JP2009251411A - Method for manufacturing optical film, and liquid crystal display element using the film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film excellent in heat resistance and mechanical strength. <P>SOLUTION: The method for manufacturing the optical film includes a step to apply a photo-polymerizable liquid crystal composition to a substrate, subsequently to align the liquid crystal with heat treatment, and to immobilize the aligned state by irradiating actinic ray, and is characterized in that an inequality of Tm-T0>30°C holds, when the temperature of the substrate just before irradiation of the actinic ray is represented by T0(°C), and the maximum temperature of the substrate during irradiation is represented by Tm(°C). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical film useful in the liquid crystal display field, optical field, optoelectronic field, and the like, a method for producing the same, and a liquid crystal display element using the film.

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. .
On the other hand, the drive mode of the liquid crystal display is an OCB (optically compensated bend) type with improved response speed and viewing angle, VA (vertical alignment) mode and IPS (in-plane switching) in addition to the conventional TN mode and STN mode. The mode has begun to be actually used, and an optical film (retardation film) suitable for each driving mode is required. Examples of the retardation film include a film obtained by uniaxially or biaxially stretching a transparent plastic film, and a liquid crystalline film in which a liquid crystal compound is aligned.
The liquid crystalline film is attracting attention because various liquid crystal alignment forms can be obtained by selecting the conditions, and the film can be made thinner.

For the liquid crystal film, those using a polymerizable low-molecular liquid crystal compound (monomer) (Patent Documents 1 and 2) and the like, and even a high-molecular liquid crystal compound is a side chain type polymer having a relatively low melt viscosity before crosslinking. Those using molecular liquid crystal compounds are known (Patent Documents 3 and 4).
Patent Documents 1 and 2 disclose a method of performing photopolymerization near room temperature using a composition mainly composed of a monomer having a liquid crystal phase expression temperature near room temperature in order to avoid unexpected thermal polymerization. However, there are not many compounds having a liquid crystal phase expression temperature near room temperature, and there is a problem that the demands of the market cannot always be met.
Moreover, although patent document 3 is made to superpose | polymerize by the light irradiation under a heating, it is not described at all about the temperature change of a to-be-polymerized object, and exceeds liquid crystal phase temperature by the temperature rise accompanying light (UV) irradiation. There is a risk of an isotropic phase temperature. On the other hand, in Patent Document 4, UV irradiation is performed in a glass state, but in the glass state, the movement of molecules is frozen, and it is difficult to improve the degree of polymerization (degree of crosslinking).
On the other hand, a technique that takes into account temperature fluctuations during light irradiation is also known (Patent Documents 5 and 6), but it is necessary to adjust the liquid crystal compound to be used and the coating film thickness, and the allowable temperature fluctuation range. Small and precise temperature control is also required.
JP-A-8-231958 JP 2002-145830 A JP 2000-144133 A JP 2002-333524 A JP-A-8-043624 JP 2007-148098 A

  The present invention solves the above-mentioned problems without requiring complicated and precise temperature control, and provides a method for producing an optical film excellent in heat resistance and mechanical strength, and a liquid crystal display element equipped with the film. .

  The present inventors diligently studied the above-mentioned problem, and after aligning the photopolymerizable liquid crystal composition, focused on the conditions of the treatment for fixing the alignment state by irradiation with actinic rays such as UV. As a result of the study, the present inventors have found that the above problem can be solved when the temperature of the alignment substrate just before receiving irradiation with active light and during the irradiation satisfies certain conditions, and have completed the present invention.

That is, the means for solving the above problems are as follows.
[1] A step of applying a photopolymerizable liquid crystal composition on a substrate, aligning it by heat treatment, and fixing the alignment state by irradiation with actinic rays, and setting the substrate temperature immediately before receiving the actinic rays to T0 (.Degree. C.), Tm-T0> 30.degree. C., where Tm (.degree. C.) is the maximum temperature of the substrate being irradiated.

[2] Production of optical film as described in [1] above, wherein Tg-20 ° C. ≦ T0 ≦ Tg + 20 ° C. when the glass transition point of the photopolymerizable liquid crystal composition is Tg (° C.). Method.

[3] The production of an optical film as described in [1] or [2] above, wherein the photopolymerizable liquid crystal composition contains at least a side chain polymer liquid crystalline compound having a cationic polymerizable group. Method.

[4] The method for producing an optical film according to any one of [1] to [3], wherein an alignment film is provided on the substrate.

[5] The optical film as described in any one of [1] to [4] above, which includes a step of transferring a liquid crystal layer in which the alignment state is fixed onto a base material different from the substrate. Production method.

[6] The method for producing an optical film as described in any one of [1] to [5], wherein the alignment state is homogeneous alignment, hybrid alignment, or homeotropic alignment.

[7] An optical film produced by the production method according to any one of [1] to [6].

[8] A liquid crystal display device using the optical film according to [7].

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the optical film excellent in heat resistance, mechanical strength, and manufacturing efficiency, and the liquid crystal display element using the said optical film can be provided.

