KR102340163B1 - Method of manufacturing optical film, and optical film - Google Patents

Abstract

(Problem) To provide a method for producing an optical film that can dry the solvent in a short time, wrinkle is less likely to occur on the film during transport, and is excellent in productivity, and provides an optical film with few wrinkles and excellent dimensional stability to do.
(Solution Means) As a method for manufacturing an optical film by solution film forming, a dope composition containing a polymer and a solvent is cast on a support to form a cast film, and a step (1) of drying the solvent to the total solid content of the cast film The content of the solvent for the solvent is peeled off from the support within the range of 5 to 60 mass%, the step (2) of gripping both ends in the width direction of the stripped cast film with a tenter, the gripped cast film, an optical film With respect to the glass transition temperature Tg of Tg-30 degreeC - Tg+20 degreeC at the temperature of Tg-30 degreeC - Tg+60 degreeC with respect to the glass transition temperature Tg of an optical film, Tg+60 degreeC- A method for producing an optical film comprising the step (4) of obtaining an optical film by heat treatment at a temperature of Tg+120°C in this order, and an optical film obtained by this method.

Description

The manufacturing method of an optical film, and an optical film TECHNICAL FIELD

The present invention relates to a method of manufacturing an optical film, and to an optical film.

Demand for liquid crystal display devices is expanding in applications such as liquid crystal televisions and liquid crystal displays of personal computers. Usually, a liquid crystal display device consists of a liquid crystal cell with a transparent electrode, a liquid crystal layer, a color filter, etc. sandwiched between glass plates, and two polarizing plates formed on both sides thereof, and each polarizing plate has a polarizer (also called a polarizing film or a polarizing film). It consists of a structure placed between two optical films (polarizer protective film). As a material of the optical film, various polymers are used, for example, an acrylic resin such as polymethyl methacrylate (also referred to as PMMA) is used.

On the other hand, as a film forming method of an optical film, the solution film forming method is used in a wide range of fields as a manufacturing method of various optical films, such as a polarizing plate protective film and retardation film, since it is excellent in thickness nonuniformity and surface smoothness of the film obtained. The solution film forming method is a film forming method which casts a dope composition containing a polymer and a solvent on a support body, forms a cast film, and forms a film through the process of drying a solvent, etc.

Patent Document 1 describes a method for obtaining an optical film by drying the film at high temperature and then stretching it as a manufacturing method by a solution film forming method of an optical film using an acrylic resin. Moreover, also in the special documents 2 and 3, the method of drying an acrylic resin film at high temperature to obtain an optical film is described.

Japanese Patent Laid-Open No. 2007-118266 International Publication No. 2009/150926 Japanese Patent Laid-Open No. 2014-38180

However, in the manufacturing method of the optical film by the solution film forming method of patent documents 1-3, although a solvent can be dried in a short time, the fall of productivity by generation|occurrence|production of wrinkles in a film during conveyance was a problem. Moreover, the dimensional stability of the obtained optical film also had room for improvement.

The subject of this invention is providing the manufacturing method of the optical film which can dry a solvent in a short time, a wrinkle does not generate|occur|produce in a film easily during conveyance, and is excellent in productivity. Moreover, the other subject of this invention is providing the optical film excellent in dimensional stability with few wrinkles.

The said subject is solved by the following means.

<1>

A method for producing an optical film by solution film forming, comprising:

Step (1) of casting a dope composition containing a polymer and a solvent on a support to form a cast film, and drying the solvent;

Step (2) of peeling off the cast film from the support within the range of 5 to 60 mass% of the content of the solvent with respect to the total solid content of the cast film, and holding both ends of the cast film in the width direction of the stripped off with a tenter (2),

Process (3) of shrink|contracting the said hold|gripped cast film to 97% - 70% in the width direction at the temperature of Tg-30 degreeC - Tg+20 degreeC with respect to the glass transition temperature Tg of an optical film (3), and

The manufacturing method of the optical film containing the process (4) which heat-processes the said cast film at the temperature of Tg+60 degreeC - Tg+120 degreeC with respect to the glass transition temperature Tg of an optical film, and obtains an optical film in this order.

<2>

After the step (4), further,

Tg+10°C to Tg+100°C with respect to the glass transition temperature Tg of the optical film, further including a step (5) of stretching the optical film to 105% to 300% in the width direction at a temperature lower than the heat treatment temperature in the step (4) The manufacturing method of the optical film as described in <1> to do.

<3>

The manufacturing method of the optical film as described in <1> or <2> in which the said polymer contains (meth)acrylic-type resin.

<4>

The manufacturing method of the optical film in any one of <1>-<3> in which the said dope composition contains the rubber elastic particle in the ratio of 1-50 mass parts with respect to 100 mass parts of said polymers.

<5>

The optical film manufactured by the manufacturing method of the optical film in any one of <1>-<4>.

ADVANTAGE OF THE INVENTION According to this invention, a solvent can be dried in a short time, and wrinkles do not generate|occur|produce in a film easily during conveyance, and the manufacturing method of the optical film excellent in productivity can be provided. Moreover, according to this invention, there are few wrinkles and the optical film excellent in dimensional stability can be provided.

Hereinafter, the content of the present invention will be described in detail. Although the description of the components described below may be made based on the representative embodiment of this invention, this invention is not limited to such an embodiment. In addition, in this specification, "-" is used in the meaning which includes the numerical value described before and after that as a lower limit and an upper limit.

<Method for producing optical film>

The manufacturing method of the optical film of this invention,

A method for producing an optical film by solution film forming, comprising:

Step (1) of casting a dope composition containing a polymer and a solvent on a support to form a cast film, and drying the solvent;

Step (2) of peeling off the cast film from the support within the range of 5 to 60 mass% of the content of the solvent with respect to the total solid content of the cast film, and holding both ends of the cast film in the width direction of the stripped off with a tenter (2),

Process (3) of shrink|contracting the said hold|gripped cast film to 97% - 70% in the width direction at the temperature of Tg-30 degreeC - Tg+20 degreeC with respect to the glass transition temperature Tg of an optical film (3), and

It is a manufacturing method of the optical film containing the process (4) of which heat-processes the said cast film at the temperature of Tg+60 degreeC - Tg+120 degreeC with respect to the glass transition temperature Tg of an optical film, and obtains an optical film in this order, in this order.

