JP2005263866A - Maleimide-based resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a maleimide-based copolymer resin film having high physical characteristics and high optical characteristics compatible with each other, to provide an optical film, to provide a polarizer protecting film, to provide a retardation film, and to provide a polarizing plate. <P>SOLUTION: This maleimide-based copolymer resin film is formed by dispersing a rubbery polymer in a matrix formed out of a maleimide-based copolymer resin in a state of having a dispersion diameter of ≤100 μm, wherein the film has a parallel light transmittance of ≥ 87%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a maleimide-based resin film, an optical film, a polarizer protective film, a retardation plate, and a polarizing plate that have both high physical characteristics and optical characteristics.

As a transparent material, glass has been used so far, but an optical film made of a resin film has been used from the viewpoint of productivity, weight reduction, cost, and the like.
The use of such an optical film is extremely wide, but in recent years, in particular, a polarizer protective film or a plate used for a polarizing plate of a liquid crystal display device such as a desktop electronic computer, an electronic watch, a word processor, an automobile, and a machine instrument. Application as a phase difference plate is expected.

The polarizing plate is usually composed of a polarizer obtained by adsorbing iodine or a dichroic dye on a stretched and oriented polyvinyl alcohol resin, and a polarizer protective film adhered to both surfaces of the polarizer. The optical film used as a polarizer protective film has excellent optical properties such as light transmission, has sufficient mechanical strength to prevent contraction of a highly shrinkable polarizer, and can withstand high temperatures applied in the manufacturing process. It is required to have heat resistance.

As such a polarizer protective film, an optical film made of triacetyl cellulose has been used. However, an optical film made of triacetylcellulose has high optical properties but insufficient heat resistance and moisture resistance. When used in a high temperature or high humidity atmosphere for a long time, the degree of polarization is significantly reduced. There has been a problem that peeling of the film, a decrease in transparency due to hydrolysis of triacetylcellulose, and the like occur and the performance of the polarizing plate is lowered.
In addition, a retardation plate is used for the polarizing plate for the purpose of compensating for distortion of light when passing through a liquid crystal substance. As such a phase difference plate, what consists of resin excellent in transparency and heat resistance like polycarbonate resin and polysulfone resin was used.

On the other hand, the use of a maleimide resin film as an optical film has attracted attention. The maleimide-based resin film exhibits excellent heat resistance in addition to excellent optical properties such as characteristics such as low expression of birefringence with respect to stress and high transparency. However, the maleimide resin film has a problem that it is very brittle and it is difficult to reduce the thickness. Moreover, even if it tried to manufacture by an extrusion method, since the film will fracture | rupture if a taking-up speed becomes high, there also existed a problem also in productivity. Further, in the production of a liquid crystal display device, a step of attaching a polarizing plate to a liquid crystal cell is performed. However, it is inevitable that bubbles or foreign substances are involved in the attachment, or that the polarizing plate itself has a defect. Therefore, the inspection is performed after the step of attaching the polarizing plate to the liquid crystal cell, and if there is a defect, the polarizing plate is removed and the expensive liquid crystal cell is reused.
A process called rework is performed. In order to enable such reuse, it is necessary to be able to easily peel off the polarizing plate at the time of peeling, but in a polarizing plate using a polarizer protective film or retardation plate made of a brittle maleimide resin film, There was also a problem that the maleimide resin film was broken at the time of peeling and the reworkability was poor.

On the other hand, in Patent Document 1, the maleimide component is 30 to 98 mol% of the whole polymer, the other specific constituent components are 70 to 2 mol% of the whole polymer, and the weight average molecular weight in terms of polystyrene is 1. 0.5-99.5 parts by weight of a maleimide copolymer that is × 10 ³ or more and 5 × 10 ⁶ or less, and an elastomer that has a refractive index difference within 0.01 at a wavelength of 589 nm is 99.5-0.
. A resin composition comprising 5 parts by weight is disclosed. This is to improve the brittleness, which was a problem of maleimide resin films, while maintaining high optical performance by blending an elastomer with a very small difference in refractive index with maleimide copolymer resin. To do. However, such a material having a refractive index difference of 0.01 or less has a very narrow selection range, and the present situation is that the combinations that can be realized are limited to exceptional cases. Moreover, transparency and mechanical properties are not sufficient, and it has been difficult to use for polarizer protective film applications.

