JP2016107498A - Surface protection film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface protection film which has a high ultraviolet shielding function, hardly causes coloring and has sufficient scratch resistance to protect the surface of a member such as a polarizer.SOLUTION: There is provided a surface protection film having a substrate film and a surface protection layer, wherein the surface protection layer is a cured product of an ionizing radiation-curable resin composition which comprises a resin component containing an ionizing radiation-curable compound, an ultraviolet absorbing agent having a molecular weight of less than 1000 and an ultraviolet absorbing agent having a weight average molecular weight of 1000 or more and the ultraviolet absorbing agent having a molecular weight of less than 1000 satisfies the following expression (1). (The transmittance at a wavelength of 390 nm/The transmittance at a wavelength of 380 nm)≥1.40 (1)SELECTED DRAWING: Figure 1

Description

  The present invention relates to a surface protective film, a front plate of a display element using the same, and a display device.

In an image display device such as a liquid crystal display device, a surface protective film is used for the purpose of preventing the surface of the display device from being damaged, or preventing various members that may occur during the manufacturing process. The surface protective film is used, for example, as a film for protecting the surface of various members such as a polarizer constituting the front plate in addition to the surface protection of the front plate installed on the display elements of various image display devices. The surface protective film has at least a base material and a surface protective layer such as a hard coat layer, and is provided with various functions such as ultraviolet absorbing ability, antifouling function and antireflection according to the required performance. Has been developed.
Among these, a film having a base material and a surface protective layer made of an ultraviolet curable resin composition is known as a surface protective film having an ultraviolet cut function. The film is used not only for the purpose of protecting the surface of the image display device and each member constituting the image display device, but also for absorbing ultraviolet light from outside light or a light source and preventing ultraviolet deterioration of each member constituting the image display device. ing.
Examples of the surface protective film include those in which an ultraviolet absorber is added to the base material to give an ultraviolet cut function to the base material side (Patent Documents 1 and 2), and an ultraviolet absorber is added to the surface protective layer side. In other words, a material having an ultraviolet cut function is known (Patent Document 3).

JP 2013-20114 A JP 2012-72235 A JP 2009-6513 A

However, depending on the type of substrate, it may be difficult to add an ultraviolet absorber. Moreover, the surface protective film which has a base material and surface protective layers including a hard-coat layer is normally provided so that a surface protective layer may become the surface side (observer side) of an image display apparatus. Therefore, the film provided with the ultraviolet cut function on the surface protective layer side is more advantageous than the films disclosed in Patent Documents 1 and 2 from the viewpoint of protection from external light ultraviolet rays.
In view of this, the present inventors have developed a surface protective film having a UV protection function on the surface protective layer side. From the viewpoint of the ultraviolet cut function, it is desired that the transmittance of the surface protective layer at a wavelength of 380 nm is 10% or less, preferably 8% or less. Further, from the viewpoint of visibility, it is desirable that the surface protective film is colorless (that is, the absorption in the visible light region is small). However, when an ultraviolet absorber having strong absorption near a wavelength of 380 nm is used, the surface protective layer is formed. May be colored yellow. Although the hard coat film disclosed in Patent Document 3 has a low transmittance at a wavelength of 380 nm, there is no mention of coloring.
On the other hand, ultraviolet absorbers with little absorption in the visible light region may have low ultraviolet absorption ability at wavelengths of 380 nm or less, and increasing the amount of ultraviolet absorber used to compensate for this will reduce the hardness of the surface protective layer. Tend. As described above, it has been difficult to obtain a surface protective film satisfying all the properties of an ultraviolet cut function, low colorability, and high hardness.

In recent years, touch panel functions are mounted on portable liquid crystal terminals such as smartphones and other liquid crystal display devices. Conventionally, the liquid crystal display device equipped with such a touch panel function is mainly an external type in which a touch panel is mounted on the liquid crystal display device.
Since the external type is integrated after the liquid crystal display device and the touch panel are manufactured separately, one of them can be used even if there is a defect, and the yield is excellent. There was a problem that increased.
In order to solve such a problem, a so-called on-cell type liquid crystal display device in which a touch panel is incorporated between a liquid crystal element of a liquid crystal display device and a polarizing plate has appeared. In recent years, a so-called in-cell type liquid crystal display device in which a touch function is incorporated in a liquid crystal element has been developed to further reduce the thickness and weight of the on-cell type.

In the in-cell type liquid crystal display device, it is considered that the liquid crystal element portion incorporating the touch function is sufficiently thin in the overall configuration. However, a sufficient reduction in thickness of the front plate installed on the liquid crystal element has not been studied.
The in-cell type liquid crystal display device has a configuration in which a front plate in which films having various functions are bonded to each other via an adhesive layer on a liquid crystal element incorporating a touch function. Examples of the film having various functions include a retardation plate, a polarizer, a protective film for a polarizer, and a surface protective member.
As a protective film for the polarizer, a triacetyl cellulose (TAC) film having no optical anisotropy is used. However, the TAC film is used only for the purpose of protecting the polarizer, and the TAC film may be omitted from the viewpoint of the optical function of the front plate. Therefore, the above-mentioned surface protective member is also configured to serve as a protective film for the polarizer, thereby reducing the TAC film and the adhesive layer for bonding this to other layers, and studying to reduce the thickness of the front plate. Has been done.
Here, since a UV absorber is usually added to the TAC film, it also has a function of preventing UV deterioration of a polarizer or the like provided on the inner side (liquid crystal element side) than the TAC film. Therefore, in order to reduce the TAC film, it is necessary to separately provide an ultraviolet cut function to another layer provided on the outer side (observer side) than the polarizer.
Therefore, if the surface protective film having the ultraviolet ray blocking function as described above is used as the film having the protective film of the polarizer and the surface protective member, the TAC film and the adhesive layer are reduced, and the front plate and the display using the same The apparatus can be thinned.

  An object of the present invention is to provide a surface protective film having a high ultraviolet ray cutting function, little coloring, and sufficient scratch resistance to protect the surface of a member such as a polarizer.

In the surface protective film having the base film and the surface protective layer, the present inventors use a specific ultraviolet absorber in combination with the ionizing radiation curable resin composition for forming the surface protective layer. It has been found that the above problems can be solved.
That is, the present invention is a surface protective film having a base film and a surface protective layer, wherein the surface protective layer comprises a resin component containing an ionizing radiation curable compound, an ultraviolet absorber having a molecular weight of less than 1,000, A cured product of an ionizing radiation curable resin composition containing an ultraviolet absorber having a weight average molecular weight of 1,000 or more, wherein the ultraviolet absorber having a molecular weight of less than 1,000 satisfies the following formula (1): The present invention relates to a surface protective film.
(Transmittance at a wavelength of 390 nm / Transmittance at a wavelength of 380 nm) ≧ 1.40 (1)
The present invention also relates to a front plate of a display element having a polarizing plate and the surface protective film, and a display device having the front plate.

The surface protective film of the present invention has a high UV-cutting function, is less colored, and has sufficient scratch resistance to protect the surface of a member such as a polarizer. It is suitably used as a member constituting the front plate of the display device.
Moreover, since the surface protection film of this invention has the said performance, it has the function as a protective film of a polarizer used for the front plate installed on a display element, and a surface protection member. Therefore, by using the surface protective film of the present invention, the number of constituent members can be reduced, and the front plate and the display device can be thinned. In particular, the surface protective film of the present invention is suitably used for in-cell type liquid crystal display devices including in-cell touch panel liquid crystal display devices.

It is sectional drawing which shows one Embodiment of the surface protection film of this invention. It is sectional drawing which shows one Embodiment of the front plate of this invention.

[Surface protection film]
The surface protective film of the present invention has a base film and a surface protective layer, and the surface protective layer comprises a resin component containing an ionizing radiation curable compound, an ultraviolet absorber having a molecular weight of less than 1,000, and a weight average. A cured product of an ionizing radiation curable resin composition containing an ultraviolet absorber having a molecular weight of 1,000 or more, and an ultraviolet absorber having a molecular weight of less than 1,000 satisfies the following formula (1).
(Transmittance at a wavelength of 390 nm / Transmittance at a wavelength of 380 nm) ≧ 1.40 (1)

<Base film>
As a base film used for the surface protective film of the present invention, a base film having light permeability (hereinafter, also referred to as “light-transmitting base film”) is preferable. Examples of the light transmissive substrate film include resin substrates used in conventionally known optical films. The total light transmittance of the light transmissive substrate film is usually 70% or more, preferably 85% or more. The total light transmittance can be measured at room temperature and in the atmosphere using an ultraviolet-visible spectrophotometer.
The material constituting the light transmissive substrate film includes acetyl cellulose resin, polyester resin, polyolefin resin, (meth) acrylic resin, polyurethane resin, polyethersulfone resin, polycarbonate resin, polysulfone resin. Examples include resins, polyether resins, polyether ketone resins, (meth) acrylonitrile resins, cycloolefin resins, and the like. Among the above, at least one selected from acetyl cellulose resins, polyester resins, polyolefin resins, and (meth) acrylic resins is preferable from the viewpoints of economy and processability.

  The base film preferably has optical anisotropy (hereinafter, the base film having optical anisotropy is also referred to as “optically anisotropic base material”). Since the optically anisotropic substrate has the property of disturbing the linearly polarized light emitted from the polarizer, in the case of an image display device (for example, a liquid crystal display device) configured to emit linearly polarized light from the polarizer, the display screen is polarized sunglasses. It is possible to prevent the display screen from becoming invisible due to the angle between the linearly polarized light and the polarized sunglasses.

