JP6764669B2 - Optical film and its manufacturing method - Google Patents

Description

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

Optical transparency, optical homogeneity, and smoothness are required for a polarizing element protective film for protecting a polarizer and an optical film represented by a film substrate for a liquid crystal display device. ..
As a method for producing such an optical film, a melt extrusion method is known in which a resin composition as a film raw material is melted by an extruder and extruded into a film from a die to form a film.
When the film thus obtained is used as a product, the film is wound into a roll. However, there is a problem that the films come into contact with each other inside the wound roll, causing scratches and unevenness defects on the films (hereinafter, blocking-induced defects).

As a method of suppressing this blocking-induced defect, for example, a method of improving the film slipperiness by adding slippery particles having antiblocking property such as silica particles having a specific particle size to the molten resin is known. (See Patent Document 1).
Further, there is also known a method in which both ends of the film are knurled to form an embossed portion to reduce the degree of contact between the films (see Patent Document 2). Patent Document 2 also describes that fine particles that impart slipperiness to the film are added.

Japanese Patent No. 5587209 Japanese Unexamined Patent Publication No. 2009-073154

However, when the film to which the slippery particles are added is subjected to the knurling process, the effect of preventing defects caused by blocking can be obtained, while the knurled portion that maintains the wound state of the film also has the slipperiness. Since the film is held, there is a problem that the roll is unwound (the position of the end face of the roll becomes non-uniform) due to shaking (meandering) during winding the film on the roll or during transportation after winding.

In view of the above situation, the present invention relates to an optical film in which the occurrence of unwinding due to meandering of the film is suppressed while imparting slipperiness to the film by using crosslinked polymer particles, and a method for producing the optical film. The purpose is to provide.

As a result of diligent studies by the present inventor in order to solve the above problems, in an optical film composed of a thermoplastic resin composition containing crosslinked polymer particles and having a nerling processed portion in a part in the width direction, the nerling of the nerling processed portion We have found that the above problems can be solved by setting the protruding height of the crosslinked polymer particles on the contact surface in contact with the convex to 0.0 times or more and 0.5 times or less the major axis of the crosslinked polymer particles. It led to the invention.

That is, the present invention
(I) An optical film composed of a thermoplastic resin composition containing crosslinked polymer particles and having a knurled portion in a part in the width direction.
An optical film in which the protruding height of the crosslinked polymer particles is 0.0 times or more and 0.5 times or less the major axis of the crosslinked polymer particles on the contact surface in contact with the knurling convex of the knurled portion.
(Ii) The optical film according to (i), wherein the surface roughness of the contact surface is 1 nm or more and 50 nm.
(Iii) The optical film according to (i) or (ii), wherein the thermoplastic resin composition contains an acrylic resin.
(Iv) The protrusion height of the crosslinked polymer particles in the portion other than the knurled portion is 0.3 times or more and 0.8 times or less the major axis of the crosslinked polymer particles, according to any one of (i) to (iii). Optical film,
(V) The crosslinked polymer particles consist of an optical film according to any one of (i) to (iv) containing multilayer structure particles, and a raw film composed of a thermoplastic resin composition containing (vi) crosslinked polymer particles. A method of manufacturing optical films
The knurling temperature during knurling on the raw film is Tg + 10 ° C. or higher and Tg + 40 ° C. or lower (Tg is the glass transition temperature of the thermoplastic resin composition), the knurling treatment speed is 20 m / min or higher and 50 m / min or lower, and the knurling. Provided is a method in which the pressing pressure is 0.1 MPa or more and 0.5 MPa or less.

According to the present invention, there is provided an optical film in which the occurrence of unwinding due to meandering of the film is suppressed while imparting slipperiness to the film by using crosslinked polymer particles, and a method for producing the optical film. be able to.

It is a figure which shows typically about the sandwich molding.

≪Optical film≫
The optical film is an optical film composed of a thermoplastic resin composition containing crosslinked polymer particles and having a knurled portion in a part in the width direction.
Further, on the contact surface in contact with the knurling convex of the knurled portion (hereinafter, also simply referred to as a contact surface), the protruding height of the crosslinked polymer particles is 0.0 times or more and 0.5 times the major axis of the crosslinked polymer particles. It is as follows.

In the optical film, the knurling process is applied to one side. The film is usually wound into a roll, and at that time, the knurling protrusion of the knurled portion comes into contact with the surface of the film that has not been knurled.
That is, the "contact surface in contact with the knurling convex of the knurled portion" is the surface of the film that has not been knurled.
The contact surface means only a portion of the film surface that has not been knurled and comes into contact with the knurling convex.

In the optical film, the protruding height of the crosslinked polymer particles on the contact surface in contact with the knurling convex of the knurled portion is 0.0 times or more and 0.5 times or less the major axis of the crosslinked polymer particles. The slip between the knurled portion and the contact surface is suppressed, which suppresses the meandering of the film.
The lower limit of 0.0 times also includes a state in which the crosslinked polymer particles are buried in the film and the surface of the contact surface is recessed.
The protruding height of the crosslinked polymer particles may be 0.1 times or more the major axis of the crosslinked polymer particles, or 0.2 times or more. Further, the protruding height of the crosslinked polymer particles may be 0.4 times or less of the major axis of the crosslinked polymer particles, or may be 0.3 times or less.
For the protruding height of the crosslinked polymer particles, data on the surface shape of the film was obtained using a scanning probe microscope, and the height of the smooth portion where the crosslinked polymer particles did not protrude and the height of the protruding crosslinked polymer particles top. Measured as the difference from the average height.

The protrusion height of the crosslinked polymer particles is 0.0 times or more and 0.5 times or less the major axis of the crosslinked polymer particles, which means that the crosslinked polymer protrudes only slightly on the surface of the contact surface.
In this case, since the contact state between the knurled portion and the contact surface is closer to the surface contact than the point contact, the knurled portion and the contact surface are less likely to slip. As a result, meandering is suppressed.

The major axis of the crosslinked polymer particles is the longest length of the distance connecting arbitrary two points on the outer periphery of the crosslinked polymer particles, and is measured by the following method. By observing the crosslinked polymer particles under a microscope and measuring the major axis of 10 or more crosslinked polymer particles having the longest length of 50 nm or more among the distances connecting arbitrary two points on the outer periphery of the crosslinked polymer particles. The value of the major axis of the crosslinked polymer particles can be obtained as the number average particle diameter.
When measuring the major axis of the crosslinked polymer particles in the film, the major axis which is the number average diameter may be determined by observing the film surface or the film cross section with a microscope and following the above method.

The major axis of the crosslinked polymer particles is not particularly limited as long as the object of the present invention is not impaired. The major axis of the crosslinked polymer particles is preferably 50 to 450 nm, more preferably 50 to 350 nm, and even more preferably 60 to 300 nm. If the major axis of the crosslinked polymer particles is too short, it may be difficult to obtain a film having sufficient crack resistance. If the major axis of the crosslinked polymer particles is too long, it may be difficult to obtain a film having excellent transparency.

The surface roughness of the contact surface (arithmetic mean roughness Ra) is not particularly limited as long as the protruding state of the crosslinked polymer particles on the contact surface satisfies a predetermined requirement. The surface roughness of the contact surface is preferably 1 nm or more and 50 nm or less, and more preferably 10 nm or more and 50 nm or less.

