JP2013072010A - Polycarbonate resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polycarbonate resin film having excellent light diffusivity.SOLUTION: The polycarbonate resin film consists of a polycarbonate resin, with at least one side thereof being matted, which is characterized by being 9-15 in height distribution index on the matted surface. It is preferable that the resin film is obtained by melt extrusion of the corresponding polycarbonate resin, and the matted surface is formed by matting roll transfer.

Description

  The present invention relates to a polycarbonate resin film.

Optical films such as a light guide film, a retardation film, a light diffusion film, and a protective film for a polarization separation sheet are required to have excellent transparency and heat resistance. A film made of a polycarbonate resin is used as an optical film because it is excellent in transparency and further excellent in heat resistance, impact resistance and rigidity.

The light guide film is often used as a thin-walled light guide film for backlights of small liquid crystal display devices, keyboards for personal computers, and operation buttons for mobile phones, and has a high transparency. Desired.
The retardation film is used in a liquid crystal display device, and is produced, for example, by stretching a polycarbonate resin film obtained by a solution casting method (so-called solvent casting method), and is required to have a desired retardation.
The light diffusing film is used in a liquid crystal display device, and is manufactured by, for example, adding a light diffusing agent to a thermoplastic resin film or shaping a pattern on a thermoplastic resin film. Transparency is required.
The protective film of the polarization separation sheet is used by being bonded to at least one surface of the polarization separation sheet in order to protect the polarization separation sheet, but the polarization direction of the polarized light emitted from the polarization separation sheet is changed. In order to reduce the optical distortion, it is required to reduce the optical distortion, and in order to improve the viewing angle, light diffusibility is required.

Patent Document 1 discloses a polycarbonate-based resin film used as a light diffusing film, in which one surface has an arithmetic average roughness (Ra) of 0.5 to 3 and a height distribution index (HDI) of 3. A polycarbonate resin film of ~ 8 is described.

International Publication No. 2009/028769

  However, the polycarbonate-based resin film described in Patent Document 1 has insufficient light diffusibility, gloss is confirmed on the film surface, and when the liquid crystal display device in which the film is used is viewed from an oblique direction. The display image of the liquid crystal display device looks dark.

  Then, the subject of this invention is providing the polycarbonate-type resin film which has the outstanding light diffusibility.

  As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.

That is, the present invention relates to the following inventions.
(1) A polycarbonate resin film comprising a polycarbonate resin, at least one surface of which is a mat surface, and having a height distribution index of 9 to 15 on the mat surface.
(2) The polycarbonate resin film according to (1), which has a thickness of 30 to 300 μm and a total light transmittance of 85% or more.
(3) The polycarbonate-type resin film as described in said (1) or (2) whose haze is 50% or more.
(4) The polycarbonate resin film according to any one of (1) to (3), wherein the surface glossiness is 50% or less.
(5) The polycarbonate resin film according to any one of (1) to (4), wherein the retardation of incident light having a wavelength of 590 nm is 30 nm or less.
(6) The polycarbonate resin film according to any one of (1) to (5), which is formed by melt extrusion of a polycarbonate resin.
(7) The polycarbonate resin film according to any one of (1) to (6), which is used in a liquid crystal display device.
(8) The polycarbonate resin film according to (7), which is used for protecting a polarization separation sheet in the liquid crystal display device.

  According to the present invention, a polycarbonate resin film having excellent light diffusibility can be provided.

It is a schematic explanatory drawing which shows an example of the height distribution curve of the surface shape of a polycarbonate-type resin film. It is a schematic explanatory drawing which shows an example of the manufacturing process of a polycarbonate-type resin film. It is a schematic explanatory drawing which shows an example which used the polycarbonate-type resin film as a polarization separation sheet protective film in a liquid crystal display device.

  Hereinafter, the present invention will be described in detail. The polycarbonate resin film of the present invention is made of a polycarbonate resin.

