JP6192255B2 - Method for producing hard coat film - Google Patents

Description

The present invention relates to a method for producing a hard coat film, a hard coat film, a polarizing plate, a front plate, and an image display device.

In an image display device such as a cathode ray tube display device (CRT), a liquid crystal display (LCD), a plasma display (PDP), an electroluminescence display (ELD), an electronic paper, etc., an optical laminate for preventing reflection is generally provided on the outermost surface. Is provided. Such an anti-reflection optical laminated body suppresses reflection of an image or reduces reflectance by scattering or interference of light.

Conventionally, it is known to use a triacetyl cellulose (TAC) substrate as a substrate film of such an optical laminate.
However, the triacetyl cellulose base material is inferior in heat-and-moisture resistance, and when the hard coat film is used as a polarizing plate protective film in a high-temperature and high-humidity environment, there is a drawback that the polarizing plate function such as polarizing function and hue is lowered.
For such a problem, it has been proposed to use a transparent plastic substrate mainly composed of an acrylic resin and / or a methacrylic resin.

However, in an optical laminate in which a hard coat layer is formed on one or both sides of a transparent plastic base material mainly composed of an acrylic resin and / or a methacrylic resin, the adhesion between the base material and the hard coat layer is poor. was there. In addition, a difference in refractive index occurs between the base material and the hard coat layer, and when a polarizing plate is formed using the optical layered body, there is a problem that interference fringes are generated and the appearance is poor.

To deal with such problems, for example, in Patent Document 1, in addition to physical treatment such as corona discharge treatment and oxidation treatment on a base film, a coating material called an anchor agent or primer is applied, It is disclosed to improve the adhesion between the base film and the hard coat layer by forming a coat layer.
However, in the method disclosed in Patent Document 1, the number of steps necessary for producing a hard coat film is increased, and special treatment is required, so that productivity is still lacking.

Moreover, for example, a method of forming irregularities at the interface between the base film and the hard coat layer is known (see, for example, Patent Document 2).
However, in such an optical laminate, it is not possible to form irregularities on the surface of the plastic substrate at the same time as forming a hard coat layer on the surface of the plastic substrate. It was necessary to form in advance. For this reason, the optical laminated body which prevented generation | occurrence | production of the interference fringe by forming an unevenness | corrugation in the conventional base film is not preferable in terms of manufacturing cost, and can be manufactured more simply and can suppress the generation of the interference fringe. The body was sought.

JP 2011-81359 A JP-A-8-197670

In view of the above situation, the present invention can produce a hard coat film that is excellent in adhesion between a base film made of a (meth) acrylic resin and a hard coat layer, and generation of interference fringes is sufficiently suppressed. In addition, a method for producing a hard coat film capable of simultaneously forming a hard coat layer on the base film and forming irregularities on the interface between the base film and the hard coat layer, and ( A hard coat film having irregularities at the interface between a base film made of a (meth) acrylic resin and a hard coat layer, excellent adhesion between the base film and the hard coat layer, and generation of interference fringes sufficiently suppressed An object of the present invention is to provide a polarizing plate and a front plate using the hard coat film, and an image display device.

As a result of intensive studies, the present inventors have applied a coating film formed by applying a hard coat layer forming composition for forming a hard coat layer on a base film made of a (meth) acrylic resin under predetermined conditions. It has been found that by drying, a hard coat layer having excellent adhesion can be formed on the base film, and irregularities capable of suppressing the generation of interference fringes can be formed at the interface between the base film and the hard coat layer. The invention has been completed.

That is, the present invention comprises a step of coating a hard coat layer composition containing a binder resin and a solvent on a base film made of a (meth) acrylic resin to form a coating film, It has a step of drying under conditions of a temperature of 90 to 110 ° C. and a time of 30 seconds to 10 minutes, and a step of curing the dried coating film to form a hard coat layer, and the solvent has a boiling point of 85 to 85. It is 165 degreeC and the glass transition temperature of the said base film is 110-140 degreeC, It is a manufacturing method of the hard coat film characterized by the above-mentioned .

In addition, as a result of intensive studies on a hard coat film having a hard coat layer on a base film made of a (meth) acrylic resin, the present inventors have found irregularities at the interface between the base film and the hard coat layer. The roughness curve of the unevenness has a specific relationship in the cross section between the base film and the hard coat layer, so that the adhesion between the base film and the hard coat layer is excellent, and the generation of interference fringes is suitable. It was found that the hard coat film of the present invention was completed.