The protruding height of the crosslinked polymer particles at the portion (non-contact surface) that does not contact the knurling convex on the film surface including the contact surface is 0.3 times or more and 0.8 times or less the major axis of the crosslinked polymer particles. Is preferable.
The protruding height of the crosslinked polymer particles at a portion that does not contact the knurling convex may be 0.4 times or more, or 0.5 times or more, the major axis of the crosslinked polymer particles. Further, the protruding height of the crosslinked polymer particles may be 0.7 times or less of the major axis of the crosslinked polymer particles, or may be 0.6 times or less.
The protruding height of the crosslinked polymer particles on the non-contact surface and the height of the crosslinked polymer particles on the contact surface may be high, but it is preferable that the protruding height of the crosslinked polymer particles on the non-contact surface is high. ..
When the crosslinked polymer particles protrude in the above range at a portion that does not come into contact with the knurling convex, antiblocking property is imparted to the film surface, and the generation of defects due to blocking is satisfactorily suppressed.

The material and major axis of the crosslinked polymer particles contained in the contact surface and the crosslinked polymer particles contained in the non-contact surface may be the same or different.
When the crosslinked polymer particles contained in the contact surface and the crosslinked polymer particles contained in the non-contact surface are different in material and major axis, for example, a portion where the contact surface is formed and a portion where the non-contact surface is formed. After forming a film by co-extruding a thermoplastic resin containing different crosslinked polymer particles, a nerling process may be applied to a portion where a contact surface is formed.

The knurling process may be performed on any region in the width direction of the film. The area to be knurled may be one place or two or more places. When there are two or more places where knurling is applied, the knurled part and the contact surface are less likely to slip, so that the area sandwiched between the multiple areas where knurling is applied has a significant deviation during film transportation. It is suppressed.
From the viewpoint of high effect of suppressing meandering, it is preferable that knurling is applied to both ends in the film width direction.
Applying knurling to both ends in the film width direction is also preferable in that a wide film can be obtained when the knurled portion is cut by slitting or the like.

The total width of the portion to be knurled is not particularly limited as long as the desired effect can be obtained, but the width in the width direction of the film is preferably 10 mm or more and 100 mm or less. The total width of the portion to be knurled may be 20 mm or more, or 30 mm or more. Further, the total width of the portions to be knurled may be 90 mm or less, or 80 mm or less.

When the knurling process is applied to both ends in the width direction of the film, it is preferable that the knurling is performed with a width of 30 mm or less within a range of 50 mm or less from each end. The width of the knurling process applied to both ends of the film is not particularly limited as long as the desired effect can be obtained, but is preferably 5 mm or more, and more preferably 10 mm or more.
When the knurling process is applied to both ends in the width direction of the film, the width at which the knurling process is performed at both ends is preferably the same width.

The pattern shape of the unevenness formed by knurling is not particularly limited. Examples of the pattern shape, but not limited to these, include flatfish, diagonal, and twill.
The pitch in the knurling pattern (the shortest distance between the tops of adjacent knurling protrusions) is not particularly limited.
The height of the knurling convex is appropriately selected according to the film thickness, preferably 1 to 10 μm, more preferably 1.5 to 8 μm, and particularly preferably 2.0 to 6.0 μm.

The thickness of the optical film is not particularly limited.
With the optical film having the configuration described above, for example, even in an extremely thin film having a thickness of 30 μm or more and 80 μm or less, slipperiness can be suppressed in the knurled part and slipped in the non-nerled part. Since the property can be imparted, it is possible to suppress the occurrence of unwinding due to meandering of the film while imparting slipperiness to the film by using the crosslinked polymer particles.
With conventionally known optical films, it is difficult to suppress the occurrence of unwinding due to meandering of the film while imparting slipperiness to the film by using crosslinked polymer particles during the production of a thin film. It is remarkable.

As described above, the above optical film includes a knurling processed portion. The optical film is usually used in a state where the knurled portion is cut by a method such as slit processing.
However, depending on the mode of use of the optical film, the presence of the knurled portion may be allowed. In this case, the optical film can be used without cutting off the knurled portion.

Hereinafter, essential or arbitrary components in the thermoplastic resin composition which is the material of the optical film will be described.

(Thermoplastic resin)
The thermoplastic resin is a material that constitutes a matrix portion in a film. The thermoplastic resin used in the production of the film is not particularly limited as long as it is a thermoplastic resin that can be used as an optical film and can be molded by melt extrusion.
For example, polycarbonate resin, aromatic vinyl resin and its hydrogen additive, polyolefin resin, acrylic resin, polyester resin, polyarylate resin, polyimide resin, polyether sulfone resin, polyamide resin, cellulose resin, Examples thereof include thermoplastic resin compositions such as polyphenylene oxide resin. Of these, acrylic resins are particularly preferable from the viewpoint of transparency.

The acrylic resin is not particularly limited, but a methacrylic resin containing methyl methacrylate as a monomer component can be used, and a resin containing 30 to 100% by weight of a constituent unit derived from methyl methacrylate is preferable. Among the acrylic resins, heat-resistant acrylic resins are preferable.

As a heat-resistant acrylic resin, for example,
1) Acrylic resin in which an N-substituted maleimide compound is copolymerized as a copolymerization component.
2) Acrylic anhydrous glutarate resin,
3) Acrylic resin having a lactone ring structure,
4) Glutarimide acrylic resin,
5) Acrylic resin containing hydroxyl groups and / or carboxyl groups,
6) Aromatic vinyl-containing acrylic polymer obtained by polymerizing an aromatic vinyl monomer and another monomer copolymerizable therewith (for example, a styrene monomer and another single amount copolymerizable therewith). Styrene-containing acrylic polymer obtained by polymerizing the body)
7) A hydrogenated aromatic vinyl-containing acrylic polymer obtained by partially or completely hydrogenating the aromatic ring of the resin of 6) above (for example, a styrene monomer and another single amount copolymerizable therewith). Partially hydrogenated styrene-containing acrylic polymer obtained by partially hydrogenating the aromatic ring of the styrene-containing acrylic polymer obtained by polymerizing the body),
8) Acrylic polymer containing a cyclic acid anhydride repeating unit and the like can be mentioned.
A glutarimide acrylic resin can be more preferably used from the viewpoint of heat resistance and optical properties.

（式中、Ｒ^１およびＲ^２は、それぞれ独立して、水素原子または炭素数１〜８のアルキル基であり、Ｒ^３は、炭素数１〜１８のアルキル基、炭素数３〜１２のシクロアルキル基、または炭素数５〜１５の芳香環を含む置換基である。）
で表される単位（以下、「グルタルイミド単位」ともいう）と、
下記一般式（２）：

（式中、Ｒ^４およびＲ^５は、それぞれ独立して、水素原子または炭素数１〜８のアルキル基であり、Ｒ^６は、炭素数１〜１８のアルキル基、炭素数３〜１２のシクロアルキル基、または炭素数５〜１５の芳香環を含む置換基である。）
で表される単位（以下、「（メタ）アクリル酸エステル単位」ともいう）とを含むグルタルイミドアクリル系樹脂を好適に用いることができる。 The glutarimide acrylic resin will be described in detail below. Specifically, as the glutarimide acrylic resin, for example, the following general formula (1):

(In the formula, R ¹ and R ² are independently hydrogen atoms or alkyl groups having 1 to 8 carbon atoms, and R ³ is an alkyl group having 1 to 18 carbon atoms and cyclo having 3 to 12 carbon atoms. It is an alkyl group or a substituent containing an aromatic ring having 5 to 15 carbon atoms.)
Units represented by (hereinafter, also referred to as "glutarimide units") and
The following general formula (2):

(In the formula, R ⁴ and R ⁵ are independently hydrogen atoms or alkyl groups having 1 to 8 carbon atoms, and R ⁶ is an alkyl group having 1 to 18 carbon atoms and cyclo having 3 to 12 carbon atoms. It is an alkyl group or a substituent containing an aromatic ring having 5 to 15 carbon atoms.)
A glutarimide acrylic resin containing a unit represented by (hereinafter, also referred to as "(meth) acrylic acid ester unit") can be preferably used.