JP-A-5-140379

An object of this invention is to provide the maleimide-type resin film, optical film, polarizer protective film, phase difference plate, and polarizing plate which balanced the high physical characteristic and optical characteristic in view of the said present condition.

In the present invention, a rubber polymer is 5 μm in a matrix made of a maleimide copolymer resin.
A maleimide resin film dispersed with the following dispersion diameter, which is JIS K 7113
Is a maleimide resin film having a tensile elongation at break of 4% or more measured according to the above.
The present invention is described in detail below.

As a result of intensive studies, the present inventors, in a matrix composed of a maleimide copolymer resin,
By dispersing the rubbery polymer with a dispersion diameter of 5 μm or less, it is possible to improve physical properties such as brittleness while maintaining high optical properties even when there is a certain difference in refractive index, and also bleeding out The present inventors have found that a maleimide-based resin film that does not occur can be obtained, and have completed the present invention.

As a result of further intensive studies, the present inventors have focused on components other than maleimide in maleimide copolymer resins, and if a rubbery polymer having high affinity with this component is selected, a maleimide copolymer It has also been found that a maleimide resin film having both excellent physical properties and optical properties can be obtained because it has excellent affinity with the whole resin and can be dispersed with a dispersion diameter of 5 μm or less. That is, when designing a maleimide resin film, the types and ratios of polymerizable monomers for constituting components other than the maleimide component in the maleimide copolymer resin, and the types and blending amounts of rubber polymers to be blended By adjusting, the range of material selection can be dramatically increased, and material design suitable for the application can be performed.

In this specification, the maleimide copolymer resin means a copolymer containing at least a component represented by the following general formula (1) (hereinafter also referred to as a maleimide component) and other components. .

式（１）中、Ｒ^１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、
フェニル基、アルキル置換フェニル基又はハロゲン置換フェニル基を示す。

In Formula (1), R ¹ is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms,
A phenyl group, an alkyl-substituted phenyl group or a halogen-substituted phenyl group is shown.

The maleimide copolymer resin is produced by copolymerizing a polymerizable monomer for constituting the maleimide component and a polymerizable monomer for constituting a component other than the maleimide component by a conventionally known method. can do.

The polymerizable monomer for constituting the maleimide component is not particularly limited, for example,
N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, Ni-
Propylmaleimide, Nn-butylmaleimide, Ni-butylmaleimide, Ns-
Butylmaleimide, Nt-butylmaleimide, Nn-pentylmaleimide, Nn-
Hexylmaleimide, Nn-heptylmaleimide, Nn-octylmaleimide, N-
Laurylmaleimide, N-stearylmaleimide, N-cyclopropylmaleimide, N-
Cyclobutylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N
-(2-methylphenyl) maleimide, N- (2-ethylphenyl) maleimide, N- (
2-Isopropylphenyl) maleimide, N- (3-methylphenyl) maleimide, N-
(3-ethylphenyl) maleimide, N- (4-methylphenyl) maleimide, N- (4
-Ethylphenyl) maleimide, N- (2,6-dimethylphenyl) maleimide, N- (
2,6-diethylphenyl) maleimide, N- (2,6-diisopropylphenyl) maleimide, N- (2,4,6-trimethylphenyl) maleimide, N-carboxyphenylmaleimide, N- (2-chlorophenyl) maleimide, N such as N- (2,6-dichlorophenyl) maleimide, N- (2-bromophenyl) maleimide, N- (perbromophenyl) maleimide, N- (2,4-dimethylphenyl) maleimide, p-tolylmaleimide
-Substituted maleimides. Among these, N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide or N-cyclohexylmaleimide is preferable. These polymerizable monomers may be used independently and may use 2 or more types together.