  As an optically anisotropic substrate, a retardation film having a retardation value of 3000 to 30000 nm (hereinafter also referred to as “high retardation film”) or a plastic film having a quarter wavelength retardation (hereinafter also referred to as “¼ wavelength retardation film”). ) And the like. When the optically anisotropic substrate is a high retardation film or a quarter-wave retardation film, when the display screen such as a liquid crystal screen is observed with polarized sunglasses, the display screen has different colors (hereinafter also referred to as “NIJIMURA”). ) Can be prevented. Nizimura is particularly conspicuous when the display screen is observed obliquely, but it can be prevented by using the above film as a base film. When the light emitted from the polarizer is incident on the high retardation film, the light passing through the film has an extremely large phase difference variation due to the wavelength, so that it is difficult to see the Nijimura when viewing the display screen through the polarized sunglasses. There is an effect. Moreover, since the 1/4 wavelength phase difference film has the property to convert the linearly polarized light emitted from the polarizer into circularly polarized light, it is possible to prevent azimuth irregularities.

A high retardation film or quarter-wave retardation film having optical anisotropy is suitable as a base film for a surface protective film of an image display device in which linearly polarized light is emitted from a polarizer. This will be described by taking a front plate used for an in-cell touch panel type liquid crystal display element as an example.
The front plate has a retardation plate, a polarizer, a polarizer protective film, and a surface protective member, and a TAC film is usually used as the polarizer protective film. However, since the TAC film does not have optical anisotropy, it is necessary to separately provide a functional layer for improving the visibility and the like in order to improve the visibility through the polarized sunglasses and the azimuth. Therefore, this increases the thickness of the front plate.
Therefore, when a high retardation film or quarter-wave retardation film having optical anisotropy is used as the base film of the surface protective film, and this is used as the surface protective member of the front plate, it becomes an in-cell touch panel type liquid crystal display element or the like. In various front plates used, it is not necessary to provide surface protection characteristics and to provide a separate functional layer for improving visibility, etc., so that the thickness can be reduced compared to the conventional configuration. .

When the retardation value is 3000 nm or more, the high retardation film having a retardation value of 3000 to 30000 nm can prevent the occurrence of Nizimura on the display screen when the display screen is observed with polarized sunglasses. If the retardation value is increased too much, the effect of improving the azimuth cannot be seen. Therefore, by setting the retardation value to 30000 nm or less, it is possible to prevent the film thickness from being increased more than necessary.
It is preferable that the retardation value of a high retardation film is 6000-30000 nm.
In addition, it is preferable that the retardation value mentioned above is satisfy | filled with respect to the wavelength of about 589.3 nm wavelength.

The retardation value (nm) is the refractive index (nx) in the direction having the highest refractive index (slow axis direction) and the refractive index in the direction orthogonal to the slow axis direction (fast axis direction) in the plane of the plastic film. (Ny) and the thickness (d) (nm) of the plastic film are expressed by the following equation.
Retardation value (Re) = (nx−ny) × d
The retardation value can be measured, for example, by KOBRA-WR manufactured by Oji Scientific Instruments (measurement angle: 0 °, measurement wavelength: 589.3 nm).
Alternatively, the retardation value is obtained by using two polarizing plates to determine the orientation axis direction (principal axis direction) of the substrate, and the refractive indexes (nx, ny) of two axes orthogonal to the orientation axis direction. The axis showing a large refractive index determined by an Abbe refractive index difference meter (NAR-AT, manufactured by Atago Co., Ltd.) is defined as the slow axis. A retardation value is obtained by multiplying the refractive index difference (nx−ny) thus determined by the thickness measured using an electric micrometer (manufactured by Anritsu Co., Ltd.).
In the present invention, nx-ny (hereinafter sometimes referred to as “Δn”) is preferably 0.05 or more, more preferably 0.07 or more, and still more preferably 0.10 or more. If Δn is 0.05 or more, a high retardation value can be obtained even if the thickness of the base film is thin.

  As a material constituting the high retardation film, those exemplified as the light-transmitting substrate film can be used. Among these, polyester resins are preferable, and among these, polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are more preferable.

  When the high retardation film is made of a polyester-based resin such as PET, for example, the polyester of the material is melted, and the unstretched polyester extruded and formed into a sheet is horizontally stretched using a tenter or the like at a temperature equal to or higher than the glass transition temperature. Thereafter, it can be obtained by heat treatment. The transverse stretching temperature is preferably 80 to 130 ° C, more preferably 90 to 120 ° C. Further, the transverse draw ratio is preferably 2.5 to 6.0 times, and more preferably 3.0 to 5.5 times. By setting the draw ratio to 2.5 times or more, the draw tension can be increased, the birefringence of the resulting film is increased, and the retardation value can be 3000 nm or more. Moreover, the fall of the transparency of a film can be prevented by making a horizontal stretch ratio into 6.0 times or less.

  Examples of the method for controlling the retardation value of the high retardation film produced by the above-described method to 3000 nm or more include a method of appropriately setting the stretching ratio, the stretching temperature, and the film thickness of the produced high retardation film. Specifically, for example, the higher the draw ratio, the lower the drawing temperature, and the thicker the film thickness, the easier it is to obtain a high retardation value.

  Among optically anisotropic substrates, as a plastic film having a quarter wavelength retardation, a positive quarter wavelength retardation film having a retardation of 550 nm of 137.5 nm can be used, but a retardation of 550 nm is 80. A substantially quarter-wave retardation film that is ˜170 nm can also be used. These positive quarter-wave retardation films and substantially quarter-wave retardation films can prevent azimuth from appearing in a display image of a liquid crystal display device when observed with polarized sunglasses, and a high retardation film. Compared to the above, it is preferable in that the film thickness can be reduced.

A quarter-wave retardation film is obtained by stretching a plastic film uniaxially or biaxially, or by regularly arranging liquid crystal materials in a plastic film or a layer provided on the plastic film. Can be formed. As the plastic film, for example, a film made of polycarbonate, polyester, polyvinyl alcohol, polystyrene, polysulfone, polymethyl methacrylate, polypropylene, cellulose acetate polymer polyamide, cycloolefin polymer, or the like can be used. Among these, those obtained by stretching a plastic film are preferred from the viewpoint of the ease of the production process in which a quarter-wave phase difference can be given in the stretching step, and particularly those obtained by stretching a polycarbonate, cycloolefin polymer or polyester film. preferable.
In addition, a positive 1/4 wavelength phase difference film can be obtained by adjusting a draw ratio, a draw temperature, and a film thickness suitably in the range of a well-known technique. Examples of the positive quarter-wave retardation film include Arton manufactured by JSR Corporation, ZEONOR manufactured by Zeon Corporation, and Pure Ace WR manufactured by Teijin Chemicals Limited.
A substantially quarter-wave retardation film can be obtained by application of production of a positive quarter-wave retardation film. For example, by increasing the draw ratio, increasing the difference between the longitudinal and lateral stretches, etc., the 550 nm phase difference moves in the increasing direction, reducing the draw ratio, or the difference between the longitudinal and lateral stretches. The phase difference of 550 nm moves in the direction of decreasing by decreasing.

The thickness of the base film is preferably in the range of 4 to 200 μm, more preferably 4 to 170 μm, from the viewpoint of strength, processability, and thinning of the front plate and display device using the surface protective film of the present invention. 135 micrometers is still more preferable, and 4-100 micrometers is still more preferable.
When the substrate film is a high retardation film, the thickness is preferably 60 to 200 μm, more preferably 60 to 170 μm, and still more preferably 60 to 135 μm.
Moreover, when a base film is a 1/4 wavelength phase difference film, 4-200 micrometers is preferable, 4-135 micrometers is more preferable, and 4-70 micrometers is still more preferable.

  There is also a problem that it is difficult to add an ultraviolet absorbent to the polyester resin film preferably used as the base film of the surface protective film of the present invention. Therefore, the surface protective film of the present invention has a configuration in which an ultraviolet absorber is added to the surface protective layer described below.

<Surface protective layer>
The surface protective layer is a cured ionizing radiation curable resin composition comprising a resin component containing an ionizing radiation curable compound, an ultraviolet absorber having a molecular weight of less than 1,000, and an ultraviolet absorber having a weight average molecular weight of 1,000 or more. It is a thing. That is, the ionizing radiation curable resin composition includes at least a resin component containing an ionizing radiation curable compound, an ultraviolet absorber having a molecular weight of less than 1,000, and an ultraviolet absorber having a weight average molecular weight of 1,000 or more. . The ionizing radiation curable resin composition may contain a resin component such as a thermoplastic resin other than the ionizing radiation curable compound as described later.
The ionizing radiation curable resin composition is a resin composition that is cured by irradiating with ionizing radiation. As the ionizing radiation, an electromagnetic wave or a charged particle beam having an energy quantum capable of polymerizing or crosslinking molecules, for example, In addition to ultraviolet rays (UV) or electron beams (EB), electromagnetic waves such as X rays and γ rays, and charged particle beams such as α rays and ion rays are also used.

