JP2003313329A - Hard coat film, method for correcting/preventing curling of hard coat film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hard coat film having one or more resin layers on a flexible plastic film which can prevent occurrence of curling without selecting a resin which is hard to thermally shrink or a resin which is hard to shrink due to crosslink curing as the resin constituting the resin layers or without providing a resin layer exhibiting the same shrinkage on the opposite surface of the flexible plastic film or a hard coat film capable of correcting curling even if it occurs. <P>SOLUTION: The hard coat film has one or more resin layers on one surface of the flexible plastic film, and is constituted in a manner such that at least one layer of the above resin layers is a hard coat layer and, simultaneously, at least one layer of the above resin layers contains thermally expandable microcapsules. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hard coat film in which curl is corrected / prevented, and a curl correction / prevention method for a hard coat film.

[0002]

2. Description of the Related Art In recent years, hard coat films have been used for display parts of various home electric appliances and decorative plates for membrane switches.

Such a hard coat film is mainly manufactured by a coating method. Specifically, it can be produced by applying a coating liquid in which the constituents of the resin layer constituting the hard coat film, such as the undercoat layer and the hard coat layer, are applied onto a plastic film and heating and drying.

However, the hard coat film produced in this manner may be curled so as to have a concave shape on the resin layer side, which causes a problem such as inconvenience when incorporated into an electric / electronic component. It was happening.

Such curling is caused by the fact that the resin forming the resin layer shrinks during the formation of the resin layer, the crosslinking cure progresses after the resin layer is formed, and the resin layer shrinks after the resin layer is formed. It is considered to occur due to the result of absorbing and releasing moisture in the air. Therefore, as a means for preventing curling, a resin that does not easily shrink by heat or a resin that does not easily shrink by cross-linking curing is selected as a resin forming the resin layer, or a resin layer that exhibits the same behavior on the opposite surface of the plastic film is used. It is considered that the means provided is effective.

[0006]

However, the former means narrows the selection range of the resin forming the resin layer, and as a result, the function of the resin layer (hard coat property, etc.) is made sufficient. Can not do it. In addition, the latter means complicates the design of resin layers exhibiting the same behavior. In particular, depending on the application of the hard coat film, when the resin layer cannot be provided on the opposite surface, or the resins and additives that compose the resin layer on the opposite surface are limited, designing resin layers that exhibit the same behavior is not possible. It's extremely difficult.

[0007]

In order to achieve the above object, the hard coat film of the present invention comprises at least one resin layer on a flexible plastic film, wherein At least one layer is a hard coat layer, and at least one of the resin layers contains thermally expandable microcapsules.

The curl correction / prevention method for a hard coat film of the present invention has at least one resin layer on a flexible plastic film, and at least one of the resin layers is a hard coat layer. A hard coat film containing a heat-expandable microcapsule in at least one of the resin layers is thermally expanded.

Alternatively, at least one resin layer is provided on the flexible plastic film, at least one of the resin layers is a hard coat layer, and at least one of the resin layers is heated. A hard coat film containing expandable microcapsules, after being curled into a concave shape on the resin layer side containing the expandable microcapsules, the thermally expandable microcapsules are thermally expanded. It is a thing.

Alternatively, at least one resin layer is provided on the flexible plastic film, at least one of the resin layers is a hard coat layer, and at least one of the resin layers is heated. The heat-expandable microcapsules are thermally expanded in the process of forming a curl-causing resin layer of the hard coat film containing the expandable microcapsules.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The hard coat film of the present invention has at least one resin layer on a flexible plastic film, and at least one of the resin layers is a hard coat layer. In addition, at least one of the resin layers contains heat-expandable microcapsules. Hereinafter, an embodiment of each component will be described.

The flexible plastic film is not particularly limited and may be polyester, polycarbonate, polyvinyl chloride, polyethylene, polypropylene,
Examples include polystyrene. Such a flexible plastic film is excellent in handleability because it has flexibility, but has a problem that curling is likely to occur.

The resin layer is mainly composed of resin and additives, and is provided on at least one layer on the flexible plastic film.

At least one of the resin layers must be a hard coat layer that imparts hard coat properties to the hard coat film. As the other resin layer, there is an undercoat layer or an overcoat layer which imparts auxiliary functions other than hard coat properties to the hard coat film, for example, functions such as antistatic property, adhesive property, antireflection property, and weather resistance. can give.