That is, the present invention is a hard coat film having a base film made of (meth) acrylic resin and a hard coat layer formed on one surface of the base film, In the cross section in the thickness direction of the base film and the hard coat layer, in the direction perpendicular to the thickness direction of the base film and the hard coat layer. and taking the reference length (a), the ratio of the reference length (a) above the interface length in the and (B) (B / a) is Ri der 1.04 to 1.09, the hard coat The film is also a hard coat film characterized by having a haze of 0.7% or less and a total light transmittance of 90% or more .
In the hard coat film of the present invention, the hard coat layer comprises a hard coat layer composition containing a binder resin and a solvent, and the solvent has a boiling point of 85 to 165 ° C. ± 40 ° C. preferable.
Moreover, it is preferable that the glass transition temperature of the said base film is 110-140 degreeC.

Moreover, this invention is a polarizing plate provided with a polarizing element, Comprising: The polarizing plate characterized by providing the hard coat film of this invention on the surface of the said polarizing element.
Moreover, this invention is also a front plate characterized by hold | maintaining the hard coat film of this invention on the surface.
Furthermore, the present invention is also an image display device comprising the hard coat film of the present invention, the polarizing plate of the present invention, or the front plate of the present invention on the outermost surface.
Hereinafter, the present invention will be described in detail.

According to the method for producing a hard coat film of the present invention, a hard coat film having a hard coat layer on a base film made of a (meth) acrylic resin, having irregularities at the interface between the base film and the hard coat layer Can be formed. As a result, the hard coat film produced according to the present invention can suitably prevent the generation of interference fringes, and the formation of the hard coat layer and the formation of irregularities at the interface can be performed at a time. Therefore, the manufacturing cost is excellent, and the adhesion can be improved by increasing the contact area between the base film and the hard coat layer.

The unevenness formed at the interface between the base film of the hard coat film produced by the present invention and the hard coat layer will be described in more detail with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing a part of a hard coat film produced according to the present invention.
As shown in FIG. 1, the hard coat film 10 produced according to the present invention has an interface 13 between the base film 11 and the hard coat layer 12 in the cross section in the thickness direction of the base film 11 and the hard coat layer 12. Concavities and convexities 14 are formed.
The hard coat film produced according to the present invention has a reference length (A) in a direction perpendicular to the thickness direction of the base film 11 and the hard coat layer 12, and an interface within the reference length (A). When the length (B) of 13 (indicated by a thick line in FIG. 1) is taken, the ratio (B / A) of the reference length (A) to the length (B) is 1.04 to 1.09. It is preferable that
When the (B / A) is less than 1.04, the adhesion between the base film and the hard coat layer of the obtained hard coat film is inferior, and interference fringes cannot be sufficiently prevented. On the other hand, if it exceeds 1.09, the internal haze of the hard coat film becomes high, and the display image when the hard coat film is used causes a problem of whitening.

Here, the ratio between the reference length (A) and the interface length (B) can be measured, for example, by image analysis of the cross section using image analysis software (Image Pro, manufactured by Media Cybernetic). it can. Specifically, using the image obtained by cross-sectional observation with SEM or the like, using the image analysis software, the linear distance between the hard coat and the base film film end in the image is the reference length, and the image analysis is performed. The length (B) of the interface at the reference length (A) is measured using software, and (B / A) is calculated from the obtained value. More specifically, using the image analysis software Image-Pro Plus, Sharp Stack version 6.2, measure, calibrate, spatial calibration wizard, configure the active image, operate with the units (microns), and scale the SEM image Draw a definition line according to and calibrate. After calibration, the distance between the two ends of the interface is measured by distance measurement to obtain the reference length (A). Next, create a trace line by manual measurement (threshold = 3, smoothing = 0, speed = 3, noise = 5, automatic), measure the curve automatically by matching the standard to the end, and read the measured value The length of the interface (B). (B / A) is calculated from the obtained value.

The method for producing a hard coat film of the present invention comprises a step of coating a base film made of a (meth) acrylic resin with a hard coat layer composition containing a binder resin and a solvent to form a coating film. Have.
The base film made of the above (meth) acrylic resin, the hard coat film to be produced is superior in moisture and heat resistance and smoothness compared to a hard coat film having a base film made of TAC, and wrinkles are generated. Can be suitably prevented.
In the present specification, “(meth) acryl” means “acryl” and “methacryl”.

