JP2011175021A - Method for producing optical film, and optical film and optical element obtained by using the same, - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an optical film with which phase difference fluctuation of a COP film by heat and tension is suppressed, in producing the optical film formed by forming a liquid crystal layer composed of a liquid crystalline composition directly on the COP film having a phase difference. <P>SOLUTION: In the method for producing the optical film: a step to laminate a protective layer on one face of a continuously transferred cycloolefin polymer film; a step to coat another face opposite to the protective layer with the liquid crystalline composition; a step to align the liquid crystalline composition with a heating process; and a step to fix the aligned composition are conducted in this order. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing an optical film obtained by aligning and fixing a liquid crystalline composition on a cycloolefin polymer (hereinafter referred to as COP) film having no alignment film, and an optical element using the method.

  An optical film having a refractive index anisotropy plays an important industrial role such as being used for improving the image quality of a liquid crystal display device. Films having refractive index anisotropy can be broadly classified into those obtained by stretching a plastic film and those obtained by aligning liquid crystals. The latter is more remarkable because it has the potential to realize various refractive index structures. Alignment films made by aligning liquid crystal polymers show epoch-making performance as color compensators and viewing angle improvement plates for liquid crystal display devices, and improve the performance, weight and thickness of liquid crystal display devices. Has contributed.

  For example, a film having a larger refractive index in the film thickness direction is considered to be effective for improving the viewing angle of a liquid crystal display device, but such a film is considered to be a shortcut to use the homeotropic alignment (vertical alignment) of the liquid crystal. It is done. Homeotropic alignment of liquid crystal molecules is that the long-axis molecular direction of the liquid crystal is aligned in a direction substantially perpendicular to the substrate. It is well known that homeotropic alignment can be obtained by applying an electric field by putting liquid crystal in two glass substrates as in a liquid crystal display device, but it is very difficult to make this alignment state into a film. However, there are problems with the methods reported in the past.

  For example, in Patent Documents 1 and 2, a main-chain polymer liquid crystal is homeotropically aligned, and then a film is obtained by glass fixation. However, in order to fix the alignment of the liquid crystal molecules, a substrate serving as a support such as a film or glass is necessary. In order to obtain an optical film having a desired function utilizing the alignment of the liquid crystal molecules, In order to keep the alignment, the liquid crystal molecule layer can be isolated or transferred to another substrate, or incorporated into the optical film including a transparent support substrate that is unnecessary as a function of the optical film. Inclusion of the transparent support has caused problems such as deterioration of optical characteristics and increase in thickness.

  The present inventors have previously developed an optical film in which a cycloolefin polymer (COP) film used separately is used as a substrate and a liquid crystal molecular layer is coated thereon as an optical film for a liquid crystal display device. In this case, it is not necessary to isolate the liquid crystal molecular layer or transfer it to another substrate, and good display characteristics can be realized by directly incorporating the liquid crystal display element. However, when a COP film is continuously coated with a liquid crystal molecular layer, and the liquid crystal molecules are aligned and fixed, it is necessary to apply tension for continuous film transport, and to align the liquid crystal molecules. However, in the case of a COP film alone, phase difference variation occurs in the film tension direction due to the influence of tension and heat, and it may be difficult to produce an optical film having a desired phase difference.

Japanese Patent No. 2853064 Japanese Patent No. 3018120

  An object of the present invention is to provide a method for producing an optical film capable of suppressing the phase difference variation of the COP film due to the influence of heat and tension when forming the liquid crystalline composition on the COP film. In addition, an object of the present invention is to provide an optical film and an optical element obtained by the above method.

As a result of diligent research on the solution of the above problems, the present inventors have found that the influence of tension and heat can be suppressed to the maximum by bonding a protective film to the COP film, and the present invention has been completed. is there.
That is, the present invention is as follows.

[1] A step of laminating a protective layer on one side of a continuously conveyed cycloolefin polymer film, a step of coating a liquid crystalline composition on the surface opposite to the protective layer, and heat treatment A method for producing an optical film, wherein the step of aligning and the step of fixing the alignment are performed in this order.
[2] The method for producing an optical film as described in [1], wherein the protective layer is a poly-α-olefin film or a polyester film.
[3] The method for producing an optical film as described in [1] or [2], wherein the protective layer is a polyethylene terephthalate film.
[4] The method for producing an optical film as described in any one of [1] to [3], wherein the liquid crystalline composition is homeotropically aligned.
[5] An optical film obtained by the production method according to any one of [1] to [4].
[6] An optical element obtained using the optical film according to [5].

  By the method of the present invention, it is possible to produce an optical film in which variation in retardation of the COP film due to heat and tension is suppressed.

Hereinafter, the present invention will be described in detail.
The present invention includes a step of laminating a protective layer on one side of a continuously conveyed cycloolefin polymer film, a step of coating a liquid crystalline composition on the surface opposite to the protective layer, and a heat treatment to form the liquid crystalline composition. Is a method for producing an optical film by performing the steps of orienting and fixing the orientation in this order.

  That is, in the present invention, when a liquid crystal composition is coated on a COP film and an optical film is manufactured through processes such as heat treatment and immobilization, the COP film is coated with the COP film prior to coating the liquid crystal composition. It is essential to laminate a protective film on the film. This is because when the COP film is not laminated, the COP film is subjected to unintended stretching and shrinkage due to the influence of heat and film tension in the heat treatment step, and the retardation value governing the optical characteristics fluctuates.

  In this invention, a protective layer is a layer affixed on the single side | surface of a COP film, and is a film (henceforth a protective film) obtained from various polymers. Examples of the polymer constituting the protective film include various α-olefin polymers: polymers (including copolymers) obtained from ethylene and propylene, poly-4-methylpentene-1, etc .; polyesters: polyethylene terephthalate ( PET), polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate (PEN) and the like; polyamide: various nylons (trade names) and the like; polyvinyl alcohol; various celluloses (diacetyl cellulose, triacetyl cellulose) and the like. These may be a mixture.

