JP2007178504A - Film for display unit and method for manufacturing film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film for a display unit, the optical quality level of which is so excellent that a flicker is not generated and to provide a method for manufacturing the film for the display unit. <P>SOLUTION: The film for the display unit is a film formed by a solution film-forming method. When thickness data are sampled from the film at intervals of 0.25 mm over a section of 300 mm, the thickness variation in an optional section of 5 mm is ≤0.5 μm and a phase difference Rth of the thickness direction is ≤10 nm. The method for manufacturing the film for the display unit comprises the steps of: dissolving a polymer (A) in a solvent (B) to prepare a polymer solution (C); and forming the film from the polymer solution by the solution film-forming method. The viscosity of the polymer solution (C) at 25°C is 7-600 Pa-s and the boiling point of the solvent (B) is 30-80°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a film for a display device excellent in optical quality and a method for producing the same.

  Conventionally, a film for a display device such as a polarizer protective film has been widely used because of excellent thickness unevenness and flatness of the resulting film.

In recent years, with the increase in definition of display devices, there has been a demand for further improvement even if the quality has been satisfied in the past. In particular, a defect called “fluctuation” has become a problem.
Fluctuation is a phenomenon in which when an image is observed through a film, the image appears distorted, and is a defect unique to a film obtained by a solution casting method. When the fluctuation is large, when used as an image display element, the visibility may be lowered.

  Regarding the improvement of fluctuation, in Patent Document 1, it is pointed out that the change in thickness per unit distance has a great influence on the fluctuation between the thickness fluctuation and the visibility of fluctuation. In order to solve this, it is possible to suppress the pneumatic vibration of 5 to 100 Hz near the casting die, or increase the film forming speed to widen the thickness unevenness pitch, and the thickness fluctuation of the frequency observed visually does not occur. A membrane method is proposed. However, this method is insufficient to improve the stripe-like fluctuation generated horizontally in the film forming direction.

Conventional polarizer protective films have been proposed to reduce luminance unevenness by controlling the in-plane retardation, but the thickness direction retardation of the film used as the polarizer protective film may adversely affect the viewing angle of the display device. It has become clear. On the other hand, a film used as an optical material generally requires high light transmittance and low haze, and an acrylic film can be suitably used.
For example, Patent Document 2 discloses a solution film-forming method for an acrylic film. However, depending on this method, there is no description regarding fluctuations that are peculiar to the solution film-forming method, and the obtained film also needs to be improved.
JP 2002-189127 A JP 2003-334831 A

  In view of the background of such conventional technology, the present invention is to provide a film for a display device excellent in optical quality such as no “fluctuation” and a method for producing the same.

  The present invention employs the following means in order to solve such problems. That is, the film for a display device of the present invention is a film formed by a solution casting method, and when the thickness data is sampled every 0.25 mm over a 300 mm section, the thickness in an arbitrary 5 mm section The variation is 0.5 μm or less, and the thickness direction retardation Rth is 10 nm or less.

  Such a method for producing a film for a display device includes a polymer solution (C) prepared by dissolving a polymer (A) in a solvent (B), and a method for producing a film by a solution casting method. The solution viscosity at 25 ° C. of C) is 7 Pa · s or more and 600 Pa · s or less, and the boiling point of the solvent (B) is 30 ° C. or more and 80 ° C. or less.

  According to this invention, since it is excellent in optical quality, the film for display apparatuses suitable for optical members, such as an image display element, can be provided.

  The present invention, for the display device film excellent in optical quality such as the above-mentioned problem, that is, there is no "fluctuation", intensively studied, the film formed by the solution film forming method, so far not seen It was made possible to control both the thickness variation and the thickness direction retardation Rth to be extremely small, and for the first time, it was sought to solve the above-mentioned problems all at once.

  That is, as a result of intensive studies, the present inventors have found that “fluctuation” can be expressed by thickness fluctuation in an arbitrary 5 mm section when thickness data is sampled every 0.25 mm over a 300 mm section. Here, it can be said that “fluctuation” is good when the thickness variation is 0.5 μm or less. In the present invention, the thickness variation needs to be 0.5 μm or less. If the thickness variation in the film plane exceeds 0.5 μm, the fluctuation is so great that it cannot be suitably used as a film for a display device. Further, it is more preferable that the variation in thickness is 0.3 μm or less because fluctuations cannot be almost recognized. Such thickness variation is preferably as small as possible, but in reality, the lower limit is about 0.01 μm.

  The thickness was continuously measured using an Anritsu Co., Ltd. film thickness tester “KG601A” and an electronic micrometer “K306C”. The thickness fluctuation, that is, “fluctuation” is considered to be caused by the flow of the coating film in the initial stage of drying, and in order to make this less than 0.5 μm, it is necessary to optimally control the solution viscosity and the solvent. These will be described in detail later.

  In the film for a display device of the present invention, the thickness direction retardation Rth needs to be 10 nm or less. That is, when the thickness direction retardation Rth is 10 nm or less, the viewing angle when used as a film for a display device is good. The thickness direction retardation Rth is preferably 3 nm or less, more preferably 1 nm or less.

  The thickness direction retardation Rth is a value measured using an automatic birefringence meter “KOBRA-21ADH” manufactured by Oji Scientific Co., Ltd.

 This retardation Rth in the thickness direction is mainly caused by the structure of the polymer. To achieve this, three-dimensional refraction including not only the in-plane orientation of the polymer but also the orientation in the thickness direction is included. It is necessary to form a film using a polymer having a small rate difference. Examples of such a polymer include an acrylic polymer described later.

The thickness of the film for a display device of the present invention is preferably 15 μm or more and 100 μm or less. When the thickness is less than 15 μm, the film strength decreases and the processability deteriorates. On the other hand, when the thickness exceeds 100 μm, when the film is formed by the solution casting method, the time until the coating film shows self-supporting property becomes long and fluctuation may occur.
Moreover, it is preferable that the film for display apparatuses of this invention has a glass transition temperature (Tg) of 120 degreeC or more. More preferably, it is 130 ° C. or higher. When the glass transition temperature (Tg) is less than 120 ° C., the glass transition temperature (Tg) may not be used in a high temperature environment such as a projector or an in-vehicle display device. When performing a coating process, etc., it may be deformed by heat and flatness may be impaired. Further, when the glass transition temperature Tg is low, the drying temperature is limited due to the heat resistance problem of the film in the solvent drying step, and it takes a long time to dry the solvent, which may deteriorate the productivity.

The glass transition temperature referred to here is an intermediate value determined according to JIS K7121 (1987) using a differential scanning calorimeter (DSC-7 model manufactured by Perkin Elmer) at a temperature rising rate of 20 ° C./min. It is the point glass transition temperature (T _mg ).

  Next, a detailed description will be given of a film forming method for causing the thickness fluctuation in each 5 mm section to be 0.5 μm or less when the thickness data is sampled every 0.25 mm over the 300 mm section.

  In the conventional film forming method, the fluidity of the coating film at the initial stage of drying is a problem, and fluctuations due to drying air and drying unevenness occur. The present inventors have found that it is necessary to optimally control the solution viscosity and the solvent in order to improve such fluctuation. More specifically, in order to suppress fluctuation, it is necessary to control the fluidity of the coating film immediately after casting. That is, the coating film immediately after casting is affected by drying wind and drying unevenness, resulting in uneven thickness, and fluctuations are likely to occur. Therefore, in order to suppress fluctuations, the coating film after casting exhibits self-supporting properties. In the meantime, it is necessary to maintain the low fluidity of the coating film and to prevent the flatness of the film from being deteriorated by dry air. That is, the key point of fluctuation improvement is the investigation of the viscosity of the polymer solution and its solvent. Here, self-supporting means that the film can be kept in shape without a support.

  First, the viscosity of the polymer solution will be described.

  The solution viscosity at 25 ° C. of the polymer solution (C) used for production of the film for a display device of the present invention needs to be 7 Pa · s or more and 600 Pa · s or less. When the solution viscosity is less than 7 Pa · s, since the fluidity of the coating film is too high, there is a problem that fluctuations increase due to the influence of drying air or the like. In general, a solution having a viscosity exceeding 600 Pa · s has a problem that uniform casting is difficult and the thickness accuracy tends to deteriorate. The viscosity of the polymer solution (C) is more preferably 7 Pa · s to 20 Pa · s, and particularly preferably 8 Pa · s to 15 Pa · s. The viscosity of the polymer solution (C) is measured using an RB type R80U viscometer manufactured by Toki Sangyo Co., Ltd.

  Next, the solvent will be described.

