Coating agent for optics, and film for urethane-based primer

Abstract

To provide a coating agent capable of forming a film excellent in adhesion to an urethane-based primer layer even under a heat and humidity environment, and capable of forming a film having a high transparency and a high refractive index, and a film for an urethane-based primer.SOLUTION: A coating agent of the present invention at least includes the following constituents: (A); an oligomer, constituent (B); an aromatic urethane acrylate, and constituent (C); one or more selected from the group consisting of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate, and a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate, where the oligomer has a weight average molecular weight of 700 or more and 1,500 or less, and has a radical-polymerizable double bond part and a bisphenol part in a molecule.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an optical coating agent used for coating a urethane-based primer layer and a film for a urethane-based primer.

Background Art

[0002] An active energy ray-curable resin composition having a property of curing with active energy rays such as ultraviolet rays is used, for example, as a coating agent, and can form a film on various substrates. Such a film can exhibit various functions depending on the characteristics of the components contained in the coating agent. In order to improve the functionality of such a film, various curable resin compositions have been proposed as coating agents.

[0003] As a coating agent containing a curable resin composition, for example, Patent Document 1 proposes an active energy ray-curable composition mainly composed of urethane (meth) acrylate obtained by reacting a polyol, a polyether polyol, a polyisocyanate, and a (meth) acrylate having a hydroxyl group. Since the coating agent composed of such a composition is urethane-based, it is considered that a film excellent in crack resistance and stretchability can be formed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, it has also been carried out to coat a urethane-based primer layer using a coating agent containing an active energy ray-curable resin composition. In this case, excellent adhesion is required for the film formed on the urethane-based primer layer.

[0006] However, as a result of the inventors' study, it has been found that conventional urethane-based coating agents have a problem that the adhesion to the urethane-based primer layer tends to decrease in a humid and hot environment (i.e., an environment at high temperature and high humidity). On the other hand, although it is possible to improve the adhesion by selecting the types of components contained in the coating agent, conversely, the transparency and refractive index may decrease. In this case, for example, it is difficult to expand to optical applications and the like, and there is a problem of limitation in applications. From such a viewpoint, there has been a demand for a coating agent that has excellent adhesion to the urethane-based primer layer even in a humid and hot environment and can form a film having high transparency and a high refractive index.

[0007] The present invention has been made in view of the above, and an object thereof is to provide a coating agent and a film for a urethane-based primer that can form a film having excellent adhesion to the urethane-based primer layer even in a humid and hot environment and can also form a film having high transparency and a high refractive index.

Means for Solving the Problems

[0008] As a result of intensive studies to achieve the above object, the inventors have found that the above object can be achieved by using a specific oligomer, aromatic urethane acrylate, and polyfunctional acrylic compound as essential components, and have completed the present invention.

[0009] That is, the present invention includes, for example, the subjects described in the following items. Item 1 An optical coating agent used for coating a urethane-based primer layer, The following component (A), component (B), and component (C) (A) component; an oligomer and, (B) component; an aromatic urethane acrylate and, (C) Component; one or more selected from the group consisting of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate, and a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate, and contains at least The oligomer has a weight average molecular weight of 700 or more and 1500 or less, and has a radically polymerizable double bond site and a bisphenol site in the molecule, and is an optical coating agent. Item 2 The oligomer has a group derived from an epoxy group or a glycidyl group in the molecule, and is the optical coating agent according to Item 1. Item 3 The aromatic urethane acrylate has two or more acryloyl groups in the molecule, and is the optical coating agent according to Item 1 or 2. Item 4 A urethane-based primer film containing a cured product of the optical coating agent according to any one of Items 1 to 3. Item 5 Use of the optical coating agent according to any one of Items 1 to 3 for a urethane-based primer. Item 6 A method for using a coating agent or a method for forming a film, comprising a step of forming a film on a urethane-based primer layer using the optical coating agent according to any one of Items 1 to 3.

Advantages of the Invention

[0010] The coating agent of the present invention can form a film having excellent adhesion to a urethane-based primer layer even in a wet and hot environment, and can also form a film having high transparency and a high refractive index.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described in detail. In this specification, the expressions "containing" and "including" include the concepts of "containing", "including", "substantially consisting of", and "consisting only of".

[0012] In the numerical ranges described step by step in this specification, the upper limit value or the lower limit value of a numerical range at a certain step can be arbitrarily combined with the upper limit value or the lower limit value of the numerical range at other steps. In the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples or the value that can be uniquely derived from the examples. Also, in this specification, the numerical values connected by "~" mean a numerical range including the numerical values before and after "~" as the lower limit value and the upper limit value.