The protective film may be produced by a normal melt extrusion method or solution casting method, and may be uniaxially stretched or biaxially stretched as necessary.
Of these protective films, poly-α-olefins and polyesters are preferred from the standpoint of film availability and physical properties, among which polyethylene terephthalate films are particularly preferred.
Although there will be no restriction | limiting in particular if the film thickness of a protective film is the thickness suitable for the manufacturing method of the optical film of this invention, Preferably it is 5-100 micrometers, More preferably, it is 10-80 micrometers. Outside this range, it is not preferable because the strength at the time of processing becomes insufficient or becomes too thick.

Although some protective films do not particularly require an adhesive layer or an adhesive layer for lamination to the COP film depending on the molding conditions of the film, a protective film formed with a detachable adhesive layer or an adhesive layer is preferred and is applied in advance. It can also be appropriately selected from commercially available products on which an adhesive layer is formed.
Materials for forming the adhesive layer are known adhesives (for example, acrylic adhesives, polyester adhesives, urethane adhesives, polyether adhesives, rubber adhesives, silicone adhesives, polyamide adhesives). , Fluorine-based pressure-sensitive adhesive, etc.). An adhesive can be used individually or in combination of 2 or more types.
The protective film may be subjected to surface treatment such as corona discharge treatment or UV-ozone treatment to control the tackiness and adhesiveness.

  When laminating the protective film on the COP film, it is necessary to set an appropriate tension on both the COP film side and the protective film side. The tension from the feeding of the COP film and the protective film to the lamination and winding is preferably about 10 to 500 N / m and more preferably about 15 to 150 N / m per film width.

Next, a cycloolefin polymer (COP) film will be described.
The COP film is a film mainly composed of COP, and a film having a retardation function is preferable. COP is a general generic name for resins obtained by polymerizing cyclic olefins such as cyclohexene, cycloheptene, norbornene, tetracyclododecene, and cyclopentadiene, and derivatives thereof. Specifically, ring-opening polymers of cyclic olefins, addition polymers of cyclic olefins, random copolymers of cyclic olefins and α-olefins such as ethylene and propylene, and these are modified with unsaturated carboxylic acids or their derivatives. Examples of such graft-modified products can be given. Moreover, these hydrides are also mentioned. Products include ZEONEX, ZEONOR manufactured by ZEON CORPORATION, Arton manufactured by JSR Corporation, Essina manufactured by Sekisui Chemical Co., Ltd. Topas manufactured by Topas Advanced Polymers GmbH, Appel manufactured by Mitsui Chemicals, Inc. Can be mentioned.

  These COP films may be uniaxially stretched films or biaxially stretched films. Uniaxial stretching is preferably longitudinal uniaxial stretching using the difference in peripheral speed between two or more rolls, or tenter stretching in which both sides of the polymer film are gripped and stretched in the width direction. Biaxial optical anisotropy may be developed by stretching the polymer film in the longitudinal and transverse directions. Moreover, what performed the Z-axis orientation process etc. are mentioned. Further, for the purpose of controlling the adhesiveness of the COP film, surface treatment such as corona discharge treatment or UV-ozone treatment may be performed.

The retardation value in the COP film plane (hereinafter abbreviated as Re1) is Re1 when the main refractive index in the film plane is nx, ny, the main refractive index in the thickness direction is nz, and the thickness is d1 (nm). = (Nx−ny) × d1 [nm], depending on the application, such as when used as a viewing angle improving film of a liquid crystal display device, and also when used as a viewing angle improving film Although it cannot be generally described because it depends on the optical parameters, Re1 is usually in the range of 30 nm to 500 nm, preferably 50 nm to 400 nm, for monochromatic light of 550 nm. The retardation value in the thickness direction (hereinafter abbreviated as Rth1) is represented by Rth1 = {(nx + ny) / 2−nz} × d1 [nm], and is usually 0 to 300 nm, preferably 0 to 200 nm. Preferably, it is controlled to 0 to 150 nm. The thickness of the COP film is preferably 10 to 400 μm, and most preferably 15 to 100 μm.
In addition, the optical property as the whole film may satisfy the said conditions using two or more polymer films.

  By setting the Re1 value and the Rth1 value in the above ranges, the viewing angle improving film of the liquid crystal display device can widen the viewing angle while correcting the color tone of the liquid crystal display. An improvement effect can be obtained. When the Re1 value is smaller than 30 nm or larger than 500 nm, a sufficient viewing angle improvement effect cannot be obtained, or unnecessary coloring may occur when viewed from an oblique direction. Further, when the Rth1 value is smaller than 0 nm or larger than 300 nm, a sufficient viewing angle improvement effect cannot be obtained, or unnecessary coloring may occur when viewed from an oblique direction.

  The liquid crystalline composition used in the present invention is not particularly limited as long as it is a liquid crystal material capable of fixing its orientation after coating on a COP film. Examples of the liquid crystal compound constituting the liquid crystal composition include a material composed of a low molecular liquid crystal compound, a liquid crystal polymer compound, and a mixture thereof.

  As the low-molecular liquid crystal compound, a compound having a reactive group that reacts with light or heat is preferable because the alignment can be easily fixed. As the reactive group, a vinyl group, an acryloyl group, a vinyloxy group, an oxiranyl group, an oxetanyl group, an aziridinyl group and the like are preferable, but other reactive groups such as an isocyanate group, a hydroxyl group, an amino group, an acid anhydride group, a carboxyl group, and the like. Groups and the like can also be used depending on the reaction conditions.