  In the production of the film for a display device of the present invention, in order to maintain a state where the fluidity of the coating film is low until the coated film after casting exhibits self-supporting property, the temperature of the coating film is low. Need to maintain. Furthermore, it is important to shorten the time until the solvent is efficiently volatilized even when the temperature of the coating film is low and the coating film exhibits self-supporting properties. In order to achieve such conditions, a specific solvent is selected. That is, as the specific solvent (B), it is necessary to selectively use a solvent component having a boiling point of 30 ° C. or higher and 80 ° C. or lower so as to be 50% by weight or more in the solvent (B). Specific examples include tetrahydrofuran, acetone, 2-butanone, dichloromethane, and the like. When the boiling point of the solvent component occupying 50% by weight or more in the solvent (B) exceeds 80 ° C., the time required for the initial drying until the fluidity of the coating film is lost becomes long, and fluctuation may occur. Moreover, since the high temperature initial drying is required, the fluidity | liquidity of a coating film becomes high and a fluctuation | variation may arise. If the boiling point is less than 30 ° C., the solvent is very volatile at room temperature, which causes a problem of bumping defects during film formation. As the solvent (B), one type of solvent may be used, or two or more types of solvents may be mixed and used. When two or more kinds of solvents are mixed and used, it is necessary to contain 50% by weight or more of a solvent having a boiling point of 30 ° C. or higher and 80 ° C. or lower. When the solvent is less than 50% by weight, there is a problem that the drying time becomes long and fluctuations occur or bumping defects occur.

  From these conditions, it is most preferable that 80% by weight or more and 100% by weight or less of the solvent (B) used in the present invention uses acetone and / or 2-butanone. Conventionally, dichloromethane is often used as a solvent for solution casting, but dichloromethane has a large latent heat of vaporization, and when it volatilizes, the temperature of the coating film is drastically reduced, which tends to cause condensation. And fluctuations may occur. On the other hand, since acetone and 2-butanone have low latent heat of vaporization, there is no rapid decrease in the coating film temperature, so that condensation does not easily occur and fluctuation due to uneven drying is unlikely to occur. When acetone and / or 2-butanone is less than 80% by weight, if the solvent to be mixed is a solvent such as dichloromethane having a high latent heat of vaporization, the coating temperature may decrease due to the latent heat of vaporization and condensation may occur. If the solvent to be mixed is a poor solvent in which the polymer (A) does not dissolve, the solubility is lowered, and the polymer solution (C) is not a uniform solution and the coating property may be deteriorated. In the case of mixing a solvent having a high boiling point, there is a problem that the drying time becomes long for the volatilization of the solvent.

  By controlling the viscosity and the solvent as described above, when the thickness data is sampled every 0.25 mm over the 300 mm section, the thickness fluctuation in an arbitrary 5 mm section can be set to 0.5 μm or less.

  Other preferable modes of film formation will be described.

  The polymer (A) concentration in the polymer solution (C) is preferably 15% by mass or more and 40% by mass or less. When the concentration is less than 15% by mass, the fluidity of the coating film increases and fluctuations may increase. Further, it is not preferable because it takes a long time to dry the solvent. If the concentration exceeds 40% by mass, the solubility may deteriorate and it may be difficult to obtain a uniform coating film.

  Moreover, you may add a drying adjuvant, a release agent, etc. for the purpose of acceleration | stimulation of drying of a solvent (B), or the peelability improvement from a base material.

  The polymer solution (C) after dissolution is preferably filtered to remove foreign substances and gel-like substances. By removing the foreign matter, defects and haze are reduced, so that it can be suitably used as an optical film. It is preferable that the filtration accuracy can remove foreign matters of 50 μm or more. More preferably, it is 10 μm, and most preferably 1 μm. It is preferable to perform filtration step by step with a plurality of filters having different filtration accuracy because the filtration life is extended. Filtration can be performed at a temperature of 25 ° C. or higher and 100 ° C. or lower. The filter can be appropriately selected and used from, for example, sintered metal, porous ceramic, sand, and wire mesh.

  Next, although the example of the film forming method of the film for display apparatuses is demonstrated, this invention is not limited to this. The solution casting method includes a dry-wet method, a dry method, a wet method, etc., and any method may be used to form a film, but here, the dry method will be described as an example.

  In the case of forming a film by a dry method, a polymer solution (C) is cast from a die onto a support such as a drum, an endless belt, or a process film to form a coating film, and a solvent (B ) Is volatilized, and the coating film is dried until it has self-holding properties. Thereafter, a heat treatment is performed to obtain a film having a residual solvent (B) concentration of less than 2% by mass. If the surface of the drum, endless belt, process film, etc. used is as smooth as possible, a film with little fluctuation and low haze can be obtained.

  In order to suppress fluctuations, it is preferable to maintain a low fluidity state of the coating film until the coated film exhibits self-supporting property and prevent deterioration of the flatness of the film due to dry air or the like. . For this reason, it is preferable that the temperature of the polymer solution (C) which cools a nozzle | cap | die and piping and casts is in the range of 10 to 25 degreeC. When the temperature of the polymer solution (C) is lower than 10 ° C., the solubility of the polymer (A) may be poor, the dissolution state may be uneven, and uniform casting may not be possible. When the temperature of a polymer solution (C) is higher than 25 degreeC, the fluidity | liquidity of a coating film becomes high and it becomes easy to produce fluctuation. The temperature of the polymer solution (C) is more preferably 15 ° C to 25 ° C.

  It is also important to reduce the coating thickness unevenness by reducing the pulsation of the solution flow rate, the mechanical vibration of the casting part, and the uneven speed of the support to improve the fluctuations that occur perpendicular to the film forming direction. is there. Furthermore, in order to prevent an increase in the haze of the film due to condensation due to the latent heat of vaporization of the solvent (B), the humidity in the vicinity of the coating part can be lowered, and heating from the back surface of the support by hot air, a heating roll, a heater, etc. It is valid. In this case, when hot air is applied locally, vibration is generated in the support and causes fluctuations. Therefore, when hot air is used, it is preferable to enlarge the air outlet and reduce the wind speed.

  Subsequently, in the drying step, the coating film is dried until it exhibits self-supporting properties on the substrate. In order to improve the fluctuation, it is preferable to dry the coating film until it shows self-supporting property while maintaining the low fluidity of the coating film. When the boiling point of the solvent (B) is bp (° C.), it is preferably carried out in the range of (bp−50 ° C.) to (bp + 20 ° C.). When the temperature of the drying process is low, the time until the self-supporting property is exhibited becomes long, and the fluctuation may increase. If it is too high, bumping may occur and it may not be used as an optical film. The temperature of the drying step is more preferably in the range of (bp-30 ° C.) to (bp + 10 ° C.), and more preferably (bp-20 ° C.) to bp. It is preferable that the solvent (B) density | concentration in the film after a drying process is 10-30 mass%, and the time which a normal drying process requires is about 1 second-60 seconds. In order to remove the solvent (B) efficiently, it is preferable to raise the drying temperature stepwise.

  Next, the film after the drying step is subjected to a heat treatment step to volatilize the solvent in the film. When the glass transition temperature of the polymer (A) is Tg, it is preferable to perform the heat treatment in a temperature range of (Tg−50 ° C.) to (Tg + 50 ° C.). If the temperature of the heat treatment is too low, it takes time to dry the solvent (B) and the productivity is deteriorated. If the temperature is too high, foaming defects may occur when the residual solvent (B) in the film volatilizes. The solvent (B) concentration in the film after the heat treatment step is preferably less than 2% by mass, and the time required for the heat treatment is usually about 5 to 60 minutes. When the solvent (B) concentration is 2% by mass or more, the solvent (B) may be eluted when used as a product. Since the rigidity of the film is excellent, the residual solvent (B) is more preferably less than 1% by mass. The smaller the residual solvent, the better. However, it is difficult to remove all of the solvent in the film produced by the solution casting method, and in reality, the lower limit is about 0.001% by mass.

  For example, when the obtained film is formed using the process film as a base material, the film may be wound while being laminated, or may be peeled off from the base material during or at the end of the drying process. In the case of peeling from the substrate, it is preferable to stack a protective film and wind it up, since scratches are suppressed.

The obtained film may be subjected to a treatment such as stretching and lamination of a hard coat layer or an antireflection layer in a subsequent step.
The film for a display device of the present invention needs to have a thickness direction retardation Rth of 10 nm or less. The polymer is not limited as long as it provides such a thickness direction retardation Rth. For example, an acrylic polymer can be exemplified, among the structural units represented by the following structural formulas (a) to (c). Use of an acrylic polymer containing at least one or more has properties suitable for optical applications such as high transparency, low birefringence, low Rth, weather resistance, and moldability, and is suitable as a film for a display device. .