(Ionizing radiation curable compounds)
The ionizing radiation curable compound contained in the ionizing radiation curable resin composition can be appropriately selected from conventionally used polymerizable monomers and polymerizable oligomers or prepolymers. From the viewpoint of improving the scratch resistance, a polymerizable monomer is preferable.
As the polymerizable monomer, a (meth) acrylate monomer having a radical polymerizable unsaturated group in the molecule is suitable, and among them, a polyfunctional (meth) acrylate monomer is preferred. The polyfunctional (meth) acrylate monomer is not particularly limited as long as it is a (meth) acrylate monomer having two or more ethylenically unsaturated bonds in the molecule. For example, diethylene glycol di (meth) acrylate, propylene glycol di ( (Meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane ethylene oxide tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate Etc. are preferable. The (meth) acrylate may be modified with a part of the molecular skeleton, modified with ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, alkyl, cyclic alkyl, aromatic, bisphenol, etc. Can also be used.
One of these (meth) acrylate monomers may be used alone, or two or more thereof may be used in combination.
The number of functional groups of the polyfunctional (meth) acrylate monomer is not particularly limited as long as it is 2 or more. However, from the viewpoint of improving the curability of the ionizing radiation curable resin composition and the scratch resistance of the surface protective layer, 2-8. Is more preferable, 2-6 is more preferable, and 3-6 is more preferable.
From the viewpoint of improving the scratch resistance of the surface protective layer, the molecular weight of the polyfunctional (meth) acrylate monomer is preferably less than 1,000, and more preferably 200 to 800.

  In the present invention, from the viewpoint of improving the curability of the ionizing radiation curable resin composition and the scratch resistance of the surface protective layer, it is preferable to use a polyfunctional polymerizable monomer as the ionizing radiation curable compound. It is more preferable to use a (meth) acrylate monomer. In addition, from the same viewpoint as described above, the content of the polyfunctional (meth) acrylate monomer in the ionizing radiation curable compound is preferably 50 to 100% by mass, more preferably 65 to 100% by mass, and 70 to 100% by mass. Is more preferable.

The ionizing radiation curable compound is preferably composed only of the polymerizable monomer from the viewpoint of improving the curability of the ionizing radiation curable resin composition and the scratch resistance of the surface protective layer, but is also used in combination with the polymerizable oligomer. May be.
As the polymerizable oligomer, a polyfunctional (meth) acrylate oligomer having two or more radically polymerizable unsaturated groups in the molecule is preferably used. Examples of the (meth) acrylate oligomer include urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, melamine (meth) acrylate, polyfluoroalkyl (meth) acrylate, and silicone (meth) acrylate. It is done. The (meth) acrylate may be modified with a part of the molecular skeleton, modified with ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, alkyl, cyclic alkyl, aromatic, bisphenol, etc. Can also be used. These may be used alone or in combination of two or more.

The number of functional groups of the polyfunctional (meth) acrylate oligomer is not particularly limited as long as it is 2 or more. However, from the viewpoint of improving the curability of the ionizing radiation curable resin composition and the scratch resistance of the surface protective layer, 2-8. Is preferable, and more preferably 2 to 6.
The weight average molecular weight of the polyfunctional (meth) acrylate oligomer is preferably 1,000 to 20,000, and more preferably 1,000 to 15,000. In addition, in this specification, the said weight average molecular weight is the value calculated | required by polystyrene conversion by gel permeation chromatography (GPC).

The ionizing radiation curable resin composition may further contain a thermoplastic resin as another resin component. This is because by using the electron radiation curable compound and the thermoplastic resin in combination, it is possible to effectively prevent the adhesion with the base film or the like and the defect of the coating film.
Examples of the thermoplastic resin include styrene resin, (meth) acrylic resin, polyolefin resin, vinyl acetate resin, vinyl ether resin, halogen-containing resin, polycarbonate resin, polyester resin, polyamide resin, nylon, cellulose resin, silicone resin, and polyurethane. Preferable examples include thermoplastic resins such as resins and copolymers, and mixed resins thereof. These resins are preferably amorphous and soluble in a solvent. In particular, from the viewpoint of film forming property, transparency, weather resistance, styrene resin, (meth) acrylic resin, polyolefin resin, polyester resin, cellulose resin, etc. are preferable, (meth) acrylic resin is more preferable, and polymethyl methacrylate is preferable. Further preferred.
These thermoplastic resins preferably have no reactive functional group in the molecule. This is because if the reactive functional group is included in the molecule, the amount of cure shrinkage increases, and the adhesion of the surface protective layer to the base film may be reduced. Reactive groups include functional groups having unsaturated double bonds such as acryloyl groups and vinyl groups, cyclic ether groups such as epoxy rings and oxetane rings, ring-opening polymerizable groups such as lactone rings, and isocyanates that form urethane. Groups and the like. In addition, these reactive functional groups may be contained as long as the adhesiveness to the base film of the surface protective layer is not impaired.

When the ionizing radiation curable compound is an ultraviolet curable compound, the ionizing radiation curable resin composition preferably contains additives such as a photopolymerization initiator and a photopolymerization accelerator.
Examples of the photopolymerization initiator include acetophenone, α-hydroxyalkylphenone, acylphosphine oxide, benzophenone, Michler ketone, benzoin, benzylmethyl ketal, benzoylbenzoate, α-acyl oxime ester, thioxanthone and the like. These can be used alone or in combination of two or more. When a photopolymerization initiator is used, the content of the photopolymerization initiator is preferably 0.1 to 20 parts by mass, more preferably 1 to 15 parts by mass with respect to 100 parts by mass of the ionizing radiation curable compound. .
Further, the photopolymerization accelerator can reduce the polymerization obstacle due to air at the time of curing and increase the curing speed. For example, p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester, and the like. Can be mentioned. These can be used alone or in combination of two or more.

(UV absorber)
The ionizing radiation curable resin composition used in the present invention has an ultraviolet absorber (hereinafter referred to as “low molecular weight type”) having a molecular weight of less than 1,000 in order to impart an ultraviolet cut function while suppressing coloring of the surface protective layer of the surface protective film. And a UV absorber having a weight average molecular weight of 1,000 or more (hereinafter also referred to as “polymer UV absorber”).
Low molecular weight UV absorbers can be used in a relatively small amount because of their high UV absorption ability, but many have strong absorption even in the visible light region, particularly near the wavelength of 390 to 420 nm, and the surface protective layer is colored yellow. It's easy to do. On the other hand, the high-molecular ultraviolet absorber is less colored, but has a lower UV-absorbing ability than the low-molecular ultraviolet absorber, and if added in a large amount to compensate for this, there is a problem that the hardness of the surface protective layer decreases. . In the present invention, a combination of a low molecular weight UV absorber and a high molecular weight UV absorber in an ionizing radiation curable resin composition has a high UV blocking function, is less colored, and is a member such as a polarizer. A surface protective film having sufficient scratch resistance to protect the surface of the film can be obtained.

[Low molecular weight UV absorber]
The low molecular weight ultraviolet absorber used in the present invention has a molecular weight of less than 1,000 and satisfies the following formula (1).
(Transmittance at a wavelength of 390 nm / Transmittance at a wavelength of 380 nm) ≧ 1.40 (1)
The transmittance ratio represented by the above formula (1) represents the contrast of the transmittance in the vicinity of the boundary between the visible light region and the ultraviolet light region, and the larger the value, the more preferable. That is, at a wavelength of 390 nm on the short wavelength side of the visible light region, a higher transmittance is preferable because of less visible coloration, while at a wavelength of 380 nm on the long wavelength side of the ultraviolet light region, the transmittance is lower. Is preferable because of its high ultraviolet absorption ability.
When the transmittance ratio represented by the above formula (1) of the low molecular weight ultraviolet absorber is less than 1.40, the obtained surface protective film has a high ultraviolet cut function but is markedly colored or is not colored. The UV cut function is low, and the UV cut function and low colorability cannot be achieved at the same time. From the viewpoint of achieving both the UV-cutting function and the low colorability of the surface protective film, the transmittance ratio represented by the above formula (1) is preferably 1.50 or more, more preferably 1.55 or more, and even more preferably 1. .60 or more.
The transmittance ratio represented by the formula (1) of the low molecular weight ultraviolet absorber can be measured as follows. A low molecular weight ultraviolet absorber is dissolved to a concentration of 6 parts by mass with respect to 100 parts by mass of a polyfunctional (meth) acrylate monomer (pentaerythritol triacrylate) having no absorption near a wavelength of 380 to 750 nm, and further photopolymerization is performed. An initiator is added and applied to a glass substrate or the like having no absorption near a wavelength of 350 to 750 nm to form a coating film having a dry thickness of 4 to 5 μm. Next, the coating film is irradiated with ultraviolet rays to form a uniform cured film having a thickness of 4 to 5 μm, and transmittances at wavelengths of 380 nm and 390 nm are measured with an ultraviolet-visible spectrophotometer using the obtained sample. More specifically, the transmittance ratio can be measured by the method described in Examples.

Moreover, it is preferable that the low molecular weight ultraviolet absorber has less absorption in the visible light region having a wavelength of more than 390 nm and not more than 750 nm from the viewpoint of low colorability. Specifically, it is preferable that the low molecular weight ultraviolet absorber further satisfies the following formula (1a) from the viewpoint of achieving both the ultraviolet cut function of the surface protective film and the low colorability in the visible light region. . The transmittance ratio represented by the following formula (1a) is more preferably 1.80 or more, and further preferably 2.00 or more.
(Transmission at wavelength 580 nm / Transmission at wavelength 380 nm) ≧ 1.50 (1a)
The transmittance ratio represented by the formula (1a) of the low molecular weight ultraviolet absorber is determined by measuring the transmittance at wavelengths of 380 nm and 580 nm by the same method as in the case of the formula (1).