[0013] The optical coating agent of the present invention is an optical coating agent used for coating on a urethane-based primer layer, and comprises the following components (A), (B), and (C). Component (A); an oligomer, and Component (B); an aromatic urethane acrylate, and Component (C); at least one selected from the group consisting of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate, and a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate, and contains at least these. Here, the oligomer has a weight average molecular weight of 700 or more and 1500 or less, and has a radically polymerizable double bond site and a bisphenol site in the molecule.

[0014] By using the optical coating agent of the present invention (hereinafter, sometimes simply referred to as "the coating agent of the present invention" or "the coating agent"), a film can be formed on the urethane-based primer layer. The coating agent of the present invention can form a film excellent in adhesion to the urethane-based primer layer even in a wet-heat environment by containing the aforementioned components (A), (B), and (C), and can also form a film having high transparency and a high refractive index. In particular, the haze of the film formed by the coating agent hardly changes even when the film is placed in a wet-heat environment.

[0015] (A) component (A) component is an oligomer having a weight average molecular weight (Mw) of 700 or more and 1500 or less, and having a radically polymerizable double bond site and a bisphenol site in the molecule.

[0016] When the weight average molecular weight of the oligomer is 700 or more and 1500 or less, the film obtained from the coating agent is excellent in adhesion to the urethane-based primer layer even in a wet heat environment, and also has high transparency and a high refractive index. When the weight average molecular weight of the oligomer is less than 700, the film obtained from the coating agent has low adhesion to the urethane-based primer layer in a wet heat environment. When the weight average molecular weight of the oligomer exceeds 1500, the haze of the film increases and the transparency decreases.

[0017] The weight average molecular weight of the oligomer is preferably 800 or more, more preferably 850 or more, still more preferably 900 or more, and particularly preferably 950 or more. Also, the weight average molecular weight of the oligomer is preferably 1400 or less, more preferably 1300 or less, still more preferably 1250 or less, and particularly preferably 1200 or less.

[0018] The weight average molecular weight of the oligomer is the polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC) method. There is no particular limitation on the GPC apparatus used in the GPC method, and a commercially available GPC measuring machine can be used. Specific measurement conditions are as follows. Column: Shodex OHPak SB-806M HQ Column temperature: 50 °C Detector: Differential refractive index detector RID-20A (Shimadzu Corporation) Flow rate: 0.5 ml / min In addition, when the manufacturer's guaranteed value or measured value of the weight average molecular weight of the oligomer is known, that value can also be adopted as the weight average molecular weight of the oligomer.

[0019] In the oligomer, examples of the radically polymerizable double bond site include a (meth)acryloyl group. In the present specification, “(meth)acrylic” means “acrylic” or “methacrylic”, “(meth)acrylate” means “acrylate” or “methacrylate”, and “(meth)allyl” means “allyl” or “methallyl”.

[0020] The oligomer preferably has two or more radically polymerizable double bond sites. In this case, the hardness of the film obtained from the coating agent is within an appropriate range, and it becomes more suitable as a film for the urethane-based primer layer. The number of radically polymerizable double bond sites in the oligomer is preferably 5 or less, more preferably 4 or less, still more preferably 3 or less, and particularly preferably 2.

[0021] The radically polymerizable double bond site is preferably bonded, for example, by a covalent bond to the terminal of the oligomer, and more preferably bonded by a covalent bond to both terminals.

[0022] Examples of the bisphenol site present in the oligomer include a divalent group derived from bisphenol A. The divalent group derived from bisphenol A is, for example, a group in which hydrogen atoms are removed from two hydroxyl groups of bisphenol A.

[0023] In addition to the radically polymerizable double bond site and the bisphenol site, the oligomer can have other sites. For example, the oligomer can have a group derived from an epoxy group or a glycidyl group in the molecule. In other words, the oligomer is, for example, represented by the following formula (1) ―CH2―CH(OH)―CH2― (1) a divalent group represented by, or the following formula (2) ―CH2―CH(OH)― (2) It can have a divalent group represented by in the molecule. By having a group derived from an epoxy group or a glycidyl group in the molecule, the resulting film is likely to have appropriate hardness, has better adhesion to the urethane-based primer layer even in a wet and hot environment, and is also more likely to further have high transparency and a high refractive index.

[0024] In addition, it is preferable that the oligomer does not have a urethane bond in the molecule.

[0025] The oligomer can have, for example, a structural unit represented by the following general formula (3).

[0026] [Chemical formula]

[0027] For example, the oligomer can have a (meth)acryloyl group at the terminal of the structural unit represented by the formula (3). Preferably, a group represented by the formula (1) or (2) is bonded via a covalent bond between the (meth)acryloyl group and the terminal of the structural unit represented by the formula (3).

