JP2018132665A - Hard coat film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hard coat film that offers superior adhesion, durability, processability, and visibility among other things.SOLUTION: A hard coat film 10 comprises a hard coat layer 3 containing an ionizing radiation-curable resin that is laminated on at least one surface of a cycloolefin film 1 having a thickness of 30 μm or less via an adhesive layer 2 containing a mixture of a polyolefin resin and styrene acrylic resin. The hard coat film satisfies conditions (A) and (B) as described below. (A): bvalue should be 1.5 or less. (B): a residual ratio of the hard coat layer should be 90% or greater as measured by the cross-cut method after irradiating the film with ultraviolet rays at irradiance of 500 W/mfor an irradiation period of 100 hours in an environment with a temperature of 43 degrees and humidity of 50%RH.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hard coat film used for an optical member.

  For example, a display surface of a liquid crystal display such as a liquid crystal display device (LCD) is required to be provided with scratch resistance so that the surface is not damaged due to scratches during handling. Therefore, it is common practice to impart scratch resistance to the display surface of a display using a hard coat film in which a hard coat layer is provided on a base film. In recent years, with the spread of touch panels, functional requirements for hard coat films used for such optical members are increasing.

  By the way, since the cycloolefin film is excellent in transparency, heat resistance, dimensional stability, low hygroscopicity, low birefringence, and optical isotropy, it is expected to be used for such optical member applications. It has been proposed to provide a hard coat layer on this cycloolefin film.

  When a cycloolefin film is used for an optical member, as with other resin films, a mixture of a cycloolefin resin raw material and an ultraviolet absorber is formed by melt extrusion for the purpose of preventing deterioration of liquid crystal due to ultraviolet rays. In general, a cycloolefin film containing a prepared UV absorber is used.

  On the other hand, thinning of liquid crystal display devices in recent years is expected to reduce the thickness of films for optical members (for example, a film thickness of 30 μm or less). If such a thin film contains an ultraviolet absorber, it is manufactured. It is known that the ultraviolet absorber easily bleeds out at the time of film formation and has problems such as a decrease in transparency, a yellowing of the film, and a decrease in processability due to a decrease in flexibility.

  Therefore, in the case of optical member use, the conventional cycloolefin film having a film thickness of 30 μm or less does not contain an ultraviolet absorber or suppresses its content even if an ultraviolet absorber is contained. Thus, a film having sufficient ultraviolet absorption performance has not been obtained.

  Therefore, when producing a hard coat film using such a cycloolefin film having a low ultraviolet absorption performance, a hard coat layer made of a mixture containing an ionizing radiation curable resin and an ultraviolet absorber is formed on the cycloolefin film. A method for imparting ultraviolet absorptivity by providing it has been proposed (see, for example, Patent Document 1).

JP 2008-134624 A

  However, although the hard coat film disclosed in Patent Document 1 can obtain ultraviolet absorption, it still has insufficient adhesion and durability, and has poor workability (curling) and poor visibility due to yellowing. There were many issues.

Therefore, the present invention uses a thin cycloolefin film having a thickness of 30 μm or less as a base material, and has hardness (surface hardness), adhesion, durability (especially light resistance, heat resistance, heat and humidity resistance), workability ( It is an object of the present invention to provide a hard coat film excellent in curling characteristics), optical characteristics (haze, transparency, etc.), and visibility (b ^* value).

As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by having the following configuration.
That is, the present invention has the following configuration.
The first invention is a hard coat layer containing an ionizing radiation curable resin on at least one side of a cycloolefin film having a thickness of 30 μm or less via an easy adhesion layer containing a mixture of a polyolefin resin and a styrene acrylic resin. Is a hard coat film characterized by satisfying the following conditions (A) and (B).
(A) b ^* value is 1.5 or less.
(B) After irradiating the hard coat film with ultraviolet rays having an irradiation illuminance of 500 W / m ² and an irradiation time of 100 hours in an environment of a temperature of 43 degrees and a humidity of 50% RH, the JIS-K5600-5-6 The residual ratio of the hard coat layer measured by a cross cut method is 90% or more.

A second invention is the hard coat film according to the first invention, wherein the hard coat film further satisfies the following conditions (C) and (D).
(C) Haze is 1% or less.
(D) The light transmittance at a wavelength of 380 nm is 25.0% or less.

  A third invention is the hard coat film according to the first or second invention, wherein the easy-adhesion layer contains an ultraviolet absorber.

  A fourth invention is a hard coat film according to any one of the first to third inventions, wherein the hard coat layer contains an ultraviolet absorber.

  5th invention is a hard coat film characterized by the total amount of the ultraviolet absorber contained in the said easily bonding layer and the said hard-coat layer in 3rd or 4th invention being 5-30 weight part. is there.

  According to a sixth invention, in any one of the first to fifth inventions, the blending ratio (parts by weight) of the polyolefin resin and the styrene acrylic resin contained in the easy-adhesion layer is a polyolefin resin: Styrene acrylic resin = 95: 5 to 70:30 It is a hard coat film characterized by the above-mentioned.

  According to a seventh invention, in any one of the first to sixth inventions, the hard coat layer is a polyfunctional compound having three or more (meth) acryloyloxy groups in one molecule as the ionizing radiation curable resin. A hard coat film containing an acrylate.

An eighth invention is a hard coat film according to any one of the first to seventh inventions, wherein the hard coat layer satisfies the following conditions.
Conditions: A film in which a hard coat layer made of the ionizing radiation curable resin cured at an ultraviolet light quantity of 50 to 100 mJ / cm ² is formed on a polyethylene terephthalate film so as to form a coating film having a thickness of 2 μm is prepared. Next, a test piece having a width of 15 mm and a length of 150 mm was prepared from the film, and the test piece was subjected to a tensile test at a tensile speed of 50 mm / min in an environment of a temperature of 23 ° C. and a humidity of 50% RH. The elongation until cracks occur in the coating film is 8% or more and 45% or less.

According to the present invention, a hard coat film for use in optical members can be thinned using a thin cycloolefin film having a thickness of 30 μm or less as a base material, and hardness (surface hardness), adhesion, durability (particularly light resistance) A hard coat film having excellent properties (eg, heat resistance, moist heat resistance), processability (curl characteristics), optical characteristics (haze, transparency, etc.), and visibility (b ^* value).