Hereinafter, the present invention will be described in detail.

<Dope composition>

A dope composition is a composition containing a polymer and a solvent at least.

<Polymer>

As a polymer, (meth)acrylic-type resin, polycarbonate-type resin, polystyrene-type resin, and cyclic polyolefin-type resin are preferable, and it can also select from these resin and mixed resin of these multiple types of resin.

In addition, (meth)acrylic-type resin is a concept containing both a methacryl-type resin and an acrylic resin. Moreover, the (meth)acrylic-type resin also contains the derivative of acrylate/methacrylate, especially the (co)polymer of acrylate ester/methacrylate ester.

The polymer preferably contains (meth)acrylic resin, more preferably 30 to 100% by mass of (meth)acrylic resin, based on the total solid content of the polymer, and more preferably 60 to 100% by mass of (meth)acrylic resin It is more preferable to contain, and it is especially preferable to consist of 100 mass % of (meth)acrylic-type resin.

<(meth)acrylic resin>

[Structural unit of (meth)acrylic resin]

It is preferable that the (meth)acrylic resin contains the methyl methacrylate unit (a), and may be comprised only with the methyl methacrylate unit (a), and alkyl (meth)acrylate units other than methyl methacrylate (b) may be included. However, when (meth)acrylic-type resin contains alkyl (meth)acrylate units (b) other than methyl methacrylate, it is preferable that the ratio is less than 5 mass %. The (meth)acrylic resin may be a homopolymer of methyl methacrylate without using another copolymerizable monomer.

When (meth)acrylic-type resin contains alkyl (meth)acrylate units (b) other than methyl methacrylate, the following are mentioned as this alkyl (meth)acrylate unit (b).

(Alkyl (meth) acrylate units other than methyl methacrylate (b))

As the alkyl (meth)acrylate unit (b) other than the above-mentioned methyl methacrylate, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2- Acrylic acid esters, such as ethylhexyl acrylate, cyclohexyl acrylate, and benzyl acrylate (Preferably C1-C18 alkyl acrylate of alkyl number); Methacrylic acid esters such as ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate (preferably C2-C18 alkyl methacrylate); etc. are mentioned, These may use only 1 type, and may use 2 or more types together.

(Other units of construction)

(meth)acrylic resin may also contain structural units other than alkyl (meth)acrylate units (a) and (b). Examples of such structural units include α,β-unsaturated acids such as acrylic acid and methacrylic acid, unsaturated group-containing divalent carboxylic acids such as maleic acid, fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene; and α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide, N-substituted maleimide, and glutaric anhydride. On the other hand, the cellulosic resin is not included as another structural unit.

These structural units may be introduce|transduced into (meth)acrylic-type resin individually by 1 type, and may be introduce|transduced into (meth)acrylic-type resin in combination of 2 or more types.

Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. An acrylate and n-butyl acrylate are used especially preferably.

(Mass fraction of methyl methacrylate unit (a))

It is most preferable that (meth)acrylic-type resin is comprised with the methyl methacrylate unit (a) independently from a viewpoint of raising a glass transition temperature and obtaining heat resistance. On the other hand, when the (meth)acrylic resin is a copolymer of the methyl methacrylate unit (a) and another structural unit, properties other than those expressed by the methyl methacrylate unit (a) can be imparted to the acrylic resin. have.

In the above-mentioned (meth)acrylic resin, the content ratio of methyl methacrylate in the monomer component to be used in the polymerization step is preferably 95 to 100 mass%, more preferably 97 to sufficiently exhibit the effects of the present invention. - 100 mass %, More preferably, it is 100 mass %.

By making the ratio of methyl methacrylate into 95 mass % or more, an acrylic resin with high heat resistance can be obtained and the heat resistance of an optical film can be improved.

Moreover, it is preferable that the above-mentioned acrylic resin contains a methyl methacrylate unit (a), and it is preferable that the mass fraction of alkyl (meth)acrylate units (b) other than methyl methacrylate is less than 5 mass %, and 3 mass % It is more preferable that it is less than, and it is especially preferable that it is 0 mass %.

(Method for producing (meth)acrylic resin)

The (meth)acrylic resin which can be used for this invention can be obtained by a commercial item or a well-known synthesis method.

As a manufacturing method of the (meth)acrylic-type resin which can be used for this invention, emulsion polymerization, solution polymerization, block polymerization, and suspension polymerization are applicable. Among these, emulsion polymerization and suspension polymerization are more preferable in producing the high molecular weight substance of the present invention.

As the initiator of suspension polymerization, those used for conventional suspension polymerization can be used, and organic peroxides and azo compounds are exemplified.

As the suspension stabilizer, commonly used known ones can be used, and examples thereof include organic colloidal polymer substances, inorganic colloidal polymer substances, inorganic fine particles, and combinations of these and surfactants.

The (meth)acrylic resin contains a methyl methacrylate unit (a), the mass fraction of the alkyl (meth)acrylate unit (b) other than methyl methacrylate is less than 5 mass%, and the weight average molecular weight is 250,000 It is -4 million, and it is preferable that the weight loss at the time of heating at 140 degreeC for 1 hour is 0.5 % or less. In the acrylic resin having the composition of such a structural unit, in order to make the high weight average molecular weight and suppression of a weight loss compatible, it is preferable to implement the following method especially at the time of the synthesis|combination of an acrylic resin.

As a preferred method to be included in the synthesis of (meth)acrylic resin, after obtaining (meth)acrylic resin by polymerization reaction, the reaction solution is filtered in a suspension state with a filter cloth, washed with methanol, and then the filtrate is dried method can be found. As a filter cloth, a nylon filter cloth is mentioned, for example. By not drying the reaction solution as it is after obtaining the (meth)acrylic resin by polymerization reaction, an excess polymerization initiator, etc. can be removed, and a (meth)acrylic resin that achieves both a high weight average molecular weight and suppression of weight loss can be obtained. have.

