenol, 4′-vinyloxy-4-biphenylcarboxylic acid, 4′-vinyloxy-4-hydroxybiphenyl, 4′-vinyloxyethoxy-4-biphenylcarboxylic acid, 4′- Vinyloxyethoxy-4-hydroxybiphenyl, 4′-glycidyloxy-4-biphenylcarboxylic acid, 4′-glycidyloxy-4-hydroxybiphenyl, 4′-oxetanylmethoxy-4-biphenylcarboxylic acid, 4′-oxetanylmethoxy- 4-hydroxybi Enyl, 6-vinyloxy-2-naphthalenecarboxylic acid, 6-vinyloxy-2-hydroxynaphthalene, 6-vinyloxyethoxy-2-naphthalenecarboxylic acid, 6-vinyloxyethoxy-2-hydroxynaphthalene, 6-glycidyloxy-2 -Naphthalenecarboxylic acid, 6-glycidyloxy-2-hydroxynaphthalene, 6-oxetanylmethoxy-2-naphthalenecarboxylic acid, 6-oxetanylmethoxy-2-hydroxynaphthalene, 4-vinyloxycinnamic acid, 4-vinyloxyethoxycinnamic acid, 4-glycidyloxycinnamic acid, 4-oxetanylmethoxycinnamic acid, 4'-vinyloxy-4-stilbenecarboxylic acid, 4'-vinyloxy-3'-methoxy-4-stilbenecarboxylic acid, 4'-vinyloxy-4-hydroxystilbene 4 '-Vinyloxyethoxy-4-stilbenecarboxylic acid, 4'-vinyloxyethoxy-3'-methoxy-4-stilbenecarboxylic acid, 4'-vinyloxyethoxy-4-hydroxystilbene, 4'-glycidyloxy-4- Stilbenecarboxylic acid, 4′-glycidyloxy-3′-methoxy-4-stilbenecarboxylic acid, 4′-glycidyloxy-4-hydroxystilbene, 4′-oxetanylmethoxy-4-stilbenecarboxylic acid, 4′-oxetanylmethoxy- 3′-methoxy-4-stilbene carboxylic acid, 4′-oxetanylmethoxy-4-hydroxystilbene and the like are preferable.

  The ratio of the structural unit (D) having a cationic polymerizable group to the total structural units constituting the main-chain liquid crystalline polyester is similarly expressed by the weight ratio in the composition charged with the structural unit (D) as carboxylic acid or phenol. When used, it is usually 1 to 60%, preferably 5 to 50%. If it is less than 1%, there is a possibility that the improvement of the orientation holding ability and the mechanical strength may not be obtained. If it exceeds 60%, the crystallinity is increased and the liquid crystal temperature range is narrowed. Is also not preferable.

Each structural unit of (A) to (D) has one or two carboxyl groups or phenolic hydroxyl groups, but the carboxyl groups and phenolic hydroxyl groups of (A) to (D) are charged. In this step, it is desirable to make the sum of the number of equivalents of each functional group substantially equal. That is, when the structural unit (D) is a unit having a free carboxyl group,
When the number of moles of (A) × 2 = number of moles of (B) × 2 + number of moles of (D) structural unit (D) is a unit having a free phenolic hydroxyl group,
Number of moles of (A) × 2 + Number of moles of (D) = Number of moles of (B) × 2
It is desirable to satisfy the general relationship. In the case of a charged composition greatly deviating from this relational expression, carboxylic acid or phenol other than the unit involved in cationic polymerization, or a derivative thereof becomes the molecular end, and not only sufficient cationic polymerizability cannot be obtained, The presence of these acidic residues is not preferable because a polymerization reaction or a decomposition reaction may occur at a stage other than the desired stage in the process.

  The main chain type liquid crystalline polyester can contain structural units other than (A), (B), (C) and (D). Other structural units that can be contained are not particularly limited, and compounds (monomers) known in the art can be used. For example, naphthalene dicarboxylic acid, biphenyl dicarboxylic acid, aliphatic dicarboxylic acid, compounds in which halogen groups or alkyl groups are introduced into these compounds, biphenols, naphthalenediol, aliphatic diols, and compounds in which halogen groups or alkyl groups are introduced into these compounds Etc.

Further, when an optically active compound is used as a raw material for the units constituting the main chain type liquid crystalline polyester, it is possible to impart a chiral phase to the main chain type liquid crystalline polyester. The optically active compound is not particularly limited. For example, an optically active aliphatic alcohol (C _n H _{2n + 1} OH, where n represents an integer of 4 to 14), an optically active aliphatic group is bonded. alkoxy benzoate _{(C n H 2n + 1 O} -Ph-COOH, where n is 4 to 14 integer, Ph represents a phenylene group.), menthol, camphor acid, naproxen derivatives, binaphthol, 1,2-propanediol, 1 , 3-butanediol, 2-methylbutanediol, 2-chlorobutanediol, tartaric acid, methylsuccinic acid, 3-methyladipic acid and the like.