<Polycarbonate resin>
As the polycarbonate resin, for example, an aromatic polycarbonate resin excellent in heat resistance, mechanical strength, transparency and the like is preferably used. The aromatic polycarbonate resin is usually obtained by reacting a dihydric phenol and a carbonate precursor by an interfacial polycondensation method or a melt transesterification method, or by polymerizing a carbonate prepolymer by a solid phase transesterification method. Or obtained by polymerizing a cyclic carbonate compound by a ring-opening polymerization method.

  Examples of the dihydric phenol include hydroquinone, resorcinol, 4,4′-dihydroxydiphenyl, bis (4-hydroxyphenyl) methane, bis {(4-hydroxy-3,5-dimethyl) phenyl} methane, 1,1 -Bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A), 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis {(4-hydroxy-3,5-dimethyl) phenyl} propane, 2,2-bis {(4-hydroxy-3,5- Dibromo) phenyl} propane, 2,2-bis {(3-isopropyl-4-hydroxy) phenyl} propane, 2,2-bis { 4-hydroxy-3-phenyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) -3-methylbutane, 2,2-bis (4-hydroxy) Phenyl) -3,3-dimethylbutane, 2,4-bis (4-hydroxyphenyl) -2-methylbutane, 2,2-bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, 1,1-bis (4-hydroxyphenyl) -3, 3,5-trimethylcyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis {(4-hydro Cis-3-methyl) phenyl} fluorene, α, α′-bis (4-hydroxyphenyl) -o-diisopropylbenzene, α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene, α, α ′ -Bis (4-hydroxyphenyl) -p-diisopropylbenzene, 1,3-bis (4-hydroxyphenyl) -5,7-dimethyladamantane, 4,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfoxide 4,4′-dihydroxydiphenyl sulfide, 4,4′-dihydroxydiphenyl ketone, 4,4′-dihydroxydiphenyl ether, and 4,4′-dihydroxydiphenyl ester. These may be used alone or in combination of two or more. Can be used.

  Among them, bisphenol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl)- 3-methylbutane, 2,2-bis (4-hydroxyphenyl) -3,3-dimethylbutane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4-hydroxyphenyl) ) -3,3,5-trimethylcyclohexane and α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene are preferably used alone or in combination of two or more. Bisphenol A alone, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, At least one selected from the group consisting of enol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, and α, α'-bis (4-hydroxyphenyl) -m-diisopropylbenzene. The combined use with a monohydric phenol is preferred.

  Examples of the carbonate precursor include carbonyl halide, carbonate ester, haloformate, and the like, and specific examples include phosgene, diphenyl carbonate, dihaloformate of dihydric phenol, and the like.

Polycarbonate resin in the present invention, 300 ° C., a melt volume flow rate at 1.2kg load (MVR) is 11~35cm ³ / 10min, preferably 12~30cm ³ / 10min, more preferably 12 to it is a 25cm ³ / 10min. If the MVR of the polycarbonate resin is out of the predetermined range, irregularities may occur on the surface of the film made of the polycarbonate resin. As a polycarbonate-type resin whose MVR is in a predetermined range, those obtained by the above polymerization method may be used, or commercially available resins may be used. The MVR is measured according to ISO1133.

  The polycarbonate-based resin preferably has a viscosity average molecular weight of 17000 to 21,500, more preferably 18000 to 21000, and still more preferably 19000 to 21000. When the viscosity average molecular weight of the polycarbonate resin is out of the predetermined range, irregular defects may occur on the surface of the film made of the polycarbonate resin. As a polycarbonate-type resin whose viscosity average molecular weight is a predetermined range, what was obtained by the above-mentioned polymerization method may be used, and a commercially available thing may be used.