It does not specifically limit as a polymerizable monomer for comprising components other than the said maleimide component, For example, isobutene, 2-methyl-1-butene, 2-methyl-1-pentene, 2-methyl-1-hexene, 1 -Methyl-1-heptene, 1-isooctene, 2-methyl-1-octene, 2-ethyl-1-pentene, 2-methyl-2-butene, 2-methyl-2-pentene, 2-methyl-2-hexene And other olefins. For example, when isobutene is used as a polymerizable monomer for constituting a component other than the maleimide component, the resulting maleimide copolymer resin has a maleimide component and an isobutene component. These polymerizable monomers may be used independently and may use 2 or more types together.

The minimum with preferable content of the said maleimide component in the said maleimide-type copolymer resin is 30 mol%, and a preferable upper limit is 70 mol%. If it is less than 30 mol%, the resulting maleimide-based resin film may not exhibit sufficient heat resistance and transparency. If it exceeds 70 mol%, the affinity with the rubbery polymer will be low and sufficient. Improvement effects such as brittleness may not be obtained. A more preferable lower limit is 40 mol%, and a more preferable upper limit is 60 mol%.

In this specification, the rubbery polymer means a polymer composed of a hard segment and a soft segment, and the glass transition temperature of the soft segment is 25 ° C. or lower.
The rubbery polymer is not particularly limited. For example, a styrene-butadiene block copolymer, a hydrogenated styrene-butadiene block copolymer, a styrene-isoprene block copolymer, a hydrogenated styrene-isoprene block copolymer, Styrene elastomer such as styrene-isobutylene block copolymer, low crystalline polybutadiene resin, ethylene-propylene elastomer, styrene graft ethylene-propylene elastomer, thermoplastic polyester elastomer, ethylene ionomer resin, butadiene graft acrylonitrile-styrene (ABS) And the like, and the like. These rubbery polymers may be modified with specific functional groups such as epoxy groups, carboxyl groups, hydroxyl groups, amino groups, acid anhydride groups, oxazoline groups, and have a specific structure. The side chain it has may be added by graft polymerization or the like. Of these, styrene-based elastomers are preferred.

The maleimide copolymer resin and the rubbery polymer preferably have a refractive index difference of 0.2 or less. If it exceeds 0.2, the transparency, residual retardation, etc. of the resulting maleimide-based resin film may deteriorate, or optical distortion or the like may easily occur. More preferably, it is 0.1 or less, More preferably, it is 0.05 or less, Most preferably, it is 0.03 or less.

When the maleimide copolymer resin and the rubber polymer are melt mixed, the viscosity of the maleimide copolymer resin (η maleimide) at the molding temperature and the viscosity of the rubber polymer (
The ratio (η rubber / η maleimide) to (η rubber) is preferably close to 1. When the viscosity ratio is close to 1, it becomes easy to finely disperse the rubbery polymer in the maleimide copolymer resin. Preferably it is 0.2-3.0, More preferably, it is 0.4-2.0. When the haze value of the obtained maleimide resin film is 0.5% or less, it is particularly preferable that η rubber / η maleimide is 0.5 to 1.8. In addition, the viscosity here means the viscosity when the shear rate is measured at 24.3 at the actual molding temperature.

