JP2009040881A - Transparent crosslinked film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preferable single film for optical having no problem (heat-resistance, interface adhesion property, interference stripe and optical anisotropy) as an optical film using a PET film and a TAC film and by laminating of a hard coat layer for compensating it and a primer layer for laminating it, and having self-support property solving cost increase by multiple steps for giving function. <P>SOLUTION: In the transparent crosslinked film, a liquid active ray curable composition comprising 5-50 pts.wt. of a multi-functional acrylate and 0.5-10 pts.wt. of an oligohydroxyketone based initiator based on 100 pts.wt. of a vinyl ester composition is used. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transparent cross-linked film. More specifically, the film of the present invention has self-supporting properties, and is excellent in transparency suitable for an optical film, high glass transition temperature, surface hardness, and optical isotropy. The present invention relates to a transparent crosslinked film.

  Transparent plastic films such as polyester film (PET, PEN, etc.), polycarbonate film (PC), polymethyl methacrylate film (PMMA), triacetyl cellulose film (TAC), amorphous polyolefin film (amorphous PO) are made of glass. Compared to the above, it has suitable properties such as light weight, hard to break, and bendable, but the surface of the film is low due to low hardness and wear resistance. In some cases, the product value is likely to be damaged, and the value of the product may be remarkably reduced or unusable.

  For this reason, the method of providing the hard-coat layer excellent in abrasion resistance and abrasion resistance on said base film is known, and is utilized universally as a hard-coat film. However, when it is used as a film for various displays such as a liquid crystal display panel (LCD) and a plasma display panel (PDP), which are typical uses of optical films, the following problems can be mentioned. (1) Rainbow color unevenness (interference fringes) occurs due to the difference in refractive index between the provided hard coat layer and the substrate film. (2) There is a problem of a decrease in commercial value due to deformation caused by heat from the light source, heat during processing, and the like.

  The former interference fringes are caused by the difference in the refractive index between the base material and the hard coat layer. Due to the interference of light reflected at the interface, an iris-like reflection is observed when observed under a three-wavelength fluorescent lamp. When it is used, it is one cause of lowering the visibility.

  As a means for improving this phenomenon, there is a method of reducing the difference in refractive index between the substrate and the hard coat layer. As this method, a method of providing a primer layer having an intermediate refractive index between the substrate and the hard coat layer has been proposed. In this method, even if the intermediate layer is provided, the refractive index changes only in a stepwise manner, and the interference fringes are not reduced or eliminated. In addition, since a process of providing an intermediate layer is required, there is a problem that the cost increases. (See Patent Document 1)

  As another improvement method, a method for reducing interference fringes by applying a hard coating agent using a solvent that dissolves the base film and dissolving or swelling the base material is proposed (Patent Document 2). Has been.

  However, in the method of dissolving and swelling the base film, the applicable resin is limited, and a highly biaxially oriented polyester film is limited to a special solvent such as orthochlorophenol, and the working environment is extremely bad. Moreover, even if interference fringes can be reduced, the haze increases, and a low haze required for display applications cannot be obtained, resulting in poor visibility.

Further, it is known that the latter deterioration due to heat is improved by increasing the glass transition temperature of the base film. As for heat resistance, for example, films having glutaric anhydride units (see Patent Document 3 and Patent Document 4) are disclosed for the purpose of improving the heat resistance of acrylic resin films.
However, a transparent film having a single film and having high heat resistance, surface hardness, optical isotropy, and self-supporting properties has not yet been proposed, and the development of this film is a polarizing plate protective film, an antireflection film, It can be suitably used as a wide range of optical films such as a diffusion film and a light collecting film.
JP 2000-111706 A JP 2003-205563 A JP-A-7-268036 JP 2004-2711 A

  An object of the present invention is to provide a transparent film having the above-mentioned drawbacks in the prior art, specifically, self-supporting ability, excellent heat resistance, surface hardness, and optical isotropy.