Viscosity average molecular weight is 0.5 wt% polycarbonate resin solution using methylene chloride as a solvent, specific viscosity η _sp is measured at 20 ° C. using a Canon Fenske type viscosity tube, and the intrinsic viscosity η is determined by concentration conversion. , Calculated from the following SCHNELL formula (I).
η = 1.23 × 10 ⁻⁴ M ^0.83 (I)

  The polycarbonate resin may contain, for example, a light diffusing agent, an ultraviolet absorber, an organic dye, an inorganic dye, a pigment, an antioxidant, an antistatic agent, or a surfactant, if necessary. Good.

<Polycarbonate resin film>
The polycarbonate-based resin film of the present invention has excellent light diffusibility because at least one surface is a mat surface and the height distribution index (HDI) on the mat surface is within a predetermined range.

  The HDI on the mat surface is 9-15, preferably 9-12, and more preferably 9-10. If the HDI is too small, the light diffusibility of the polycarbonate resin film is not sufficient, the gloss is confirmed on the film surface, and the liquid crystal display device using the polycarbonate resin film is viewed from an oblique direction. The display image of the liquid crystal display device may appear dark. When the HDI is too large, the light diffusibility of the polycarbonate resin film becomes excessive, and gloss is not confirmed on the film surface, but when the liquid crystal display device using the polycarbonate resin film is viewed from the front, The display image of the liquid crystal display device may appear dark. In order to make the HDI of at least one surface of the optical polycarbonate resin film within the predetermined range, in the film forming method using a mat roll described later, for example, the resin extruded from the die is used as the first cooling roll. What is necessary is just to adjust the pressing pressure of the 2nd cooling roll to this resin when pinched | interposed into a 2nd cooling roll, or to adjust the uneven | corrugated shape of the outer peripheral surface of a 2nd cooling roll, and the mat | matte mentioned later In the method of forming the matte surface using the agent, for example, the average particle size and the amount of the matting agent may be adjusted.

  When one surface of the polycarbonate resin film is a mat surface, the HDI on the mat surface may be in the predetermined range. When both surfaces of the film are mat surfaces, the HDI on one mat surface may be within the predetermined range, and the HDI on the other mat surface may be outside the predetermined range. The HDI on the surface may be within the predetermined range.

  The HDI is obtained from the height distribution curve of the surface shape of the polycarbonate resin film. FIG. 1 is a schematic explanatory diagram illustrating an example of a height distribution curve of a surface shape of a polycarbonate resin film. In the figure, the X axis indicates the height of the surface shape of the film, and the Y axis indicates the presence ratio of the surface shape having the height indicated by the X axis. The maximum value on the Y axis of the height distribution curve is 100%, and the value of X when Y is 100% is 0 μm. HDI is defined as the distribution width of X where Y is 20% or more.

  For the HDI, for example, the surface shape of a polycarbonate resin film is measured using a three-dimensional microscope “PLμ2300” (manufactured by Sensofar) to create a height distribution curve of the surface shape, and from the obtained height distribution curve Derived.

  From the viewpoint of light diffusibility, the polycarbonate resin film preferably has a maximum height roughness (Rz) of 8 to 20 μm, more preferably 10 to 15 μm on the mat surface in which the HDI is in the predetermined range. preferable. When the Rz is too small, the light diffusibility of the polycarbonate resin film is not sufficient, and when the liquid crystal display device using the polycarbonate resin film is viewed from an oblique direction, the display image of the liquid crystal display device appears dark. There is a fear. If the Rz is too large, the light diffusibility of the polycarbonate resin film becomes excessive, and when the liquid crystal display device using the polycarbonate resin film is viewed from the front, the display image of the liquid crystal display device appears dark. There is a fear. In order to set the Rz of at least one surface of the optical polycarbonate resin film within the predetermined range, the uneven shape of the outer peripheral surface of the second cooling roll in the melt extrusion forming described later is adjusted, or a matting agent described later is used. In the mat surface forming method, the average particle size and the amount of the matting agent may be adjusted. The Rz is a value obtained by measuring with a surface roughness meter in accordance with JIS B0601-2001.