Hereinafter, the present invention will be described in detail.
Examples of the substrate (alignment substrate) used in the present invention include polyimide, polyphenylene sulfide, polyphenylene oxide, polyether ether ketone, polyether sulfone, polyethylene naphthalate, polyethylene terephthalate, polyarylate, triacetyl cellulose, poly (cycloolefin), and the like. This film can be exemplified. These substrates may be a uniaxially or biaxially stretched film or a film that has been subjected to a surface treatment such as easy adhesion or easy peelability. Depending on the production method, these films may exhibit sufficient alignment ability with respect to liquid crystal molecules in the photopolymerizable liquid crystal composition to be described later, and can be used as an alignment substrate as they are. The alignment ability is expressed or enhanced by performing operations such as irradiation with polarized light and irradiation with oblique light. Further, if necessary, an alignment film such as polyimide, polyvinyl alcohol, polyvinyl ether, polyvinyl cinnamate, and silane coupling agent may be provided on these substrate films to express desired alignment ability. Among these, a preferred alignment film is polyvinyl alcohol (PVA).

  When the PVA is used as an alignment film, the degree of saponification is 75% or more, preferably 80% or more. If the saponification degree is less than 75%, the film tends to absorb moisture, which may cause adverse effects on the alignment of the liquid crystal, and the wear resistance of the alignment film is also deteriorated.

  The arrangement of the hydroxyl unit and the acetyl group unit in the structure of the PVA is not particularly limited, and may be distributed randomly or in a block manner. Furthermore, the PVA may be a modified PVA having other structural units in addition to the hydroxyl unit or acetyl group unit. Examples of the modified PVA include those having a hydrocarbon group, a carbonyl group, or a carboxyl group as structural units other than the hydroxyl unit and the acetyl group unit. Examples of those having a hydrocarbon group include those in which the end of the main chain is alkylthio-modified, and those in which a structure having a hydrocarbon group is linked to a hydroxyl group via an ester bond, an ether bond, or an acetal bond. Can do.

The solvent for preparing the PVA solution is not particularly limited as long as it is a solvent capable of dissolving PVA. Usually, water is used, but a lower alcohol such as methanol, ethanol, isopropyl alcohol or a mixture thereof is used in combination. Also good. Moreover, you may heat in order to accelerate | stimulate melt | dissolution.
As water used for dissolution, water containing a large amount of (polyvalent) metal ions is not preferable, ion-exchanged water is preferable, and water having an electric conductivity of 10 μS / cm or less is more preferable. Water containing (polyvalent) metal ions is not preferred because it may react with PVA to form an insoluble compound.

The concentration of total PVA in the PVA solution depends on the target film thickness and cannot be generally stated, but is usually 1 to 10% by mass.
You may add additives, such as surfactant, an antifoamer, and a leveling agent which do not have a bad influence on application | coating or the orientation of a liquid crystal to this PVA solution. For the purpose of strengthening the PVA film, aldehydes, dialdehydes, dialdehyde starches, methylol compounds, cross-linking agents such as boric acid and borax may be added to the solution. Also, other polymers and other compounds can be added depending on the purpose.

An alignment film forming process in the case of using PVA as an alignment film will be described.
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 particularly a flexographic printing method, a dispenser method, a gravure coating method, a micro gravure method, and a screen printing method. Lip coat method, die coat method and the like. Among these, a gravure coating method, a lip coating method and a die coating method are preferable.

The substrate thus obtained or the substrate on which the alignment film is formed may be used as it is, or may be rubbed as necessary.
In the rubbing treatment, rubbing is performed at a predetermined arbitrary angle with respect to the longitudinal direction (hereinafter referred to as MD) of the long film, preferably at an angle of 0 ° to ± 45 °. In addition, this angle (rubbing angle) is positive when the rubbing surface is viewed from the top in a clockwise direction from the MD.

  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 the alignment substrate is placed on the stage (11) that conveys the long film (12) 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 transferred at a speed of 0.5 to 100 m / min, preferably 1 to 30 m / min, and the rubbing roll rotation speed is selected from the range of 0 to 1000, preferably 0 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, the rubbed surface may be subjected to a cleaning treatment by spraying pressurized gas, contacting with an adhesive roll, or the like.

About the photopolymerizable liquid crystal composition in this invention, the said composition should just show liquid crystallinity, and it is not necessary for each component which comprises the said composition to show liquid crystallinity entirely.
As a component constituting the photopolymerizable liquid crystal composition, a low-molecular liquid crystalline compound or a high-molecular liquid crystalline compound is used, preferably a high-molecular liquid crystalline compound, more preferably a polymer having a reactive group. A liquid crystal compound, more preferably a side chain polymer liquid crystal compound having a reactive group. As the reactive group, an addition polymerizable group such as a vinyl group, a (meth) acryloyl group, a vinyloxy group, an oxirane group, an oxetanyl group, or a cinnamoyl group is preferable, but by selecting conditions, a hydroxyl group, an amino group, an acid anhydride can be selected. Group, carboxyl group and the like.
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, non-liquid crystalline low molecular compounds, various activators and various additives such as surfactants that are miscible with the low-molecular liquid crystalline compounds and high-molecular liquid crystalline compounds. Leveling agents, antifoaming agents, antioxidants, dyes, pigments and the like can be added without departing from the scope of the present invention. The surfactant is used, for example, to improve the surface smoothness of the optical film, and specific examples include fluorine-based, acrylic-based, and silicon-based surfactants.