[0028] As a specific aspect of the oligomer, a compound represented by the following general formula (4) can be mentioned. In this case, the resulting film has particularly excellent adhesion to the urethane-based primer layer even in a wet and hot environment, and the transparency and refractive index are particularly likely to increase.

[0029] [Chemical formula]

[0030] (A) The manufacturing method of the oligomer, which is a component, is not particularly limited. For example, well-known manufacturing methods can be widely adopted. For example, an oligomer, which is a component (A), can be manufactured by reacting an epoxy compound with an acrylic compound such as acrylic acid in the presence of a catalyst. Examples of the epoxy compound include compounds having a structural unit represented by the above formula (3) and having epoxide sites at both ends (for example, "jER1001" (registered trademark) of Mitsubishi Chemical Corporation). Examples of the catalyst include tetrabutylammonium bromide and the like.

[0031] The coating agent of the present invention can contain the component (A) alone or can contain two or more thereof.

[0032] (B) component (B) The component is aromatic urethane acrylate. When the coating agent of the present invention does not contain the component (B), the adhesion to the urethane-based primer layer in a wet and hot environment decreases, and particularly, the decrease in transparency and refractive index becomes remarkable.

[0033] The type of aromatic urethane acrylate is not particularly limited. For example, well-known aromatic urethane acrylates can be widely applied to the present invention.

[0034] Aromatic urethane acrylate is an acrylate compound having an aromatic site and a urethane bond in the molecule. That is, the aromatic urethane acrylate, which is the component (B), is a compound having a (meth)acryloyl group, an aromatic site, and a urethane bond in the molecule.

[0035] It is preferable that the aromatic urethane acrylate has two or more acryloyl groups in the molecule. In the aromatic urethane acrylate, the number of acryloyl groups is preferably at least two, more preferably at least three, preferably eight or less, more preferably six or less, and even more preferably five or less.

[0036] The molecular weight (molecular weight based on molar mass) of the aromatic urethane acrylate is preferably, for example, 1000 to 1500.

[0037] The aromatic urethane acrylate can be produced, for example, by a known production method. For example, an aromatic urethane acrylate can be obtained by reacting an alcohol compound having a hydroxyl group and an acryloyl group with an isocyanate compound. In this case, it is preferable that either one or both of the alcohol compound and the isocyanate compound have an aromatic moiety. The alcohol compound is preferably a polyhydric alcohol compound, and the isocyanate compound is preferably a polyvalent isocyanate compound. The polyhydric alcohol compound and the isocyanate compound can include a wide range of known compounds. Examples of the alcohol compound having an aromatic moiety include an epoxy ring-opened product of bisphenol A epoxy resin (for example, a compound having the same structure as the compound represented by the formula (4)) and pentaerythritol acrylate. In addition, "Sanyo Chemical Industries' Newpol BPE (registered trademark) series and Newpol BP (registered trademark) series" obtained by adding ethylene oxide or propylene oxide to bisphenol A can also be mentioned. Furthermore, polyester polyols containing terephthalic acid or isophthalic acid can be mentioned. Examples of the isocyanate compound having an aromatic moiety include 1,3-bis(isocyanatomethyl)benzene, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, tolylene diisocyanate, metaxylylene diisocyanate, tetramethylxylylene diisocyanate, and the like.

[0038] As an example of the production of the aromatic urethane acrylate, for example, a method of reacting a compound having the same structure as the compound represented by the formula (4) with a polyvalent isocyanate compound having an aromatic moiety can be mentioned. In addition, the aromatic urethane acrylate can also be produced by reacting pentaerythritol acrylate with a polyvalent isocyanate compound having an aromatic moiety.

[0039] Aromatic urethane acrylate can also be obtained from commercially available products or the like. For example, aromatic urethane acrylate “EBECRYL” of Daicel Ornex can be mentioned.

[0040] In the coating agent of the present invention, the component (B) can be contained alone or can contain two or more kinds.

[0041] (C) component (C) component is one polyfunctional acrylic compound selected from the group consisting of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate, and a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate. When the coating agent of the present invention does not contain the (C) component, the hardness of the coating film may be insufficient and it may not be possible to obtain a desired film.

[0042] In the mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate, the ratio of the two is not particularly limited, and the action of the (C) component can be exhibited at any mixing ratio. From the viewpoint of ease of availability, the content ratio of dipentaerythritol hexaacrylate is preferably 40% by mass or more, more preferably 50% by mass or more, and can be 99% by mass or less.