[Weight average molecular weight of (meth)acrylic resin]

In this invention, a "weight average molecular weight" is a weight average molecular weight measured by gel permeation chromatography.

It is preferable that the weight average molecular weights of (meth)acrylic-type resin are 250,000-4 million, It is more preferable that it is 600,000-4 million, It is still more preferable that it is 800,000-3 million, It is especially preferable that it is 1 million-2 million. When the (meth)acrylic resin has a weight average molecular weight of 250,000 or more, for example, when an optical film is manufactured by a solution film forming method, a solution (dope) having a relatively high viscosity can be obtained even if the concentration of the (meth)acrylic resin is lowered. can As a result, it is suppressed that a stripe|streak arises on the surface at the time of discharge of dope from a casting die, and the film with a favorable surface shape can be obtained. Moreover, by making resin density|concentration of dope low (increasing the ratio of a solvent), a solvent component remains in the film after drying, and the effect that peeling of the film from a support body can be performed easily is acquired. On the other hand, since the weight average molecular weight of the (meth)acrylic resin is 4 million or less, there is an advantage that the (meth)acrylic resin can be easily synthesized or obtained.

Here, the "weight average molecular weight (Mw)" in this invention can be measured under the conditions described in [Measuring method] of an Example. Specifically, it is as follows.

It is a weight average molecular weight measured by the following conditions by gel permeation chromatography.

Solvent tetrahydrofuran

Device Name TOSOH HLC-8220GPC

Three columns of TOSOH TSKgel Super HZM-H (4.6 mm × 15 cm) were connected and used.

Column temperature 25℃

Sample concentration 0.1% by mass

flow rate 0.35 ml/min

Calibration curve TOSOH manufactured TSK standard polystyrene Mw = The calibration curve by 7 samples from 2800000 to 1050 is used.

<Cellulose Ester Resin>

As a polymer, you may make it contain cellulose-ester resin from a transparency viewpoint at the time of especially a brittle improvement and heat resistance improvement, and also (meth)acrylic-type resin and mixing by extension. As for the ratio of (meth)acrylic-type resin and the cellulose-ester resin to mix, 40 mass % or less is preferable with respect to total solid. Moreover, as for cellulose-ester resin, it is preferable that the total substitution degree (T) of an acyl group is 2.0-3.0, and it is preferable that the substitution degree of a C3-C7 acyl group is 1.2-3.0. That is, the cellulose ester resin is a cellulose ester resin substituted with an acyl group having 3 to 7 carbon atoms, and specifically, propionyl, butyryl, etc. are preferably used, but a propionyl group is particularly preferably used.

As for the acyl substitution degree of cellulose ester resin, it is preferable that total substitution degree (T) is 2.0-3.0, it is preferable that the substitution degree of a C3-C7 acyl group is 1.2-3.0, C3-C7 acyl group other than That is, it is more preferable that the total of substitution degrees of an acetyl group or a C8 or more acyl group becomes 1.3 or less.

In this application, "acyl group" is a meaning including what has a substituent further. However, carbon number of an acyl group includes the substituent of an acyl group.

When cellulose-ester resin has an aromatic acyl group as a substituent, it is preferable that the number of the substituents X substituted by an aromatic ring is 0-5. Also in this case, care must be taken so that the substitution degree of a C3-C7 acyl group including a substituent may be set to 1.2-3.0. For example, since a benzyl group becomes carbon number 7, when it has a substituent containing carbon, carbon number as a benzyl group becomes 8 or more, and a C3-C7 acyl group does not contain it.

In addition, when the number of substituents substituted with an aromatic ring is two or more, they may be the same or different from each other, but they may be connected to each other to form a condensed polycyclic compound (eg, naphthalene, indene, indane, phenanthrene, quinoline, isoquinoline, chromene). , chroman, phthalazine, acridine, indole, indoline, etc.) may be formed.

In cellulose-ester resin, it is preferable to have a structure which has at least 1 type of a substituted or unsubstituted C3-C7 aliphatic acyl group.

As for the substitution degree of cellulose-ester resin, it is preferable that total substitution degree (T) of an acyl group is 2.00-3.00, and it is preferable that the substitution degree of a C3-C7 acyl group is 1.2-3.0.

Moreover, it is a preferable structure that the total of substitution degree of acetyl groups other than a C3-C7 acyl group, ie, an acetyl group, and a C8 or more acyl group is 1.3 or less.

The cellulose ester resin is preferably at least one selected from cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate and cellulose butyrate, and particularly cellulose acetate propionate and cellulose propionate. Cypionate is more preferred.

Among these, particularly preferable cellulose ester resin is cellulose acetate propionate or cellulose acetate butyrate, and it is preferable to have an acyl group having 3 or 4 carbon atoms as a substituent.

The part not substituted with the acyl group exists as a hydroxyl group normally. These can be synthesized by a known method.

In addition, the substitution degree of an acetyl group and the substitution degree of another acyl group are calculated|required by the method prescribed|regulated to ASTM-D817-96.

The weight average molecular weight (Mw) of the cellulose ester resin is, in particular, from the viewpoint of compatibility with (meth)acrylic resin and improvement of brittleness, is 75000 or more, preferably in the range of 75000 to 300000, more preferably in the range of 100000 to 240000 It is preferable, and it is especially preferable that it is 160000-240000.

<Additives>

The additive may be added to the dope composition of this invention in the range which does not impair the effect by this invention.

As an additive, a plasticizer, a ultraviolet absorber, antioxidant, a brittleness improving agent, an optical expression agent, rubber elastic particle, etc. can be added.

A plasticizer has a function which improves the fluidity|liquidity and softness|flexibility of the dope composition used when manufacturing an optical film. As a plasticizer, a phthalic acid ester type, a fatty acid ester type, a trimellitic acid ester type, a phosphoric acid ester type, a polyester type, an epoxy type, etc. are mentioned.