As acrylic resin which comprises the said base film, it is preferable that it is acrylic resin which has a ring structure, for example.
Although it does not specifically limit as acrylic resin which has the said ring structure, For example, the (meth) acrylic resin which has a lactone ring structure or the (meth) acrylic resin which has an imide ring structure is used suitably. The base film made of these (meth) acrylic resins is superior in mechanical strength and smoothness to the base film made of TAC, has low moisture permeability, and has high heat resistance in a high temperature environment. It is excellent in durability such as moisture resistance in a humid environment.

Examples of the (meth) acrylic resin having the lactone ring structure include, for example, JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, JP Examples thereof include (meth) acrylic resins having a lactone ring structure described in JP 2005-146084 A.

The (meth) acrylic resin having the lactone ring structure preferably has a lactone ring structure represented by the following general formula (1).

In General Formula (1), R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

The content of the lactone ring structure represented by the general formula (1) in the structure of the (meth) acrylic resin having the lactone ring structure is preferably 5 to 90% by mass, and 10 to 70% by mass. More preferably, it is more preferably 10 to 60% by mass, and most preferably 10 to 50% by mass. When the content of the lactone ring structure represented by the general formula (1) is less than 5% by mass, heat resistance, solvent resistance, and surface hardness may be insufficient. When the content exceeds 90% by mass, It may be inferior in moldability.

The (meth) acrylic resin having a lactone ring structure preferably has a mass average molecular weight of 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, and still more preferably 10,000 to 500,000. Most preferably, it is 50,000 to 500,000. When the mass average molecular weight of the (meth) acrylic resin having the lactone ring structure is out of the above range, the above-described effects of the present invention may not be sufficiently exhibited.

Examples of the (meth) acrylic resin having the imide ring structure include a (meth) acrylic resin having a glutarimide structure or an N-substituted maleimide structure.

The (meth) acrylic resin having the glutarimide structure preferably has a glutarimide structure represented by the following general formula (2).

In the general formula (2), R ⁴ and R ⁵ each independently represent a hydrogen atom or a methyl group, and R ⁶ represents a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, or cyclohexyl. Represents a group or a phenyl group.
Such a glutarimide structure can be formed, for example, by imidizing a (meth) acrylic acid ester polymer with an imidizing agent such as methylamine.

The (meth) acrylic resin having an N-substituted maleimide structure preferably has an N-substituted maleimide structure represented by the following general formula (3).

In the general formula (3), R ⁷ and R ⁸ each independently represent a hydrogen atom or a methyl group, and R ⁹ represents a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, or cyclohexyl. Represents a group or a phenyl group.
The acrylic resin having such an N-substituted maleimide structure in the main chain can be formed, for example, by copolymerizing N-substituted maleimide and (meth) acrylic acid ester.

Moreover, it is preferable that the said base film has a glass transition temperature (Tg) higher than what was used as a base film of the conventional hard coat film. When the base film has a higher Tg compared to the conventional film, the interface with the hard coat layer is not damaged by the solvent contained in the hard coat layer composition when the coating film described below is dried. Predetermined irregularities can be formed.
Specifically, the Tg of the substrate film is preferably 110 to 140 ° C. When the temperature is less than 110 ° C., the hard coat layer may be damaged by the solvent contained in the hard coat layer composition. On the other hand, when the temperature exceeds 140 ° C., the interface with the hard coat layer may be uneven. Sometimes it cannot be formed. The minimum with more preferable Tg of the said base film is 120 degreeC, and a more preferable upper limit is 130 degreeC.

As thickness of the said base film, it is preferable that it is 20-300 micrometers, More preferably, an upper limit is 200 micrometers and a minimum is 30 micrometers. When the thickness of the base film is less than 20 μm, wrinkles may occur in the hard coat film of the present invention. On the other hand, when the thickness exceeds 300 μm, the hard coat film of the present invention becomes thick and light transmittance, etc. Inferior optical properties.

The hard coat layer composition contains a binder resin and a solvent.
The binder resin is preferably transparent, for example, an ionizing radiation curable resin, an ionizing radiation curable resin and a solvent-drying resin (thermoplastic resin, etc.) that are cured by ultraviolet rays or an electron beam. It is possible to use a mixture with a resin or a thermosetting resin by simply drying the solvent added to adjust the solid content. More preferred is an ionizing radiation curable resin.
In the present specification, “resin” is a concept including resin components such as monomers and oligomers.