（式中、Ｒ^７は、水素原子または炭素数１〜８のアルキル基であり、Ｒ^８は、炭素数６〜１０のアリール基である。）
で表される単位（以下、「芳香族ビニル単位」ともいう）をさらに含んでいてもよい。 Further, the glutarimide acrylic resin may be prepared from the following general formula (3):

(In the formula, R ⁷ is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R ⁸ is an aryl group having 6 to 10 carbon atoms.)
It may further contain a unit represented by (hereinafter, also referred to as "aromatic vinyl unit").

In the above general formula (1), R ¹ and R ² are independently hydrogen atoms or methyl groups, respectively. R ³ is preferably a hydrogen atom, a methyl group, a butyl group, or a cyclohexyl group, R ¹ is a methyl group, R ² is a hydrogen atom, and R ³ is more preferably a methyl group.

The glutarimide acrylic resin may contain only a single type as a glutarimide unit, or may contain a plurality of types having different R ¹ , R ² , and R ³ in the above general formula (1). You may.
The glutarimide unit is an adjacent two alkoxycarbonyl groups contained in the continuous (meth) acrylic acid ester unit when the (meth) acrylic acid ester unit represented by the above general formula (2) is continuous. It can be formed by imidizing (carboxylic acid ester group).

Also, an acid anhydride such as maleic anhydride, or a half ester of such an acid anhydride and a linear or branched alcohol having 1 to 20 carbon atoms; acrylic acid, citraconic acid, maleic acid, maleic anhydride, The glutarimide unit can also be formed by imidizing α, β-ethylene unsaturated carboxylic acids such as itaconic acid, maleic anhydride, crotonic acid, fumaric acid, and citraconic acid.

In the above general formula (2), R ⁴ and R ⁵ are preferably hydrogen or methyl groups, respectively, R ⁶ is preferably hydrogen or methyl group, R ⁴ is hydrogen, and R ⁵ is. It is a methyl group, and it is more preferable that R ⁶ is a methyl group.
The glutarimide acrylic resin, (meth) acrylic acid ester unit, may include only a single type, R ⁴ in the general formula ^(2), R ^5, and R ⁶ is different The type may be included.
The glutarimide acrylic resin preferably contains styrene, α-methylstyrene, or the like as the aromatic vinyl constituent unit represented by the general formula (3), and more preferably contains styrene.
Further, the glutarimide acrylic resin may contain only a single type as the aromatic vinyl constituent unit, or may contain a plurality of types having different R ⁷ and R ⁸ .

In the above general formula (2), R ⁴ and R ⁵ are preferably hydrogen atoms or methyl groups, respectively, R ⁶ is preferably a hydrogen atom or a methyl group, and R ⁴ is a hydrogen atom. More preferably, R ⁵ is a methyl group and R ⁶ is a methyl group.
The glutarimide acrylic resin, (meth) acrylic acid ester unit, may include only a single type, R ⁴ in the general formula ^(2), R ^5, and R ⁶ is different The type may be included.
The glutarimide acrylic resin preferably contains styrene, α-methylstyrene, or the like as the aromatic vinyl constituent unit represented by the general formula (3), and more preferably contains styrene.
Further, the glutarimide acrylic resin may contain only a single type as the aromatic vinyl constituent unit, or may contain a plurality of types having different R ⁷ and R ⁸ .

In the glutarimide acrylic resin, the content of the glutarimide unit represented by the general formula (1) is not particularly limited, for example, it is preferable to change depending on the structure or the like of R ^3.

In general, the content of the glutarimide unit is preferably 1% by weight or more, more preferably 1% by weight to 95% by weight, still more preferably 2% by weight to 90% by weight of the glutarimide acrylic resin. It is particularly preferably from% to 80% by weight.
If the content of the glutarimide unit is within the above range, the heat resistance and transparency of the obtained glutarimide acrylic resin may be lowered, or the moldability and the mechanical strength when processed into a film may be lowered. It's hard to do.

On the other hand, if the content of the glutarimide unit is less than the above range, the heat resistance of the obtained glutarimide acrylic resin tends to be insufficient or the transparency tends to be impaired. On the other hand, if it is more than the above range, the heat resistance and the melt viscosity are unnecessarily increased, the molding processability is deteriorated, the mechanical strength at the time of film processing becomes extremely brittle, and the transparency is impaired. Tend.

In the glutarimide acrylic resin, the content of the aromatic vinyl unit represented by the general formula (3) is not particularly limited, and can be appropriately set according to the required physical properties. Depending on the intended use, the content of the aromatic vinyl unit represented by the general formula (3) may be 0% by weight.
When the aromatic vinyl unit represented by the general formula (3) is contained, the content thereof is preferably 10% by weight or more based on the total repeating unit of the glutarimide acrylic resin, and is preferably 10% by weight to 40% by weight. It is more preferably 50% by weight, further preferably 15% to 30% by weight, and particularly preferably 15% to 25% by weight. When the content of the aromatic vinyl unit is within the above range, the heat resistance of the obtained glutarimide acrylic resin is unlikely to be insufficient, and the mechanical strength during film processing is unlikely to decrease.
On the other hand, if the content of the aromatic vinyl unit is larger than the above range, the heat resistance of the obtained glutarimide acrylic resin tends to be insufficient.

If necessary, the glutarimide acrylic resin may be further copolymerized with other units other than the glutarimide unit, the (meth) acrylic acid ester unit, and the aromatic vinyl unit.
Other units include, for example, copolymerization of nitrile-based monomers such as acrylonitrile and methacrylonitrile, and maleimide-based monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide. The constituent units can be mentioned.
These other units may be directly copolymerized or graft-copolymerized in the glutarimide acrylic resin.

The weight average molecular weight of the glutarimide acrylic resin is not particularly limited, but is preferably ^{1 × 10 4 ~5 × 10 5} . If it is within the above range, it is unlikely that the moldability is lowered and the mechanical strength at the time of film processing is insufficient. On the other hand, if the weight average molecular weight is smaller than the above range, the mechanical strength of the film tends to be insufficient. On the other hand, if it is larger than the above range, the viscosity at the time of melt extrusion is high, the molding processability is lowered, and the productivity of the molded product tends to be lowered.

The glass transition temperature of the glutarimide acrylic resin is not particularly limited, but is preferably 110 ° C. or higher, more preferably 120 ° C. or higher. When the glass transition temperature is within the above range, the applicable range of the obtained thermoplastic resin composition can be expanded.

The method for producing the glutarimide acrylic resin is not particularly limited, and examples thereof include the methods described in JP-A-2008-273140.

(Crosslinked polymer particles)
The crosslinked polymer particles are not particularly limited as long as they are particles containing polymers having various conventionally known crosslinked structures.
The crosslinked polymer particles are preferably multilayer structure type (core shell type) particles having a rubber portion. The presence of the shell layer improves compatibility with the thermoplastic resin to be mixed and allows the particles to be uniformly dispersed. When particles without a shell layer are mixed with a thermoplastic resin, the particles are difficult to disperse uniformly, and the transparency of the film may decrease.
Hereinafter, preferred examples of the crosslinked polymer particles will be described.

-Multilayer structure particles Preferred examples of the crosslinked polymer particles include multilayer structure particles having a rubber portion having a degree of crosslink of 2.3% by weight or more and 4.0% by weight or less and a particle diameter of 180 nm or more and 400 nm or less. Be done.
Such multilayer structure particles enhance the slipperiness of the film, impart antiblocking property to the film, have excellent dispersibility in the film, and do not easily reduce the transparency of the film.