It is sectional drawing which shows the layer structure of one Embodiment of the hard coat film of this invention. It is a figure for demonstrating the evaluation method of the curl characteristic of a hard coat film.

Hereinafter, although the form for implementing this invention is demonstrated in detail, this invention is not limited to the following embodiment.
In the present specification, “XX to ΔΔ” means “from XX to ΔΔ” unless otherwise specified.

As shown in FIG. 1, a hard coat film 10 according to an embodiment of the present invention includes a polyolefin resin and a styrene acrylic resin on at least one surface of a cycloolefin film 1 having a thickness of 30 μm or less as a base material. A hard coat layer 3 containing an ionizing radiation curable resin is laminated via an easy-adhesion layer 2 containing a mixture, and the hard coat film 10 satisfies the following conditions (A) and (B): It is what.
(A) b ^* value is 1.5 or less.
(B) After irradiating the hard coat film with ultraviolet rays having an irradiation illuminance of 500 W / m ² and an irradiation time of 100 hours in an environment of a temperature of 43 ° C. and a humidity of 50% RH, the JIS-K5600-5-6 The residual ratio of the hard coat layer measured by a cross cut method is 90% or more.
Hereinafter, the configuration of the hard coat film 10 will be described in detail.

[Base film]
First, the base film of the hard coat film 10 will be described.
In the present invention, as the base film of the hard coat film, the cycloolefin film 1 having excellent transparency, heat resistance, dimensional stability, low hygroscopicity, low birefringence, optical isotropy, and the like is used. Features. Specifically, cycloolefin units are polymerized alternately or randomly in the polymer skeleton and have an alicyclic structure in the molecular structure, and include norbornene compounds, monocyclic cyclic olefins, cyclic conjugated dienes and vinyl fatty acids. A cycloolefin copolymer film or a cycloolefin polymer film, which is a copolymer comprising at least one compound selected from cyclic hydrocarbons, can be selected and used as appropriate.

  In the present invention, the cycloolefin film 1 has a thickness of 30 μm or less, preferably 25 μm or less, and more preferably 20 μm or less. As the thickness of the base film becomes thinner, the effect of thinning the liquid crystal display becomes larger. However, since the mechanical strength and the handling property are liable to be lowered due to the thin film, the lower limit value is 10 μm or more. And more preferably 13 μm or more.

  Further, regarding the heat resistance of the cycloolefin film 1, when used in the hard coat film application of the present invention, the thermogravimetry (TG) method for measuring the thermal change when a temperature change is applied to the sample or differential scanning. The use of a film having a glass transition temperature measured by a calorimetric (DSC) method or the like of about 120 ° C to 170 ° C is preferred.

  In the present invention, when the hard coat layer 3 is formed on one side of the cycloolefin film 1 via the easy adhesion layer 2, the cycloolefin film is wound on the back surface of the cycloolefin film 1 on which the hard coat layer is not formed. Polyethylene resin, polypropylene resin, or polyester resin that is excellent in releasability from cycloolefin film by co-extrusion method when forming cycloolefin film for the purpose of preventing film crimping and improving film runnability when forming hard coat layer It is good also as a film which laminated | stacked as a protective layer. Moreover, it is also possible to use what stuck protective films, such as a polyethylene resin in which the weak adhesion layer is formed in the back surface, a polypropylene resin, or a polyester resin.

  Examples of the cycloolefin film 1 include commercially available ZEONOR (trade name: manufactured by ZEON CORPORATION), Optica (trade name: manufactured by Mitsui Chemicals), Arton (trade name: manufactured by JSR Corporation), and Kozek. (Product name: Kurashiki Boseki Co., Ltd.).

[Easily adhesive layer]
Next, the easy-adhesion layer 2 of the hard coat film 10 will be described.
In the present invention, the easy adhesion layer 2 is a layer containing a mixture of a polyolefin resin and a styrene acrylic resin. Moreover, the said easily bonding layer 2 can contain a ultraviolet absorber further. That is, the easy adhesion layer may be a mixture layer containing a polyolefin resin, a styrene acrylic resin, and an ultraviolet absorber.

  In the present invention, the polyolefin resin used for the easy-adhesion layer 2 is a resin blended for the purpose of imparting adhesion between the cycloolefin film 1 and the hard coat layer 3. As a result of intensive studies on the resin for an easy adhesion layer having excellent adhesion to both the cycloolefin film and the hard coat layer, the present inventors have found that a polyolefin resin having excellent flexibility is suitable.

  The polyolefin-based resin used for the easy-adhesion layer 2 in the present invention is not particularly limited, but an ethylene-propylene copolymer and a propylene-butene copolymer are excellent in adhesion to the base material (cycloolefin film). Those constituting the copolymer with two or more types of monomers such as polymers are preferred, and those containing a propylene monomer in the copolymer are particularly preferred. Further, the molecular weight is not particularly limited, but those having a weight average molecular weight in the range of 10,000 to 200,000 are preferable from the viewpoint of balance between flexibility and adhesion. As such polyolefin resin, for example, commercially available Unistor (trade name: manufactured by Mitsui Chemicals), Surflen (trade name: manufactured by Mitsubishi Chemical), Arrow Base (trade name: manufactured by Unitika Ltd.) ), Auroren (trade name: manufactured by Nippon Paper Industries Co., Ltd.) and the like.

  In addition, since this polyolefin-type resin is resin excellent in a softness | flexibility, when forming an easily bonding layer and winding up a film, there exists a problem that a film surface tends to crimp | bond together. Therefore, from the viewpoint of preventing blocking between the film surfaces, it is preferable to prevent the pressure-bonding of the easy-adhesion layer by blending a high hardness resin, inorganic or organic fine particles, or attaching a protective film to the back surface of the cycloolefin film.

  In the blending of the inorganic or organic fine particles, the blending amount (parts by weight) is in the range of resin / inorganic or organic fine particles forming the easy-adhesion layer = 99.8 / 0.2 to 95.0 / 5.0 Preferably there is. If the amount of the inorganic or organic fine particles exceeds 5.0 parts by weight, it is not preferable because the transparency and the adhesion to the cycloolefin film are lowered. On the other hand, if the blending amount of the inorganic or organic fine particles is less than 0.2 parts by weight, there is a concern that a sufficient anti-bonding effect is not exhibited.