As the resins and additives constituting such a resin layer, those known as those imparting a specific function can be used.

For example, as the hard coat layer, a thermosetting resin such as an organopolysiloxane-based resin, a melamine-based resin, a phenol-based resin or a urethane-based resin which is generally used as a resin forming the hard coat layer, and further, A photocurable resin using a monomer or oligomer such as an acrylic compound or an epoxy compound can be used. Further, the hard coat layer may contain additives such as known benzotriazole-based and benzoguanamine-based ultraviolet absorbers.

The composition of the other resin layer differs depending on its role, but when it has a role of improving the adhesiveness between the flexible plastic film and the hard coat layer, the flexible resin film and the hard coat layer are mainly used. Each of the layers is made of a resin having good adhesiveness. For example, when the flexible plastic film is made of polyester resin and the hard coat layer is made of acrylic resin, the resin forming the undercoat layer is preferably acrylic-styrene resin.

The resin layer is formed by applying a coating material containing a resin, an additive, a solvent and the like on a flexible plastic film and heating and drying. If necessary, the resin layer may be crosslinked and cured by heating, irradiation with ultraviolet rays, or the like after the formation. Here, when the resin forming the resin layer is one that heat shrinks in the process of forming the resin layer or one that shrinks due to progress of crosslinking and curing after the resin layer is formed, curling occurs in the hard coat film. Is believed to be.

The hard coat film of the present invention is characterized by containing heat-expandable microcapsules in at least one resin layer. In this way, the curl described above can be corrected / prevented by including the thermally expandable microcapsules in the resin layer. It is considered that the reason why the curl can be corrected / prevented is that the thermal expansion of the heat-expandable microcapsules cancels the shrinkage of the resin forming the resin layer that causes the curl.

The thermally expandable microcapsules may or may not be thermally expanded in the resin layer. The hard coat film in which the thermally expandable microcapsules are thermally expanded in the resin layer is one in which the occurrence of curl is prevented. The hard coat film in which the heat-expandable microcapsules are not thermally expanded in the resin layer can correct the curl that is presently occurring or curl that is occurring in the future by thermally expanding the heat-expandable microcapsule. Is.

The time for thermally expanding the thermally expandable microcapsules can be divided into the process of forming the resin layer (during heating and drying of the resin layer) and after forming the resin layer (after heating and drying of the resin layer).

Here, when the cause of the curl is contraction of the resin in the process of forming the resin layer, it is preferable to thermally expand the thermally expandable microcapsules in the process of forming the resin layer that causes the curl. The hard coat film thus obtained is one in which the occurrence of curl during production is prevented.

When the cause of curling is after the resin layer is formed, such as when the resin constituting the resin layer is crosslinked and cured after the resin layer is formed, the thermally expansive micro-expandable resin is formed in the process of forming the resin layer. It is preferable not to thermally expand the capsule. As a means of not thermally expanding the thermally expandable microcapsules in the process of forming the resin layer, the resin layer may be dried by heating at a temperature not higher than the expansion start temperature of the thermally expandable microcapsules. The hard coat film thus obtained is curled to have a concave shape on the resin layer side containing the heat-expandable microcapsules after the production, and then by thermally expanding the heat-expandable microcapsules, The curl that occurred can be corrected.

Examples of the heat-expandable microcapsules include those in which a volatile liquid (expanding agent) is wrapped in a capsule-shaped outer shell made of a polymer that softens when the temperature is raised.

Examples of the volatile liquid include isobutane, isopentane, normal butane, normal pentane, neopentane, hexane, etc., but hydrocarbons mainly containing isobutane and isopentane can be preferably used. The proportion of the volatile liquid in the heat-expandable microcapsules is 5 to
30% by weight is suitable.