[0043] In the mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate, the ratio of the two is not particularly limited, and the action of the (C) component can be exhibited at any mixing ratio. From the viewpoint of ease of availability, the content ratio of pentaerythritol tetraacrylate is preferably 30% by mass or more, more preferably 40% by mass or more, and can be 99% by mass or less.

[0044] The manufacturing method of the component (C) is not particularly limited, and for example, well-known manufacturing methods can be widely adopted. Also, the component (C) can be obtained from commercially available products or the like. Examples of commercially available products of the component (C) include "KAYARAD DPHA" (registered trademark) of Nippon Kayaku Co., Ltd. and "New Frontier PET-3" (registered trademark) of Daiichi Kogyo Seiyaku Co., Ltd.

[0045] (Coating agent) The coating agent of the present invention contains the component (A), the component (B), and the component (C). Thereby, the film formed from the coating agent is excellent in adhesion to the urethane-based primer layer even in a wet and hot environment, and also has high transparency and a high refractive index.

[0046] In the coating agent of the present invention, since the components (A) and (B) have radically polymerizable double bond sites, curing occurs by heating or active energy rays, and a film can be formed on the substrate.

[0047] In the coating agent of the present invention, the content of the component (A) is preferably 15 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 25 parts by mass or more, particularly preferably 30 parts by mass or more, and preferably 70 parts by mass or less, more preferably 60 parts by mass or less, still more preferably 55 parts by mass or less, and particularly preferably 50 parts by mass or less, based on 100 parts by mass of the total mass of the components (A), (B), and (C) in terms of enhancing the adhesion of the resulting film to the urethane-based primer layer in a wet and hot environment. Note that 100 parts by mass of the total mass of the components (A), (B), and (C) means the value in terms of solid content, excluding volatile components such as solvents.

[0048] In the coating agent of the present invention, the content of component (B) is preferably 15 parts by mass or more, more preferably 20 parts by mass or more, further preferably 25 parts by mass or more, particularly preferably 30 parts by mass or more, and preferably 70 parts by mass or less, more preferably 60 parts by mass or less, further preferably 55 parts by mass or less, particularly preferably 50 parts by mass or less, based on 100 parts by mass of the total mass of components (A), (B), and (C), in terms of the adhesion and transparency to the urethane-based primer layer in a wet-heat environment of the resulting film being likely to increase.

[0049] In the coating agent of the present invention, the content of component (C) is preferably 1 part by mass or more, more preferably 5 parts by mass or more, further preferably 10 parts by mass or more, particularly preferably 15 parts by mass or more, and preferably 40 parts by mass or less, more preferably 35 parts by mass or less, further preferably 30 parts by mass or less, particularly preferably 25 parts by mass or less, based on 100 parts by mass of the total mass of components (A), (B), and (C), in terms of the haze and refractive index of the resulting film being likely to be in an appropriate range.

[0050] The coating agent of the present invention can contain components other than components (A), (B), and (C). Examples of other components include polymerization initiators, solvents, and the like.

[0051] Examples of the polymerization initiator include photoinitiators and polymerization initiators by active energy rays such as ultraviolet rays.

[0052] Examples of the photoinitiator include aromatic ketones such as benzophenone, aromatic compounds such as anthracene and α-chloromethylnaphthalene, and sulfur compounds such as diphenyl sulfide and thiocarbamate.

[0053] Examples of polymerization initiators by active energy rays such as ultraviolet rays other than visible light include acetophenone, acetophenone benzyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-1,2-diphenylethane-1-one, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, benzoin propyl ether, benzoin ethyl ether, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, thioxanthone, diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone), and the like.

[0054] Examples of commercially available products of polymerization initiators by active energy rays include Omnirad 184, 369, 651, 500, 819, 907, 784, 2959, 1000, 1300, 1700, 1800, 1850 manufactured by IGM Resins B.V., Lucirin TPO manufactured by BASF, Ubecryl P36 manufactured by UCB, Esacure KIP150, KIP100F, KT37, KT55, KTO46, TZT, KIP75LT manufactured by Fratelli Lamberti, Kayacure DETX manufactured by Nippon Kayaku Co., Ltd., and the like.

[0055] The content of the polymerization initiator varies depending on its type and the like. For example, with respect to 100 parts by mass of the total mass of components (A), (B), and (C), the content of the polymerization initiator is preferably 0.1 to 10 parts by mass, more preferably 1 to 8 parts by mass, and even more preferably 2 to 5 parts by mass.

