JP2008239673A - Transparent crosslinked film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optically isotropic transparent crosslinked film having excellent surface hardness, and singly self-supporting properties, free from interference fringes and having excellent stainproof properties. <P>SOLUTION: The transparent crosslinked film is obtained by curing and crosslinking a composition obtained by mixing 100 pts.wt. vinyl ester composition with 5-50 pts.wt. polyfunctional acrylate and 5-50 pts.wt. (meth)acrylate having a fluorene skeleton. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transparent cross-linked film, and more specifically, the film of the present invention has self-supporting properties, has transparency and optical isotropy suitable as an optical film, and is excellent in surface hardness and heat resistance. 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 (non-crystalline PO), etc. In addition, while having suitable properties such as light weight, hard to break, and bendable, the film surface has low hardness and lacks abrasion resistance, so damage to the surface due to contact with other hard substances, scratching, etc. The product value is likely to be significantly 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 used as various display films such as liquid crystal display panels (LCD) and plasma display panels (PDP), which are typical applications of optical films, or touch panel films such as car navigation systems and personal digital assistants (PDAs). The following issues can be raised. (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) Deformation under severe usage conditions that require heat resistance, such as drying, vapor deposition and sputtering during coating on the hard coat layer, or use in automobiles Arise.

  The former interference fringe is a phenomenon in which an iris-like reflection is observed when observing under a three-wavelength fluorescent lamp due to interference of light reflected at the interface of each layer of the multi-laminate, and this reduces visibility when used for display applications. One cause.

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 is increased. (See Patent Document 1)
As another improvement method, there is a method of reducing interference fringes without reflecting interface by applying a hard coat agent using a solvent that dissolves the base film and dissolving or swelling the base material (see Patent Document 2). Proposed.

  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.

  Moreover, about the latter heat resistance, the film (refer patent document 3 and patent document 4) which has a glutaric anhydride unit is disclosed, for example in order to improve the heat resistance of an acrylic resin film.

  However, if the heat resistance is simply improved by adjusting the composition of the acrylic resin film, the self-supporting property is insufficient, and it becomes easy to break due to bending stress, and sufficient toughness required during processing cannot be obtained.

  Moreover, in order to improve the heat resistance and toughness of the acrylic resin film at the same time, a film in which a crosslinked elastic body is contained in an acrylic resin containing a methyl methacrylate unit, a glutaric anhydride unit, and a styrene-based unit (see Patent Document 5) Is disclosed. However, since this film contains styrene units in the acrylic resin, heat resistance and transparency are not sufficient, and flatness deteriorates when processed at high speed and high temperature and high tension to improve productivity, In applications where high light transmittance is required, such as film for use, there has been a problem that the performance is insufficient.

A film that solves the above problems, that is, a material film that has self-supporting properties, has no interference fringes, has a hard coat property, and has heat resistance, is a material that is expected to be applied for optical use. When used as a protective film for liquid crystal displays or the like, it is desired that the retardation, which is an index of optical isotropy, be as low as possible.
JP 2000-111706 A JP 2003-205563 A JP-A-7-268036 JP 2004-2711 A JP 2000-178399 A

In view of the disadvantages of the prior art, the present invention is a transparent cross-linked film having excellent surface hardness, independent self-supporting properties, no interference fringes, excellent antifouling properties, and optically isotropic properties. Is intended to provide.

  The present invention employs the following means in order to solve such problems. That is, the transparent crosslinked film of the present invention cures a composition in which 5 to 50 parts by weight of a polyfunctional acrylate and 5 to 50 parts by weight of a (meth) acrylate having a fluorene skeleton are mixed with 100 parts by weight of a vinyl ester composition. It is characterized by being crosslinked.

Moreover, the preferable aspect of the transparent crosslinked film of this invention is:
(1) The retardation is 5 nm or less,
(2) Refractive index is 1.56 or more,
(3) The vinyl ester composition is a composition obtained by esterifying a bisphenol type or alicyclic epoxy compound with acrylic acid or methacrylic acid.

According to the transparent cross-linked film of the present invention, it has a self-supporting property as a single film and has sufficient surface hardness, so there is no need to laminate a surface hardened layer, no interference fringes, and further heat resistance Excellent optical properties and is optically transparent and isotropic, so it is an optical film member such as an antireflection film, a polarizing plate protective film, an electromagnetic wave shielding film, a diffusion film, and a prism film, and a base film such as a name plate and a decorative plate. In addition, substrate films for various displays can be provided.
There is an effect.