  The liquid crystalline polymer compound includes a main chain type liquid crystal polymer and a side chain type liquid crystal polymer, and any of them can be used. Examples of the main chain type liquid crystal polymer include polyester, polyesterimide, polyamide, and polycarbonate. Among these, liquid crystalline polyesters are preferable from the viewpoint of easiness of synthesis, orientation, glass transition point, and the like, and main chain type liquid crystalline polyesters bonded with cationic polymerizable groups are particularly preferable. Examples of the side chain type liquid crystal polymer include polyacrylate, polymalonate, polyether, polysiloxane and the like. The liquid crystal polymer preferably has the above-described reactive group bonded thereto.

  The main-chain 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, it is a main-chain liquid crystalline polyester containing at least two kinds of structural units (C) as essential units, and includes a structural unit having a cationically polymerizable group at least at one end of the main chain. The 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 binding position of the cationic polymerizable group or the substituent containing the cationic polymerizable group and the phenolic hydroxyl group or carboxyl group is 1, 4 when the skeleton to which these groups are bonded is a benzene ring. From the viewpoint of liquid crystallinity, a positional relationship of-, a 2,6- positional relationship in the case of a naphthalene ring, and a 4,4'- positional relationship in the case of a biphenyl skeleton or a stilbene skeleton are preferable. 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 preferred.

  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. It is desirable that the total number of equivalents of the respective functional groups be roughly aligned at this stage. That is, when the structural unit (D) is a unit having a free carboxyl group, (number of moles of (A) × 2) = (number of moles of (B) × 2) + number of moles of (D) ), When the 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 generally satisfy the 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). There is no restriction | limiting in particular as another structural unit which can be contained, A compound (monomer) well-known in the said field | area 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 phenyl 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 such that the logarithmic viscosity η measured at 30 ° C. in a phenol / tetrachloroethane mixed solvent (mass ratio 60/40) is 0.03 to 0.50 dl / g. Preferably it is 0.05-0.15 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.

The side chain type liquid crystal polymer is a polymer having a group (mesogen) that exhibits liquid crystallinity in the side chain. As an example, a copolymer of a (meth) acrylic compound having an oxetane group and a polymerizable liquid crystal compound is used. Can be mentioned. In the following description, “methacryl” and “acryl” are collectively referred to as “(meth) acryl”.
As the (meth) acrylic compound having an oxetane group, a compound represented by the following general formula (1), (2) or (3) is preferable.

In Formula (1), Formula (2), and Formula (3), R ¹ each independently represents hydrogen or a methyl group, R ² each independently represents hydrogen, a methyl group, or an ethyl group, and L ¹ 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 , An integer from 0 to 10. In addition, L ¹ is a single bond means that a group bonded through L ¹ is directly bonded, and for example, in the case of AL ¹ -B, it is AB.

These compounds are not necessarily required to exhibit liquid crystallinity. Moreover, you may use the compound of Formula (1)-(3) as a 2 or more types of mixture.
Although various compounds corresponding to these formulas (1) to (3) can be mentioned, the following compounds can be mentioned as preferred examples.

The method for synthesizing these (meth) acrylic compounds having an oxetane group is not particularly limited, and can be synthesized by applying a method used in ordinary organic chemistry synthesis methods.
For example, by connecting a site with an oxetane group and a site with a (meth) acrylic group by means such as Williamson's ether synthesis or ester synthesis using a condensing agent, the oxetane group and the (meth) acrylic group are completely A (meth) acrylic compound having an oxetane group having two different reactive groups can be synthesized.
In the synthesis, since the oxetane 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.

As the side chain type liquid crystal polymer, a side chain type liquid crystal polymer represented by the following general formula (4) is particularly preferable.
In the present invention, when a side chain type liquid crystal polymer is used as the liquid crystal compound, the liquid crystal composition contains a (meth) acryl compound having an oxetane group (for example, compounds of the above formulas (1) to (3)). It is preferable because the adhesion between the COP film, which is a hardly adhesive material, and the liquid crystal layer is greatly improved. When the liquid crystal composition does not contain a (meth) acrylic compound having an oxetane group, sufficient adhesion between the COP film and the liquid crystal layer cannot be obtained. Although the mechanism of its action is not clear, it is presumed that the (meth) acrylic compound having an oxetane group has some mediating effect on adhesion between the COP film and a liquid crystal composition having insufficient affinity.

In the formula (4), 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 0 And a, b, c, d, e and f are the molar ratio of each unit in the polymer (a + b + c + d + e + f = 1.0, but not c + d + e = 0. Also, only the substituents are different. In the case of a unit, the molar ratio is counted as the same unit). Furthermore, it is necessary to exhibit liquid crystallinity.

If this requirement is satisfied, the molar ratio of each unit in the polymer may be arbitrary, 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

R ⁴ is preferably hydrogen, methyl group, butyl group, methoxy group, cyano group, bromo group, or fluoro group, and particularly preferably hydrogen, methoxy group, or cyano group. L ² is preferably a single bond, —O—, —O—CO— or —CO—O—. R ⁶ is preferably a hydrocarbon group having 2, 3, 4, ⁶ , 8 or 18 carbon atoms.

  The side chain type liquid crystalline polymer represented by the general formula (4) is easily obtained by copolymerizing the (meth) acrylic group of each (meth) acrylic compound 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.

  The side chain type liquid crystalline polymer 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.

  The liquid crystalline composition used in the present invention may further contain a dioxetane compound represented by the following general formula (5). The dioxetane compound represented by the general formula (5) can be used regardless of the presence or absence of liquid crystallinity, but preferably exhibits liquid crystallinity.

In Formula (5), 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 (6) or formula (7). P ¹ in formula (6) and formula (7) each independently represents a group selected from formula (8), P ² represents a group selected from formula (9), 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- (6)
-P ¹ -L ⁴ -P ^1- (7)

  In formula (8) and formula (9), Et, iPr, nBu and tBu represent an ethyl group, an isopropyl group, a normal-butyl group and a tertiary-butyl group, respectively.