（６）ガラス転移点温度が１２０℃以上であり、
（７）破断伸度が３％以上３０％以下であることを特徴とする透明架橋フィルムに関するものである。 In order to achieve this object, the present inventors have conducted intensive research and have found that the object can be achieved by the following means.
That is, the present invention
(1) A liquid actinic radiation curable composition containing 5 to 50 parts by weight of a polyfunctional acrylate and 0.5 to 10 parts by weight of an oligohydroxyketone initiator is crosslinked with respect to 100 parts by weight of a vinyl ester composition. Transparent crosslinked film,
(2) The retardation is 5 nm or less,
(3) The vinyl ester composition is a vinyl ester composition obtained by esterifying a bisphenol type or alicyclic epoxy compound with acrylic acid or methacrylic acid,
(4) The oligohydroxyketone-based initiator includes a component that generates radicals upon irradiation with actinic rays having a molecular weight of 400 to 10500,
(5) The oligohydroxyketone-based initiator has a structure represented by Formula 1, and includes a component that generates radicals upon irradiation with active rays having a value of n of 2 to 50,

(6) The glass transition temperature is 120 ° C. or higher,
(7) The present invention relates to a transparent crosslinked film characterized by having a breaking elongation of 3% or more and 30% or less.

  Since the transparent crosslinked film of the present invention has the above-described configuration, it has a self-supporting property as a single film and has a sufficient surface hardness, so there is no need to laminate a surface hardened layer, and the heat resistance is high. Therefore, there is almost no deformation due to thermal deterioration, interference fringes are eliminated, and optical isotropic effects are exhibited.

Hereinafter, embodiments of the transparent crosslinked film of the present invention will be specifically described.
The transparent crosslinked film of the present invention is a film comprising a vinyl ester composition as a main constituent, a trifunctional or higher polyfunctional acrylate as an auxiliary component, and, if necessary, a bifunctional or lower acrylate.

  Here, the vinyl ester composition (a) is defined as a vinyl ester that is a series of oligoacrylates that share a secondary hydroxyl group generated by a ring-opening reaction of an epoxy group and a (meth) acryloyl group in the same molecule. The vinyl ester composition (a) preferably used in the present invention is obtained by esterifying a bisphenol type or alicyclic epoxy compound with acrylic acid or methacrylic acid. Examples of the bisphenol type or alicyclic epoxy compound include the following.

  Reaction product of bisphenol A and epichlorohydrin, reaction product of bisphenol F and epichlorohydrin, reaction product of hydrogenated bisphenol A and epichlorohydrin, reaction product of cyclohexanedimethanol and epichlorohydrin, reaction product of norbornane dialcohol and epichlorohydrin, tetra Reaction product of bromobisphenol A and epichlorohydrin, reaction product of tricyclodecanedimethanol and epichlorohydrin, alicyclic diepoxy adipate, alicyclic diepoxy carbonate, alicyclic diepoxy acetal, alicyclic diepoxy carboxylate Etc.

  Next, the polyfunctional acrylate as the second component of the present invention is a composition having 3 (more preferably 4 or 5) or more (meth) acryloyloxy groups in one molecule, and is a specific example. As pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (Meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol triacrylate hexanemethylene diisocyanate urethane polymer, and the like can be used. These compositions can be used 1 type or in mixture of 2 or more types.

  In addition, commercially available polyfunctional acrylic compositions include Mitsubishi Rayon Co., Ltd. (trade name “Diabeam” series, etc.), Nagase Sangyo Co., Ltd. (trade name “Denacol” series, etc.), Shin Nakamura Co., Ltd .; (Product name “NK Ester” series, etc.), Dainippon Ink and Chemicals Co., Ltd .; (Product name “UNIDIC”, etc.), Toa Gosei Chemical Industry Co., Ltd. (“Aronix” series, etc.), Nippon Oils and Fats Corporation; Such as “Blenmer” series), Nippon Kayaku Co., Ltd .; (trade name “KAYARAD” series, etc.), Kyoeisha Chemical Co., Ltd .; (trade name “light ester” series, etc.), etc. be able to.

These polyfunctional acrylates are effective in improving the surface hardness of the film. The compounding quantity of polyfunctional acrylate is 5-50 weight part with respect to 100 weight part of said vinyl ester composition, Preferably it is 10-30 weight part, More preferably, it is 15-25 weight part. When the blending amount of the polyfunctional acrylate is less than 5 parts by weight, the surface hardness is insufficient, and when it exceeds 50 parts by weight, brittleness appears even if the elongation of the film is lowered, causing a problem in self-supporting property.
The surface hardness of the transparent crosslinked film of the present invention is H or higher, preferably 2H or higher in terms of pencil hardness from the viewpoint of scratch resistance.