Examples of the ionizing radiation curable resin include compounds having one or more unsaturated bonds such as compounds having an acrylate functional group. Examples of the compound having one unsaturated bond include ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N-vinylpyrrolidone and the like. Examples of the compound having two or more unsaturated bonds include polymethylolpropane tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri ( Polyfunctional compounds such as (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, or the above polyfunctional compound and (meth) acrylate And the like (for example, poly (meth) acrylate esters of polyhydric alcohols).

In addition to the above compounds, relatively low molecular weight polyester resins having unsaturated double bonds, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins, etc. It can be used as an ionizing radiation curable resin.

The ionizing radiation curable resin can be used in combination with a solvent-drying resin. By using the solvent-drying resin in combination, film defects on the coated surface can be effectively prevented. The solvent-drying resin that can be used in combination with the ionizing radiation curable resin is not particularly limited, and a thermoplastic resin can be generally used.
The thermoplastic resin is not particularly limited. For example, a styrene resin, a (meth) acrylic resin, a vinyl acetate resin, a vinyl ether resin, a halogen-containing resin, an alicyclic olefin resin, a polycarbonate resin, or a polyester resin. Examples thereof include resins, polyamide-based resins, cellulose derivatives, silicone-based resins, rubbers, and elastomers. The thermoplastic resin is preferably amorphous and soluble in an organic solvent (particularly a common solvent capable of dissolving a plurality of polymers and curable compounds). In particular, from the viewpoints of film forming properties, transparency and weather resistance, styrene resins, (meth) acrylic resins, alicyclic olefin resins, polyester resins, cellulose derivatives (cellulose esters, etc.) and the like are preferable.

Thermosetting resins that can be used as the other binder resins include phenolic resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, aminoalkyd resin, and melamine-urea. A condensation resin, a silicon resin, a polysiloxane resin, etc. can be mentioned.

Although it does not specifically limit as said solvent, What has a comparatively high boiling point is preferable, Specifically, it is preferable that it is 85-165 degreeC. The hard coat layer composition contains a solvent having such a boiling point, and the drying conditions in the subsequent coating film drying step are within the ranges described below, the type of base film (Tg) and the type of binder resin. By appropriately adjusting according to the above, irregularities can be suitably formed at the interface between the base film and the hard coat layer.
Moreover, in this invention, it is preferable that it is +/- 40 degreeC as said solvent with respect to Tg of the said base film. Examples of the solvent having such a boiling point include methyl isobutyl ketone (boiling point 116 ° C.), dimethylformamide (boiling point 153 ° C.), cyclohexanone (boiling point 157 ° C.), isopropyl acetate (boiling point 88 ° C.), butyl acetate (boiling point 126 ° C.). ), Isobutyl acetate (boiling point 116 ° C.), propylene glycol monomethyl ether (boiling point 121 ° C.), propylene glycol monomethyl ether acetate (boiling point 146 ° C.), toluene (boiling point 110 ° C.) and the like. Of these, methyl isobutyl ketone and cyclohexanone are preferably used.

The hard coat layer composition preferably further contains a leveling agent.
By containing the leveling agent, the flatness of the hard coat layer can be improved and blocking of the hard coat film can be prevented.
Examples of the leveling agent include known ones such as a fluorine leveling agent, a silicone leveling agent, and an acrylic leveling agent. Among these, a fluorine-based leveling agent is preferable in that the stability of the ink and the stability of the coated surface can be ensured with a small addition amount.

It is preferable that content of the said leveling agent is 0.05-1 mass part with respect to 100 mass parts of binder resin solid content of the composition for hard-coat layers. If the amount is less than 0.05 parts by mass, the flatness of the hard coat layer may be deteriorated, and haze and unevenness may easily occur. On the other hand, if it exceeds 1 part by mass, the dispersibility and pot life of the hard coat layer composition are likely to deteriorate, and the haze of the hard coat layer may increase due to the aggregation of the anti-blocking agent described below and the adverse effect on the coating film. is there.