The low molecular weight ultraviolet absorber used in the present invention is not particularly limited as long as it satisfies at least the transmittance ratio represented by the above formula (1). For example, benzophenone compounds, benzotriazole compounds, triazine compounds Benzoxazine compounds, salicylic acid ester compounds, cyanoacrylate compounds, and the like.
Among these, from the viewpoint of ultraviolet absorption, at least one selected from benzophenone compounds, benzotriazole compounds, and triazine compounds is preferable. From the viewpoint of ultraviolet absorption, solubility in ionizing radiation curable compounds, and the like, 1 or more types chosen from a triazole type compound and a triazine type compound are more preferable.

  Preferred low molecular weight ultraviolet absorbers used in the present invention include benzotriazole compounds represented by the following general formula (1) or (2) and triazine compounds represented by the following general formula (3). It is done.

(In General Formulas (1) and (2), R ^{1 to} R ⁴ are each independently substituted with a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 18 carbon atoms, a hydroxyl group, or an alkyl group having 1 to 18 carbon atoms. Benzyl group or (meth) acryloyloxyalkyl group which may be present.

(In General Formula (3), R ^{5 to} R ⁹ each independently represent a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 18 carbon atoms, or an alkyloxy group having 1 to 18 carbon atoms.)

Among the above, the benzotriazole-based compound is more preferably represented by the general formula (1), and R ¹ and R ^{2 in} the general formula (1) are each independently an alkyl group having 1 to 18 carbon atoms. Is more preferable.

  The molecular weight of the low molecular weight UV absorber is less than 1,000 from the viewpoint of UV absorbing ability, and from the viewpoint of UV absorbing ability and solubility in the resin composition, the molecular weight is preferably 200 to 900, and 300 to 800. More preferred. Since the ultraviolet absorber having the above molecular weight range has a high ultraviolet absorbing ability, it exhibits a sufficient ultraviolet absorbing property even if the amount used is small. Therefore, by using a low molecular weight ultraviolet absorbent, it is possible to obtain a surface protective film having an excellent ultraviolet cut effect without impairing scratch resistance.

  Examples of commercially available low molecular weight ultraviolet absorbers that can be used in the present invention include KEMISORB 71D (Kemipro Kasei Co., Ltd., benzotriazole-based compound represented by the following structural formula (1-1)), JF-80 (Johoku Chemical Industry). Manufactured by Co., Ltd., benzotriazole-based compound represented by the following structural formula (2-1)), Tinuvin 477 (manufactured by BASF, triazine-based compound included in the range of general formula (3)), Tinuvin 460 (manufactured by BASF, the following structure) And a triazine compound represented by the formula (3-1). All of these satisfy the transmittance ratio represented by the above formula (1).

[Polymer type UV absorber]
The polymer type ultraviolet absorber used in the present invention has a weight average molecular weight of 1,000 or more, and preferably satisfies the following formula (2) from the viewpoint of achieving both the ultraviolet cut function and the low colorability of the surface protective film. It is more preferable to satisfy the following formulas (2) and (2a).
(Transmittance at a wavelength of 390 nm / Transmittance at a wavelength of 380 nm) ≧ 2.00 (2)
(Transmission at wavelength 580 nm / Transmission at wavelength 380 nm) ≧ 3.00 (2a)
The transmittance ratio represented by the above formula (2) is more preferably 2.50 or more, and further preferably 3.00 or more. Further, the transmittance ratio represented by the above formula (2a) is more preferably 3.50 or more, and further preferably 4.00 or more.
The transmittance ratio represented by the formulas (2) and (2a) of the polymer type ultraviolet absorber is, for example, a dry thickness 4 of the polymer type ultraviolet absorber on a glass substrate or the like that does not absorb near a wavelength of 350 to 750 nm. It is calculated | required by forming a ~ 5 micrometer coating film and measuring the transmittance | permeability of wavelength 380nm, 390nm, and 580nm with an ultraviolet visible spectrophotometer. More specifically, the transmittance ratio can be measured by the method described in Examples.
Moreover, it is preferable that the polymer type ultraviolet absorber has less absorption in the visible light region having a wavelength of more than 390 nm and not more than 750 nm from the viewpoint of low colorability in the visible light region. More specifically, the minimum value of the transmittance in the wavelength range of more than 390 nm and less than 750 nm measured by the same method as the transmittance ratio represented by the formula (2) is 50% or more in terms of thickness of 4 to 5 μm. It is preferable.

  Examples of the polymer type ultraviolet absorber include a polymer having an ultraviolet absorbing group, and preferred examples include a copolymer of an ultraviolet absorbing monomer and another monomer. Examples of the ultraviolet absorbing monomer include compounds containing a benzotriazole skeleton, a benzophenone skeleton, a triazine skeleton, a benzoxazine skeleton, etc. in the ester substituent of (meth) acrylic acid ester. Moreover, as said other monomer, what is necessary is just a monomer copolymerizable with the said ultraviolet-absorbing monomer, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, Examples include alkyl (meth) acrylates such as butyl (meth) acrylate, and hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and hydroxybutyl (meth) acrylate. Species or a combination of two or more can be used.

  As the polymer type ultraviolet absorber used in the present invention, an ultraviolet absorber having a benzotriazole group is preferable. As this ultraviolet absorber, the ultraviolet absorber represented by following General formula (4) is mentioned, for example.

(In General Formula (4), R ^{10 to} R ¹² each independently represents a hydrogen atom or a methyl group. R ¹³ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a benzyl group, or an aryl group. R ¹⁴ and R ¹⁵ each independently represents an alkylene group having 1 to 3 carbon atoms, a, b, and c each represents a molar ratio of each structural unit represented by the general formula (4), and a + b + c = 1. A and b represent a number of 0 or more, and c represents a number other than 0.)
In the general formula (4), c is preferably 0.3 or more, more preferably 0.5 or more, and a preferable upper limit is 0.8 from the viewpoint of ultraviolet absorbing ability.

  The polymer type ultraviolet absorber used in the present invention has a weight average molecular weight of 1,000 or more, and from the viewpoint of ultraviolet absorption ability and solubility in the resin composition, the weight average molecular weight is preferably 150,000 or less, 000-100,000 are more preferable, and 5,000-80,000 are still more preferable. Since the ultraviolet absorber having the above molecular weight range is less colored, a surface protective film with less coloring can be obtained even if the amount used is increased in order to provide an ultraviolet cut function. A weight average molecular weight is the value calculated | required by polystyrene conversion by GPC.

  Examples of commercially available polymer ultraviolet absorbers that can be used in the present invention include Vanaresin UVA-5080 (manufactured by Shin-Nakamura Chemical Co., Ltd.), UVA1935LH (manufactured by BASF), and the like (all of which have a benzotriazole group). It is done.

The content of the resin component containing the ionizing radiation curable compound and the ultraviolet absorber in the ionizing radiation curable resin composition is 50 to 90% by mass of the resin component containing the ionizing radiation curable compound, and the weight average molecular weight is 1,000. It is preferable that 3 to 9 parts by mass of an ultraviolet absorber having a molecular weight of less than 1,000 is included with respect to 100 parts by mass of the mixture composed of 10 to 50% by mass of the above ultraviolet absorber. The “resin component” here includes an ionizing radiation curable compound and a resin (such as the thermoplastic resin described above) other than the ultraviolet absorber.
If the content of the resin component containing the ionizing radiation curable compound and the polymer type ultraviolet absorber in the above-mentioned mixture is within the above range, the UV cut function is provided while maintaining sufficient scratch resistance as a surface protective layer. it can. Moreover, if content of a low molecular weight type ultraviolet absorber is the said range, it can be set as a surface protection layer with little coloring, providing an ultraviolet cut function.
In the above mixture, the content of the resin component containing the ionizing radiation curable compound is more preferably 60 to 85% by mass, and still more preferably 60 to 80% by mass, from the viewpoint of the scratch resistance of the surface protective layer and the ultraviolet cut function. More preferably, it is 65-80 mass%. Further, the content of the low molecular weight ultraviolet absorber in the ionizing radiation curable resin composition is more preferably 4 to 8 parts by mass, still more preferably 5 to 8 parts by mass with respect to 100 parts by mass of the mixture.
In addition, the content of the ionizing radiation curable compound in the resin component is preferably 50% by mass or more, more preferably 70 to 100% by mass from the viewpoint of maintaining sufficient scratch resistance as a surface protective layer. Preferably it is 85-100 mass%.

(Light reflecting fine particles)
The ionizing radiation curable resin composition may further contain light reflecting fine particles as desired. Since the light-reflecting fine particles do not transmit ultraviolet rays, if the surface protective layer contains the light-reflecting fine particles, the ultraviolet ray cutting function is further improved.
Such light-reflective fine particles are not particularly limited, and for example, metal fine particles, metal oxide fine particles, and coating fine particles in which a light-reflective coating layer is formed on the surface of core fine particles are preferably used.
Examples of the metal constituting the metal fine particles include Au, Ag, Cu, Al, Fe, Ni, Pd, and Pt.
Examples of the metal oxide constituting the metal oxide fine particles include tin oxide (SnO ₂ ), antimony oxide (Sb ₂ O ₅ ), antimony tin oxide (ATO), indium tin oxide (ITO), and aluminum zinc oxide. (AZO), fluorinated tin oxide (FTO), ZnO and the like.
Examples of the coating fine particles include conventionally known fine particles having a configuration in which a light-reflective coating layer is formed on the surface of the core fine particles. The core fine particles are not particularly limited, and examples thereof include inorganic fine particles such as colloidal silica fine particles and silicon oxide fine particles, fine polymer particles such as fluororesin fine particles, acrylic resin particles, and silicone resin particles, and fine particles such as organic inorganic composite particles. . Moreover, it does not specifically limit as a material which comprises a light reflection coating layer, For example, the metal mentioned above or these alloys, the metal oxide mentioned above, etc. are mentioned.