The outer shell is made of a thermoplastic material that softens when heated and expands due to the volatile expansion of the volatile liquid enclosed therein. The polymer forming the outer shell needs to have a sufficiently high viscosity even at a heating temperature so that the outer shell does not burst even when thermally expanded and maintains a capsule state. Polymers satisfying such conditions include vinylidene chloride, acrylonitrile, methacrylonitrile, and one or more copolymers of methyl methacrylate, for example, vinylidene chloride-acrylonitrile copolymer, vinylidene chloride-acrylonitrile-methyl methacrylate copolymer. , Acrylonitrile-methacrylonitrile copolymer, and copolymers of one or more of these with various monomers such as vinyl halide, styrene-based monomer, vinyl acetate, butadiene, vinyl pyridine, and chloroprene. The thermoplastic resin may be crosslinked or crosslinkable with a crosslinking agent such as divinylbenzene, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, triacrylic formal, triallyl isocyanate. Among these thermoplastic resins, in particular, a (meth) acrylonitrile homopolymer or (meth) having a high expansion start temperature and a high maximum expansion temperature.
A copolymer having a high acrylonitrile content is preferably used.

The average particle size, expansion temperature, expansion coefficient, etc. of the heat-expandable microcapsules cannot be generally determined depending on the material of the outer shell, but the average particle size is 10 to 20 μm, the expansion start temperature and the maximum expansion temperature are 80. ~ 190 ℃, expansion coefficient is 30 by volume
About 50 times is used. In order to thermally expand the heat-expandable microcapsule, it cannot be said unconditionally depending on the material constituting the heat-expandable microcapsule, but 90 to 18
The heating may be performed at 0 ° C. for about 1 to 5 minutes.

The heat-expandable microcapsule cannot be generally said depending on the type of resin constituting the resin layer and the thickness of the resin layer, but it is added to 100 parts by weight of all the resins constituting the resin layer containing the heat-expandable microcapsule. On the other hand, it is preferably contained in an amount of 0.5 to 25 parts by weight. When the amount is 0.5 parts by weight or more, curling can be corrected / prevented, and when the amount is 25 parts by weight or less, the strength of the resin layer can be maintained.

The heat-expandable microcapsules need only be contained in at least one resin layer, and need not be contained in all resin layers. For example, when the hard coat film has a subbing layer, a hard coat layer, and an overcoat layer on a flexible plastic film, the heat-expandable microcapsules are contained in at least one of these layers. If you have.

When the hard coat film has a resin layer that causes curling and a resin layer that does not cause curling, the heat-expandable microcapsules are not limited to the resin layer that causes curling, and may be contained in the resin layer that does not cause curling. Good. However, when the hard coat film has a resin layer on both sides of a flexible plastic film, the heat-expandable microcapsules are contained in the resin layer on the curling side so as to have a concave shape.
For example, when the hard coat film has a resin layer that curls into a concave shape by shrinking and a resin layer that does not curl on the same surface of the flexible plastic film, whichever resin layer contains the heat-expandable microcapsules. You may let me. In addition, the hard coat film has a resin layer that curls into a convex shape by absorbing moisture in the air on one surface of the flexible plastic film, and has a concave shape due to the influence of the resin layer on the other surface. In the case where the resin layer that curls is included in the above, the thermally expandable microcapsules are contained in the resin layer that curls in a concave shape.

Next, the curl correction / prevention method of the hard coat film of the present invention will be described. The curl correction / prevention method for a hard coat film of the present invention is characterized by thermally expanding the heat-expandable microcapsules contained in at least one resin layer of the above-mentioned hard coat film.

The heat-expandable microcapsules are thermally expanded in the process of forming the resin layer when the cause of the curl is in the process of forming the resin layer, and after forming the resin layer in the case of forming the resin layer. Thermally expand.

The means for thermally expanding the thermally expandable microcapsules is not particularly limited, and an oven, a heat press machine or the like can be used. The heating temperature and the heating time cannot be generally determined depending on the materials constituting the heat-expandable microcapsules, but are usually 90 to 180 ° C. and about 1 to 5 minutes. By such a method, curling of the hard coat film can be corrected / prevented.

The curl correction / prevention method for a hard coat film of the present invention is carried out by curling the above-mentioned hard coat film into a concave shape on the side of the resin layer containing the thermally expandable microcapsules, and then expanding the thermally expandable film. It is characterized in that the microcapsules are thermally expanded.

The means for thermally expanding the thermally expandable microcapsules is not particularly limited, and an oven or a heat press machine can be used. The heating temperature and the heating time cannot be generally determined depending on the materials constituting the heat-expandable microcapsules, but are usually 90 to 180 ° C. and about 1 to 5 minutes. By such a method, the curl generated on the hard coat film can be easily corrected.

