KR20200115366A - Method of manufacturing optical film - Google Patents

Abstract

The present invention relates to an optical film comprising a (meth)acrylic resin and elastic particles, or to a manufacturing method of an optical film, containing a cycloolefin resin having a polar group. The manufacturing method of an optical film comprises the steps of: crushing a half-material generated in a manufacturing process of the optical film to obtain a film piece having bulk density of 0.02 to 0.4 g/cm^3; dissolving raw materials containing the film piece in a solvent to prepare a dope; and drying and peeling the dope to obtain a film-like material after the dope is flexible on a support. According to the manufacturing method of an optical film, failure of the film is suppressed by foreign matters.

Description

Manufacturing method of an optical film TECHNICAL FIELD [METHOD OF MANUFACTURING OPTICAL FILM}

The present invention relates to a method for producing an optical film.

Optical films, such as a polarizing plate protective film, are used for display devices, such as a liquid crystal display device and an organic EL display device. As such an optical film, a film containing a cycloolefin resin or a (meth)acrylic resin as a main component may be used from the viewpoint of having excellent transparency, dimensional stability, and low hygroscopicity.

These films can be produced by a melt film forming method (melt method) or a solution film forming method (cast method). Among them, the cast method is advantageous in that it does not need to be melted under a high temperature such as the melt method (there is no high-temperature heating step), there is little risk of material deterioration such as pyrolysis, and there are few restrictions on the material to be used.

In particular, it is desired to be able to reuse non-standard products or film cut materials (hereinafter referred to as "half materials") generated during production from the viewpoint of reducing manufacturing cost. The cast method is also advantageous in that there is little concern about material deterioration such as thermal decomposition even for such a semi-material, and the semi-material can be reused.

As a manufacturing method of an optical film by a cast method using a semi-material, for example, 1) a step of preparing a dope containing a (meth)acrylic resin and a cellulose ester resin, and 2) casting a dope to form an optical film A manufacturing method of an optical film having a step of performing, 3) a step of crushing a half-material to form a chip, and 4) a step of supplying the chip to a dope preparation step are known (see, for example, Patent Document 1). And it is said that by removing the chips in the step 4), aggregation of the half-material can be suppressed, and thus, when the chips are dissolved in a solvent, the undissolved product of the half-material can be reduced.

Japanese Patent Application Publication No. 2010-242017

However, unlike cellulose ester resins that have been widely used in the past, (meth)acrylic resins and cycloolefin resins have a low glass transition temperature. In particular, in the (meth)acrylic resin, in order to improve brittleness, elastic particles such as rubber particles may be additionally added. It has been newly discovered that foreign matter failure is likely to occur in the resulting optical film when the half-material containing a large amount of such a component having a low glass transition temperature is reused.

Although this reason is not clear, it thinks as follows. Typically, when the half-wood is reused, in order to make it easier to dissolve in a solvent, the half-wood is crushed until it has a size of a certain size or less. At this time, if the heat generated by the load at the time of crushing of the shards is large, the shards after crushing (hereinafter, referred to as "film pieces") are likely to be fused together, particularly between the pieces of films containing a component having a relatively low glass transition temperature. When film pieces are fused together, voids are eliminated between the fused film pieces, so that when dissolving in a solvent, the solvent does not penetrate easily, and poor dissolution is liable to occur. Thereby, foreign matter failure due to undissolved matter is liable to occur.

The present invention has been made in view of the above circumstances, and is a method for producing an optical film containing a resin having a relatively low glass transition temperature using a half material, reducing undissolved matter of the half material, and preventing foreign matter failure of the film resulting from it. It aims at providing a manufacturing method of an optical film which can be suppressed.

The present invention relates to a method for producing the following optical films.

The manufacturing method of the optical film of the present invention is a method of manufacturing an optical film containing a (meth)acrylic resin and elastic particles, or an optical film containing a cycloolefin resin having a polar group, which occurs in the manufacturing process of the optical film. The step of crushing the half material to obtain a film piece having a bulk density of 0.02 to 0.4 g/cm 3, a step of preparing a dope by dissolving the raw material containing the film piece in a solvent, and the step of preparing a dope on a support. After that, it includes a step of drying and peeling to obtain a film-like material.

According to the present invention, as a manufacturing method of an optical film containing a resin having a relatively low glass transition temperature using a semi-material, an optical film capable of reducing undissolved matter of the semi-material and suppressing foreign matter failure of the film resulting from it A manufacturing method can be provided.

1 is a cross-sectional view showing a crusher according to the present embodiment.
2 is a cross-sectional view showing a crusher according to a modified example.
3 is a cross-sectional view showing a crusher according to a modified example.

1. Manufacturing method of optical film

The manufacturing method of the optical film of the present invention includes 1) a step of crushing a half-material generated in the manufacturing process of an optical film to obtain a film piece having an appropriately low bulk density (half-material crushing step), and 2) a film piece. The raw material to be dissolved in a solvent to prepare a dope (dope preparation step), and 3) after the dope is pliable on a support, dried and peeled to obtain a film-like substance (film forming step).

1) Half-wood crushing process

In this step, the half material generated in the manufacturing step of the optical film is crushed to obtain a film piece whose bulk density is suitably low.

The semi-material may be a cut-out material or an out-of-standard product cut out in the manufacturing process of the optical film. In other words, in the manufacturing process of the optical film, defective products may occur due to cut-out end portions or irregular windings. These do not become products, but since there is no problem with the material, they can be reused.

The thickness of the half material is the same as that of the optical film, and can be, for example, 5 to 100 µm, preferably 5 to 40 µm. Each material constituting the optical film and the half material will be described in detail later.

Such half-wood is crushed (or pulverized) to a size sufficient to dissolve in a solvent. The semi-material used in the present invention contains, as a main component, a resin having a relatively low melting point such as a (meth)acrylic resin or a cycloolefin resin having a polar group. Therefore, if the heat generated by the load at the time of crushing is large, the heat makes it easier for the film pieces to be fused to each other after crushing. When the film pieces after crushing are fused together, the gap between the films disappears, so when dissolving the film pieces in a solvent (to prepare dope), the solvent does not penetrate well into the fusion product of the film pieces Cannot be dissolved. Thereby, a foreign matter failure may occur in the obtained optical film. Moreover, when the heat generation at the time of crushing is large, the film piece is thermally deteriorated by the heat, and coloration may occur in the obtained optical film.

In particular, in order to improve brittleness, an optical film containing a (meth)acrylic resin may further contain elastomer particles having a low melting point. It is desired to reduce heat generation at the time of crushing since it is easy to cause fusion or thermal deterioration due to heat generation at the time of crushing of the plate or film piece containing the elastic particles having a low melting point.

Therefore, in the present invention, the half-wood is crushed under the condition that the heat generated at the time of crushing (heat received by the half-wood or the film piece during crushing) is reduced. That is, under the condition that the bulk density of the obtained film piece becomes moderately low, the half-wood is crushed.

Specifically, it is crushed under the condition that the bulk density of the obtained film piece is 0.02 to 0.4 g/cm 3. When the bulk density of the obtained film piece is 0.4 g/cm 3 or less (that is, when the film piece is large), the load at the time of crushing can be reduced, so that heat generation at the time of crushing can be reduced. Thereby, it is possible to suppress the fusion between the film pieces by heat, and to suppress the dissolution defects in the solvent. Moreover, since deterioration of a film piece due to heat at the time of crushing can also be suppressed, coloring of the obtained optical film can also be suppressed. On the other hand, when the bulk density of the obtained film piece is 0.02 g/cm 3 or more, since the obtained film piece is not too large, a dissolution defect in a solvent can be suppressed. The bulk density of the obtained film piece is preferably 0.02 to 0.34 g/cm 3 from the above viewpoint.

The bulk density of a film piece can be measured according to 6 of JIS Z 8807 (Measurement method of density and specific gravity by a specific gravity bottle).

In addition, adjusting the bulk density of the raw material of the optical film itself is known, for example, as shown in Japanese Laid-Open Patent Publication No. 2002-128903, but this document has a bulk density of 0.45 g/cm 3 or more. That is, the average particle diameter (size) of the film piece is made small, so that it is easily dissolved in a solvent. Therefore, as in the present application, when using a half-material containing a component having a relatively low glass transition temperature, the idea of ``to suppress fusion bonding or thermal deterioration of film pieces accompanying heat generation at the time of crushing'', but for that, `` Adjusting the bulk density of the film piece obtained after crushing to 0.4 g/cm 3 or less” is not considered to be shown.

The average particle diameter of the film piece is not particularly limited, but it is preferably 2 to 7.3 mm. When the average particle diameter of the film piece is 2 mm or more, it is easy to lower the bulk density of the film piece, so it is easy to adjust the bulk density to the above range. When the average particle diameter of the film piece is 7.3 mm or less, since the film piece is not too large, it is easy to suppress the resulting dissolution in the solvent. It is more preferable that the average particle diameter of a film piece is 4-7 mm from the said viewpoint.

The average particle diameter of a film piece can be calculated|required from the particle size distribution obtained by a sieving test. Specifically, in accordance with JIS Z 8815 (1994), a sieving test is performed to obtain a particle size distribution based on mass. And the 50% particle diameter of the obtained mass-based particle size distribution can be calculated|required as "average particle diameter" (sieve diameter).

It is preferable that the film piece is not too crushed, that is, the ratio of the film piece which is too finely crushed to become small is small. Specifically, when the film piece is sieved for 2 minutes with a mesh having an average eye size of 1 mm, the fraction (%) (hereinafter referred to as "fractionation") is 10 with respect to the total amount of the film piece before sieving. It is preferably not more than mass%. Such a film piece is crushed under gentle conditions, and since the load at the time of crushing is moderately small, it is easier to suppress the fusion of the film pieces and thermal deterioration due to heat generation at the time of crushing. The fractionation ratio (%) of the film piece is more preferably 5% by mass or less with respect to the total amount of the film piece before sifting from the above viewpoint.