(In the above formulas, R ¹ and R ² represent the same or different hydrogen atoms, an alkyl group having 1 to 5 carbon atoms, a carboxyl group, or a carboxyalkyl group having 2 to 5 carbon atoms. , X ¹ and X ² represent the same or different CH ₂ or C═O, X ³ represents O or NR ³ , R ³ represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a carboxyl group Represents a group or a carboxyalkyl group having 2 to 5 carbon atoms.)
In particular, from the viewpoint of heat resistance, R ¹ and R ² are preferably hydrogen, a methyl group or a carboxymethyl group, particularly preferably a methyl group, and X ¹ and X ² are preferably C═O. From the viewpoint of transparency, X ³ is preferably O.

(In the above formula, R ^{4 represents} a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a carboxyl group, or a carboxyalkyl group having 2 to 5 carbon atoms.)
In particular, from the viewpoint of heat resistance, R ⁴ is preferably a methyl group.

(In the above formula, R ⁵ represents a substituent containing an alicyclic structure having 6 to 15 carbon atoms.)
In particular, from the viewpoint of low hygroscopicity, R ⁵ is preferably a substituent represented by the following structural formulas (e) and (f).

Among the structural formulas (a) to (c), when an acrylic polymer containing a cyclized structure represented by the following structural formula (d) is used, the transparency, heat resistance, and productivity are excellent. It is preferable because a film excellent in optical isotropy can be obtained.

(In said formula, R < ⁶ >, R < ⁷ > represents the same or different hydrogen atom or a C1-C5 alkyl group.)
In particular, from the viewpoint of heat resistance, R ⁶ and R ⁷ are preferably hydrogen or a methyl group, and particularly preferably a methyl group.

  Next, although the example of the manufacturing method of the acrylic polymer (A) containing the glutaric anhydride unit represented by the said structural formula (d) is demonstrated, this invention is not limited to this.

  That is, the unsaturated carboxylic acid monomer (g) and the unsaturated carboxylic acid alkyl ester monomer (h) that give the glutaric anhydride unit represented by the structural formula (d) by the subsequent heating step, and other When the vinyl monomer unit is included, the vinyl monomer (i) giving the unit is polymerized to obtain a copolymer (a), and then the copolymer (a) is converted into an appropriate catalyst. It can be produced by heating in the presence or absence of and causing an intramolecular cyclization reaction by dealcoholization and / or dehydration. In this case, the carboxyl group of the unsaturated carboxylic acid unit of 2 units is typically dehydrated by heating the copolymer (a), or the adjacent unsaturated carboxylic acid unit and unsaturated carboxylic acid alkyl ester unit. 1 unit of the glutaric anhydride unit is generated by the elimination of the alcohol. The unsaturated carboxylic acid monomer (g) used in this case is not particularly limited, and can be copolymerized with another vinyl compound (i), which is represented by the following structural formula (j). Carboxylic acid monomers can be used.

(In the above formula, R ⁸ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)
In particular, acrylic acid and methacrylic acid are preferable from the viewpoint of excellent thermal stability, and methacrylic acid is more preferable. These can be used alone or in combination of two or more thereof. The unsaturated carboxylic acid monomer (g) represented by the above structural formula (j) is copolymerized and then subjected to an intramolecular cyclization reaction to form a structure represented by the above structural formula (d). Of unsaturated carboxylic acid units.

  Further, the unsaturated carboxylic acid alkyl ester monomer (h) is not particularly limited, but preferred examples include those represented by the following structural formula (k).

(In the above formula, R ⁹ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ¹⁰ represents a hydrogen atom or an aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms.)
Of these, acrylates and / or methacrylates having an aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms or a hydrocarbon group having a substituent are particularly preferred in terms of excellent thermal stability. is there. The unsaturated carboxylic acid alkyl ester monomer represented by the structural formula (k) is copolymerized and then subjected to an intramolecular cyclization reaction to form a structure represented by the structural formula (d). Of unsaturated carboxylic acid alkyl ester units.

  Preferable specific examples of the unsaturated carboxylic acid alkyl ester monomer (h) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and n-butyl (meth) acrylate. T-butyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2- (meth) acrylic acid 2- Hydroxyethyl, 3-hydroxypropyl (meth) acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth) acrylate and 2,3,4,5-tetrahydroxypentyl (meth) acrylate Among them, methyl methacrylate is most preferably used. These can be used alone or in combination of two or more thereof.

  In the production of the acrylic polymer (a) used in the present invention, other vinyl monomers (i) such as styrene, acrylamide and methacrylamide may be used as long as the effects of the present invention are not impaired. However, monomers that do not contain an aromatic ring can be more preferably used in terms of transparency, birefringence, and chemical resistance. These may be used alone or in combination of two or more.

  As for the polymerization method of the acrylic polymer (A), basically, polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. by radical polymerization can be used, but the solution is less in terms of impurities. Polymerization, bulk polymerization and suspension polymerization are particularly preferred.

  The polymerization temperature is not particularly limited, but from the viewpoint of color tone, a monomer mixture containing an unsaturated carboxylic acid monomer and an unsaturated carboxylic acid alkyl ester monomer is polymerized at a polymerization temperature of 95 ° C. or less. Is preferred. The lower limit of the polymerization temperature is not particularly limited as long as the polymerization proceeds, but is usually 50 ° C. or higher from the viewpoint of productivity considering the polymerization rate. For the purpose of improving the polymerization yield or polymerization rate, the polymerization temperature can be raised as the polymerization proceeds. The polymerization time is not particularly limited as long as it is a sufficient time to obtain the required degree of polymerization, but is preferably in the range of 60 to 360 minutes from the viewpoint of production efficiency.

  In the present invention, the preferred proportion of these monomer mixtures used in the production of the acrylic polymer (a) is that the unsaturated carboxylic acid monomer (g) is 5 to 100 parts by weight based on the monomer mixture. 50 parts by mass, more preferably 9-33 parts by mass, the unsaturated carboxylic acid alkyl ester monomer (h) is preferably 50-95 parts by mass, more preferably 67-91 parts by mass, and others copolymerizable therewith When the vinyl monomer (i) is used, the preferable ratio is 0 to 5 parts by mass, and the more preferable ratio is 0 to 3 parts by mass.

  When the unsaturated carboxylic acid monomer amount (g) is less than 5 parts by mass, the amount of glutaric anhydride units represented by the structural formula (d) generated by heating the copolymer (a) is There is a tendency that the effect of improving the heat resistance of the acrylic film of the present invention is reduced. On the other hand, when the unsaturated carboxylic acid monomer amount (g) exceeds 50 parts by mass, a large amount of unsaturated carboxylic acid units tend to remain after the cyclization reaction by heating the copolymer (a). , Colorless transparency and retention stability tend to decrease.

  The acrylic polymer (A) used for the acrylic film of the present invention preferably has a mass average molecular weight of 80,000 to 150,000. The acrylic polymer (a) having such a molecular weight is obtained by controlling the copolymer (a) to a desired molecular weight, that is, a mass average molecular weight of 50,000 to 150,000 in advance during the production of the copolymer (a). This can be achieved. When the mass average molecular weight exceeds 150,000, there is a tendency of coloring during cyclization in the subsequent step. On the other hand, when the mass average molecular weight is less than 50,000, the mechanical strength of the acrylic film tends to decrease.

  Glutaric anhydride obtained by heating the copolymer (a) used in the production of the acrylic polymer (a) preferably used in the present invention and (i) dehydration and / or (b) intramolecular cyclization reaction by dealcoholization The method for producing the thermoplastic polymer containing the unit is not particularly limited, but it can be produced by passing through a heated extruder having a vent or in an inert gas atmosphere or in an apparatus that can be heated and degassed under vacuum. The manufacturing method is preferable from the viewpoint of productivity.

  The temperature during cyclization is not particularly limited as long as (i) dehydration and / or (b) dealcoholization causes an intramolecular cyclization reaction, but is preferably in the range of 180 to 300 ° C, particularly 200 to 200 ° C. A range of 280 ° C is preferred.

  Further, the cyclization time at this time is not particularly limited and can be appropriately set according to the desired copolymer composition, but is usually 1 minute to 60 minutes, preferably 2 minutes to 30 minutes, especially 3 to 20 minutes. The range of is preferable. In particular, the length / diameter ratio (L / D) of the extruder screw is preferably 40 or more in order to secure a heating time for allowing sufficient intramolecular cyclization reaction to proceed using an extruder. When an extruder with a short L / D is used, a large amount of unreacted unsaturated carboxylic acid units remain, so that the reaction proceeds again during the heat molding process, and there is a tendency for silver and bubbles to be seen in the molded product and molding retention. Sometimes the color tends to deteriorate significantly.