  The present invention, the above-mentioned problem, that is, a transparent cross-linked film having excellent surface hardness, self-supporting ability, no interference fringes, excellent antifouling properties, and optically isotropic studies When a single film was formed by curing and crosslinking a composition formed by mixing a polyfunctional acrylate and a (meth) acrylate having a fluorene skeleton into the main vinyl ester composition, such a problem was found. It has been sought to solve all at once.

  Hereinafter, embodiments of the present invention will be specifically described.

  The transparent crosslinked film of the present invention is a film formed by using a composition obtained by mixing a polyfunctional acrylate and (meth) having a fluorene skeleton in a main component vinyl ester composition.

Here, the vinyl ester composition is defined as 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. Such an acrylate is preferably obtained by esterifying bisphenol-type or alicyclic epoxy compound with acrylic acid or methacrylic acid.
Examples of such bisphenol type or alicyclic epoxy compounds include the following. That is, a reaction product of bisphenol A and epichlorohydrin, a reaction product of bisphenol F and epichlorohydrin, a reaction product of hydrogenated bisphenol A and epichlorohydrin, a reaction product of cyclohexanedimethanol and epichlorohydrin, a reaction product of norbornane alcohol and epichlorohydrin , Reaction product of tetrabromobisphenol A and epichlorohydrin, reaction product of tricyclodecane dimethanol and epichlorohydrin, alicyclic diepoxy adipate, alicyclic diepoxy carbonate, alicyclic diepoxy acetal, alicyclic diepoxy Carboxylate and the like.

  Next, the polyfunctional acrylate which is the second component of the present invention is a compound having 3 (more preferably 4 or 5) or more (meth) acryloyloxy groups in one molecule. Are pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa ( A (meth) acrylate, a trimethylol propane tri (meth) acrylate, a pentaerythritol triacrylate hexanemethylene diisocyanate urethane polymer, etc. can be used. These monomers can be used alone or in combination of two or more. Commercially available polyfunctional acrylic compounds 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. If the blending amount of this polyfunctional acrylate is less than 5 parts by weight, the surface hardness is insufficient, and conversely if it exceeds 50 parts by weight, the elongation of the film is lowered, the brittleness is developed, and there is a problem in self-supporting property. Arise.

  In addition, the surface hardness of the transparent crosslinked film of the present invention is preferably H or higher, more preferably 2H or higher in terms of pencil hardness from the viewpoint of scratch resistance. The blending amount of the polyfunctional acrylate is determined in consideration of such surface hardness.

  In addition to the mixture of the vinyl ester composition and the polyfunctional acrylate, a compound such as an allyl ester monomer, an acrylate monomer, and a methacrylic acid ester monomer is reduced in viscosity within a range not inhibiting the effects of the present invention. It may be used for such purposes.

That is, as the allyl ester monomer, diallyl orthophthalate, diallyl isophthalate, diallyl terephthalate, diallyl 1,4-cyclohexanedicarboxylate, diallyl succinate and the like can be used.
Examples of the acrylic acid ester monomer and methacrylic acid ester monomer include methyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxylethyl methacrylate, 2-hydroxypropyl methacrylate, EO adduct dimethacrylate of bisphenol A, and EO of bisphenol A. Adduct diacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, phenoxyethyl methacrylate, isobornyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, dicyclopentenyloxyethyl acrylate, dicyclopentenyloxy Ethyl methacrylate, trimethylolpropane Acrylate, trimethylolpropane dimethacrylate, glycerine diacrylate, glycerine dimethacrylate, glycerine dimethacrylate, 2,6-dibromo -4-tert-butylphenyl acrylate, various urethane acrylates can be used such as epoxy acrylate.

  Next, (meth) acrylate having a fluorene skeleton is used as the third component constituting the vinyl ester composition of the present invention. The (meth) acrylate having such a fluorene skeleton is selected and used as long as the properties of the transparent film (surface hardness, transparency, optical isotropy) are not impaired.

  The (meth) acrylate having such a fluorene skeleton is one having 1 to 2 (meth) acryloyloxy groups in the molecule. The (meth) acrylate compound having a fluorene skeleton preferably used in the present invention is represented by the following general formulas (Formula 1) to (Formula 3).