The multilayer structure particles having a rubber portion having a degree of cross-linking of 2.3% by weight or more and 4.0% by weight or less have a certain degree of hardness. As a result, when the films containing the multilayer structure particles come into contact with each other or between the films and the rolls, the multilayer structure particles are less likely to be deformed, and the film is particularly liable to be provided with slipperiness.
The degree of cross-linking is the ratio (% by weight) of the weight of the polyfunctional monomer having two or more functionalities to the total weight of the monomer of the monomer used for the production of the rubber part. Is.

When the degree of cross-linking of the rubber portion is less than 2.3% by weight, the rubber portion is flexible and therefore easily deforms when the multilayer structure particles protruding from the film surface come into contact with the roll or the film. Therefore, it may be difficult to impart slipperiness to the film.
When the degree of cross-linking of the rubber portion exceeds 4.0% by weight, cracks and chips are likely to occur in the multilayer structure particles, and the desired slipperiness cannot be imparted to the central portion of the film, or fine powder is generated during film production. In some cases.

When multilayer structure particles having a rubber portion having a particle diameter of 180 nm or more and 400 nm or less are used, it is easy to impart slipperiness to the film without impairing the transparency of the film. When the particle size of the rubber portion is less than 180 nm, it is difficult to impart a desired degree of slipperiness to the film. Further, when the particle size of the rubber portion exceeds 400 nm, it may be difficult to obtain a film having a desired degree of transparency. Here, the particle size of the rubber portion is determined by using a U-5100 type ratio beam spectrophotometer manufactured by Hitachi High-Technologies Corporation and using light scattering with a wavelength of 546 nm.

The multilayer structure particles are composed of core particles having a rubber portion having the above-mentioned predetermined requirements and a shell layer. The shell layer may be a single layer or a multi-layer.

The shell layer may be chemically bonded to the rubber portion by a covalent bond or the like, or may cover the rubber portion without being chemically bonded to the rubber portion. When the shell layer has a multi-layer structure of two or more layers, the layers constituting the shell layer may or may not be chemically bonded to each other by a covalent bond or the like. ..
A preferred example of a method of chemically bonding the shell layer to the surface of the rubber portion or the surface of another shell layer is a method of forming the shell layer by graft polymerization.

Examples of the material of the rubber portion include a butadiene-based crosslinked polymer, a (meth) acrylic-based crosslinked polymer, and an organosiloxane-based crosslinked polymer. Among them, in terms of weather resistance (light resistance) and transparency of the film, the (meth) acrylic crosslinked polymer (in the present specification, the rubber portion made of the (meth) acrylic copolymer is referred to as the acrylic rubber particles. Also referred to as) is particularly preferable.

Examples of the acrylic rubber particles include ABS resin rubber particles, ASA resin rubber particles, and acrylic acid ester rubber particles.
As the multilayer structure particles, multilayer structure particles obtained by forming a shell layer by performing graft polymerization on the surface of these acrylic rubber particles using a desired monomer are preferable.
From the viewpoint of the transparency of the obtained film, the acrylic-based graft copolymer particles obtained by graft-polymerizing the surfaces of the acrylic acid ester-based rubber-like polymer particles shown below are preferable as the multilayer structure particles. ..
Acrylic-based graft copolymer particles can be obtained by polymerizing a monomer mixture containing a methacrylic acid ester as a main component in the presence of particles of an acrylic acid ester-based rubber-like polymer.

The acrylic acid ester-based rubber-like polymer, which is the material of the rubber portion, is a rubber-like polymer containing acrylic acid ester as a main component. Specifically, a monomer mixture (100% by weight) consisting of 50 to 100% by weight of acrylic acid ester and 50 to 0% by weight of other copolymerizable vinyl-based monomer, and two or more per molecule. It is preferably obtained by polymerizing a polyfunctional monomer having a non-conjugated reactive double bond.
The polyfunctional monomer is used in a desired amount so that the degree of cross-linking of the rubber portion is in the range of 2.3% by weight or more and 4.0% by weight or less.
All the monomers may be mixed and used, or the monomer composition may be changed and used in two or more stages.

As the acrylic acid ester, it is preferable to use an alkyl group having 1 to 12 carbon atoms from the viewpoint of polymerizable property and cost. For example, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, benzyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, n- acrylate. Examples thereof include octyl, phenyl acrylate, and 2-phenoxyethyl acrylate.
Two or more of these acrylic ester may be used in combination.
The amount of acrylic acid ester is preferably 50% by weight or more and 100% by weight or less, more preferably 60% by weight or more and 99% by weight or less, still more preferably 70% by weight or more and 99% by weight or less, and 80% by weight or less, based on 100% by weight of the monomer mixture. Most preferably, it is by weight% or more and 99% by weight or less.
If it is less than 50% by weight, the impact resistance is lowered, the elongation at the time of tensile break is lowered, and cracks are likely to occur at the time of cutting the film.

As the other vinyl-based monomer copolymerizable with the acrylic acid ester, methacrylic acid esters are particularly preferable from the viewpoint of weather resistance and transparency. Examples of methacrylic acid esters include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, 2-methacrylic acid. Examples thereof include phenoxyethyl, 2-ethylhexyl methacrylate, phenyl methacrylate, n-octyl methacrylate and the like.

In addition, aromatic vinyls and derivatives thereof, and vinyl cyanide are also preferable. Examples of these vinyl-based monomers include styrene, methylstyrene, acrylonitrile, and methacrylonitrile. Other examples include unsubstituted and / or substituted maleic anhydrides, (meth) acrylamides, vinyl esters, vinylidene halides, (meth) acrylic acids and salts thereof, and (hydroxyalkyl) acrylic acid esters.

Examples of the polyfunctional monomer copolymerized with the monofunctional monomer containing acrylic acid ester as a main component include allyl methacrylate, allyl acrylate, triallyl cyanurate, triallyl isocyanurate, and diallyl phthalate. Uses diallyl malate, divinyl adipate, divinylbenzene, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, trimethylroll propantrimethacrylate, pentaerythritol tetramethacrylate, dipropylene glycol dimethacrylate, and acrylates thereof. can do. Two or more of these polyfunctional monomers may be used.

The multilayer structure polymer may have another polymer layer inside (center side) of the rubber portion. From the viewpoint of anti-blocking property, a monomer mixture consisting of 40 to 100% by weight of an alkyl methacrylate ester and 60 to 0% by weight of another monomer having a copolymerizable double bond thereof, and the above-mentioned It is preferable to have a methacrylic crosslinked polymer layer obtained by polymerizing 0.01 to 10 parts by weight of a polyfunctional monomer with respect to 100 parts by weight of the monomer mixture. Examples of the monomer having a copolymerizable double bond include the above-mentioned other copolymerizable vinyl-based monomers and acrylic acid esters.
The acrylic graft copolymer comprising the rubber portion and the shell layer formed by graft polymerization on the surface of the rubber portion is 5 to 90 parts by weight (more preferably 5) of particles of the acrylic acid ester rubber-like polymer. It is preferably obtained by polymerizing 95 to 25 parts by weight of a monomer mixture containing a methacrylic acid ester as a main component in at least one step in the presence of (~ 75 parts by weight).

The methacrylic acid ester in the graft copolymer composition (monomixture) is preferably 50% by weight or more. If it is less than 50% by weight, the hardness and rigidity of the obtained film tend to decrease.
As the monomer used for graft copolymerization, the above-mentioned methacrylic acid ester, acrylic acid ester, and vinyl-based monomer copolymerizable with these can be similarly used, and methacrylic acid ester and acrylic acid ester are preferably used. Will be done. Methyl methacrylate is preferable from the viewpoint of compatibility with an acrylic resin, and methyl acrylate, ethyl acrylate, and n-butyl acrylate are preferable from the viewpoint of suppressing zipper depolymerization.