As a ultraviolet absorber, the thing of a benzotriazole type, 2-hydroxybenzophenone type, or a salicylic acid phenyl ester type|system|group, etc. are mentioned. For example, 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole , 2-(3,5-di-t-butyl-2-hydroxyphenyl) triazoles such as benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzo Benzophenones, such as phenone and 2,2'- dihydroxy-4- methoxybenzophenone, etc. are preferable.

Moreover, in order to improve the thermal decomposition property and thermal coloring property at the time of a molding process, various antioxidants, a brittleness improving agent, an optical expression agent, rubber elastic particles, etc. can be added as an additive.

<Rubber Elastic Particles>

In order to improve especially brittleness and impact resistance in the dope composition in this invention, it is preferable to contain rubber elastic particle.

That is, in the manufacturing method of the optical film of this invention, it is preferable that a dope composition contains the rubber elastic particle in the ratio of 1-50 mass parts with respect to 100 mass parts of polymer, It is more preferable to contain it in the ratio of 3-40 mass parts. It is preferable, and it is more preferable to contain in the ratio of 5-30 mass parts. A sufficient improvement effect can be acquired with respect to brittleness and impact resistance that addition amount is 1 mass part or more, and transparency of an optical film is not impaired as it is 50 mass parts or less.

As the rubber elastic particles, commercially available ones can be used, for example, Metablen W-341 (C2) manufactured by Rayon Mitsubishi, “Kaneace” manufactured by Kanegafuchi Chemical Industries, Ltd., “Pararoid” manufactured by Kureha Chemical Industries, Ltd., ROM & & "Acryloid" manufactured by Haas, "Starpyroid" manufactured by Gantz Chemical Industries, Ltd., and "Parapet SA" manufactured by Kuraray, etc. are mentioned, These can be used individually or 2 or more types.

The particle diameter of the rubber elastic particles preferably used in the present invention is not particularly limited, but is preferably 10 nm or more and 10 µm or less, more preferably 20 nm or more and 1 µm or less, and particularly 50 nm or more and 400 It is most preferred that it is less than or equal to nm.

(menstruum)

As a solvent contained in a dope composition, an organic solvent is preferable.

The organic solvent can be used without limitation as long as it dissolves the polymer and an additive added as needed.

For example, as a chlorine-based organic solvent, methylene chloride, as a non-chlorine-based organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2 -Propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2 , 3,3,3-pentafluoro-1-propanol, nitroethane, etc. are mentioned, and methylene chloride, methyl acetate, ethyl acetate, acetone, and methyl ethyl ketone can be preferably used.

It is preferable to make dope composition contain a C1-C4 linear or branched aliphatic alcohol of 1-40 mass % other than the said organic solvent. When the ratio of alcohol in the dope composition becomes high, peeling from a metal support becomes easy, and when there is little ratio of alcohol, it also has a role which accelerates|stimulates the melt|dissolution of the polymer in a non-chlorine type organic solvent system.

In the present invention, when a plurality of solvents are used, the one having the highest weight ratio among them may be expressed as the main solvent.

Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, isopropanol, n-butanol, s-butanol and t-butanol. Among these, stability of a dope composition and a boiling point are also comparatively low, and methanol is preferable at the point from which drying property is also favorable.

Preparation of dope composition (dissolution process)

At a dissolution process, a polymer, an organic solvent, and the additive added as needed are mixed and stirred, and a dope composition is prepared.

A dope composition can be prepared by the general method which consists of processing at the temperature (normal temperature or high temperature) of 0 degreeC or more. Preparation of the dope composition of this invention can be performed using the preparation method and apparatus of the dope composition in a normal solvent casting method. In addition, in the case of the general method, halogenated hydrocarbons (especially dichloromethane) and alcohols (especially methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol) as organic solvents , 2-methyl-2-butanol and cyclohexanol).

It is preferable that content of the polymer in a dope composition is 10-50 mass %, It is more preferable that it is 10-40 mass %, It is still more preferable that it is 10-35 mass %. In an organic solvent (main solvent), you may add the arbitrary additives mentioned later.

A dope composition can be prepared by stirring a polymer, an organic solvent, and an additive as needed. At this time, the mixture of each component may be added and dissolved in the solvent during stirring, or each component may be sequentially added and dissolved in the solvent during stirring, or a dope composition is formed by preparing a solution of each component in advance and mixing these solutions, also be Polymer dissolution is performed under normal pressure, at or below the boiling point of the main solvent, by pressurizing above the boiling point of the main solvent, Japanese Patent Application Laid-Open No. 9-95544, Japanese Unexamined Patent Application Publication No. Hei 9-95557 A variety of dissolution methods can be used, such as a method carried out by a cooling melting method as described in Japanese Patent Application Laid-Open No. Hei 9-95538 or a method carried out by a high pressure method as described in Japanese Patent Application Laid-Open No. Hei 11-21379, In particular, a method of carrying out under pressure at a temperature equal to or higher than the boiling point of the main solvent is preferable.

The container which prepares a dope composition needs to be comprised so that it can stir. Moreover, it is preferable that this container can be pressurized by injecting inert gas, such as nitrogen gas. Moreover, you may use the raise of the vapor pressure of the solvent by heating. Or, after sealing a container, you may add each component under pressure.

When heating, it is preferable to heat from the outside of a container. For example, a jacket-type heating device can be used. Moreover, the whole container can also be heated by providing a plate heater on the exterior of a container, piping and circulating a liquid.

It is preferable to form a stirring blade inside a container, and to stir using this. It is preferable that the stirring blades have a length reaching the vicinity of the wall of the vessel. In order to renew the liquid film on the wall of a container, it is preferable to form a scraping blade|wing at the end of a stirring blade.

You may install instruments, such as a pressure gauge and a thermometer, in a container. Each component is dissolved in a solvent in a container. The prepared dope composition is taken out from the container after cooling, or after being taken out, it is cooled using a heat exchanger etc.

As mentioned above, the manufacturing method of the optical film of this invention has process (1)-(4) in this order, process (1) is a casting process, process (2) is a peeling process, process (3), respectively The preheating process and the process (4) are called a heat treatment process. Moreover, you may have a process (5) after a process (4), and a process (5) is called an extending process.