  The thickness of the polycarbonate resin film is preferably 30 to 300 μm, more preferably 40 to 270 μm, and still more preferably 50 to 250 μm. If the thickness of the polycarbonate resin film is too thin, the rigidity of the film itself is lowered, and wrinkles are likely to occur on the surface of the film. When the polarization separating sheet has insufficient rigidity, it may be liable to cause swell or deflection when it is set in a liquid crystal display device. If the polycarbonate-based resin film is too thick, the production cost of the film becomes high, or when the film is bonded to a polarization separation sheet, the thickness of the polarization separation sheet after bonding becomes thick, resulting in liquid crystal There is a possibility that the thickness of the panel becomes thick.

  The polycarbonate resin film preferably has a total light transmittance of 85% or more measured in accordance with JIS K7361-1. If the total light transmittance of the film is too low, the ratio of the amount of light emitted from the film with respect to the amount of light incident on the film is reduced, which may reduce the light utilization efficiency.

  The haze of the polycarbonate resin film is preferably 50% or more, more preferably 55% or more, and further preferably 60% or more. If the haze is too low, a sufficient light diffusion effect may not appear.

  The 60-degree specular gloss of at least one surface of the polycarbonate resin film is preferably 50% or less, more preferably 45% or less, and even more preferably 35% or less. If the 60-degree specular gloss is too large, for example, when an optical film and a liquid crystal panel come into contact with each other, a rainbow pattern due to an interference draft may occur.

The in-plane retardation value of incident light at a wavelength of 590 nm of the polycarbonate resin film is preferably 30 nm or less, and more preferably 20 nm or less.
For example, when the polycarbonate resin film of the present invention is used in a liquid crystal display device, since the light used for liquid crystal display is polarized light, a film with small optical distortion is required, and the retardation value should be 30 nm or less. preferable. When the polycarbonate resin film of the present invention is used as a polarizing separation sheet protective film used for protecting a polarizing separation sheet among liquid crystal display devices, the polarization direction of polarized light emitted from the polarizing separation sheet for the following reasons The retardation value is preferably low, the retardation value is more preferably 20 nm or less, and further preferably 10 nm or less so as not to disturb as much as possible.
As shown in FIG. 3, the liquid crystal display device has a liquid crystal panel 11 installed on a backlight unit 8, and is configured such that light emitted from the backlight unit 8 enters the liquid crystal panel 11. The polarized light separating sheet 9 is usually disposed between the backlight unit 8 and the liquid crystal panel 11, and converts the non-polarized light emitted from the backlight unit 8 into two polarized lights that are orthogonal to each other. After separating and selectively transmitting only one polarized light and emitting it to the liquid crystal panel 11 side, returning the other polarized light to the backlight unit 8 side and reflecting it in the backlight unit, By making it incident on the polarization separation sheet 9 and reusing it, the light utilization efficiency is improved. Therefore, as the polarization separation sheet protective film 10 used by being laminated or bonded to both or one surface of the sheet 9 for protection of the polarization separation sheet 9, the polarization direction of polarized light emitted from the sheet 9 is used. The retardation value is preferably low, more preferably 20 nm or less, and even more preferably 10 nm or less so as not to disturb as much as possible.
When a polycarbonate resin film is used as the polarizing separation sheet protective film 10, the film is laminated or bonded to the polarizing separation sheet 9 so that the matte surface in which the HDI of the film is in the predetermined range is the outermost surface. Is preferred.