  Examples of inorganic fine particles include fine particles such as alumina, zinc oxide, silica, titanium oxide, and cerium oxide. Examples of organic fine particles include fine particles such as acrylic, melamine / formaldehyde condensate, polyethylene, styrene acrylic, and polyester. It can be illustrated. As the particle size, for example, it is preferable to use fine particles of 0.05 μm to 0.20 μm. A particle diameter of less than 0.05 μm is not preferable because the effect of preventing pressure bonding is low. On the other hand, if the particle diameter exceeds 0.20 μm, the effect of preventing further press-bonding cannot be obtained, resulting in an increase in cost, an increase in external haze, and a decrease in transparency, which is not preferable.

  Moreover, in this invention, the styrene acrylic resin contained in the said easily bonding layer 2 is a polymer which contains an acrylic monomer and a styrene monomer alternately or randomly in a structural unit. This styrene-acrylic resin prevents pressure-bonding between the protective film on the back of the cycloolefin film on which the hard coat layer is not formed and the easy-adhesion layer, and reduces the shrinkage difference between the easy-adhesion layer and the hard coat layer. Therefore, the resin is required to be relatively hard and less stretched. In the present invention, as a standard, it is desirable to use a resin having a glass transition temperature (Tg) of 50 ° C. or higher. Examples of such a styrene acrylic resin include a commercially available ARUFON resin (trade name: manufactured by Toa Gosei Co., Ltd.) and an acrylate resin (trade name: manufactured by Taisei Fine Chemical Co., Ltd.).

In the present invention, the blending ratio (parts by weight) of the polyolefin resin and the styrene acrylic resin contained in the easy adhesion layer 2 is preferably in the range of 95/5 to 70/30. More preferably, it is in the range of 90/10 to 80/20. If the blending ratio of the polyolefin resin exceeds 95 parts by weight, the easy-adhesion layer that is formed is soft and easily stretched. When the film is formed, there is a problem that cracks are likely to occur under heat resistant conditions (for example, storage at 100 ° C. for 5 minutes) and a pencil hardness is likely to be reduced due to a difference in shrinkage from the hard coat layer that is hard to stretch. . On the other hand, if the blending ratio of the polyolefin resin is less than 70 parts by weight, the difference in shrinkage between the easy adhesion layer and the hard coat layer is small, and there is no occurrence of cracks under heat resistant conditions. There exists a problem that adhesiveness with a cycloolefin film (base film) falls.

In the present invention, the easy-adhesion layer 2 preferably contains an ultraviolet absorber. Such an ultraviolet absorber is used for the purpose of reducing deterioration of liquid crystal due to ultraviolet rays when incorporated in a liquid crystal display as a deflecting plate. The UV absorbent that can be used in the present invention has excellent UV-absorbing properties, and is excellent in compatibility with polyolefin resins and styrene acrylic resins used as resins for easy-adhesion layers. And the b ^* value of the easy-adhesion layer containing the ultraviolet absorber is required to be low. In addition, this b ^* value is the value of the yellowness of the resin film measured by the method prescribed | regulated to JIS-Z8722.

  Use of a triazine-based ultraviolet absorber is effective as the ultraviolet absorber having the suitability for use in the present invention as described above. Triazine UV absorbers have a higher molecular weight than other UV absorbers (for example, benzophenone UV absorbers and benzotriazole UV absorbers), so if the compatibility with the resin for the easy adhesion layer is good, Since it is hard to be out and has little volatilization, it can retain ultraviolet absorbing ability over a long period of time, and since it hardly deteriorates against ultraviolet rays, it has the effect of reducing discoloration of the easy-adhesion layer and the hard coat layer.

  Specific examples of triazine-based ultraviolet absorbers that can be used in the present invention include Tinuvin 460 (trade name: manufactured by BASF Corporation), Adeka Stab LAF-70 (trade name: manufactured by ADEKA Corporation), KEMISORB 73 (Chemipro Kasei Co., Ltd.) Company-made), Chinosorb S (trade name: manufactured by BASF Corporation), and the like.

  In the present invention, when the easy-adhesion layer 2 contains an ultraviolet absorber, the blending ratio (parts by weight) of the ultraviolet absorber with respect to the resin component of the easy-adhesion layer is: resin component of the easy-adhesion layer / ultraviolet absorber = 97 / A range of 3 to 80/20 is preferable. When the blending ratio of the UV absorber exceeds 20 parts by weight, the haze is increased, the adhesion to the cycloolefin film is decreased, the easy-adhesion layer is yellowed, and cracks are likely to occur in the hard coat layer. It is not preferable. On the other hand, when the blending ratio of the ultraviolet absorber is less than 3 parts by weight, sufficient ultraviolet absorbing ability cannot be obtained.

  In the present invention, the necessary amount of the ultraviolet absorber may be contained not in the easy-adhesion layer 2 but in the hard coat layer 3. Moreover, you may make it contain the required quantity of a ultraviolet absorber separately in the easily bonding layer 2 and the hard-coat layer 3. FIG. This will be described in detail later.

The coating thickness of the easy-adhesion layer 2 in the present invention is not particularly limited, but within a range that does not adversely affect the adhesion between the cycloolefin film and the hard coat layer, or the pencil hardness of the hard coat layer. A range of 0.2 μm to 5.0 μm is preferable. In addition, the coating film thickness of an easily bonding layer can be measured by actually measuring with a micrometer.
When the coating thickness of the easy-adhesion layer 2 is less than 0.2 μm, it is difficult to obtain the target UV-absorbing property when the adhesiveness with the hard coat layer is lowered or the UV-absorbing agent is contained in the easy-adhesion layer. It is not preferable. On the other hand, when the coating thickness of the easy-adhesion layer 2 exceeds 5.0 μm, a large amount of a flexible easy-adhesion layer is formed in the lower layer of the hard coat layer, and the pencil hardness of the hard coat film is reduced. It is not preferable because cracks are likely to occur under a reduction (for example, a reduction from pencil hardness 5B to pencil hardness 6B) or under heat resistant conditions (for example, storage in an oven at a temperature of 100 ° C. for 5 minutes).