As mentioned above, paying attention to components other than maleimide in the maleimide copolymer resin,
If a rubbery polymer having a high affinity with this component is selected, the rubbery polymer is excellent in affinity with the whole maleimide copolymer resin, and the rubber polymer is dispersed in the maleimide copolymer resin with a dispersion diameter of 5 μm or less. And a maleimide resin film having both high physical properties and optical properties.
For example, when the maleimide copolymer resin contains an isobutene component, it is preferable to use a styrene-isobutene-styrene copolymer (SIBS) as the rubbery polymer. The maleimide copolymer resin containing an isobutene component and SIBS have an isobutene component in common, and therefore have excellent affinity. In addition, since SIBS has a relatively close refractive index to maleimide copolymer resin, using SIBS with maleimide copolymer resin containing isobutene component achieves both extremely high optical properties and physical properties. An optical film is obtained.

In SIBS, the preferred lower limit of the amount of isobutene component is 50% by weight, and the preferred upper limit is 90% by weight. If it is less than 50% by weight, sufficient affinity with the maleimide copolymer resin may not be obtained, and if it exceeds 90% by weight, an improvement effect such as sufficient brittleness may not be obtained. . A more preferred lower limit is 70% by weight, and a more preferred upper limit is 85% by weight.

For example, when the maleimide copolymer resin contains an isobutene component, it is preferable to use a rubber polymer having an acrylonitrile-styrene copolymer component in the side chain. Since the acrylonitrile-styrene copolymer component is extremely excellent in affinity with the isobutene component, the rubbery polymer having the acrylonitrile-styrene copolymer component in the side chain is a maleimide copolymer resin containing the isobutene component. Excellent affinity with. Therefore, if a maleimide copolymer resin containing an isobutene component and a rubbery polymer having an acrylonitrile-styrene copolymer component in the side chain are used, an optical film having both extremely high optical properties and physical properties can be obtained. can get.

The rubbery polymer having the acrylonitrile-styrene copolymer component in the side chain is not particularly limited. For example, it is easy to select one having a relatively small difference in refractive index, so that the acrylonitrile-styrene copolymer component is A styrene-isobutene-styrene copolymer (SIBS) having a side chain, a styrene-ethylene-styrene copolymer (SEBS) having an acrylonitrile-styrene copolymer component in a side chain, and the like are preferable.

It does not specifically limit as a method of manufacturing the rubber-like polymer which has the said acrylonitrile-styrene copolymer component in a side chain, A conventionally well-known method can be used. For example, when manufacturing SIBS having an acrylonitrile-styrene copolymer component in the side chain and SEBS having an acrylonitrile-styrene copolymer component in the side chain, the isobutene component of SIBS,
For example, a method of forming an acrylonitrile-styrene copolymer side chain by graft polymerization on the ethylene component portion of SEBS by a conventionally known method such as a chain transfer method or an ionizing radiation irradiation method may be mentioned. Further, as described in JP-A-6-128491, a vinyl monomer containing a radical polymerizable organic peroxide and a radical polymerization initiator in a suspension of acrylonitrile-styrene copolymer in water. A monomer solution is added, and heating is performed under the condition that decomposition of the radical polymerization initiator does not substantially occur, and the acrylonitrile-styrene copolymer is impregnated with the vinyl monomer, the radical polymerizable organic peroxide, and the radical polymerization initiator. Then, the temperature of the aqueous suspension is increased, and a vinyl monomer and a radical polymerizable organic peroxide are copolymerized in an acrylonitrile-styrene copolymer to obtain a grafted precursor. The grafted precursor directly
A method of melt mixing with IBS or SEBS can also be suitably used.

When using a styrene-based elastomer such as SIBS or SEBS as the rubber polymer,
The preferable lower limit of the number average molecular weight of the styrene-based elastomer is 50,000, and the preferable upper limit is 10
It is 0,000. If it is less than 50,000, the dispersibility in the maleimide copolymer resin becomes insufficient, and the effect of modifying the physical properties by adding the rubbery polymer may not be obtained. The melt viscosity at the time of blending with the maleimide copolymer resin is too high, and the formability is poor and a uniform film may not be obtained. A more preferred lower limit is 80,000, and a more preferred upper limit is 5
The upper limit is 100,000, and a more preferable lower limit is 100,000, and a more preferable upper limit is 400,000.