The bulk density, average particle diameter, and fractionation ratio of the film piece can be adjusted according to the crushing conditions. In order to keep the bulk density, average particle diameter, and fractionation ratio of the film pieces within the above ranges, reduce heat generation at the time of crushing (reduce the heat received by the plate or film pieces at the time of crushing), specifically, reduce the load at the time of crushing. It is preferable to reduce heat generation or reduce heat generation during crushing.

The crushing of the half-material can be carried out by any method, for example, by sandwiching the half-material between the fixed blade and the rotating blade and crushing it. And, from the viewpoint of reducing the heat received by the plate or film piece during crushing, the crushing of the plate is 1) the rotational speed of the rotating blade is reduced to reduce the load during crushing, and 2) the cooling gas is supplied. It is preferable to carry out (by blowing air) while cooling the inside of the system. In addition, the supply of the cooling gas is different from the blowing for supplying the half-wood to the crushing mechanism.

The supply direction C (airflow direction) of the cooling gas is not particularly limited, and may be the forward direction (cocurrent direction) with the half-material supply direction F, or may be a reverse direction (a counter flow direction or an opposing direction). Becomes (see Fig. 1). Among them, from the viewpoint of increasing the residence time of the cooling gas and increasing the heat exchange efficiency, the supply direction C of the cooling gas is in the opposite direction to the supply direction F of the half material (direction to be counter-current or opposite). desirable.

The temperature of the cooling gas is not particularly limited, and may be room temperature or lower than room temperature. The temperature of the cooling gas can be, for example, 10 to 30°C. In addition, the flow rate of the cooling gas is not particularly limited, and can be, for example, 2 to 40 Nm 3 /hour. The type of the cooling gas is not particularly limited, and may be an inert gas such as air or nitrogen gas.

The crushing of such a plate can be carried out with a known crushing machine using a fixed blade and a rotating blade.

1 is a cross-sectional view showing a crusher 100 according to the present embodiment.

As shown in FIG. 1, the crusher 100 includes a crushing chamber 110, a supply port 120 for supplying half-materials therein, a crushing mechanism 130 disposed in the crushing chamber 110, It has an outlet 140 for discharging the crushed half-wood, and a screen 150 disposed near the outlet 140 of the crushing chamber 110.

The supply port 120 is connected via a hopper 210 and an arbitrary supply pipe 220. The discharge port 140 is connected to the discharge pipe 230. Thereby, while supplying the half-material supplied from the hopper 210 into the crushing chamber 110 from the supply port 120, the film piece obtained by crushing can be discharged from the discharge port 140 through the discharge pipe 230. have.

The crushing mechanism 130 is disposed in the crushing chamber 110 and has a fixed blade 130A fixed to the inner wall surface of the crushing chamber 110 and a rotating blade 130B attached to a rotating shaft. Then, the half-material supplied from the supply port 120 is crushed by shearing force while being sandwiched between the fixed blade 130A and the rotating blade 130B.

The screen 150 may be disposed between the crushing mechanism 130 and the discharge port 140 of the crushing chamber 110, or near the discharge port 140. In this embodiment, the screen 150 is disposed in the discharge port 140. A plurality of meshes (holes) are formed in the screen 150. Thereby, among the film pieces obtained by crushing by the fixed blade 130A and the rotating blade 130B, only the film pieces having a predetermined size or less are passed.

In addition, the crusher 100 further has an air outlet 160 for sending a cooling gas in the crusher chamber 110. The position of the air blower 160 may be set according to the supply direction C of the cooling gas, and is not particularly limited. For example, the air outlet 160 may be disposed on the downstream side of the crushing chamber 110 in the supply direction F of the half material (for example, on the downstream side from the rotation shaft) (see FIG. 1 ), or disposed on the lateral side. It may be possible (see Fig. 2 to be described later). In this embodiment, the air blower 160 is disposed on the downstream side of the crushing chamber 110 in the supply direction F of the half-material (specifically, on the downstream side of the rotation shaft of the rotary blade 130B).

The blower 160 is connected to a blower mechanism (not shown). Thereby, it is possible to supply the cooling gas into the crushing chamber 110. The temperature of the cooling gas is further adjusted by a temperature adjusting means (not shown). The temperature of the cooling gas is not particularly limited, and may be 10 to 30°C.

In the crusher 100 shown in FIG. 1, the half-material supplied from the hopper 210 is empty and supplied from the supply port 120 into the crushing chamber 110. Subsequently, the supplied half-material is crushed until it reaches a predetermined size or less while being sandwiched between the crushing mechanism 130 (the fixed blade 130A and the rotary blade 130B) in the crushing chamber 110. The half-material (film piece) crushed to a predetermined size or less is discharged from the discharge port 140 through a plurality of meshes formed in the screen 150.

In the present invention, the crushing conditions of the half-material are set so that the bulk density of the obtained film piece falls within the above range. In the crushing conditions of the half-material, the supply of cooling gas (blowing) into the crushing chamber 110, the number of rotations of the rotary blade 130B, the temperature of the fixed blade 130A, the mesh diameter of the screen 150, the crushing time ( And the number of stages of the crushing chamber 110). Especially, from the viewpoint of adjusting the bulk density of the obtained film piece within the above range, the crushing of the half-material is to 1) supply a cooling gas, and 2) reduce the number of rotations of the rotary blade 130B (300 Adjusting to -800 rpm) is preferable; It is more preferable to further adjust at least one or more of the mesh diameter of the screen 150, the temperature of the fixed blade 130A, and the crushing time (the number of stages of the crushing chamber 110).

(About supply of cooling gas)

By supplying (blowing) the cooling gas into the crushing chamber 110, the interior of the crushing chamber 110 can be cooled or removed. That is, by supplying the cooling gas into the crushing chamber 110, it is possible to appropriately cool the inside of the crushing chamber 110, the fixed blade 130A, the rotating blade 130B, and the like. Thereby, since heat generated by the load at the time of crushing can be removed while crushing the half-material to a predetermined size, it is easy to suppress fusion of film pieces and thermal deterioration.

As described above, the cooling gas supply direction C (airflow direction) may be a direction in which co-current flows with respect to the supply direction F of the half material or counter flow direction may be used. Among them, from the viewpoint of increasing the residence time of the cooling gas in the crushing chamber 110 and increasing the heat exchange efficiency, the supply direction C of the cooling gas is a direction in which counter flow is made to the supply direction F of the semi-material. It is preferable to be.

For example, in FIG. 1, in the supply direction F of the half-material, the air outlet 160 is on the side or the downstream side of the crushing chamber 110 (for example, in the supply direction F of the half-material, the rotary blade 130B It is preferable that it is arranged in the range of ), and it is more preferable that it is arranged on the downstream side than the rotation axis of ). Specifically, in a cross section (see Fig. 1) orthogonal to the axial direction of the rotation axis of the rotary blade 130B, the intersection angle between the supply direction C of the cooling gas and the supply direction F of the half material is, for example, 0 to It is preferably 40°, more preferably 0 to 30°, and more preferably 0 to 10°. The crossing angle refers to the smaller one of the angles formed by two directions.

(About the number of revolutions)

It is preferable that the rotational speed of the rotating blade 130B be low. Specifically, the rotational speed of the rotary blade 130B is preferably 300 to 800 rpm. When the rotational speed is 300 rpm or more, sufficient crushing performance is easily obtained, and thus the film piece is crushed to a predetermined size. If the rotational speed is 800 rpm or less, the load at the time of crushing is not too large, and thus heat generation due to it can be sufficiently suppressed. It is more preferable that the rotational speed of the rotary blade 130B is 400 to 600 rpm from the above viewpoint.

(About the temperature of the fixed blade (130A))

The temperature of the fixed blade 130A is preferably 10 to (Tg-50)°C when the glass transition temperature of the resin contained in the half-material is Tg. When the temperature of the fixed blade 130A is 10° C. or higher, it is easy to suppress brittleness because the plate does not become too low temperature. Thereby, it is possible to suppress breakage that is too finer than a preset size. When the temperature of the fixed blade 130A is (Tg-50)° C. or less, it is easy to suppress the progress of fusion or thermal deterioration of the half-material or film piece along with heat generation at the time of crushing. The temperature of the fixed blade 130A is more preferably 20 to (Tg-70)°C from the above viewpoint. The temperature of the fixed blade 130A is measured as the actual surface temperature of the fixed blade 130A.

(For the mesh diameter of screen 150)

It is preferable that the mesh diameter of the screen 150 is 2 mm or more and less than 10 mm. If the mesh diameter of the screen 150 is 2 mm or more, since the ratio of the film pieces passing through the mesh of the screen 150 and discharged outside the crushing chamber 110 can be increased, the load at the time of crushing can be reduced easily, As a result, it is easy to reduce heat generation during crushing. When the mesh diameter of the screen 150 is 10 mm or less, the size of the film piece passing through the mesh of the screen 150 can be suitably small enough to be sufficiently dissolved in a solvent. The mesh diameter of the screen 150 is more preferably 4 to 8 mm from the above viewpoint.

(About the number of stages in the crushing chamber 110)

The number of crushing chambers 110 may be only one or may be plural. That is, a plurality of crushing chambers 110 may be connected. However, from the viewpoint of reducing the load at the time of crushing, the number of stages of the crushing chamber 110 is preferably small. That is, it is preferable that the number of stages of the crushing chamber 110 is 1 stage.

In this way, among the film pieces obtained by being crushed in the crushing chamber 110, the ones that have passed through the screen 150 are discharged from the discharge port 140. The discharged film piece is air-delivered through the discharge pipe 230.

In addition, in this embodiment, although the example which uses what is shown in FIG. 1 as a crusher was shown, it is not limited to this.

2 and 3 are cross-sectional views showing a crusher 100 according to a modified example. As shown in FIG. 2, the air blower 160 may be arrange|positioned so that it may supply (air blow) gas for cooling from the side direction with respect to the supply direction F of the half-material. Moreover, as shown in FIG. 3, a plurality of crushing chambers 110 may be connected in series to the supply direction F of the half-material.