  Examples of the low-molecular liquid crystalline compound include low-molecular liquid crystalline compounds having a polymerizable group such as a (meth) acryloyl group, a vinyloxy 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, 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 can be mentioned, 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.

  The compound for introducing the structural unit (B) is preferably a compound represented by the following general formula, specifically, terephthalic acid, isophthalic acid, phthalic acid or the like, or a substituted product thereof, 4,4′-stilbene Examples thereof include 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 a substituted product 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.

  The compound for introducing the structural unit (C) is preferably a compound represented by the following general formula, specifically, hydroxybenzoic acid or a substituted product thereof, 4′-hydroxy-4-biphenylcarboxylic acid or a substituted product thereof. , 4′-hydroxy-4-stilbene carboxylic acid or a substituted product thereof, 6-hydroxy-2-naphthoic acid, 4-hydroxycinnamic acid and the like. In particular, 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 it represents with the ratio of the mass sum occupied with respect to the preparation amount of all the monomers as hydroxycarboxylic acid, it is 20 to 99% normally, Preferably it is 30 to 95%, Most preferably, it is the range of 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 oxiranyl group, an oxetanyl group, and a vinyloxy group is preferable, and an oxetanyl group is particularly preferable. As a compound for introducing the structural unit (D), as shown in the following general formula, an aromatic compound having a phenolic hydroxyl group or a carboxyl group, a cationic polymerizability selected from an oxiranyl group, an oxetanyl group, and a vinyloxy group Is a compound having a functional group bonded thereto. 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 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. 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). 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.

  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 the form of sealing both ends of the molecule, 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:

  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 the 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, pentyl group, hexyl group, octyl group, nonyl Group, decyl 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 Group, a fluoro group or a carboxyl group, R ⁵ independently represents hydrogen, a methyl group or an ethyl group, R ⁶ represents a hydrocarbon group having 1 to 24 carbon atoms, and L ² represents Independently, it represents a single bond, —O—, —O—CO—, —CO—O—, —CH═CH— or —C≡C—, and p represents an integer of 1 to 10 Q represents an integer from 0 to 10, 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) Represents.

The molar ratio of each component constituting the side chain type polymer liquid crystalline compound represented by the formula (1) is a + b + c + d + e + f = 1.0, c + d + e ≠ 0, and it is necessary 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 has 2, 3, 4, 5, ⁶ , 7, 8, 10, 12 and 18 hydrocarbon groups are represented.

  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 the present invention, the photopolymerizable liquid crystal composition composed of the above-mentioned side chain polymer liquid crystal compound 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). In formulas (3) and (4), P ¹ represents a group independently selected from formula (5), and P ² represents a group selected from formula (5) or 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 photopolymerizable liquid crystal 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 crystal compound or the high molecular liquid crystal compound. It is a composition showing properties. 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.

  The photopolymerizable liquid crystal composition used in the present invention can 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 as described above. . 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 oxiranyl group, and a vinyloxy 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.

  The photopolymerizable liquid crystal composition having a reactive group is made to have a desired orientation by realizing a desired alignment and then performing a reaction under conditions suitable for reacting the reactive group, by crosslinking, increasing molecular weight, and the like. It can contribute to the improvement of the heat resistance and mechanical strength of the optical film.

  As said polymeric compound, the compound which can improve the workability and adhesiveness in the next processing process of the optical 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, the following compounds can be exemplified.

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 described in the synthesis of the compound represented by the general formula (2).

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.

  As the photo radical initiator, commercially available benzophenone derivatives, benzoin ethers, acylphosphine oxides, triazine derivatives used for general ultraviolet (UV) curable paints, UV curable adhesives, negative resists, etc., Examples thereof include bisimidazole derivatives and organic peroxide-amine systems. These may be used as a mixture, and if necessary, a compound having an amino group such as dimethylaminobenzoate may be added as a sensitizer.

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 ⁻ 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.

  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 photopolymerizable liquid crystal composition cannot be generally described because it varies depending on the structure of the mesogen portion and spacer portion constituting the liquid crystal compound used, the structure of the spacer portion, the molecular weight, the alignment conditions of the liquid crystal, etc. It is 100 mass ppm-20 mass% normally with respect to a liquid crystal compound, Preferably it is 1000 mass ppm-10 mass%, More preferably, it is the range of 0.5 mass%-8 mass%. If the amount is less than 100 mass ppm, the amount of active species generated from the reaction initiator is not sufficient, and the reaction may not proceed. If the amount is more than 20 mass%, the photopolymerizable liquid crystal composition contains This is not preferable because the decomposition residue of the reaction initiator remaining in the substrate increases and may be colored or light resistance may deteriorate.

  Hereinafter, a method for forming an aligned liquid crystal layer will be described, but the method for forming a liquid crystal layer is not limited thereto.

First, the photopolymerizable liquid crystal composition used in the present invention is developed on the alignment substrate.
Examples of the method for forming the liquid crystal layer by spreading the photopolymerizable liquid crystal composition on the alignment substrate include a method in which the photopolymerizable liquid crystal composition is directly applied on the alignment film substrate in a molten state, and a photopolymerizable liquid crystal composition. A method of drying the coating film and distilling off the solvent after the above solution is applied on the alignment substrate.

