Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
  • G02B1/14—Protective coatings, e.g. hard coatings
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/02—Physical, chemical or physicochemical properties
  • B32B7/023—Optical properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/06—Interconnection of layers permitting easy separation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J7/00—Adhesives in the form of films or foils
  • C09J7/20—Adhesives in the form of films or foils characterised by their carriers
  • C09J7/22—Plastics; Metallised plastics
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J7/00—Adhesives in the form of films or foils
  • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
  • C09J7/38—Pressure-sensitive adhesives [PSA]
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/30—Polarising elements
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/30—Polarising elements
  • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
  • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/30—Polarising elements
  • G02B5/3083—Birefringent or phase retarding elements

Definitions

• the present invention relates to a substrate for a surface protective film, a surface protective film using the substrate, and an optical film with a surface protective film.
• An optical film for example, a polarizing plate or a laminate including a polarizing plate
• An optical film includes the optical film (finally, the image display device) until the image display device to which the optical film is applied is actually used.
• a surface protection film is releasably attached.
• an optical display / surface protective film laminate is bonded to a display cell to produce an image display device, and the image display device is subjected to an optical test (for example, a lighting test) in a state where the laminate is bonded. ), And at an appropriate time thereafter, the surface protective film is peeled off.
• the surface protective film typically has a resin film as a substrate and an adhesive layer.
• the present invention has been made in order to solve the above conventional problems, and a main object of the present invention is to provide a surface protection film base material capable of favorably suppressing light leakage during optical inspection, coloring and rainbow unevenness. It is in.
• the phase difference R0 (550) in the front direction and the phase difference R45 (550) in the polar angle of 45 ° and the azimuth angle of 45 ° satisfy the following relationship: R45 (550) -R0 (550) ⁇ 13 (nm).
• the base material for a surface protective film has a front-side retardation R0 (550) of 20 nm or less.
• the substrate for a surface protective film has a total light transmittance of 80% or more and a haze of 1.0% or less.
• the substrate for a surface protection film contains at least one resin selected from polycarbonate, polyester, cycloolefin-based resin, acrylic resin, and cellulose resin. In one embodiment, the substrate for a surface protection film contains a resin having an alicyclic structure or an aromatic ring structure exhibiting negative intrinsic birefringence.
• a surface protective film is provided. This surface protection film includes the above-mentioned substrate for a surface protection film and an adhesive layer.
• an optical film with a surface protection film includes an optical film and the above-mentioned surface protective film releasably bonded to the optical film.
• the optical inspection is performed by setting the difference between the phase difference R0 (550) in the front direction and the phase difference R45 (550) in the polar angle 45 ° and the azimuth angle 45 ° direction to a predetermined value or less. It is possible to realize a substrate for a surface protective film that can effectively suppress light leakage, coloring and rainbow unevenness at the time. In particular, in an optical inspection of a large-sized image display device, light leakage at an end can be significantly suppressed.
• the substrate for surface protective film according to the embodiment of the present invention has a phase difference R0 (550) in the front direction and a phase difference R45 (550) in the polar angle of 45 ° and the azimuth angle of 45 ° as follows. Satisfy the relationship: R45 (550) -R0 (550) ⁇ 13 (nm). [R45 (550) -R0 (550)] is preferably at most 10 nm, more preferably at most 5 nm, further preferably at most 3 nm, particularly preferably at most 1 nm.
• [R45 (550) -R0 (550)] is preferably -5 nm or more, more preferably -3 nm or more, and still more preferably -1 nm or more.
• [R45 (550) -R0 (550)] is in such a range, a substrate for a surface protective film capable of favorably suppressing light leakage, coloring and rainbow unevenness during an optical inspection can be realized, In particular, in an optical inspection of a large-sized image display device, light leakage at an end can be significantly suppressed.
• an image is taken by a camera (for example, a camera equipped with a polarizing filter) for each image display device while the image display device in which the optical film / surface protection film laminate is bonded to the display cell is transported in a roll.
• a lighting defect of the image display device is inspected.