In addition, as for the shredder 100, the BO series open flat cutter manufactured by Horai Corporation (a device that can make the shape of the shredded object constant by passing through a sieve installed under the blade after making the film fine with a rotating blade and a fixed blade) B. A sheet pelletizer manufactured by Horai Co., Ltd. (a device that cuts vertically while taking up a sheet with a vertical blade of a roll cutter, and then cuts it horizontally with a rotating blade and a fixed blade) can be used.

2) Dope preparation process

In this step, the raw material containing the film piece obtained in the step 1) is dissolved in a solvent (solvent) to obtain a dope.

The raw material containing a film piece is a raw material of an optical film. It is preferable that the raw material of an optical film further contains not only a film piece but a pure material. Pure materials refer to new materials that are not reused products such as film pieces. It is preferable that it is 10 to 80 mass% with respect to a raw material, and, as for content of a film piece, it is more preferable that it is 30 to 60 mass %.

The raw material of the optical film contains a (meth)acrylic resin or a cycloolefin resin having a polar group as a matrix resin.

((Meth)acrylic resin)

The (meth)acrylic resin is a homopolymer of a (meth)acrylic acid ester, or a copolymer of a (meth)acrylic acid ester and a copolymerizable monomer capable of copolymerizing with it. In addition, (meth)acrylic means acrylic or methacryl. It is preferable that (meth)acrylic acid ester is methyl methacrylate.

That is, the (meth)acrylic resin contains a structural unit derived from methyl methacrylate, and is a structural unit derived from a copolymerizable monomer other than methyl methacrylate that can be copolymerized with it (hereinafter, simply referred to as “copolymerization monomer”) It may further contain.

Although the copolymerization monomer is not particularly limited, it is preferable to contain a copolymerization monomer having a cyclic structure from the viewpoint of making it easy to improve drying properties during solution film formation. Examples of the cyclic structure include an alicyclic ring, an aromatic ring, and an imide ring. Since the copolymerization monomer having such a cyclic structure has a large free volume of molecules, it is easy to form a gap (space) for moving the solvent molecules in the resin matrix of the film-like material in the solution film forming step. Thereby, the solvent removal property, that is, drying property can be improved.

Examples of the copolymerization monomer having a cyclic structure,

Alicyclic (meth)acrylic acid esters such as dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, cyclohexyl (meth)acrylate, and 6-membered lactone (meth)acrylic acid ester;

Vinyls having an alicyclic such as vinylcyclohexane;

Vinyls having an aromatic ring such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, and α-methylstyrene; And

Maleimides (compounds having an imide ring) such as N-phenylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-cyclohexylmaleimide, and N-o-chlorophenylmaleimide are included.

Among them, the copolymerization monomer having a cyclic structure is preferably a copolymerization monomer having an aromatic ring (eg, vinyls having an aromatic ring) or a copolymerization monomer having an imide ring (eg, maleimides). These monomers easily raise the glass transition temperature of the (meth)acrylic resin.

The structural unit derived from the copolymerization monomer may further contain a structural unit derived from a copolymerization monomer other than the structural unit derived from the copolymerization monomer having a cyclic structure.

Examples of other copolymerization monomers include copolymerization monomers that do not have a ring structure, that is,

Ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate Alkyl (meth)acrylates having 2 to 20 carbon atoms, such as;

Unsaturated nitriles such as (meth)acrylonitrile;

Unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, and (meth)acrylic acid;

Olefins such as vinyl acetate, ethylene and propylene;

Vinyl halides such as vinyl chloride, vinylidene chloride, and vinylidene fluoride;

(Meth)acrylamides such as (meth)acrylamide, methyl (meth)acrylamide, ethyl (meth)acrylamide, and propyl (meth)acrylamide are included. These may be used alone or in combination of two or more.

When the (meth)acrylic resin contains a structural unit derived from a copolymerized monomer having a cyclic structure, the content is preferably 10 to 40% by mass with respect to all structural units constituting the (meth)acrylic resin, It is more preferable that it is 10 to 30 mass %. When the content of the structural unit derived from the copolymerized monomer having a cyclic structure is 10% by mass or more, it is easy to increase the glass transition temperature of the (meth)acrylic resin, so that it is easy to increase the drying temperature during solution film formation, Since it originates from the structure, it is easy to form a space in which the solvent can be moved, so that the drying property is also easily improved. Moreover, when the content of the structural unit derived from the copolymerization monomer having a cyclic structure is 40% by mass or less, the film-like material containing the (meth)acrylic resin is not too brittle.

The kind and composition of the monomer of the (meth)acrylic resin can be specified by ¹ H-NMR.

It is preferable that the glass transition temperature (Tg) of (meth)acrylic resin is 90 degreeC or more. When the Tg of the (meth)acrylic resin is 90°C or higher, not only the heat resistance of the optical film can be improved, but also the drying temperature at the time of film formation of the solution can be increased, so that drying properties are easily improved. From the viewpoint of making it easier to increase the drying temperature at the time of solution film formation, and not inhibiting the toughness of the optical film well, the Tg of the (meth)acrylic resin is more preferably 100 to 150°C.

The glass transition temperature (Tg) of the (meth)acrylic resin can be measured in accordance with JIS K 7121-2012 or ASTM D 3418-82 using DSC (Differential Scanning Colorimetry: Differential Scanning Calorimetry).

The glass transition temperature (Tg) of the (meth)acrylic resin can be adjusted according to the monomer composition. In order to increase the glass transition temperature (Tg) of the (meth)acrylic resin, for example, it is preferable to increase the content of the structural unit derived from a copolymerization monomer having a cyclic structure.

It is preferable that the weight average molecular weight (Mw) of (meth)acrylic resin is 400,000-3 million. When the weight average molecular weight of the methacrylic resin is in the above range, film forming properties and drying properties are not well impaired, while providing sufficient mechanical strength (toughness) to the film. It is more preferable that the weight average molecular weight of (meth)acrylic resin is 500,000-2 million from the said viewpoint.

The weight average molecular weight (Mw) of the (meth)acrylic resin can be measured in terms of polystyrene by gel permeation chromatography (GPC). Specifically, it can measure using the Tosoh Corporation HLC8220GPC) and a column (Tosoh Corporation TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL serial). Measurement conditions can be made the same as in Examples described later.

(Cycloolefin resin having a polar group)

Although the cycloolefin resin having a polar group is not particularly limited, it is preferably a polymer containing a structural unit derived from a norbornene skeleton-containing monomer having a polar group.

The norbornene skeleton-containing monomer having a polar group is preferably a monomer represented by formula (A-1) or (A-2), and from the viewpoint of making it easy to localize the polar group possessed by the resin on the film surface, the formula (A It is more preferable that it is a monomer represented by -2).

[Formula 1]

In formula (A-1), each of R ¹ to R ⁴ independently represents a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or a polar group. However, at least one of R ¹ to R ⁴ is a polar group. Moreover, the case where R ¹ and R ² are a hydrogen atom and R ³ and R ⁴ are a group other than a hydrogen atom is excluded.

The polar group refers to a functional group in which polarization is generated by an atom with high electronegativity such as an oxygen atom, a sulfur atom, and a nitrogen atom. Examples of such a polar group include a carboxyl group, a hydroxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, a cyano group, and a group in which these groups are bonded through a linking group such as an alkylene group. Among them, a carboxyl group, a hydroxy group, an alkoxycarbonyl group, or an aryloxycarbonyl group is preferable, and an alkoxycarbonyl group and an aryloxycarbonyl group are more preferable from the viewpoint of ensuring solubility during solution film formation.

p represents the integer of 0-2.

[Formula 2]

In formula (A-2), R ⁵ represents an alkylsilyl group having a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms. Among them, a hydrocarbon group having 1 to 3 carbon atoms is preferable.

R ⁶ represents a polar group. Examples of the polar group include those similar to those described above. Among them, a carboxy group, a hydroxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, or a cyano group is preferable, and a carboxyl group, a hydroxy group, an alkoxycarbonyl group and an aryloxycarbonyl group are more preferable, and solubility in solution formation From the viewpoint of securing a, an alkoxycarbonyl group or an aryloxycarbonyl group is more preferable.

p represents the integer of 0-2.

Examples of the monomer represented by formula (A-1) or (A-2) include the following.

[Formula 3]

The cycloolefin resin having a polar group may further contain a structural unit derived from a copolymerizable monomer capable of copolymerizing with the norbornene skeleton-containing monomer having a polar group (hereinafter, referred to as "copolymerization monomer"), if necessary.

Examples of the copolymerization monomer include a norbornene skeleton-containing monomer having no polar group; A copolymerization monomer capable of ring-opening copolymerization; And a copolymerization monomer capable of addition copolymerization.

Examples of the copolymerizable monomer capable of ring-opening copolymerization include cycloolefins having no norbornene skeleton, such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

Examples of the copolymerizable monomer capable of addition copolymerization include an unsaturated double bond-containing compound, a vinyl-based cyclic hydrocarbon monomer, and a (meth)acrylic acid ester. Examples of the unsaturated double bond-containing compound are olefin compounds having 2 to 12 carbon atoms (preferably 2 to 8), and examples thereof include ethylene, propylene, and butene. Examples of the vinyl-based cyclic hydrocarbon monomer include vinylcyclopentene-based monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene. Examples of the (meth)acrylic acid ester include alkyl (meth)acrylates having 1 to 20 carbon atoms such as methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate.

Among these, the cycloolefin resin having a polar group is preferably a homopolymer or a copolymer of a monomer represented by formula (A-1) or (A-2), and examples include the following.

(1) Ring-opening polymer of a monomer containing a norbornene skeleton having a polar group

(2) Ring-opening copolymer of a monomer containing a norbornene skeleton having a polar group and a copolymerizable monomer

(3) Hydrogenated (co)polymer of the ring-opening (co)polymer of (1) or (2) above.