  The molecular weight of the main-chain liquid crystalline polyester is preferably 0.03 to 0.50 dl / g in logarithmic viscosity η measured at 30 ° C. in a phenol / tetrachloroethane mixed solvent (mass ratio 60/40). Is 0.05 to 0.15 dl / g. When η is smaller than 0.03 dl / g, the solution viscosity of the main-chain liquid crystalline polyester is low, and there is a possibility that a uniform coating film cannot be obtained when forming into a film. On the other hand, if it is larger than 0.50 dl / g, the alignment treatment temperature required for aligning the liquid crystal becomes high, and there is a risk that the alignment and the crosslinking occur simultaneously to deteriorate the alignment.

  In the present invention, the molecular weight control of the main chain type liquid crystalline polyester is determined solely by the charged composition. Specifically, the main chain obtained by the relative content in the total charge composition of the monofunctional monomer that reacts in such a manner that both ends of the molecule are sealed, that is, the compound for introducing the structural unit (D) described above. The average degree of polymerization of the liquid crystal polyester (average number of bonds of the structural units (A) to (D)) is determined. Therefore, in order to obtain a main-chain liquid crystalline polyester having a desired logarithmic viscosity, it is necessary to adjust the charged composition according to the type of charged monomer.

  As a method for synthesizing the main-chain liquid crystalline polyester, a method used when synthesizing a normal polyester can be adopted, and the method is not particularly limited. For example, a method in which a carboxylic acid unit is activated to an acid chloride or a sulfonic acid anhydride and reacted with a phenol unit in the presence of a base (acid chloride method), a carboxylic acid unit and a phenol unit are converted into DCC (dicyclohexylcarbodiimide), etc. A method of directly condensing using a condensing agent of the above, a method of acetylating a phenol unit, and deaceticating polymerization of this with a carboxylic acid unit under melting conditions can be used. However, in the case of using deacetic acid polymerization under melting conditions, it is necessary to strictly control the reaction conditions because the monomer unit having a cationic polymerizable group may cause polymerization or decomposition reaction under the reaction conditions. In many cases, it is desirable to use a method such as using an appropriate protective group or reacting a compound having another functional group once and then introducing a cationically polymerizable group later. There is also. The crude main chain type liquid crystalline polyester obtained by the polymerization reaction may be purified by a method such as recrystallization or reprecipitation.

  The main-chain liquid crystalline polyester thus obtained is identified by the analytical means such as NMR (nuclear magnetic resonance method) at what ratio each monomer is present in the main-chain liquid crystalline polyester. can do. In particular, the average number of bonds of the main-chain liquid crystalline polyester can be calculated from the amount ratio of the cationic polymerizable group.

  It is also possible to mix other compounds with the main-chain liquid crystalline polyester containing the cationic polymerizable group as long as the scope of the present invention is not exceeded. For example, you may add the other high molecular compound miscible with the main chain type liquid crystalline polyester used for this invention, various low molecular weight compounds, etc. Such low molecular weight compounds may or may not have liquid crystallinity, and may or may not have a polymerizable group capable of reacting with a crosslinkable main chain liquid crystalline polyester. It is preferable to use a liquid crystalline compound having a polymerizable group, and examples thereof include the following.

Here, n represents an integer of 2 to 12, and -V- and -W each represents one of the following groups.
-V-: single bond, -O -, - O-C m H 2m -O- ( although, m is an integer from 2 to 12)
-W:

  In addition, when the high molecular compound and low molecular compound to add are optically active, a chiral liquid crystal phase can be induced as a composition. Such a composition can be used for production of a film having a twisted nematic alignment structure or a cholesteric alignment structure.

  Examples of the side chain polymer liquid crystalline compound include poly (meth) acrylate, polymalonate, polysiloxane, and the like. Among them, poly (meth) acrylate bonded with a reactive group represented by the following general formula (1) Is preferred.

In Formula (1), each R ³ independently represents hydrogen or a methyl group, and each R ⁴ independently represents hydrogen, methyl group, ethyl group, butyl group, hexyl group, octyl group, nonyl group, decyl group. Group, dodecyl group, methoxy group, ethoxy group, propoxy group, butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group, decyloxy group, dodecyloxy group, cyano group, bromo group, chloro group, fluoro R ⁵ represents a hydrogen group, a methyl group or an ethyl group, R ⁶ represents a hydrocarbon group having 1 to 24 carbon atoms, and L ² each independently represents a group or a carboxyl group. Represents a single bond, —O—, —O—CO—, —CO—O—, —CH═CH— or —C≡C—, p represents an integer of 1 to 10, and q represents Represents an integer of 10 from, a, b, c, d, e and f represent the mole ratio of each unit in the polymer (a + b + c + d + e + f = 1.0, but not the c + d + e = 0).