In the formula, R ₁ , R ₂ , R ₅ , R ₆ and R ₇ represent a hydrogen atom and a methyl group, R ₃ and R ₄ represent a hydrogen atom, a methyl group and an ethyl group, and R ₈ represents a hydrogen atom or carbon. Represents an alkyl group having 1 to 6 carbon atoms, and examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, and n-hexyl. Represents a linear or branched alkyl group such as n1 and n2 represent an integer of 0 to 3, n3 and n4 represent an integer of 1 to 3, and n5 represents an integer of 0 to 10. R _{1 to} R ₈ are preferably a hydrogen atom or a methyl group. Furthermore, it is preferable that R1-R9 is the same and is a hydrogen atom or a methyl group.

  The (meth) acrylate having such a fluorene skeleton is obtained by a known method using (meth) acrylic acid, (meth) acrylic acid or (meth) acrylic acid chloride, and alcohol or fluorene ring substitution with fluoric acid. It is obtained by (OH) esterifying an OH group. Further, an alcohol having a fluorene ring or a fluorene ring-substituted —OH group-containing compound is reacted with a reactive compound or cyclic ester compound having an epoxy ring, a carboxylic acid compound having a hydroxyl group, or the like, and further the hydroxyl group is (meth) It can also be obtained by acrylic esterification.

  Examples of the alcohol having a fluorene ring or a fluorene ring-substituted -OH group-containing compound used here include 9-fluorenemethanol, 9,9-bis (4-hydroxyethyloxyphenyl) fluorene, and 9,9-bis (3 -Methyl-4-hydroxyethyloxyphenyl) fluorene, 9,9-bis (3-ethyl-4-hydroxyethyloxyphenyl) fluorene, 9,9-bis (3,3'-dimethyl-4-hydroxyethyloxyphenyl) Fluorene, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, 9,9-bis (3-ethyl-4-hydroxyphenyl) fluorene, etc. Can be mentioned.

  Examples of the reactive compound having an epoxy group include epoxide compounds such as ethylene oxide, propylene oxide, styrene oxide, and cyclohexene oxide, methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, 2- Glycidyl ether or glycidyl ester compounds having groups such as ethylhexyl, lauryl, stearyl, phenyl, 2-methylphenyl, furfuryl and the like can be used. Examples of cyclic ester compounds include γ-lactone and δ-lactone. Etc. can be used.

  As a commercial item of the (meth) acrylate derivative having a fluorene ring used in the present invention, for example, bisphenol full orange hydroxy acrylate, bisphenol fluor orange methacrylate and the like manufactured by Nippon Steel Chemical Co., Ltd. can be used. In addition, a fluorene acrylate compound (Ogsol EA series, Ogsol CA series, etc.) manufactured by Osaka Gas Chemical Co., Ltd. can be used.

  The addition amount of the (meth) acrylate having a fluorene skeleton in the present invention is 5 to 50 parts by weight, preferably 7 to 40 parts by weight, more preferably 10 to 30 parts by weight with respect to 100 parts by weight of the vinyl ester composition. . When the amount added is less than 5 parts by weight, the heat resistance is insufficient. On the other hand, when it exceeds 50 parts by weight, it becomes brittle and the self-supporting property becomes insufficient, which is not preferable.

In the transparent crosslinked film of the present invention, a polymerization initiator can be added depending on the curing method in order to crosslink the composition. As a method for crosslinking, either one of heat crosslinking or ionizing radiation crosslinking, for example, crosslinking by ultraviolet rays, electron beams or the like, or a combination of both methods can be used.
First, in the case of heat crosslinking, it is effective to use an organic peroxide as a polymerization initiator. As such organic peroxides, known ones such as dialkyl peroxides, acyl peroxides, hydroperoxides, ketone peroxides, and peroxyesters can be used, and specific examples are shown below. Yes.
That is, benzoyl peroxide, t-butylperoxy-2-ethylhexanate, 2,5-dimethyl-2,5-di (2-ethylhexanoyl) peroxyhexane, t-butylperoxybenzoate, t-butyl Hydroperoxide, cumene hydroperoxide, dicumyl peroxide, di-t-butyl peroxide, 1,1,3,3-trimethylbutylperoxy-2-ethylhexanate, 2,5-dimethyl-2,5 -Dibutyl peroxyhexane or the like can be used.
Moreover, when carrying out ultraviolet crosslinking, the well-known photoinitiator which is illustrated below can be used as a polymerization initiator.
2,2-dimethoxy-1,2-digenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, bezophenone, 2-methyl-1- (4-methylthiophenyl) -2-monforinopropanone -1,2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2,4,6- Trimethylbenzoyldiphenyl-phosphine oxide or the like can be used. Moreover, a crosslinking accelerator can also be added as needed.