(4) (co)polymer in which the ring-opening (co)polymer of (1) or (2) is cyclized by a Friedel-Crafts reaction and then hydrogenated

(5) Saturated polymer of a monomer containing a norbornene skeleton having a polar group and a compound containing an unsaturated double bond

(6) Addition type (co)polymer of a monomer containing a norbornene skeleton having a polar group and its hydrogenated (co)polymer

(7) Alternate copolymer of norbornene skeleton-containing monomer having a polar group and methacrylate or acrylate

Among them, (1) to (3) are preferable, and (3) is more preferable. That is, it is preferable that the cycloolefin resin is a polymer containing the structural unit represented by formula (B-1) or the structural unit represented by formula (B-2). The structural unit represented by formula (B-1) is derived from a monomer represented by the aforementioned formula (A-1); The structural unit represented by formula (B-2) is derived from a monomer represented by the aforementioned formula (A-2). Such a cycloolefin resin is a polymer containing a structural unit represented by formula (B-2), or a structural unit represented by formula (B-1) and a structural unit represented by formula (B-2). It is preferably a polymer. This is because the glass transition temperature of the cycloolefin-based resin is high, and it is excellent in transparency.

[Formula 4]

X in formula (B-1) represents -CH=CH- or -CH ₂ CH ₂ -. Formula (B-1) of R ¹ ~ R ^4, and p is the formula (A-1) are each as defined in R ¹ ~ R ⁴ and p.

[Formula 5]

X in formula (B-2) represents -CH=CH- or -CH ₂ CH ₂ -. Formula (B-2) in R ^5, R ⁶ and p have the formula (A-2) are each as defined in R ^5, R ⁶ and p.

The content of the structural unit derived from the norbornene skeleton-containing monomer having a polar group (preferably the total amount of the structural unit represented by formula (B-1) and the structural unit represented by formula (B-2)) is a cycloolefin resin It can be set as 50-100 mass% with respect to all the structural units which comprise.

It is preferable that the weight average molecular weight (Mw) of the cycloolefin resin which has a polar group is 20,000-300,000. When the weight average molecular weight (Mw) of the cycloolefin-based resin having a polar group is within the above range, the film-forming property is not poorly impaired while imparting sufficient mechanical strength to the film. The weight average molecular weight (Mw) of the cycloolefin resin having a polar group is more preferably 40,000 to 200,000 from the above viewpoint. The weight average molecular weight (Mw) can be measured by the method similar to the above.

The glass transition temperature (Tg) of the cycloolefin-based resin having a polar group is usually 110°C or higher, preferably 110 to 350°C, more preferably 120 to 250°C, and particularly preferably 120 to 220°C. Do. When the glass transition temperature (Tg) is 110°C or higher, it is preferable because deformation due to use under high-temperature conditions or secondary processing such as coating and printing is suppressed. Moreover, when the glass transition temperature (Tg) is 350 degreeC or less, since resin deterioration by heat at the time of molding processing or molding processing is suppressed, it is preferable.

Among them, a (meth)acrylic resin or a cycloolefin resin having a polar group is preferable in view of low hygroscopicity or one point.

(Other ingredients)

The raw material of the optical film may further contain other components other than the above, if necessary. Examples of other components include elastic particles, mat agents, ultraviolet absorbers, antioxidants, and the like. In particular, when the matrix resin is a (meth)acrylic resin, in order to impart flexibility to the obtained film, it is preferable that the raw material of the optical film further contains elastic particles. Examples of the elastic particles include rubber particles and thermoplastic elastomer particles.

《Rubber Particle》

The rubber particles are a graft copolymer containing a rubber-like polymer (crosslinked polymer).

Examples of the rubbery polymer include butadiene-based crosslinked polymer, (meth)acrylic crosslinked polymer, and organosiloxane-based crosslinked polymer. Among them, the difference in refractive index with the methacrylic resin is small, and from the viewpoint that transparency of the optical film is not poorly impaired, a (meth)acrylic crosslinked polymer is preferable, and an acrylic crosslinked polymer (acrylic rubber polymer) is more preferable.

That is, it is preferable that the rubber particles are an acrylic graft copolymer containing an acrylic rubber polymer (a). The acrylic graft copolymer containing the acrylic rubber polymer (a) may be a core-shell particle having a core portion containing the acrylic rubber polymer (a) and a shell portion covering the core portion. The core-shell particle is a multistage polymer obtained by polymerizing at least one or more stages of a monomer mixture (b) containing a methacrylic acid ester as a main component in the presence of an acrylic rubber polymer (a). Polymerization can be carried out by an emulsion polymerization method.

About acrylic rubber polymer (a):

The acrylic rubber polymer (a) is a crosslinked polymer containing an acrylic acid ester as a main component.

The acrylic rubber-like polymer (a) is a monomer mixture (a') containing an acrylic acid ester and an optional monomer copolymerizable therewith, and a polytube having two or more non-conjugated reactive double bonds (radical polymerizable groups) per molecule. It is a crosslinked polymer obtained by polymerizing a functional monomer. The acrylic rubber polymer (a) may be obtained by polymerizing all of these monomers by mixing them, or may be obtained by polymerizing two or more times by changing the monomer composition.

The acrylic acid ester is preferably an alkyl acrylate ester having 1 to 12 carbon atoms of an alkyl group such as methyl acrylate and butyl acrylate. One type may be sufficient as an acrylic acid ester, and two or more types may be sufficient as it. From the viewpoint of making the glass transition temperature of the rubber particles into -15°C or less, it is preferable that the acrylic acid ester contains at least an acrylate alkyl ester having 4 to 10 carbon atoms.

The content of the acrylic acid ester is preferably 50 to 100% by mass, more preferably 60 to 99% by mass, and still more preferably 70 to 99% by mass with respect to 100% by mass of the monomer mixture (a'). When the content of the acrylic ester is 50% by weight or more, it is easy to impart sufficient toughness to the film.

Examples of the copolymerizable monomer include methacrylic acid esters such as methyl methacrylate; Styrene, such as styrene and methyl styrene; And unsaturated nitriles such as acrylonitrile and methacrylonitrile.

Examples of polyfunctional monomers include allyl (meth)acrylate, triallyl cyanurate, triallyl isocyanurate, diallylphthalate, diallylmaleate, divinyl adipate, divinylbenzene, ethylene glycol di(meth) ) Acrylate, diethylene glycol (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylol methane tetra (meth) acrylate, dipropylene glycol di (meth) ) Acrylate, polyethylene glycol di (meth) acrylate is included.

It is preferable that it is 0.05-10 mass %, and, as for content of a polyfunctional monomer, it is more preferable that it is 0.1-5 mass% with respect to the total 100 mass% of the monomer mixture (a'). When the content of the polyfunctional monomer is 0.05% by mass or more, it is easy to increase the degree of crosslinking of the acrylic rubber-like polymer (a) obtained, so that the hardness and rigidity of the obtained film are not excessively impaired, and when the content is 10% by mass or less, the toughness of the film is good. Not inhibited.

For the monomer mixture (b):

The polymer of the monomer mixture (b) is a graft component for the acrylic rubber polymer (a). The monomer mixture (b) contains methacrylic acid ester as a main component.

The methacrylic acid ester is preferably an alkyl methacrylate ester having 1 to 12 carbon atoms of an alkyl group such as methyl methacrylate. The number of methacrylic acid esters may be one or two or more.

The content of the methacrylic acid ester is preferably 50% by mass or more with respect to 100% by mass of the monomer mixture (b). When the content of the methacrylic acid ester is 50% by mass or more, the hardness and rigidity of the resulting film can be prevented from deteriorating. In addition, from the viewpoint of enhancing the affinity with a solvent such as methylene chloride, the content of the methacrylic acid ester is more preferably 70% by mass or more, further preferably 80% by mass or more with respect to 100% by mass of the monomer mixture (b). Do.

The monomer mixture (b) may further contain other monomers as necessary. Examples of other monomers include acrylic acid esters such as methyl acrylate, ethyl acrylate, and n-butyl acrylate; (Meth)acrylic monomers having an alicyclic structure, a heterocyclic structure or an aromatic group such as benzyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and phenoxyethyl (meth)acrylate ((meth)acrylic monomers containing a ring structure ) Is included.

About acrylic graft copolymer:

The graft ratio (mass ratio of the graft component to the acrylic rubber-like polymer (a)) in the acrylic graft copolymer is preferably 10 to 250%, more preferably 25 to 200%, and 40 to 200%. It is more preferable and it is still more preferable that it is 60-150%. When the graft ratio is 10% or more, the ratio of the shell portion is not too small, so that the hardness and rigidity of the film are hardly impaired. When the graft ratio of the acrylic graft copolymer is 250% or less, since the proportion of the acrylic rubber polymer (a) is not too small, the effect of improving the toughness and brittleness of the film is hardly impaired.

The graft ratio of the acrylic graft copolymer is measured by the following method.

1) 2 g of an acrylic graft copolymer was dissolved in 50 ml of methyl ethyl ketone, and centrifuged for 1 hour at a rotational speed of 30000 rpm and a temperature of 12°C using a centrifugal separator (manufactured by Hitachi Industrial Machinery Co., Ltd., CP60E), Separation into insoluble and soluble content (a total of 3 sets of centrifugal separation work).

2) The weight of the obtained insoluble matter is applied to the following formula, and the graft ratio is calculated.

Graft rate (%) = [{(weight of methyl ethyl ketone insoluble content) -(weight of acrylic rubber polymer (a))}/(weight of acrylic rubber polymer (a))] × 100

《Thermoplastic elastomer particle》

Examples of the thermoplastic elastomer constituting the thermoplastic elastomer particles include styrene-based elastomers, olefin-based elastomers, urethane-based elastomers, polyester-based elastomers, polyamide-based elastomers, and silicone-based elastomers.

(Styrene-based elastomer)

The styrenic elastomer may be a copolymer of styrene and a conjugated solution of butadiene or isoprene and/or a hydrogenated diene thereof. The styrenic elastomer is a block copolymer having styrene as a hard segment and conjugated diene as a soft segment, and does not require a vulcanization step, and is preferably used. Further, the hydrogenated one has high thermal stability, and is more preferably used.

