JP2017066169A - Hard coat film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hard coat film having excellent transparency and smoothness while having excellent hardness and curl inhibitory effect.SOLUTION: A hard coat film has a hard coat layer applied on at least one side of a transparent film, the hard coat layer comprising a hard coat paint composition that comprises an ionizing radiation-curable resin, a silica fine particle, and a solvent, wherein the solvent comprises a ketone solvent of 20 wt.% or more.SELECTED DRAWING: None

Description

The present invention relates to a hard coat film. More specifically, the present invention relates to a hard coat film that can be used as a protective film for liquid crystal display devices, CRT display devices, plasma display devices, EL display devices, touch panels, and the like.

  For a polarizing plate used in a liquid crystal display or a touch panel display, a hard coat film having a hard coat layer and a triacetyl cellulose which is a transparent film as a protective film is used.

  In recent years, with the thinning of liquid crystal displays and touch panel displays, thinner hard coat films have been used. However, since the transparent film also becomes thinner due to the thinning of the hard coat film, it is more difficult than before to form both the hardness and the curl when forming the hard coat layer.

  Patent Document 1 discloses a hard coat film in which silica fine particles are contained in a hard coat layer in order to achieve both hardness and curl.

JP 2010-082860

  However, when silica fine particles are contained in the hard coat paint, the appearance of the silica is reduced due to the aggregation of the silica fine particles and the unevenness of the repellency is generated. For applications that require transparency and smoothness such as liquid crystal displays. There was a problem that it was not suitable.

  Then, this invention aims at providing the hard coat film excellent in transparency and smoothness, while having favorable hardness and curl suppression effect.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors applied a hard coat coating composition containing an ionizing radiation curable resin, silica fine particles, and a solvent to at least one surface of the transparent film. A hard coat film having a hard coat layer, wherein the solvent contains a ketone solvent in an amount of 20% by weight or more. The invention has been reached.

  According to the present invention, a hard coat film excellent in transparency and smoothness can be obtained while having good hardness and curling suppression effect.

That is, this invention is following (1)-(6).
(1) A hard coat film having a hard coat layer formed by coating a hard coat coating composition containing an ionizing radiation curable resin, silica fine particles, and a solvent on at least one surface of a transparent film, A hard coat film, wherein the solvent contains a ketone solvent in an amount of 20% by weight or more.
(2) The hard coat film as described in (1), wherein the ketone solvent uses at least one of methyl ethyl ketone, methyl isobutyl ketone, propylene glycol monomethyl ether, diacetone alcohol, acetone, and cyclohexanone.
(3) The hard coat film according to any one of (1) to (2), wherein the hard coat coating composition contains a fluorine-based leveling agent.
(4) The hard coat film according to any one of (1) to (3), wherein the transparent film is a triacetylcellulose film.
(5) The ionizing radiation curable resin used in the hard coat paint contains at least one resin selected from urethane (meth) acrylate, epoxy (meth) acrylate, or (meth) acrylate. The hard coat film according to any one of (1) to (4).
(6) The hard coat film according to any one of (1) to (5), wherein a coating amount of the hard coat layer is in a range of 3.0 to 20.0 g / m 2.

  Hereinafter, the present invention will be described in detail. Unless otherwise specified, the description “1 to 100 nm” and the like shown in the present invention refers to 1 nm to 100 nm.

  The transparent film that can be used in the present invention is not particularly limited, and examples thereof include triacetyl cellulose, polyethylene terephthalate, cycloolefin polymer, polycarbonate, polyethylene naphthalate, polyethylene, polytrimethylene terephthalate, polypropylene, and polybutylene terephthalate. Polybutylene naphthalate, polystyrene, polymethyl methacrylate, polystyrene glycidyl methacrylate, and mixtures thereof can be exemplified, but polyethylene terephthalate, polyethylene naphthalate, and triacetyl cellulose are heated from the viewpoint of heat resistance, availability, and economy. It is preferably used as a raw material for the plastic resin film.