  The solvent used for preparing the solution is not particularly limited as long as it can dissolve various compounds used in the photopolymerizable liquid crystal composition of the present invention and can be distilled off under appropriate conditions. Generally, acetone, methyl ethyl ketone, Ketones such as isophorone and cyclohexanone, ether alcohols such as butoxyethyl alcohol, hexyloxyethyl alcohol, methoxy-2-propanol and benzyloxyethanol, glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, ethyl acetate, ethyl lactate, Esters such as γ-butyrolactone, phenols such as phenol and chlorophenol, amides such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone, 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 alignment substrate, a surfactant, an antifoaming agent, a leveling agent, or the like may be added to the solution.

  The method of directly applying the photopolymerizable liquid crystal composition or the method of applying a solution is not particularly limited as long as the coating method ensures the uniformity of the coating film. Can be adopted. 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 solution of the photopolymerizable liquid crystal composition, 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 thickness is not generally determined because it is adjusted depending on the photopolymerizable liquid crystal composition to be used, the use of the obtained liquid crystal layer, and the like, but is 0.1 to 20 μm, preferably 0. 3 to 10 μm. In addition, since the photopolymerizable liquid crystal composition in the present invention exhibits refractive index anisotropy by being oriented, it is not always sufficient to simply define the coating film thickness only by the film thickness. For example, in the case of a nematic alignment liquid crystal layer or a hybrid nematic alignment liquid crystal layer having an in-plane anisotropy, it is preferable to specify the in-plane retardation value Re (= refractive index anisotropy × actual film thickness: Δnd). There is also. The Re value at that time is in the range of 10 to 1000 nm, preferably 20 to 800 nm. If the film thickness and / or the Re value are out of this range, the desired effect cannot be obtained and the orientation becomes insufficient.

  In the case of a homeotropic alignment liquid crystal layer having anisotropy in the thickness direction, the refractive index in the in-plane direction is nx and ny (nx ≧ ny), the refractive index in the thickness direction is nz, and the thickness is d (nm). In some cases, it is preferable that the thickness is defined by a retardation value Rth in the thickness direction defined by Rth = ((nx + ny) / 2−nz) × d. The Rth value at that time is in the range of −1000 to −10 nm, preferably −600 to −20 nm. If the film thickness and / or Rth value is out of this range, the desired effect cannot be obtained and the orientation becomes insufficient.

  Subsequently, the liquid crystal layer formed on the alignment substrate is aligned with liquid crystal by heat treatment, and then the reactive group is reacted by irradiation with active light to fix the alignment. In the first heat treatment, the liquid crystal is aligned by the self-alignment ability inherent in the photopolymerizable liquid crystal composition by heating to a desired temperature within the liquid crystal phase expression temperature range of the used photopolymerizable liquid crystal composition. The conditions for the heat treatment cannot be generally stated because the optimum conditions and limit values differ depending on the liquid crystal phase behavior temperature (transition temperature) of the photopolymerizable liquid crystal composition to be used, but are usually 10 to 300 ° C., preferably 30 to 250 ° C. It is preferable to perform the heat treatment at a temperature in the range of ° C. and higher than the glass transition point (Tg) of the photopolymerizable liquid crystal composition, more preferably 20 ° 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 photopolymerizable 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. In addition, although heat processing is based on the phase transition temperature of the polymeric liquid crystal composition used, it can also be performed by heating to the temperature used as an isotropic phase, and maintaining in a liquid crystal phase temperature range.

  A cooling operation is performed after the heat treatment. Specifically, the alignment is maintained by taking out the substrate film including the aligned liquid crystal layer from the heat treatment atmosphere into an atmosphere of Tg or less of the photopolymerizable liquid crystal composition.

  After forming the alignment of the liquid crystal layer by the above method, the function of the reaction initiator contained in the photopolymerizable liquid crystal composition is expressed while maintaining the alignment state, and the reactive group is reacted to form a three-dimensional By forming a crosslinked structure, the orientation is fixed or the mechanical strength is improved.

  The reaction initiator exhibits the function of the initiator by irradiation with actinic rays. For example, UV is used as the actinic ray. As a method of UV irradiation, light from a light source such as a metal halide lamp, a (super) high pressure mercury lamp, a low pressure mercury lamp, a xenon lamp, an arc lamp, or a laser having a spectrum in the absorption wavelength region of the initiator used is irradiated. Activate the 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 photopolymerizable liquid crystal composition itself has the ability to absorb the light source wavelength. In these cases, an appropriate photosensitizer, or a mixture of two or more reaction initiators having different absorption wavelengths can be used. Moreover, the actinic ray irradiation source may be single or plural.