Examples of the styrene-based elastomer include styrene-butadiene-styrene block polymer, styrene-isoprene-styrene block polymer, styrene-ethylene-butylene-styrene block polymer, styrene-ethylene-propylene-styrene block polymer, styrene-isobutylene- And styrene block copolymers. Among them, a styrene-ethylene-butylene-styrene block copolymer, a styrene-ethylene-propylene-styrene block copolymer, or a styrene-isobutylene-styrene block copolymer is preferable.

As a component constituting the styrene-based elastomer, in addition to styrene, styrene derivatives such as α-methylstyrene, 3-methylstyrene, 4-propylstyrene, and 4-cyclohexylstyrene can be further used.

Examples of commercially available styrenic elastomers include Tuffrene, Solprene T, Asaprene T, Toughtech (above, manufactured by Asahi Chemicals Chemical Co., Ltd.), Elastomer AR (manufactured by Aaron Chemical Co., Ltd.), Clayton D, Clayton G, and Kari Flex (Lee Sang, manufactured by Clayton Polymer Japan Co., Ltd.), JSR-TR, TSR-SIS, DYNARON (manufactured by JSR Corporation), Denka STR (manufactured by Denka Corporation), Quintec (manufactured by Nippon Xeon Corporation), TPE-SB Series ( Sumitomo Chemical Co., Ltd.), Rabaron (Mitsubishi Chemical Co., Ltd. product), Sefton, Hybra (Lee Sang, Kuraray Co., Ltd. product), a rheostomer, Actimer (above, Riken Technos Co., Ltd. product), etc. are mentioned.

As for the refractive index of the styrene-based elastomer, it is preferable that the absolute value of the difference in refractive index with the (meth)acrylic resin is 0.020 to 0.036. In the case of using a hydrogenated styrene-based elastomer, when the amount of the styrene component (styrene conversion ratio) of the elastomer is 1% by mass or more and less than 40% by mass, it is easy to adjust the refractive index difference within the above range with respect to the (meth)acrylic resin.

(Olefin elastomer)

The olefin elastomer is a copolymer of an α-olefin having 2 to 20 carbon atoms such as ethylene, propylene, 1-butene, 1-hexene, and 4-methylpentene. Examples of the olefinic elastomer include ethylene-propylene copolymer (EPR), ethylene-propylenediene copolymer (EPDM), and dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylenenorbornene , Ethylidene norbornene, butadiene, isoprene, and other non-conjugated dienes having 2 to 20 carbon atoms and α-olefin copolymers. Moreover, carboxy-modified NBR obtained by copolymerizing methacrylic acid with a butadiene-acrylonitrile copolymer can be mentioned. Specifically, ethylene/α-olefin copolymer rubber, ethylene/α-olefin/non-conjugated diene copolymer rubber, propylene/α-olefin copolymer rubber, and butene/α-olefin copolymer rubber may be mentioned.

(Urethane elastomer)

The urethane-based elastomer includes a hard segment composed of low-molecular ethylene glycol and diisocyanate, and a soft segment composed of a high-molecular (long chain) diol and diisocyanate. As a polymer (long-chain) diol, polypropylene glycol, polytetramethylene oxide, poly(1,4-butylene adipate), poly(ethylene/1,4-butylene adipate), polycaprolactone, poly(1) ,6-hexylene carbonate), poly(1,6-hexylene neopentylene adipate), and the like. The number average molecular weight of the polymer (long chain) diol is preferably 500 to 10,000. In addition to ethylene glycol, single-chain diols such as propylene glycol, 1,4-butanediol, and bisphenol A can be used, and the number average molecular weight of the single-chain diol is preferably 48 to 500.

(Polyester-based elastomer)

The polyester elastomer is obtained by polycondensing a dicarboxylic acid or a derivative thereof and a diol compound or a derivative thereof. Examples of dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids having 2 to 20 carbon atoms such as adipic acid, sebacic acid, and dodecanedicarboxylic acid. And alicyclic dicarboxylic acids such as acids and cyclohexanedicarboxylic acid. Examples of diol compounds include aliphatic diols and alicyclic diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, and 1,4-cyclohexanediol, bisphenol A, bis- And aromatic cyclic diols such as (4-hydroxyphenyl)-methane and bis-(4-hydroxy-3-methylphenyl)-propane.

Further, a multi-block copolymer having a hard segment of an aromatic polyester (eg, polybutylene terephthalate) and a soft segment of an aliphatic polyester (eg, polytetramethylene glycol) may be used.

(Polyamide elastomer)

Polyamide elastomers are two types: a polyether block amide type having a hard segment of polyamide and a soft segment of polyether, and a polyether block amide type having a hard segment of polyamide and a soft segment of polyester. It is roughly divided into. As the polyamide, polyamide-6, 11, 12, etc. are used, and as the polyether, polyoxyethylene, polyoxypropylene, polytetramethylene glycol, and the like are used.

(Silicone elastomer)

The silicone-based elastomer contains organopolysiloxane as a main component, and examples thereof include polydimethylsiloxane-based, polymethylphenylsiloxane-based, and polydiphenylsiloxane-based.

Among these thermoplastic elastomers, it is preferable to contain an aromatic vinyl-based compound as a copolymerization component, and styrene-based elastomer particles are particularly preferable from the viewpoint of having a uniform particle diameter.

About physical properties:

It is preferable that it is 100-400 nm, and, as for the average particle diameter of an elastic body particle, it is more preferable that it is 150-300 nm. When the average particle diameter is 100 nm or more, it is easy to impart sufficient toughness to the film, and when it is 400 nm or less, the transparency of the film is not easily reduced.

It is preferable that the glass transition temperature (Tg) of the elastic body particles is -10°C or less. When the glass transition temperature (Tg) of the elastic body particles is -10°C or less, it is easy to impart sufficient toughness to the film. It is more preferable that it is -15 degreeC or less, and, as for the glass transition temperature (Tg) of an elastic body particle, it is still more preferable that it is -20 degreeC or less. The glass transition temperature (Tg) of the elastic body particles is measured by the same method as described above.

When the elastic body particles are rubber particles, the glass transition temperature (Tg) of the rubber particles can be adjusted according to, for example, the monomer composition constituting the core portion or the shell portion, the mass ratio of the core portion and the shell portion (graft ratio), and the like. In order to lower the glass transition temperature (Tg) of the rubber particles, as described later, for example, the number of carbon atoms of the alkyl group in the monomer mixture (a') constituting the acrylic rubber-like polymer (a) of the core portion is 4 It is preferable to increase the mass ratio of the total of the acrylic acid ester/copolymerizable monomers above (eg, 3 or more, preferably 4 or more and 10 or less).

It is preferable that it is 0-30 mass% with respect to the matrix resin, and, as for content of an elastic body particle, it is more preferable that it is 2-20 mass %. When the content of the elastic body particles is 2% by mass or more, it is easy to impart sufficient toughness to the obtained film, and when it is 30% by mass or less, it is easy to suppress an increase in internal haze.

《Matte》

The raw material of the optical film may further contain organic fine particles other than inorganic fine particles or elastomer particles as a mat agent from the viewpoint of imparting sliding properties to the obtained film.

Examples of the inorganic material constituting the inorganic fine particles include silicon dioxide (SiO ₂ ), titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate. , And calcium phosphate are contained, and from the viewpoint of reducing the increase in haze, it is preferably silicon dioxide. The organic fine particles are resin particles having a glass transition temperature (Tg) of preferably 80°C or higher. Among them, organic fine particles are preferred from the viewpoint of easily enhancing the toughness of the film.

(menstruum)

The solvent used for dissolution or dispersion of the raw material of the optical film is an organic solvent, and contains at least a good solvent capable of dissolving the matrix resin. Examples of the good solvent include chlorine-based organic solvents such as methylene chloride; Non-chlorine-based organic solvents such as methyl acetate, ethyl acetate, acetone, and tetrahydrofuran are included. Among them, methylene chloride is preferred.

The solvent may further contain a poor solvent. Examples of poor solvents include linear or branched aliphatic alcohols having 1 to 4 carbon atoms. When the ratio of alcohol in the dope increases, the film-like substance is likely to gel, and peeling from the metal support is likely to be facilitated. Examples of linear or branched aliphatic alcohols having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Among these, ethanol is preferable because the stability and boiling point of the dope are also relatively low, and the drying property is also improved.

In addition, in the present invention, it is preferable not to include a step of further crushing or pulverizing a film piece between 1) a half-reinforced crushing step and 2) a dope preparation step. This is for suppressing fusion bonding or thermal deterioration between film pieces due to heat generation when further crushing or pulverizing the film pieces.

3) film forming process

Then, the obtained dope is flexible on a support. The casting of dope can be performed by discharging it from the casting die.

Subsequently, after appropriately evaporating the solvent in the dope cast on the support (after drying), it is peeled off from the support to obtain a film-like material.

The residual solvent amount of the dope when peeling from the support (the residual solvent amount of the film-like substance at the time of peeling) is, for example, preferably 25 mass% or more, more preferably 30 to 37 mass%, and 30 to 35 mass% It is more preferable to be. When the residual solvent amount at the time of peeling is 25 mass% or more, it is easy to volatilize the solvent from the film-like substance after peeling at once. Moreover, when the amount of residual solvent at the time of peeling is 37 mass% or less, it can suppress that the film-like material by peeling extends too much.

The residual solvent amount of dope at the time of peeling is defined by the following formula. The same is the case below.

Amount of residual solvent of dope (mass%) = (mass before heat treatment of dope-mass after heat treatment of dope)/mass after heat treatment of dope × 100

In addition, the heat treatment at the time of measuring the amount of residual solvent means a heat treatment at 140°C for 15 minutes.

The amount of residual solvent at the time of peeling can be adjusted according to the drying temperature or drying time of the dope on the support, the temperature of the support, and the like.

4) Other processes

The manufacturing method of the optical film of the present invention may further include other steps other than the steps 1) to 3) above, as necessary. Examples of other processes include 4-1) a process of storing and storing a film piece obtained after crushing (storage/storing process), and 4-2) an optical film by drying the obtained film-like material while stretching as necessary. A step (drying/stretching step), 4-3) A step (winding up step) of winding up the obtained optical film is included.