From the viewpoint of optical isotropic property, it is referred to as a (meth) acrylic monomer having an alicyclic structure, a heterocyclic structure or an aromatic group (referred to as "ring structure-containing (meth) acrylic monomer". ) Is also preferable as a monomer for graft copolymerization. Specific examples thereof include benzyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and 2-phenoxyethyl (meth) acrylate.

The amount used is 100% by weight based on the total amount of the monomer mixture for graft copolymerization (the total amount of the ring structure-containing (meth) acrylic monomer and other monofunctional monomers copolymerizable therewith). 1 to 100% by weight is preferable, 5 to 70% by weight is more preferable, and 5 to 50% by weight is most preferable.

The other monofunctional monomer copolymerizable with the ring structure-containing (meth) acrylic monomer is the above-mentioned methacrylic acid ester, acrylic acid ester, or other copolymerizable vinyl monofunctional monomer. The weights can be used as well, but preferably contain a methacrylic acid ester and an acrylic acid ester.

The methacrylic acid ester is preferably contained in an amount of 0 to 98% by weight based on 100% by weight of the above-mentioned ring structure-containing vinyl-based monomer and other monofunctional monomer copolymerizable therewith. It is more preferably contained in an amount of ~ 98% by weight, further preferably 1 to 94% by weight, and particularly preferably 30 to 90% by weight.
Further, the acrylic acid ester is preferably contained in an amount of 0 to 98% by weight based on 100% by weight of the total amount of the above-mentioned ring structure-containing vinyl-based monomer and other monofunctional monomers copolymerizable therewith. .1 to 98% by weight is more preferable, 1 to 50% by weight is further preferable, and 5 to 50% by weight is particularly preferable.

The graft ratio of the acrylic ester-based rubber-like polymer to the particles is preferably 10 to 250%, more preferably 40 to 230%, and most preferably 60 to 220%.
If the graft ratio is less than 10%, the acrylic graft copolymer particles tend to aggregate in the film, which may reduce the transparency or cause foreign matter. In addition, the elongation at the time of tensile breakage decreases, and cracks tend to occur easily at the time of film cutting. If it exceeds 250%, for example, the melt viscosity during film molding tends to increase, and the formability of the film tends to decrease.

The graft ratio is a weight ratio of the graft component in the acrylic graft copolymer particles, and is measured by, for example, the following method.
2 g of acrylic graft copolymer particles are dissolved in 50 ml of methyl ethyl ketone and centrifuged at a rotation speed of 30,000 rpm and a temperature of 12 ° C. for 1 hour using a centrifuge (manufactured by Hitachi Koki Co., Ltd., CP60E) to remove insoluble matter. Separate into the dissolved components (centrifugal separation work is set 3 times in total). From the weight of the obtained insoluble matter and the weight of the acrylic acid ester-based rubber-like polymer contained in the acrylic-based graft copolymer particles, the graft ratio is calculated by the following formula.
Graft ratio (%) = [{(weight of methyl ethyl ketone insoluble matter)-(weight of acrylic ester-based rubber polymer)} / (weight of acrylic ester rubber polymer)] × 100

Acrylic graft copolymer particles can be produced by a general emulsification polymerization method. Specifically, a method of continuously polymerizing an acrylic acid ester monomer using an emulsifier in the presence of a water-soluble polymerization initiator can be exemplified.
In the emulsion polymerization method, it is preferable to carry out continuous polymerization in a single reaction tank, and it is not preferable to use two or more reaction tanks because the mechanical stability of the latex is lowered.
The polymerization temperature is preferably 30 ° C. or higher and 100 ° C. or lower, more preferably 50 ° C. or higher and 80 ° C. or lower. If the temperature is lower than 30 ° C., the productivity tends to decrease, and if the temperature exceeds 100 ° C., the target molecular weight tends to be excessively large, and the quality tends to decrease.
Raw materials such as monomers, initiators, emulsifiers and deionized water that are continuously added to the polymerization reaction tank are accurately added under the control of the metering pump, but the amount of heat removed from the polymerization heat generated in the reaction tank. There is no problem even if it is cooled in advance as necessary to ensure the above.
A polymerization inhibitor, a coagulant, a flame retardant, an antioxidant, and a pH adjuster may be added to the latex discharged from the reaction vessel, if necessary, to recover unreacted monomers and post-polymerize. You may go. After that, a copolymer can be obtained through known methods such as solidification, heat treatment, dehydration, washing with water, and drying.

In the emulsion polymerization, a usual polymerization initiator can be used. For example, inorganic peroxides such as potassium persulfate and sodium persulfate, organic peroxides such as cumenehydroperoxide and benzoyl peroxide, and oil-soluble initiators such as azobisisobutyronitrile are also used. These may be used alone or in combination of two or more. These initiators are used as ordinary redox-type polymerization initiators in combination with reducing agents such as sodium sulfite, sodium thiosulfate, sodium formaldehyde, sulfoxylate, ascorbic acid, ferrous sulfate, and disodium ethylenediaminetetraacetic acid complex. You may.

A chain transfer agent may be used in combination with the polymerization initiator. Examples of the chain transfer agent include alkyl mercaptans having 2 to 20 carbon atoms, mercapto acids, thiophenols, carbon tetrachloride and the like, and these may be used alone or in combination of two or more.

The emulsifier used in the emulsion polymerization method is not particularly limited, and an ordinary emulsifier for emulsion polymerization can be used. For example, sulfate ester-based surfactants such as sodium alkylsulfate, sulfonate-based surfactants such as sodium alkylbenzene sulphonate, sodium alkylsulfonate, and sodium dioctyl sulfosuccinate, sodium alkylphosphates, polyoxyethylene alkyl ethers. Examples thereof include anionic surfactants such as phosphate-based surfactants such as sodium phosphate ester. Further, the sodium salt may be another alkali metal salt such as potassium salt or an ammonium salt. These emulsifiers may be used alone or in combination of two or more. Further, a nonionic surfactant represented by an alkyl-substituted product or an aryl-substituted product of the polyoxyalkylenes or the terminal hydroxyl group thereof may be used or partially used in combination. Among them, a sulfonate-based surfactant or a phosphate-based surfactant is preferable from the viewpoint of polymerization reaction stability and particle-based controllability, and among them, dioctyl sulfosuccinate or polyoxyethylene alkyl ether phosphoric acid. Ester salts can be used more preferably.

The amount of the emulsifier used is preferably 0.05 parts by weight or more and 10 parts by weight, and more preferably 0.1 parts by weight or more and 1.0 part by weight or less with respect to 100 parts by weight of the entire monomer component. If the amount is less than 0.05 parts by weight, the particle size of the copolymer tends to be too large, and if the amount is more than 10 parts by weight, the particle size of the graft copolymer tends to be too small and the particle size distribution tends to be deteriorated. is there.

The multilayer structure particles described above and the thermoplastic resin are mixed to obtain a thermoplastic resin composition.
The multilayer structure particles and the thermoplastic resin may be uniformly pelletized according to a conventional method before the film is produced, or may be mixed by an extruder during the film production.
The amount of the multilayer structure particles used is not particularly limited as long as the object of the present invention is not impaired. The amount of the multilayer structure particles used is preferably 0.1 to 2.0 parts by weight, more preferably 0.2 to 1.5 parts by weight, when the total weight of the thermoplastic resin composition is 100 parts by weight.
When the amount of the multilayer structure particles used is less than 0.1 parts by weight, it is difficult to impart the desired degree of slipperiness to the obtained film, and blocking-induced defects are likely to occur when the film is wound.
Further, if the amount of the multilayer structure particles used is more than 2.0 parts by weight, excessive slipperiness is given to the film, which may cause a transfer trouble.