  Furthermore, in the present invention, when the copolymer (a) is heated by the above method or the like, one or more of acid, alkali and salt compounds may be added as a catalyst for promoting the cyclization reaction to glutaric anhydride. it can. The addition amount is not particularly limited, and is preferably about 0.01 to 1 part by mass with respect to 100 parts by mass of the copolymer (a).

  In view of heat resistance, the acrylic polymer (A) preferably has a glass transition temperature (Tg) of 120 ° C. or higher. The method for raising the glass transition temperature is not particularly limited, but it is effective to increase the content of the cyclized structural unit in the acrylic polymer (A), for example, as represented by the structural formula (d). It is. It is also effective to orient the obtained film by stretching.

  As the acrylic polymer (A) of the present invention, a copolymer comprising a glutaric anhydride unit represented by the structural formula (d) and an unsaturated carboxylic acid alkyl ester unit can be preferably used. The content of the unsaturated carboxylic acid alkyl ester unit and the glutaric anhydride unit is not particularly limited. However, since heat resistance is improved, the total of the unsaturated carboxylic acid alkyl ester unit and the glutaric anhydride unit is 100 masses. Parts, preferably 50 to 90 parts by weight of unsaturated carboxylic acid alkyl ester units and 10 to 50 parts by weight of glutaric anhydride units, more preferably 55 to 80 parts by weight of unsaturated carboxylic acid alkyl ester units. And 20 to 45 parts by mass of glutaric anhydride units. When the glutaric anhydride unit is less than 10 parts by mass, not only the heat resistance improving effect is reduced, but also sufficient low birefringence (optical isotropy) and chemical resistance tend not to be obtained.

In addition, an infrared spectrophotometer or a proton nuclear magnetic resonance (1H-NMR) measuring instrument is generally used for quantification of each component unit in the acrylic polymer (A) of the present invention. In infrared spectroscopy, glutaric anhydride units, absorption of 1800 cm ^-1 and 1760 cm ^-1 are characteristic can be distinguished from unsaturated carboxylic acid units and unsaturated carboxylic acid alkyl ester unit. In the 1H-NMR method, for example, in the case of a copolymer consisting of a glutaric anhydride unit, methacrylic acid, and methyl methacrylate, the attribution of the spectrum in dimethyl sulfoxide heavy solvent is 0.5 to 1.5 ppm. The peak is methacrylic acid, methyl methacrylate and α-methyl group hydrogen of glutaric anhydride ring compound, the peak of 1.6 to 2.1 ppm is hydrogen of the methylene group of the polymer main chain, and the peak of 3.5 ppm is methacrylic acid The hydrogen of methyl carboxylic acid ester (—COOCH ₃ ), the peak at 12.4 ppm can determine the copolymer composition from the hydrogen of carboxylic acid of methacrylic acid and the integral ratio of the spectrum. In addition to the above, in the case of a copolymer containing styrene as another copolymer component, hydrogen of an aromatic ring of styrene is seen at 6.5 to 7.5 ppm, and the copolymer is similarly obtained from the spectral ratio. The composition can be determined.

  In addition, the acrylic polymer (A) of the present invention may contain other unsaturated carboxylic acid units and / or other copolymerizable vinyl monomer units in the acrylic polymer (A). .

  The amount of other unsaturated carboxylic acid units contained in 100 parts by mass of the thermoplastic polymer is preferably 10 parts by mass or less, that is, 0 to 10 parts by mass, more preferably 0 to 5 parts by mass, most preferably Preferably it is 0-1 mass part. When the unsaturated carboxylic acid unit exceeds 10 parts by mass, the colorless transparency and the residence stability tend to decrease.

  Further, the amount of other copolymerizable vinyl monomer units is preferably 5 parts by mass or less, that is, in the range of 0 to 5 parts by mass, more preferably 0 to 5 parts by mass, in 100 parts by mass of the thermoplastic polymer. 3 parts by mass. In particular, when an aromatic vinyl monomer unit such as styrene is contained and the content exceeds the above range, colorless transparency, optical isotropy, and chemical resistance tend to decrease.

  In the present invention, by dispersing the elastic particles (ii) in the above acrylic polymer (a), the elongation and toughness are improved without significantly detracting from the excellent properties of the acrylic polymer (a). Workability can be imparted. As the elastic particles (i), there is a multilayer structure polymer called a so-called core-shell type composed of a layer containing one or more rubber polymers and one or more layers composed of different polymers. Some elastic particles (ii-1) or elastic particles (ii-2) that are graft copolymers obtained by copolymerizing a monomer mixture comprising a vinyl monomer in the presence of a rubbery polymer. ) And the like can be preferably used, and elastic particles (I-1) which is a multilayer structure polymer are more preferable.

  The number of layers constituting the elastic particles (I-1), which is a core-shell type multilayer polymer used in the present invention, is not particularly limited, and may be two or more. Although it may be three or more layers or four or more layers, it is necessary to be a multilayer structure polymer having a rubber elastic body layer formed of at least one rubber polymer inside.

  In the elastic particles (I-1) which is the multilayer structure polymer of the present invention, the type of the rubber elastic body layer is not particularly limited as long as it is composed of a polymer component having rubber elasticity. Good. For example, a rubber composed of a polymer obtained by polymerizing an acrylic component, a silicone component, a styrene component, a nitrile component, a conjugated diene component, a urethane component or an ethylene component, a propylene component, an isobutene component, and the like can be given. Preferred rubber elastic bodies include, for example, acrylic components such as ethyl acrylate units and butyl acrylate units, silicone components such as dimethylsiloxane units and phenylmethylsiloxane units, styrene components such as styrene units and α-methylstyrene units, and acrylonitrile. It is a rubber elastic body composed of nitrile components such as units and methacrylonitrile units and conjugated diene components such as butanediene units and isoprene units. A rubber elastic body composed of a combination of two or more of these components is also preferable. For example, (1) acrylic components such as ethyl acrylate units and butyl acrylate units, dimethylsiloxane units and phenylmethylsiloxane units (2) rubber elastic bodies composed of acrylic components such as ethyl acrylate units and butyl acrylate units and styrene components such as styrene units and α-methylstyrene units, (3) ) Rubber elastic bodies composed of acrylic components such as ethyl acrylate units and butyl acrylate units and conjugated diene components such as butanediene units and isoprene units, and (4) acrylic components such as ethyl acrylate units and butyl acrylate units. , Dimethylsiloxane units and phenyl Such as styrene component configured rubber elastic body such as silicone component and styrene units and α- methyl styrene unit, such as a chill siloxane units and the like. In addition to these components, a rubber elastic body obtained by crosslinking a copolymer composed of a crosslinking component such as a divinylbenzene unit, an allyl acrylate unit and a butylene glycol diacrylate unit is also preferable.

  In the elastic particles (I-1) which is the multilayer structure polymer of the present invention, the type of layers other than the rubber elastic layer is particularly limited as long as it is composed of a polymer component having thermoplasticity. However, it is preferably a polymer component having a glass transition temperature higher than that of the rubber elastic body layer. Polymers having thermoplastic properties include unsaturated carboxylic acid alkyl ester units, unsaturated carboxylic acid units, unsaturated glycidyl group-containing units, unsaturated dicarboxylic acid anhydride units, aliphatic vinyl units, and aromatic vinyls. Examples include polymers containing at least one unit selected from system units, vinyl cyanide units, maleimide units, unsaturated dicarboxylic acid units and other vinyl units. Among them, unsaturated carboxylic acids A polymer containing at least one unit selected from an alkyl ester unit, an unsaturated glycidyl group-containing unit, and an unsaturated dicarboxylic acid anhydride unit is preferable, and further, an unsaturated glycidyl group-containing unit and an unsaturated dicarboxylic acid A polymer containing at least one unit selected from anhydride-based units is more preferable.

  Although it does not specifically limit as a monomer used as the raw material of the said unsaturated carboxylic-acid alkylester type | system | group unit, (meth) acrylic-acid alkylester is used preferably. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, (meth) acrylic N-hexyl acid, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, stearyl (meth) acrylate, octadecyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, ( Chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2,3,4,5,6 (meth) acrylic acid -Pentahydroxyhexyl, 2,3,4,5-tetrahydroxypentyl (meth) acrylate, amino acid acrylate Examples include ethyl, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, phenylaminoethyl methacrylate, and cyclohexylaminoethyl methacrylate, and from the viewpoint that the effect of improving impact resistance is large ( Methyl methacrylate is preferably used. These units can be used alone or in combination of two or more.