In order to exhibit the effect of the present invention, it is important to perform irradiation with the actinic ray under the following specific conditions.
In the present invention, when the substrate temperature immediately before receiving the actinic ray irradiation is T0 (° C.) and the maximum temperature of the substrate being irradiated is Tm (° C.), the activity is such that Tm−T0> 30 ° C. Irradiate light. In this way, the reaction of the reactive group in the photopolymerizable liquid crystal composition is promoted, the three-dimensional cross-linked structure becomes stronger, and an optical film excellent in heat resistance and mechanical strength can be obtained. It can be obtained with high production efficiency. The upper limit of Tm-T0 is preferably less than the isotropic phase transition temperature of the unreacted polymerizable liquid crystal composition, but is not always isotropic because the liquid crystallinity of the composition disappears as the crosslinking proceeds by irradiation. It need not be below the phase transition temperature.
The above substrate temperature refers to the temperature of the surface irradiated with actinic rays, and can be measured using a minute thermocouple or a radiation thermometer attached to the surface.

  In the present invention, the relationship between the temperature T0 (° C.) and the Tg (° C.) is preferably Tg−20 ° C. ≦ T0 ≦ Tg + 20 ° C. The lower limit of T0 is more preferably Tg−15 ° C. ≦ T0, and further preferably Tg−10 ° C. ≦ T0. The upper limit of T0 is more preferably T0 ≦ Tg + 15 ° C., and further preferably T0 ≦ Tg + 10 ° C. When T0 is less than (Tg−20 ° C.), there is a possibility that the crosslinking reaction of the photopolymerizable liquid crystal composition does not sufficiently proceed, and when T0 is higher than (Tg + 20 ° C.), the photopolymerizable liquid crystal composition. There is a possibility that the alignment order of the liquid crystal molecules inside is disturbed.

  In order to realize the conditions of T0 and Tm in the present invention, a heat treatment of the substrate film including the liquid crystal layer can be appropriately incorporated before or during the irradiation with the actinic ray. Specifically, it is possible to employ a dielectric heating drum or a hot water heating drum with high in-plane accuracy so that the surface of a long substrate film can be continuously and uniformly heated. If necessary, heating by radiant heat such as a far-infrared heater or control of the ambient temperature in the actinic ray irradiation apparatus can be used.

  The liquid crystal layer obtained by the method of the present invention becomes a sufficiently strong film. Specifically, the mesogen is three-dimensionally bonded by the crosslinking reaction, and not only the heat resistance (the upper limit temperature for maintaining the liquid crystal alignment) is improved as compared to before the crosslinking, but also the scratch resistance, wear resistance, and crack resistance. The mechanical strength such as is greatly improved. The present invention is industrially significant in that it provides a method that can easily control the precise alignment of liquid crystal alignment and simultaneously achieve the conflicting objectives of improving thermal and mechanical strength.

Next, the transfer process of the liquid crystal layer added as necessary will be described.
The alignment substrate is not optically isotropic, or is opaque in the final use wavelength region of the obtained liquid crystal layer, or the alignment substrate is too thick, causing trouble in actual use. When there is a problem, the substrate formed from the alignment substrate is different from the alignment substrate, for example, optically isotropic, or the obtained liquid crystal layer is finally transparent in the intended use wavelength region. Or a liquid crystal layer may be transferred to a base material such as a film for temporarily supporting until the liquid crystal layer is bonded to a liquid crystal cell substrate.

  As a transfer method, a known method can be adopted. For example, as described in JP-A-4-57017 and JP-A-5-333313, after laminating a base material different from the alignment substrate through a pressure-sensitive adhesive or adhesive, A method of transferring the liquid crystal layer by performing a curing treatment on the pressure-sensitive adhesive or the adhesive as necessary and peeling the alignment substrate from the laminate can be exemplified.

  Examples of the base material different from the alignment substrate include triacetyl cellulose films such as Fujitac (product of Fujifilm), Konicatak (product of Konica Minolta Opto), and TPX film (Mitsui Chemicals). Products), Arton Film (product of JSR Co., Ltd.), Zeonex Film (product of Nippon Zeon Co., Ltd.), Acryprene Film (product of Mitsubishi Rayon Co., Ltd.) and the like. Moreover, temporary support films, such as a polyethylene terephthalate film etc. which performed the silicone process or provided the easy peeling layer on the surface etc. are mentioned. Furthermore, if necessary, a film provided with a retardation function by stretching or the like, various retardation films including a liquid crystal alignment layer, a polarizing element, a polarizing plate, various glasses, and the like can be exemplified.

  Examples of the film provided with the retardation function include those obtained by uniaxially stretching or biaxially stretching a polymer film, and various retardation films including a liquid crystal alignment layer include coating / alignment films of liquid crystalline polymers. Can be mentioned.

  As the polymer film for uniaxial stretching or biaxial stretching, a polymer film having a smooth plane and high transmittance is preferable, and examples thereof include films and sheets made of organic polymer materials, such as polyvinyl alcohol, Polyimide, polyphenylene oxide, polyether ketone, polyether ether ketone, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polycarbonate polymers and polymethyl methacrylate The film which consists of transparent polymers, such as these, is mentioned. Also, styrene polymers such as polystyrene, acrylonitrile / styrene copolymer, olefin polymers such as polyethylene, polypropylene, polycycloolefin, ethylene / propylene copolymer, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide. A film made of a transparent polymer such as In addition, films made of transparent polymers such as sulfone polymers, polyether sulfone polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers, epoxy polymers and blends of the above polymers are also included. It is done.