-Rubber Particles Another preferable example of the crosslinked polymer particles is a multilayer structure type rubber particles having a rubber portion having a degree of crosslink of less than 2.3% by weight and a particle diameter of 180 nm or more and 400 nm or less.
The glass transition temperature of the rubber portion is not particularly limited, but is preferably less than 20 ° C.
When the thermoplastic resin composition contains rubber particles, toughness is imparted to the film, and as a result, cracking of the film in the transport process and generation of fine powder due to slit failure at the slit portion are less likely to occur, resulting in productivity. Can be improved.

Suitable rubber particles having a multi-layer structure can be produced by the same material and the same method as the above-mentioned multi-layer structure particles, except that the degree of cross-linking of the rubber portion is different.

The amount of the rubber particles used is not particularly limited as long as the object of the present invention is not impaired. The amount of the rubber particles used is preferably 1 to 60 parts by weight, more preferably 1 to 30 parts by weight, still more preferably 1 to 25 parts by weight, when the total weight of the thermoplastic resin composition is 100 parts by weight.

The rubber particles are less likely to impart slipperiness to the film when compared with the multilayer structure particles described above. Therefore, the rubber particles are preferably blended with the above-mentioned multilayer structure particles in the thermoplastic resin composition.

(Other ingredients)
The thermoplastic resin composition may contain one or more kinds of antioxidants, ultraviolet absorbers, ultraviolet stabilizers and the like for improving stability against heat and light, in addition to the multilayer structure particles.

≪Manufacturing method of optical film≫
The method for producing an optical film is not particularly limited as long as it can produce an optical film having the above-mentioned predetermined configuration.
As a method for producing an optical film, a method is performed in which a thermoplastic resin composition on a sheet extruded from an extruder via a T-die is sandwiched and molded, and then knurling is performed at a desired timing at a desired position. Can be mentioned.
FIG. 1 is a diagram schematically showing sandwich molding in a method for manufacturing an optical film. In FIG. 1, the extruder 10 is simplified and only the vicinity of the T die 11 is shown.

First, a predetermined thermoplastic resin composition as a film raw material is put into the extruder 10 and heated to a temperature equal to or higher than the glass transition temperature in the extruder 10 to be in a molten state.
The melted thermoplastic resin composition is transferred to the T-die 11 attached to the outlet side of the extruder 10, and is discharged from the die outlet 12 at the tip of the die in the molten state. At the time of discharge, the thermoplastic resin composition 13 in the molten state takes a sheet shape due to the shape of the die outlet 12.

The surface of the sheet-shaped thermoplastic resin composition 13 in the molten state is smoothed by being sandwiched between a pair of smoothing rolls. One of the smoothing rolls is an elastic roll 14 and the other is a cast roll 15. The elastic roll 14 refers to a roll in which the surface of a roll made of an elastic body such as rubber is covered with a metal film, and the surface of the roll is flattened by the metal film on the surface and functions as a smoothing roll.
The cast roll 15 is a hard roll made of metal.

By sandwiching the sheet-shaped thermoplastic resin composition 13 discharged from the die outlet 12 between the elastic roll 14 and the cast roll 15, the temperature is cooled to a temperature equal to or lower than the glass transition temperature thereof, and the smoothness of the sheet surface is improved. ..
The sandwich molding step is a step for smoothing the surface of the film, and is different from the step for stretching the film.
Note that FIG. 1 is a schematic view of the sheet-shaped thermoplastic resin composition 13 as viewed from a plane perpendicular to the width direction of the die outlet 12.

As described above, by continuously performing the ejection from the extruder 10 (die outlet 12) and the sandwich molding step between the elastic roll 14 and the cast roll 15, the optical film stretched in the longitudinal direction is continuously formed. Manufactured.

If necessary, the method for producing an optical film may include a step of inspecting foreign matter in the film and a stretching step of using the film after sandwich molding as a raw film.

The film thus obtained is subjected to knurling at any position in the width direction of the film before it is finally wound up as a product.
The nerling process is performed before winding the film in the film forming process of converting the thermoplastic resin into a film, before winding the film in the additional process of applying additional processing to the film such as stretching and coating, or in the film forming process. This may be carried out after the film is wound and before the film is wound in a separate rewinding step.
Of these, it is most preferable to perform a knurling process after the film is formed and before it is first wound into a roll. Once wound, blocking-induced defects may occur before the knurling process is performed, which is not preferable.

As a method for performing the knurling process, various methods such as a knurling method and a laser method can be adopted, and the knurling method is preferable.
The knurling method is preferable in that the non-convex portion can also be thermally deformed when controlling the protruding height of the crosslinked polymer particles other than the knurled portion as described later.

When the knurling process is applied, pressure is applied to both sides of the film. Therefore, depending on the height of the pressure applied to both sides of the film, the crosslinked polymer particles are somewhat buried in the above-mentioned contact surface, and the protruding height of the crosslinked polymer is adjusted within a predetermined range.

When knurling is performed by the knurling method, the knurling temperature at the time of knurling is preferably Tg + 10 ° C. to Tg + 40 ° C., the knurling processing speed is preferably 20 m / min to 50 m / min, and the knurling pressure is 0.1 MPa or higher. It is preferably 0.5 MPa or less.
When the knurling temperature is from Tg + 10 ° C. to Tg + 40 ° C., the thermoplastic resin composition is appropriately deformed. Therefore, the protrusion height of the crosslinked polymer particles on the contact surface in contact with the knurling convex is adjusted within a desired range. Cheap.
When the knurling processing speed is 20 m / min to 50 m / min, it is easy to apply sufficient force to the film surface, it is easy to form a knurling convex at a desired height, and cross-linking is performed on the contact surface in contact with the knurling convex. It is easy to adjust the protrusion height of the polymer particles within a desired range.
When the knurling pressing pressure is 0.1 MPa or more and 0.5 MPa or less, it is easy to form a knurling convex with a desired height, and the thermoplastic resin composition can be appropriately deformed and comes into contact with the knurling convex. It is easy to adjust the protruding height of the crosslinked polymer particles on the contact surface within a desired range.

The optical film having the above-mentioned predetermined configuration manufactured as described above is a member used in a display device such as a liquid crystal display device or an organic EL device, for example, a polarizing plate protective film, a retardation film, a brightness improving film, and the like. It can be used for liquid crystal substrates, light diffusion sheets, prism sheets and the like. Above all, it is suitable for a polarizing plate protective film and a retardation film.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to these Examples.

The methods for measuring each physical property measured in Examples and Comparative Examples are as follows.
(Average particle size of the rubber part of the multilayer structure particles)
Using the obtained polymer latex diluted to a solid content concentration of 0.02% as a sample, using a U-5100 type ratio beam spectrophotometer of Hitachi High-Technologies Corporation, light scattering with a wavelength of 546 nm was used. I asked for it.
(Glass-transition temperature)
Using the differential scanning calorimetry (DSC) SSC-5200 manufactured by Seiko Instruments, the sample was once heated to 200 ° C. at a rate of 25 ° C./min, held for 10 minutes, and then held at a rate of 25 ° C./min to 50 ° C. After preliminary adjustment to lower the temperature, the measurement was performed while the temperature was raised to 200 ° C at a heating rate of 10 ° C / min, the integrated value was obtained from the obtained DSC curve (DDSC), and the glass transition temperature was obtained from the maximum point. Asked.
(Rolling deviation)
The deviation of the end of the rolled-up film roll is measured with a caliper, and it is evaluated as no 1 mm or less (○), slightly larger than 1 mm and 3 mm or less (△), and larger than 3 mm (×). did.
(Defect caused by blocking)
When a high-brightness light is applied to the rolled-up film roll from the end, no color shading is observed (○), and slight color shading is observed (△), high-brightness light. The case where the shade of color is observed under a fluorescent lamp without using is regarded as (x).