[0056] When the coating agent contains a solvent, examples of the solvent include hydrocarbon solvents such as benzene, toluene, and xylene; ketone solvents such as acetone, methyl ethyl ketone, and isophorone; alcohol solvents such as tert-butyl alcohol, benzyl alcohol, phenoxyethanol, and phenylpropylene glycol; halogenated hydrocarbon solvents such as methylene chloride and chloroform; ether solvents such as 1,2-dimethoxyethane, tetrahydrofuran, 1,4-dioxane, and anisole; ester solvents such as ethyl acetate, propyl acetate, ethyl carbitol acetate, and butyl carbitol acetate; amide solvents such as N,N-dimethylformamide and N,N-dimethylacetamide; and the like.

[0057] The coating agent may also contain additives such as a light stabilizer, an ultraviolet absorber, a catalyst, a leveling agent, an antifoaming agent, a polymerization accelerator, an antioxidant, a flame retardant, an infrared absorber, an antistatic agent, a slip agent, a plasticizer, and a dispersant, as necessary.

[0058] The method for preparing the coating agent is not particularly limited. For example, the coating agent can be prepared by a method of mixing components (A), (B), and (C) and other components added as necessary in predetermined blending amounts.

[0059] A film can be formed using a coating agent. The method for forming the film is not particularly limited, and for example, known methods can be widely adopted. For example, a method comprising a step of forming a film on a urethane-based primer layer using an optical coating agent can be adopted. Specifically, a coating agent is applied onto the urethane-based primer layer to form a coating film, and by irradiating such a coating film with active energy rays, the coating film is cured to form a film. Therefore, the film contains a cured product of the optical coating agent of the present invention.

[0060] Examples of the active energy rays include a high-pressure mercury lamp, an electron beam, a γ-ray, a carbon arc lamp, a xenon lamp, a metal halide lamp, etc. When curing by heating, it can be cured by heating in a temperature range of 60 to 250°C.

[0061] The method for applying the coating agent onto the urethane-based primer layer is not particularly limited, and for example, known methods can be widely adopted. Specifically, examples include a method of applying the coating agent onto the urethane-based primer layer with a bar coater or the like, and a method of spraying the coating agent onto the urethane-based primer layer.

[0062] The thickness of the film formed by the coating agent is not particularly limited, and for example, it is 1 to 20 μm, preferably 2 to 10 μm.

[0063] The film formed from the coating agent of the present invention has excellent adhesion to the urethane-based primer layer even in a wet heat environment (for example, in an environment of 80°C and 90% humidity for 500 hours of wet heat treatment), and the haze hardly changes even when placed in a wet heat environment, that is, it has high transparency. Also, the film formed from the coating agent of the present invention has a high refractive index. Therefore, the optical coating agent of the present invention is suitable for use on a urethane-based primer. That is, the film formed from the coating agent (the film containing the cured product of the optical coating agent) is suitable as a film for a urethane-based primer.

[0064] The haze of the film formed by the coating agent is hardly changed even when the film is placed in a humid heat environment. For example, when the film is subjected to a humid heat treatment for 500 hours in an environment of 80°C and 90% humidity, the amount of change in haze before and after the humid heat treatment is preferably 2.5 or less, more preferably 2 or less, and even more preferably 1.5 or less.

[0065] The refractive index of the film formed by the coating agent is preferably 1.555 or more, for example, from the viewpoint of being suitably used for optical applications.

[0066] The type of the urethane-based primer for forming the film with the coating agent is not particularly limited, and known urethane-based primers can be widely adopted. Specific examples of the urethane-based primer include known aqueous urethane-based primers, solvent-based urethane-based primers, ultraviolet curable urethane-based primers, and the like. As the method for producing the urethane-based primer layer, for example, known methods can be widely adopted. Specifically, there is a method of coating the urethane-based primer on a substrate so as to have a desired thickness and drying it. The substrate is not particularly limited, and various films and optical displays used as optical members can be widely exemplified.

[0067] The thickness of the urethane-based primer layer is not particularly limited, and can be, for example, in the range of 0.1 to 5 μm from the viewpoint of optical functions.

[0068] The coating agent of the present invention is suitable for optical applications. For example, the member on which the film formed from such a coating agent is formed is preferably an optical member such as an optical film or an optical display. The optical member is incorporated into, for example, a display device. Examples of the display device include a liquid crystal display, a plasma display, and an organic EL display.

[0069] In identifying the inventions encompassed by the present disclosure, the respective configurations (properties, structures, functions, etc.) described in each embodiment of the present disclosure may be combined in any manner. That is, the present disclosure encompasses all the subject matters consisting of any combinations of the respective combinable configurations described herein.

Example

[0070] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to the aspects of these examples.

[0071] (Raw materials) In each of the examples and comparative examples, the following were used as raw materials for preparing the coating agent.