The hard coat layer composition may also contain an antiblocking agent.
Examples of the anti-blocking agent include particles such as silicon or styrene having no reactive group and an average primary particle size of 100 to 600 nm.
If the average primary particle size is less than 100 nm, the anti-blocking property may not be exhibited. If it exceeds 600 nm, the haze may be increased. The average primary particle size is more preferably 100 to 350 nm.
The average primary particle size is a value obtained by measuring with a laser diffraction scattering method particle size distribution measuring apparatus in a 5% by weight dispersion of methyl isobutyl ketone.

It is preferable that content of the said blocking inhibitor is 0.5-3 mass parts with respect to 100 mass parts of binder resin solid content of the composition for hard-coat layers. If it is less than 0.5 parts by mass, the anti-blocking property may not be exhibited. If it exceeds 3 parts by mass, the dispersibility is remarkably deteriorated, causing aggregation and gelation, and as a result, there is a possibility of leading to defects in the appearance of the hard coat film surface and an increase in haze.

The hard coat layer composition preferably further contains a photopolymerization initiator.
The photopolymerization initiator is not particularly limited as long as it is a known one. For example, acetophenones (for example, trade name Irgacure 184, 1-hydroxy-cyclohexyl-phenyl-ketone manufactured by Ciba Specialty Chemicals, Inc. Name Irgacure 907, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one), benzophenones, thioxanthones, benzoin, benzoin methyl ether, manufactured by Ciba Specialty Chemicals, Aromatic diazonium salts, aromatic sulfonium salts, aromatic iodonium salts, metathelone compounds, benzoin sulfonic acid esters and the like can be mentioned. Of these, acetophenones are preferable.

It is preferable that content of the said photoinitiator is 1-7 mass parts with respect to 100 mass parts of binder resin solid content in the composition for hard-coat layers. If the amount is less than 1 part by mass, the amount of the photopolymerization initiator may be insufficient, resulting in insufficient curing. When the amount exceeds 7 parts by mass, the photopolymerization initiator becomes excessive, and a difference in the photopolymerization reaction due to the excess is caused.
The content of the photopolymerization initiator is more preferably 2 to 5 parts by mass with respect to 100 parts by mass of the resin solid content.

The composition for hard coat layers may further contain other components as necessary in addition to the components described above.
Examples of the other components include a thermal polymerization initiator, an ultraviolet absorber, a light stabilizer, a crosslinking agent, a curing agent, a polymerization accelerator, a viscosity modifier, an antistatic agent, an antioxidant, an antifouling agent, a slip agent, A refractive index adjusting agent, a dispersing agent, etc. can be mentioned. These can use a well-known thing.

The hard coat layer composition preferably has a total solid content of 20 to 50%. If it is lower than 20%, residual solvent may remain or whitening may occur. If it exceeds 50%, the viscosity of the composition for hard coat layer is increased, the coating property is lowered and unevenness and streaks may appear on the surface, or interference fringes may be generated. The solid content is more preferably 30 to 45%.

The hard coat layer composition can be prepared by mixing and dispersing the binder resin, leveling agent, anti-blocking agent, photopolymerization initiator, and other components in a solvent.
The mixing and dispersing may be performed using a known apparatus such as a paint shaker, a bead mill, a kneader.

Examples of a method for forming a coating film by applying the hard coat layer composition include, for example, a spin coating method, a dip method, a spray method, a die coating method, a bar coating method, a roll coater method, a meniscus coater method, and a flexographic printing method. And various known methods such as a screen printing method and a bead coater method.

Moreover, it is preferable that the application quantity (dry application quantity) of the said composition for hard-coat layers is 3-15 g / m < ² >. If it is less than 3 g / m ² , a hard coat layer having a desired hardness may not be obtained. If it exceeds 15 g / m ² , curling and damage may be insufficiently prevented. The coating amount is more preferably 4 to 10 g / m ² .

The manufacturing method of the hard coat film of this invention has the process of drying the said coating film on the conditions of temperature 90-110 degreeC and time 30 seconds-10 minutes.
By drying the coating film formed on the base film under the above conditions, irregularities can be formed at the interface between the base film and the dried coating film.
When the drying temperature is less than 90 ° C. or the drying time is less than 30 seconds, the formation of the unevenness becomes insufficient, and the adhesion between the base film and the hard coat layer of the obtained hard coat film becomes insufficient. Also, the interference fringe prevention property is insufficient. On the other hand, if the drying temperature exceeds 110 ° C. or the drying time exceeds 10 minutes, the productivity is inferior, the Tg of the base film becomes close, the base film becomes brittle, the unevenness can be excessive, and whitening occurs. There is a risk of doing. It is preferable that the drying temperature of the said coating film is 100-110 degreeC, and the preferable minimum of the drying time of the said coating film is 1 minute, and a preferable upper limit is 5 minutes.
The base film and the coating film are selected by appropriately selecting an appropriate drying temperature and drying time according to the type of binder resin and solvent used in the hard coat layer composition and the type of base film. Predetermined irregularities as described with reference to FIG. 1 can be formed at the interface with the film.