The preferable lower limit of the amount of the rubber polymer added to 100 parts by weight of the maleimide copolymer resin is 5 parts by weight, and the preferable upper limit is 40 parts by weight. If the amount is less than 5 parts by weight, the effect of improving the physical properties of the resulting maleimide-based resin film may not be obtained. If the amount exceeds 40 parts by weight, the optical properties may be inferior. More preferably, the lower limit is 10 parts by weight, and the more preferable upper limit is 30 parts by weight.

The maleimide resin film of the present invention preferably further contains a thermoplastic resin.
By containing the thermoplastic resin, the affinity between the maleimide copolymer resin and the rubbery polymer is further improved, and the optical properties of the resulting maleimide resin film are improved.

The maleimide resin film of the present invention, if necessary, within a range that does not hinder the purpose of the present invention,
2,6-di-t-butyl-4-methylphenol, 2- (1-methylcyclohexyl)-
Antioxidants such as 4,6, dimethylphenol, 2,2-methylene-bis- (4-ethyl-6-tert-butylphenol), tris (di-nonylphenyl phosphite); pt-butylphenyl salicylate, 2,2′-dihydroxy-4-methoxy-benzophenone,
UV absorbers such as 2- (2′-dihydroxy-4′-m-octoxyphenyl) benzotriazole; lubricants such as paraffin phenos and hydrogenated oil; stearoadipropylpropyldimethyl-
You may contain antistatic agents, such as (beta) -hydroxyethyl ammonium trate.

In the maleimide resin film of the present invention, the lower limit of the tensile elongation at break measured according to JIS K 7113 is 4%. If it is less than 4%, it tends to break, so that when used as a polarizer protective film, the reworkability of the polarizing plate is inferior. A preferred lower limit is 6%, and a more preferred lower limit is 8%. The upper limit of tensile fracture elongation is not particularly limited, but the preferable upper limit is 40%. If it exceeds 40%, a dimensional change of the polarizing plate becomes large when a durability test, particularly a heat resistance deterioration test is performed, and a change in optical performance or peeling from the liquid crystal cell may easily occur. A more preferred upper limit is 35%.

The maleimide resin film of the present invention preferably has a tensile elastic modulus of 900 MPa or more as measured according to JIS K7113. When it is less than 900 MPa, when used as a polarizer protective film, shrinkage of the polarizer may not be suppressed. More preferably, it is 1000 MPa or more. The tensile modulus is preferably high and there is no upper limit.

It is preferable that the maleimide resin film of the present invention can be rolled up at room temperature without breaking at a tension of 500 N / 650 mm. As a result, mass production becomes possible, and the cost can be greatly reduced.

The maleimide resin film of the present invention preferably has a photoelastic coefficient of 2.0 × 10 ⁻¹¹ Pa ⁻¹ or less. When the maleimide resin film of the present invention is used as a polarizer protective film, various external forces such as a contraction stress of the polarizer, a stress due to distortion at the time of bonding, and a stress due to distortion at the time of incorporation into a display are applied. Especially in high temperature and high humidity environment,
The contraction stress of the polarizer is large. The photoelastic coefficient is calculated by the following formula (4), and is a value representing a change in birefringence with respect to an external force.
Photoelastic coefficient (c) = birefringence (Δn) / stress (σ) (4)
That is, the smaller the photoelastic coefficient, the smaller the amount of change in birefringence due to external force. If the photoelastic coefficient exceeds 2.0 × 10 ⁻¹¹ Pa ⁻¹ , the optical performance largely changes due to deformation due to external force, so that it is difficult to use for optical film applications. More preferably 1.
0 × 10 ⁻¹¹ Pa ⁻¹ or less.