  In the present invention, the thickness of the transparent film is appropriately selected according to the use for which the hard coat film is used, but it is preferably 10 to 250 μm, more preferably 10 to 150 μm, in view of mechanical strength and handling properties. Preferably, 10-100 micrometers is more preferable.

  The ionizing radiation curable resin that can be used in the present invention is not particularly limited as long as it is a transparent resin that is cured by irradiating an electron beam or ultraviolet rays. Epoxy (meth) acrylate, urethane (meth) (Meth) acryloyl in the molecule such as acrylate, polyester (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol poly (meth) acrylate, etc. What has group is preferable, and what consists of either of these may be used individually by 1 type, and may mix and use 2 or more types.

  The silica fine particles of the present invention are not particularly limited as long as they are contained in the hard coat layer and contribute to improvement in hardness and reduction in curing shrinkage, but the contained hard coat layer can maintain high transparency. The primary particle size is preferably 1 to 100 nm. If the primary particle size is less than 1 nm, the hardness cannot be obtained. When the primary particle size exceeds 100 nm, the transparency is lowered.

  10-70 weight part is preferable with respect to 100 weight part of hard coat coating compositions, and, as for content of the silica fine particle of this invention, 20-70 weight part is more preferable. When the silica fine particle exceeds 70 parts by weight with respect to the hard coat coating composition, the dispersibility with respect to the solvent is inferior, and since the resin content is small, the adhesion of the hard coat layer decreases. Further, when the silica fine particles are less than 10 parts by weight with respect to the hard coat coating composition, good hardness cannot be obtained.

The hard coat coating composition of the present invention preferably has a solid content (solid content concentration) of 10 to 80% by weight, mainly 10 to 70% by weight, mainly composed of an ionizing radiation curable resin or silica fine particles. More preferred is 20 to 70% by weight. If the solid content concentration is 10% by weight or less, the solvent ratio in the hard coat coating composition becomes too high, and a large amount of drying energy is required at the time of coating. On the other hand, when the solid content concentration is 80% by weight or more, the viscosity of the hard coat coating composition becomes strong, and the dispersion of the silica fine particles is not easily uniform.

  It is important that the solvent (solvent) in the hard coat coating composition of the present invention contains a ketone solvent in an amount of 20% by weight or more, preferably 40 to 95% by weight, more preferably 60 to 95% by weight. If the ketone solvent is less than 20% by weight, the silica fine particles in the paint aggregate in the coating drying process, and the silica fine particles become a lump larger than the wavelength of visible light. Therefore, the transparency and smoothness of the hard coat film are improved. descend.

  The ketone solvent refers to an organic compound represented by a structural formula of R 1 -C (═O) —R 2 (where R 1 and R 2 are alkyl groups, etc.) that are liquid at normal temperature and pressure. Examples of such a material include methyl ethyl ketone, methyl isobutyl ketone, propylene glycol monomethyl ether, diacetone alcohol, acetone, and cyclohexanone, and these can be used alone or in appropriate combination of several kinds.

  As the solvent (solvent) used in the hard coat coating composition of the present invention, a solvent other than the ketone solvent can be used as long as the effects of the present invention are not impaired. Such a solvent can be appropriately selected according to the solubility of the resin, and may be any solvent that can uniformly dissolve or disperse at least a solid content (resin, polymerization initiator, other additives), such as toluene, Aromatic solvents such as xylene and n-heptane, aliphatic solvents such as cyclohexane, methylcyclohexane and ethylcyclohexane, ester solvents such as methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate and methyl lactate, methanol Well-known organic solvents such as alcohol solvents such as ethanol, isopropyl alcohol, and n-propyl alcohol can be used alone or in appropriate combination with ketone solvents.

  In this invention, it is preferable that the coating amount of a hard-coat layer exists in the range of 3.0-20.0 g / m2. If the coating amount is less than 3.0 g / m 2, the pencil hardness is not preferable. On the other hand, if the coating amount is more than 20.0 g / m 2, the curl of the hard coat film is strong and easily becomes a cylindrical curl, which is not preferable. In other words, by setting the coating amount in the range of 3.0 to 20.0 g / m 2, both the pencil hardness and curl of the hard coat film can be achieved.