• the angle of view of the camera becomes very large.
• the angle of view in the long side direction of the image display device is 45 ° or more in one embodiment, 60 ° or more in another embodiment, and 70 ° or more in another embodiment. In another embodiment, it may be 82 ° or more.
• the size of the image display device to which the substrate for a surface protection film (substantially, the surface protection film including the substrate) according to the embodiment of the present invention is applied is preferably 25 inches or more, more preferably 35 inches or more. Inches or more, more preferably 40 inches or more.
• the higher the definition of the image display device the more noticeable the improvement of the inspection accuracy.
• R0 ( ⁇ ) is a front-side phase difference measured with light having a wavelength of ⁇ nm at 23 ° C.
• nx is the refractive index in the direction in which the in-plane refractive index is maximized (ie, the slow axis direction)
• ny is the direction perpendicular to the slow axis in the plane (ie, fast phase). (Axial direction).
• R45 ( ⁇ ) is a phase difference in a direction of a polar angle of 45 ° and an azimuth angle of 45 ° measured with light having a wavelength of ⁇ nm at 23 ° C.
• the azimuth is a direction when the long side direction of the image display device is 0 °.
• References to angles herein include both clockwise and counterclockwise directions with respect to a reference direction.
• the front-side retardation R0 (550) of the surface protective film substrate is preferably 20 nm or less, more preferably 15 nm or less, further preferably 10 nm or less, and particularly preferably 5 nm or less.
• the phase difference R0 (550) in the front direction is preferably as small as possible, and the lower limit is ideally 0 nm, for example, 0.3 nm.
• Such a front-side phase difference R0 (550) can be realized by appropriately combining and setting the material forming the base material and the stretching conditions.
• the phase difference R45 (550) in the polar angle 45 ° and the azimuth angle 45 ° direction of the surface protective film substrate is preferably 30 nm or less, more preferably 20 nm or less, further more preferably 12 nm or less, particularly Preferably it is 7 nm or less.
• R45 (550) is in such a range, the desired [R45 (550) -R0 (550)] can be easily realized, and as a result, in the optical inspection of a large-sized image display device, the light at the end portion can be obtained. Leakage can be significantly suppressed. Similar to R0 (550), such R45 (550) can be realized by appropriately combining and setting the material forming the base material and the stretching conditions.
• the thickness direction retardation Rth (550) of the surface protective film substrate is preferably -90 nm to +90 nm, more preferably -50 nm to +50 nm, and still more preferably -20 nm to +20 nm.
• Rth ( ⁇ ) is a retardation in the thickness direction measured with light having a wavelength of ⁇ nm at 23 ° C.
• nz is the refractive index in the thickness direction.
• the substrate for a surface protective film may exhibit an inverse dispersion wavelength characteristic in which an in-plane retardation (a retardation in the front direction) increases according to the wavelength of the measurement light, and the in-plane retardation corresponds to the wavelength of the measurement light. It may show a positive wavelength dispersion characteristic that becomes smaller as a result, or may show a flat wavelength dispersion characteristic in which the in-plane phase difference hardly changes depending on the wavelength of the measurement light.
• the total light transmittance of the substrate for a surface protective film is preferably 80% or more, more preferably 85% or more, further preferably 90% or more, and particularly preferably 95% or more.
• the haze of the surface protective film substrate is preferably 1.0% or less, more preferably 0.7% or less, further preferably 0.5% or less, and particularly preferably 0.3% or less. % Or less. If the total light transmittance or haze is within such a range, when the surface protective film using the substrate for a surface protective film of the present invention is subjected to optical inspection of an image display device, excellent visibility is ensured. be able to. As a result, the accuracy of the optical inspection of the image display device can be significantly improved.
• the base material for a surface protective film has a number of bending times to break in an MIT test of preferably 500 or more, more preferably 700 or more, still more preferably 900 or more, and particularly preferably 1100 or more. is there. That is, the substrate for a surface protective film can preferably have excellent flexibility or bending resistance. With such a configuration, it is possible to obtain a surface protective film which is excellent in operability at the time of laminating and peeling and in which cracking is suppressed. According to the embodiment of the present invention, it is possible to achieve both such excellent flexibility or bending resistance and the extremely small front-side phase difference R0 (550) as described above.