  In addition to the above-mentioned vinyl ester composition and mixture of polyfunctional acrylates, the following bifunctional or lower acrylate compounds can be used for the purpose of lowering the viscosity within the range not impairing the effects of the present invention.

  Allyl ester monomers: diallyl orthophthalate, diallyl isophthalate, diallyl terephthalate, diallyl 1,4-cyclohexanedicarboxylate, diallyl succinate.

  Acrylic acid ester monomers and methacrylic acid ester monomers: methyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxylethyl methacrylate, 2-hydroxypropyl methacrylate, EO adduct dimethacrylate of bisphenol A, EO adduct diacrylate of bisphenol A , Polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, phenoxyethyl methacrylate, isobornyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, dicyclopentenyloxyethyl acrylate, dicyclopentenyloxyethyl methacrylate, tri Methylolpropane diacrylate Trimethylol propane dimethacrylate, glycerol diacrylate, glycerol dimethacrylate, glycerol dimethacrylate, 2,6-dibromo -4-tert-butylphenyl acrylate, various urethane acrylates, epoxy acrylates.

Next, the photopolymerization initiator will be described.
The oligohydroxyketone photopolymerization initiator is, for example, a compound represented by the following formula (1), and the number of repeating units n is 2-50. The oligohydroxyketone-based photopolymerization initiator has a site for generating a plurality of radicals in one molecule.

  The oligohydroxyketone-based photopolymerization initiator that can be used in the present invention is preferably a composition containing a component having a point that generates a plurality of radicals upon irradiation with actinic rays having a molecular weight of 400 or more and 10500 or less. 1) (where R2 and R3 are alkyl groups having 1 to 5 carbon atoms, R1 is a divalent aromatic group such as a phenylene group or a biphenylene group, and n is 2 to 50, preferably 2 to 20) It is possible to use a compound represented by

  In formula (1), examples of the alkyl group having 1 to 5 carbon atoms include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, t-butyl group, n-pentyl group, i -A pentyl group etc. can be mentioned. Among these, an alkyl group having 1 to 3 carbon atoms is preferable, and further, a 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone polymer is preferably included. Examples of these commercially available products include ESACURE KIP150, ESACURE KK, ESACURE 75LT, ESACURE KIP100F, ESACURE KIPIT, ESACURE KTO46 (manufactured by LAMBERTI). Moreover, a sensitizer etc. can be used as needed.

  The amount of these oligohydroxyketone photopolymerization initiators used is 0.5 to 10 parts by weight, preferably 2 to 6 parts by weight, more preferably 3 to 5 parts by weight, based on 100 parts by weight of the vinyl ester composition. is there. If the amount of the oligohydroxyketone photopolymerization initiator used exceeds 10 parts by weight, it may adversely affect the curing properties of the resin liquid, the physical properties of the cured product, the handling of the resin liquid, etc. Further, the curing rate may be slow or the curing may be poor, resulting in a decrease in productivity.

  The transparent crosslinked film of the present invention preferably has a glass transition temperature in differential scanning calorimetry of 120 ° C. or higher, more preferably 130 ° C. or higher, and a pencil hardness of H or higher. For this reason, it is suitable to make said photoinitiator into the addition amount range of 0.5-10 weight part with respect to 100 weight part of vinyl ester compositions.

  The glass transition temperature is generally referred to as a glass transition temperature (temperature) when a polymer substance is heated to change from a glassy hard state to a rubbery state. In the present invention, a glass transition temperature is measured using a differential scanning calorimeter (DSC) according to JIS K7121.

  When the structure of the photopolymerization initiator is not an oligohydroxyketone system, the glass transition point temperature in the differential scanning calorimetry of the transparent crosslinked film is not sufficiently high, so that the film is likely to be deformed or deteriorated due to heat. Distortion occurs and processability is reduced. The glass transition temperature is preferably as high as possible when applied to optical applications, and it is desirable that the glass transition temperature does not change for a long time when exposed to heat generated from the apparatus or the use environment.

  The breaking elongation of the transparent crosslinked film of the present invention is desirably 3% or more and 30% or less. When the elongation at break is less than 3%, the self-supporting property of the film is lowered and handling may be difficult. Further, if the elongation at break exceeds 30%, the surface hardness is likely to decrease. For these reasons, it is important to balance the elongation at break, self-supporting property and surface hardness.