  In the present invention, a leveling agent can be used to improve the coatability of the hard cord coating composition. Examples of the leveling agent include, but are not limited to, fluorine-based, acrylic-based, and siloxane-based leveling agents. In particular, a fluorine-based fluorine-containing group such as a perfluoroalkyl group is excellent in leveling adjustment function. It is preferable to use a leveling agent. Examples of such a product include Mega-Fac RS-75 (manufactured by DIC Corporation).

  In the present invention, the hard coat layer has a non-reactive or radically polymerizable (meth) acryloyloxy group-containing UV absorber for the purpose of imparting light resistance (adhesion after exposure, etc.), Addition of benzophenone UV absorber is possible. The addition amount is preferably 0.05 to 10.0 parts by weight with respect to 100 parts by weight of the ionizing radiation curable resin. Particularly preferred is 1.0 to 5.0 parts by weight.

  In the present invention, the hard coat paint for forming the hard coat layer may contain a photopolymerization initiator, a light stabilizer, a thermosetting resin, an antifoaming agent, etc., as long as the effects of the present invention are not impaired. It can be contained.

  In order to apply the hard coat paint onto the film, any known coating method can be used. For example, the reverse coating method, the gravure coating method, the bar coating method, the die coating method, the spray coating method, the kiss coating method, the wire bar coating method, the curtain coating method, etc. may be mentioned, and these methods may be used alone or in combination. Good. The electron beam for curing the hard coat layer, the irradiation conditions of ultraviolet rays, etc. may be appropriately adjusted according to the electron beam curable resin to be used and other various chemicals to be added. In the present invention, in order to improve the surface strength (scratch resistance, etc.), it is preferable to irradiate ionizing radiation under conditions where nitrogen gas is enclosed and the oxygen concentration is 1000 ppm or less.

  In the present invention, it is presumed that the hard coat layer exhibits excellent hardness and transparency as follows. Since ketone solvents have higher affinity for both silica fine particles and ionizing radiation curable resins than ester and alcohol solvents, the dispersion stability of silica fine particles does not decrease during the paint drying process and is high. It is considered that transparency and high hardness can be obtained.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples.

<Example 1>
Electro-radiation curable resin dipentaerythritol hexaacrylate (trade name: NK ester A-9550; manufactured by Shin-Nakamura Chemical Co., Ltd.) 32.0 parts by weight on one side of a triacetylulose film (product name: KC2UAW, thickness: 25 μm), silica Fine particle dispersion (trade name; NANOBYK-3605 (silica content 50%), manufactured by Big Chemie Japan, particle size 20 to 25 nm) 28.0 parts by weight, photopolymerizer 1-hydroxy-cyclohexyl-phenyl-ketone (trade name) Irgacure 184, manufactured by company) 1.5 parts by weight, leveling fluorine-based compound (trade name; MegaFac RS-75), DIC Corporation) 0.5 parts by weight, ketone solvent methyl ethyl ketone 23 parts by weight, Hard coat obtained by mixing with 15 parts by weight of propylene glycol monomethyl ether and stirring. The coating layer coating was applied using a bar coater and dried in a drying furnace at 80 ° C. to form a coating layer having a coating amount of 7.0 g / m 2. This was cured at a UV irradiation amount of 200 mJ / cm 2 using a UV irradiation apparatus set at a height of 60 mm from the coated surface to prepare a hard coat film having a hard coat layer.

<Example 2>
A hard coat film was produced in the same manner as in Example 1 except that 35 parts by weight of methyl ethyl ketone and 3 parts by weight of propylene glycol monomethyl ether were used.

<Example 3>
A hard coat film was produced in the same manner as in Example 1 except that methyl ethyl ketone in Example 1 was changed to methyl isobutyl ketone.

<Example 4>
A hard coat film was produced in the same manner as in Example 1 except that the hard coat layer of Example 1 was changed to 18 g / m 2.

<Example 5>
A hard coat film was prepared in the same manner as in Example 1 except that 37 parts by weight of dipentaerythritol hexaacrylate of Example 1, 18 parts by weight of silica fine particle dispersion, and 28 parts by weight of methyl ethyl ketone were used.