• the MIT test can be performed in accordance with JIS P # 8115.
• the substrate for a surface protective film has a water absorption of preferably 5% or less, more preferably 4% or less, and further preferably 2% or less.
• the substrate for a surface protective film has a moisture permeability of preferably not more than 400 g / m 2 ⁇ 24 h, more preferably 160 g / m 2 ⁇ after being left for 24 hours in an environment of 40 ° C. and 92% RH. and at 24h or less, still more preferably not more than 130 g / m 2 ⁇ 24h, most preferably not more than 90g / m 2 ⁇ 24h. If the water absorption or the moisture permeability is in such a range, it is possible to suppress floating in a humid environment.
• a water absorption can be measured based on JISK7209.
• the water vapor transmission rate can be measured according to JIS Z 0208 (temperature and humidity conditions: 40 ° C., 90% RH).
• the substrate for a surface protective film has a glass transition temperature (Tg) of preferably 145 ° C or higher, more preferably 160 ° C or higher.
• Tg glass transition temperature
• the pressure-sensitive adhesive layer can be formed by directly applying the pressure-sensitive adhesive layer to the surface protective film base when producing the surface protective film. In other words, there is no need to transfer the pressure-sensitive adhesive layer formed on the predetermined film to the substrate for the surface protection film. Therefore, a surface protection film can be produced with extremely excellent production efficiency.
• the upper limit of the Tg of the substrate for a surface protective film may be, for example, 200 ° C.
• the elastic modulus of the surface protective film substrate is preferably 50 MPa to 350 MPa at a tensile speed of 100 mm / min.
• a surface protective film having excellent transportability and operability can be obtained.
• the modulus of elasticity is measured according to JIS K7127: 1999.
• the tensile elongation of the substrate for a surface protective film is preferably 70% to 200%.
• the tensile elongation is measured according to JIS @ K # 6781.
• the substrate for a surface protective film can be made of any appropriate material as long as it has the desired properties as described above.
• the substrate for a surface protection film can be typically composed of a resin film.
• the resin constituting the film include polyarylate, polyamide, polyimide, polyester, polyaryletherketone, polyamideimide, polyesterimide, polyvinyl alcohol, polyfumarate, polyethersulfone, polysulfone, and cycloolefin-based resins (for example, , A norbornene-based resin), polycarbonate, polyester carbonate, a cellulose resin (eg, triacetyl cellulose), an acrylic resin, and a polyurethane. These resins may be used alone or in combination.
• the resin may have an alicyclic structure or an aromatic ring structure exhibiting negative intrinsic birefringence.
• the alicyclic structure include a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, an N-substituted maleimide structure, and a maleic anhydride structure.
• the aromatic ring structure exhibiting negative intrinsic birefringence include a fluorene structure, a naphthalene structure, an anthracene structure, a carbazole structure, and a phthalimide structure. Resins having these structures have a small birefringence in the resulting film and can suppress a phase difference when formed into a film.
• the substrate for the surface protective film may be, for example, a film using a film formed from the above resin as it is.
• a method of forming a film from a resin any appropriate molding method can be adopted. Specific examples include a compression molding method, a transfer molding method, an injection molding method, an extrusion molding method, a blow molding method, a powder molding method, an FRP molding method, a cast coating method (for example, a casting method), a calendar molding method, and a hot press. And the like. Extrusion molding or cast coating is preferred. This is because the smoothness of the obtained film can be improved and good optical uniformity can be obtained.
• the molding conditions can be set as appropriate according to the composition and type of the resin used, the characteristics desired for the substrate for the surface protective film, and the like.
• the base material for a surface protective film may be a film obtained by subjecting a film formed from the above resin to a stretching treatment.