<Manufacturing process of polycarbonate resin film>
The polycarbonate-based resin film of the present invention is made of the above-described polycarbonate-based resin, and at least one surface is a mat surface, and the HDI on the mat surface is in the predetermined range. Examples of the method for producing a polycarbonate resin film include a method of melt-extruding the above-mentioned polycarbonate resin, a method of forming a solution of the resin, and the like. Of these, 300 ° C., according to the method of MVR at 1.2kg load melt-extruding a polycarbonate resin is 11~35cm ³ / 10min, polycarbonate formation of surface defects is suppressed based resin film, sequentially It can be stably produced with good production stability. As a method for forming a polycarbonate-based resin film in which the HDI is in a predetermined range, a transfer method using a so-called mat roll, which is a metal roll having an uneven shape formed on the outer peripheral surface at the time of melt extrusion molding, a matting agent and The method etc. which form an unevenness | corrugation on the surface in melt-extrusion molding using the polycarbonate-type resin which mix | blended the transparent fine particle which becomes will be mentioned. The polycarbonate-based resin film of the present invention only needs to contain the above-described polycarbonate-based resin, for example, other resins may be blended, and, for example, multilayer melt extrusion molding with other resins It may be a multilayer film such as a two-kind two-layer or a two-kind three-layer obtained by the above. In addition, about these other resin, you may mix | blend a transparent fine particle and the above-mentioned other component as needed like a polycarbonate-type resin.

<Method for forming film using mat roll>
A method of forming a film using a mat roll is a method of transferring a concavo-convex shape using a metal roll having a concavo-convex shape formed on the outer peripheral surface at the time of melt extrusion molding (hereinafter sometimes referred to as a mat roll). Examples include the methods described in JP-A-2009-196327 and JP-A-2009-202382.

FIG. 2 is a schematic explanatory view showing an example of a production process of the polycarbonate-based resin film of the present invention (hereinafter sometimes referred to as the production process of the present invention).
As shown in the figure, in this manufacturing process, a melt extruder 1 is prepared, and a polycarbonate resin charged into the extruder is melt-kneaded, passes through a polymer filter 2, and then passes through a die 3 (T die). The resin is spread and extruded from the die tip as a film.

  Examples of the polymer filter 2 include a leaf disc type, a candle type, and a pleat type. Among them, a leaf disc type polymer filter is preferable.

  As the die 3, a T die is usually used. The die 3 is preferably a single-layer die in which one type of resin is extruded as a single layer when the polycarbonate resin film is a single-layer film, and in the case of a multilayer film such as two-type two-layer or two-type three-layer, respectively. A multilayer die in which two or more kinds of resins fed by pressure from an extruder are laminated and co-extruded is preferable, and a feed block die or a multi-manifold die is preferable as the multilayer die.

  Next, the resin extruded from the die 3 is sandwiched between the first cooling roll 4 and the second cooling roll 5 that are arranged to face each other in a substantially horizontal direction, and the mat surface is transferred to at least one surface by transferring the uneven shape. The polycarbonate resin film 7 can be obtained by being slowly cooled by the third cooling roll 6.

  The first cooling roll 4 has a diameter of about 25 to 100 cm and is made of a rubber roll or a metal elastic roll.

  Examples of the rubber roll include a silicone rubber roll and a fluororubber roll, and a mixture of sand in order to improve releasability can also be employed. The hardness of the rubber roll is preferably in the range of A60 ° to A90 ° measured according to JIS K6253. In order to make the hardness of the rubber roll within the above range, for example, it can be arbitrarily performed by adjusting the degree of crosslinking and composition of the rubber constituting the rubber roll.

  The metal elastic roll is one in which the inside of the roll is made of rubber or one in which a fluid is injected, and the outer peripheral part is made of a metal thin film having flexibility. . Specifically, the inside of the roll is composed of a silicone rubber roll, and a cylindrical stainless steel thin film having a thickness of about 0.2 to 1 mm is coated on the outer periphery of the roll, In the case of injecting a fluid such as oil, a cylindrical thin film made of stainless steel having a thickness of about 2 to 5 mm is fixed at the end of the roll and the fluid is sealed inside.

  Thus, as the 1st cooling roll 4, what was comprised by the metal material and the elastic body, and finished in mirror surface shape with the plating etc. may be used. It should be noted that the surface of the metal thin film or rubber roll of the metal elastic roll has no problem even if an uneven shape is provided on the surface in the same manner as the second cooling roll 5 described below.