4-1) It is preferable to perform the storage/storage process between 1) a half ash crushing process and 2) a dope preparation process. It is preferable to perform 4-2) drying/stretching process after 3) film forming process. It is preferable to perform 4-3) winding-up process after 4-1) drying and extending process.

4-1) Storage and storage process

You may store and store the film piece obtained in the said 1) half-material crushing process once in a storage tank or the like.

4-2) Drying and stretching process

Drying may be carried out in one step or in multiple steps. Moreover, you may perform drying, extending|stretching as needed.

Stretching may be performed according to the required optical properties, and it is preferable to stretch in at least one direction, stretching in two directions orthogonal to each other (e.g., the width direction of the film-like material (TD direction), and Biaxial stretching in the conveyance direction (MD direction) may be sufficient.

From the viewpoint of using the optical film as a retardation film for IPS, for example, the draw ratio can be 1.01 to 2 times. The draw ratio is defined as (size in the stretching direction of the film after stretching)/(size in the stretching direction of the film before stretching). In addition, when performing biaxial stretching, it is preferable to set it as the said stretching ratio for each of the TD direction and the MD direction.

In addition, the in-plane slow axis direction (the direction in which the refractive index becomes maximum in the plane) of the optical film is usually a direction in which the draw ratio becomes maximum.

The drying temperature (stretching temperature) at the time of stretching, when the glass transition temperature of the matrix resin is Tg, is preferably (Tg-65) to (Tg+60)°C, and (Tg-50)°C to (Tg+) It is more preferable that it is 50) degreeC, and it is still more preferable that it is (Tg-30)-(Tg+50) degreeC. When the stretching temperature is (Tg-65)°C or higher, since it is easy to appropriately volatilize the solvent, it is easy to adjust the stretching tension to an appropriate range, and when it is (Tg+60)°C or less, the solvent does not volatilize excessively. It does not hinder well. When the matrix resin is a (meth)acrylic resin, the stretching temperature can be, for example, 90°C or higher.

The stretching temperature is (a) when drying by a non-contact heating type such as a tenter stretching machine, an ambient temperature such as the temperature inside the stretching machine or hot air temperature, and (b) when drying by a contact heating type such as a heat roller, contact It can measure as any temperature among the temperature of a heating part or (c) the surface temperature of a film-like material (a surface to be dried). Among them, (a) it is preferable to measure the ambient temperature such as the temperature inside the drawing machine or the hot air temperature.

It is preferable that the amount of residual solvent in the film-like material at the start of stretching is about the same as the amount of residual solvent in the film-like material at the time of peeling, for example, it is preferably 20 to 30 mass%, more preferably 25 to 30 mass%. desirable.

The stretching in the TD direction (width direction) of the film-like material can be performed by, for example, a method of fixing both ends of the film-like material with a clip or a pin, and widening the gap between the clip and the pin in the traveling direction (tenter method). The stretching of the film-like material in the MD direction can be performed by, for example, a method (roll method) that provides a circumferential speed difference to a plurality of rolls and uses the roll circumferential speed difference therebetween.

From the viewpoint of further reducing the amount of residual solvent, it is preferable to again (post-dry) the film-like material obtained after stretching. For example, it is preferable to dry again while conveying the film-like material obtained after stretching by a roll or the like (with a certain tension applied).

The drying temperature at this time (drying temperature when not stretching or drying temperature after stretching) is preferably (Tg-30) to (Tg+30)°C when the glass transition temperature of the matrix resin is Tg, It is more preferable that it is (Tg-20)-Tg degreeC. When the drying temperature is (Tg-30)°C or higher, preferably (Tg-20)°C or higher, it is easy to increase the volatilization rate of the solvent from the film-like material after stretching, so that the drying efficiency is easy to increase. When the drying temperature is (Tg+30)°C or less, preferably Tg°C or less, deformation of the tin phase due to elongation of the film-like material can be highly suppressed. As for the drying temperature, as described above, (a) it is preferable to measure the ambient temperature such as the temperature inside the drawing machine or the hot air temperature.

4-3) Winding process

And the obtained optical film is wound up in the longitudinal direction (direction perpendicular to the width direction) of the film using a winder. Thereby, an optical film wound in a roll shape around a core, that is, a roll body of an optical film can be obtained.

The winding method is not particularly limited, and may be a constant torque method, a constant tension method, a taper tension method, or the like.

When winding up the optical film, the winding tension can be about 50 to 170 N. The winding length is not particularly limited, and may be 3000 m or more, preferably 3500 to 8000 m.

Among the steps 1) to 4) above, for example, between the 4-2) drying/stretching step and the 4-3) winding step, the obtained optical film is in the width direction as necessary from the viewpoint of adjusting to a predetermined width. There are cases where both ends of the are cut off. Moreover, in the 4-3) winding process, when a winding defect or the like occurs, a defective product that does not satisfy the standard as a product may be generated. In this way, the cut-out material of the optical film cut out during the production of the optical film, the defective product that does not become a product, and the like can be reused as the aforementioned half-material.

The optical film obtained in this way is used as an optical member in a display device such as a liquid crystal display device or an organic EL display device. Examples of the optical member include a polarizing plate protective film (including a phase difference film and a brightness enhancing film), a transparent substrate, and a light diffusion film. Especially, it is preferable that the optical film of this invention is used as a polarizing plate protective film.

2. Optical film

The optical film of this invention is obtained by the manufacturing method of the said optical film. That is, the optical film contains a (meth)acrylic resin and an elastic body particle, or contains a cyclorepine resin having a polar group. These optical films may further contain other components as described above as necessary.

(Residual solvent)

Since the optical film is produced by the solution film forming method as described later, it may contain a residual solvent derived from the dope solvent used by the solution film forming method.

It is preferable that it is 700 ppm or less with respect to an optical film, and, as for the amount of a residual solvent, it is more preferable that it is 30-700 ppm. The content of the residual solvent can be adjusted according to the drying conditions of the dope cast on the support in the manufacturing process of the optical film described later.

The amount of residual solvent in the optical film can be measured by headspace gas chromatography. In the headspace gas chromatography method, a sample is enclosed in a container, heated, and the gas in the container is rapidly injected into a gas chromatograph in a state full of volatile components in the container, and the compound is identified by mass analysis. It is to quantify the volatile components. In the headspace method, it is possible to observe all peaks of volatile components using a gas chromatograph, and also quantify volatile substances and monomers with high accuracy by using an analysis method using electromagnetic interaction. can do.

(YI)

It is preferable that it is 2.0 or less, as for the yellow index (YI) of an optical film, it is more preferable that it is 1.5 or less, and it is still more preferable that it is 1.2 or less. When the YI of the optical film is within the above range, there is little coloration resulting from thermal deterioration of the film piece in the manufacturing process of the film, and it is preferable as an optical film.

The yellow index (YI) can be measured by the method described in JIS K-7105-6.3. Specifically, using a spectrophotometer U-3200 manufactured by Hitachi High Technology Co., Ltd. and an attached saturation calculation program, the three stimulus values X, Y, and Z of the color are measured. The obtained measured value is applied to the following formula to calculate a yellow index value.

Yellow Index (YI) = 100(1.28X ― 1.06Z)/Y

YI of the optical film can be adjusted according to the crushing conditions in the manufacturing process of the optical film. In order to lower the YI of the optical film, it is preferable to reduce the load at the time of crushing or to reduce heat generation by performing heat removal (cooling), for example, crushing under conditions in which the bulk density falls within the above range.

(Internal haze)

It is preferable that the optical film has high transparency. It is preferable that it is 0.05% or less, and, as for the haze of an optical film, it is more preferable that it is 0.03% or less. The internal haze can be measured according to JIS K-6714 with a haze meter (HGM-2DP, Suga tester) at 25°C and 60%RH of a sample 40 mm×80 mm.

(Phase difference Ro and Rt)

From the viewpoint of using the optical film as a retardation film for IPS mode, for example, the retardation Ro in the in-plane direction measured in an environment of a measurement wavelength of 550 nm and 23°C 55% RH is preferably 0 to 10 nm, It is more preferable that it is 0-5 nm. It is preferable that it is -20-20 nm, and, as for the retardation Rt in the thickness direction of an optical film, it is more preferable that it is -10-10 nm.

Ro and Rt are each defined by the following formula.

Equation (2a): Ro = (nx ― ny) × d

Equation (2b): Rt = ((nx + ny)/2 ― nz) × d

(In the formula,

nx represents the refractive index of the film in the in-plane slow axis direction (the direction in which the refractive index becomes maximum),

ny represents the refractive index in the direction orthogonal to the in-plane slow axis of the film,

nz represents the refractive index in the thickness direction of the film,

d represents the thickness (nm) of the film)

The in-plane slow axis of an optical film means the axis at which the refractive index becomes the largest in the film surface. The in-plane slow axis of the optical film can be confirmed by an automatic birefringence meter exo scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Exo Matrix).

Ro and Rt can be measured by the following method.

1) The optical film is humidified in an environment of 23°C and 55%RH for 24 hours. The average refractive index of this film is measured with an Abbe refractometer, and the thickness d is measured using a commercially available micrometer.

2) The retardation Ro and Rt of the film after humidity control at a measurement wavelength of 550 nm were respectively obtained at 23° C. of 55% RH using an automatic birefringence meter exo scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Exo Matrix). Measured under the environment.

The retardation Ro and Rt of the optical film can be adjusted, for example, depending on the type of the matrix resin and stretching conditions. In order to lower the retardation Ro and Rt of the optical film, for example, a matrix resin having a low retardation due to stretching is selected (e.g., a structural unit derived from a monomer having negative birefringence and a monomer having positive birefringence. It is preferable to select a resin having a monomer ratio capable of canceling a phase difference in a structural unit).

(thickness)

The thickness of the optical film can be, for example, 5 to 100 µm, preferably 5 to 40 µm.

3. Polarizer

The polarizing plate of this invention has a polarizer, the optical film of this invention, and the adhesive layer arrange|positioned between them.