  Among these, plastic films such as triacetyl cellulose, polycarbonate, and polycycloolefin that are used as optical films are used. Examples of the organic polymer film include ZEONOR (trade name, manufactured by ZEON CORPORATION), ZEONEX (trade name, manufactured by ZEON CORPORATION), Arton (trade name, manufactured by JSR Corporation), etc. A plastic film made of a polymer material having a cyclic structure is preferably used. A retardation film produced by a method of uniaxially or biaxially stretching the above-described film, a method of reducing the retardation in the stretching direction by a heat shrink film as disclosed in JP-A-5-157911, The polymer film described in Kai 2001-343529 also exhibits optically excellent characteristics. The polymer film may be, for example, an extruded product of the resin composition.

  There is no particular limitation on the pressure-sensitive adhesive or adhesive used for transfer (hereinafter sometimes referred to as “sticky / adhesive”) as long as it is of optical grade. For example, acrylic, epoxy resin, ethylene-vinyl acetate copolymer Various reactive types such as a system, a rubber system, a urethane system and a mixture system thereof, a thermosetting type and / or a photocurable type, and an electron beam curable type can be exemplified. 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 fixing the liquid crystal composition layer with light, and the irradiation amount may be the same. The acceleration voltage in the case of the electron beam-curing type is usually 10 kV to 200 kV. It is preferably 20 kV to 100 kV.

  The optical film of the present invention has an alignment structure of a liquid crystal layer included in the optical film by appropriately selecting the structure and ratio of each component in the photopolymerizable liquid crystal composition, the type of alignment film, and the manufacturing conditions. And / or the phase state can be controlled. As the alignment structure, homogeneous alignment, hybrid alignment, homeotropic alignment, and the like can be formed, and as the phase state, a nematic phase, a smectic phase, and the like can be formed, and each alignment structure and / or phase can be formed. It is possible to produce an optical film with a fixed state.

The optical film of the present invention can be suitably used as a λ / 2 film, a λ / 4 film, a color compensation film, a retardation film, a viewing angle improving film or the like for a liquid crystal display element.
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 birefringence). 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.

  The optical film of the present invention is applied to various uses depending on the alignment structure and / or phase structure of the liquid crystal layer contained therein. A film in which the liquid crystal layer takes a nematic phase or a nematic phase that is hybrid-aligned is particularly preferably used as a retardation film or a viewing angle improving film. For example, an optical film in which a nematic phase is fixed functions as a retardation film, and can be used as a compensation plate for STN-type, TN-type, OCB-type, HAN-type transmissive or reflective liquid crystal display devices. An optical film in which a smectic phase is fixed can be used as a diffraction film. An optical film in which a hybrid-oriented nematic phase is fixed can be used as a retardation film or a wave plate by using retardation when viewed from the front, and by utilizing the asymmetry of the viewing angle dependency of retardation, a TN type It can be used for a viewing angle improving film of a liquid crystal display device. In addition, the optical film in which homeotropic alignment is fixed can be used as a viewing angle improving film for VA type and IPS type liquid crystal display devices.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. The analysis methods used in Examples and Comparative Examples are described below.

(1) Measurement of solid content concentration The solid content concentration was measured using an ETAC oven HT310S. The obtained PVA composition solution was weighed on an aluminum tray and dried in air at 107 ° C for 3 hours. Obtained from mass loss.
(2) Measurement of molecular weight The molecular weight was measured by dissolving the compound in tetrahydrofuran, connecting TSK-GEL SuperH1000, SuperH2000, SuperH3000, and SuperH4000 in series with an 8020 GPC system manufactured by Tosoh Corporation and using tetrahydrofuran as an eluent. Polystyrene standards were used for molecular weight calibration.
(3) Observation of phase behavior The phase behavior was observed with a BH2 polarizing microscope manufactured by Olympus Optical Co., Ltd. while heating the sample on a hot stage FP82HT manufactured by Mettler.
The phase transition temperature was measured with a differential scanning calorimeter DSC7 manufactured by Perkin-Elmer. In the description of phase behavior, Nm represents a nematic phase, and Iso represents an isotropic liquid phase.
(4) Microscope observation The alignment state of the liquid crystal of the obtained optical film was observed with an Olympus BH2 polarizing microscope.
(5) Optical film parameter measurement The retardation value (Δnd) of the optical film and its light incident angle dependency are determined by using an automatic birefringence meter (KOBRA-21ADH) manufactured by Oji Scientific Instruments using light having a wavelength of 550 nm. Measured with
The substrate temperature at the time of ultraviolet (UV) irradiation was measured using a radiation thermometer.

[Reference Example 1]
(Preparation of PVA solution)
In a 500 L stainless steel tank equipped with a reflux condenser and a stirrer, PVA (trade name PVA-117H, manufactured by Kuraray Co., Ltd .: saponification degree 99.3% or more, average polymerization degree 1700) 16.00 kg and deionized water 307. 20 kg (electrical conductivity value: 1 μS / cm or less) was added, heated at 95 ° C. for 3 hours, dissolved by stirring, and then cooled to 70 ° C. Isopropyl alcohol 76.8 kg (Kanto Chemicals, deer grade 1 purity 99% or more) was gradually added and stirred at 65 ° C. to 70 ° C. for 2 hours to obtain a transparent homogeneous solution.
It cooled to room temperature and extracted, filtering the PVA solution from the said tank. Filtration is performed using a cartridge filter (ADVANTEC, TCP-JX-S1FE (1 μm)) capable of collecting particles having an average particle diameter of 1 μm at a filtration rate of 10 kg / min, and 350 kg of a solution having a solid content concentration of about 4% by mass is obtained. Obtained.