  The unsaturated carboxylic acid monomer is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, maleic acid, and further a hydrolyzate of maleic anhydride. Acrylic acid is particularly excellent in terms of thermal stability. Methacrylic acid is preferable, and methacrylic acid is more preferable. These can be used alone or in combination.

  The monomer used as the raw material for the unsaturated glycidyl group-containing unit is not particularly limited, and is glycidyl (meth) acrylate, glycidyl itaconate, diglycidyl itaconate, allyl glycidyl ether, styrene-4-glycidyl ether. And 4-glycidylstyrene, and glycidyl (meth) acrylate is preferably used from the viewpoint that the effect of improving impact resistance is great. These units can be used alone or in combination of two or more.

  Examples of the monomer used as a raw material for the unsaturated dicarboxylic acid anhydride unit include maleic anhydride, itaconic anhydride, glutaconic anhydride, citraconic anhydride, and aconitic anhydride, and the effect of improving impact resistance. From the standpoint of large, maleic anhydride is preferably used. These units can be used alone or in combination of two or more.

  Examples of the monomer that is a raw material for the aliphatic vinyl-based unit include ethylene, propylene, and butadiene. Examples of the monomer that is a raw material for the aromatic vinyl-based unit are styrene, α-methylstyrene, 1 -Vinyl naphthalene, 4-methyl styrene, 4-propyl styrene, 4-cyclohexyl styrene, 4-dodecyl styrene, 2-ethyl-4-benzyl styrene, 4- (phenylbutyl) styrene, halogenated styrene, etc. Acrylonitrile, methacrylonitrile, ethacrylonitrile, etc. are used as the raw material for the vinyl-based unit, and maleimide, N-methylmaleimide, N-ethylmaleimide are used as the monomer for the maleimide-based unit. N-propylmaleimide, N-isopropylmaleimide, Examples of monomers that can be used as raw materials for the unsaturated dicarboxylic acid units include maleic acid and maleic acid such as -cyclohexylmaleimide, N-phenylmaleimide, N- (p-bromophenyl) maleimide, and N- (chlorophenyl) maleimide. Monoethyl ester, itaconic acid, phthalic acid, and the like, which are monomers used as raw materials for the other vinyl units, include acrylamide, methacrylamide, N-methylacrylamide, butoxymethylacrylamide, N-propylmethacrylamide, N- Vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamine, N-methylallylamine, p-aminostyrene, 2-isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acryloyl-oxazoline, and 2-styrene Examples include ril-oxazoline, and these monomers can be used alone or in combination of two or more.

  In the elastic particles (I-1), which is a multilayer structure polymer containing the rubbery polymer of the present invention, the type of the outermost layer is not particularly limited, and the unsaturated carboxylic acid alkyl ester unit, Saturated carboxylic acid unit, unsaturated glycidyl group-containing unit, aliphatic vinyl unit, aromatic vinyl unit, vinyl cyanide unit, maleimide unit, unsaturated dicarboxylic acid unit, unsaturated dicarboxylic anhydride unit And at least one selected from polymers containing other vinyl units and the like. Among them, unsaturated carboxylic acid alkyl ester units, unsaturated carboxylic acid units, unsaturated glycidyl group-containing units and At least one selected from polymers containing a saturated dicarboxylic acid anhydride-based unit is preferred, and further, an unsaturated carboxylic acid alkyl ester. System unit, a polymer containing an unsaturated carboxylic acid-based units are more preferable.

  Furthermore, when the outermost layer in the elastic particle (ii-1), which is the multilayer structure polymer, is a polymer containing an unsaturated carboxylic acid alkyl ester unit and an unsaturated carboxylic acid unit, by heating As in the production of the acrylic polymer (a) of the present invention described above, it was found that the intramolecular cyclization reaction proceeds to produce the glutaric anhydride unit represented by the structural formula (d). . Therefore, the elastic particles (I-1), which is a multilayer structure polymer having a polymer containing an unsaturated carboxylic acid alkyl ester unit and an unsaturated carboxylic acid unit in the outermost layer, is blended in the acrylic polymer (a). In the acrylic polymer (a) that becomes a continuous phase (matrix phase) by heating and kneading under appropriate conditions, the outermost layer contains a glutaric anhydride unit represented by the above structural formula 10 By dispersing the elastic particles (I-1), which is a multilayer structure polymer having a polymer formed as described above, a good dispersion state is possible without agglomeration, and with improved mechanical properties such as impact resistance, It is considered that extremely high transparency can be expressed.

  The monomer used as the raw material for the unsaturated carboxylic acid alkyl ester unit herein is not particularly limited, but (meth) acrylic acid alkyl ester is preferred, and methyl (meth) acrylate is more preferred. Preferably used.

  Further, the monomer used as a raw material for the unsaturated carboxylic acid unit is not particularly limited, but (meth) acrylic acid is preferable, and methacrylic acid is more preferably used.

  As a preferable example of the elastic particles (I-1) which is the multilayer structure polymer of the present invention, the core layer is represented by butyl acrylate / styrene polymer, and the outermost layer is represented by methyl methacrylate / the above structural formula (d). Copolymer consisting of glutaric anhydride units, or methyl methacrylate / glutaric anhydride units represented by the structural formula (d) / methacrylic acid polymer, and the core layer is dimethylsiloxane / acrylic acid A butyl polymer with an outermost layer of methyl methacrylate polymer, a core layer with a butanediene / styrene polymer and an outermost layer with a methyl methacrylate polymer, and a core layer with a butyl acrylate polymer and an outermost layer Examples include methyl methacrylate polymer ("/" indicates copolymerization). Furthermore, a preferable example is one in which either one or both of the rubber elastic body layer and the outermost layer is a polymer containing a glycidyl methacrylate unit. Among them, the core layer is butyl acrylate / styrene polymer, and the outermost layer is methyl methacrylate / a copolymer of glutaric anhydride units represented by the above structural formula (d), or methyl methacrylate / the above structural formula. In the polymer composition, the glutaric anhydride unit represented by (d) / methacrylic acid polymer approximates the refractive index with the acrylic polymer (A) that is the continuous phase (matrix phase), and It is possible to obtain a good dispersion state with the above, and the transparency that can satisfy the demand for more advanced in recent years is expressed.

  The particle diameter of the elastic particles (I-1) which is a multilayer structure polymer preferably used in the present invention is not particularly limited, but is preferably 10 nm or more and 1000 μm or less, and more preferably 20 nm or more. 100 μm or less, more preferably 50 nm or more and 400 nm or less.

  In the elastic particles (I-1) which is a multilayer structure polymer preferably used in the present invention, the mass ratio of the core and the shell is not particularly limited, but the entire multilayer structure polymer is 100 parts by mass. Sometimes, the core layer is preferably 50 parts by mass or more and 90 parts by mass or less, and more preferably 60 parts by mass or more and 80 parts by mass or less.

As the multilayer structure polymer preferably used in the present invention, a commercially available product that satisfies the above-described conditions may be used.
Examples of commercially available products of such a multilayer structure polymer include, for example, “Metablene” (registered trademark) manufactured by Mitsubishi Rayon Co., Ltd., “Kaneace” (registered trademark) manufactured by Kaneka Chemical Industry Co., Ltd., and “Paraloid” manufactured by Kureha Chemical Industry Co., Ltd. "(Registered trademark)", "Acryloid" (registered trademark) manufactured by Rohm and Haas, "Staffyroid" (registered trademark) manufactured by Gantz Kasei Kogyo Co., Ltd., and "Parapet (registered trademark) SA" manufactured by Kuraray May be used alone or in combination of two or more.

  In addition, specific examples of the elastic particles (ii-2), which is a graft copolymer suitably used as the elastic particles (ii) preferably used in the present invention, include a rubbery polymer, Monomer mixture comprising a saturated carboxylic acid ester monomer, an unsaturated carboxylic acid monomer, an aromatic vinyl monomer, and, if necessary, other vinyl monomers copolymerizable therewith And a graft copolymer obtained by copolymerizing.

  There is no particular limitation on the rubbery polymer used for the elastic particles (I-2) which is a graft copolymer, but diene rubber, acrylic rubber, ethylene rubber and the like can be used. Specific examples include polybutadiene, styrene-butadiene copolymer, block copolymer of styrene-butadiene, acrylonitrile-butadiene copolymer, butyl acrylate-butadiene copolymer, polyisoprene, butadiene-methyl methacrylate copolymer. , Butyl acrylate-methyl methacrylate copolymer, butadiene-ethyl acrylate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-isoprene copolymer, and ethylene-acrylic acid Examples thereof include a methyl copolymer. These rubbery polymers can be used alone or in a mixture of two or more.