Further, the curl correction / prevention method for a hard coat film of the present invention comprises the step of forming a resin layer which causes curling of the thermally expandable microcapsules contained in at least one resin layer of the hard coat film described above. It is characterized by thermal expansion.

The resin layer is formed by applying a coating material containing a resin, heat-expandable microcapsules, additives, a solvent, etc. onto a flexible plastic film and heating and drying. If necessary, the resin layer may be crosslinked and cured by heating, irradiation with ultraviolet rays, or the like after the formation. In order to thermally expand the heat-expandable microcapsules in the process of forming the curl-causing resin layer, when the heat-expandable microcapsules are contained in the curl-causing resin layer, the heat-drying of the resin layer should be 90-180. It suffices to carry out at a temperature of 1 to 5 minutes. When the heat-expandable microcapsule is contained in a resin layer other than the resin layer that causes curling, the heat-drying of the resin layer is performed at a temperature not higher than the expansion start temperature of the heat-expandable microcapsule to prevent curling of the resin layer. The heat drying is performed at 90 to 180 ° C. for about 1 to 5 minutes. The heating means is not particularly limited, and an oven or a heat press machine can be used. By such a method, it is possible to easily prevent curling from occurring during the production of the hard coat film.

[0038]

EXAMPLES The present invention will be further described below with reference to examples.
In addition, "part" and "%" are based on weight unless otherwise specified.

[Example 1] On a polyester film (Lumirror T60: Toray Co., Ltd.) having a thickness of 50 μm, a coating solution for an easy-adhesion layer having the following composition was applied by a bar coating method.
0 g / m ^{2 was} applied. Then, it was heated and dried at 80 ° C. for 5 minutes to form an easily adhesive layer without thermally expanding the thermally expandable microcapsules. Next, a hard coating layer coating solution having the following composition was coated on the easy-adhesion layer by a bar coating method at 40 g / m ² . Then, it was heated and dried at 150 ° C. for 3 minutes to form a hard coat layer while thermally expanding the thermally expandable microcapsules of the easy-adhesion layer to obtain a hard coat film.

<Easy adhesive layer coating liquid> ・ Acrylic-styrene copolymer (solid content 51%) 19 parts (Nikazor RX-552: Nippon Carbide Industry Co., Ltd.) ・ 1 part of thermal expansion microcapsule (Expansel (551) DU-20: Nippon Philite) ・ 80 parts of water

<Coating liquid for hard coat layer> ・ Acrylic polyol (solid content 50%) 31.0 parts (Acridic A801P: Dainippon Ink and Chemicals, Inc.) ・ Polyisocyanate (solid content 75%) 12.5 parts (Barnock DN950: Dainippon Ink and Chemicals, Inc.) ・ Methyl ethyl ketone 28.2 parts ・ Toluene 28.2 parts

[Example 2] On a polyester film (Lumirror S14: Toray Co., Ltd.) having a thickness of 50 µm, a coating liquid for an easy-adhesion layer having the following composition was applied by a bar coating method.
0 g / m ^{2 was} applied. Then, it was heated and dried at 80 ° C. for 5 minutes to form an easily adhesive layer without thermally expanding the thermally expandable microcapsules. Next, a hard coating layer coating liquid having the following composition was coated on the easy-adhesion layer by a bar coating method at 30 g / m ² . Then, it was heated and dried at 80 ° C. for 5 minutes to form a hard coat layer without thermally expanding the thermally expandable microcapsules of the easily adhesive layer. Next, when a hard coat film was produced by irradiating the hard coat layer with ultraviolet rays for 1 to 2 seconds to crosslink and harden the hard coat film, curl was generated so that the hard coat layer had a concave shape. Then, hard coat film at 150 ° C for 5
It was heated for a minute to thermally expand the thermally expandable microcapsules of the easily adhesive layer.