Process (1) flexible process

In the manufacturing method of this invention, a casting process is provided.

At a casting process, the dope composition prepared by the dissolution process is cast|flow_spread on a support body, it is set as a film|membrane, this is dried and a cast film is formed. In this casting process, the dope composition is liquid-fed to a pressurization die via a liquid feeding pump (for example, a pressurization type fixed-distance gear pump), and an endless metal belt (for example, a stainless steel belt, a rotating metal drum, etc.) It is preferable that it is a process of casting|flow_spreading a dope composition from a press die slit to the casting position on supports, such as metal support body) or a process film. As the die, a pressure die capable of adjusting the slit shape of the clasp of the die and making the film thickness uniform is preferable. The pressure die includes a coat hanger die, a T die, and the like, and all of them are preferably used. The surface of the metal support is made of a mirror surface. In order to raise a film forming rate, two or more press dies may be formed on a metal support body, and it is good also as an intermediate|middle layer by dividing|segmenting the dope composition amount. Or it is also preferable to obtain the cast film of a laminated structure by the co-spreading method which casts a some dope composition simultaneously.

When cast|flow_spreading a dope composition, simultaneous lamination|stacking co-spanning or sequential lamination|stacking co-spreading of two or more types of dope composition can also be carried out. In addition, you may combine these two common transmissions. When performing simultaneous lamination|stacking co-spanning, the casting die to which the feed block was attached may be used, and a multi-manifold type casting die may be used. As for the film which consists of a multilayer by co-spanning, it is preferable that at least either one of the layer thickness on the side of an air side and the layer thickness on the side of a support is 0.5 % - 30 % of the film thickness of the whole film. Moreover, when performing simultaneous lamination|stacking co-spreading, when casting|flow_spreading a dope composition from a die slit to a support body, it is preferable that a high-viscosity dope composition is covered with a low-viscosity dope composition.

In this casting process, you may perform common casting sequentially.

Structures such as casting die, decompression chamber, support, co-spanning, peeling method, stretching, drying conditions for each step, handling method, curling method, winding method after flatness correction, solvent recovery method, film recovery method JP 2005- 104148, in paragraphs [0617] through [0889].

When an optical film is produced by unstretching, it is preferable to carry out the casting conditions of this invention on the conditions used as the film thickness of an optical film will be 10-80 micrometers, It is more preferable to set it as the conditions used as 15-40 micrometers. do. In a film thickness thinner than this range, the intensity|strength of a cast film falls and workability deteriorates. On the other hand, in the film thickness thicker than this range, a solvent may remain|survive in an optical film.

Next, the cast film thus obtained is dried. In that case, it heats on a cast film metal support body, and evaporates a solvent until a cast film becomes peelable from a metal support body normally. In order to evaporate the solvent, there are a method of blowing air to the cast film side and/or a method of transferring heat with a liquid from the back surface of the metal support, a method of transferring heat from the front and the back by radiant heat, etc., but the method of liquid heat transfer on the back has good drying efficiency so it is preferable Moreover, the method of combining them is also preferable. In the case of backside liquid heat transfer, it is preferable to heat below the boiling point of the main organic solvent used for the dope composition, or the organic solvent which has the lowest boiling point.

Process (2) Peeling process

In the manufacturing method of this invention, a peeling process is provided.

At a peeling process, the cast film formed in the casting process is peeled from a support body. The peeled cast film is sent to a preheating process. Although the amount of residual solvent at the time of peeling of the cast film on a support body is set according to drying conditions, the length of a support body, etc., in this invention, it peels in 5-60 mass %. Furthermore, it is preferable to peel in the range of 10-40 mass %. Here, the amount of residual solvent is content of the solvent with respect to the total solid of a cast film, as shown by a following formula.

Residual solvent amount (mass %) = [(M-N)/N] × 100

Here, M is the mass at the arbitrary time point of a cast film, and N is the mass when the thing of mass M is dried at 130 degreeC for 3 hours.

In this invention, it is preferable to set the temperature in the peeling position on this metal support body to -50-40 degreeC, It is more preferable to set it as 0-40 degreeC, It is most preferable to set it as 10 to 30 %.

Process (3) Preheating process

In the manufacturing method of this invention, a preheating process is provided.

After a peeling process, it is preferable to heat a cast film in a preheating process using the tenter apparatus which hold|gripped and conveys the both ends of a cast film. As the heating means, it is common to apply hot air to both sides of the polymer film, but there is also a means for heating by applying microwaves instead of wind.

The surface temperature of the film in the preheating step is preferably Tg-30°C to Tg+20°C of the optical film, more preferably Tg-20 to Tg+10°C, and particularly preferably Tg-10 to Tg+5°C. Moreover, in a preheating process, the width direction of a film is contracted to 97 % - 70 % by adjusting the space|interval of the clip which clamps the film both ends. It is more preferable to shrink to 95% to 75%, and it is still more preferable to shrink to 90% to 80%.

Here, the shrinkage rate means being calculated|required by the following formula|equation.

Shrinkage percentage (%) = 100 × width after shrinkage/width before shrinkage

By providing such a preheating process, the film excellent in dimensional stability can be obtained. Moreover, there is little generation|occurrence|production of a wrinkle, and a favorable flat film and a favorable roll film of the wound form can be obtained.

Process (4) heat treatment process

In the manufacturing method of the present invention, a heat treatment step is provided as a subsequent step of the preheat treatment step.

The surface temperature of the cast film in the heat treatment step performed after the preheating step is preferably in the range of Tg+60°C to Tg+120°C with respect to the glass transition temperature (Tg) of the optical film, and Tg+70 to Tg+100°C of the optical film is in the range more preferably. By setting the heat treatment temperature within this range, drying of the solvent can be sufficiently performed, a cast film and an optical film excellent in dimensional stability can be manufactured, and furthermore, the transportability of the cast film is excellent.