In the maleimide resin film of the present invention, the preferable lower limit of the parallel light transmittance is 87%.
If it is less than 87%, it is difficult to use it for applications such as a polarizer protective film. More preferably, it is 89% or more.
In the maleimide resin film of the present invention, the preferred lower limit of the haze value is 5%. 5
If it exceeds 50%, it may cause light leakage when used in applications such as a polarizer protective film. More preferably, it is 3% or less, more preferably 1% or less, and particularly preferably 0.5% or less.

The maleimide resin film of the present invention preferably further has a residual retardation of 3 nm or less and an optical axis deviation of ± 10 ° or less with respect to the major axis (MD) direction. If the residual phase difference exceeds 3 nm or the optical axis deviation exceeds ± 10 ° with respect to the long axis direction, the cause of light leakage etc. when the maleimide resin film of the present invention is used as a polarizer protective film or the like. It may become. Although it is preferable that the residual phase difference and the optical axis deviation are smaller, if the residual phase difference is 1 nm or less, the magnitude of the optical axis deviation can be ignored, and a process for inspecting the optical axis deviation is not required. The manufacturing process when manufacturing a polarizer protective film or the like can be greatly simplified, which is more preferable.
The optical axis means a direction in which the refractive index of incident light becomes the largest, generally an axis called a slow axis, and the optical axis shift is the long axis direction of the optical axis. It means an angle shift. The major axis direction is the flow direction of extrusion molding when a film is produced by extrusion molding, for example.

The thickness of the maleimide resin film of the present invention is not particularly limited, but the average film thickness is 10
When it is 0 μm or less, it is preferable that the above optical performance and physical characteristics are satisfied. More preferably, when the average film thickness is 70 μm or less, and more preferably the average film thickness is 50 μm or less, the above optical performance and physical characteristics are satisfied. Average film thickness 50
If the above optical performance and physical properties are satisfied at μm or less, the cost can be greatly reduced and the value is extremely high. The lower limit of the average film thickness is not particularly limited, but the average film thickness is preferably 25 in consideration of use as an optical film, a polarizer protective film, or the like.
When the average film thickness is 20 μm or more, more preferably, the above optical performance and physical characteristics are satisfied.

The method for producing the maleimide-based resin film of the present invention is not particularly limited. Conventional methods such as melt-kneading and extrusion-molding the maleimide-based copolymer resin, the rubbery polymer, and each component added as necessary. It can be produced by a known method.

The maleimide resin film of the present invention can be suitably used as an optical film because physical properties such as brittleness are greatly improved while maintaining high optical performance as described above.
An optical film comprising the maleimide resin film of the present invention is also one aspect of the present invention.

The maleimide resin film of the present invention can also be suitably used as a polarizer protective film. A polarizer protective film comprising the maleimide resin film of the present invention is also one aspect of the present invention.
The polarizer protective film of the present invention may be subjected to various surface treatments according to the use of the liquid crystal display to be used. The surface treatment is not particularly limited, and examples thereof include a clear hard coat treatment, an AG (anti-reflection) treatment, and an AR (anti-reflection) treatment.
The polarizer protective film of the present invention is a corona discharge treatment or the like so that the contact angle with water on the surface is about 40 to 50 degrees for the purpose of improving the bonding property with the polarizer within a range not impairing the optical performance. May be applied.

The maleimide resin film of the present invention can be suitably used as a retardation plate that compensates for distortion of light when passing through a liquid crystal material by imparting orientation by uniaxial or biaxial stretching. The retardation film made of the maleimide resin film of the present invention is also one of the first aspects of the present invention. Furthermore, a polarizing plate obtained by directly laminating the retardation plate of the present invention on at least one surface of a polarizer is also one aspect of the present invention.

Although it does not specifically limit as temperature in the case of performing said extending | stretching, It is preferable that it is the glass transition temperature +20 degreeC of the maleimide-type copolymer resin-the glass transition temperature of the said maleimide-type copolymer resin. If it is outside this range, the film may be broken on the low temperature side, or a desired retardation value may not be obtained on the high temperature side. More preferably, the glass transition temperature of the maleimide copolymer resin is + 1 ° C. to the glass transition temperature of the maleimide copolymer resin + 10 ° C.