In the formula (5), the linking groups connecting the left and right oxetane groups as viewed from the M ¹ group may be different (asymmetric type) or the same (symmetric type), and the liquid crystallinity may vary depending on the structure. Good.
The compound represented by formula (5) is a number of compounds from a combination of L ^3, X ¹ and M ¹ are exemplified, preferably may be mentioned the following compounds.

  These compounds can be synthesized according to a usual synthesis method in organic chemistry, and the synthesis method is not particularly limited.

In the liquid crystalline composition used in the present invention, the (meth) acrylic compound having any oxetane group represented by formulas (1) to (3), a liquid crystalline compound, and a formula (if necessary) ( The composition (mass ratio) of each component of the dioxetane compound represented by 5) is a compound having an oxetane group represented by formulas (1) to (3): a liquid crystal compound: a dioxetane represented by formula (5) It is preferable that it is compound = 1-30: 100: 0-40, More preferably, it is 3-20: 100: 0-30.
Outside this range, it is not possible to obtain a liquid crystal film having excellent homeotropic alignment retention ability and interlayer adhesion between the COP film and the liquid crystal layer.

  After the liquid crystalline composition is subjected to an alignment treatment, the liquid crystalline state is fixed by polymerizing a cationic polymerizable group contained in the composition and crosslinking. Thereby, the heat resistance of a liquid crystal film improves. Accordingly, in order to easily and rapidly proceed cationic polymerization, the liquid crystalline composition may contain a photocation generator and / or a thermal cation generator that generates cations by external stimuli such as light and heat. preferable. If necessary, various sensitizers may be used in combination.

The photo cation generator means a compound capable of generating a cation by irradiating with light having an appropriate wavelength, and examples thereof 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 ⁻ and Ar ₂ I ⁺ PF ₆ ⁻ (wherein Ar represents a phenyl group or a substituted phenyl group). In addition, sulfonate esters, triazines, diazomethanes, β-ketosulfone, iminosulfonate, benzoinsulfonate, and the like can also be used.

  The thermal cation generator is a compound capable of generating a cation by being heated to an appropriate temperature, for example, benzylsulfonium salts, benzylammonium salts, benzylpyridinium salts, benzylphosphonium salts, hydrazinium salts, carboxylic acid esters, Examples thereof include sulfonic acid esters, amine imides, antimony pentachloride-acetyl chloride complexes, diaryliodonium salts-dibenzyloxycopper, and boron halide-tertiary amine adducts.

  The amount of these cation generators added to the liquid crystal composition varies depending on the structure of the mesogen portion and spacer portion of the compound constituting the liquid crystal composition, the oxetane group equivalent, the alignment conditions of the liquid crystal composition, and the like. Although it cannot be generally stated, it is usually 100 mass ppm to 20 mass%, preferably 1000 mass ppm to 10 mass%, more preferably 0.5 mass% to 8 mass%, most preferably based on the side chain type liquid crystalline polymer. Is in the range of 1% to 6% by weight. If the amount is less than 100 mass ppm, the amount of cations generated may not be sufficient and polymerization may not proceed. If the amount is more than 20 mass%, the remaining cation generator remains in the liquid crystal film. It is not preferable because there is a risk that the light resistance and the like may deteriorate due to an increase in the number of objects.

  The liquid crystal composition used in the present invention may contain various compounds that can be mixed in a range that does not impair the liquid crystal properties of the liquid crystal composition. Examples of the compound that can be contained include radical polymerizable groups such as vinyl groups and (meth) acryl groups, and cation polymerizable groups such as oxetane groups (excluding compounds having the above oxetane group), oxiranyl groups, and vinyloxy groups. Various polymerizable compounds, a compound having a reactive group such as a carboxyl group, an amino group, and an isocyanate group, and various polymer compounds having a film forming ability can also be blended. In addition, when a surfactant, antifoaming agent, leveling agent, plasticizer, ionic liquid, ionic liquid crystal, etc., and a compound having a reactive functional group or a low molecular or high molecular liquid crystal substance are used, the respective functionalities are used. A reaction initiator, activator, sensitizer and the like suitable for the group may be added within a range not departing from the object of the present 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.

Next, the manufacturing method of an optical film is demonstrated.
First, as a method for forming a liquid crystal layer by spreading a liquid crystalline composition on a surface opposite to a surface on which a protective film of a COP film laminated with a protective film is formed, a solution of the liquid crystalline composition is COP. The method of drying a coating film and distilling a solvent after apply | coating on a film 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 and can be distilled off under appropriate conditions and has little influence on the COP film. In particular, ketones such as acetone, methyl ethyl ketone, isophorone and cyclohexanone, ether alcohols such as butoxyethyl alcohol, hexyloxyethyl alcohol, methoxy-2-propanol and benzyloxyethyl alcohol, glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether , Esters such as ethyl acetate, ethyl lactate and γ-butyrolactone, phenols such as phenol and chlorophenol, N, N-dimethylformamide, N, N-dimethylacetamide, N-meth Amides such as Rupiroridon, chloroform, tetrachloroethane, halogenated such or a mixture of these systems, such as dichlorobenzene are preferably used. Further, in order to form a uniform coating film on the COP film, a surfactant, an antifoaming agent, a leveling agent, and 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. For example, a flexographic printing method, an offset printing method, a dispenser method, a gravure coating method, a micro gravure method, a bar coating method, a screen printing method, a lip coating method, a die coating method, and the like can be given. Of these, gravure coating, kiss coating, lip coating and die coating are preferred.
Further, in order to form a uniform coating film on the COP film, corona treatment or plasma treatment may be performed as surface modification treatment before coating.