  Although there is no restriction | limiting in particular in the mass mean particle diameter of the rubber-like polymer which comprises the elastic body particle | grains (ii-2) which are the graft copolymers in this invention, 0.01-0.5 micrometer, Especially 0.05- A range of 0.4 μm is preferred. If it is less than the above range, the impact strength of the resulting thermoplastic composition tends to decrease, and if it exceeds the above range, transparency may decrease. The mass average particle size of the rubbery polymer depends on the sodium alginate method described in “Rubber Age, Vol. 88, p. 484-490 (1960), by E. Schmidt, PHBiddison”, that is, the concentration of sodium alginate. It can measure by the method of calculating | requiring the particle diameter of 50% of cumulative mass fraction from the mass ratio of creamed and the cumulative mass fraction of sodium alginate density | concentration using the polybutadiene particle diameter to cream.

  The elastic particles (I-2) which is a graft copolymer in the present invention is 10 to 80 parts by weight, preferably 20 to 70 parts by weight, more preferably 100 parts by weight of the rubbery polymer when the particles are taken as 100 parts by weight. Is obtained by copolymerizing 20 to 90 parts by weight, preferably 30 to 80 parts by weight, more preferably 40 to 70 parts by weight of the above-mentioned monomer (mixture) in the presence of 30 to 60 parts by weight. When the ratio of the rubbery polymer is less than the above range or exceeds the above range, the impact strength and the surface appearance may be lowered.

  The elastic particles (I-2), which is a graft copolymer, may contain an ungrafted copolymer that is produced when a monomer mixture is graft copolymerized with a rubbery polymer. However, from the viewpoint of impact strength, the graft ratio is preferably 10 to 100%. Here, the graft ratio is a mass ratio of the grafted monomer mixture to the rubbery polymer. In addition, the intrinsic viscosity measured at 30 ° C. of the methylethylketone solvent of the ungrafted copolymer is not particularly limited, but 0.1 to 0.6 dl / g is a balance between impact strength and moldability. From the viewpoint of, it is preferably used.

  The intrinsic viscosity measured at 30 ° C. of the methyl ethyl ketone solvent of the elastic particles (ii-2) which is the graft copolymer in the present invention is not particularly limited, but is 0.2 to 1.0 dl / g, It is preferably used from the viewpoint of the balance between impact strength and moldability, and more preferably 0.3 to 0.7 dl / g.

  There is no restriction | limiting in particular in the manufacturing method of the elastic body particle | grains (ii-2) which is a graft copolymer in this invention, It can obtain by polymerization methods, such as block polymerization, solution polymerization, suspension polymerization, and emulsion polymerization.

  Moreover, since the transparency of the acrylic film of this invention can be obtained when each refractive index of an acrylic polymer (A) and an elastic body particle (I) is approximate, it is preferable. Specifically, the difference in refractive index between the elastic particles (ii) and the acrylic polymer (ii) is preferably 0.05 or less, more preferably 0.02 or less, especially 0.01 or less. preferable. In order to satisfy such a refractive index condition, a method of adjusting the monomer unit composition ratio of the acrylic polymer (A) and / or a rubbery polymer or single polymer used for the elastic particles (I). The refractive index difference can be reduced by a method for adjusting the composition ratio of the monomer, and an acrylic film having excellent transparency can be obtained.

  The refractive index difference referred to here is a solution in which the acrylic film of the present invention is sufficiently dissolved in a solvent in which the acrylic polymer (A) is soluble under appropriate conditions to obtain a cloudy solution, which is subjected to an operation such as centrifugation. By separating the solvent-soluble part and the insoluble part, the soluble part (acrylic polymer (A)) and the insoluble part (elastic particle (I)) were purified, respectively, and the measured refractive index (23 ° C., Difference in measurement wavelength: 550 nm).

  The average particle diameter of the acrylic elastic particles (i) is preferably 10 to 1000 nm, and more preferably 100 to 200 nm. By setting the thickness to 10 nm or more, the effect of improving toughness can be obtained, and by setting the thickness to 1000 nm or less, a decrease in heat resistance can be suppressed.

  The content of the elastic particles (ii) with respect to the acrylic film is preferably 0.1 to 50 parts by weight, more preferably 5 wt% to 20 wt%. By setting the content of the elastic particles in the above range, it is possible to obtain an acrylic film having particularly excellent workability such as folding resistance and heat resistance.

  In addition, the copolymer composition of the acrylic polymer (A) and the elastic particles (I) in the substantial acrylic film is obtained by separating each component individually by separating the soluble component and the insoluble component using the above solvent. It can be analyzed.

  Further, the acrylic film of the present invention is not limited to the purpose of the present invention, and other thermoplastic resins (for example, polyethylene, polypropylene, acrylic resin, polyamide, polyphenylene sulfide resin, polyether ether ketone resin, polyester, polysulfone, Polyphenylene oxide, polyacetal, polyimide, polyetherimide, etc.), thermosetting resins (for example, phenol resin, melamine resin, polyester resin, silicone resin, epoxy resin, etc.) can be further added, and hindered Phenol, benzotriazole, benzophenone, benzoate, and cyanoacrylate UV absorbers and antioxidants, higher fatty acids, acid esters, and acid amides, and higher alcohols Lubricants and plasticizers such as, montanic acid and its salts, esters thereof, half esters thereof, release agents such as stearyl alcohol, stearamide and ethylene wax, anti-coloring agents such as phosphites and hypophosphites, halogens Optional additives such as phosphoric flame retardants, phosphorous and silicone non-halogen flame retardants, nucleating agents, amine-based, sulfonic acid-based, polyether-based antistatic agents, pigments and other colorants Also good. However, in light of the characteristics required by the application to be applied, it is necessary to add the additive within a range in which the color of the additive does not adversely affect the thermoplastic polymer and the transparency is not lowered.

  In the present invention, the method of blending the acrylic polymer (A) with optional components such as elastic particles (I) or other additives is not particularly limited, and the acrylic polymer (A) and other optional components are previously added. After blending, a method of uniformly melt-kneading with a single-screw or twin-screw extruder usually at 200 to 350 ° C. is preferably used. Moreover, when mix | blending an elastic body particle | grain (ii), the method of removing a solvent after mixing in the solution of the solvent which melt | dissolves both (a) and (ii) component can be used.

  Since the film for a display device of the present invention is excellent in transparency, for example, various covers, various terminal boards, printed wiring boards, speakers, microscopes, binoculars, cameras, optical instruments represented by watches, and video equipment-related Parts such as cameras, VTRs, projection TVs, etc., filters, prisms, Fresnel lenses, etc. Optical recording / optical communication related parts such as various optical discs (VD, CD, DVD, MD, LD, etc.), substrate protective films, optical switches, light Information equipment-related parts such as connectors such as liquid crystal displays, flat panel displays, plasma display light guide plates, Fresnel lenses, polarizing plates, polarizer protective films, retardation films, light diffusion films, viewing angle widening films, reflection films, reflections Prevention film, antiglare film, brightness enhancement film , Conductive films for touch panels, covers, etc., can be used, because particularly excellent in optical isotropy, and the substrate film is extremely useful as a polarizer-protective film.

Hereinafter, the configuration and effects of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.
[Measurement method of physical properties]
Prior to describing each example, the measurement method employed in the example is described.

1. Thickness variation The thickness variation was measured using an Anritsu Co., Ltd. film thickness tester “KG601A” and an electronic micrometer “K306C”. Measurement was performed at a film conveyance speed of 0.3 m / min and a sampling interval of 0.1 second, and thickness data was sampled every 0.25 mm over a 300 mm interval. When the difference between the minimum value and the maximum value of the thickness in an arbitrary 5 mm section is defined as the thickness variation ΔD (μm), the maximum ΔD (μm) in the measured 300 mm section is defined as ΔDmax.

2. Thickness direction retardation Rth
The thickness direction retardation Rth is determined by using an automatic clothing refractometer (KOBRA-21ADH) manufactured by Oji Scientific Co., Ltd., and the refractive index in the direction of the perpendicular axis in the resin film surface at a wavelength of 590 nm, nx, ny (where nx ≧ ny) ), The refractive index nz in the thickness direction of the resin film with respect to light having a wavelength of 590 nm was measured, and the thickness was determined from the following formula when the thickness d (nm) of the resin film was obtained. The measurement was performed once.
Thickness direction retardation Rth = d × {(nx + ny) / 2−nz}.

3. Glass transition temperature (Tg)
Using a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer), the measurement was performed at a temperature increase rate of 20 ° C./min in a nitrogen atmosphere. The sample amount was 5 mg.
The glass transition temperature here was measured at a rate of temperature increase of 20 ° C./min using a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer) and determined according to JIS K7121 (1987). The midpoint glass transition temperature (T _mg ).