  The second cooling roll 5 is a mat roll made of a metal roll having a diameter of about 25 to 100 cm and having an uneven shape on the outer peripheral surface. Specific examples include drilled rolls from which metal lumps have been cut out and metal rolls that can control the temperature of the roll surface through fluid, steam, etc. inside a roll such as a spiral roll having a hollow structure. In addition, a material having a desired concavo-convex shape formed by sandblasting, engraving or the like can be used.

  The uneven shape formed on the outer peripheral surface of the second cooling roll 5 is not particularly limited as long as the HDI on the surface in contact with the second cooling roll of the obtained polycarbonate-based resin film is 9 to 15. A mat shape or an uneven shape having a specific pitch or height may be used, and a mat shape is preferable.

  The uneven transfer onto the polycarbonate resin film surface is because the resin pushed out of the die is sandwiched between the first cooling roll and the die 2 cooling roll, and the resin is pressed against the second cooling roll. Done. When the pressing pressure of the second cooling roll to the resin is low, the uneven shape on the surface of the second cooling roll becomes difficult to be transferred to the resin, and the resulting polycarbonate-based resin film on the mat surface where the uneven shape is formed. HDI tends to be smaller.

  In order to use both surfaces of the polycarbonate resin film as a mat surface, for example, the rubber roll is used as the first cooling roll 4, and the mat roll having the uneven shape formed on the outer peripheral surface is used as the second cooling roll 5. In the polycarbonate resin film to be obtained, the surface in contact with the mat roll is a mat surface in which the HDI is in the predetermined range. In addition, the resin extruded from the die 3 may be sandwiched between cooling rolls formed with the uneven shape on the outer peripheral surface.

  The polycarbonate-based resin film to which the concavo-convex shape has been transferred is wound around the second cooling roll 5 and then taken up by the take-up roll. At this time, the third cooling roll 6 may be provided after the second cooling roll 5. As a result, the polycarbonate-based resin film is slowly cooled, so that the optical distortion of the film can be reduced and the contact time with the second cooling roll 5 can be secured stably. It is possible to stably transfer the uneven shape imparted to the. The third cooling roll 6 is not particularly limited, and an ordinary metal roll conventionally used in extrusion molding can be employed. Specific examples include a drilled roll and a spiral roll. The surface state of the third cooling roll 6 is preferably a mirror surface.

  The resin film wound around the second cooling roll 5 is passed between the second cooling roll 5 and the third cooling roll 6 so as to be wound around the third cooling roll 6. A predetermined gap may be provided between the second cooling roll 5 and the third cooling roll 6 so as to be in a released state or may be sandwiched between both rolls. In order to cool the resin film more gently, a fourth cooling roll, a fifth cooling roll,... And a plurality of cooling rolls are provided after the third cooling roll 6 and wound around the third cooling roll 6. The matte film may be sequentially wound around the next cooling roll.

<Method for forming film using matting agent>
The method of forming a film using a matting agent is a method of melt extrusion molding using a resin in which transparent fine particles serving as a matting agent are blended. In order to make at least one surface of the polycarbonate-based resin film obtained by the melt extrusion molding a mat surface, and to make the HDI on the mat surface within the predetermined range, the average particle diameter and addition amount of the matting agent are adjusted. do it. In addition, since HDI can be made into the said predetermined range by the effect of a matting agent, the 2nd cooling roll 5 can also employ | adopt the metal roll whose normal surface state is a mirror surface.

  In addition, the matting agent used in this case is usually a particle called a so-called light diffusing agent, and as the light diffusing agent, for example, methyl methacrylate polymer particles, styrene polymer heavy particles are used. Organic particles such as coalescence particles, siloxane polymer particles, calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, silica (silicon oxide), inorganic glass, talc, mica, white carbon, magnesium oxide, zinc oxide, etc. Examples include inorganic particles. The inorganic particles may be surface-treated with a surface treatment agent such as a fatty acid so as to be uniformly dispersed in the thermoplastic resin.