The amount of the polymerization initiator added is preferably 0.05 to 3.0 parts by weight, more preferably 0.1 to 2 parts by weight, with respect to 100 parts by weight of the mixture of the vinyl steal composition and the polyfunctional acrylate. It is good to do.
In the case of electron beam crosslinking, it is not particularly necessary to use an initiator. In addition, in the case of crosslinking with ultraviolet rays, it is preferable to employ ultraviolet irradiation in a nitrogen atmosphere because it is efficient.

In the present invention, a method of crosslinking by ionizing radiation is preferably employed. Specific film forming methods will be exemplified below.
That is, the composition is cast on a film, a metal plate, a rotating drum, or an endless driving belt, and after drying, is crosslinked by irradiating with ultraviolet rays or an electron beam, and the resulting film is drum or A method of continuously peeling and winding up from the belt is preferably used.

  When this method is used, the surface of the film, metal plate, drum and belt is subjected to surface treatment with silicone, a fluorine compound or the like in order to reduce the peeling stress of the crosslinked film and maintain the isotropy of the film. Is preferred.

  The thickness of the transparent crosslinked film of the present invention is preferably 5 to 200 μm, more preferably 20 to 100 μm, from the viewpoint of mechanical strength and handling properties.

In addition, 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 powder, cross-linked polymer particles, etc.), pigments, dyes, surfactants, ionic conductive agents such as polystyrene sulfonate, anti-static agents such as electron conductive materials such as polythiophene doped bodies and polyaniline doped bodies , Nucleating agent, acrylic resin, polyester resin, urethane resin, polyolefin resin, polycarbonate resin, alkyd resin, epoxy resin, urea resin, phenol resin, silicone resin, rubber resin, wax composition, melamine crosslinking agent, oxazoline crosslinking Agent, methylolation, alkyl Lumpur of urea-based crosslinking agents, acrylamide, polyamide, epoxy resins, isocyanate compounds, aziridine compounds, various silane coupling agents may contain various titanate coupling agent.

  The transparent crosslinked film of the present invention has a retardation of preferably 5 nm or less, more preferably 3 nm or less, and particularly preferably 1.5 nm or less. By controlling to such a retardation, it is possible to have characteristics that have antistatic properties that are not dependent on humidity and that are optically isotropic. In the present invention, retardation is used as an index of optical isotropy.

The retardation here means both retardation in the film plane (Re) and retardation in the film thickness direction (Rth), and the main refractive index of the film is _nx (in-plane width direction), _ny. (In-plane longitudinal direction), _nz (thickness direction), and the thickness of the film is d (nm), Re = | n _x −n _y | × d, Rth = | (n _x + n _y ) / 2 -N _z | × d.

  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 curable composition is cast on a rotating drum or an endless driving belt and irradiated with ultraviolet rays or an electron beam 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. In other words, 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 process capable of peeling with low stress on the surface of the drum or belt. is there. Such surface treatment is preferably treatment with silicone or a fluorine compound.

  The transparency of the transparent crosslinked film of the present invention is such that the total light transmittance in the visible light region is preferably 85% or more, more preferably 88% or more, particularly preferably 90% or more, and haze is preferably 1. It is 5% or less, more preferably 1% or less, and particularly preferably 0.7% or less.

  Various coating methods such as a reverse coating method, a gravure coating method, a rod coating method, a bar coating method, a die coating method, a spray coating method, and the like can be used as a coating means for forming the composition.

  The transparent crosslinked film of the present invention is a single film having self-supporting properties excellent in surface hardness, transparency, and antifouling properties, such as an antireflection film, a polarizing plate protective film, an electromagnetic wave shielding film, a diffusion film, and a prism film. It can be suitably used as a substrate film for optical film members, nameplates, decorative plates and the like.

  The refractive index of the transparent crosslinked film in the present invention is measured by an Abbe refractometer (manufactured by Atago Co., Ltd.) based on JIS K 7105 (1981), and the refractive index is preferably 1.56 or more. It is preferably 1.57 or more, particularly preferably 1.58 or more.

  By setting it as such a transparent crosslinked film, when the layer which has a refractive index lower than the refractive index of a transparent crosslinked film is laminated | stacked, antireflection performance becomes favorable and reflection of external light is suppressed. However, when the refractive index of the transparent crosslinked film is lower than 1.56, the minimum reflectance (bottom reflectance) in the visible light region of wavelength 400 to 700 nm is 1% or more, and the antireflection function may be insufficient. is there.