• the stretching method of the film is typically biaxial stretching, and more specifically, sequential biaxial stretching or simultaneous biaxial stretching. This is because a substrate for a surface protective film having a small front-side retardation R0 (550) can be obtained.
• the sequential biaxial stretching or simultaneous biaxial stretching is typically performed using a tenter stretching machine. Therefore, the stretching direction of the film is typically the length direction and the width direction of the film.
• the stretching temperature can be changed according to R0 (550), R45 (550) and thickness desired for the surface protective film substrate, the type of resin used, the thickness of the film used, the stretching ratio, and the like.
• the stretching temperature is preferably Tg + 5 ° C. to Tg + 50 ° C., more preferably Tg + 10 ° C. to Tg + 40 ° C., with respect to the glass transition temperature (Tg) of the film.
• the stretching ratio can be changed according to R0 (550) and R45 (550) and the thickness desired for the surface protective film substrate, the type of resin used, the thickness of the film used, the stretching temperature, and the like.
• biaxial stretching for example, sequential biaxial stretching or simultaneous biaxial stretching
• stretching ratio in the first direction for example, length direction
• stretching in the second direction for example, width direction
• the magnification is preferably as small as possible, more preferably substantially equal.
• the stretching ratio is determined in the first direction (for example, the length direction) and the second direction (for example, the width direction). For each, it can be, for example, from 1.1 times to 3.0 times.
• the stretching speed is preferably 10% / sec or less, more preferably 7% / sec or less, further preferably 5% / sec or less, and particularly preferably 2.5% / sec or less.
• the lower limit of the stretching speed can be, for example, 1.2% / sec. If the stretching speed is too low, the productivity may not be practical.
• biaxial stretching for example, sequential biaxial stretching or simultaneous biaxial stretching
• the stretching speed in the first direction (for example, the length direction) and the second direction (for example, the width direction) Is preferably as small as possible, and more preferably substantially equal. With such a configuration, R0 (550) and R45 (550) can be further reduced.
• the substrate for a surface protective film may be a commercially available resin film as it is, or may be formed by subjecting a commercially available resin film to the above-described stretching treatment.
• the thickness of the substrate for a surface protection film is typically from 10 ⁇ m to 100 ⁇ m, preferably from 20 ⁇ m to 70 ⁇ m.
• the substrate for a surface protective film may have a slow axis.
• the slow axis direction of the surface protection film substrate is relative to the long side direction of the image display device. It is preferably at most 30 °, more preferably at most 15 °, even more preferably at most 5 °, particularly preferably at most 2 °.
• the slow axis is manifested when the front-side phase difference substantially exists. When the front-side phase difference approaches zero and substantially does not exist, the influence of the slow axis is small. Become.
• the substrate for a surface protective film described in the above section A can be suitably used for a surface protective film. Therefore, embodiments of the present invention also include a surface protection film.
• the surface protective film according to the embodiment of the present invention includes the surface protective film substrate described in the above section A and an adhesive layer.
• any suitable pressure-sensitive adhesive can be adopted as the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer.
• the base resin of the pressure-sensitive adhesive include an acrylic resin, a styrene resin, a silicone resin, a urethane resin, and a rubber resin. Such a base resin is described in, for example, JP-A-2015-120337 or JP-A-2011-201983. The descriptions in these publications are incorporated herein by reference. Acrylic resins are preferred from the viewpoints of chemical resistance, adhesion for preventing the intrusion of the treatment liquid during immersion, and the degree of freedom for the adherend.
• the crosslinking agent that can be included in the pressure-sensitive adhesive include an isocyanate compound, an epoxy compound, and an aziridine compound.
• the pressure-sensitive adhesive may include, for example, a silane coupling agent. The formulation of the pressure-sensitive adhesive can be appropriately set according to the purpose and desired properties.
• the storage elastic modulus of the pressure-sensitive adhesive layer is preferably from 1.0 ⁇ 10 4 Pa to 1.0 ⁇ 10 7 Pa, and more preferably from 2.0 ⁇ 10 4 Pa to 5.0 ⁇ 10 6 Pa.