[Reference Example 2]
In the same manner as in Reference Example 1, a PVA solution was obtained using a product name JL-18E (saponification degree: 83-86%, average polymerization degree: 1800) manufactured by Nippon Vinegar Poval Co., Ltd.

[Reference Example 3]
(Preparation of photopolymerizable liquid crystal composition solution)
A photopolymerizable liquid crystal composition solution used for the production of the optical film was prepared as follows.
A side chain type liquid crystalline polymer represented by the following formula (10) 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. In addition, although following formula (10) is displayed with the form of a block copolymer, it represents the monomer composition ratio (molar ratio) at the time of superposition | polymerization.
160 g of this side chain type liquid crystalline polymer, 30 g of the dioxetane compound represented by the following formula (11), and 10 g of the acrylic compound represented by the following formula (12) were dissolved in 1800 ml of γ-butyrolactone, and in the dark. After adding 20 g of a triallylsulfonium hexafluoroantimonate 50% propylene carbonate solution (manufactured by Aldrich, reagent), the solution is filtered through a polytetrafluoroethylene filter having a pore size of 0.45 μm to obtain a photopolymerizable liquid crystal composition solution. Prepared.

[Example 1]
(Alignment film formation)
It was obtained in Reference Example 1 so that a dry film thickness was about 1 μm by a gravure coater at room temperature on a polyethylene naphthalate film (PEN: manufactured by Teijin DuPont Films Co., Ltd., trade name Q51) having a width of 650 mm and a length of 1000 m. The PVA solution was applied continuously. The coating film was continuously dried 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 (hereinafter referred to as an alignment substrate).

(Rubbing process)
With the apparatus shown in FIG. 1, a rubbing roll having a diameter of 150 mm in which a rubbing cloth is wound around the alignment film surface is set to 45 degrees with respect to the MD of the film while the alignment substrate obtained above is conveyed at a speed of 20 m / min. Then, the rubbing cloth was rubbed continuously by rotating the bristles at 500 rpm and rotating at 170 rpm (peripheral speed ratio 4), and wound on a roll.

(Manufacture of optical films)
The photopolymerizable liquid crystal composition solution obtained in Reference Example 3 was applied on the rubbing-treated alignment substrate using a roll coater so that the liquid crystal composition layer thickness after alignment / curing was about 1 μm. After drying at 60 ° C., heat treatment was performed at 130 ° C. for 2 minutes to orient the liquid crystal composition layer, and then it was taken out in a room temperature atmosphere.
Only the liquid crystal layer portion thus obtained was scraped from the alignment substrate, and the glass transition point (Tg) was measured using DSC. Further, from observation with a polarizing microscope on a hot stage, a nematic phase was developed at a temperature of Tg or higher, and the Nm-Iso transition temperature was 228 ° C.
Next, in an apparatus (hereinafter referred to as UV apparatus) that includes a high-pressure mercury lamp and a metal drum and can continuously irradiate UV from the liquid crystal layer side while holding the alignment substrate on the drum, the temperature T0 of the alignment substrate immediately before receiving UV irradiation is The atmospheric temperature in the apparatus and the drum temperature were adjusted so that the maximum temperature Tm of the alignment substrate during irradiation was 110 ° C. at 55 ° C. An alignment substrate having a liquid crystal layer was continuously introduced into this UV device, and 300 mJ / cm ² of UV was irradiated to fix the alignment of the liquid crystal layer.

Since the PEN film as the substrate shows optical anisotropy, the liquid crystal layer was transferred onto the triacetyl cellulose (TAC) film with an acrylic adhesive as follows.
A commercially available UV curable adhesive (UV-3400, manufactured by Toagosei Co., Ltd.) was applied as an adhesive layer on the liquid crystal layer of the alignment substrate having the obtained liquid crystal layer to a thickness of 5 μm, and a TAC film After laminating and curing the adhesive layer by irradiating UV from the TAC film side, the PEN film and the alignment film layer were peeled off to obtain an optical film (liquid crystal layer / adhesive layer / TAC film). .

[Example 2]
In Example 1, an optical film (liquid crystal layer / adhesive layer / TAC film) was obtained in the same manner as in Example 1 except that T0 was 70 ° C. and Tm was 115 ° C.

[Example 3]
An optical film (liquid crystal layer / adhesive layer / TAC film) was obtained in the same manner as in Example 1 except that T0 was 85 ° C. and Tm was 120 ° C. in Example 1.

[Example 4]
In Example 1, an optical film (liquid crystal) was formed in the same manner as in Example 1 except that the alignment film was formed using the PVA solution obtained in Reference Example 2 and the alignment film surface was not rubbed. Layer / adhesive layer / TAC film).

[Example 5]
In Example 4, an optical film (liquid crystal layer / adhesive layer / TAC film) was obtained in the same manner as in Example 4 except that T0 was set to 70 ° C. and Tm was set to 115 ° C.