  In the easy-adhesion layer 2 in the present invention, a leveling agent can be blended for the purpose of improving the coatability. For example, known leveling such as fluorine-based, acrylic-based, siloxane-based, and adducts or mixtures thereof. Agents can be used. For example, the blending amount can be 0.03 to 3.0 parts by weight with respect to 100 parts by weight of the resin component of the easy-adhesion layer.

  Further, as other additives to be added to the easy-adhesion layer 2, an antifoaming agent, an antifouling agent, an antioxidant, an antistatic agent, a light stabilizer, and the like are required as long as the effects of the present invention are not impaired. May be blended.

  In the present invention, the easy-adhesion layer 2 may be made of other additives in addition to the polyolefin-based resin, the styrene-acrylic resin, and the ultraviolet absorbent (when the easy-adhesive layer contains an ultraviolet absorbent). A paint (easily adhesive layer paint) dissolved and dispersed in an organic solvent is applied onto the cycloolefin film and dried. The organic solvent in this case can be appropriately selected according to the solubility of the resin contained therein, and can be a solvent that can uniformly dissolve or disperse at least a solid content (resin and other additives), and at the time of coating. From the viewpoint of workability and drying properties, it is preferable to use an organic solvent having a boiling point of 50 ° C to 160 ° C, for example. Examples of such an organic solvent include aromatic solvents such as toluene, xylene, and n-heptane, aliphatic solvents such as cyclohexane, methylcyclohexane, and ethylcyclohexane, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, Known organic solvents such as ester solvents such as butyl acetate and methyl lactate, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, and alcohol solvents such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol and butanol. It is also possible to use the solvents alone or in combination of several kinds as appropriate.

  In the present invention, the method for coating the above-mentioned easy-adhesion layer coating on the cycloolefin film includes gravure coating, microgravure coating, fountain bar coating, slide die coating, slot die coating, and screen printing. Coating can be performed by a known coating method such as a spray coating method. The paint applied on the cycloolefin film is usually dried at a temperature of about 50 to 120 ° C. to remove the solvent and form a coating film.

[Hard coat layer]
Next, the hard coat layer 3 of the hard coat film 10 will be described.
In the present invention, the resin contained in the hard coat layer 3 can be used without particular limitation as long as it is a resin that forms a film, but particularly provides the surface hardness (pencil hardness, scratch resistance) of the hard coat layer. In addition, it is preferable to use an ionizing radiation curable resin in that the degree of crosslinking can be adjusted by the exposure amount of ultraviolet rays, and the surface hardness of the hard coat layer can be adjusted.

  The ionizing radiation curable resin used in the present invention is a transparent resin that is cured by irradiation with ultraviolet rays (hereinafter abbreviated as “UV”) or electron beams (hereinafter abbreviated as “EB”). Although not particularly limited, UV or EB having three or more (meth) acryloyloxy groups in one molecule in order that the coating film hardness and the hard coat layer form a three-dimensional cross-linked structure. Those composed of a curable polyfunctional acrylate are preferred. Specific examples of UV or EB curable polyfunctional acrylate having three or more (meth) acryloyloxy groups in the molecule include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (Meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane ethoxytriacrylate, glycerin propoxy Examples thereof include triacrylate and ditrimethylolpropane tetraacrylate. The polyfunctional acrylate may be used alone or in combination of two or more.

  Furthermore, the ionizing radiation curable resin used in the present invention is preferably a polymer having a weight average molecular weight in the range of 700 to 3600, more preferably a weight average molecular weight in the range of 700 to 3000, and a weight average molecular weight of 700. ˜2400 is more preferred. When the weight average molecular weight is less than 700, the curing shrinkage when cured by UV or EB irradiation is large, and the phenomenon that the hard coat film warps to the hard coat layer surface side (curl) increases, and the subsequent processing steps are performed. Defects occur and processing suitability is poor. On the other hand, if the weight average molecular weight exceeds 3600, the flexibility of the hard coat layer increases, but it is not suitable because the hardness is insufficient.

  Further, when the ionizing radiation curable resin used in the present invention has a weight average molecular weight of less than 1500, the number of functional groups in one molecule is desirably 3 or more and less than 10. When the ionizing radiation curable resin has a weight average molecular weight of 1500 or more, the number of functional groups in one molecule is preferably 3 or more and 20 or less. If it is in the said range, curling can be suppressed and generation | occurrence | production of a crack on heat-resistant conditions (for example, preserve | saved at 100 degreeC for 5 minutes) can be suppressed, and appropriate workability can be maintained.

  Moreover, as resin contained in the said hard-coat layer 3, other than the above-mentioned ionizing radiation curable resin, thermoplastic resins, such as polyethylene, a polypropylene, a polystyrene, a polycarbonate, polyester, an acryl, styrene-acryl, a fiber, You may mix | blend thermosetting resins, such as a phenol resin, urea resin, unsaturated polyester, an epoxy, and a silicon resin, in the range which does not impair the hardness of a hard-coat layer, and scratch resistance.

In the present invention, the hard coat layer 3 may contain an ultraviolet absorber. The UV absorber usable for the hard coat layer 3 is excellent in UV absorbability, in addition to excellent compatibility with the ionizing radiation curable resin used as the hard coat layer resin, and the b ^* value of the hard coat layer. Low is desirable. The b ^* value is as described above.

  Examples of the ultraviolet absorber used in the hard coat layer 3 include the same ultraviolet absorbers as those contained in the easy-adhesion layer 2 described above. That is, as the ultraviolet absorber contained in the hard coat layer 3, it is effective to use a triazine ultraviolet absorber. Specific examples of the triazine-based UV absorber can include the same examples as the specific examples of the triazine-based UV absorber contained in the above-mentioned easy adhesion layer.

When the hard coat layer 3 of the present invention contains an ultraviolet absorber, the blending ratio (parts by weight) of the ultraviolet absorber to the resin component (ionizing radiation curable resin) of the hard coat layer is the ionizing radiation curing used for the hard coat layer. The mold resin / ultraviolet absorber is preferably in the range of 97/3 to 90/10. When the blending ratio of the ultraviolet absorber exceeds 10 parts by weight, the haze increases, the scratch resistance decreases, the adhesiveness between the cycloolefin film (base material) and the easy adhesion layer, and the b ^* value of the hard coat layer. Is unfavorable because of the high. On the other hand, when the blending ratio of the ultraviolet absorber is less than 3 parts by weight, sufficient ultraviolet absorbing ability cannot be obtained.