  Since polycarbonate resin films often require high light transmittance as optical properties, particles having good transparency can be preferably used as a matting agent. Further, from the viewpoint of maintaining a high light transmittance, particles that do not have a very large difference in refractive index from the base resin are suitable, and it is usually preferable that the difference in refractive index is about 0.1 or less. In the multilayer melt extrusion molding, it is preferable to select particles that do not have a large difference in refractive index from the resin forming the surface layer. In addition, the matting agent to be used may be used independently and may be used in combination of 2 or more type.

The polycarbonate resin film of the present invention is used for various purposes such as diffusion action, angle change action, prevention of sticking with other members and protection of the film surface by contact, etc. For example, in a liquid crystal display device, as a backlight unit. It can be used for a light diffusion film, a polarizing plate protective film, a retardation film, a brightness enhancement film to be incorporated, a protective film for a polarizing separation sheet, a reflective film, a light guide film, and the like. Further, the present invention can be applied to an optical disk, an illumination film, and the like, and the present invention is not limited to these uses. Especially, it can use preferably as a protective film of the polarization separation sheet in a liquid crystal display device.

  Examples of the present invention will be described below, but the present invention is not limited thereto. In the following examples, the parts representing the content or amount used are based on weight unless otherwise specified.

The structure of the extrusion apparatus used in the following examples and comparative examples is as follows.
Melt Extruder 1: Single screw extruder with vented screw diameter 115mm (Toshiba Machine Co., Ltd.)
Polymer filter 2: filter pore size 10 μm
Die 3: T die (single layer die)

  The melt extruder 1, the polymer filter 2, the die 3, the first to third cooling rolls 4 to 6 were arranged as shown in FIG. 2, and each cooling roll 4 to 6 was configured as follows.

<Roll configuration>
The 1st cooling roll 4, the 2nd cooling roll 5, and the 3rd cooling roll 6 were comprised as follows.
First cooling roll 4: Silicone rubber roll having an outer diameter of 450 mmφ and a hardness of A 70 ° Second cooling roll 5: Stainless steel metal roll (drilled roll) having an outer diameter of 450 mmφ and an irregular shape with Rz of 16.5 μm formed by blasting )
Third cooling roll 6: mirror-finished stainless steel metal roll with an outer diameter of 450 mmφ (drilled roll)

Example 1
Polycarbonate-based resin ("Caliber 301-10" made by Sumika Stylon Polycarbonate) is supplied to a 115mmφ single-screw melt extruder 1 and passed through a polymer filter 2 having a filter pore size of 10µm installed in front of the die 3 After that, a film-like resin is extruded from the die 3 at a discharge rate of 300 kg / hr, and the resin is fed to the first cooling roll 4 (set temperature: 34 ° C.) and the second cooling roll 5 (set temperature: 130 ° C.). The second cooling roll 5 is pressed against the resin, wound around the second cooling roll 5, and then between the second cooling roll 5 and the third cooling roll 6 (set temperature: 135 ° C.). Then, the film was further wound around the third cooling roll 6 to obtain a polycarbonate resin film 7 having a thickness of 130 μm whose surface in contact with the second cooling roll 5 was a mat surface.

(Comparative Example 1)
Except that the pressing pressure of the second cooling roll 5 against the resin sandwiched between the first cooling roll 4 and the second cooling roll 5 was lowered, the second cooling roll 5 was contacted in the same manner as in Example 1. A polycarbonate resin film 7 having a thickness of 130 μm and having a matte surface was obtained.

  The following evaluation was performed about each obtained polycarbonate-type resin film (Example 1, comparative example 1). The results are shown in Table 1.

<Maximum roughness (Rz)>
The maximum height roughness (Rz) on the surface of the polycarbonate resin film in contact with the second cooling roll was determined according to JIS B0601-2001 by a surface roughness meter ("Surf Test SJ-201" manufactured by Mitutoyo Corporation). ).