The reason why irregularities are formed at the interface between the base film and the dried coating film by drying the coating film under the above conditions is estimated as follows.
That is, the Tg of the base film is close to the drying temperature, and the base film is affected. The base film is slightly close to the state allowing the solvent to penetrate and / or swell. Presumed to be slightly softened by approaching Tg, and by using the solvent having the boiling point described above, the solvent concentration of the coating film during drying at a high drying temperature is prevented from rapidly decreasing, and slightly By swelling and eroding the base film, it is estimated that as a result, irregularities are formed at the interface.

The manufacturing method of the hard coat film of this invention has the process of curing the dried said coating film and forming a hard-coat layer.
As a method for curing the coating film, a known method may be appropriately selected according to the contents of the hard coat layer composition. For example, if the binder resin contained in the hard coat layer composition is of an ultraviolet curable type, the coating film may be cured by irradiating with ultraviolet rays.
When irradiating the ultraviolet light is preferably ultraviolet irradiation amount is 80 mJ / cm ² or more, more preferably 100 mJ / cm ² or more, more preferably 130 mJ / cm ² or more.

The hard coat layer preferably has a layer thickness of 3 to 15 μm.
If it is less than 3 μm, the hardness may be insufficient. If it exceeds 15 μm, residual solvent may remain or coating film adhesion may be reduced. The lower limit of the thickness of the hard coat layer is more preferably 4 to 10 μm.
The layer thickness is a value obtained by measuring the cross section of the hard coat layer with an electron microscope (SEM, TEM, STEM).

Further, the hard coat film obtained by the present invention preferably has a hardness of 3H or more in a pencil hardness test (load 4.9N) according to JIS K5600-5-4 (1999), preferably 4H or more. Is more preferable.

The hard coat film preferably has a total light transmittance of 90% or more. If it is less than 90%, color reproducibility and visibility may be impaired when mounted on the display surface, and a desired contrast may not be obtained. The total light transmittance is more preferably 91% or more.
The total light transmittance can be measured by a method based on JIS K-7361 using a haze meter (manufactured by Murakami Color Research Laboratory, product number: HM-150).

The hard coat film preferably has a haze of 0.7% or less. If it exceeds 0.7%, desired optical characteristics cannot be obtained, and visibility when the hard coat film is placed on the image display surface is lowered. The minimum with said more preferable haze is 0.1%, and a more preferable upper limit is 0.5%.
In addition, the said haze can be measured by the method based on JISK-7136 using a haze meter (the product number; HM-150 made by Murakami Color Research Laboratory).

The hard coat film may also have other layers (antiglare layer, antistatic layer, low refractive index layer, antifouling layer, adhesive layer, etc.) as necessary within the range not impairing the effects of the present invention. 1 layer or two or more layers of a hard coat layer, etc.) may be appropriately formed. Among these, it is preferable to have at least one of an antiglare layer, an antistatic layer, a low refractive index layer, and an antifouling layer. These layers may be the same as those of a known antireflection laminate.

According to such a method for producing a hard coat film of the present invention, the formation of irregularities as shown in FIG. 1 at the interface between the base film made of (meth) acrylic resin and the hard coat layer, Since the formation can be performed at a time, the manufacturing cost is extremely excellent, and the manufactured hard coat film can effectively suppress the generation of interference fringes.
Moreover, since the said hard coat film is what the unevenness | corrugation was formed in the interface of the said base film and a hard-coat layer, the contact area of this base film and a hard-coat layer increases, and adhesiveness is extremely It will be excellent.
Such an improvement in adhesion between the base film and the hard coat layer is achieved by the formation of the hard coat layer on the base film and the unevenness at the interface between the base film and the hard coat layer as in the present invention. It can be obtained by performing the formation at once. That is, when the unevenness is previously formed on the base film and the hard coat layer is formed on the surface having the pre-formed unevenness of the base film as in the conventional hard coat film, Adhesion with the coat layer cannot be sufficiently improved. This is because the coating solution is applied to the substrate film and dried and cured while creating irregularities. The substrate erodes (penetrates and swells) depending on the solvent and temperature. It is presumed that the interaction between the two works in the vicinity of the interface, leading to improved adhesion.