[0072] (A) component; oligomer Oligomer A-1 was prepared by the following method. First, 72 parts by weight of acrylic acid, 0.55 parts by weight of 4-methoxyphenol as a polymerization inhibitor, 4 parts by weight of tetrabutylammonium bromide as a catalyst, and 234 parts by weight of toluene were added to 475 parts by weight of "jER1001 (registered trademark)" manufactured by Mitsubishi Chemical Corporation in a flask equipped with a thermometer, a stirrer, and a water-cooled condenser, and the reaction was carried out at a reaction temperature of 95 to 110°C until the epoxy equivalent became 10,000 or more to obtain a solution containing oligomer A-1 (solid content concentration: 70% by mass). The weight average molecular weight of oligomer A-1 was 1000.

[0073] (Comparative oligomer 1) Oligomer a-1 was prepared by the following method. First, 72 parts by weight of acrylic acid, 2 parts by weight of 4-methoxyphenol as a polymerization inhibitor, 15 parts by weight of tetrabutylammonium bromide as a catalyst, and 877 parts by weight of toluene were added to 1975 parts by weight of "jER1007 (registered trademark)" manufactured by Mitsubishi Chemical Corporation in a flask equipped with a thermometer, a stirrer, and a water-cooled condenser, and the reaction was carried out at a reaction temperature of 95 to 110°C until the epoxy equivalent became 20,000 or more to obtain a solution containing oligomer a-1 (solid content concentration: 70% by mass). The weight average molecular weight of oligomer a-1 was 3000.

[0074] (Comparative oligomer 2) Oligomer a-2 was prepared by the following method. First, 72 parts by weight of acrylic acid, 0.26 parts by weight of 4-methoxyphenol as a polymerization inhibitor, and 1.3 parts by weight of tetrabutylammonium bromide as a catalyst were added to 189 parts by weight of "jER828 (registered trademark)" manufactured by Mitsubishi Chemical Corporation in a flask equipped with a thermometer, a stirrer, and a water-cooled condenser. The reaction was carried out at a reaction temperature of 95 to 110 °C until the epoxy equivalent became 10,000 or more, and the resulting solution containing oligomer a-2 (solid content concentration: 70 mass%) was diluted with 112 parts by weight of methyl ethyl ketone. The weight average molecular weight of oligomer a-2 was 500.

[0075] (B) component; aromatic urethane acrylate Aromatic urethane acrylate B-1 was prepared by the following method. First, 72 parts by weight of acrylic acid, 0.52 parts by weight of 4-methoxyphenol as a polymerization inhibitor, and 1.3 parts by weight of tetrabutylammonium bromide as a catalyst were added to 189 parts by weight of "jER828 (registered trademark)" manufactured by Mitsubishi Chemical Corporation in a flask equipped with a thermometer, a stirrer, and a water-cooled condenser. The reaction was carried out at a reaction temperature of 95 to 110 °C until the epoxy equivalent became 10,000 or more. Next, 47 parts by weight of an aromatic isocyanate "Takenate 500 (trademark registration)" manufactured by Mitsui Chemicals, Inc. and 135 parts by weight of methyl isobutyl ketone were added, and the reaction was carried out at a reaction temperature of 50 to 70 °C until the free isocyanate content became 0.1% or less, to obtain a solution containing aromatic urethane acrylate B-1 (solid content concentration: 70 mass%).

[0076] Aromatic urethane acrylate B-2 was prepared by the following method. First, 1151 parts by weight of acrylic acid, 604 parts by weight of pentaerythritol (manufactured by Koei Chemical Industry Co., Ltd.), 43.9 parts by weight of p-toluenesulfonic acid, 2.1 parts by weight of 4-methoxyphenol as a polymerization inhibitor, and 552 parts by weight of toluene were added to a flask equipped with a thermometer, a stirrer, and a water-cooled condenser and mixed. Then, while blowing air under reduced pressure and maintaining the reaction temperature at about 100 °C, the reaction was carried out until 75% of all the hydroxyl groups in pentaerythritol were esterified. The reaction was carried out while removing the condensed water. After the reaction was completed, 353 parts by weight of toluene was added. Neutralization treatment was carried out by adding a 20% by weight aqueous sodium hydroxide solution corresponding to 1.1 times the molar amount of the acid content of the reaction solution to which this toluene was added while stirring, thereby removing excess acrylic acid and p-toluenesulfonic acid. Then, the organic layer was separated, and a water washing treatment was carried out by adding 10 parts by weight of water to 100 parts by weight of the organic layer while stirring. Then, the organic layer was separated again, and toluene was distilled off by heating under reduced pressure. The obtained pentaerythritol acrylate was 837 parts by weight, and the hydroxyl value was 190 mgKOH / g. Next, 190.5 parts by weight of an aromatic isocyanate "Takenate 500 (trademark registration)" manufactured by Mitsui Chemicals, Inc. and 440 parts by weight of methyl ethyl ketone were added to 837 parts by weight of the obtained pentaerythritol acrylate having a hydroxyl value of 190 mgKOH / g, and the reaction was carried out at a reaction temperature of 50 to 70 °C until the free isocyanate content became 0.1% or less, to obtain a solution (solid content concentration 70 mass%) containing aromatic urethane acrylate B-2.