  The vinyl ester composition, the polyfunctional acrylate, and the liquid actinic radiation curable composition containing a photopolymerization initiator constituting the transparent crosslinked film used in the present invention may be diluted with a solvent or used without a solvent. It can also be. A solvent can also be used individually or in mixture of 2 or more types. It is preferable to include an organic solvent in order to facilitate uniform dispersibility in the film of the photopolymerization initiator, improvement in workability during coating, smoothness of the film, control of the thickness, and the like. In particular, it is preferable in terms of isotropic refractive index of the film to reduce the shearing force during film formation and to form a film with a low viscosity using an organic solvent in order to relax the orientation in one direction. Further, in the case of curing with ultraviolet rays, it is efficient and preferable to perform ultraviolet irradiation in a nitrogen atmosphere.

  Although the specific film forming method is illustrated below, it is not necessarily limited to this. The liquid actinic radiation curable composition is cast on a substrate such as a film, a metal plate, a rotating mirror drum, or an endless driving belt, and after drying the solvent as necessary, it is irradiated with ultraviolet rays. A method in which the film obtained by crosslinking and curing is continuously peeled off from the mirror drum or the belt and wound is preferred. When this method is used, the surface of a substrate such as a film, metal plate, drum or belt is applied to the surface with silicone, a fluorine compound or the like in order to reduce the peeling stress of the film after curing and to maintain the film's isotropy. It is preferable to use a mold that has been subjected to a mold release treatment.

  The thickness of the transparent crosslinked film used in the present invention is preferably 5 to 300 μm, more preferably 20 to 150 μm, from the viewpoint of mechanical strength and handling properties.

  The transparent crosslinked film of the present invention may contain various additives, resin compositions, crosslinking agents and the like within a range that does not impair the effects of the present invention. For example, antioxidants, heat stabilizers, ultraviolet absorbers, organic and inorganic particles (for example, silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate, barium sulfate, carbon black, zeolite, titanium oxide, Metal fine powders), pigments, dyes, antistatic agents, nucleating agents, acrylic resins, polyester resins, urethane resins, polyolefin resins, polycarbonate resins, alkyd resins, epoxy resins, urea resins, phenol resins, silicone resins, rubber resins , Wax composition, melamine crosslinking agent, oxazoline crosslinking agent, methylolated, alkylolized urea crosslinking agent, acrylamide, polyamide, epoxy resin, isocyanate compound, aziridine compound, various silane coupling agents, various titanates And the like can be mentioned system coupling agent.

  The transparent crosslinked film of the present invention desirably has a retardation of 5 nm or less, preferably 3 nm or less, more preferably 1.5 nm or less. Thereby, it can have the characteristic which is optically isotropic. In the present invention, retardation is used as an index of optical isotropy.

  The retardation here means both the retardation (Re) in the film plane and the retardation (Rth) in the film thickness direction, and the main refractive index of the film is nx (in-plane width direction), ny (plane). Inner longitudinal direction), nz (thickness direction), and film thickness d (nm), Re = | nx−ny | × d, Rth = | (nx + ny) / 2−nz | × d Is.

  Such Re and Rth can be measured using a commercially available automatic birefringence meter (for example, “KOBRA-21ADH” manufactured by Oji Scientific Instruments).

  In order to obtain such a film, the liquid actinic radiation curable composition is cast on a rotating drum or an endless driving belt and irradiated with ultraviolet rays to be cured. Alternatively, it is important not to apply excessive stress in the film forming method in which the belt is continuously peeled off and wound up. If excessive stress acts on the film during peeling, etc., molecular orientation occurs in the film surface and retardation increases. Therefore, it is effective to apply a treatment capable of peeling with low stress to the surface of the drum or belt. Specifically, it is peeled off by a method of winding with a low tension or slowly. In addition, the surface treatment of the substrate is preferably a treatment with silicone or a fluorine compound.

  Various coating methods such as reverse coating method, gravure coating method, comma coating method, rod coating method, bar coating method, die coating method, spray coating method and the like are used as coating means when forming the composition into a film. be able to.