4). Solution viscosity Measured using an RB type R80U viscometer manufactured by Toki Sangyo Co., Ltd. It is a value measured using a ST rotor with a measurement temperature of 25 ° C., a rotation speed of 100 rpm.

5. Refractive index, refractive index difference Acetone is added to polymer (A) and refluxed for 4 hours, and this solution is centrifuged at 9,000 rpm for 30 minutes to dissolve acetone soluble component (component (A)) and insoluble component ((I)). Component). These were dried under reduced pressure at 60 ° C. for 5 hours. Each of the obtained solids was press-molded at 250 ° C. to form a film having a thickness of 0.1 mm, and then the refractive index at 23 ° C. and 550 nm wavelength was measured with an Abbe refractometer (manufactured by Atago Co., Ltd., DR-M2). It was measured. In addition, the absolute value was used about the refractive index difference of (A) component and (I) component.

6). Mass average molecular weight (absolute molecular weight)
Gel permeation chromatograph (pump: model 515, manufactured by Waters, column: TSK-gel-GMHXL, Tosoh Corporation) equipped with a DAWN-DSP type multi-angle light scattering photometer (manufactured by Wyatt Technology) using dimethylformamide as a solvent. ).

7). Average particle diameter The film is made into ultra-thin sections of about 100 to 800 nm in the thickness direction, stained with ruthenic acid, and then transferred at a magnification of 100,000 times using a transmission electron microscope (JEM-1200EX manufactured by JEOL). However, the equivalent circle diameter was determined for 100 particles, and the average value was defined as the average particle diameter. For core-shell type and graft copolymer type elastic particles (ii), the particle size of the rubbery polymer portion was measured.

8). Residual solvent The film immediately after film formation was sampled in a 20 cm square, and the film weight w ₂ was weighed. Next, after heat-treating this film for 10 minutes in a hot air oven at a temperature of 200 ° C., the film weight w ₃ was weighed and the residual solvent in the film was determined from the following formula. In addition, the measurement was performed twice and the average value was calculated | required.
· Residual solvent _{(%) = (w 2 -w} 3) / w 3 × 100.

9. Fluctuation evaluation Light is irradiated using a projector from a position 1 m from the front of the white screen. The shadow projected on the white screen when a film inclined by 45 ° with respect to the screen surface was placed at a position 15 cm from the screen on the straight line was visually evaluated.
A ... Striped pattern is not observed in the projected image.
B: A slight stripe pattern is observed in the projected image, but the contrast is very weak.
C: A striped pattern is clearly observed in the projected image.
D: The stripe pattern of the projected image looks very prominent, and a clear period is observed.

(1) Preparation of acrylic polymer Acrylic polymer (A-1)
First, a methyl methacrylate / acrylamide copolymer suspension was prepared as follows.
20 parts by weight of methyl methacrylate,
80 parts by mass of acrylamide,
0.3 parts by mass of potassium persulfate,
1500 parts by mass of ion-exchanged water was charged into the reactor, and while the reactor was replaced with nitrogen gas, the reaction was allowed to proceed at 70 ° C. until the monomer was completely converted to a polymer. The obtained aqueous solution was used as a suspending agent. A solution in which 0.05 part by mass of the above suspending agent is dissolved in 165 parts by mass of ion-exchanged water is supplied to a stainless steel autoclave having a capacity of 5 liters and equipped with a baffle and a foudra-type stirring blade, and the system is filled with nitrogen gas. It stirred at 400 rpm, replacing.

Next, a mixed substance having the following charge composition was added while stirring the reaction system.
Methacrylic acid: 27 parts by mass Methyl methacrylate: 73 parts by mass t-dodecyl mercaptan: 1.2 parts by mass 2,2′-azobisisobutyronitrile: 0.4 parts by mass The time at which the internal temperature reached 70 ° C. was set as the polymerization start time, and the polymerization was continued for 180 minutes.

Thereafter, the reaction system was cooled, the polymer was separated, washed and dried in accordance with a normal method to obtain a bead-shaped copolymer. The polymerization rate of this copolymer was 97%, and the mass average molecular weight was 130,000. Add 0.2% by mass of additive (NaOCH ₃ ) to the above copolymer and use 10L of nitrogen from the hopper using a twin screw extruder (TEX30 (manufactured by Nippon Steel), L / D = 44.5). An intramolecular cyclization reaction was carried out at a screw rotation speed of 100 rpm, a raw material supply rate of 5 kg / h, and a cylinder temperature of 290 ° C. while purging at an amount of / min. To obtain a pellet-like acrylic polymer (A-1). The molecular weight of the polymer (A-1) was 130,000, and Tg was 140 ° C.

(2) Preparation of elastic particles Elastic particle (I-1) which is a multilayer structure polymer
In a glass container with a cooler (capacity 5 liters), as an initial adjustment solution,
120 parts by weight of deionized water,
0.5 parts by weight of potassium carbonate,
0.5 parts by weight of dioctyl sulfosuccinate,
After charging 0.005 parts by mass of potassium persulfate and stirring under a nitrogen atmosphere,
53 parts by weight of butyl acrylate,
17 parts by mass of styrene,
1 part by weight of allyl methacrylate (crosslinking agent) was charged. These mixtures were reacted at 70 ° C. for 30 minutes to obtain a rubbery polymer.
Next, 21 parts by mass of methyl methacrylate,
9 parts by weight of methacrylic acid,
A mixture of 0.005 parts by mass of potassium persulfate was continuously added over 90 minutes at 70 ° C. and held for another 90 minutes to polymerize the shell layer.

  The polymer latex was coagulated with sulfuric acid, neutralized with caustic soda, washed, filtered, and dried to obtain elastic particles (I-1) as a multilayer structure polymer. The average particle diameter of the rubber polymer part of the elastic particles measured with an electron microscope was 140 nm.

(3) Blending of acrylic polymer (A) and elastic particles (I) 80 parts by mass of acrylic polymer (A) and 20 parts by mass of elastic particles (I) are mixed into a twin-screw extruder (Nippon Steel). TEX30, L / D = 44.5) was used and kneaded at a screw rotation speed of 150 rpm and a cylinder temperature of 280 ° C. to obtain a pellet-shaped acrylic polymer composition (U). The Tg of the polymer was 137 ° C.

Example 1
The acrylic polymer composition (U) was vacuum dried at 80 ° C. for 8 hours, then dissolved in acetone to a solid content concentration of 33% by mass, filtered using a 1.2 μm cut filter, and then filtered with a hopper. The polymer solution was obtained by leaving the solution for a period of time to remove bubbles in the solution. The viscosity of this polymer solution at 25 ° C. was 8 Pa · s. The polymer solution was cast at 22 ° C. on a PET film subjected to a release treatment through a T die having a lip gap of 0.2 mm and a width of 1360 mm using a gear pump. Thereafter, drying at 60 ° C., 70 ° C., 90 ° C., 100 ° C., and 120 ° C. is performed stepwise for 1 minute each, followed by heat treatment at 130 ° C. for 3 minutes, heat treatment at 170 ° C. for 10 minutes, and an acrylic system having a thickness of 30 μm. A film was obtained. The thickness variation was as small as 0.2 μm, and Rth was as small as 1 nm.
The properties of the obtained film are shown in Table 1.

(Example 2)
The acrylic polymer composition (U) was vacuum dried at 80 ° C. for 8 hours, then dissolved in 2-butanone to a solid content concentration of 28% by mass, filtered using a 1.2 μm cut filter, and put into a hopper. For 24 hours to remove bubbles in the solution to obtain a polymer solution. The viscosity of this polymer solution at 25 ° C. was 7 Pa · s. The polymer solution was cast at 22 ° C. on a PET film subjected to a release treatment through a T die having a lip gap of 0.2 mm and a width of 1360 mm using a gear pump. Thereafter, drying at 60 ° C., 70 ° C., 90 ° C., 100 ° C., and 120 ° C. is performed stepwise for 1 minute each, followed by heat treatment at 130 ° C. for 3 minutes, heat treatment at 170 ° C. for 10 minutes, and an acrylic system having a thickness of 30 μm. A film was obtained. Since the boiling point of the solvent was slightly higher than that in Example 1, the thickness fluctuation was slightly increased, and the fluctuation evaluation was B.
The properties of the obtained film are shown in Table 1.