[0077] (Comparative urethane acrylate) The aliphatic urethane acrylate b-1 was prepared by the following method. First, 24.6 parts by weight of polycaprolactone diol "Placcel 205" manufactured by Daicel Corporation, 16.3 parts by weight of trifunctional polyether polyol "DK Polyol G-480" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., and 41.3 parts by weight of isophorone diisocyanate were added to a flask equipped with a thermometer, a stirrer, and a water-cooled condenser, and reacted at a reaction temperature of 70 to 80 °C until a predetermined free isocyanate content was reached. Next, 0.05 part by weight of 4-methoxyphenol, which is a polymerization inhibitor, and 17.8 parts by weight of 2-hydroxyethyl acrylate were added, and the reaction was carried out at a reaction temperature of 70 to 80 °C until the free isocyanate content became 0.1% or less. Then, 43 parts by weight of methyl ethyl ketone was added to obtain a solution (solid content concentration: 70 mass%) containing aliphatic urethane acrylate b-1.

[0078] (C) component; polyfunctional acrylic compound ·C-1; Dipentaerythritol acrylate (Nippon Kayaku Co., Ltd. "KAYARAD DPHA" (registered trademark)) = a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate ·C-2; Pentaerythritol acrylate (Dai-ichi Kogyo Seiyaku Co., Ltd. "New Frontier PET-3" (registered trademark)) = a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate

[0079] (Example 1) The raw materials shown in Example 1 of the formulation table in Table 1 were selected to prepare a coating agent. Specifically, 100 parts by weight of a mixture was prepared by mixing 40 parts by weight of oligomer A-1 as component (A), 40 parts by weight of aromatic urethane acrylate B-1 as component (B), and 20 parts by weight of C-1 as component (C) in terms of solid content conversion value. To this mixture, 4 parts by weight of Omnirad 184 (IGM Resins B.V.) as a polymerization initiator and 57 parts by weight of methyl ethyl ketone as a solvent were mixed to obtain a coating agent having a concentration of 50 mass%.

[0080] (Example 2) As the component (B), a coating agent with a concentration of 50% by mass was obtained in the same manner as in Example 1, except that it was changed to aromatic urethane acrylate B-2 as shown in Table 1.

[0081] (Example 3) As the component (C), a coating agent with a concentration of 50% by mass was obtained in the same manner as in Example 1, except that it was changed to C-2 as shown in Table 1.

[0082] (Example 4) As shown in Table 1, a coating agent with a concentration of 50% by mass was obtained in the same manner as in Example 1, except that the oligomer A-1 was changed to 60 parts by mass as the component (A) and the aromatic urethane acrylate B-1 was changed to 20 parts by mass as the component (B).

[0083] (Example 5) As shown in Table 1, a coating agent with a concentration of 50% by mass was obtained in the same manner as in Example 1, except that the oligomer A-1 was changed to 20 parts by mass as the component (A) and the aromatic urethane acrylate B-1 was changed to 60 parts by mass as the component (B).

[0084] (Example 6) As shown in Table 1, a coating agent with a concentration of 50% by mass was obtained in the same manner as in Example 1, except that the oligomer A-1 was changed to 50 parts by mass as the component (A) and C-1 was changed to 10 parts by mass as the component (C).

[0085] (Example 7) As shown in Table 1, a coating agent with a concentration of 50% by mass was obtained in the same manner as in Example 1, except that the oligomer A-1 was changed to 30 parts by mass as the component (A) and C-1 was changed to 30 parts by mass as the component (C).

[0086] (Comparative Example 1) As the component (A), a coating agent with a concentration of 50% by mass was obtained in the same manner as in Example 1, except that it was changed to oligomer a-1 as shown in Table 1.

[0087] (Comparative Example 2) (A) As a component, a coating agent with a concentration of 50% by mass was obtained in the same manner as in Example 1, except that it was changed to oligomer a-2 as shown in Table 1.

[0088] (Comparative Example 3) (B) As a component, a coating agent with a concentration of 50% by mass was obtained in the same manner as in Example 1, except that it was changed to aliphatic urethane acrylate b-1 as shown in Table 1.