• the storage elastic modulus can be determined, for example, from dynamic viscoelasticity measurement at a temperature of 23 ° C. and an angular velocity of 0.1 rad / s.
• the thickness of the pressure-sensitive adhesive layer is preferably 1 ⁇ m to 60 ⁇ m, more preferably 3 ⁇ m to 30 ⁇ m. If the thickness is too small, the adhesiveness becomes insufficient, and air bubbles and the like may enter the adhesive interface. If the thickness is too large, problems such as sticking out of the pressure-sensitive adhesive tend to occur.
• the separator is temporarily attached to the surface of the pressure-sensitive adhesive layer in a releasable manner until the surface protective film is actually used (that is, the surface protective film is bonded to an optical film or an image display device).
• the separator include a plastic (eg, polyethylene terephthalate (PET), polyethylene, polypropylene) film, nonwoven fabric, or the like, which is surface-coated with a release agent such as a silicone release agent, a fluorine release agent, or a long-chain alkyl acrylate release agent. Paper and the like. Any appropriate thickness can be adopted for the thickness of the separator depending on the purpose.
• the thickness of the separator is, for example, 10 ⁇ m to 100 ⁇ m.
• the embodiment of the present invention also includes an optical film with a surface protection film.
• An optical film with a surface protective film according to an embodiment of the present invention includes an optical film and the surface protective film according to the above item B, which is releasably attached to the optical film.
• the optical film may be a single film or a laminate.
• Specific examples of the optical film include a polarizer, a retardation film, a polarizing plate (typically, a laminate of a polarizer and a protective film), a conductive film for a touch panel, a surface-treated film, and for these purposes.
• a laminate for example, an anti-reflection circular polarizer, a polarizer with a conductive layer for a touch panel, a polarizer with a retardation layer, and a prism sheet-integrated polarizer
• appropriately laminated according to the requirements is given.
• the angle between the absorption axis direction of the polarizer and the slow axis direction of the surface protective film substrate is preferably 0 ° ⁇ 30 ° or 90 ° ⁇ 30 °, Preferably it is 0 ° ⁇ 15 ° or 90 ° ⁇ 15 °, more preferably 0 ° ⁇ 5 ° or 90 ° ⁇ 5 °.
• the angle is in such a range, light leakage, coloring, and rainbow unevenness during an optical inspection can be satisfactorily suppressed. Particularly, in an optical inspection of a large-sized image display device, light leakage at an end portion is remarkable. Can be suppressed.
• R0 (550), thickness direction retardation Rth (550) and R45 (550) The base material for a surface protective film obtained in each of the examples and comparative examples was cut into a length of 4 cm and a width of 4 cm to obtain a measurement sample.
• R0 (550), thickness direction retardation Rth (550), and R45 (550) of the measurement sample were measured using a product name "Axoscan" manufactured by Axometrics.
• the measurement wavelength was 550 nm, and the measurement temperature was 23 ° C.
• Nijimura The surface protective film substrates obtained in the examples and comparative examples were arranged between two polarizing plates in a crossed Nicols state.
• the surface protection film substrate was disposed such that the length direction of the surface protection film substrate was parallel to the transmission axis direction of one of the polarizing plates.
• light from a fluorescent lamp was irradiated from below the lower polarizing plate, and the presence or absence of rainbow unevenness was visually observed.
• Evaluation was made according to the following criteria. :: No rainbow unevenness was observed. ⁇ : Slight rainbow unevenness was observed. X: Rainbow unevenness was significantly observed. (3) Brightness Commercially available liquid crystal television (manufactured by LG, 49 inches, product name “49SJ8000”)
• the base material for a surface protective film obtained in each of Examples and Comparative Examples was bonded to the viewing-side polarizing plate of (2) via an adhesive.
• the surface protective films including the substrate for a surface protective film obtained in Examples and Comparative Examples were bonded.
• the entire input image was displayed in white and turned on.
• the brightness of the lit liquid crystal television was measured using a product name “SR-UL2” manufactured by Topcon Technohouse Co., Ltd.