  The transparent crosslinked film of the present invention is a single film having a self-supporting property excellent in surface hardness, transparency, heat resistance, optical isotropy, an antireflection film, a polarizing plate protective film, an electromagnetic shielding film, a diffusion film, It can be suitably used as a base film such as an optical film member such as a prism film, a name plate, and a decorative plate.

[Characteristic measurement method and effect evaluation method]
The characteristic measurement method and effect evaluation method in the present invention are as follows. Unless otherwise specified, the average value of the measured values of the three samples is taken as the value in each measurement.

(1) Optical isotropy The central part of the sample is measured in the low phase difference mode using an automatic birefringence meter KOBRA-21ADH manufactured by Oji Scientific Instruments and its equivalent. The measurement wavelength is 590 nm, the slow axis is fixed, the incident angle is changed every 10 ° from 0 ° to 50 °, and the incident angle dependency of the phase difference is measured. A value at an incident angle of 0 ° is defined as an in-plane retardation (Re), and thickness direction retardation (Rth) is calculated using measured values at an incident angle of 0 ° and 40 °.

(2) Pencil hardness Measured with a measurement load of 500 g according to JIS K-5400 (1990) using HEIDON (manufactured by Shinto Kagaku Co., Ltd.) or an equivalent thereof.

(3) Heat resistance
A glass transition temperature is measured by using a DSC (differential scanning calorimeter) manufactured by Perkin Elmer Co., Ltd. or an equivalent of the sample at a sample temperature of 10 mg and a heating rate of 20 ° C./min. This glass transition temperature is used as an index of heat resistance.
120 degreeC or more was set as the pass.

(4) Self-supporting property Judgment is made based on whether or not the film breaks when bent at 180 ° at 25 ° C. and 65% RH. If all three sample films do not break, they are self-supporting.

(5) Elongation at break Strain (elongation rate) when the film was ruptured at 25 ° C. and 65% RH using a tensile tester manufactured by Orientec Co., Ltd. or an equivalent product according to the JIS K 7127 method. Is determined as the elongation at break.

(6) Molecular weight measurement method Molecular weight measurement is performed using a matrix-assisted ionization-time mass spectrometer (AXIMA-CFR, manufactured by Shimadzu Corporation) or an equivalent thereof.

(7) Presence / absence of interference fringes The interference fringes were evaluated in a state where a hard coat layer was laminated on the sample according to the following method. First, a hard coat layer was provided on one side of the sample so as to have a thickness of about 5 μm. The hard coat layer is a hard coat paint (Z7528 made by JSR, 50% concentration or equivalent), using a # 10 metering bar, formed into a thin film, placed in an oven at 90 ° C., and heat treated for 1 minute. After that, UV irradiation is performed once through a conveyor type UV irradiation apparatus equipped with one high pressure mercury lamp (120 W) at a speed of 5 m / min. In this way, a sample in which the hard coat layer is laminated is obtained.

Furthermore, in order to eliminate the influence of the reflection on the back surface, the back surface (the surface opposite to the hard coat layer surface) was roughened with sandpaper No. 240, and a sample prepared by coloring with black magic ink (registered trademark) was prepared. When placed in a dark room, 30 cm directly under a three-wavelength fluorescent lamp (National Parrook, three-wavelength daylight white (F.L 15EX-N 15W) or equivalent) Evaluation is based on whether the pattern is visible. The lowest rating of the 3 samples is used.
-Iris pattern is not visible: A rank-Very weak iris pattern is visible: B rank-Weak rainbow color pattern is visible: C rank-Strong rainbow color pattern is clearly visible: D rank.

(8) Total light transmittance A test is performed in accordance with JIS K 7105 method. The total light transmittance is an average value of 10 samples.

(9) Haze The haze is tested according to JIS K 7105 method.

Next, although this invention is demonstrated based on an Example, this invention is not necessarily limited to these.
(Coating agent adjustment)
(Coating agent 1: vinyl ester composition)
In a 1 L flask equipped with a thermometer, stirrer, fractionation condenser, and gas introduction tube, 374.4 g (1.20 mol) of bisphenol A diepoxy compound, 206.4 g (2.4 mol) of methacrylic acid, chromium octylate 1.5 g, 0.15 g of phosphorous acid, and 0.2 g of hydroquinone were added, and the reaction was performed at 120 to 125 ° C. for 2 hours while blowing nitrogen gas. When the acid value reached 11.0, the composition in the flask was poured into a metal vat and cooled to obtain a colorless and transparent vinyl ester composition.