Next, the hard coat film of the present invention will be described.
The hard coat film of the present invention is a hard coat film having a base film made of (meth) acrylic resin and a hard coat layer formed on one surface of the base film, It has unevenness at the interface between the film and the hard coat layer, and is perpendicular to the thickness direction of the base film and the hard coat layer in the cross section in the thickness direction of the base film and the hard coat layer. The ratio (B / A) between the reference length (A) taken in the direction and the length (B) of the interface in the reference length (A) is 1.04 to 1.09. It is what.

In the hard coat film of the present invention, the reference length (A), the interface length (B), and the ratio (B / A) thereof are as described with reference to FIG.
In addition, the base film made of (meth) acrylic resin and the hard coat layer in the hard coat film of the present invention are the same as those described in the above-described method for producing a hard coat film of the present invention.

Such a hard coat film of this invention can be manufactured with the manufacturing method of the hard coat film of this invention mentioned above.

The hard coat film of the present invention can be suitably used for a polarizing plate.
Examples of the polarizing plate using the hard coat film of the present invention include a polarizing plate provided with a polarizing element and the surface of the polarizing element provided with the hard coat film of the present invention.
A polarizing plate using such a hard coat film of the present invention is also one aspect of the present invention.

The polarizing element is not particularly limited, and for example, a polyvinyl alcohol film, a polyvinyl formal film, a polyvinyl acetal film, an ethylene-vinyl acetate copolymer saponified film, etc. dyed and stretched with iodine or the like can be used. In laminating the polarizing element and the hard coat film of the present invention, it is preferable to saponify the light-transmitting substrate. By the saponification treatment, the adhesiveness is improved and an antistatic effect can be obtained.

The present invention is also an image display device comprising the hard coat film of the present invention, the polarizing plate of the present invention, or the front plate of the present invention on the outermost surface.
Examples of the image display device include LCD, PDP, FED, ELD (organic EL, inorganic EL), CRT, touch panel, and electronic paper.

The LCD includes a transmissive display body and a light source device that irradiates the transmissive display body from the back. When the image display device of the present invention is an LCD, the hard coat film, the polarizing plate or the front plate of the present invention is formed on the surface of the transparent display body.

When the present invention is a liquid crystal display device having the hard coat film, the light source of the light source device is irradiated from the lower side (base material side) of the hard coat film. Note that in the STN liquid crystal display device, a retardation plate may be inserted between the liquid crystal display element and the polarizing plate. An adhesive layer may be provided between the layers of the liquid crystal display device as necessary.

The PDP includes a front glass substrate and a rear glass substrate disposed with a discharge gas sealed between the front glass substrate and the front glass substrate. When the image display device of the present invention is a PDP, the surface of the surface glass substrate or the front plate (glass substrate or film substrate) is provided with the hard coat film described above.
The front plate holding the hard coat film of the present invention on its surface is also one aspect of the present invention.

Other image display devices are ELD devices that emit light when zinc is applied, such as zinc sulfide or diamine substances, deposited on a glass substrate, and display the voltage by controlling the voltage applied to the substrate. It may be an image display device such as a CRT that generates an image visible to human eyes. In this case, the hard coat film described above is provided on the outermost surface of each display device as described above or the surface of the front plate.

In any case, the hard coat film of the present invention can be used for display display of a television or a computer. In particular, it can be suitably used for the surface of a high-definition image display such as a liquid crystal panel, PDP, ELD, touch panel, and electronic paper.

The method for producing a hard coat film of the present invention comprises forming a hard coat layer on one surface of a base film made of a (meth) acrylic resin, and providing a predetermined at the interface between the base film and the hard coat layer. Since the formation of irregularities can be performed at a time, the manufacturing cost is excellent, and the obtained hard coat film can suitably prevent the occurrence of interference fringes. Furthermore, the hard coat film obtained by the present invention can be extremely excellent in the adhesion between the base film and the film layer.
In the hard coat film of the present invention, predetermined irregularities were formed between the base film made of (meth) acrylic resin and the hard coat layer formed on one surface of the base film. Therefore, the occurrence of interference fringes can be prevented, and the adhesion between the base film and the hard coat layer is extremely excellent.
For this reason, the hard coat film of the present invention is used for displays such as cathode ray tube display (CRT), liquid crystal display (LCD), plasma display (PDP), electroluminescence display (ELD), and electronic paper, particularly high definition display. It can be preferably used.