In addition, the heat treatment is preferably performed for 10 seconds or longer. By setting the treatment time within this range, the solvent can be sufficiently dried, and a cast film and an optical film having excellent dimensional stability can be manufactured, and from the viewpoint of productivity of the optical film, the heat treatment time is preferably short, and less than 300 seconds It is preferable to be

Step (5) Stretching step

It is preferable that the optical film obtained through a heat treatment process is extended|stretched in the width direction. At this time, it is preferable that the amount of residual solvent of a cast film is less than 1 %.

It is preferable that they are 105 % - 300 %, and, as for a draw ratio, it is more preferable that they are 110 % - 200 %. If a draw ratio is 105 % or more, a favorable planar shape will be obtained, and if it is 300 % or less, there is little possibility that an optical film will fracture|rupture.

Here, "draw ratio (%)" means what is calculated|required by the following formula|equation.

Stretch ratio (%) = 100 x width after stretching / width before stretching

Moreover, it is preferable that the surface temperature of the optical film in an extending process is lower than the temperature in a heat processing process, and it is Tg+10 degreeC - Tg+100 degreeC of an optical film, and it is more preferable that it is Tg+20 - Tg+60 degreeC. If it is Tg+10 degreeC or more of an optical film, besides the dimensional stability of an optical film will not deteriorate, the thing with favorable transparency of an optical film is also easy to be obtained.

If the optical film is Tg+100° C. or less, wrinkles do not easily occur after leaving the tenter, so that the winding shape of the roll is not easily deteriorated.

After an extending process performs a heat processing process, after winding up an optical film in roll shape once, you may implement it with respect to the optical film which wound up an extending process from a roll offline. After the stretching process, the surface temperature of the film is preferably cooled to Tg or less until the optical film is separated from the tenter.

In addition, in order to prevent fusion of the film to the tenter gripping portion, the temperature of the gripping portion is preferably cooled to Tg or less.

As for the both ends of the film obtained through an extending process, the both edges are cut|disconnected with a splitting device. It is preferable to give knurling by embossing to both edges of the film from which both ends are cut off. It is preferable to provide at least one end, and, as for knurling, it is more preferable to provide to both ends. As for the width of a knurling, 3 mm - 50 mm are preferable, More preferably, 5 mm - 30 mm and height are 0.5-500 micrometers, More preferably, they are 1-200 micrometers. This may be an unbalanced pressure or a positive pressure may be sufficient as it.

Finally, the film is wound. At this time, it is preferable to wind up while providing a desired tension with a press roller. Moreover, it is more preferable to change a tension gradually from the time of winding-up start to the time of completion|finish. The film to be wound is preferably at least 100 m or more in the longitudinal direction (flexible direction), more preferably 100 to 10000 m, still more preferably 500 to 7000 m, further preferably 1000 to 6000 m. more preferably. Moreover, it is preferable that the width|variety of a film is 600 mm or more, It is more preferable that they are 1100 mm or more and 2900 mm or less, It is still more preferable that they are 1800 mm or more. Moreover, 5000 mm or less is preferable, 3000 mm or less is more preferable, and 2500 mm or less is still more preferable.

[Glass Transition Temperature]

In this specification, "glass transition temperature Tg" is the value which measured the film sample with the dynamic viscoelasticity measuring instrument (DMA). Under the conditions of a frequency of 1 Hz, a temperature increase rate of 5°C/min, a measurement temperature range of 30 to 240°C, and a distance between chucks of 50 mm, a tensile load was applied to a 5 mm×50 mm test piece, and dynamic viscoelasticity was measured. At this time, the value of the inflection point of storage elastic modulus E' was made into "glass transition temperature Tg."

It is preferable that a glass transition temperature is 90-200 degreeC, as for the optical film of this invention, it is more preferable that it is 100-190 degreeC, It is still more preferable that it is 110-180 degreeC.

[Configuration added to optical film]

The optical film of this invention may have an additional structure according to the use. As such a structure, the functional layer formed in the surface treatment given to the surface of an optical film, the surface of an optical film, etc. are mentioned. Hereinafter, this surface treatment and a functional layer are demonstrated.

(Surface treatment)

The optical film of the present invention can achieve an improvement in adhesiveness between the optical film and other layers (eg, polarizer, undercoat layer, and white layer) by subjecting the optical film to surface treatment as necessary. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. The glow discharge treatment referred to herein may be a low-temperature plasma generated under a low-pressure gas of ^{10 -3 to 20 Torr, and further preferably a plasma treatment under atmospheric pressure.} The plasma excitatory gas refers to a gas that is plasma excited under the above conditions, and includes Freons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. About these, details are described in detail on pages 30 - 32 in the Invention Association Publication No. 2001-1745, March 15, 2001 publication, Invention Association, and can be used suitably in this invention. .

(functional layer)

Moreover, the optical film of this invention may laminate|stack the functional layer with a film thickness of 0.1-20 micrometers on at least one surface. Types of this functional layer include a hard coat layer, an antireflection layer (layers with a refractive index adjusted such as a low refractive index layer, a medium refractive index layer, and a high refractive index layer), an antiglare layer, an antistatic layer, an ultraviolet absorption layer, a moisture permeability reducing layer, and the like. .

One layer may be sufficient as the above-mentioned functional layer, and multiple layers may be formed. It is preferable to apply|coat and form the lamination|stacking method of the above-mentioned functional layer on the polarizing plate protective film of this invention or co-casting with the polarizing plate protective film of this invention.

When forming a functional layer by application|coating and drying, it is preferable to use the monomer which has an ethylenically unsaturated group as a binder. This monomer may be monofunctional or polyfunctional may be sufficient as it. Among them, it is preferable to use a polymerizable polyfunctional monomer, it is more preferable to use a photopolymerizable polyfunctional monomer, and it is particularly preferable to use a coating solution containing a monomer having two or more (meth)acryloyl groups. do.

In addition, as a functional layer, various additives may be added to form an antireflection layer (a layer with a refractive index adjusted such as a low refractive index layer, a medium refractive index layer, a high refractive index layer), an antiglare layer, an antistatic layer, an ultraviolet absorbing layer, and a moisture permeability reducing layer.