<Manufacturing Example 1: Production of Acrylic Resin (A1)>
In Production Example 1, an acrylic resin (A1), which is a glutarimide acrylic resin, was produced using polymethyl methacrylate (A2) as a raw material resin and monomethylamine as an imidizing agent.
In this production, a tandem type reaction extruder in which two extrusion reactors were arranged in series was used.
Regarding the tandem type reaction extruder, both the first extruder and the second extruder have a diameter of 75 mm and an L / D (ratio of the length L of the extruder to the diameter D) of 74, which is a meshing type isodirectional twin-screw extruder. Was used to supply the raw material resin to the raw material supply port of the first extruder using a constant weight feeder (manufactured by Kubota Co., Ltd.).
The degree of decompression of each vent in the first extruder and the second extruder was −0.095 MPa. Further, a pressure control mechanism inside the component that connects the first extruder and the second extruder with a pipe having a diameter of 38 mm and a length of 2 m, and connects the resin discharge port of the first extruder and the raw material supply port of the second extruder. Used a constant flow pressure valve.
The resin (strand) discharged from the second extruder was cooled by a cooling conveyor and then cut with a pelletizer into pellets. Here, in order to adjust the pressure inside the component connecting the resin discharge port of the first extruder and the raw material supply port of the second extruder, or to determine the extrusion fluctuation, the discharge port of the first extruder, the first extruder, and the first extruder are used. A resin pressure gauge was provided at the center of the connecting parts between the two extruders and at the discharge port of the second extruder.
In the first extruder, polymethyl methacrylate resin (Mw: 105,000) was used as a raw material resin, and monomethylamine was used as an imidizing agent to produce an imide resin intermediate 1. At this time, the temperature of the maximum temperature part of the extruder was 280 ° C., the screw rotation speed was 55 rpm, the amount of the raw material resin supplied was 150 kg / hour, and the amount of monomethylamine added was 2.0 parts with respect to 100 parts of the raw material resin. The constant flow pressure valve was installed immediately before the raw material supply port of the second extruder, and the pressure at the monomethylamine press-fitting portion of the first extruder was adjusted to 8 MPa.
In the second extruder, the imidizing agent and by-products remaining in the rear vent and the vacuum vent were devolatile, and then dimethyl carbonate was added as an esterifying agent to produce an imide resin intermediate 2. At this time, the barrel temperature of the extruder was 260 ° C., the screw rotation speed was 55 rpm, and the amount of dimethyl carbonate added was 3.2 parts with respect to 100 parts of the raw material resin. Further, the esterifying agent was removed by venting, extruded from the strand die, cooled in a water tank, and then pelletized with a pelletizer to obtain an acrylic resin (A1).
The obtained acrylic resin (A1) is an acrylic resin obtained by copolymerizing a glutamylimide unit and a (meth) acrylic acid ester unit.

<Manufacturing Example 2: Production of rubber particles (B1)>
In Production Example 2, rubber particles (B1), which are non-slip particles, were produced.
The following substances were charged into an 8 L polymerization apparatus with a stirrer.
Deionized water 200 parts Polyoxyethylene lauryl ether Sodium phosphate 0.05 parts Sodium formaldehyde Sulfoxylate 0.11 parts Ethethylenediamine tetraacetate-2-sodium 0.004 parts Ferrous sulfate 0.001 parts In-polymerizer Was sufficiently replaced with nitrogen gas to make it substantially oxygen-free, and then the internal temperature was adjusted to 40 ° C., and the raw material mixture of acrylic rubber particles (rubber particles) (butyl acrylate 90%, methyl methacrylate 10%). To 45 parts by weight of the monofunctional monomer composed of the above, 0.45 parts of allyl methacrylate and 0.041 parts of cumene hydroperoxide) 45.491 parts were continuously added over 225 minutes. 20 minutes, 40 minutes, and 60 minutes after the start of addition of the raw material mixture, sodium polyoxyethylene lauryl ether phosphate (polyoxyethylene lauryl ether phosphoric acid (manufactured by Toho Chemical Industry Co., Ltd., trade name: Phosphanol RD-510Y) 0.2 parts each of sodium salt) was added to the polymerization machine. After the addition was completed, polymerization was continued for another 0.5 hours to obtain rubber parts particles. The polymerization conversion rate was 98.6%.
Then, the internal temperature was set to 60 ° C., 0.2 part of sodium formaldehyde sulfoxylate was charged, and then the raw material mixture of the shell layer (methyl methacrylate 57.8%, butyl acrylate 4%, benzyl methacrylate 38) was charged. To 55 parts by weight of the monofunctional monomer consisting of .2%, 0.3 parts of t-dodecyl mercaptan and 0.254 parts of cumenehydroperoxide) were continuously added over 210 minutes. Polymerization was continued for another hour to obtain a graft copolymer latex (rubber particles having a core-shell structure). The polymerization conversion rate was 100.0%. The obtained latex was salted out with magnesium sulfate, coagulated, washed with water, and dried to obtain white powdery rubber particles (B1).
The average particle size of the rubber particles (B1) was 121 nm. The graft ratio of the rubber particles (B1) was 56%.

<Production Example 3: Production of Multilayer Particles (B2)>
In Production Example 3, multilayer structure particles (B2), which are particles that impart smoothness to the film, were produced.
The following substances were charged into a glass reactor.
Ion-exchanged water 125 parts borate 0.47 parts sodium carbonate 0.05 parts polyoxyethylene lauryl ether phosphoric acid 0.0042 parts After sufficiently replacing the inside of the polymerization machine with nitrogen gas, the internal temperature is set to 80 ° C. and the monomer is used. 25% of the mixture consisting of 17.5 parts (3% n-butyl acrylate, 97% methyl methacrylate), 0.17 parts allyl methacrylate and 0.065 parts t-butyl hydroperoxide was collectively put into a polymerization machine. After that, 0.00645 parts of 5% sodium formaldehyde sulfoxypolymer, 0.0056 parts of ethylenediaminetetraacetate-2-sodium, and 0.0014 parts of ferrous sulfate were added, and 15 minutes later, t-butyl was added. 0.022 part of hydroperoxide was added, and the polymerization was continued for another 15 minutes. Then, 0.013 parts of a 2% aqueous sodium hydroxide solution was added. The remaining 75% was added continuously over 30 minutes. 30 minutes after the completion of the addition, 0.0069 parts of 69% t-butyl hydroperoxide was added and kept at the same temperature for 30 minutes to complete the polymerization. The polymerization conversion rate was 98%.
Then, the obtained polymer latex was kept at 80 ° C. in a nitrogen stream, and 0.0346 parts of sodium hydroxide and 0.0519 parts of potassium persulfate were added. Then, a mixture consisting of 32.5 parts of monomer (82% n-butyl acrylate, 18% styrene), 0.97 parts of allyl methacrylate and 0.3 parts of polyoxyethylene lauryl ether phosphoric acid was continuously added over 74 minutes. did. It was then held for 45 minutes to complete the polymerization. The average particle size of the obtained polymer was 260 nm, and the polymerization conversion rate was 99%.
Further, the obtained polymer latex was kept at 80 ° C., 0.0097 parts of potassium persulfate and 0.05 parts of sodium hydroxide were added, and then 50 parts of a monomer (90% methyl methacrylate, n-butyl acrylate). A mixture consisting of 10%) was added continuously over 150 minutes. After the addition of the mixture was completed, the mixture was held for 1 hour to obtain a latex of multilayer structure particles (B2).
The average particle size of the multilayer structure particles was 380 nm, and the polymerization conversion rate was 99%.
The latex of the obtained multilayer structure particles was salted out with magnesium sulfate, solidified, washed with water, and dried to obtain white powdery multilayer structure particles (B2).