<Easy adhesive layer coating liquid> ・ Acrylic-styrene copolymer (solid content 51%) 19 parts (Nikazor RX-552: Nippon Carbide Industry Co., Ltd.) ・ 1 part of thermal expansion microcapsule (Expansel (551) DU-20: Nippon Philite) ・ 80 parts of water

<Coating liquid for hard coat layer> ・ Ionizing radiation curable resin 85.7 parts (Yupimer UV H6000DS: Mitsubishi Chemical, solid content 35%) ・ Initiator 0.9 parts (Dolphin Cure 651: Ciba Specialty Chemicals) ・ Isopropyl alcohol 14.3 parts

[Comparative Example 1] A hard coat film was obtained in the same manner as in Example 1 except that the heat-expandable microcapsules were removed from the coating solution for easily adhering layer of Example 1.

[Comparative Example 2] A hard coat film was obtained in the same manner as in Example 2 except that the heat-expandable microcapsules were removed from the coating solution for easily adhering layer of Example 2.

The curls of the hard coat films obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were evaluated by the following method. The hard coat film of Example 2 was evaluated after thermally expanding the thermally expandable microcapsules. The results are shown in Table 1.

[Curl Evaluation Method] A hard coat film was cut into a size of 150 mm × 150 mm to prepare a sample, which was allowed to stand on a horizontal and smooth table with the hard coat layer on top. Then, the lifting of the edge of the hard coat film from the table was measured, and the lifting 10
A value of 10 mm or less was evaluated as “◯”, and a value of 10 mm or more was evaluated as “x”.

[0049]

[Table 1]

The hard coat film of Example 1 contains thermally expandable microcapsules in the easily adhesive layer. Therefore, the obtained hard coat film was prevented from curling. In addition, according to the curl correction / prevention method for the hard coat film of Example 1, it was possible to easily prevent curling that occurs during the production of the hard coat film.

The hard coat film of Example 2 contains heat-expandable microcapsules which are not thermally expanded in the easy-adhesion layer at the stage where the hard coat layer is formed by drying by heating. Therefore, after forming the hard coat layer, the curl generated when the hard coat layer is cross-linked and cured by irradiation with ultraviolet rays can be corrected by thermally expanding the thermally expandable microcapsules. Further, according to the curl correction / prevention method for the hard coat film of Example 2, the curl generated in the hard coat film could be easily corrected.

Further, the hard coat films of Examples 1 and 2 were both excellent in surface hardness and satisfied the hard coat property.

Since the hard coat films of Examples 1 and 2 have no curl or can correct the curl even when the curl occurs, they are incorporated into electric / electronic parts. It did not cause any inconvenience and was extremely easy to handle.

On the other hand, the hard coat films of Comparative Examples 1 and 2 do not contain the thermally expandable microcapsules in the resin layer such as the hard coat layer. Therefore, none of them can prevent the occurrence of curling, and thus are inferior in handleability such as being difficult to incorporate in electric / electronic parts.

[0055]

Since the hard coat film of the present invention has the resin layer containing the heat-expandable microcapsules on the flexible plastic film, the obtained hard coat film is not curled. If there is no curl or the curl occurs, the curl can be corrected. Therefore, the hard coat film of the present invention is extremely excellent in handleability. Further, according to the curl correction / prevention method for a hard coat film of the present invention, the curl of the hard coat film can be easily corrected / prevented.

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Claims (4)

[Claims] 1. A hard coat film having at least one resin layer on a flexible plastic film, wherein at least one layer of the resin layers is a hard coat layer, and at least one of the resin layers. A hard coat film characterized by containing thermally expandable microcapsules in one layer. 2. A flexible plastic film having at least one resin layer, at least one of the resin layers being a hard coat layer, and at least one of the resin layers being heat-treated. A method for curl correction / prevention of a hard coat film, comprising the expandable microcapsule, which comprises thermally expanding the thermally expandable microcapsule. 3. A flexible plastic film having at least one or more resin layers, at least one of the resin layers being a hard coat layer, and at least one of the resin layers being heat-treated. A hard coat film containing expandable microcapsules, after being curled into a concave shape on the resin layer side containing the expandable microcapsules, the thermally expandable microcapsules are thermally expanded. Curling / prevention method for hard coat film. 4. A flexible plastic film having at least one resin layer, at least one of the resin layers being a hard coat layer, and at least one of the resin layers being heat-treated. Curling / prevention of a hard coat film containing expandable microcapsules, wherein the thermally expandable microcapsules are thermally expanded in the process of forming a resin layer in the resin layer that causes curling. Method.