As for the thickness of the functional layer mentioned above, it is more preferable that it is 0.01-100 micrometers, and it is especially preferable that it is 0.02-50 micrometers. Moreover, as a functional layer which reduces water vapor transmission rate, it is more especially preferable that it is 0.1-20 micrometers in thickness.

<Polarizer>

The optical film of this invention can be used as a polarizing plate protective film.

The polarizing plate can be manufactured by a general method. There is a method of bonding the polarizing plate protective film of the present invention to both sides of a polarizer produced by subjecting the polarizing plate protective film to an alkali treatment and immersing and stretching the polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. In place of the alkali treatment, easy adhesion processing as described in Japanese Patent Application Laid-Open No. Hei 6-94915 and Japanese Unexamined Patent Publication No. 6-118232 may be performed. Moreover, you may perform the surface treatment as mentioned above.

Examples of the adhesive used to bond the polarizing plate protective film-treated surface to the polarizer include polyvinyl alcohol-based adhesives such as polyvinyl alcohol and polyvinyl butyral, and vinyl-based latex such as butyl acrylate. have.

A polarizing plate protective film and a polarizer may be pasted together by another adhesive agent or an adhesive, and may be laminated|stacked directly, without interposing an adhesive agent or an adhesive.

It is preferable that a polarizing plate is comprised from the polarizing plate protective film which protects a polarizer and the at least one surface.

In a liquid crystal display device, a substrate including a liquid crystal cell is usually disposed between two polarizing plates, but the optical film of the present invention can be used as any protective film among two polarizing plates. It is preferable that the optical film of this invention is used as a polarizing plate protective film arrange|positioned on the side far from a liquid crystal cell with respect to a polarizer among two polarizing plate protective films of each polarizing plate.

<Liquid crystal display device>

It is more preferable that a liquid crystal display device contains a liquid crystal cell and the polarizing plate arrange|positioned on at least one of this liquid crystal cell, and it arrange|positions so that it may become the most visible layer of the polarizing plate protective film of this invention contained in the above-mentioned polarizing plate.

(Composition of a general liquid crystal display device)

A liquid crystal display device comprises a liquid crystal cell formed by supporting liquid crystal between two electrode substrates, two polarizing plates disposed on both sides thereof, and, if necessary, at least one optical compensation film disposed between the liquid crystal cell and the polarizing plate. It is preferable to have

The liquid crystal layer of a liquid crystal cell is normally formed by sealing a liquid crystal in the space formed with the spacer between two board|substrates. The transparent electrode layer is formed on the substrate as a transparent film containing a conductive material. You may provide a gas barrier layer, a hard-coat layer, or an undercoat layer (undercoat layer) (used for adhesion|attachment of a transparent electrode layer) in a liquid crystal cell further. These layers are usually formed on a substrate. The substrate of the liquid crystal cell generally has a thickness of 50 µm to 2 mm.

(Type of liquid crystal display)

The polarizing plate protective film can be used for liquid crystal cells in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-ferroelectric Liquid Crystal), OCB (Optically Compensatory Bend), STN (Super Twisted Nematic), VA (Vertically Aligned), Various display modes such as Electrically Controlled Birefringence (ECB) and Hybrid Aligned Nematic (HAN) have been proposed. Moreover, a display mode in which the display mode is divided by orientation has also been proposed. A polarizing plate protective film is effective in the liquid crystal display device of any display mode. Moreover, in any liquid crystal display device of a transmissive type, a reflection type, and a transflective type, it is effective.

Example

Hereinafter, the present invention will be specifically described based on Examples. Materials, reagents, amounts of substances, ratios, operations, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the present invention is not limited to the following examples. In addition, in the following description, "MMA" shows methyl methacrylate, and "MA" shows methyl acrylate.

<Example 1>

(Acrylic resin)

An acrylic resin (PMMA resin) having a weight average molecular weight of 1.3 million and an MMA ratio of 100% used in Examples and Comparative Examples was synthesized by the following method.

300 g of ion-exchanged water and 0.6 g of polyvinyl alcohol (saponification degree 80%, polymerization degree 1700) are added to a 1-liter 3-neck flask equipped with a mechanical stirrer, a thermometer, and a cooling tube and stirred, and polyvinyl alcohol is completely dissolved After making it, 100 g of methyl methacrylate and 0.15 g of azobisisobutyronitrile were added, and it was made to react at 85 degreeC for 6 hours. The obtained suspension was filtered with a nylon filter cloth, methanol wash|cleaned, and the target polymer was obtained in the form of beads by drying the filtrate at 50 degreeC overnight.

[Production of optical film]

(dissolution step: preparation of dope composition)

The composition described below was put into a mixing tank, stirred while heating, and each component was dissolved to prepare a dope composition.

(dope composition 1)

100 parts by mass of PMMA resin

10 parts by mass of rubber elastic particles

0.1 parts by mass of antioxidant

383 parts by mass of dichloromethane

57 parts by mass of methanol

In addition, as the rubber elastic particles, Kaneace M-210 (manufactured by Kaneka Corporation) was used. As the antioxidant, Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.) was used.

(Measurement of glass transition temperature)

In order to measure the glass transition temperature of the film obtained from the prepared dope composition mentioned above, the obtained dope composition was cast|flow_spread on a glass plate, and the 40-micrometer-thick film was produced by drying the obtained cast film at 140 degreeC for 40 minutes.

Next, about the obtained film, the glass transition temperature (Tg) was measured on the following conditions with the dynamic viscoelasticity measuring machine (DVA-225 by a IT instrumentation control company). Under the conditions of a frequency of 1 Hz, a temperature increase rate of 5°C/min, a measurement temperature range of 30 to 240°C, and a distance between chucks of 50 mm, a tensile load was applied to a 5 mm×50 mm test piece, and dynamic viscoelasticity was measured. At this time, the value of the inflection point of storage elastic modulus E' was made into "glass transition temperature Tg."