In the present invention, as described above, the necessary amount of the ultraviolet absorber may be contained only in one of the easy-adhesion layer 2 and the hard coat layer 3. The required amount of the agent may be separately contained in the easy-adhesion layer 2 and the hard coat layer 3.
In this case, the total amount of the ultraviolet absorber contained in the easy-adhesion layer 2 and the hard coat layer 3 is 5 to 30 parts by weight with respect to the total amount of resin components in the easy-adhesion layer and the hard coat layer. Is preferred. More preferably, it is 5-25 weight part, More preferably, it is 10-25 weight part. If the total amount of the ultraviolet absorber exceeds 30 parts by weight, it is not preferable because haze increases, scratch resistance decreases, adhesion between the cycloolefin film and the easy-adhesion layer decreases, and the b ^* value of the hard coat film increases. On the other hand, if the total amount of the ultraviolet absorber is less than 5 parts by weight, sufficient ultraviolet absorbing ability cannot be obtained.
The content of the ultraviolet absorber in each layer is not particularly limited, but the content of the content is determined comprehensively from the viewpoint of the coating thickness of each layer, the adhesion with each layer, the coating strength of each layer, and the like. Settings can be made. Under such circumstances, it is preferable to add more UV absorber to the easy-adhesion layer 2 than to the hard coat layer 3 because the b ^* value of the hard coat film can be further suppressed.

  In the present invention, the hard coat layer 3 may contain inorganic oxide fine particles to further improve the surface hardness (scratch resistance). In this case, the average particle size of the inorganic oxide fine particles is preferably in the range of 5 to 50 nm, more preferably in the range of 10 to 20 nm. If the average particle size is less than 5 nm, it is difficult to obtain sufficient surface hardness. On the other hand, if the average particle diameter exceeds 50 nm, the gloss and transparency of the hard coat layer are likely to be lowered, and the flexibility may be lowered.

  In the present invention, examples of the inorganic oxide fine particles include alumina and silica. Among these, alumina containing aluminum as a main component is particularly suitable because it has a high hardness and can obtain an effect with a smaller amount of addition than silica.

  In the present invention, the content of the inorganic oxide fine particles is preferably 0.1 to 10.0 parts by weight with respect to 100 parts by weight of the ionizing radiation curable resin of the hard coat layer 3. When the content of the inorganic oxide fine particles is less than 0.1 parts by weight, it is difficult to obtain an effect of improving the surface hardness (abrasion resistance). On the other hand, if the content exceeds 10.0 parts by weight, the haze increases, which is not preferable.

  The hard coat coating material for forming the hard coat layer 3 of the present invention can contain a photopolymerization initiator. As such a photopolymerization initiator, acetophenones such as commercially available IRGACURE 651 and IRGACURE 184 (both trade names: manufactured by BASF) and benzophenones such as IRGACURE 500 (trade name: manufactured by BASF) are used. it can.

For the hard coat layer 3, a leveling agent can be used for the purpose of improving coatability. For example, a known leveling agent such as fluorine-based, acrylic-based, siloxane-based, or an adduct or mixture thereof is used. Is possible. The blending amount can be in the range of 0.03 to 3.0 parts by weight with respect to 100 parts by weight of the solid content of the resin of the hard coat layer. In addition, in touch panel applications and the like, adhesion to the cover glass (CG), transparent conductive member (TSP), liquid crystal module (LCM), etc. of the touch panel terminal using an optical transparent adhesive OCR is required. In this case, it is preferable to use an acrylic leveling agent or a fluorine leveling agent having a high surface free energy (approximately 40 mJ / cm ² or more).

  As other additives to be added to the hard coat layer 3, an antifoaming agent, a surface tension adjusting agent, an antifouling agent, an antioxidant, an antistatic agent, a light stabilizer and the like are added within a range not impairing the effects of the present invention. You may mix | blend as needed.

  In addition to the ionizing radiation curable resin and the ultraviolet absorber (when the hard coat layer contains an ultraviolet absorber), the hard coat layer 3 contains a photopolymerization initiator, other additives, and the like in an appropriate solvent. After coating and drying the hard coat paint dissolved and dispersed in the easy-adhesion layer, irradiation with ionizing rays such as UV or EB results in photopolymerization and a hard coat layer having excellent hard properties can be obtained. it can. The solvent can be appropriately selected depending on the solubility of the resin to be blended, and any solvent that can uniformly dissolve or disperse at least solids (resin, photopolymerization initiator, other additives, etc.) may be used. Examples of such solvents include aromatic solvents such as toluene, xylene and n-heptane, aliphatic solvents such as cyclohexane, methylcyclohexane and ethylcyclohexane, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate and acetic acid. A known organic solvent such as an ester solvent such as butyl or methyl lactate, a ketone solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, or cyclohexanone, or an alcohol solvent such as methanol, ethanol, isopropyl alcohol, or n-propyl alcohol. Or it can also be used in combination of several kinds as appropriate.

  The method of applying the hard coat paint for forming the hard coat layer 3 is not particularly limited, but gravure coating, micro gravure coating, fountain bar coating, slide die coating, slot die coating, screen printing. After coating by a known coating method such as a spray coating method, it is usually dried at a temperature of about 50 to 120 ° C.

In the present invention, the hard coat layer 3 preferably further satisfies the following conditions.
Conditions: A film in which a hard coat layer made of the ionizing radiation curable resin cured with an ultraviolet light quantity of 50 to 100 mJ / cm ² is formed on a polyethylene terephthalate film so as to form a 2 μm thick coating film is prepared. Next, a test piece having a width of 15 mm and a length of 150 mm was prepared from the film, and the test piece was subjected to a tensile test at a tensile speed of 50 mm / min in an environment of a temperature of 23 ° C. and a humidity of 50% RH. The elongation until cracks occur in the coating film is 8% or more and 45% or less.