The molar ratio of each component constituting the side chain type polymer liquid crystalline compound represented by the formula (1) is not a + b + c + d + e + f = 1.0, c + d + e = 0, and needs to exhibit liquid crystallinity. The molar ratio of each component may be arbitrary as long as this requirement is satisfied, but is preferably as follows.
a: Preferably 0 to 0.80, more preferably 0.05 to 0.50
b: preferably 0 to 0.90, more preferably 0.10 to 0.70
c: preferably 0 to 0.50, more preferably 0.10 to 0.30
d: preferably 0 to 0.50, more preferably 0.10 to 0.30
e: preferably 0 to 0.50, more preferably 0.10 to 0.30
f: Preferably 0 to 0.30, more preferably 0.01 to 0.10

Each component in these poly (meth) acrylates does not need to be present in all six types as long as the above conditions are satisfied.
R ⁴ is preferably hydrogen, methyl group, butyl group, methoxy group, cyano group, bromo group or fluoro group, particularly preferably hydrogen, methoxy group or cyano group, and L ² is preferably Is a single bond, —O—, —O—CO— or —CO—O—, and R ⁶ preferably represents a hydrocarbon group having 2, 3, 4, ⁶ , 8 or 18 carbon atoms.
Furthermore, the birefringence of the side chain type polymer liquid crystalline compound represented by the general formula (1) varies depending on the molar ratio of each component a to f and the orientation form, but the birefringence when nematic orientation is taken. The rate is preferably 0.001 to 0.300, more preferably 0.05 to 0.25.

  Each (meth) acrylic compound corresponding to each component of the above-mentioned side chain polymer liquid crystalline compound can be obtained by an ordinary organic chemical synthesis method. The (meth) acrylic compound having an oxetanyl group can be easily obtained by a method similar to the synthesis of compounds corresponding to formulas (7), (8) and (9) described later.

  Said side chain type polymer liquid crystalline compound can be easily obtained by copolymerizing the (meth) acrylic group of each (meth) acrylic compound obtained by the above method corresponding to each component by radical polymerization or anionic polymerization. Can be synthesized. Polymerization conditions are not particularly limited, and normal conditions can be employed.

  As an example of radical polymerization, a (meth) acrylic compound corresponding to each component is dissolved in a solvent such as dimethylformamide (DMF) or diethylene glycol dimethyl ether, and 2,2′-azobisisobutyronitrile (AIBN) or benzoyl peroxide is dissolved. The method of making it react for several hours at 60-120 degreeC by using (BPO) etc. as an initiator is mentioned. Moreover, in order to make the liquid crystal phase appear stably, copper bromide (I) / 2,2′-bipyridyl series, 2,2,6,6-tetramethylpiperidinooxy free radical (TEMPO) series, etc. are used. A method of controlling the molecular weight distribution by conducting living radical polymerization as an initiator is also effective. These radical polymerizations need to be performed under deoxygenated conditions.

  An example of anionic polymerization is a method in which a (meth) acrylic compound corresponding to each component is dissolved in a solvent such as tetrahydrofuran (THF) and reacted with a strong base such as an organic lithium compound, an organic sodium compound, or a Grignard reagent as an initiator. Can be mentioned. In addition, the molecular weight distribution can be controlled by optimizing the initiator and the reaction temperature for living anionic polymerization. These anionic polymerizations need to be performed under dehydration and deoxygenation conditions.

  The side chain polymer liquid crystalline compound preferably has a weight average molecular weight of 1,000 to 200,000, particularly preferably 3,000 to 50,000. Outside this range, the strength is insufficient or the orientation is deteriorated.

  In addition, the above-mentioned discotic liquid crystal molecules, that is, discotic liquid crystal molecules, are disclosed in various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); Chapter, Quarterly Chemistry Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10, Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 ( 1985); J. Zhang et al., J. Am. Chem. Soc., Vol. 116, page 2655 (1994)). The polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284.

In the present invention, the liquid crystalline composition preferably contains a dioxetane compound represented by the following general formula (2).

In the formula (2), each R ⁷ independently represents hydrogen, a methyl group or an ethyl group, and each L ³ independently represents a single bond or — (CH ₂ ) _n — (n is an integer of 1 to 12) X ¹ represents each independently a single bond, —O—, —O—CO— or —CO—O—, and M ¹ is represented by formula (3) or formula (4). P ¹ in formulas (3) and (4) each independently represents a group selected from formula (5), P ² represents a group selected from formula (6), and L ⁴ Each independently represents a single bond, —CH═CH—, —C≡C—, —O—, —O—CO— or —CO—O—.
-P ¹ -L ⁴ -P ² -L ⁴ -P ^1- (3)
-P ¹ -L ⁴ -P ^1- (4)

In the formulas (5) and (6), Et represents an ethyl group, iPr represents an isopropyl group, nBu represents a normal butyl group, and tBu represents a tertiary butyl group.
More specifically, the linking groups connecting the left and right oxetanyl groups as viewed from the M ¹ group may be different (asymmetric) or the same (symmetric), particularly when two L ³ are different or other Depending on the structure of the linking group, it may not exhibit liquid crystallinity, but it is not a restriction for use.
The compound represented by the general formula (2) can be exemplified by many compounds from the combination of M ¹ , L ³ and X ¹ , and preferably the following compounds can be mentioned.