The light-reflecting fine particles used in the present invention may be conductive fine particles having conductivity. The conductive fine particles are fine particles that play a role of establishing conduction between the surface protective layer containing the conductive fine particles and another conductive layer. Examples of the “other conductive layer” include an antistatic layer described later. That is, a surface protective layer containing conductive fine particles (hereinafter also referred to as “conductive surface protective layer”) is preferably provided when an antistatic layer described later is provided between the base film and the surface protective layer.
Such conductive fine particles are not particularly limited, and examples thereof include those similar to the light reflective fine particles. In addition, from the viewpoint of improving conduction from another conductive layer such as an antistatic layer, the conductive fine particles are preferably gold-plated fine particles.

The average particle diameter of the light-reflecting fine particles is preferably 1 to 15 μm, more preferably 2 to 10 μm, and still more preferably 2 to 8 μm. If the average particle diameter is 1 μm or more, the scratch resistance of the surface protective layer is not lowered, and if it is 15 μm or less, the thickness of the surface protective layer can be reduced and the thickness can be reduced.
In the present specification, the “thickness of the surface protective layer” in the case of the surface protective layer containing the light-reflecting fine particles means the thickness of the portion excluding the fine particles protruding from the layer (x in FIG. 1).

  When the light-reflecting fine particles are conductive fine particles, the average particle size is the thickness of the surface protective layer in order to establish conduction between the surface of the conductive surface protective layer and another conductive layer such as an antistatic layer. It is preferable that the size is equal to or larger than the above. Specifically, the average particle diameter of the conductive fine particles is preferably 50 to 150% with respect to the thickness of the surface protective layer, more preferably 70 to 120%, and still more preferably 85 to 115%. preferable. By making the average particle diameter of the conductive fine particles with respect to the thickness of the surface protective layer 50% or more, the conduction from the antistatic layer can be improved, and by making it 150% or less, the conductive fine particles fall off from the surface protective layer. Can be prevented.

The light-reflecting fine particles may be present in the surface protective layer in any state of non-aggregated particles and aggregated particles. Here, the average particle diameter of the light-reflecting fine particles can be calculated by the following operations (1) to (3).
(1) The cross section of a surface protection film is imaged with a transmission type | mold microscope (TEM) or a scanning transmission electron microscope (STEM). The acceleration voltage of TEM or STEM is preferably 10 kv to 30 kV, and the magnification is preferably 50,000 to 300,000 times.
(2) Ten arbitrary particles are extracted from the observed image, the major axis and minor axis of each particle are measured, and the particle diameter of each particle is calculated from the average of the major axis and minor axis. The major axis is the longest diameter on the screen of individual particles. The minor axis is a distance between two points where a line segment perpendicular to the midpoint of the line segment constituting the major axis is drawn and the perpendicular line segment intersects the particle.
(3) The same operation is performed five times on the observation image of another screen of the same sample, and the value obtained from the number average of the particle diameters for a total of 50 particles is taken as the average particle diameter of the particles.

  The content of the light-reflecting fine particles is 0 with respect to 100 parts by mass of the total amount of the resin component containing the ionizing radiation-curable compound in the ionizing radiation-curable resin composition and the ultraviolet absorber having a weight average molecular weight of 1,000 or more. It is preferable that it is 0.5-4.0 mass parts, and it is more preferable that it is 0.5-3.0 mass parts. When the content of the light-reflecting fine particles is 0.5 parts by mass or more, an ultraviolet cut function can be provided. When the light-reflecting fine particles are conductive fine particles, a conductive layer such as an antistatic layer to be described later The conduction from can be improved. Moreover, the fall of the film property of a surface protective layer and abrasion resistance can be prevented by making this content into 4.0 mass parts or less.

  In the ionizing radiation curable resin composition, as other various additional components, fillers such as antiwear agents, matting agents, scratch-resistant fillers, mold release agents, dispersants, leveling agents, hindered amine light stabilizers (HALS) ) And the like.

(Method for forming surface protective layer)
The surface protective layer is coated on the base film with an ionizing radiation curable resin composition having a desired thickness after curing, and after drying as necessary, is cured by irradiating with ionizing radiation. Can be formed. When providing other layers such as an antistatic layer, which will be described later, on the base film, apply an ionizing radiation curable resin composition on the layer, and dry and cure in the same manner to form a surface protective layer. That's fine.

For example, the ionizing radiation curable compound, the ultraviolet absorber, and the light-reflecting fine particles used as necessary, and other various additives are uniformly mixed at a predetermined ratio, respectively, from the ionizing radiation curable resin composition A coating solution is prepared. The coating solution prepared in this way is coated on the base film or the layer provided on the base film, die coat, bar coat, roll coat, slit coat, slit reverse coat, reverse roll coat, gravure coat The uncured resin layer is formed by applying, for example, and drying as necessary.
Next, the uncured resin layer is cured by irradiating the uncured resin layer with ionizing radiation such as an electron beam or ultraviolet rays. Here, when an electron beam is used as the ionizing radiation, the acceleration voltage can be appropriately selected according to the resin used and the thickness of the layer, but the uncured resin layer is usually cured at an acceleration voltage of about 70 to 300 kV. preferable.
When ultraviolet rays are used as the ionizing radiation, those containing ultraviolet rays having a wavelength of 190 to 380 nm are usually emitted. There is no restriction | limiting in particular as an ultraviolet-ray source, For example, a high pressure mercury lamp, a low pressure mercury lamp, a metal halide lamp, a carbon arc lamp, etc. are used.

  The thickness of the surface protective layer can be appropriately selected according to the use and required characteristics of the surface protective film, but from the viewpoint of abrasion resistance, processability, and thinning of the display device using the surface protective film of the present invention, 1 -30 μm is preferable, 2-20 μm is more preferable, and 2-10 μm is still more preferable. The thickness of the surface protective layer can be calculated, for example, by measuring the thickness at 20 locations from a cross-sectional image taken using a scanning transmission electron microscope (STEM) and calculating the average value of the 20 locations. The acceleration voltage of STEM is preferably 10 kv to 30 kV, and the observation magnification of STEM is preferably 1000 to 7000 times.

<Antistatic layer>
The surface protective film of the present invention only needs to have at least a base film and a surface protective layer. However, particularly when used for an in-cell touch panel, the antistatic is further provided between the base film and the surface protective layer. It is preferable to have a layer.
In the in-cell touch panel, the antistatic layer has an alternative role to the touch panel that has been working as a conductive member in a conventional external type or on-cell type. When a surface protective film having an antistatic layer is used, the antistatic layer is positioned closer to the viewer than the liquid crystal element, so that static electricity generated when the touch panel is touched can be released and the liquid crystal screen Can be partially clouded. In addition, when a front plate in which a surface protective film, a polarizer, and a retardation plate are laminated in order, the conductive surface protective layer and the antistatic layer are located on the outermost surface. The grounding treatment on the surface can be easily performed.

The antistatic layer is formed from a resin composition for forming an antistatic layer containing a conductive agent and, if necessary, a binder resin and a diluting solvent.
Examples of the conductive agent include ion conductive conductive agents such as quaternary ammonium salts and lithium salts, and electronic conductive conductive agents such as metal fine particles, metal oxide fine particles, carbon nanotubes, coating fine particles, and polyethylene dioxythiophene particles. Therefore, an electron conductive type conductive agent that is not easily affected by humidity is preferably used. As the metal fine particles, metal oxide fine particles, and coating fine particles, the same conductive fine particles as those described above are used. In addition, among the electron conductive type conductive agents, it is preferable to include one or more selected from metal fine particles and metal oxide fine particles from the viewpoint of good long-term storage, heat resistance, moist heat resistance, and light resistance. An oxide (ATO) is more preferable.

The electron conductive conductive agent preferably has an average particle size of 6 to 40 nm. By setting the thickness to 6 nm or more, the electron-conducting conductive agents can easily come into contact with each other in the antistatic layer. Therefore, the addition amount of the conductive agent for imparting sufficient conductivity can be suppressed, and the thickness should be 40 nm or less. Thus, it is possible to prevent the transparency and adhesion between other layers from being impaired. The more preferable lower limit of the average particle diameter of the electron conduction type conductive agent is 7 nm, and the more preferable upper limit is 20 nm. In addition, the average particle diameter of an electron conduction type conductive agent can be calculated by the following operations (1) to (3).
(1) The cross section of the optical sheet of the present invention is imaged with TEM or STEM. The acceleration voltage of TEM or STEM is preferably 10 kv to 30 kV, and the magnification is preferably 50,000 to 300,000 times.
(2) Ten arbitrary particles are extracted from the observed image, the major axis and minor axis of each particle are measured, and the particle diameter of each particle is calculated from the average of the major axis and minor axis. The major axis is the longest diameter on the screen of individual particles. The minor axis is a distance between two points where a line segment perpendicular to the midpoint of the line segment constituting the major axis is drawn and the perpendicular line segment intersects the particle.
(3) The same operation is performed five times on the observation image of another screen of the same sample, and the value obtained from the number average of the particle diameters for a total of 50 particles is taken as the average particle diameter of the particles.

  The electron conduction type conductive agent is preferably chain-like or needle-like. The electron conductive conductive agent having such a shape can reduce the fluctuation of the surface resistivity of the antistatic layer even when the antistatic layer is somewhat deformed (curing shrinkage or expansion / contraction due to temperature and humidity). it can.