<Height distribution index (HDI)>
Using a three-dimensional microscope “PLμ2300” (manufactured by Sensofar), the surface shape of the surface of the polycarbonate resin film in contact with the second cooling roll was measured to create a height distribution curve of the surface shape. The measurement was performed in Symmetrical using the confocal microscope mode of the microscope, the magnification of the objective lens being 20 times, the Zscan being 100 μm pitch, the threshold value being 1.0%. The measurement area was 640 μm × 480 μm.
The maximum value of the Y-axis in the obtained height distribution curve was 100%, the value of X when Y was 100% was 0 μm, and the range of X where Y was 20% or more was HDI.

<Surface haze>
Water was applied to the surface of the obtained polycarbonate resin film in contact with the first cooling roll, and an acrylic resin plate ("Sumipex E000" manufactured by Sumitomo Chemical Co., Ltd.) 1 mm thick on the applied water 1 Sheets were placed to produce a laminate. The haze of the obtained laminate was measured according to JIS K 7136, and the obtained value was defined as the surface haze.

<Retardation value>
A test piece was cut out in a 50 mm square size from the obtained polycarbonate-based resin film, and the retardation value at 590 nm was measured with a micro area birefringence meter (“KOBRA-CCO / X” manufactured by Oji Scientific Instruments).

<Surface gloss>
Based on JIS Z8741, 60 degree glossiness of the surface which contacted the 2nd cooling roll of the obtained polycarbonate-type resin film was measured.

<Light diffusion>
In a dark room, a 5 mm thick glass plate is placed on the surface of the obtained polycarbonate resin film in contact with the second cooling roll, and a light source (incandescent lamp) is directed to the film surface from above at 45 degrees through the glass plate. The film surface was visually observed from the upper 45 degree direction of the film through a glass plate while illuminating with, and when the gloss was not confirmed on the film surface, “◯”, the gloss was confirmed on the film surface. The case was judged as “×”.

  As is clear from Table 1, the polycarbonate resin film obtained in Example 1 was excellent in light diffusibility because gloss was not confirmed on the film surface in the evaluation of light diffusibility. Since the polycarbonate resin film obtained in Example 1 has excellent light diffusibility, the display image of the liquid crystal display device looks dark even when the liquid crystal display device in which the film is used is viewed from an oblique direction. Absent. The polycarbonate-based resin film obtained in Comparative Example 1 was found to be glossy on the film surface in the evaluation of light diffusibility, and the light diffusibility was insufficient. Since the polycarbonate resin film obtained in Comparative Example 1 has insufficient light diffusibility, the display image of the liquid crystal display device looks dark when the liquid crystal display device in which the film is used is viewed from an oblique direction. .

DESCRIPTION OF SYMBOLS 1 Melt extruder 2 Polymer filter 3 Die 4 1st cooling roll 5 2nd cooling roll 6 3rd cooling roll 7 Polycarbonate-type resin film 8 Backlight unit 9 Polarization separation sheet 10 Polarization separation sheet protective film 11 Liquid crystal panel

Claims (8)

A polycarbonate resin film comprising a polycarbonate resin, wherein at least one surface is a mat surface, and a height distribution index on the mat surface is 9 to 15. The polycarbonate resin film according to claim 1, wherein the polycarbonate resin film has a thickness of 30 to 300 µm and a total light transmittance of 85% or more. The polycarbonate resin film according to claim 1 or 2, wherein the haze is 50% or more. The polycarbonate resin film according to claim 1, which has a surface glossiness of 50% or less. The polycarbonate resin film according to claim 1, wherein the retardation of incident light having a wavelength of 590 nm is 30 nm or less. The polycarbonate resin film according to claim 1, which is formed by melt extrusion of a polycarbonate resin. The polycarbonate-type resin film in any one of Claims 1-6 used for a liquid crystal display device. The polycarbonate-type resin film of Claim 7 used for protection of the polarization separation sheet in the said liquid crystal display device.

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