These compounds can be synthesized according to a usual synthesis method in organic chemistry, and the synthesis method is not particularly limited.
In the synthesis, since the oxetanyl group has cationic polymerizability, it is necessary to select reaction conditions in consideration of causing side reactions such as polymerization and ring opening under strong acidic conditions. The oxetanyl group is less likely to cause a side reaction than an oxiranyl group that is a similar cationically polymerizable functional group. Furthermore, various compounds such as similar alcohols, phenols, carboxylic acids and the like may be reacted one after another, and utilization of protecting groups may be considered as appropriate.

  As a more specific synthesis method, for example, hydroxybenzoic acid is used as a starting compound, an oxetanyl group is bound by Williamson's ether synthesis method, etc., and then the resulting compound and a diol suitable for the present invention are combined with an acid chloride. Or by condensing using a carbodiimide condensation method or the like, or conversely protecting the hydroxyl group of hydroxybenzoic acid with an appropriate protecting group in advance, condensing with a diol suitable for the present invention, removing the protecting group, and Examples thereof include a method of reacting a hydroxyl group with a compound having an oxetanyl group (oxetane compound), for example, a haloalkyloxetane or the like.

  For the reaction between the oxetane compound and the hydroxyl group, a reaction condition suitable for the form and reactivity of the compound used may be selected. Usually, the reaction temperature is -20 ° C to 180 ° C, preferably 10 ° C to 150 ° C. The reaction time is 10 minutes to 48 hours, preferably 30 minutes to 24 hours. Outside these ranges, the reaction does not proceed sufficiently or side reactions occur, which is not preferable. Moreover, the mixing ratio of both is preferably 0.8 to 1.2 equivalents of the oxetane compound per equivalent of hydroxyl group.

  The reaction can be carried out without solvent, but is usually carried out in a suitable solvent. The solvent used is not particularly limited as long as it does not interfere with the intended reaction. For example, aromatic hydrocarbons such as benzene, toluene and xylene, amides such as dimethylformamide, dimethylacetamide and N-methylpyrrolidone, methyl ethyl ketone, Examples include ketones such as methyl isobutyl ketone, ethers such as dibutyl ether, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, esters such as ethyl acetate and ethyl benzoate, halogenated hydrocarbons such as chloroform and dichloromethane, and mixtures thereof. .

  The liquid crystalline composition used in the present invention contains at least 10% by mass, preferably 30% by mass or more, more preferably 50% by mass or more of the low molecular liquid crystalline compound or the high molecular liquid crystalline compound, and has liquid crystallinity. It is the composition shown. When the content of the low-molecular liquid crystalline compound or the high-molecular liquid crystalline compound is less than 10% by mass, the concentration of the compound exhibiting liquid crystallinity in the composition is low, and the composition may not exhibit liquid crystallinity. Absent.

As described above, the liquid crystalline composition of the present invention may contain various compounds that can be mixed without impairing liquid crystallinity, in addition to the low molecular liquid crystalline compound or the high molecular liquid crystalline compound. Examples of the compound that can be contained include various polymerizable compounds having a radical polymerizable group such as a vinyl group and a (meth) acryloyl group and a cationic polymerizable group such as an oxetanyl group, an epoxy group, and a vinyl ether group, a carboxyl group, and an amino group. A compound having a reactive group such as a group or an isocyanate group, or various polymer compounds having film-forming ability can also be blended. In addition, if a surfactant, antifoaming agent, leveling agent, etc., as well as a compound having a reactive functional group or a low molecular or high molecular liquid crystal is used as described above, a reaction start suitable for each functional group is started. You may add an agent, an activator, a sensitizer, etc. within the range which does not deviate from the objective of this invention.
A liquid crystalline composition having a reactive group is obtained by achieving a desired alignment and then reacting under a condition suitable for reacting the reactive group to achieve a desired final product by crosslinking or increasing molecular weight. It is also possible to contribute to the improvement of the mechanical strength and the like.

  As said polymeric compound, the compound which can improve the workability and adhesiveness in the next processing process of the liquid crystal film obtained by a case is preferable, and the (meth) acrylates which have an oxetanyl group are especially preferable. Examples of these (meth) acrylates include compounds represented by general formulas (7), (8) and (9).

In the above formula (7), formula (8) and formula (9), each R ¹ independently represents hydrogen or a methyl group, each R ² independently represents hydrogen, a methyl group or an ethyl group, L ¹ each independently represents a single bond, —O—, —O—CO— or —CO—O—, m is each independently an integer of 1 to 10, and n is each independently Represents an integer from 0 to 10.

Various specific compounds corresponding to these formulas (7), (8) and (9) can be mentioned, but they do not necessarily have liquid crystallinity. More specifically,
Etc. are particularly preferred.