  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 generally determined because it is adjusted depending on the liquid crystal composition to be used and the intended use of the liquid crystal layer to be obtained. However, the film thickness after drying is 0.1 to 50 μm, preferably 0.2 to 20 μm. More preferably, it is 0.3 to 10 μm. If the film thickness is outside this range, the desired effect cannot be obtained, and the orientation becomes insufficient.

  In order to align the liquid crystal layer in a certain direction, alignment treatment may be performed on the COP film or after coating the liquid crystalline composition as necessary. As long as this process is a method in which the liquid crystalline composition is uniformly aligned, a known method can be adopted without any particular limitation. For example, a rubbing treatment on a COP film or a method of aligning in a certain direction by irradiating polarized light with high fluidity after coating with a liquid crystalline composition containing a photosensitive portion. However, in the case of homeotropic alignment, a special alignment process may not be required.

  Subsequently, after aligning the liquid crystal in the liquid crystal layer formed on the COP film by a method such as heat treatment, a reactive group is reacted by light irradiation and / or heat treatment as necessary to fix the alignment. 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 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. It is preferable to perform heat treatment at a temperature equal to or higher than the glass transition point (Tg) of the liquid crystalline composition, more preferably at a temperature 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 COP film 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.

When a liquid crystal composition containing a reactive group is used after forming the liquid crystal layer by the above-described method, a reaction in which the liquid crystal composition is contained in the composition while maintaining the liquid crystal alignment state. The function of the initiator is expressed and the reactive group is reacted to fix the orientation.
When the reaction initiator exhibits the function of the initiator by light irradiation, the light irradiation method includes a metal halide lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a low pressure mercury lamp having a spectrum in the absorption wavelength region of the reaction initiator used. The reaction initiator is activated by irradiating light from a light source such as a xenon lamp, an arc lamp, or a laser. The integrated dose is usually 10 to 2000 mJ / cm ² , preferably 50 to 1000 mJ / cm ² . 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 at the time of light irradiation is preferably a temperature range in which the liquid crystalline composition takes liquid crystal alignment. In order to sufficiently increase the reaction effect, light irradiation is performed at a liquid crystal phase temperature equal to or higher than Tg of the liquid crystalline composition. Is preferred.
Thus, an optical film having a liquid crystal layer with the orientation fixed on the COP film is formed. The liquid crystal layer on the COP film may be provided with a surface protective layer in order to protect the surface, and examples thereof include a coating type adhesive and a protective film made of a polymer film.

  The optical film of the present invention can usually be used as an optical element combined with a polarizing plate as a laminate. Moreover, you may laminate | stack with other various retardation films. The laminate is usually formed using an adhesive or a pressure-sensitive adhesive so as not to cause displacement or distortion in the polarizing plate or each film.

  As the polarizing plate, one having a translucent protective film on both sides or one side of the polarizing element is usually used. The polarizing element is not particularly limited, and various types can be used. Examples of polarizing elements include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films, and two colors such as iodine and dichroic dyes. And polyene-based oriented films such as those obtained by adsorbing a functional substance and uniaxially stretched, and polyvinyl chloride dehydrochlorinated products. Among these, those obtained by stretching a polyvinyl alcohol film and adsorbing and orienting a dichroic material (iodine, dye) are preferably used. The thickness of the polarizing element is not particularly limited, but is generally about 5 to 80 μm.

  A polarizing film using iodine, which is widely used, is manufactured by a continuous longitudinal uniaxial stretching process, and therefore has an absorption axis parallel to the longitudinal direction of the roll. Therefore, the long polarizing film stretched in a general longitudinal uniaxial direction and the long first optically anisotropic layer have the absorption axis of the polarizing film orthogonal to the slow axis of the first optically anisotropic layer. Thus, when laminating by roll-to-roll, it is preferable to use a transverse stretching machine so that the slow axis is orthogonal to the transport direction.

  A polarizing element in which a polyvinyl alcohol film is dyed with iodine and uniaxially stretched can be produced, for example, by dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  As the above-mentioned translucent protective film, an optically isotropic substrate is preferable. For example, a triacetyl cellulose film such as Fujitac (product of Fujifilm) or Konicatak (product of Konica), Arton film (product of JSR) COP films such as ZEONOR film, ZEONEX film (product of Nippon Zeon Co., Ltd.), TPX film (product of Mitsui Chemicals Co., Ltd.), acrylprene film (product of Mitsubishi Rayon Co., Ltd.), but heat resistance when used as a film for optical elements From the viewpoint of properties and moisture resistance, a triacetyl cellulose film and a COP film are preferable. Generally the thickness of a translucent protective film is 150 micrometers or less, and 1-100 micrometers is preferable. In particular, the thickness is preferably 5 to 50 μm.

Examples of the various retardation films include those formed from polymer films, liquid crystalline compounds and compositions.
The polymer film is formed from a polymer capable of developing birefringence. As the birefringent polymer film, those having excellent controllability of birefringence characteristics, transparency and heat resistance, and those having low photoelasticity are preferable. In this case, the polymer material to be used is not particularly limited as long as it is a polymer that can achieve uniform uniaxial orientation or biaxial orientation, but conventionally known materials that can be formed by a solution casting method or an extrusion molding method. Preferably, cycloolefin polymer, polycarbonate, polyarylate, polyester, polyamide, polyimide, polyamideimide, polyetherimide, polyether ketone, polyethersulfone, polysulfone, polystyrene, polyacetal, polyvinyl alcohol, polymethyl methacrylate, cellulose acylate, or , Or a polymer obtained by mixing two or more of these polymers.
The thickness of these films is preferably 10 to 100 μm, and particularly preferably 20 to 80 μm. If the thickness is too thick, the resulting laminate is too thick to satisfy the demand for thinning, and if it is too thin, the mechanical strength of the film cannot be maintained, which may cause problems such as tearing during production.