(Coating agent 2: polyfunctional acrylate)
DPHA (dipentaerythritol hexaacrylate: Nippon Kayaku Co., Ltd .: solid content 100%) was used as the polyfunctional acrylate.

(Coating agent 3: Other acrylate)
1,6-hexanediol diacrylate (100% solid content) was used as a reaction diluent.

(Photoinitiator 1: Oligohydroxyketone photopolymerization initiator)
2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone polymer (ESACURE KIP150: manufactured by LAMBERTI) was used.

(Photoinitiator 2: Hydroxyketone photopolymerization initiator)
1-Hydroxy-cyclohexyl-phenyl ketone (“Irgacure 184” manufactured by Nagase Sangyo Co., Ltd.) was used.
The above materials were mixed at a mixing ratio (solid weight ratio) shown in Table 1 to obtain a coating solution.

(Film forming method)
After coating the prepared coating solution on a fluorine-treated metal plate using an applicator, the resin composition was cured by irradiating with ultraviolet rays having an irradiation intensity of 800 mJ / cm ^2, and peeled from the metal plate to obtain a film. The film thickness was 50 μm.
Table 2 shows the evaluation results of the film prepared by the above method.

  As is apparent from Table 2, when the blending amount of the oligohydroxyketone-based photopolymerization initiator or the non-oligohydroxyketone-based photopolymerization initiator was small (Comparative Examples 1 and 3), the prepared coating liquid was not cured. . Moreover, when it was blended in a large amount beyond the scope of the present invention (Comparative Examples 2 and 6), the surface hardness and transparency were inferior, and the glass transition temperature was insufficient. On the other hand, when the oligohydroxyketone photopolymerization initiator is within the scope of the present invention (Examples 1 to 3), the film has a good balance of surface hardness, self-supporting property, transparency, and optical isotropy. It was.

  However, when a photopolymerization initiator that is not an oligohydroxyketone type is used (Comparative Examples 3 to 6), the glass transition temperature and the elongation at break were insufficient. On the other hand, when an oligohydroxyketone photopolymerization initiator is used (Examples 1 and 2), a glass transition temperature exceeding 120 ° C. and a photopolymerization initiator whose breaking elongation is not an oligohydroxyketone system are used. It was bigger than when it was used.

  Further, when the amount of the polyfunctional acrylate is less than the range of the present invention (Comparative Example 7), the surface hardness becomes insufficient, and when the amount of the polyfunctional acrylate exceeds the range of the present invention (Comparative Example 8), self The support was insufficient and it was broken by bending.

  When each composition is within the scope of the present invention as shown in Table 2 (Examples 1 to 3), it is excellent in self-supporting property, has a high glass transition temperature, and has excellent hardness and transparency. there were.

The transparent crosslinked film of the present invention is excellent in transparency, heat resistance and surface hardness, satisfactory as an optical film, and excellent in self-supporting as a single film having optical isotropy. It can be suitably used as a substrate film.

Claims (7)

  Transparent crosslinking in which a liquid actinic radiation curable composition containing 5 to 50 parts by weight of a polyfunctional acrylate and 0.5 to 10 parts by weight of an oligohydroxyketone initiator is crosslinked with respect to 100 parts by weight of a vinyl ester composition the film.   The transparent crosslinked film according to claim 1, wherein the retardation is 5 nm or less.   The transparent crosslinked film according to claim 1 or 2, wherein the vinyl ester composition is a vinyl ester composition obtained by an esterification reaction between a bisphenol type or alicyclic epoxy compound and acrylic acid or methacrylic acid.   The transparent crosslinked film according to any one of claims 1 to 3, wherein the oligohydroxyketone-based initiator includes a component having a molecular weight of 400 or more and 10500 or less and generating a radical upon irradiation with active rays. The oligo-hydroxyketone-based initiator has a structure represented by the formula (1), and includes a component that generates a radical upon irradiation with active rays having a value of n of 2 to 50. Transparent crosslinked film.

  The transparent cross-linked film according to claim 1, wherein the glass transition temperature is 120 ° C. or higher. The transparent crosslinked film according to any one of claims 1 to 6, which has a breaking elongation of 3% to 30%.