3-1. Polarizer

The polarizer is an element that allows only light of a polarization surface in a predetermined direction to pass, and is a polyvinyl alcohol-based polarizing film. Polyvinyl alcohol-based polarizing films include polyvinyl alcohol-based films dyed with iodine and dyed with a dichroic dye.

The polyvinyl alcohol-based polarizing film may be a film dyed with iodine or a dichroic dye after uniaxially stretching the polyvinyl alcohol-based film (preferably a film further subjected to durability treatment with a boron compound); After dyeing the polyvinyl alcohol-based film with iodine or a dichroic dye, it may be a uniaxially stretched film (preferably, a film further subjected to durability treatment with a boron compound). The absorption axis of the polarizer is usually parallel to the maximum stretching direction.

For example, ethylene-modified polyvinyl having an ethylene unit content of 1 to 4 mol%, a polymerization degree of 2000 to 4000, and a saponification degree of 99.0 to 99.99 mol% described in JP 2003-248123 A, JP 2003-342322 A, etc. Alcohol is used.

The thickness of the polarizer is preferably 5 to 30 µm, and more preferably 5 to 20 µm in terms of thinning the polarizing plate.

3-2. Optical film

The optical film of the present invention is disposed on at least one surface of the polarizer (at least the surface facing the liquid crystal cell). The optical film can function as a polarizing plate protective film.

When the optical film of the present invention is disposed only on one surface of the polarizer, another optical film may be disposed on the other surface of the polarizer. Examples of other optical films include commercially available cellulose ester films (e.g., Konica Minoltatech KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC4UE, KC4UEY , KC8UY-HA, KC2UA, KC4UA, KC6UA, KC8UA, KC2UAH, KC4UAH, KC6UAH, and above Konica Minolta Co., Ltd.manufactured, Fujitech T40UZ, Fujitech T60UZ, Fujitech T80UZ, Fujitech TD80UL, Fujitech TD80UL, Fujitech TD80UL , Fujitech R02, Fujitech R06, and above (manufactured by Fujifilm Co., Ltd.), and the like.

The thickness of other optical films may be, for example, 5 to 100 µm, and preferably 40 to 80 µm.

3-3. Adhesive layer

The adhesive layer is disposed between an optical film (or other optical film) and a polarizer. The thickness of the adhesive layer may be, for example, 0.01 to 10 µm, preferably about 0.03 to 5 µm.

3-4. Polarizing plate manufacturing method

The polarizing plate of the present invention can be obtained by bonding a polarizer and the optical film of the present invention through an adhesive. The adhesive may be a completely saponified polyvinyl alcohol aqueous solution (water paste), or an active energy ray-curable adhesive. The active energy ray-curable adhesive may be a photo-radical polymerization-type composition using photo-radical polymerization, a photo-cationic polymerization-type composition using photo-cation polymerization, or a combination thereof.

4. Liquid crystal display

The liquid crystal display device of the present invention includes a liquid crystal cell, a first polarizing plate disposed on one surface of the liquid crystal cell, and a second polarizing plate disposed on the other surface of the liquid crystal cell.

The display mode of the liquid crystal cell is, for example, STN (Super-Twisted Nematic), TN (Twisted Nematic), OCB (Optically Compensated Bend), HAN (Hybridaligned Nematic), VA (Vertical Alignment, MVA (Multi-domain Vertical Alignment)). , PVA (Patterned Vertical Alignment)), IPS (In-Plane-Switching), and the like. Among them, VA (MVA, PVA) mode and IPS mode are preferred.

One or both of the first and second polarizing plates are the polarizing plates of the present invention. It is preferable that the polarizing plate of this invention is arrange|positioned so that the optical film of this invention may become a liquid crystal cell side.

Example

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these.

1. Materials for optical films and semi-materials

(1) Matrix resin

Resin A: methyl methacrylate (MMA)/N-phenylmaleimide (PMI) copolymer (MMA/PMI = 85/15 (mass ratio), glass transition temperature (Tg): 125°C, weight average molecular weight Mw: 1.5 million )

Resin B: G7810 manufactured by JSR (cycloolefin resin containing a structural unit represented by formula (B-2), refractive index 1.51, weight average molecular weight 140,000, glass transition temperature 170°C)

The glass transition temperature (Tg) and weight average molecular weight (Mw) of resins A and B were measured by the following method.

(Glass transition temperature (Tg))

The glass transition temperature of the resin was measured in accordance with JIS K 7121-2012 using DSC (Differential Scanning Colorimetry: Differential Scanning Calorimetry).

(Weight average molecular weight (Mw))

The weight average molecular weight (Mw) of the resin was measured using gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation) and a column (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL serial manufactured by Tosoh Corporation). 20 mg ± 0.5 mg of a sample was dissolved in 10 ml of tetrahydrofuran and filtered through a 0.45 mm filter. 100 ml of this solution was poured into a column (40° C.), measured at a detector RI temperature of 40° C., and the value converted to styrene was used.

(2) elastomer particles

Rubber Particles R1: Rubber particles prepared by the following method were used.

(Preparation example)

The following components were injected into a glass reactor.

Ion-exchanged water: 125 parts by mass

Boric acid: 0.47 parts by mass

Sodium carbonate: 0.05 parts by mass

Polyoxyethylene lauryl ether phosphoric acid: 0.0042 parts by mass

After sufficiently replacing the inside of the polymerization reactor with nitrogen gas, the internal temperature was set to 80°C, and 97 parts by mass of methyl methacrylate (MMA), 3 parts by mass of butyl acrylate (BA), and 0.17 parts by mass of allyl methacrylate (ALMA), And 25% by mass of a monomer mixture (c1) consisting of 0.065 parts by mass of tertiarydodecylmercaptan (tDM) was added at once to a polymerization reactor. To this, 0.00645 parts by mass of 5% sodium formaldehyde sulfoxylate, 0.0056 parts by mass of ethylenediamine tetraacetate-2-sodium, and 0.0014 parts by mass of ferrous sulfate were added, and after 15 minutes, 0.022 parts by mass of t-butyl hydroperoxide Then, polymerization was continued for another 15 minutes. Then, 0.013 parts by mass of a 2% aqueous sodium hydroxide solution was added.

Then, the remaining 75 mass% of the monomer mixture (c1) was continuously added over 30 minutes. 30 minutes after the completion of the addition, 0.0069 parts by mass of 69% t-butyl hydroperoxide was added, and the mixture was held at the same temperature for 30 minutes to complete polymerization. The polymerization conversion rate was 98%.

The obtained polymer latex was kept at 80°C in a nitrogen stream, and 0.0346 parts by mass of sodium hydroxide and 0.0519 parts by mass of potassium persulfate were added. Thereafter, a mixture consisting of 32.5 parts by mass of the monomer mixture (a1) (BA: 82% by mass, MMA: 18% by mass), 0.97 parts by mass of AIMA, and 0.3 parts by mass of polyoxyethylene lauryl ether phosphoric acid was continuously added over 74 minutes. I did. After that, it was held for 45 minutes to complete polymerization. The average particle diameter of the obtained rubbery polymer was 260 nm, and the polymerization conversion rate was 99%.

After maintaining the obtained rubbery polymer at 80°C, adding 0.0097 parts by mass of potassium persulfate and 0.05 parts by mass of sodium hydroxide, 50 parts by mass of the monomer mixture (b1) (MMA: 90% by mass, BA: 10% by mass) was added to 150 It was added continuously over a minute. After completion of the addition, it was held for 1 hour.

The graft copolymer containing the obtained rubbery polymer was salted out and solidified with magnesium sulfate, washed with water, and dried to obtain a graft copolymer (rubber particles R1) containing a white powdery rubbery polymer. The glass transition temperature (Tg) of the obtained rubber particles R1 was -30°C, the average particle diameter was 380 nm, the graft ratio was about 149%, and the polymerization conversion ratio was 99%.

Thermoplastic elastomer particles E1: TR2827 manufactured by JSR Corporation (styrene/butadiene = 24/76 mass ratio)

(Average particle diameter)

The dispersed particle diameter of the rubber particles R1 or the thermoplastic elastomer particles E1 in the obtained dispersion was measured by a zeta potential/particle size measuring system (ELSZ-2000 ZS manufactured by Otsuka Electronics Co., Ltd.). In addition, the average particle diameter of these particles measured using the zeta potential/particle diameter measurement system (ELSZ-2000 ZS manufactured by Otsuka Electronics Co., Ltd.) is almost identical to the average particle diameter of these particles measured by TEM observation of an optical film.

2. Manufacturing and evaluation of optical films using semi-materials

[Example 1]

2-1. Preparation of rebuttal

(Preparation of rubber particle dispersion)

11.3 parts by mass of rubber particles R1 and 200 parts by mass of methylene chloride were stirred and mixed for 50 minutes with a dissolver, and then dispersed under conditions of 1500 rpm using a Milder disperser (manufactured by Taiheiyo Machinery Co., Ltd.) to disperse the rubber particle dispersion. Got it.

(Preparation of dope)

Next, a dope of the following composition was prepared. First, methylene chloride and ethanol were added to a pressure dissolution tank. Then, it injected|threw-in stirring the (meth)acrylic resin A into a pressure dissolution tank. Next, the above prepared rubber particle dispersion was added, and it was completely dissolved while stirring. The viscosity of the obtained solution was 16000 mmPa·s, and the moisture content was 0.50%. This was filtered with a filtration flow rate of 300 L/m 2·h and a filtration pressure of 1.0×10 ⁶ Pa using SHP150 manufactured by Rocky Techno Co., Ltd. to obtain a dope.

(Meth)acrylic resin A: 100 parts by mass

Methylene chloride: 220 parts by mass

Ethanol: 35 parts by mass

Rubber particle dispersion: 200 parts by mass

(Production and semi-product)

Using an endless belt casting apparatus, the dope was uniformly cast on a stainless steel belt support at a temperature of 30° C. and a width of 1900 mm. The temperature of the stainless steel belt was controlled at 28°C. The conveyance speed of the stainless steel belt was set to 20 m/min.