• “REGQ1298DUHC3” manufactured by Nitto Denko Corporation was attached to the lens portion of SL-UL2 in an axial arrangement so as to be crossed with the viewing side polarizing plate, and the luminance was measured.
• the directions of measurement were a total of three places: a front direction, a 45 ° azimuth azimuth 45 ° direction, and a 45 ° azimuth 135 ° azimuth direction.
• Example 1 After vacuum drying a commercially available polycarbonate resin film (manufactured by Mitsubishi Chemical Corporation, trade name “DURABIO T7450A”) at 105 ° C. for 5 hours, a single screw extruder (manufactured by Toshiba Machine Co., cylinder temperature 230 ° C.), a T-die (width) A film having a thickness of 40 ⁇ m was prepared using a film forming apparatus equipped with a cast roll (temperature: 1700 mm, temperature: 230 ° C.), a cast roll (temperature: 120 ° C.) and a winder, and used as a substrate for a surface protective film. This film exhibited flat wavelength dispersion characteristics.
• R0 (550) of the obtained base material for surface protective film was 5.6 nm
• Rth (550) was 11.5 nm
• R45 (550) was 6.02 nm
• [R45 (550) -R0 (550)] was 0.42 nm.
• the obtained substrate for a surface protective film was subjected to the above-mentioned evaluations (2) to (4). Table 1 shows the results.
• Example 2 A substrate for a surface protective film (thickness: 15 ⁇ m) was obtained in the same manner as in Example 1 except that the extrusion amount of the extruder and the speed of the cast roll were adjusted.
• R0 (550) of the obtained base material for surface protective film was 11.2 nm
• Rth (550) was 17.8 nm
• R45 (550) was 11.9 nm
• [R45 (550) -R0 (550)] was 0.7 nm.
• the obtained substrate for a surface protective film was subjected to the above-mentioned evaluations (2) to (4). Table 1 shows the results.
• Example 3 Commercially available polycarbonate resin (trade name “Iupilon H-4000” manufactured by Mitsubishi Engineering-Plastics Corporation) was vacuum-dried at 120 ° C. for 5 hours, and then a single-screw extruder (manufactured by Toshiba Machine Co., cylinder temperature 255 ° C.), T Using a film forming apparatus equipped with a die (width 1700 mm, temperature 255 ° C.), cast roll (temperature 130 ° C.) and a winder, a film having a thickness of 40 ⁇ m was prepared and used as a substrate for a surface protective film.
• a single-screw extruder manufactured by Toshiba Machine Co., cylinder temperature 255 ° C.
• T Using a film forming apparatus equipped with a die (width 1700 mm, temperature 255 ° C.), cast roll (temperature 130 ° C.) and a winder, a film having a thickness of 40 ⁇ m was prepared and used as a substrate for
• R0 (550) of the obtained base material for surface protective film was 2.6 nm
• Rth (550) was 43.9 nm
• R45 (550) was 15.1 nm
• [R45 (550) ⁇ R0 ( 550)] was 12.5 nm
• the obtained substrate for a surface protective film was subjected to the evaluations of the above (2) to (4), and the results are shown in Table 1.
• Example 4 A polymer alloy film was prepared using the following raw materials.
• R0 (550) of the obtained base material for surface protective film was 20 nm
• Rth (550) was 85 nm
• R45 (550) was 28.1 nm
• [R45 (550) -R0 (550)]. was 8.1 nm.
• the obtained substrate for a surface protective film was subjected to the above-mentioned evaluations (2) to (4). Table 1 shows the results.
• Example 5 A commercially available triacetyl cellulose (TAC) film (manufactured by FUJIFILM Corporation, product name "TD80UL”) was used as it was to prepare a substrate for a surface protection film (thickness: 80 m).
• R0 (550) of the substrate for a surface protective film is 4.9 nm
• Rth (550) is 52.6 nm
• R45 (550) is 8.7 nm
• [R45 (550) -R0 (550). ] was 3.8 nm.
• the substrate for a surface protective film was subjected to the evaluations (2) to (4) above. Table 1 shows the results.