By satisfying the above conditions, that is, by controlling the elongation (elongation rate) of the hard coat layer 3 within a predetermined range, the hard coat layer can obtain the hard coat film excellent in processability by suppressing the curling described above. Can do.
In order for the hard coat layer 3 to satisfy the above conditions, examples of the ionizing radiation curable resin contained in the hard coat layer include EBECRYL-5129 (trade name: manufactured by Daicel Ornex Co., Ltd.), NK Oligo U-6LPA ( Trade name: Shin-Nakamura Chemical Co., Ltd.), ArtResin UN-908 (trade name: Negami Kogyo Co., Ltd.), Unidic 17-806 (trade name: DIC Corporation), ACRIT 8UX-015A (trade name: Preferred examples include Taisei Fine Chemical Co., Ltd.).

  The coating thickness of the hard coat layer 3 is not particularly limited, but is preferably in the range of 1.0 μm to 5.0 μm, and more preferably in the range of 1.5 μm to 3.5 μm. is there. A coating thickness of less than 1.0 μm is not preferable because the required scratch resistance and pencil hardness are reduced. On the other hand, when the coating thickness exceeds 5.0 μm, curling is likely to occur strongly, and the handling property is reduced in the manufacturing process and the like, which is not preferable. The coating thickness of the hard coat layer can be measured by actually measuring with a micrometer.

  The hard coat layer 3 of the present invention is preferably a hard coat layer having a pencil hardness defined by JIS K5600-5-4 of 5B or more, more preferably a pencil hardness of 4B or more, and still more preferably a pencil hardness. 3B or more.

[Hard coat film]
It is important that the hard coat film 10 according to one embodiment of the present invention obtained as described above satisfies the following conditions (A) and (B).
(A) b ^* value is 1.5 or less.
(B) After irradiating the hard coat film with ultraviolet rays having an irradiation illuminance of 500 W / m ² and an irradiation time of 100 hours in an environment of a temperature of 43 ° C. and a humidity of 50% RH, the JIS-K5600-5-6 The residual ratio of the hard coat layer measured by a cross cut method is 90% or more.

It is important that the b ^* value of the hard coat film of the present invention is 1.5 or less, preferably 1.0 or less, more preferably 0.6 or less. The b ^* value is as described above. When the b ^* value is 1.5 or less, visibility deterioration due to film yellowing can be prevented.

  Moreover, the hard coat film of this invention is a hard coat film which is excellent in light resistance (light-resistant adhesiveness) by satisfy | filling the said conditions (B).

The hard coat film of the present invention preferably further satisfies the following conditions (C) and (D).
(C) Haze is 1% or less.
(D) The light transmittance at a wavelength of 380 nm is 25.0% or less.

  The hard coat film of the present invention preferably has a haze of 1% or less, more preferably 0.5% or less, and still more preferably 0.3% or less.

  The hard coat film of the present invention preferably has a light transmittance at a wavelength of 380 nm of 25.0% or less, more preferably 20.0% or less.

  The hard coat film 10 that satisfies the above conditions (A) and (B), or the conditions (A) to (D) is, for example, the total amount of the ultraviolet absorber contained in the easy-adhesion layer and the hard coat layer. This can be achieved by adjusting appropriately.

The cycloolefin film having a thickness of 30 μm or less usually does not contain an ultraviolet absorber for the reasons described above, and therefore, the applied hard coat layer has durability by UV irradiation (light adhesion to a cycloolefin film). Lower. Therefore, as described above, adhesion durability due to ultraviolet irradiation can be improved by containing an ultraviolet absorber in either one of the easy-adhesion layer and the hard coat layer, or in both layers. However, when an ultraviolet absorber is contained in the easy-adhesion layer or the hard coat layer, haze, light transmittance, and b ^* value are likely to increase, which may cause yellowing.

  In the present invention, from this point of view, as described above, the total amount of the ultraviolet absorber contained in the easy-adhesion layer 2 and the hard coat layer 3 is adjusted to a range of 5 to 30 parts by weight. It is preferably 5 to 25 parts by weight, more preferably 10 to 25 parts by weight. By adjusting the content of the ultraviolet absorber to the above range, the hard coat film of the present invention easily satisfies the above conditions (A) and (B) or the conditions (A) to (D).

As described above in detail, according to the present invention, a hard coat film for use in an optical member can be thinned using a thin cycloolefin film having a thickness of 30 μm or less as a base material, and hardness (surface hardness), A hard coat film having excellent adhesion, durability (especially light resistance, heat resistance, moist heat resistance, etc.), workability (curl characteristics), optical characteristics (haze, transparency, etc.) and visibility (b ^* value) is obtained. be able to.

Next, although an example and a comparative example are given and an embodiment of the present invention is explained still more concretely, the present invention is not limited to the following examples.
Unless otherwise specified, “parts” and “%” described below represent “parts by weight” and “% by weight”, respectively.

[Example 1]
<Preparation of easy adhesion layer paint>
First, 40 parts of styrene acrylic resin “ARUFON UG-4070 (trade name)” (100% solid content, manufactured by Toa Gosei Co., Ltd., glass transition temperature 58 ° C.) was stirred into 160 parts of ethyl acetate using a stirrer. While adding a small amount, the resin was dissolved to prepare a solution having a concentration of 20%.
Next, 85 parts of polyolefin resin “Surflen P-1000 (trade name)” (solid content 20%, manufactured by Mitsubishi Chemical Corporation) and the above styrene acrylic resin “ARUFON UG-4070 (trade name)” (solid content 20 %) Was mixed with 15 parts, and diluted with butyl acetate / toluene = 85/15 (wt%) to a solid content concentration of 10% to prepare an easy adhesion layer coating material.

<Preparation of hard coat layer paint>
Based on 100 parts of urethane acrylate-based ultraviolet curable resin “ARTRESIN UN-908 (trade name)” (solid content 100%, (meth) acryloyloxy group number: 9, weight average molecular weight: 3600, manufactured by Negami Kogyo Co., Ltd.) TINUVIN 460 (triazine UV absorber, manufactured by BASF) 10 parts, Irgacure 184 (photopolymerization initiator, manufactured by BASF) 3.5 parts, TINUVIN 292 (hindered amine light stabilizer, manufactured by BASF) 2. 5 parts and 0.3 part of leveling agent RS75 (fluorine-based leveling agent, manufactured by DIC Corporation) with butyl acetate / n-propyl alcohol = 50/50 (parts by weight) in the solid content concentration in the UV curable resin coating Was diluted to 35% and stirred well to prepare a hard coat layer coating.
A film in which a hard coat layer made of an ionizing radiation curable resin cured with an ultraviolet light quantity of 100 mJ / cm ² is formed on a polyethylene terephthalate film to form a 2 μm thick coating film using the hard coat layer paint. Is made. Next, a test piece having a width of 15 mm and a length of 150 mm was prepared from the film, and the test piece was subjected to a tensile test at a tensile speed of 50 mm / min in an environment of a temperature of 23 ° C. and a humidity of 50% RH. The elongation rate until the cracks occurred in the coating film was 18.3%.