The bottom reflectance described in the present invention refers to the lowest reflectance of the surface reflectance at a wavelength of 400 to 700 nm of the antireflection film. A method for measuring the bottom reflectance will be described below.
That is, after the surface opposite to the measurement surface (antireflection layer side surface) is uniformly roughened with a 320-400 water resistant sandpaper so that the 60 ° gloss (JIS Z 8741) is 10 or less, A black paint is applied and colored so that the transmittance is 5% or less. Using a spectrophotometer (UV-3150) manufactured by Shimadzu Corporation, the absolute reflection spectrum in the wavelength region of 380 to 800 nm was measured at an incident angle of 5 ° from the measurement surface, and the lowest reflection at a wavelength of 400 to 700 nm. Find the rate.

  Various coating methods such as a reverse coating method, a gravure coating method, a rod coating method, a bar coating method, a die coating method, a spray coating method, and the like can be used as a coating means for forming the composition.

  The transparent crosslinked film of the present invention is a single film having a self-supporting property excellent in surface hardness, transparency, heat resistance, and optical isotropy, an antireflection film, a polarizing plate protective film, an electromagnetic wave shielding film, and 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.

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

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

(4) 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. For the hard coat layer, a hard coat paint (Z7528 made by JSR Co., 50% concentration) was formed using a # 10 metering bar and a thin film was formed. Ultraviolet irradiation was performed once through a conveyor type UV irradiation apparatus equipped with one lamp (120 W) at a speed of 5 m / min. In this way, a sample in which the hard coat layer was laminated was 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. , Whether or not the iris pattern can be seen when placed in a dark room 30 cm directly under a 3 wavelength fluorescent lamp (National Parrook 3 wavelength shape daylight white (FL 15EX-N 15W)) and viewing the sample while changing the viewpoint It was evaluated with.
-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.

(5) Self-supporting property The obtained film was allowed to stand at 25 ° C. and 65% RH for 24 hours, and then judged by whether or not the film was broken when bent at 180 degrees. When the film did not break, it was regarded as having self-supporting property.

(6) Total light transmittance The average value of the total light transmittance in the film thickness direction in the visible light region was determined using a fully automatic direct reading haze computer HGM-2DP (manufactured by Suga Test Instruments Co., Ltd.). The measurement was an average of 10 points.

(7) Haze The film sample was allowed to stand for 24 hours at 25 ° C. and 65% RH, and then the haze at a wavelength of 590 nm was measured using a fully automatic direct reading haze computer HGM-2DP (manufactured by Suga Test Instruments Co., Ltd.). The average value of three measurements was determined.

(8) Reflectance In order to eliminate the influence of back surface reflection, the surface opposite to the measurement surface (antireflection layer side surface) is numbered 320 to 400 so that the 60 ° gloss (JIS Z 8741 (1997)) is 10 or less. After uniformly roughening with a water-resistant sandpaper, a black paint was applied and colored so that the visible light transmittance was 5% or less. Using a spectrophotometer (UV-3150) manufactured by Shimadzu Corporation, the absolute reflection spectrum in the wavelength region of 380 to 800 nm was measured at an incident angle of 5 ° from the measurement surface, and the lowest reflection at a wavelength of 400 to 700 nm. The rate (bottom reflectance) was determined. A bottom reflectance of less than 1% was accepted.

  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. (Solid content 100%).

(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.

(Coating agent 4: acrylate containing fluorene skeleton 1)
As the acrylate having a fluorene skeleton, “Ogsol EA-0200” (manufactured by Osaka Gas Chemical Co., Ltd.) (solid content: 100%) was used.

(Coating agent 5: Acrylate 2 having a fluorene skeleton)
As the acrylate having a fluorene skeleton, “Ogsol CA-0400” (manufactured by Osaka Gas Chemical Co., Ltd.) (solid content: 100%) was used.

(Coating agent 6: glycidyl ether having a fluorene skeleton)
As the glycidyl ether having a fluorene skeleton, BPEF-G (bisphenoxyethanol fluorenediglycidyl ether: manufactured by Osaka Gas Chemical Co., Ltd.) (solid content: 100%) was used.

(Coating agent 7: alcohol monomer having a fluorene skeleton)
As an alcohol monomer having a fluorene skeleton, BPEF (bisphenoxyethanol fluorene: manufactured by Osaka Gas Chemical Co., Ltd.) (solid content: 100%) was used.