The method for synthesizing these (meth) acrylates having an oxetanyl group is not particularly limited, and can be synthesized by applying a method used in ordinary organic chemistry synthesis methods.
For example, by combining a site with an oxetanyl group and a site with a (meth) acryloyl group by means such as Williamson's ether synthesis or ester synthesis using a condensing agent, the oxetanyl group and the (meth) acryloyl group are completely A (meth) acrylate having an oxetanyl group having two different reactive groups can be synthesized. However, in the reaction, since the oxetanyl group has cationic polymerizability, it is necessary to select reaction conditions in consideration of causing side reactions such as polymerization and ring opening under strong acidic conditions. May be appropriately selected from the range detailed in the synthesis of the compound represented by the above general formula (1).

Examples of the reaction initiator include organic peroxides used in general radical polymerization and various photopolymerization initiators.
Examples of the photopolymerization initiator include a photo radical initiator that cleaves with appropriate light to generate radicals, and a photo cation generator that cleaves with appropriate light to generate cations. If necessary, a thermal cation generator that can generate cations when heated to an appropriate temperature can also be used.
Examples of the photoradical initiator include commercially available benzoin ethers, acylphosphine oxides, triazine derivatives, and imidazole derivatives used for general ultraviolet (UV) curable paints, UV adhesives, negative resists, and the like. .
Examples of the photocation generator include organic sulfonium salt systems, iodonium salt systems, and phosphonium salt systems. Antimonates, phosphates, borates and the like are preferably used as counter ions of these compounds. Specific examples of the compound include Ar ₃ S ⁺ SbF ₆ ⁻ , Ar ₃ P ⁺ BF ₄ ⁻ , Ar ₂ I ⁺ PF ₆ ⁻ (wherein Ar represents a phenyl group or a substituted phenyl group), and the like. In addition, sulfonate esters, triazines, diazomethanes, β-ketosulfone, iminosulfonate, benzoinsulfonate, and the like can also be used.
Examples of the thermal cation generator include benzylsulfonium salts, benzylammonium salts, benzylpyridinium salts, benzylphosphonium salts, hydrazinium salts, carboxylic acid esters, sulfonic acid esters, amine imides, antimony pentachloride-acetyl chloride complex , Diaryl iodonium salt-dibenzyloxy copper, boron halide-tertiary amine adduct, and the like.

  The amount of these reaction initiators added to the liquid crystal composition varies depending on the structure of the mesogen part and spacer part, the molecular weight, the alignment condition of the liquid crystal, etc. constituting the liquid crystal compound to be used. On the other hand, it is usually in the range of 100 mass ppm to 20 mass%, preferably 1000 mass ppm to 10 mass%, more preferably 0.5 mass% to 7 mass%. If the amount is less than 100 mass ppm, the amount of active species generated from the reaction initiator may not be sufficient and the reaction may not proceed. If the amount is more than 20 mass%, it remains in the liquid crystal composition. This is not preferable because there is a risk that the decomposition residue of the reaction initiator and the like increase in color and the light resistance and the like deteriorate.

Although the formation method of a liquid crystalline composition (birefringence) layer is demonstrated below, as a formation method of a liquid crystalline composition layer, it is not limited to these.
First, the liquid crystalline composition of the present invention is developed on an alignment film substrate.
As a method for forming a liquid crystalline composition layer by spreading the liquid crystalline composition on the alignment film substrate, a method in which the liquid crystalline composition is directly applied on the alignment substrate in a molten state, or a solution of the liquid crystalline composition is used. The method of drying a coating film and distilling a solvent after apply | coating on an orientation board | substrate is mentioned.
The solvent used for preparing the solution is not particularly limited as long as it is a solvent that can dissolve various compounds used in the liquid crystal composition of the present invention and can be distilled off under appropriate conditions. Generally, acetone, methyl ethyl ketone, isophorone, Ketones such as cyclohexanone, butoxyethyl alcohol, hexyloxyethyl alcohol, ether alcohols such as methoxy-2-propanol and benzyloxyethanol, glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, ethyl acetate, ethyl lactate, γ- Esters such as butyrolactone, phenols such as phenol and chlorophenol, amides such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone, chloro Lum, tetrachloroethane, halogenated such or a mixture of these systems, such as dichlorobenzene are preferably used. Moreover, in order to form a uniform coating film on the alignment substrate, a surfactant, an antifoaming agent, a leveling agent, or the like may be added to the solution.

  There is no particular limitation on the application method, either a method of directly applying a liquid crystalline composition or a method of applying a solution, as long as the uniformity of the coating film is ensured, and a known method is adopted. be able to. Examples thereof include a flexographic printing method, an offset printing method, a dispenser method, a gravure coating method, a micro gravure method, a screen printing method, a lip coating method, and a die coating method. Of these, gravure coating, kiss coating, lip coating and die coating are preferred.

  In the method of applying the liquid crystal composition solution, it is preferable to include a drying step for removing the solvent after the application. As long as the uniformity of a coating film is maintained, this drying process can employ | adopt a well-known method, without being specifically limited. For example, a method such as a heater (furnace) or hot air blowing may be used.