(casting process, peeling process)

The dope composition prepared above was uniformly cast|flow_spreaded from the casting die to the stainless steel band (casting support body). When the amount of residual solvent in a cast film became 20 mass %, it peeled as a cast film from a cast support body. Both ends in the width direction of the peeled flexible film were gripped by a tenter.

(Preheating process, heat treatment process, stretching process)

For the peeled cast film, under the conditions shown in Table 1, a preheating process (shrinkage in the width direction at the temperature in Table 1), a heat treatment process in a tenter (heat treatment at the temperature in Table 1), and a stretching process (the temperature in Table 1 in the width direction) stretching) was carried out. The roll appearance evaluation result of the obtained film and various physical properties were described in Table 1.

In addition, the temperature described here is the surface temperature of the film in each process.

The PET film which affixed E thermocouple on the surface previously in each process was conveyed, and the surface temperature was measured using NR-1000 by Keyence Corporation.

<Roll appearance evaluation>

The obtained film was wound up as a roll of 3900 m, and the roll external appearance was evaluated visually.

A: No wrinkles

B: Wrinkles occur at the end

C: Folding occurs with the wrinkle as the starting point

<85°C, relative humidity 85%, dimensional change before and after 24 hours elapsed>

About the obtained film, 85 degreeC, a relative humidity of 85%, and the dimensional change rate before and after 24 hours elapsed, ie, the value of (L'-L0)/L0} x 100% were calculated|required with respect to the width direction of the film. Here, the aforementioned L0 represents the film length (unit: mm) before lapse of 24 hours at 85°C and 85% relative humidity, and L′ is 85°C and after 24 hours at 85% relative humidity, 25°C , represents the film length (unit: mm) after 2 hours have elapsed in an environment of 60% relative humidity. In addition, the sample film used used the thing of 30 mm x 120 mm, and other conditions were as follows.

After controlling the humidity for at least 2 hours in an atmosphere of 25°C and 60% relative humidity, with an automatic pin gauge (manufactured by Shinto Science Co., Ltd.), holes having a diameter of 6 mm were cut at intervals of 100 mm so as to be parallel to the 120 mm side of the film. The raw number (L0) is measured to the smallest scale of 1/1000 mm. And after 24 hours passed at 85 degreeC and 85% of a relative humidity, the dimension L' of the punch space|interval was measured after humidity control in 25 degreeC and the atmosphere of 60% of a relative humidity for 2 hours.

<Heize>

The haze was measured using a haze meter (NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd.). In addition, regarding the measurement, it measured based on JIS-K7105.

<Examples 2 to 12, Comparative Examples 1 to 6>

An optical film was prepared in the same manner as in Example 1 except that the conditions shown in Table 1 were used in the preheating step, the heat treatment step, and the stretching step, and each evaluation item was measured in the same manner as in Example 1.

In Comparative Example 6, since the optical film was fractured, it could not be evaluated.

<Example 13>

Except having changed the dope composition to the following, it carried out similarly to Example 1, and manufactured the optical film. In addition, in the following dope compositions 2 to 6, all use the same thing as the dope composition 1 as PMMA resin, and all use Kanace M-210 (made by Kaneka Co., Ltd.) as an antioxidant for rubber elastic particle|grains. All of them used Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.).

(dope composition 2)

100 parts by mass of PMMA resin

0.1 parts by mass of antioxidant

426 parts by mass of dichloromethane

64 parts by mass of methanol

<Example 14>

Except having changed the dope composition to the following, it carried out similarly to Example 1, and manufactured the optical film.

(dope composition 3)

100 parts by mass of PMMA resin

20 parts by mass of plasticizer

10 parts by mass of rubber elastic particles

0.1 parts by mass of antioxidant

426 parts by mass of dichloromethane

64 parts by mass of methanol

Moreover, BisP-TMC (made by Honshu Chemical Industry Co., Ltd.) was used as a plasticizer.

<Example 15>

Except having changed the dope composition to the following, it carried out similarly to Example 1, and manufactured the optical film.

(dope composition 4)

70 parts by mass of PMMA resin

CAP 30 parts by mass

0.1 parts by mass of antioxidant

348 parts by mass of dichloromethane

52 parts by mass of methanol

In addition, CAP482-20 (made by Eastman Chemicals) was used as CAP.

<Example 16>

Except having changed the dope composition to the following, it carried out similarly to Example 1, and manufactured the optical film.

(dope composition 5)

100 parts by mass of polystyrene

0.1 parts by mass of antioxidant

234 parts by mass of dichloromethane

Moreover, PSJ-polystyrene G9504 (made by PS Japan Co., Ltd.) was used as polystyrene.

Claims (5)

A method for producing an optical film by solution film forming, comprising:
Casting step (1) of casting a dope composition containing a polymer and a solvent on a support to form a cast film, and drying the solvent;
Peeling off the cast film from the support within the range of the content of the solvent relative to the total solid content of the cast film is 5 to 60 mass %, and a peeling step (2) of gripping both ends of the cast film in the width direction of the cast film with a tenter,
The preheating process (3) of shrinking the said hold|gripped cast film to 97 % - 70% in the width direction at the temperature of Tg-30 degreeC - Tg+20 degreeC with respect to the glass transition temperature Tg of an optical film (3), and
The heat treatment process (4) of heat-processing the said cast film at the temperature of Tg+60 degreeC - Tg+120 degreeC with respect to the glass transition temperature Tg of an optical film, and obtaining an optical film
A method for producing an optical film, including in this order. The method of claim 1,
Further, after the heat treatment step (4),
With respect to the glass transition temperature Tg of the optical film, Tg + 10 ° C. to Tg + 100 ° C. Further, at a temperature lower than the heat treatment temperature in the step (4), the stretching step (5) of stretching the optical film in the width direction to 105% to 300% Including, a method of manufacturing an optical film. The method of claim 1,
The manufacturing method of the optical film in which the said polymer contains a (meth)acrylic-type resin. The method of claim 1,
The manufacturing method of the optical film in which the said dope composition contains the rubber elastic particle in the ratio of 1-50 mass parts with respect to 100 mass parts of said polymers. delete