<Preparation of hard coat film>
The easy-adhesion layer paint is applied to one side of a 13 μm thick ZEONOR film ZF14 (manufactured by Nippon Zeon Co., Ltd.) as a cycloolefin film using a bar coater. Then, an easy-adhesion layer with a coating thickness of 2.0 μm was formed to obtain an easy-adhesion layer-coated film.
Next, on the easy-adhesion layer of the easy-adhesion layer-coated film, the above-mentioned hard coat layer paint is applied using a bar coater and dried with hot air in a drying oven at 80 ° C. for 1 minute to obtain a coating thickness of 2. A 5 μm coating layer was formed. This was cured using a UV irradiation apparatus set at a height of 60 mm from the coated surface at a UV irradiation amount of 150 mJ / cm ² to form a hard coat layer, and a hard coat film of this example was produced.

[Example 2]
Except that 10 parts of ADK STAB LAF-70 (triazine UV absorber, manufactured by ADEKA Co., Ltd.) was blended with the easy-adhesion layer paint of Example 1, and the blending amount of TINUVIN 460 of the hard coat layer paint was 5 parts. Obtained a hard coat film in the same manner as in Example 1.

[Example 3]
Example 2 except that 15 parts of ADK STAB LAF-70 contained in the easy-adhesion layer coating material of Example 2 and 15 parts of TINUVIN 460 contained in the hard coat layer coating material (that is, no blending) were used. In the same manner as above, a hard coat film was obtained.

[Example 4]
A hard coat film was obtained in the same manner as in Example 2 except that 10 parts of TINUVIN 460 of the hard coat layer paint of Example 2 was used.

[Example 5]
A hard coat film was obtained in the same manner as in Example 1 except that 5 parts of TINUVIN 460 of the hard coat layer coating material of Example 1 was used.

[Example 6]
A hard coat film was obtained in the same manner as in Example 3 except that 15 parts of TINUVIN 460 of the hard coat layer paint of Example 3 was changed to 15 parts.

[Example 7]
The ultraviolet curable resin of the hard coat layer coating material of Example 2 is a urethane acrylate ultraviolet curable resin “ACRIT 8UX-015A (trade name)” (solid content 100%, (meth) acryloyloxy group number: 15, weight average molecular weight). : 2000, manufactured by Taisei Fine Chemical Co., Ltd.) A hard coat film was obtained in the same manner as in Example 2 except that the UV absorber of the hard coat layer paint of Example 2 was changed to KEMISORB 73.

[Example 8]
A hard coat film was obtained in the same manner as in Example 2 except that the cycloolefin film substrate of Example 2 was a cycloolefin copolymer film “OPTICA 50 μm (trade name)” (manufactured by Mitsui Chemicals, Inc.).

[Comparative Example 1]
A hard coat film was obtained in the same manner as in Example 1 except that TINUVIN 460 of the hard coat layer paint of Example 1 was changed to 0 part (not blended).

[Comparative Example 2]
A hard coat film was obtained in the same manner as in Example 2 except that the mixing ratio of Surflen P1000 and ARUFON UG-4070 in the easy-adhesion layer coating material of Example 2 was set to 100/0.

[Comparative Example 3]
A hard coat film was obtained in the same manner as in Example 2 except that the mixing ratio of Surflen P1000 and ARUFON UG-4070 of the easy-adhesion layer coating material of Example 2 was set to 0/100.

  The hard coat films of Examples and Comparative Examples produced as described above were evaluated for the following items, and the results are summarized in Table 1. In Table 1, the ultraviolet absorbent is abbreviated as “UVA”.

(1) Film thickness The formation thickness of the easy-adhesion layer and the hard coat layer was measured using Thin-Film Analyzer F20 (trade name) (manufactured by FILMETRICS).

(2) Adhesion (initial adhesion, wet heat adhesion and light-resistant adhesion)
The initial adhesion is in accordance with JIS-K5600-5-6, with a cross cut of 1 mm ² under normal conditions, that is, constant temperature and humidity conditions (23 ° C., 50% RH) using a cross-cut peel test jig. 100 pieces were prepared, and adhesive tape No. 252 made by Sekisui Chemical Co., Ltd. was affixed on it, pressed evenly with a spatula, then peeled in the direction of 180 degrees, and the remaining number of hard coat layers was evaluated in four stages. did. The evaluation criteria are as follows, and ◎ and ○ evaluation products (that is, the hard coat layer remaining rate of 90% or more) were judged to be acceptable.
◎: 100 pieces ○: 99 to 90 pieces △: 89 to 50 pieces ×: 49 to 0 pieces

  In addition, wet heat adhesion (adhesion over time under wet heat conditions) was determined by storing each hard coat film under wet heat conditions (80 ° C., 90% RH) for 30 days, and then performing a cross-cut peel test in the same manner as described above. The adhesion of the hard coat layer was evaluated in four stages. The evaluation criteria are the same as in the case of the above initial adhesion.

Moreover, about light-resistant adhesion, about each hard coat film, Suga Test Co., Ltd. ultraviolet auto fade meter "U48AU" (ultraviolet carbon arc lamp) is used, and test conditions are irradiation illumination intensity 500W / m < ² >, temperature 43 degree | times, When the humidity was 50% RH and the irradiation time was 100 hours, the adhesion of the hard coat layer was carried out by the same cross-cut test method as described above according to JIS-K5600-5-6. The evaluation criteria are the same as in the case of the above initial adhesion.

(3) Haze The haze of each hard coat film prepared in Examples and Comparative Examples was measured using a haze meter “HM150” manufactured by Murakami Color Research Laboratory based on JIS-K7136.