  The coating film thickness is not determined unconditionally because it is adjusted depending on the liquid crystal composition to be used and the application of the birefringent layer to be obtained, etc., but it is 0.1 to 20 μm, preferably 0.3 to 30 mm after drying. 10 μm. Alternatively, since the liquid crystalline composition exhibits refractive index anisotropy by being oriented, it is not always sufficient to simply define the coating film thickness only by the film thickness. Depending on the orientation state of the liquid crystal, the retardation value (= In some cases, it is preferable to define the refractive index anisotropy × film thickness: Δn × d). The retardation value at that time is 10 to 1000 nm, preferably 20 to 800 nm. If the film thickness and / or retardation value is outside this range, the desired effect is not observed, and the orientation is insufficient.

  Subsequently, after the liquid crystal composition (birefringence) layer formed on the alignment film substrate is aligned with a liquid crystal by a method such as heat treatment, a reactive group is reacted by light irradiation and / or heat treatment as necessary. The orientation is fixed. In the first heat treatment, the liquid crystal is aligned by the self-alignment ability inherent in the liquid crystalline composition by heating to a desired temperature within the liquid crystal phase expression temperature range of the used liquid crystalline composition. As the conditions for the heat treatment, the optimum conditions and limit values differ depending on the liquid crystal phase behavior temperature (transition temperature) of the liquid crystal composition to be used, but it cannot be generally stated, but is usually 10 to 300 ° C., preferably 20 to 250 ° C. It is preferable that the heat treatment be performed at a temperature not lower than the glass transition point (Tg) of the liquid crystalline composition, more preferably not lower than 10 ° C. higher than Tg. If the temperature is too low, the liquid crystal alignment may not proceed sufficiently, and if the temperature is high, the liquid crystal composition and the alignment substrate may be adversely affected. Moreover, about heat processing time, it is 3 seconds-30 minutes normally, Preferably it is the range of 10 seconds-10 minutes. If the heat treatment time is shorter than 3 seconds, the liquid crystal alignment may not be completed sufficiently, and if the heat treatment time exceeds 30 minutes, the productivity is deteriorated.

  After forming the alignment of the liquid crystalline composition layer by the above method, when a liquid crystalline composition containing a reactive group is used, the liquid crystalline composition is kept in the composition while maintaining the liquid crystal alignment state. The function of the reaction initiator contained is expressed and the reactive group is reacted to fix the orientation or improve the mechanical strength.

When the reaction initiator expresses the function of the initiator by light irradiation, the light irradiation method includes a metal halide lamp having a spectrum in the absorption wavelength region of the reaction initiator used, a high-pressure mercury lamp, a low-pressure mercury lamp, a xenon lamp, Irradiates light from a light source such as an arc lamp or laser to activate the reaction initiator. The dose per square centimeter is usually in the range of 1 to 2000 mJ, preferably 10 to 1000 mJ as the cumulative dose. However, this is not the case when the absorption region of the reaction initiator and the spectrum of the light source are significantly different, or when the liquid crystalline composition itself has the ability to absorb light of the light source wavelength. In these cases, an appropriate photosensitizer, or a mixture of two or more reaction initiators having different absorption wavelengths may be used.
The temperature during light irradiation is preferably in the temperature range in which the liquid crystalline composition takes liquid crystal alignment. In order to sufficiently enhance the reaction effect, light irradiation is performed at a liquid crystal phase temperature equal to or higher than Tg of the liquid crystal material. preferable.

  The liquid crystalline composition layer in which the liquid crystal alignment is fixed is in a form as it is formed on the alignment film substrate (alignment substrate / (alignment film) / liquid crystal composition layer), a transparent substrate different from the alignment film substrate Form (transparent substrate film / (adhesive / adhesive layer) / liquid crystalline composition layer) or liquid crystal transferred through various adhesives / adhesives that can optically use the liquid crystalline composition layer on a film or the like The composition can be used as an optical film in a single layer form (birefringent layer).

  As an alignment film substrate, it is not optically isotropic, or the resulting birefringent layer is finally opaque in the intended use wavelength region, or the film thickness of the alignment film substrate is too thick, which hinders actual use. When there is a problem such as occurring, a wavelength different from the alignment film substrate from the form formed on the alignment film substrate, for example, the optically isotropic or the obtained birefringent layer is finally intended wavelength A transparent film in the region, or a form transferred to a film for temporarily supporting until the film layer is bonded to a liquid crystal cell or the like can also be used. As a transfer method, a known method can be adopted. For example, as described in JP-A-4-57017 and JP-A-5-333313, a birefringent layer is required after laminating a substrate different from the alignment film substrate via an adhesive or an adhesive. A method of transferring only the birefringent layer by subjecting the pressure-sensitive adhesive or adhesive to curing treatment and peeling the alignment film substrate from the laminate can be exemplified.