(Coating 8: Low refractive index coating 1)
219 parts by weight of methyltrimethoxysilane (“KBM-7103” manufactured by Shin-Etsu Silicone) was hydrolyzed with 89 parts by weight of 0.5N formic acid while stirring at 20 ° C. ± 5 ° C. After 60 minutes, 412 parts by weight of isopropyl alcohol was mixed to prepare a treatment liquid (X1).

  Similarly, 158 parts by weight of 3,3,3-trifluoropropyltrimethoxysilane (“KBM-7103” manufactured by Shin-Etsu Silicone) was hydrolyzed with 41 parts by weight of 1N formic acid while stirring at 30 ° C. ± 10 ° C. After 60 minutes, isopropyl alcohol 521 double parts were mixed to prepare a treatment liquid (X2).

  Next, a silica slurry (X3) consisting of 144 parts by weight of hollow silica particles having an outer shell with an average primary particle diameter of 50 nm and having a porosity of 30% (Catalyst Kasei Kogyo Co., Ltd. “Thru rear”) and 560 parts by weight of isopropyl alcohol Got ready.

  720 parts by weight of treatment liquid (X1), 720 parts by weight of treatment liquid (X2), 704 parts by weight of silica slurry (X3), 356 parts by weight of methanol, 4272 parts by weight of isopropyl alcohol, and 713 parts by weight of polypropylene glycol monoethyl ether were mixed. Thereafter, 15 parts by weight of acetoacetoxyaluminum as a curing catalyst was added and stirred and mixed again to prepare a paint having a refractive index of 1.37.

(Photoinitiator)
1-hydroxy-cyclohexyl ruphenyl 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.

(For Comparative Example 8, the coating material of the formulation of Example 2 was applied on a PET base film (“Lumirror” ^(R) U34: manufactured by Toray Industries, Inc.) so that the final thickness after crosslinking was 5 μm. .)
(Also, in Examples 11, 12, 13 and Comparative Examples 1 and 2, the coating 8 was coated on a transparent crosslinked film with a micro gravure coater, dried at 80 ° C., and then heat treated at 130 ° C. Cured to form a transparent crosslinked film in which a low refractive index layer having a thickness of about 0.1 μm was formed and an antireflection layer was provided.)
Table 2 shows the evaluation results of the film prepared by the above method.

  As is apparent from Table 2, when the amount of the acrylate having a fluorene skeleton is small (Comparative Examples 1 and 2), sufficient heat resistance cannot be obtained, and even when an antireflection layer is provided on the transparent crosslinked film The prevention property was inferior. When blended beyond the scope of the present invention (Comparative Example 3), the self-supporting property was inferior and was easily damaged by bending. When the blending amount of the acrylate having a fluorene skeleton is in the range of the present invention (Examples 1 to 7), the film has a good balance of surface hardness, self-supporting property, transparency, optical isotropy, and heat resistance. When the antireflection layer was provided on the transparent cross-linked film (Examples 11, 12, and 13), the antireflection characteristics were good.

  When the polyfunctional acrylate was not added (Comparative Example 4), the surface hardness was insufficient, and when blended beyond the scope of the present invention (Comparative Example 5), there was no self-supporting property and was easily damaged by bending. .

When the blending amount of the polyfunctional acrylate was within the range of the present invention (Examples 8 to 10), good characteristics were exhibited in all evaluations.
In the case of using a glycidyl ether having a fluorene skeleton instead of (meth) acrylate having a fluorene skeleton (Comparative Example 6) or using an alcohol monomer having a fluorene skeleton (Comparative Example 7), heat resistance, surface Hardness and optical isotropy were insufficient.

  In the case where the film of the present invention was laminated on a PET film (Comparative Example 8), interference fringes were remarkably generated due to the laminated structure having different refractive indexes, and the optical isotropy derived from PET was inferior.

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

Claims (4)

  A transparent composition obtained by curing and crosslinking a composition in which 5 to 50 parts by weight of a polyfunctional acrylate and 5 to 50 parts by weight of a (meth) acrylate having a fluorene skeleton are mixed with 100 parts by weight of a vinyl ester composition Cross-linked film.   Retardation is 5 nm or less, The transparent crosslinked film of Claim 1 characterized by the above-mentioned.   The transparent crosslinked film according to claim 1 or 2, wherein a refractive index is 1.56 or more.   The said vinyl ester composition is a composition obtained by esterifying a bisphenol type or alicyclic epoxy compound and acrylic acid or methacrylic acid. The transparent crosslinked film as described.