Although it does not specifically limit as a draw ratio in the case of performing the said extending | stretching, When extending | stretching in the direction of the melt extrusion of a film, a preferable minimum is 1.05 time and a preferable upper limit is 5.0 times. 1.
If it is less than 05 times, the amount of deformation is too small to obtain sufficient retardation, and if it exceeds 5.0 times, the film may be broken. A more preferred lower limit is 1.
1 time, and a more preferable upper limit is 2.5 times. Moreover, when extending | stretching in the direction perpendicular | vertical to the direction of the melt extrusion of a film, a preferable minimum is 1.2 times and a preferable upper limit is 3.0 times, A more preferable minimum is 1.5 times and a more preferable upper limit Is 2.5 times.

According to the present invention, in view of the above situation, it is possible to provide a maleimide resin film, an optical film, a polarizer protective film, a retardation plate, and a polarizing plate that have both high physical properties and optical properties.

(Example 1)
Maleimide copolymer resin (manufactured by Tosoh Corporation, TP: maleimide component content 50% by weight, isobutene component content 50% by weight, refractive index 1.53) and styrene-isobutene-styrene copolymer (Kanebuchi Chemical Industry Co., Ltd.) SIBSTAR103T: styrene content 30% by weight, isobutene content 70% by weight, refractive index 1.53) at a weight ratio of 90:10 to a twin-screw melt extruder, melt mixed at 286 ° C., pelletized, 110 A maleimide copolymer resin composition was prepared by predrying at 3 ° C. for 3 hours.
Using the obtained maleimide copolymer resin composition, a maleimide resin film having an average thickness of 40 μm was obtained by an extrusion molding method.

(Example 2)
A dispersion was prepared by suspending in water in which polyvinyl alcohol was dissolved using acrylonitrile-styrene copolymer as a suspending agent. To this dispersion, a styrene solution containing t-butylperoxymethacryloyloxyethyl carbonate as a radical polymerizable organic peroxide and benzoyl peroxide as a radical polymerization initiator was added. After stirring at a temperature of 60 to 65 ° C. for 2 hours, the temperature was raised to 80 to 85 ° C. and further stirred for 7 hours to obtain a grafted precursor.
The obtained grafting precursor and styrene-isobutene-styrene copolymer (SIBS) are melt-mixed to obtain a styrene-isobutene-styrene copolymer (SIBS) having an acrylonitrile-styrene copolymer component in the side chain. Was made. The refractive index of SIBS having the obtained acrylonitrile-styrene copolymer component in the side chain was 1.54.

Maleimide-based copolymer resin (manufactured by Tosoh Corporation, TP: maleimide component content 50% by weight, isobutene component content 50% by weight, refractive index 1.53) and the obtained acrylonitrile-styrene copolymer component in the side chain The SIBS having a weight ratio of 90:10 was supplied to a biaxial melt extruder, melted and mixed at 286 ° C., pelletized, and pre-dried at 110 ° C. for 3 hours to prepare a maleimide copolymer resin composition.
Using the obtained maleimide copolymer resin composition, a maleimide resin film having an average thickness of 40 μm was obtained by an extrusion molding method.

(Example 3)
A dispersion was prepared by suspending in water in which polyvinyl alcohol was dissolved using acrylonitrile-styrene copolymer as a suspending agent. To this dispersion, a styrene solution containing t-butylperoxymethacryloyloxyethyl carbonate as a radical polymerizable organic peroxide and benzoyl peroxide as a radical polymerization initiator was added. After stirring at a temperature of 60 to 65 ° C. for 2 hours, the temperature was raised to 80 to 85 ° C. and further stirred for 7 hours to obtain a grafted precursor.
The obtained grafting precursor and styrene-ethylene-styrene copolymer (SEBS) are melt-mixed to obtain a styrene-ethylene-styrene copolymer (SEBS) having an acrylonitrile-styrene copolymer component in the side chain. Was made. Acrylonitrile obtained-
The refractive index of SEBS having a styrene copolymer component in the side chain was 1.53.