The content of the electron conductive conductive agent in the antistatic layer is appropriately adjusted according to the type, shape, size, and the like of the electron conductive conductive agent to be used. For example, with respect to 100 parts by mass of the binder resin described later 100 to 400 parts by mass is preferable. By setting it as 100 parts by mass or more, the surface resistivity of the antistatic layer can be easily reduced to 2.0 × 10 ⁹ Ω / □ or less, and by setting it to 400 parts by mass or less, the surface resistivity of the antistatic layer is 1. It can be easily set to 0 × 10 ⁸ Ω / □ or more.
In addition, the more preferable minimum of content of an electron-conduction type electrically conductive agent is 150 mass parts, and a more preferable upper limit is 350 mass parts.

Examples of the binder resin include thermoplastic resins, thermosetting resins, and ionizing radiation curable resins, which can be used in appropriate combination. The binder resin may have adhesiveness, and when it has adhesiveness, it can be bonded to the in-cell touch panel liquid crystal element without forming an additional adhesive layer. Among binder resins, thermoplastic resin can hardly change the surface resistivity due to deformation of the antistatic layer (curing shrinkage or expansion / contraction due to temperature and humidity), and provides stability over time to the surface resistivity of the antistatic layer. It is preferable in that it can be performed.
The thermoplastic resin preferably has no reactive functional group in the molecule. If the molecule has a reactive functional group, the reactive functional group may react to cause curing shrinkage in the antistatic layer, thereby changing the surface resistivity. Reactive groups include functional groups having unsaturated double bonds such as acryloyl groups and vinyl groups, cyclic ether groups such as epoxy rings and oxetane rings, ring-opening polymerizable groups such as lactone rings, and isocyanates that form urethane. Groups and the like. These reactive functional groups may be included as long as they do not cause the surface resistivity to change due to curing shrinkage in the antistatic layer.

  The thermoplastic resin preferably has a side chain. The thermoplastic resin having a side chain can be made to have excellent surface resistivity stability with time because the side chain is sterically hindered and hardly moves in the antistatic layer. The side chain may have any structure, but preferably does not have the above-described reactive functional group in the molecule.

  The thermoplastic resin preferably has a glass transition temperature of 80 to 120 ° C. By making the glass transition temperature 80 ° C. or higher, destabilization of the surface resistivity due to the softness of the thermoplastic resin can be prevented, and by making the glass transition temperature 120 ° C. or lower, the thermoplastic resin is harder. It is possible to prevent a decrease in adhesion with other members. A more preferable lower limit of the glass transition temperature is 90 ° C., and a more preferable upper limit is 110 ° C.

  Specifically, polymethylmethacrylate is preferably used as the thermoplastic resin because it has a characteristic that it is easy to prevent bleed-out of the electron conductive conductive agent.

  The antistatic layer may be composed of two or more layers. Moreover, when providing an antistatic layer, it is preferable that a surface protective layer is the above-mentioned conductive surface protective layer. It is preferable that the antistatic layer has a two-layer structure or has an antistatic layer and a conductive surface protective layer, so that the surface resistivity is easily stabilized over time.

The surface resistivity of the antistatic layer is preferably 1.0 × 10 ^{8 to} 2.0 × 10 ⁹ Ω / □. If the surface resistivity is 1.0 × 10 ⁸ Ω / □ or more, when used in a capacitive touch panel, its operability is not adversely affected. In addition, when the surface resistivity is 2.0 × 10 ⁹ Ω / □ or less, the above-described white turbidity of the liquid crystal screen can be effectively prevented when used for an in-cell touch panel. In addition, when a surface protective film has an antistatic layer and a conductive surface protective layer, it is preferable that the surface resistivity measured on the conductive surface protective layer is in the above range.

The thickness of the antistatic layer is preferably from 0.1 to 10 μm, more preferably from 0.3 to 5 μm, still more preferably from 0.3 to 1 μm.
Further, from the viewpoint of the temporal stability of the surface resistivity, the thickness of the antistatic layer is preferably thinner than the thickness of the conductive surface protective layer described above, [Thickness of conductive surface protective layer] / [Antistatic layer] The ratio of the thickness] is preferably 1 to 300, more preferably 1 to 67, and still more preferably 2 to 33.
The thickness of the antistatic layer can be measured by the same method as that for the surface protective layer.

  The antistatic layer is formed by applying a composition for forming an antistatic layer and a composition for forming an antistatic layer comprising a solvent to be added, if necessary, on a base film, drying, and curing as necessary. can do.

<Configuration and characteristics of surface protective film>
Here, a surface protective film having an antistatic layer will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of the surface protective film of the present invention. A surface protective film 1 shown in FIG. 1 has a base film 2 and a surface protective layer 3. The surface protective layer 3 in FIG. 1 is a conductive surface protective layer containing conductive fine particles 31, and the surface protective layer is a cured product of an ionizing radiation curable resin composition containing conductive fine particles 31. Further, an antistatic layer 4 is provided between the base film 2 and the surface protective layer 3.

  The surface protective film having the configuration of FIG. 1 is particularly preferably used in an in-cell touch panel. As described above, in the in-cell touch panel, a phenomenon occurs in which the liquid crystal screen becomes cloudy due to static electricity generated when the touch panel is touched. Therefore, in order to prevent this, it is preferable to provide an antistatic layer at an arbitrary position on the front plate of the in-cell liquid crystal element in order to release the static electricity. Therefore, if the surface protective film of FIG. 1 is used for the front plate of the in-cell liquid crystal element, the front plate is provided with a surface protection characteristic and an antistatic function is provided to prevent white turbidity of the liquid crystal screen due to static electricity. Can do.

In this case, when the surface protective layer of the surface protective film having the antistatic layer 4 is the conductive surface protective layer 3, the conductive fine particles 31 in the conductive surface protective layer 3 are charged with the surface of the conductive surface protective layer 3. Conductivity with the prevention layer 4 can be taken, and static electricity that has reached the antistatic layer can be further flowed in the thickness direction to give a desired surface resistivity to the surface side (operator side) of the surface protection layer.
The antistatic layer has conductivity in the plane direction (X direction, Y direction) and the thickness direction (z direction), whereas the conductive surface protective layer has conductivity in the thickness direction. If it is enough. Therefore, the conductive surface protective layer has a different role in that it does not necessarily require surface conductivity.

  Moreover, in the surface protective film which has the antistatic layer 4, when the surface protective layer 3 has an ultraviolet cut function, it is advantageous at the point that deterioration by the external light ultraviolet-ray of the antistatic layer 4 can also be prevented.

  The surface protective film may further have a functional layer on the surface opposite to the base film. Examples of the functional layer include an antireflection layer, an antiglare layer, an anti-fingerprint layer, an antifouling layer, an abrasion resistant layer, and an antibacterial layer. These functional layers are preferably formed from a thermosetting resin composition or an ionizing radiation curable resin composition, and more preferably formed from an ionizing radiation curable resin composition.

The surface protective film of the present invention has a maximum transmittance at a wavelength of 380 nm in an ultraviolet light region of a wavelength of 200 to 380 nm, and a transmittance at a wavelength of 380 nm is preferably 10% or less, and preferably 8% or less. More preferred is 5% or less. If the transmittance at a wavelength of 380 nm is 10% or less, the ultraviolet cut function is good.
The transmittance of the surface protective film can be measured by an ultraviolet-visible spectrophotometer or the like, and specifically can be measured by the method described in the examples.

[Front plate]
The front plate of the display element of the present invention has at least a polarizing plate and the surface protective film of the present invention. The polarizing plate is composed of at least one phase difference plate and a polarizer. FIG. 2 is a cross-sectional view of an example of the front plate 100 of the present invention, which includes a retardation plate 51, a polarizer 52, and a surface protective film 1 in this order. By having such a configuration, it is possible to reduce the thickness while providing a necessary function as a front plate of the display element.
As shown in FIG. 2, the surface protective film 1 of the present invention is bonded to the polarizer 52 side of the polarizing plate 5, so that the surface protective film functions as a surface protective member of the front plate 100 and the polarizer 52. It also functions as a surface protective film. Here, an ultraviolet absorber is usually added to the TAC film that has been used only for the purpose of protecting the polarizer, and ultraviolet rays such as a polarizer provided on the inner side (display element side) than the TAC film. It also has a function of preventing deterioration. Since the surface protective film of the present invention also has an ultraviolet cut function, the surface protective film is used for pasting a TAC film used conventionally and other layers by using the surface protective film as a front plate of a display element. The pressure-sensitive adhesive layer can be reduced, and the front plate and the display device can be thinned.
In addition, the front plate of this invention can be formed by bonding together the surface at the side of the polarizer of a polarizing plate, and the base film side of a surface protection film.

<Phase difference plate>
The retardation plate has a configuration having at least a retardation layer. Examples of the retardation layer include a stretched film such as a stretched polycarbonate film, a stretched polyester film, and a stretched cyclic olefin film, and a layer containing a refractive index anisotropic material. In the former and latter modes, the latter mode is preferable from the viewpoint of retardation control and thinning.
A layer containing a refractive index anisotropic material (hereinafter sometimes referred to as an “anisotropic material-containing layer”) may be formed on the resin film even if it constitutes a retardation plate by itself. The structure which has an anisotropic material content layer may be sufficient.

The resins constituting the resin film include polyester resins, polyolefin resins, (meth) acrylic resins, polyurethane resins, polyether sulfone resins, polycarbonate resins, polysulfone resins, polyether resins, and polyethers. Examples include ketone-based resins, (meth) acrylonitrile-based resins, cycloolefin-based resins, and the like, and one or more of these can be used. Among these, cycloolefin resins are preferable from the viewpoints of dimensional stability and optical stability.
Examples of the refractive index anisotropic material include rod-like compounds, discotic compounds, and liquid crystal molecules.