A retardation film in which the orientation of a liquid crystalline compound or composition is fixed is, for example, a thermotropic liquid crystalline compound exhibiting liquid crystallinity in a certain temperature range or a lyotropic liquid crystalline property exhibiting liquid crystallinity in a specific concentration range of a certain solution. Examples include a film in which a compound or a composition containing these is spread and oriented on a substrate to fix the orientation. In particular, the thermotropic liquid crystalline compounds are often used by mixing a plurality of liquid crystalline compounds in order to exhibit liquid crystallinity over a wide temperature range. The liquid crystalline compound may be a low molecular weight, a high molecular weight or a mixture thereof.
Examples of the liquid crystal phase of the liquid crystalline compound or composition before immobilization include a nematic phase, a twisted nematic phase, a cholesteric phase, a smectic phase, and a discotic nematic phase. Examples of the alignment form include homogeneous alignment that is horizontally aligned on the alignment substrate, homeotropic alignment that is aligned vertically, and tilt alignment and hybrid alignment that are considered to be an intermediate state between the two.

These liquid crystalline compounds and compositions may be compounds that are polymerized or crosslinked by ultraviolet rays or heat in order to fix the alignment state. Such liquid crystalline compounds include compounds having polymerizable groups such as (meth) acryloyl groups, epoxy groups, vinyl groups, oxetanyl groups, or reactive groups such as amino groups, hydroxyl groups, carboxyl groups, and isocyanate groups. A compound having a functional group is preferable, and examples thereof include compounds described in WO97 / 44703 and WO98 / 00475.
The thickness of the liquid crystal layer varies depending on the desired front retardation and thickness retardation value, and also varies depending on the birefringence of the aligned liquid crystalline compound, but is preferably 0.05 to 20 μm, more preferably Is about 0.1 to 10 μm. If the film thickness is outside this range, the desired effect cannot be obtained, and the orientation becomes insufficient.

  It should be noted that the pressure-sensitive adhesive and adhesive used for laminating and transferring the linear polarizing plate, the optical film and each optical anisotropic element (hereinafter, both are collectively referred to as “sticky / adhesive”) are used for the formation of a viscous / adhesive layer. The adhesive is not particularly limited as long as it is optically isotropic and transparent. For example, an acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer as a base polymer can be appropriately selected and used. Moreover, the reactive thing which reacts by external stimuli, such as light, an electron beam, and heat | fever, and superpose | polymerizes or bridge | crosslinks can also be used. Among these, those having excellent optical transparency, such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and having excellent weather resistance, heat resistance, and the like can be preferably used.

The formation of the adhesive / adhesive layer can be performed by an appropriate method. As an example, for example, a 10-40 mass% adhesive / adhesive solution in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of an appropriate solvent alone or a mixture such as toluene and ethyl acetate is used. Prepare and apply it directly on the polarizing plate, optical film or optical element layer by an appropriate development method such as a casting method or a coating method, or an adhesive / adhesive layer on the separator according to the above. A method of forming and transferring it onto the polarizing plate, the optical film or the optical element layer can be mentioned. In addition, the adhesive / adhesive layer includes, for example, natural and synthetic resins, in particular, tackifier resins, fillers made of glass fiber, glass beads, metal powder, other inorganic powders, pigments, coloring An additive that may be added to the adhesive layer, such as an agent and an antioxidant, may be contained. Further, it may be an adhesive / adhesive layer containing fine particles and exhibiting light diffusibility.
The thickness of the adhesive / adhesive layer is not particularly limited as long as the member to be adhered can be adhered and sufficient adhesion can be maintained. Can be selected. In view of the strong demand for reduction in the total thickness of the elliptically polarizing plate, the thickness of the adhesive / adhesive is preferably thin, but is usually 2 to 80 μm, preferably 5 to 50 μm, and more preferably 10 to 40 μm. Outside this range, it is not preferable because the adhesive force is insufficient, or it oozes out from the end portion during lamination or storage of the elliptically polarizing plate.

  The optical film or optical element of the present invention has various display modes depending on the in-plane retardation value, retardation value in the thickness direction, etc. of the liquid crystal layer, COP film, and various retardation films constituting the optical film or optical element. It can be used for liquid crystal cells and liquid crystal display devices. For example, TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensatory Bend), ECB (Electrically Controlled Birefringence) STN (Supper Twisted Nematic), VA (Vertically Aligned), and HAN (Hybrid Aligned Nematic) Various display modes can be listed.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The analysis and measurement methods used in the examples are as follows.
(1) Measurement of molecular weight The number average molecular weight (Mn) and the weight average molecular weight (Mw) of the liquid crystalline polymer were determined by dissolving TSK-GEL SuperH1000, SuperH2000, SuperH3000, and SuperH4000 using a Tosoh 8020GPC system. They were connected in series, and tetrahydrofuran was used as an eluent, and measurement was performed with an ultraviolet detector (wavelength 254 nm). Polystyrene standards were used for molecular weight calibration.
(2) Microscope observation The alignment state of the liquid crystal was observed with an Olympus BH2 polarizing microscope.
(3) Parameter measurement of liquid crystal film Using an automatic birefringence meter KOBRA21 ADH manufactured by Oji Scientific Instruments Co., Ltd., light having a wavelength of 550 nm was used.

[Example 1]
A side chain type liquid crystalline polymer represented by the following formula (10) was synthesized by radical polymerization. The molecular weight measured by GPC was in terms of polystyrene, and the weight average molecular weight was 9,700. In addition, the description in Formula (10) represents the component ratio of each unit, and does not mean a block polymer.
10 g of the acrylic compound represented by the formula (11), 85 g of the side chain type liquid crystalline polymer represented by the formula (10), and 5 g of the dioxetane compound represented by the formula (12) are dissolved in 900 ml of cyclohexanone, After adding 10 g of a 50% propylene carbonate solution of triallylsulfonium hexafluoroantimonate (manufactured by Aldrich, reagent) in the dark, the solution is filtered through a polytetrafluoroethylene filter having a pore size of 0.45 μm. A solution was prepared.