  Examples of the substrate different from the alignment film substrate include, for example, triacetyl cellulose films such as Fujitac (product of Fuji Photo Film) and Konicatak (product of Konica Minolta Opto), TPX film (product of Mitsui Chemicals), Arton film ( JSR products), Zeonex film (Nippon ZEON products), acrylprene film (Mitsubishi Rayon products) and other transparent films, polyethylene terephthalate film with silicon treatment and easy release layer on the surface, etc. Can be mentioned. If necessary, the film can be directly transferred to a film, a polarizing element, a polarizing plate, various kinds of glass, or the like having a retardation function by stretching or the like.

  The pressure-sensitive adhesive or adhesive used for transfer is not particularly limited as long as it is of optical grade. For example, acrylic, epoxy resin, ethylene-vinyl acetate copolymer, rubber, urethane, and mixtures thereof And various reactive types such as a thermosetting type and / or a photo-curing type and an electron beam curable type. The reaction (curing) conditions for the reactive ones vary depending on the components constituting the adhesive / adhesive, the viscosity, the reaction temperature, and the like. Therefore, the conditions suitable for each may be selected. For example, in the case of the photo-curing type, the same light source may be used as in the case of the photocation generator described below, and the acceleration voltage in the case of the electron beam-curing type is usually 10 kV to 200 kV, preferably 50 kV to 100 kV.

The optical film of the present invention thus obtained has various uses depending on its orientation structure, and is particularly preferably used as a viewing angle improving film for liquid crystal display elements.
Although there is no restriction | limiting in particular as a liquid crystal display element, Various liquid crystal display elements of a transmissive type, a reflective type, and a semi-transmissive type can be mentioned. Examples of modes by liquid crystal alignment in a liquid crystal cell include TN type, STN type, VA (vertical alignment) type, MVA (multi-domain vertical alignment) type, OCB (optically compensated bend) type, ECB (electrically controlled biriefringence). Type, HAN (hybrid-aligned nematic) type, IPS (in-plane switching) type, and the like. With respect to the liquid crystal alignment, it may have a single directionality within the plane of the cell, or may be used for a liquid crystal display element or the like in which the alignment is divided. Further, in terms of a method of applying a voltage to the liquid crystal cell, for example, a liquid crystal display element driven by a passive method using an ITO electrode or the like, an active method using a TFT (thin film transistor) electrode, a TFD (thin film diode) electrode, or the like. be able to.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.
The following examples and comparative examples were performed in a clean room maintained at a cleanness of 1000 or less, a temperature of 23 ± 1 ° C., and a relative humidity of 45 ± 5%.
The analysis methods used in Examples and Comparative Examples are described below.

(1) Quantification of Na ⁺ amount in alignment film material (PVA) The amount of Na (mass ppm), which is an impurity in PVA, is measured by atomic absorption spectrometry after dissolving PVA powder in deionized water. Measured promptly.

(2) Measurement of molecular weight The compound was dissolved in tetrahydrofuran, and TS was used with Tosoh 8020GPC system.
K-GEL SuperH1000, SuperH2000, SuperH3000, S
Upper H4000 was connected in series and measured using tetrahydrofuran as the eluent. Polystyrene standards were used for molecular weight calibration.

(3) Measurement of PVA solution concentration PVA solution concentration was measured from the mass loss before and after drying at 107 ° C in air for 3 hours using an ETAC oven HT310S and weighed the PVA solution in an aluminum tray. Asked.

(4) Microscope observation The orientation state of the birefringent layer was observed with an Olympus BH2 polarizing microscope. In addition, a part was also observed visually.

(5) Parameter measurement of optical film KOBRA-21ADH manufactured by Oji Scientific Instruments Co., Ltd. was used.

[Reference Example 1] Preparation of PVA solution A stainless steel 500 L tank equipped with a reflux condenser and a stirrer was charged with PVA (Nippon Vinegar-Poval Co., Ltd., trade name AT, average saponification degree 99.94%, average Degree of polymerization 1700 (composition: powder composed of 53% PVA component, 47% moisture) 30.19 kg deionized water (electric conductivity value: 1 μS / cm or less) was added, heated at 95 ° C. for 3 hours and stirred After dissolution, the mixture was cooled to 70 ° C., 76.8 kg of isopropyl alcohol (manufactured by Kanto Chemical Co., Inc., deer grade 1, purity 99% or more) was gradually added, and the mixture was stirred at 65 ° C. to 70 ° C. for 2 hours.
It cooled to room temperature and extracted, filtering the PVA solution from the said tank. Filtration is performed using a cartridge filter (manufactured by ADVANTEC, TCP-JX-S1FE (1 μm)) capable of collecting particles having an average particle diameter of 1 μm, at a filtration rate of 20 kg / 2 minutes (35 to 30 ° C.). 350 kg of a solution having a concentration of about 4% by mass was obtained.
The amount of Na ⁺ in the PVA used was 120 mass ppm.

[Reference Example 2]
A PVA solution was prepared in the same manner as in Reference Example 1. The PVA used is a product name VC-20DH (average saponification degree 99.92%, average polymerization degree 2000) manufactured by Nippon Vinegar Poval Co., Ltd.
The amount of Na ⁺ in the PVA used was 340 mass ppm.