When the refractive index anisotropic material is used, various types of retardation plates can be formed depending on the orientation direction of the refractive index anisotropic material.
For example, the optical axis of the refractive index anisotropic material is oriented in the normal direction of the anisotropic material-containing layer and has an extraordinary ray refractive index larger than the ordinary ray refractive index in the normal direction of the anisotropic material-containing layer. There is a so-called positive C plate.
In another aspect, the optical axis of the refractive index anisotropic material is parallel to the anisotropic material-containing layer and has an extraordinary ray refractive index larger than the ordinary ray refractive index in the in-plane direction of the anisotropic material-containing layer. A so-called positive A plate may be used.
Furthermore, by making the optical axis of the liquid crystal molecules parallel to the anisotropic material-containing layer and adopting a cholesteric orientation having a spiral structure in the normal direction, the anisotropic material-containing layer as a whole is more than the ordinary refractive index. A so-called negative C plate having a small extraordinary ray refractive index in the normal direction of the retardation layer may be used.
Furthermore, the discotic liquid crystal having negative birefringence anisotropy may be a negative A plate having its optical axis in the in-plane direction of the anisotropic material-containing layer.
Further, the anisotropic material-containing layer may be oblique to the layer, or may be a hybrid alignment plate whose angle changes in a direction perpendicular to the layer.
Such various types of retardation plates can be manufactured by, for example, a method described in JP-A-2009-053371.

The retardation plate may be composed of any one of the above-described positive or negative C plate, A plate, or hybrid alignment plate, but two or more of these one or a combination of two or more thereof. It may consist of the following plate. For example, when the liquid crystal element of the in-cell touch panel is a VA system, it is preferable to use a combination of a positive A plate and a negative C plate. In the case of an IPS system, the positive C plate is combined with a positive A plate or a biaxial plate. However, any combination can be used as long as the viewing angle can be compensated, and various combinations are conceivable and can be appropriately selected.
When the retardation plate is composed of two or more plates, from the viewpoint of thinning, one plate is used as a stretched film, and an anisotropic material-containing layer (other plate) is laminated on the stretched film. Embodiments are preferred.

  The thickness of the retardation plate is preferably 25 to 60 μm, and more preferably 25 to 30 μm. In addition, when the retardation plate is composed of two or more plates, by setting one plate as a stretched film and laminating an anisotropic material-containing layer (other plate) on the stretched film, It can be easily within the above thickness range.

<Polarizer>
As the polarizer, any polarizer may be used as long as it has a function of transmitting only light having a specific vibration direction. For example, a PVA film obtained by stretching a PVA film and dyeing it with iodine or a dichroic dye is used. Examples include polarizers, polyene polarizers such as PVA dehydrated products and polyvinyl chloride dehydrochlorinated products, reflective polarizers using cholesteric liquid crystals, and thin film crystal film polarizers. Among these, a PVA polarizer that exhibits adhesiveness with water and can adhere a phase difference plate or a surface protective film without providing an additional adhesive layer is preferable.

Examples of PVA polarizers include hydrophilic polymer films such as PVA films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films, as well as iodine and dichroic dyes. A uniaxially stretched product by adsorbing a chromatic substance can be mentioned. Among these, from the viewpoint of adhesiveness, a polarizer made of a dichroic substance such as a PVA film and iodine is preferably used.
The PVA resin constituting the PVA film is formed by saponifying polyvinyl acetate.
2-30 micrometers is preferable and, as for the thickness of a polarizer, 3-30 micrometers is more preferable.

  The front plate 100 of the present invention may have a surface protective material such as a cover glass or a surface protective film having a silicon-containing film on the surface protective film 1 side. Moreover, you may have a film and layer other than the above in the range which does not inhibit the effect of this invention. However, from the viewpoint of thickness reduction and transparency, the retardation plate, the polarizer, and the surface protective film are preferably laminated without any other layers. Here, “lamination without other layers” does not mean that the other layers are completely excluded. For example, it is not intended to exclude even a very thin layer such as an easy adhesion layer provided in advance on the base film.

  The thickness of the front plate of the present invention can be appropriately selected depending on the display device used and the layer structure. In the case of a front plate for an in-cell touch panel liquid crystal display element, it is preferably 90 to 800 μm, more preferably 90 to 500 μm, and still more preferably 90 to 350 μm.

The front plate of the present invention having the above-described configuration can be used as a front plate for various display elements. Especially, it is suitable as a front board of a liquid crystal display element, and using as a front board of an in-cell touch panel type liquid crystal display element is preferable.
The in-cell touch panel type liquid crystal display element is a liquid crystal element in which a liquid crystal is sandwiched between two glass substrates, and a touch panel function such as a resistance film type, a capacitance type, and an optical type is incorporated therein. Examples of the liquid crystal display method of the in-cell touch panel liquid crystal element include an IPS method, a VA method, a multi-domain method, an OCB method, an STN method, and a TSTN method.
In-cell touch panel type liquid crystal elements are described in, for example, Japanese Patent Application Laid-Open Nos. 2011-76602 and 2011-222009.

[Display device]
The display device of the present invention has the front plate of the present invention, and examples thereof include a liquid crystal display device. For example, an in-cell touch panel liquid crystal display device preferably exemplified as a display device of the present invention is formed by bonding the above-described surface of the front plate of the present invention on the in-cell touch panel type liquid crystal element.
The in-cell touch panel type liquid crystal element and the front plate can be bonded together via an adhesive layer, for example. For the adhesive layer, urethane-based, acrylic-based, polyester-based, epoxy-based, vinyl acetate-based, vinyl chloride / vinyl acetate copolymer, cellulose-based adhesive, and the like can be used. The thickness of the adhesive layer is about 10 to 25 μm.
As described above, the in-cell touch panel type liquid crystal display device of the present invention uses the front plate having the surface protective film of the present invention, and as described above, protects the polarizer which is a constituent member of the front plate and uses external light ultraviolet rays. In terms of being able to reduce the overall thickness while satisfying various necessary functions such as prevention of deterioration, prevention of Nizumura when observed with polarized sunglasses, prevention of cloudiness of the liquid crystal display screen due to generation of static electricity, etc. It is useful.

EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited at all by these examples.
In addition, evaluation of the surface protection film of an Example and a comparative example was performed as follows.

[Transmissivity of UV absorber]
The transmittance of the ultraviolet absorber having a molecular weight of less than 1,000 was measured as follows. To 100 parts by mass of pentaerythritol triacrylate (PETA), 6 parts by mass of an ultraviolet absorber having a molecular weight of less than 1,000 and 6 parts by mass of a photopolymerization initiator (BASF, Irgacure 184) are added and dissolved, and the coating solution Was prepared. This was uniformly applied onto a glass substrate and cured by irradiating 300 mJ / cm ^{2 with} ultraviolet rays to form a uniform cured film having a thickness of 4.5 μm. Subsequently, the transmittance | permeability of wavelength 380nm, 390nm, and 580nm of the obtained cured film was measured using the ultraviolet visible spectrophotometer "UVPC-2450" (made by Shimadzu Corporation).
In addition, the transmittance of the UV absorber having a weight average molecular weight of 1,000 or more was measured by applying the UV absorber uniformly on the glass substrate so as to have a thickness of 4.5 μm, and then measuring the UV-visible spectrophotometer “UVPC- 2450 "(manufactured by Shimadzu Corporation), transmittances at wavelengths of 380 nm, 390 nm, and 580 nm were measured.

[Transmissivity of surface protective film]
The transmittance | permeability in wavelength 380nm of the surface protection film produced in the Example and the comparative example was measured using the ultraviolet visible spectrophotometer "UVPC-2450" (made by Shimadzu Corporation).

[Colorability]
The colorability (yellowness) of the surface protective films prepared in Examples and Comparative Examples was measured by b * using a transmission method using an ultraviolet-visible spectrophotometer “UVPC-2450” (manufactured by Shimadzu Corporation), evaluated. The evaluation criteria are as follows. It shows that it is a favorable result with few yellowishness, so that the value of b * is small.
○: Transmission hue b * ≧ 1.0
X: Transmission hue b * <1.0

[Abrasion resistance]
The appearance after reciprocating 10 times with a load of 150 gf using steel wool (Nihon Steel Wool Co., Ltd., Bon Star # 0) was evaluated for the surface protective layers of the surface protective films prepared in Examples and Comparative Examples. . The evaluation criteria are as follows.
A: No scratches were observed on the surface, and the surface protective layer was not peeled off or whitened.
○: Although there were less than 10 scratches on the surface, the surface protective layer was not peeled off or whitened.
X: The surface was markedly scratched, and the surface protective layer was peeled off or whitened.