A COP film Arton (JSR Co., Ltd., Re1 = 100 nm, film thickness 28 μm) and a polyethylene terephthalate (PET) protective film HP25S (Panac Co., Ltd., film thickness 25 μm) so that the adhesive surface is in contact with the COP film. The above solution was applied to the COP film side of this film by a die coating method, then continuously dried for 5 minutes in a 60 ° C. drying furnace, and heat treated for 2 minutes in a 90 ° C. heat treatment furnace. The layers were oriented and the film was once wound up. The tension at the time of film conveyance at this time was 30N. Next, as the orientation fixing treatment, the above-mentioned film is drawn out, irradiated with 300 mJ / cm ² ultraviolet light (however, the amount of light measured at 365 nm) with a high-pressure mercury lamp lamp, the liquid crystal layer is cured, and the optical film (liquid crystal layer / COP film / PET protective film) was obtained.

  When the protective film was peeled off from the obtained optical film and observed under a crossed Nicols polarizing microscope, there was no disclination and the monodomain was uniformly oriented. When this film was tilted and light was incident from an oblique direction and observed in the same manner with crossed Nicols, light transmission was observed. Moreover, the optical phase difference of the film was measured by an automatic birefringence measuring apparatus KOBRA21ADH. When measurement light is incident on the sample surface perpendicularly or obliquely, the phase difference (in-plane retardation) in the perpendicular direction to the sample surface is 100 nm, and the phase difference is obliquely applied in the slow axis direction of the liquid crystal layer. As a result of measurement, the retardation value decreased with an increase in the incident angle of the measurement light, and became 90 nm at an oblique 50 ° azimuth.

  In addition, the protective film was peeled off from the optical film obtained for comparison, and the liquid crystal layer was completely wiped off using a cyclohexanone solvent. When the optical retardation was measured in the same manner as described above, the retardation in the direction perpendicular to the sample surface was measured. (In-plane retardation) is 100 nm, and the phase difference is measured obliquely with the slow axis direction of the COP film as the rotation axis. As a result, the phase difference value increases as the incident angle of the measuring light increases, and the oblique angle is 50 °. The phase difference value at the orientation was 125 nm. From these facts, it was found that there was no phase difference fluctuation of the COP film while receiving the heat treatment necessary for the alignment of the liquid crystal molecules and the tension applied in the continuous process.

This measurement confirmed that the retardation of the liquid crystal layer alone was good homeotropic alignment because Re was estimated to be 0 nm and Rth was −170 nm.
Moreover, when the liquid crystal film is peeled off from the protective film and mounted on an IPS type liquid crystal display, the viewing angle is widened compared to the case where the liquid crystal film of the present invention is not used, and a good image can be obtained even when viewed obliquely. I understood that.

[Example 2]
Paste K8000 (manufactured by DIC, 30 μm thickness), which is a polypropylene (PP) -based protective film, onto COP film Arton (JSR, Re1 = 100 nm, film thickness 28 μm) so that the adhesive surface is in contact with the COP film. Then, the solution of the liquid crystal composition prepared in Example 1 was applied to the COP film side of this film by a die coating method, and then continuously dried in a drying furnace at 60 ° C. for 5 minutes, and a heat treatment furnace at 90 ° C. The film was heat treated for 2 minutes to orient the liquid crystal layer, and the film was wound up once. The tension at the time of film conveyance at this time was 30N. Next, as the orientation fixing treatment, the above-mentioned film is drawn out, irradiated with 300 mJ / cm ² ultraviolet light (however, the amount of light measured at 365 nm) with a high-pressure mercury lamp lamp, the liquid crystal layer is cured, and the optical film (liquid crystal layer / COP film / PP protective film) was obtained.

  When the protective film was peeled off from the obtained optical film and observed under a crossed Nicols polarizing microscope, there was no disclination and the monodomain was uniformly oriented. When this film was tilted and light was incident from an oblique direction and observed in the same manner with crossed Nicols, light transmission was observed. Moreover, the optical phase difference of the film was measured by an automatic birefringence measuring apparatus KOBRA21ADH. When the measurement light is incident on the sample surface perpendicularly or obliquely, the phase difference (in-plane retardation) in the perpendicular direction with respect to the sample surface is 100.5 nm, which is obliquely aligned with the slow axis direction of the liquid crystal layer. When the phase difference was measured, the phase difference value decreased with an increase in the incident angle of the measurement light, and became 90.5 nm at an oblique 50 ° azimuth.

  In addition, the protective film was peeled off from the optical film obtained for comparison, and the liquid crystal layer was completely wiped off using a cyclohexanone solvent. When the optical retardation was measured in the same manner as described above, the retardation in the direction perpendicular to the sample surface was measured. The (in-plane retardation) is 100.5 nm, and the phase difference is measured obliquely with the slow axis direction of the COP film as the rotation axis. As a result, the retardation value increases as the incident angle of the measurement light increases. The phase difference value was 125.5 nm at 50 ° azimuth. From these, it was found that the phase difference fluctuation of the COP film can be suppressed by a slight amount while receiving the heat treatment necessary for the alignment of liquid crystal molecules and the tension applied in the continuous process.

This measurement confirmed that the retardation of the liquid crystal layer alone was good homeotropic alignment because Re was estimated to be 0 nm and Rth was −170 nm.
Also, when the optical film with the protective film peeled off is mounted on an IPS type liquid crystal display, the viewing angle is widened compared to the case where the liquid crystal film of the present invention is not used, and a good image can be obtained even when viewed obliquely. I understood that.