<Example 6>
A hard coat film was produced in the same manner as in Example 1 except that the triacetylcellulose film of Example 1 was changed to a PET film (product name: HPE-25, thickness: 25 μm).

<Example 7>
A hard coat film was produced in the same manner as in Example 1 except that dipentaerythritol hexaacrylate of Example 1 was changed to urethane acrylate trade name; U-15HA; manufactured by Shin-Nakamura Chemical Co., Ltd.

<Comparative Example 1>
A hard coat film was produced in the same manner as in Example 1 except that methyl ethyl ketone in Example 1 was changed to ethyl acetate.

<Comparative example 2>
A hard coat film was produced in the same manner as in Example 1 except that methyl ethyl ketone in Example 1 was changed to isopropyl alcohol.

<Comparative Example 3>
A hard coat film was produced in the same manner as in Example 4 except that 10 parts by weight of methyl ethyl ketone and 28 parts by weight of propylene glycol monomethyl ether were used.

  The hard coat films obtained in Examples and Comparative Examples were evaluated by the following methods.

<Evaluation of pencil hardness>
Based on JIS-K5600-5-4, the pencil hardness of the hard coat layer was implemented.
◎: Pencil hardness 4H or more ○: Pencil hardness 3H
Δ: Pencil hardness 2H-3H
X: Pencil hardness 2H

<Evaluation of curls>
The produced hard coat film was cut into a size of width × length = 20 cm × 25 cm, and the floating of the four corners when measured on a flat plate in a temperature 20 ° C. and relative humidity 60% environment was measured. The average value was the curl height. The lower the value, the higher the curl suppression effect.

<Total light transmittance, haze value>
Based on JIS K 7105, the measurement was performed using a haze meter “HM150” manufactured by Murakami Color Research Laboratory.

<Transparency>
The surface of the hard coat layer of the hard coat film was tilted by 45 degrees under a fluorescent lamp and visually confirmed.
○: Transparent and good appearance.
Δ: The observation surface is slightly whitish and the appearance is deteriorated, but there is no practical problem.
X: The observation surface is generally whitish and the appearance is deteriorated.

<Smoothness>
The surface of the hard coat layer of the hard coat film was tilted by 45 degrees under a fluorescent lamp and visually confirmed.
○: Smoothness and good appearance.
Δ: Slight irregularities are observed and the smoothness is inferior, but there is no practical problem.
X: There are unevenness on the whole, and the appearance deteriorates.

  As shown in Table 1, since the hard coat film satisfying the present invention can continue to uniformly disperse the silica fine particles containing the ketone solvent and the leveling agent before and after the hard coat layer is cured, the hardness and curl reducing property, and Appearance (transparency and smoothness) is good and suitable for use in liquid crystal displays and the like.

  On the other hand, as shown in Comparative Examples 1 to 3, it is clear that the hard coat film which does not contain a ketone solvent or whose ketone organic solvent is outside the scope of the present invention is inferior in hardness and appearance.

Claims (6)

  A hard coat film having a hard coat layer formed by coating a hard coat coating composition containing an ionizing radiation curable resin, silica fine particles, and a solvent on at least one surface of a transparent film, A hard coat film comprising a ketone solvent in an amount of 20% by weight or more.   The hard coat film according to claim 1, wherein the ketone solvent uses at least one of methyl ethyl ketone, methyl isobutyl ketone, propylene glycol monomethyl ether, diacetone alcohol, acetone, and cyclohexanone.   The hard coat film according to claim 1, wherein the hard coat coating composition contains a fluorine-based leveling agent.   The hard coat film according to claim 1, wherein the transparent film is a triacetyl cellulose film.   The ionizing radiation curable resin used in the hard coat paint contains at least one resin selected from urethane (meth) acrylate, epoxy (meth) acrylate, or (meth) acrylate. Item 5. The hard coat film according to any one of Items 1 to 4.   The hard coat film according to any one of claims 1 to 5, wherein a coating amount of the hard coat layer is in a range of 3.0 to 20.0 g / m2.