[Reference Example 3]
In the same manner as in Reference Example 1, a PVA solution was obtained using PVA117H (trade name, manufactured by Kuraray Co., Ltd., average degree of saponification 99.3%, average degree of polymerization 1700).
The amount of Na ⁺ in the PVA used was 2300 mass ppm.

[Reference Example 4]
In the same manner as in Reference Example 1, a PVA solution was obtained using PVA117 (trade name, manufactured by Kuraray Co., Ltd., average degree of saponification 98.0%, average degree of polymerization 1700).
The amount of Na ⁺ acetate in the PVA used was 3000 ppm by mass.

[Reference Example 5]
Sodium acetate was added to the PVA solution obtained in Reference Example 1 so that the Na ⁺ amount in the PVA was 3800 ppm by mass to obtain a PVA solution.

[Reference Example 6]
A liquid crystal composition solution used for production of an optical film was prepared as follows.
A liquid crystalline polymer represented by the following formula (8) was synthesized by ordinary radical polymerization. The molecular weight was, in terms of polystyrene, number average molecular weight (Mn) = 8000 and weight average molecular weight (Mw) = 15000.
After 200.0 g of this liquid crystalline polymer was dissolved in 1800 ml of cyclohexanone, 20 g of a triallylsulfonium hexafluoroantimonate 50% propylene carbonate solution (manufactured by Aldrich, reagent) was added in the dark, and then a pore diameter of 0.45 μm was added. A liquid crystal composition solution was prepared by filtration through a polytetrafluoroethylene filter.
In addition, although following formula (8) is displayed with the form of a block copolymer, it displays the monomer composition ratio (mol ratio) at the time of superposition | polymerization.

[Examples 1-2 and Comparative Examples 1-3]
(Alignment film formation)
Reference examples 1 to 5 having a dry film thickness of about 1 μm by a gravure coater on a polyethylene naphthalate film (PEN: manufactured by Teijin DuPont Films, trade name Q51 or Q02) having a width of 650 mm and a length of 1000 m at room temperature. Each PVA solution obtained in 1 was continuously applied. The coating film was continuously dried at a relative drying air speed of 600 m / min with a hot air circulation drier set at 50 ° C., 70 ° C., 90 ° C. and 130 ° C. to obtain a long film with an alignment film.

(Rubbing process)
With the apparatus shown in FIG. 1, a 150 mm diameter rubbing roll with a rubbing cloth wrapped around the alignment film surface is conveyed with respect to the MD of the film while conveying the long film with the alignment film obtained above at a speed of 20 m / min. The rubbing cloth was continuously rubbed by rotating at 1500 rpm (peripheral speed ratio 35) by setting the pushing of the bristles of the rubbing cloth to 500 μm (wind speed ratio 35).

(Manufacture of optical film)
The liquid crystalline composition solution obtained in Reference Example 6 was applied on the rubbing-treated long film using a roll coater so that the birefringent layer thickness after orientation / curing was 1 μm, and then at 60 ° C. And dried at 140 ° C. for 2 minutes to orient the liquid crystalline composition layer, and then an ultraviolet ray irradiation apparatus equipped with a high-pressure mercury lamp maintained at an ambient temperature of 70 ° C. is applied with an ultraviolet ray of 300 mJ / cm ² . The film was irradiated with light to fix the orientation and cooled to room temperature to obtain an optical film.

  Since the PEN film as the base material is optically anisotropic and it is difficult to observe the orientation state of the birefringent layer (liquid crystalline composition layer), the birefringent layer is placed on the triacetyl cellulose film with an acrylic adhesive. After the transfer, the alignment state was observed with a polarizing microscope or visually (FIGS. 2 and 3). The results are shown in Table 1.

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. 2 is a polarizing micrograph of the optical film obtained in Example 1. FIG. 6 is a polarizing micrograph of an optical film obtained in Comparative Example 3.

Explanation of symbols

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

Claims (9)

  In the method for producing an optical film comprising a step of forming an alignment film on a substrate, a step of rubbing the formed alignment film, and then a step of forming a birefringent layer on the alignment film subjected to the rubbing treatment. The method for producing an optical film, wherein the amount of ionic impurities in the film is 2000 mass ppm or less.   The method for producing an optical film according to claim 1, wherein the ionic impurities are sodium ions.   The method for producing an optical film according to claim 2, wherein the sodium ion is derived from sodium acetate.   The method for producing an optical film according to claim 1, wherein the alignment film is polyvinyl alcohol.   The method for producing an optical film according to claim 4, wherein the degree of saponification of the polyvinyl alcohol is 98% or more.   The method for producing an optical film according to claim 1, wherein the base material is a plastic film.   The method for producing an optical film according to claim 1, wherein the birefringent layer is formed of a material containing a liquid crystal compound.   The optical film manufactured by the manufacturing method in any one of Claims 1-7.   A liquid crystal display device using the optical film according to claim 8.