(Example 3)
The acrylic polymer (A) was vacuum dried at 80 ° C. for 8 hours, dissolved in acetone to a solid content concentration of 33% by mass, filtered using a 1.2 μm cut filter, and allowed to stand still for 24 hours in a hopper. The polymer solution was obtained by removing the bubbles in the solution. The viscosity of this polymer solution at 25 ° C. was 8 Pa · s. The polymer solution was cast at 22 ° C. on a PET film subjected to a release treatment through a T die having a lip gap of 0.2 mm and a width of 1360 mm using a gear pump. Thereafter, drying at 40 ° C., 60 ° C., 80 ° C., 100 ° C., and 120 ° C. is performed stepwise for 1 minute each, followed by heat treatment at 130 ° C. for 3 minutes, heat treatment at 170 ° C. for 10 minutes, and a 30 μm thick acrylic system A film was obtained. The thickness variation was as small as 0.2 μm, and Rth was as small as 1 nm.
The properties of the obtained film are shown in Table 1.

(Comparative Example 1)
After the acrylic polymer composition (U) was vacuum dried at 80 ° C. for 8 hours, it was dissolved in 2-butanone so as to have a solid content concentration of 25% by mass and filtered using a 1.2 μm cut filter. For 24 hours to remove bubbles in the solution to obtain a polymer solution. The viscosity of this polymer solution at 25 ° C. was 4 Pa · s. The polymer solution was cast at 22 ° C. on a PET film subjected to a release treatment through a T die having a lip gap of 0.2 mm and a width of 1360 mm using a gear pump. Thereafter, drying at 60 ° C., 70 ° C., 80 ° C., 100 ° C., and 120 ° C. is performed stepwise for 1 minute each, followed by heat treatment at 130 ° C. for 3 minutes, heat treatment at 170 ° C. for 10 minutes, and an acrylic system having a thickness of 30 μm. A film was obtained. Since the obtained film had a low viscosity of the polymer solution, the thickness variation was as large as 0.6 μm, and the fluctuation evaluation was poor.
The properties of the obtained film are shown in Table 1.

(Comparative Example 2)
The acrylic polymer composition (U) was vacuum dried at 80 ° C. for 8 hours, dissolved in dichloromethane to a solid content concentration of 15% by mass, filtered using a 1.2 μm cut filter, and then filtered with a hopper. The solution was left standing for a while to remove bubbles in the solution to obtain a polymer solution. The viscosity of this polymer solution at 25 ° C. was 1 Pa · s. This polymer solution was cast on a PET film subjected to a release treatment through a T die having a lip gap of 0.6 mm and a width of 1360 mm at 22 ° C. using a gear pump. Thereafter, drying at 40 ° C., 60 ° C., 80 ° C., 100 ° C., and 120 ° C. is performed stepwise for 1 minute each, followed by heat treatment at 130 ° C. for 3 minutes and heat treatment at 170 ° C. for 10 minutes, and an acrylic system having a thickness of 40 μm A film was obtained. Since the obtained film had a low viscosity of the polymer solution, the fluctuation in thickness was as large as 0.8 μm, and the evaluation of fluctuation was poor. In addition, when the solvent dichloromethane evaporated, condensation occurred and the film whitened.
The properties of the obtained film are shown in Table 1.

(Comparative Example 3)
The acrylic polymer composition (U) was vacuum-dried at 80 ° C. for 8 hours, dissolved in dichloromethane to a solid content concentration of 45% by mass, filtered using a 1.2 μm cut filter, and then filtered with a hopper. The polymer solution was obtained by leaving the solution for a period of time to remove bubbles in the solution. The viscosity of this polymer solution at 25 ° C. was 620 Pa · s. This polymer solution was cast at 22 ° C. on a PET film subjected to a release treatment through a T die having a lip gap of 0.1 mm and a width of 1360 mm using a gear pump. Since the viscosity of the solution was high, extrusion from the die could not be performed and film formation was impossible.
The properties of the obtained film are shown in Table 1.

(Comparative Example 4)
Using TAC “LT-35” manufactured by Daicel Corporation, dissolved in a solvent mixed with 80 parts by weight of dichloromethane and 20 parts by weight of methanol, and dissolved using a 1.2 μm cut filter with a solid content of 10% by mass. And left in a hopper for 24 hours to remove bubbles in the solution to obtain a polymer solution. The viscosity of this polymer solution at 25 ° C. was 5 Pa · s. This polymer solution was cast on a PET film at 22 ° C. through a T die having a lip gap of 0.6 mm and a width of 1360 mm using a gear pump. Thereafter, drying at 30 ° C., 40 ° C., and 60 ° C. was performed stepwise for 1 minute each, followed by heat treatment at 80 ° C. for 3 minutes and heat treatment at 120 ° C. for 10 minutes to obtain a cellulose film having a thickness of 40 μm. Since the obtained film had a low viscosity of the polymer solution, the fluctuation in thickness was as large as 0.6 μm, and the evaluation of fluctuation was poor. Further, since the polymer has a retardation in the thickness direction, the film has a large Rth of 45.6 nm.
The properties of the obtained film are shown in Table 1.

  The films for display devices of Examples 1 to 4 were films having a thickness variation of 0.5 μm or less, little fluctuation, and a low Rth optical quality. The films of Comparative Examples 1, 2, and 4 had a thickness variation larger than 0.5 μm and a large fluctuation, and the film of Comparative Example 4 was a film inferior in optical quality with a high Rth.

Claims (13)

  A film formed by a solution casting method, and when the thickness data is sampled every 0.25 mm over a 300 mm section, the thickness variation in an arbitrary 5 mm section is 0.5 μm or less, and A film for a display device having a thickness direction retardation Rth of 10 nm or less.   The film for a display device according to claim 1, wherein the display device film has a thickness of 15 μm or more and 100 μm or less and a glass transition temperature of 120 ° C. or more.   The film for a display device according to claim 1 or 2, wherein the film for a display device is composed of an acrylic polymer. The acrylic polymer constituting the display device film is made of an acrylic polymer (a) containing at least one of structural units represented by the following structural formulas (a) to (c) 3. 3. The film for a display device according to 3.

(In the above formulas, R ¹ and R ² represent the same or different hydrogen atoms, an alkyl group having 1 to 5 carbon atoms, a carboxyl group, or a carboxyalkyl group having 2 to 5 carbon atoms. , X ¹ and X ² represent the same or different CH ₂ or C═O, X ³ represents O or NR ³ , R ³ represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a carboxyl group Represents a group or a carboxyalkyl group having 2 to 5 carbon atoms.)

(In the above formula, R ⁴ represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a carboxyl group, or a carboxyalkyl group having 2 to 5 carbon atoms.)

(In the above formula, R ⁵ represents a substituent containing an alicyclic structure having 6 to 15 carbon atoms.) The film for a display device according to claim 3 or 4, wherein the acrylic polymer comprises an acrylic polymer (A) containing a glutaric anhydride unit represented by the following structural formula (d).

(In said formula, R < ⁶ >, R < ⁷ > represents the same or different hydrogen atom or a C1-C5 alkyl group.)   The acrylic polymer (A) comprises 50 to 90 parts by mass of an unsaturated carboxylic acid alkyl ester unit and 10 to 50 parts by mass of a glutaric anhydride unit when the acrylic polymer (A) is 100 parts by mass. 4. The film for a display device according to 4 or 5.   The acrylic polymer (A) contains 5 to 50 parts by mass of acrylic elastic particles (I) having a particle diameter of 10 nm to 1000 nm with respect to 100 parts by mass of the acrylic polymer (A). The film for display apparatuses in any one of -6.   The acrylic elastic particle (i) is a multilayer structure polymer composed of a layer containing one or more rubber polymers and one or more layers composed of a polymer other than the rubber polymer. Item 8. The film for display device according to Item 7.   The film for a display device according to claim 7 or 8, wherein a difference in refractive index between the acrylic elastic particles (I) and the acrylic polymer (A) is 0.05 or less.   In a method of forming a film by a solution casting method using a polymer solution (C) prepared by dissolving a polymer (A) in a solvent (B), the polymer (A) is an acrylic polymer, and the polymer The solution viscosity at 25 ° C. of the solution (C) is 7 Pa · s or more and 600 Pa · s or less, and the boiling point of the solvent component of 50% by weight or more in the solvent (B) is 30 ° C. or more and 80 ° C. or less. A method for forming a film for a display device, which is characterized.   The method for producing a film for a display device according to claim 10, wherein 80% by weight or more and 100% by weight or less in the solvent (B) is acetone and / or 2-butanone.   The film for liquid crystal display devices using the film for display devices in any one of Claims 1-8, or the film for display devices obtained by the manufacturing method of Claim 10 or 11. The protective film for polarizers using the film for display apparatuses in any one of Claims 1-8, or the film for display apparatuses obtained by the manufacturing method of Claim 10 or 11.