On the stainless steel belt support, the solvent was evaporated until the amount of residual solvent in the cast (cast) dope became 30 mass %. Subsequently, it peeled from the stainless steel belt support body with a peeling tension of 128 N/m, and the film-like substance was obtained (the amount of residual solvent of a film-like substance at the time of peeling was 30 mass %). While conveying the peeled film with many rollers, the obtained film-like material was stretched 30% in the width direction under the conditions of (Tg+15) degreeC (140 degreeC in this example) with a tenter. The residual solvent amount of the film-like substance at the start of stretching was 10% by mass. After that, it was dried again at (Tg-20) degreeC, conveying with a roll, and the film for half-materials with a film thickness of 20 micrometers was obtained. The obtained film for half material was slit with a laser cutter to obtain a half material.

2-2. Shredding

The obtained half-material was crushed using a crusher shown in Fig. 2 to obtain a film piece having a bulk density of 0.3 g/cm 3. Crushing by a crusher was performed under the conditions shown in Table 1. In addition, as shown in FIG. 2, as for the air blowing from the side, in a cross section orthogonal to the axial direction of the rotation axis of the rotation blade 130B, the cross angle of the supply direction C of the cooling gas with respect to the supply direction F of the half material It carried out so that it might become 90 degrees. In addition, the position of the ventilation port 160 was set to the same height as the rotation axis of the rotation blade 130B in the supply direction F of the half-material. The temperature of the cooling gas (air) was 20°C, and the flow rate was 15 Nm 3 /hour. In addition, the bulk density of the obtained film piece was measured according to JIS Z 8807.

2-3. Preparation of dope containing half ash

The obtained film piece was added to a pressure dissolution tank for preparing dope. The addition of the film piece was performed so that it might be 50 mass% with respect to the raw material (total of the film piece and the pure material) added to the solvent. And the following components were mixed and stirred to prepare a half-material-containing dope.

(Meth)acrylic resin A: 50 parts by mass

Film piece: 55 parts by mass

Methylene chloride: 220 parts by mass

Ethanol: 35 parts by mass

Rubber particle dispersion: 100 parts by mass

2-4. Production

Except having used the obtained dope, it carried out similarly to (film formation) of said 2-1, and obtained the optical film of 2.3 m in length in the width direction, 7000 m in length, and a film thickness of 20 micrometers.

[Examples 2 to 6 and 10, Comparative Examples 1 to 4]

Except having changed the crushing conditions of the half-material in said 2-2 as shown in Table 1, it carried out similarly to Example 1, and obtained the optical film with a film thickness of 20 micrometers. In addition, as for the blowing from the downstream side (the supply of the cooling gas), as shown in FIG. 1, the supply direction C of the cooling gas becomes counter-current (the opposite direction) with respect to the supply direction F of the half material, and the cross angle It carried out so that it might become 30 degrees.

[Examples 7 to 9]

Except having changed the raw material as shown in Table 1, it carried out similarly to Example 2, and obtained the optical film of 20 micrometers in thickness.

2-5. evaluation

Foreign matter failure and yellow index (YI) of the optical films obtained in Examples 1 to 10 and Comparative Examples 1 to 4 were evaluated by the following method.

(Foreign matter failure)

The surface of the obtained film was observed with an optical microscope (50 times), and the degree of the gel-like foreign matter having a diameter of 0.02 mm or more per 100 cm 2 was counted. The smaller the number of gel-like foreign matters, the less undissolved matter of the semi-material.

◎: The number of gel-like foreign substances is 0 to 3

○: The number of gel-like foreign substances is 4 to 10

△: The number of gel-like foreign substances is 11 to 25

×: the number of foreign substances in the gel form is 26 or more

If it was △ or more, it was judged as good.

In addition, for the gel-like foreign matter, 10 mg of a finely ground optical film was put in an aluminum pan, and heated at 260° C. for 60 minutes under an N2 flow using TG/DTA6200 (manufactured by SII Nanotechnology Co., Ltd.). . The heated aluminum pan containing the optical film was placed in a 10 ml volumetric flask, and this was weighed up with THF (tetrahydrofuran) until it became 10 ml. And after storage at 23 degreeC for 24 hours, as a result of visually observing the dissolution state of the optical film in an aluminum pan, it was observed as a dissolution residue (gel).

(Yellow Index (YI))

The yellow index (YI) was measured by the method described in JIS K-7105-6.3. Specifically, using a spectrophotometer U-3200 manufactured by Hitachi High Technology Co., Ltd. and an attached saturation calculation program, the three stimulus values X, Y, and Z of the color were measured. The obtained measured value was applied to the following formula to calculate a yellow index value.

Yellow Index (YI) = 100(1.28X ― 1.06Z)/Y

◎: YI is 1.2 or less

○: YI is more than 1.2 and less than 1.5

△: YI is more than 1.5 and less than 2.0

×: YI exceeds 2.0

If it is more than △, coloration was small and it was judged as good.

Table 1 shows the manufacturing conditions and evaluation results of the optical films obtained in Examples 1-10 and Comparative Examples 1-4.

As shown in Table 1, it was found that all of the optical films of Examples 1 to 10 obtained by using the crushed film piece under conditions in which the bulk density falls within a predetermined range had few foreign substances and little coloring.

In particular, it can be seen that by using the crushed film piece under the condition that the bulk density is 0.34 g/m 3 or less, foreign matter and coloring of the obtained optical film can be reduced (Examples 1 to 3 and 4 to 5 prepare). It is considered that this is because the load of the crushing treatment became smaller, so that fusion of the film piece due to heat generation at the time of crushing and thermal deterioration could be suppressed.

Moreover, it turns out that the bulk density of the obtained film piece becomes lower than that performed from the side side by performing blowing (supply of the cooling gas) from the downstream side of the crushing chamber. And it can be seen that the number of foreign substances in the obtained optical film decreases further (comparation of Examples 1 and 2). This is because, by performing blowing from the downstream side of the crushing chamber, not only can the residence time of the cooling gas be lengthened, but also the heat exchange efficiency is increased, so that the inside of the crushing chamber can be efficiently cooled, and the fusion of film pieces is further suppressed. I think it is because it can be done.

On the other hand, it can be seen that all of the optical films of Comparative Example 1 using the crushed film piece under the condition that the bulk density exceeds 0.4 g/m 3 contain many foreign substances. This is because, as the size (average particle diameter) of the film piece became too small, the load at the time of crushing became too large, so that the film piece was fused by heat generation at the time of crushing, and during dope preparation, undissolved substances that were not dissolved in the solvent increased. It seems to be because of it. Moreover, it turns out that coloring also occurs in the optical film of Comparative Example 1. This is considered to be because the film piece is thermally deteriorated by heat generation at the time of crushing.

On the other hand, it can be seen that the optical films of Comparative Examples 2 and 3 using the crushed film piece under the condition that the bulk density is less than 0.02 g/m 3 also contain many foreign substances. This is considered to be because the size (average particle diameter) of the film piece was too large, and not only did not easily dissolve in the solvent, but also the large film pieces were aggregated to cause poor dissolution.

In addition, the reason that the bulk density of the film piece obtained in Comparative Example 2 is lower than the bulk density of the film piece obtained in Example 10 is that when the rotational speed is low, heat generation enough to cause fusion is not easily generated (in the absence of blowing air) It is considered that this is because the residence time of the film piece is shortened and the influence of the increase in the size of the film piece is large. On the other hand, the reason that the bulk density of the film piece obtained in Comparative Example 4 is higher than the bulk density of the film piece obtained in Example 2 is that when the rotational speed is high, heat generation enough to cause fusion is likely to occur (because there is no blowing air. ) It is thought that this is because the influence of fusion by heat generation became larger than the effect of shortening the residence time.

This application claims priority based on Japanese Patent Application No. 2019-068677 for which it applied on March 29, 2019. All of the contents described in the application specification and drawings are incorporated in the specification of the present application.

Advantageous Effects of Invention According to the present invention, in the manufacturing method of an optical film using a semi-material, it is possible to provide a method for producing an optical film in which undissolved matter of the semi-material is reduced, and foreign matter failure of the film resulting from it is reduced.

100: shredder
110: shredding chamber
120: supply port
130: crushing mechanism
130A: Fixed blade
130B: rotating blade
140: outlet
150: screen
160: air outlet
210: Hopper
220: supply pipe
230: discharge pipe
F: direction of supply of half material
C: supply direction of cooling gas (airflow direction)

Claims (9)

As a method for producing an optical film containing a (meth)acrylic resin and elastic particles, or a cycloolefin resin having a polar group,
A step of crushing the half-material generated in the manufacturing process of the optical film to obtain a film piece having a bulk density of 0.02 to 0.4 g/cm 3,
A process of preparing a dope by dissolving a raw material containing the film piece in a solvent,
A method for producing an optical film comprising the step of obtaining a film-like material by softening the dope on a support, followed by drying and peeling. The method of claim 1,
The bulk density of the film piece is 0.02 to 0.34 g/cm 3, wherein the method for producing an optical film. The method according to claim 1 or 2,
The average particle diameter measured by the sieving test of the said film piece is 2 to 7.3 mm, The manufacturing method of an optical film. The method according to any one of claims 1 to 3,
The method for producing an optical film, wherein the fraction of the film pieces is sieved through a mesh having an average eye size of 1 mm for 2 minutes and is not more than 10% by mass relative to the total amount of the film pieces before being sieved. The method according to any one of claims 1 to 4,
The crushing of the half-material is carried out by sandwiching the half-material between a fixed blade and a rotating blade, and crushing. The method of claim 5,
The crushing of the half-material is performed while supplying a cooling gas. The method of claim 6,
The supply of the cooling gas is performed in a direction opposite to the supply direction of the half material. The method according to any one of claims 5 to 7,
The rotational speed of the rotating blade is 300 to 800 rpm, the method for producing an optical film. The method according to any one of claims 1 to 8,
The content of the half-material is 10 mass% or more with respect to the raw material, the method for producing an optical film.

Images