[Example 6]
In Example 4, an optical film (liquid crystal layer / adhesive layer / TAC film) was obtained in the same manner as in Example 4 except that T0 was 85 ° C. and Tm was 120 ° C.

[Comparative Example 1]
In Example 1, an optical film (liquid crystal layer / adhesive layer / TAC film) was obtained in the same manner as in Example 1 except that T0 was 40 ° C. and Tm was 65 ° C.

[Comparative Example 2]
In Example 1, an optical film (liquid crystal layer / adhesive layer / TAC film) was obtained in the same manner as in Example 1 except that T0 was 70 ° C. and Tm was 90 ° C.

[Comparative Example 3]
In Example 1, an optical film (liquid crystal layer / adhesive layer / TAC film) was obtained in the same manner as in Example 1 except that T0 was set to 100 ° C. and Tm was set to 115 ° C.

[Comparative Example 4]
In Example 4, an optical film (liquid crystal layer / adhesive layer / TAC film) was obtained in the same manner as in Example 4 except that T0 was 40 ° C. and Tm was 65 ° C.

[Comparative Example 5]
In Example 4, an optical film (liquid crystal layer / adhesive layer / TAC film) was obtained in the same manner as in Example 4 except that T0 was 70 ° C. and Tm was 90 ° C.

[Comparative Example 6]
In Example 4, an optical film (liquid crystal layer / adhesive layer / TAC film) was obtained in the same manner as in Example 4 except that T0 was set to 100 ° C. and Tm was set to 115 ° C.

About the optical film obtained in Examples 1-6 and Comparative Examples 1-6, the orientation state and the heat resistance after making it pass in a 90 degreeC thermostat for 500 hours were evaluated.
The homogenous alignment state indicates that there is no disclination or unevenness in the monodomain when the optical film is observed under a crossed Nicols polarizing microscope, and the extinction position is obtained when the rubbing axis is aligned with either the upper or lower polarizer. It was confirmed that light transmission was observed in other cases.
In the hybrid alignment state, there is no disclination or unevenness in the mono domain when the optical film is observed under a crossed Nicols polarizing microscope, and the light incident angle dependence of Δnd is measured along the rubbing axis. It was confirmed that there is no angle at which the value becomes 0 nm, and that the dependence of Δnd on the light incident angle is asymmetric.
The homeotropic alignment state is that there is no disclination or unevenness in the monodomain when the optical film is observed under a crossed Nicols polarizing microscope, and the value is approximately 0 nm when Δnd from the front is measured. Moreover, it confirmed by observing a positive uniaxial refractive index structure with a conoscope.
The results are shown in Table 1.

[Example 7]
(Production of elliptically polarizing plate)
On the liquid crystal layer of the alignment substrate having the liquid crystal layer obtained in Example 3, a commercially available UV curable adhesive (UV-3400, manufactured by Toagosei Co., Ltd.) was applied as an adhesive layer to a thickness of 5 μm. Then, after laminating a ZEONOR film having an in-plane retardation of 140 nm and irradiating UV light from the ZEONOR film side to cure the adhesive layer, the PEN film and the alignment film layer were peeled off to form a homeotropic alignment liquid crystal layer / adhesion A laminate comprising an agent layer / zeonore film was obtained.
The homeotropic alignment liquid crystal layer side of the obtained laminate and the polarizing element side of the polarizing plate whose one surface was protected with a TAC film were bonded together with an adhesive to obtain an elliptically polarizing plate.
(Production of IPS liquid crystal display device)
Instead of the viewing side polarizing plate of a commercially available IPS type liquid crystal television arranged in the order of the backlight, the backlight side polarizing plate, the IPS type liquid crystal cell, and the viewing side polarizing plate, the above elliptical polarizing plate was arranged. Then, compared with the case where this elliptically polarizing plate is not used, it turned out that a viewing angle expands and a favorable image is obtained even if it sees from diagonally.

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

Explanation of symbols

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

Claims (8)

  It includes a step of applying a photopolymerizable liquid crystal composition on a substrate, aligning it by heat treatment, and fixing the alignment state by irradiation with actinic rays, and setting the substrate temperature just before receiving the actinic rays to T0 (° C.) The method for producing an optical film, wherein Tm−T0> 30 ° C., where Tm (° C.) is the maximum temperature of the substrate being irradiated.   2. The method for producing an optical film according to claim 1, wherein Tg−20 ° C. ≦ T0 ≦ Tg + 20 ° C. when the glass transition point of the photopolymerizable liquid crystal composition is Tg (° C.).   The method for producing an optical film according to claim 1 or 2, wherein the photopolymerizable liquid crystal composition contains at least a side-chain polymer liquid crystal compound having a cationic polymerizable group.   The method for producing an optical film according to claim 1, wherein an alignment film is provided on the substrate.   The method for producing an optical film according to claim 1, further comprising a step of transferring the liquid crystal layer in which the alignment state is fixed onto a base material different from the substrate.   The method for producing an optical film according to claim 1, wherein the alignment state is homogeneous alignment, hybrid alignment, or homeotropic alignment.   The optical film manufactured by the manufacturing method in any one of Claims 1-6.   A liquid crystal display device using the optical film according to claim 7.

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