[0089] (Preparation of Film) Using the coating agents prepared in each example and comparative example, a film was formed on the urethane-based primer layer by the following procedure. First, for the urethane-based primer, a one-sided corona discharge-treated PET substrate (Lumirror T60, manufactured by Toray Industries, Inc.) was prepared as the substrate. The urethane-based primer solution was applied onto the untreated surface of this PET substrate with a bar coater to a dry film thickness of 2 - 8 μm, pre-dried at 80°C for 10 minutes, and then dried at 150°C for 10 minutes to form a urethane primer layer. The urethane-based primer solution was prepared by mixing 36 parts by weight of Elastron H-15 (a heat-reactive urethane aqueous dispersion, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), 2 parts by weight of a 5% aqueous sodium hydrogen carbonate solution, 1 part by weight of Elastron CAT-21 (a thermal polymerization catalyst), and 61 parts by weight of dilution water, and the pH was adjusted to about 6. Next, the coating agents prepared in each example and comparative example were applied onto the urethane-based primer layer in a dry state so that the film thickness was about 4 - 7 μm to form a coating film. Then, using a high-pressure mercury lamp of 80 W / cm 2 and with an integrated illuminance of 150 mJ / cm 2 the coating film was cured by irradiating with ultraviolet rays in a nitrogen atmosphere, thereby forming a film containing a cured product of the coating agent on the urethane-based primer.

[0090] (Evaluation Method) <Humid Heat Adhesion> The damp heat adhesion was evaluated based on the 2 mm cross-cut test conducted in accordance with JIS K5400-8.5:1990. Specifically, the film obtained in the above-mentioned "film preparation" was subjected to damp heat treatment by storing it in an environment with a temperature of 80 °C and a humidity of 90% for 500 hours. After this damp heat treatment, the residual rate of the film with respect to the PET substrate was calculated using the following formula Residual rate (%) = 100 - (number of peeled squares) The damp heat adhesion was evaluated based on the calculated residual rate according to the following criteria ≪Judgment criteria≫ A: Residual rate is 100% B: Residual rate is 95% or more and less than 100% C: Residual rate is 90% or more and less than 95% D: Residual rate is less than 90%

[0091] <Damp heat resistance of haze> The haze of the obtained film was measured using a turbidimeter (manufactured by Nippon Denshoku Industries Co., Ltd., model NDH4000) in accordance with JIS K 7136:2000. The change in haze before and after the above-mentioned damp heat treatment was calculated, and the damp heat resistance of the haze was evaluated according to the following criteria ≪Judgment criteria≫ A: Less than Δ1.5, and the damp heat resistance was significantly excellent B: Δ1.5 or more and less than 2.0, and the damp heat resistance was excellent C: Δ2.0 or more and less than Δ2.5, and the damp heat resistance deteriorated D: Δ2.5 or more, and the damp heat resistance significantly deteriorated

[0092] <Refractive index> The refractive index of the obtained film at a wavelength of 589 nm was measured using a refractive index measuring device (product name: prism coupler) manufactured by Metricon Corporation. Based on the obtained refractive index value, the evaluation was performed according to the following judgment criteria ≪Judgment criteria≫ A: 1.560 or more B: 1.555 or more and less than 1.560 C: 1.550 or more and less than 1.555 D: Less than 1.550

[0093] Table 1 shows the formulation conditions of the coating agents prepared in each example and comparative example, and the evaluation results of the humidity-heat adhesion, haze, and film refractive index of the obtained films. Note that the blanks in the formulation conditions in Table 1 mean that the raw materials are not used.

[0094] From Table 1, since the coating agents obtained in the examples contain the components (A), (B), and (C), it was possible to form films having excellent adhesion to the urethane-based primer layer even in a humidity-heat environment. It was also shown that the coating agents obtained in the examples can form films having high transparency and a high refractive index.

[0095] [Table 1]

Claims

1. An optical coating agent used for coating a urethane-based primer layer, comprising the following components (A), (B), and (C): Component (A); an oligomer, Component (B); an aromatic urethane acrylate, Component (C); one or more selected from the group consisting of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate, and a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate, and containing at least The oligomer has a weight average molecular weight of 700 or more and 1500 or less, and has a radically polymerizable double bond site and a bisphenol site in the molecule, an optical coating agent.

2. The oligomer has a group derived from an epoxy group or a glycidyl group in the molecule, the optical coating agent according to claim 1.

3. The aromatic urethane acrylate has two or more acryloyl groups in the molecule, the optical coating agent according to claim 1.

4. A urethane-based primer film containing a cured product of the optical coating agent according to any one of claims 1 to 3.

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