Maleimide-based copolymer resin (manufactured by Tosoh Corporation, TP: maleimide component content 50% by weight, isobutene component content 50% by weight, refractive index 1.53) and the obtained acrylonitrile-styrene copolymer component in the side chain The SEBS having a weight ratio of 90:10 was supplied to a biaxial melt extruder, melted and mixed at 286 ° C., pelletized, and pre-dried at 110 ° C. for 3 hours to prepare a maleimide copolymer resin composition.
Using the obtained maleimide copolymer resin composition, a maleimide resin film having an average thickness of 40 μm was obtained by an extrusion molding method.

(Comparative Example 1)
Using a maleimide copolymer resin (TPS, TP: maleimide component content 50% by weight, isobutene component content 50% by weight, refractive index 1.53), an average thickness of 4 is obtained by an extrusion method.
A 0 μm maleimide resin film was obtained.
At this time, the film was broken at the normal take-up speed. However, by adjusting the take-up speed and the like, it was possible to secure an amount of the film for use in the test.

The films prepared in Examples 1 to 3 and Comparative Example 1 were evaluated by the following methods. The results are shown in Table 1.

(1) Evaluation of dispersion state of rubbery polymer After dyeing a maleimide resin film with ruthenium tetroxide or the like, about 0.05 μm in the flow direction (MD) and width direction (TD) during extrusion molding using a microtome. Then, each cross section was observed using a transmission electron microscope (JEM-1200EX II, manufactured by JEOL Ltd.) and photographed. Based on this photograph, the dispersion diameter of the rubbery polymer was determined.

(2) Measurement of tensile elastic modulus and tensile fracture elongation According to JIS K 7113, measurement was performed using TENSILON (manufactured by Orientec) under the following conditions.
Distance between chucks 150mm
Film width 20mm
Tensile speed 20mm / min

(3) Measurement of total light transmittance, parallel light transmittance, and haze value Using a haze meter (TC-HIIIDKP, manufactured by Tokyo Denshoku Co., Ltd.), JIS K 7105
The measurement was performed according to the above.

According to the present invention, in view of the above situation, it is possible to provide a maleimide resin film, an optical film, a polarizer protective film, a retardation plate, and a polarizing plate that have both high physical properties and optical properties.

Claims (10)

A maleimide resin film in which a rubbery polymer is dispersed with a dispersion diameter of 5 μm or less in a matrix composed of a maleimide copolymer resin, and the tensile fracture elongation measured according to JIS K 7113 is 4% or more. A maleimide-based resin film characterized by being. 2. The maleimide resin film according to claim 1, wherein the maleimide copolymer resin contains an olefin component, and the rubbery polymer is a styrene elastomer. The maleimide resin film according to claim 2, wherein the olefin component is an isobutene component. The maleimide resin film according to claim 3, wherein the styrene elastomer is a styrene-isobutene-styrene copolymer. 4. The maleimide resin film according to claim 3, wherein the rubber polymer has an acrylonitrile-styrene copolymer component in the side chain. 6. The maleimide resin film according to claim 1, wherein the maleimide copolymer resin and the rubbery polymer have a difference in refractive index of 0.2 or less. . An optical film comprising the maleimide resin film according to claim 1, 2, 3, 4, 5 or 6. A polarizer protective film comprising the maleimide resin film according to claim 1, 2, 3, 4, 5 or 6. A retardation film comprising the maleimide resin film according to claim 1, 2, 3, 4, 5 or 6. A polarizing plate comprising a polarizer and the retardation plate according to claim 9 directly laminated on at least one surface of the polarizer.