(4) Heat-resistant cracks Each hard coat film produced in Examples and Comparative Examples was suspended and stored in a dryer at 100 ° C. for 5 minutes, and then the hard coat film was taken out and visually evaluated for occurrence of cracks. did. The degree of occurrence of cracks was evaluated according to the following criteria.
○: No crack was generated.
Δ: Some cracks are observed at the end of the test piece.
X: Cracks are observed on the entire surface of the test piece.

(5) Pencil hardness About each hard coat film produced by the Example and the comparative example, pencil hardness was measured by the test method according to JIS-K-5600-5-4. The hardness without scratches on the surface was marked. About the criteria, hardness 5B or more was set as the pass.

(6) Scratch resistance For each hard coat film produced in Examples and Comparative Examples, the hard coat layer surface was loaded with steel wool # 0000 by a test method according to JIS-K-5600-5-10. 10 kg of reciprocating friction was applied for 1 kg, and the degree of scratching was evaluated according to the following criteria. ○ The evaluation product was considered to have good scratch resistance. ΔEvaluated products can also be used as products.
○: No scratches △: Slight scratches ×: Innumerable scratches

(7) 380 nm light transmittance About each hard coat film produced by the Example and the comparative example, it measured using the Hitachi High-Technologies spectrophotometer U-3310. The measurement was performed at a wavelength range of 250 to 800 nm and a scan speed of 300 nm / min, and the light transmittance at a wavelength of 380 nm was detected. Regarding the evaluation criteria, a light transmittance of less than 25% was regarded as acceptable.

(8) Curl characteristics About each hard coat film produced by the Example and the comparative example, a square rhombus-shaped test piece of 10 cm on a side with the application direction (MD direction shown in the figure) as a basic axis as shown in FIG. Set the hard coat layer side up and store for 30 minutes in a 23 ° C., 50% RH environment, then measure the height of the four vertices (A, B, C, D) that are warped from the horizontal plane. The average value was defined as the curl height. As for evaluation criteria, if the curl height is 40 mm or less, it can be used practically, and the lower the value, the better.

(9) b ^* value About each hard coat film produced by the Example and the comparative example, it measured by SPECTROTOPOMETETR DOT-3C by Murakami Color Research Laboratory. About evaluation criteria, b ^* value was determined to be 1.5 or less.

As is apparent from the results in Table 1 above, according to the examples of the present invention, hardness (surface hardness), adhesion, durability (especially light resistance, heat resistance, moist heat resistance, etc.), workability (curl characteristics) ), Optical properties (haze, transparency, etc.) and visibility (b ^* value) can be obtained. In addition, since a thin cycloolefin film having a thickness of 30 μm or less is used as a base material, a hard coat film for use as an optical member can be thinned.
Further, for example, from the comparison between Example 2 and Example 3, it is more preferable to add more UV absorber to the easy-adhesion layer than to the hard coat layer because the b ^* value of the hard coat film can be suppressed lower. Recognize. The easy-adhesion layer is an intermediate layer between the base film and the hard coat layer, and the b ^* value of the hard coat film is lowered and the visibility is improved when the surface hard coat layer is a clear layer.

  On the other hand, in Comparative Example 1 which does not contain the ultraviolet absorber in either the easy-adhesion layer or the hard coat layer, the durability due to ultraviolet irradiation is inferior, and in particular, light resistance and transparency (380 nm light transmittance) are low. Inferior. In Comparative Examples 2 and 3, in which both the easy-adhesive layer and the hard coat layer contain an ultraviolet absorber, but the polyurethane-based resin and the styrene-acrylic resin are not used in combination in the easy-adhesive layer, There is a problem (Comparative Example 2) in which cracks are likely to occur and a problem (Comparative Example 3) inferior in adhesion to the substrate (particularly adhesion over time and light-resistant adhesion under wet heat conditions).

1 Cycloolefin film 2 Easy adhesion layer 3 Hard coat layer 10 Hard coat film

Claims (8)

A hard coat layer containing an ionizing radiation curable resin is laminated on at least one surface of a cycloolefin film having a thickness of 30 μm or less via an easy adhesion layer containing a mixture of a polyolefin resin and a styrene acrylic resin, and A hard coat film characterized by satisfying the conditions (A) and (B).
(A) b ^* value is 1.5 or less.
(B) After irradiating the hard coat film with ultraviolet rays having an irradiation illuminance of 500 W / m ² and an irradiation time of 100 hours in an environment of a temperature of 43 degrees and a humidity of 50% RH, the JIS-K5600-5-6 The residual ratio of the hard coat layer measured by a cross cut method is 90% or more. The hard coat film according to claim 1, wherein the hard coat film further satisfies the following conditions (C) and (D).
(C) Haze is 1% or less.
(D) The light transmittance at a wavelength of 380 nm is 25.0% or less.   The hard coat film according to claim 1, wherein the easy-adhesion layer contains an ultraviolet absorber.   The hard coat film according to claim 1, wherein the hard coat layer contains an ultraviolet absorber.   The hard coat film according to claim 3 or 4, wherein the total amount of the ultraviolet absorber contained in the easy-adhesion layer and the hard coat layer is 5 to 30 parts by weight.   The blending ratio (parts by weight) of the polyolefin resin and the styrene acrylic resin contained in the easy-adhesion layer is polyolefin resin: styrene acrylic resin = 95: 5 to 70:30. The hard coat film according to any one of claims 1 to 5.   The hard coat layer contains, as the ionizing radiation curable resin, a polyfunctional acrylate having three or more (meth) acryloyloxy groups in one molecule. The hard coat film as described. The hard coat film according to any one of claims 1 to 7, wherein the hard coat layer satisfies the following conditions.
Conditions: A film in which a hard coat layer made of the ionizing radiation curable resin cured at an ultraviolet light quantity of 50 to 100 mJ / cm ² is formed on a polyethylene terephthalate film so as to form a coating film having a thickness of 2 μm is prepared. Next, a test piece having a width of 15 mm and a length of 150 mm was prepared from the film, and the test piece was subjected to a tensile test at a tensile speed of 50 mm / min in an environment of a temperature of 23 ° C. and a humidity of 50% RH. The elongation until cracks occur in the coating film is 8% or more and 45% or less.

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