<Manufacturing Example 4: Production of Resin Pellets (C1)>
Using a twin-screw extruder with a diameter of 75 mm, the temperature control zone of the extruder is set to 255 ° C., the screw rotation speed is 70 rpm, 85 parts by weight of acrylic resin (A1), and white powdery rubber particles (B1). A mixture of 15 parts by weight and 0.5 parts by weight of white powdery multilayer structure particles (B2) was supplied at a rate of 150 kg / hr. The resin that came out as a strand from the die provided at the outlet of the extruder was cooled in a water tank and pelletized with a pelletizer. The glass transition temperature Tg of the resin pellet (C1) was 119 ° C.

<Manufacturing Example 5: Production of resin pellets (C2)>
A resin pellet (C2) was produced in the same manner as the resin pellet production (C1) except that the rubber particles (B1) were not added.

<Example 1>
The resin pellet (C1) (glass transition temperature Tg 119 ° C.) obtained in Production Example 5 was used as the thermoplastic resin composition, dried at 80 ° C. for 4 hours in a dryer, and then supplied to a φ90 mm single-screw extruder. did. Screen meshes were placed at the extruder outlet in the order of # 40, # 100, # 400, # 400, # 100, # 40 from the extruder side. The resin was heated and melted at the outlet of the extruder so that the resin temperature became 250 ° C., and the molten resin was extruded into a T-die having a width of 1850 mm via a gear pump. At this time, the die set temperature was adjusted so that the resin temperature at the T-die outlet was 260 ° C.
The discharged molten resin is taken up at a line speed of 15 m / min, sandwiched between a cast roll whose temperature is adjusted to 100 ° C. and a touch roll whose temperature is adjusted to 100 ° C., cooled and solidified, and then taken up by a take-up roll and a winding core. The end portion of 200 mm was slit in the front, and a film raw fabric having a thickness of 60 μm was obtained on the take-up core. After that, with a rewinder that knurls the ends while rewinding the original fabric, the film is conveyed to both ends under the conditions of a line speed of 40 m / min, a knurling temperature of 140 ° C., and a knurled pressing pressure of 0.2 MPa. Knurling was applied to the range of. No meandering of the film during the rewinding process was observed, and no blocking-induced defects were observed when the film was wound, resulting in a good winding appearance. At this time, the protruding heights of the crosslinked polymerized particles on the central portion of the film and the surfaces (both ends of the film) in contact with the knurling convex, and the surface roughness are as shown in Table 1.

<Example 2>
The same procedure as in Example 1 was carried out except that the resin temperature at the T-die outlet was changed from 260 ° C. to 250 ° C. No meandering of the film during the rewinding process was observed, and no blocking-induced defects were observed when the film was wound, resulting in a good winding appearance. At this time, the protruding heights of the crosslinked polymerized particles on the central portion of the film and the surfaces (both ends of the film) in contact with the knurling convex, and the surface roughness are as shown in Table 1.

<Example 3>
The same procedure as in Example 1 was carried out except that C3 prepared in Production Example 6 was used as the thermoplastic resin. No meandering of the film during the rewinding process was observed, and no blocking-induced defects were observed when the film was wound, resulting in a good winding appearance. Table 1 shows the protrusion heights and surface roughness of the crosslinked polymerized particles on the central portion of the film and the surfaces (both ends of the film) in contact with the convex knurling at this time.

<Comparative example 1>
The procedure was the same as in Example 1 except that the rewinder was not knurled. As a result, winding misalignment occurred remarkably, and blocking-induced defects were slightly observed.

<Comparative example 2>
The same procedure as in Example 1 was carried out except that the resin pellet (C1) was changed to the thermoplastic resin (A1). As a result, although there was no winding deviation, defects caused by blocking occurred severely.

<Comparative example 3>
As the knurling condition, the same procedure as in Example 2 was carried out except that the knurling temperature was changed from 140 ° C. to 120 ° C. As a result, no defects caused by blocking occurred, but winding misalignment occurred slightly.

<Comparative example 4>
As the knurling conditions, the same procedure as in Example 2 was carried out except that the knurling temperature was changed from 140 ° C. to 130 ° C. and the knurling pressure was changed from 0.2 MPa to 0.05 MPa. As a result, no defects caused by blocking occurred, but winding misalignment occurred slightly.

Table 1 summarizes the results of Examples and Comparative Examples.

According to Examples 1 to 3, in an optical film in which a film is formed using a thermoplastic resin composition containing crosslinked polymer particles and has a nerling processed portion, contact surfaces (both ends) in contact with the nerling convex. It can be seen that when the protruding height of the crosslinked polymer particles is 0.0 times or more and 0.5 times or less of the major axis of the crosslinked polymer particles, winding deviation and blocking-induced defects are satisfactorily suppressed. ..

According to Comparative Example 1, it can be seen that when the optical film is not knurled, it is difficult to suppress both winding misalignment and blocking-induced defects.
According to Comparative Example 2, when the optical film is knurled, it is easy to suppress the winding deviation, but when the material of the optical film does not contain the crosslinked polymer particles, it is difficult to suppress the defects caused by blocking.
According to Comparative Examples 3 and 4, even if the film is formed by using the thermoplastic resin composition containing the crosslinked polymer particles and the optical film has a knurled portion, the contact surface (which is in contact with the nerling convex) ( It can be seen that when the protruding height of the crosslinked polymer particles at (both ends) exceeds 0.5 times the major axis of the crosslinked polymer particles, it is difficult to suppress the winding deviation.

10 Extruder 11 T Die 12 Die Outlet 13 Thermoplastic Resin Composition 14 Elastic Roll 15 Cast Roll

Claims (5)

An optical film composed of a thermoplastic resin composition containing crosslinked polymer particles and having a knurled portion in a part in the width direction.
The crosslinked polymer particles include core particles having a rubber portion having a degree of crosslink of 2.3% by weight or more and 4.0% by weight or less, and core-shell type multilayer structure particles composed of a shell layer.
The degree of cross-linking is the ratio of the weight of the polyfunctional monomer having two or more functionalities to the total mass of the monomer used for producing the material of the rubber portion.
The protruding height of the crosslinked polymer particles on the surface of the optical film that has not been subjected to the nerling process and is in contact with the narling convex of the narling-processed portion when the optical film is wound into a roll. An optical film whose size is 0.2 times or more and 0.5 times or less the major axis of the crosslinked polymer particles. The optical film according to claim 1, wherein the arithmetic average roughness Ra of the surface of the contact surface is 1 nm or more and 50 nm. The optical film according to claim 1 or 2, wherein the thermoplastic resin composition contains an acrylic resin. The optical film according to any one of claims 1 to 3, wherein the protruding height of the crosslinked polymer particles in a portion other than the nerling processed portion is 0.3 times or more and 0.8 times or less the major axis of the crosslinked polymer particles. A method for producing an optical film from a raw film made of a thermoplastic resin composition containing crosslinked polymer particles.
The knurling temperature during knurling with respect to the raw film is Tg + 10 ° C. or higher and Tg + 40 ° C. or lower (Tg is the glass transition temperature of the thermoplastic resin composition), the knurling treatment speed is 20 m / min or more and 50 m / min or lower, and A method in which the knurling pressure is 0.1 MPa or more and 0.5 MPa or less.

Images