Example 1 (Production of surface protective film)
[Preparation of ionizing radiation curable resin composition]
Pentaerythritol triacrylate (Nippon Kayaku Co., Ltd., PET-30), a benzotriazole ultraviolet absorber having a weight average molecular weight of 40,000 to 60,000 (Shin Nakamura Chemical Co., Ltd.) Manufactured by UVA-5080), and a benzotriazole ultraviolet absorber having a molecular weight of 630 (manufactured by BASF, Tinuvin 460), so that the solid content of the three components becomes 70 parts by mass, 30 parts by mass, and 6 parts by mass in this order. It added in the ketone and stirred, and the solution a was obtained.
Next, 7 parts by mass of an α-hydroxyalkylphenone photopolymerization initiator (manufactured by BASF, Irgacure 184), acylphosphine oxide photopolymerization initiator (manufactured by BASF, lucillin TPO) with respect to 100 parts by mass of the solid content of the solution a 1.5 parts by mass was added and stirred to dissolve to prepare a solution b having a final solid content of 40% by mass.
Next, 0.4 parts by mass of a leveling agent (manufactured by DIC Corporation, Megaface RS71) was added to 100 parts by mass of the solid content of the solution b and stirred. Further, a gold-plated particle dispersion as light-reflecting fine particles (DNP Fine Chemical Co., Ltd., Bright dispersion, gold-plated particles average particle diameter 4.6 μm, solid content 25%) with respect to 100 parts by mass of the solid content of this solution Was added in a solid content and stirred to prepare an ionizing radiation curable resin composition.

[Formation of surface protective layer]
A biaxially stretched polyester film having a thickness of 50 μm (manufactured by Toyobo Co., Ltd., Cosmo Shine A4100) is coated with the above ionizing radiation curable resin composition by slit reverse coating so that the thickness after drying is 4.5 μm. After the obtained coating film was dried at 80 ° C. for 1 minute, the coating film was cured by irradiating with ultraviolet rays at an ultraviolet irradiation amount of 300 mJ / cm ² to form a surface protective layer having a thickness of 4.5 μm. Thus, a surface protective film was obtained.
Said evaluation was performed about the obtained surface protection film. The evaluation results are shown in Table 1.

Examples 2-6, Comparative Examples 1-4
Surface protective film in the same manner as in Example 1 except that the amount of the ionizing radiation curable compound in the ionizing radiation curable resin composition and the type and amount of the ultraviolet absorber were changed as shown in Table 1. Was prepared and evaluated. The evaluation results are shown in Table 1.

In addition, each component shown in Table 1 is as follows. The mass parts shown in Table 1 are mass parts in terms of pure content.
・ Ionizing radiation curable compound Pentaerythritol triacrylate (PETA); Nippon Kayaku Co., Ltd., PET-30
・ Ultraviolet absorber (A-1)
Benzotriazole-based high-molecular weight UV absorber; manufactured by Shin-Nakamura Chemical Co., Ltd., UVA-5080, weight average molecular weight 40,000-60,000, (transmittance at wavelength 390 nm / transmittance at wavelength 380 nm) 3.50 (Transmittance at wavelength 580 nm / Transmittance at wavelength 380 nm) 4.61
・ Ultraviolet absorber (A-2)
Benzotriazole-based high molecular weight UV absorber; manufactured by BASF, UVA1935LH, (transmittance at a wavelength of 390 nm / transmittance at a wavelength of 380 nm) 4.89, (transmittance at a wavelength of 580 nm / transmittance at a wavelength of 380 nm) 7.14
・ Ultraviolet absorber (B-1)
Triazine-based ultraviolet absorber; manufactured by BASF, Tinuvin 460, molecular weight 630, (transmittance at wavelength 390 nm / transmittance at wavelength 380 nm) 2.06, (transmittance at wavelength 580 nm / transmittance at wavelength 380 nm) 3.04
・ Ultraviolet absorber (B-2)
Benzotriazole ultraviolet absorber; JF-80 manufactured by Johoku Chemical Industry Co., Ltd., molecular weight 352, (transmittance at wavelength 390 nm / transmittance at wavelength 380 nm) 1.60, (transmittance at wavelength 580 nm / transmittance at wavelength 380 nm) Rate) 2.01
・ Ultraviolet absorber (b-1)
Benzotriazole-based ultraviolet absorber; JAST-500 manufactured by Johoku Chemical Industry Co., Ltd., molecular weight 500, (transmittance at a wavelength of 390 nm / transmittance at a wavelength of 380 nm) 1.30, (transmittance at a wavelength of 580 nm / transmittance at a wavelength of 380 nm) Rate) 1.46
Conductive fine particles Gold plated particles; DNP Fine Chemical Co., Ltd. Bright dispersion, average particle size of gold plated particles 4.6 μm, solid content 25%

  As is apparent from Table 1, the surface protective films of Examples 1 to 6 all had a high ultraviolet cut function, little coloring, and sufficient scratch resistance as a surface protective layer.

Example 7 (Production of surface protective film having antistatic layer)
[Preparation of composition for forming antistatic layer]
A thermoplastic resin (HRAG acrylic (25) MIBK, weight average molecular weight 70,000, glass transition temperature 100 ° C.) manufactured by DNP Fine Chemical Co., Ltd. is dissolved in methyl isobutyl ketone, and V3560 (manufactured by JGC Catalysts & Chemicals Co., Ltd.) ATO dispersion, ATO average particle diameter 8 nm) is added and stirred, and adjusted so that the final solid content is 10% by mass and the ratio of thermoplastic resin: ATO is 100: 300 (mass ratio), for forming an antistatic layer A composition was obtained.
[Formation of antistatic layer]
On the biaxially stretched polyester film (Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.) having a thickness of 50 μm, the antistatic layer forming composition is applied by slit reverse coating so that the dry coating thickness is 1 μm and dried. An antistatic layer was formed on the polyester film.
[Formation of surface protective layer]
On the antistatic layer, using the ionizing radiation curable resin composition prepared in Example 1, a surface protective layer was formed in the same manner as in Example 1 to obtain a surface protective film. When the evaluation was performed on the obtained surface protective film, the transmittance of the surface protective film at a wavelength of 380 nm was 7.25%, and both the colorability and the scratch resistance were good.

The surface protective film of the present invention has a high UV-cutting function, is less colored, and has sufficient scratch resistance to protect the surface of a member such as a polarizer. It is suitably used as a member constituting the front plate of the display device.
Moreover, since the surface protection film of this invention has the said performance, it has the function as a protective film of a polarizer used for the front plate installed on a display element, and a surface protection member. Therefore, by using the surface protective film of the present invention, the number of constituent members can be reduced, and the front plate and the display device can be thinned. In particular, the surface protective film of the present invention is suitably used for in-cell type liquid crystal display devices including in-cell touch panel liquid crystal display devices.

DESCRIPTION OF SYMBOLS 1 Surface protective film 2 Base film 3 Surface protective layer 31 Conductive fine particle 4 Antistatic layer 5 Polarizing plate 51 Phase difference plate 52 Polarizer 100 Front plate

Claims (19)

A surface protective film having a base film and a surface protective layer, wherein the surface protective layer comprises a resin component containing an ionizing radiation curable compound, an ultraviolet absorber having a molecular weight of less than 1,000, and a weight average molecular weight of 1, A surface protective film, which is a cured product of an ionizing radiation curable resin composition containing an ultraviolet absorber of 000 or more, and an ultraviolet absorber having a molecular weight of less than 1,000 satisfies the following formula (1).
(Transmittance at a wavelength of 390 nm / Transmittance at a wavelength of 380 nm) ≧ 1.40 (1)   The ionizing radiation curable resin composition comprises 100 parts by mass of a mixture composed of 50 to 90% by mass of a resin component containing an ionizing radiation curable compound and 10 to 50% by mass of an ultraviolet absorber having a weight average molecular weight of 1,000 or more. On the other hand, the surface protection film of Claim 1 containing 3-9 mass parts of ultraviolet absorbers with a molecular weight less than 1,000. The surface protection film according to claim 1 or 2, wherein the ultraviolet absorber having a weight average molecular weight of 1,000 or more satisfies the following formula (2).
(Transmittance at a wavelength of 390 nm / Transmittance at a wavelength of 380 nm) ≧ 2.00 (2)   The surface protective film according to claim 1, wherein the surface protective layer contains light-reflecting fine particles.   The surface protective film according to claim 4, wherein the light-reflecting fine particles are conductive fine particles.   The surface protective film according to claim 1, further comprising an antistatic layer between the base film and the surface protective layer.   The surface protection film according to claim 6, wherein the antistatic layer contains one or more selected from metal fine particles and metal oxide fine particles.   The surface protection film of any one of Claims 1-7 whose thickness of the said surface protection layer is 1-30 micrometers.   The surface protective film according to any one of claims 5 to 8, wherein an average particle diameter of the conductive fine particles is 50 to 150% with respect to a thickness of the surface protective layer.   The surface protection film according to any one of claims 1 to 9, wherein the ultraviolet absorber having a molecular weight of less than 1,000 is at least one selected from a benzotriazole-based compound and a triazine-based compound.   The surface protection film according to any one of claims 1 to 10, wherein the ultraviolet absorber having a weight average molecular weight of 1,000 or more has a weight average molecular weight of 3,000 to 100,000.   The surface protective film according to claim 1, wherein the ultraviolet absorber having a weight average molecular weight of 1,000 or more is an ultraviolet absorber having a benzotriazole group.   The surface protection film according to claim 1, wherein the base film is a film having optical anisotropy.   The surface protection film according to any one of claims 1 to 13, wherein the ionizing radiation curable compound comprises a polyfunctional (meth) acrylate monomer having a molecular weight of less than 1,000.   The surface protection film of any one of Claims 1-14 whose transmittance | permeability in wavelength 380nm is 10% or less.   The front plate of a display element which has a polarizing plate and the surface protection film of any one of Claims 1-15.   The front plate of a display element according to claim 16, wherein the display element is a liquid crystal display element.   The front plate of a display element according to claim 17, wherein the liquid crystal display element is an in-cell touch panel type liquid crystal display element.   A display device comprising the front plate according to claim 15.