[Example 3]
COP film Arton (JSR Co., Ltd., Re1 = 100 nm, film thickness 28 μm) and polyethylene (PE) protective film Tretec 7332 (Toray Film Processing Co., Ltd., film thickness 30 μm) with COP adhesive side The film was bonded so as to be in contact with the film, and the liquid crystal composition solution prepared in Example 1 was applied to the COP film side of this film by a die coating method, and then continuously dried in a drying oven at 60 ° C. for 5 minutes. Heat treatment was performed for 2 minutes in a heat treatment furnace at 90 ° C., the liquid crystal layer was aligned, and the film was once wound up. The tension at the time of film conveyance at this time was 30N. Next, as the orientation fixing treatment, the above-mentioned film is drawn out, irradiated with 300 mJ / cm ² ultraviolet light (however, the amount of light measured at 365 nm) with a high-pressure mercury lamp lamp, the liquid crystal layer is cured, and the optical film (liquid crystal layer / COP film / PP protective film) was obtained.

  When the protective film was peeled off from the obtained optical film and observed under a crossed Nicols polarizing microscope, there was no disclination and the monodomain was uniformly oriented. When this film was tilted and light was incident from an oblique direction and observed in the same manner with crossed Nicols, light transmission was observed. Moreover, the optical phase difference of the film was measured by an automatic birefringence measuring apparatus KOBRA21ADH. When the measurement light is incident on the sample surface perpendicularly or obliquely, the phase difference (in-plane retardation) in the perpendicular direction to the sample surface is 101 nm, and the phase difference is obliquely applied in the slow axis direction of the liquid crystal layer. As a result of measurement, the retardation value decreased with an increase in the incident angle of the measurement light, and became 91 nm at an oblique 50 ° azimuth.

  In addition, the protective film was peeled off from the optical film obtained for comparison, and the liquid crystal layer was completely wiped off using a cyclohexanone solvent. When the optical retardation was measured in the same manner as described above, the retardation in the direction perpendicular to the sample surface was measured. (In-plane retardation) is 101 nm, and the retardation is measured obliquely with the slow axis direction of the COP film as the rotation axis. As a result, the retardation value increases with an increase in the incident angle of the measurement light, and the oblique retardation is 50 °. The phase difference value at the azimuth was 126 nm. From these, it was found that the phase difference fluctuation of the COP film can be suppressed by a slight amount while receiving the heat treatment necessary for the alignment of liquid crystal molecules and the tension applied in the continuous process.

This measurement confirmed that the retardation of the liquid crystal layer alone was good homeotropic alignment because Re was estimated to be 0 nm and Rth was −170 nm.
Also, when the optical film with the protective film peeled off is mounted on an IPS type liquid crystal display, the viewing angle is widened compared to the case where the liquid crystal film of the present invention is not used, and a good image can be obtained even when viewed obliquely. I understood that.

[Comparative Example 1]
The solution of the liquid crystal composition prepared in Example 1 was applied to COP film Arton (manufactured by JSR Corporation, Re1 = 100 nm, film thickness 28 μm) by the die coating method, and then continuously in a drying oven at 60 ° C. The film was dried, heat treated in a heat treatment furnace at 90 ° C. for 2 minutes, the liquid crystal layer was aligned, and the film was wound up once. The tension at the time of film conveyance at this time was 30N. Next, as the orientation fixing treatment, the above-mentioned film is fed out, irradiated with 300 mJ / cm ² ultraviolet light (however, the amount of light measured at 365 nm) with a high-pressure mercury lamp lamp, the liquid crystal layer is cured, and the liquid crystal film (liquid crystal layer / COP film) was obtained.

  When the obtained liquid crystal film was observed under a polarizing microscope in which the crossed Nicols were crossed, there was no disclination and the monodomain was uniformly oriented. When this film was tilted and light was incident from an oblique direction and observed in the same manner with crossed Nicols, light transmission was observed. Moreover, the optical phase difference of the film was measured by an automatic birefringence measuring apparatus KOBRA21ADH. When the measurement light is incident on the sample surface perpendicularly or obliquely, the phase difference (in-plane retardation) in the perpendicular direction to the sample surface is 103 nm, and the phase difference is obliquely applied in the slow axis direction of the liquid crystal layer. As a result of measurement, the phase difference value decreased with an increase in the incident angle of the measurement light, and became 93 nm at an oblique 50 ° azimuth.

  In addition, when the liquid crystal layer was completely wiped off from the obtained liquid crystal film using a cyclohexanone solvent and the optical phase difference was measured in the same manner as described above, the phase difference (in-plane phase difference) in the direction perpendicular to the sample surface was measured. Was 103 nm, and the phase difference was measured obliquely with the slow axis direction of the COP film as the rotation axis. As a result, the phase difference value increased with an increase in the incident angle of the measurement light. It became 129 nm. From these facts, it was found that, when subjected to the heat treatment necessary for the alignment of liquid crystal molecules and the tension applied in the continuous process, the COP film alone has a large phase difference fluctuation.

  The method of the present invention is useful as an optical element because an optical film in which fluctuations in retardation of the COP film are suppressed can be produced.

Claims (6)

  A step of laminating a protective layer on one side of a continuously conveyed cycloolefin polymer film, a step of coating a liquid crystalline composition on the surface opposite to the protective layer, and a step of aligning the liquid crystalline composition by heat treatment The method for producing an optical film, wherein the steps of fixing the orientation are performed in this order.   The method for producing an optical film according to claim 1, wherein the protective layer is a poly-α-olefin film or a polyester film.   The method for producing an optical film according to claim 1, wherein the protective layer is a polyethylene terephthalate film.   The method for producing an optical film according to claim 1, wherein the liquid crystalline composition is homeotropically aligned.   The optical film obtained by the manufacturing method in any one of Claims 1-4.   An optical element obtained using the optical film according to claim 5.