• Example 6 A substrate for a surface protection film (thickness: 40 ⁇ m) was obtained in the same manner as in Example 1 except that a commercially available cycloolefin-based resin film (manufactured by Zeon Corporation, product name “ZF14”) was used.
• R0 (550) of the obtained base material for surface protective film was 2.0 nm
• Rth (550) was 7.9 nm
• R45 (550) was 2.7 nm
• [R45 (550) -R0 (550)] was 0.7 nm.
• the obtained substrate for a surface protective film was subjected to the above-mentioned evaluations (2) to (4). Table 1 shows the results.
• Example 7 After vacuum drying a commercially available acrylic resin (trade name “CM-205”, manufactured by Kimei Industry Co., Ltd.) at 100 ° C. for 5 hours, a single screw extruder (manufactured by Toshiba Machine Co., cylinder temperature 230 ° C.), T-die (width) A film having a thickness of 160 ⁇ m was produced using a film forming apparatus equipped with a cast roll (temperature 1100 mm, temperature 230 ° C.), a cast roll (temperature 100 ° C.) and a winder. This film was simultaneously biaxially stretched twice in the length and width directions. The stretching temperature was 146 ° C., and the stretching speed was 7.1% / sec in both the length and width directions.
• CM-205 commercially available acrylic resin
• a single screw extruder manufactured by Toshiba Machine Co., cylinder temperature 230 ° C.
• T-die width
• a film having a thickness of 160 ⁇ m was produced using a film forming apparatus equipped with a cast roll
• a substrate for a surface protective film (thickness: 40 ⁇ m) was obtained.
• R0 (550) of the obtained substrate for surface protective film was 0.5 nm
• Rth (550) was ⁇ 39 nm
• R45 (550) was 10.1 nm
• [R45 (550) ⁇ R0 ( 550)] was 9.6 nm.
• the obtained substrate for a surface protective film was subjected to the above-mentioned evaluations (2) to (4). Table 1 shows the results.
• a substrate for a surface protective film (40 ⁇ m in thickness) was obtained in the same manner as in Example 4 except that the stretching temperature was 167 ° C.
• R0 (550) of the obtained base material for surface protective film is 32 nm
• Rth (550) is 91 nm
• R45 (550) is 45.1 nm
• [R45 (550) -R0 (550)] was 13.1 nm.
• the obtained substrate for a surface protective film was subjected to the above-mentioned evaluations (2) to (4). Table 1 shows the results.
• a substrate for a surface protection film (thickness: 80 ⁇ m) was obtained in the same manner as in Example 3 except that the thickness was changed to 80 ⁇ m.
• R0 (550) of the obtained base material for surface protective film is 5.6 nm
• Rth (550) is 102.6 nm
• R45 (550) is 19.4 nm
• [R45 (550) -R0 (550)] was 13.8 nm.
• the obtained substrate for a surface protective film was subjected to the above-mentioned evaluations (2) to (4). Table 1 shows the results.
• ⁇ Comparative Example 3> A commercially available ultra-high retardation polyethylene terephthalate film (trade name “Diafoil MRF38CK” manufactured by Mitsubishi Chemical Corporation) was used as it was to prepare a substrate for a surface protection film (thickness: 38 ⁇ m).
• R0 (550) of the substrate for surface protective film is 2950 nm
• Rth (550) is 8899.4 nm
• R45 (550) is 3445.5 nm
• [R45 (550) -R0 (550)] is It was 495.5 nm.
• the substrate for a surface protective film was subjected to the evaluations (2) to (4) above. Table 1 shows the results.
• the substrate for a surface protective film of the example of the present invention prevents rainbow unevenness, has excellent total light transmittance, and suppresses light leakage at the end. . In addition, it was confirmed that the same result as that of rainbow unevenness and light leakage was obtained for coloring.
• the substrate for a surface protective film of the present invention is suitably used for a surface protective film.
• the surface protective film of the present invention is used to protect the optical film until the optical film (finally, the image display device) is actually used.

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