Sectional drawing which showed typically a part of hard coat film manufactured by the manufacturing method of the hard coat film of this invention.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples and comparative examples.
In the text, “part” or “%” is based on mass unless otherwise specified.

Example 1
4 parts by mass of Irgacure 184 (photopolymerization initiator, manufactured by BASF Japan Ltd.) was added to methyl isobutyl ketone (MIBK), and dissolved by stirring to prepare a solution having a final solid content of 40% by mass. To this solution, pentaerythritol triacrylate (PETA) was added as a resin component and stirred. To this solution, 0.1 part by mass of a leveling agent (product name: Defenza MCF350-5; manufactured by DIC) was added in a solid content ratio and stirred to prepare a composition for a hard coat layer.
The composition for hard coat layer was applied on an acrylic substrate (thickness 40 μm, Tg = 125 ° C.) by slit reverse coating to form a dry coating amount of 8 g / m ² to form a coating film. After drying the obtained coating film at 100 ° C. for 1 minute, the coating film was cured by irradiating with ultraviolet rays at an ultraviolet irradiation amount of 150 mJ / cm ² to form a hard coat layer having a thickness of 7 μm. A coated film was obtained.

(Example 2)
A hard coat film was obtained in the same manner as in Example 1 using the composition for hard coat layer prepared in the same manner as in Example 1 except that methyl isobutyl ketone (MIBK) was changed to cyclohexanone.

(Example 3)
A hard coat film was prepared in the same manner as in Example 1 except that the pentaerythritol triacrylate (PETA) was changed to dipentaerythritol hexaacrylate (DPHA). Got.

Example 4
A hard coat film was obtained in the same manner as in Example 1 except that the drying time of the coating film was 2 minutes.

(Example 5)
A hard coat film was obtained in the same manner as in Example 1 except that the drying temperature of the coating film was 95 ° C.

(Example 6)
A hard coat film was obtained in the same manner as in Example 1 except that the drying temperature of the coating film was 110 ° C.

(Example 7)
A hard coat film was obtained in the same manner as in Example 1 except that the drying time of the coating film was 10 minutes.

(Comparative Example 1)
A hard coat film was obtained in the same manner as in Example 1 except that the drying temperature of the coating film was set to 70 ° C.

(Comparative Example 2)
A hard coat film was obtained in the same manner as in Example 1 except that pentaerythritol triacrylate (PETA) was changed to dipentaerythritol hexaacrylate (DPHA) and the drying temperature of the coating film was set to 70 ° C.

(Comparative Example 3)
A hard coat film was obtained in the same manner as in Example 1 except that the drying time of the coating film was 30 seconds.

(Comparative Example 4)
A hard coat film was obtained in the same manner as in Example 1 except that the drying temperature of the coating film was 120 ° C.

(Comparative Example 5)
A hard coat film was obtained in the same manner as in Example 1 except that the drying time of the coating film was 15 minutes.

(Reference Example 1)
A hard coat film was obtained in the same manner as in Example 1 except that the composition for hard coat layer was prepared in the same manner as in Example 1 except that methyl isobutyl ketone (MIBK) was changed to methyl ethyl ketone (MEK).

The following evaluation was performed about the hard coat film obtained by the Example and the comparative example. The results are shown in Table 1.

(Adhesion)
In accordance with JIS K5600, crosscut CCJ-1 (manufactured by Cortec Co., Ltd.) is used, a grid-like cut is made on the surface of the hard coat layer of the obtained hard coat film, and 100 squares of 1 mm square are produced. Nichiban Industrial 24mm wide cello tape (registered trademark) is applied on the grid, and then it is rubbed back and forth 10 times with a spatula to make it come in close contact and rapidly peel off in the direction of 150 °, and the same operation is repeated 5 times. Count the number of remaining squares. Using the number of remaining squares as the numerator and the total number of squares as the denominator, the following criteria were used for evaluation.
○: 100/100
×: Less than 100/100

(Haze)
Using a haze meter (manufactured by Murakami Color Research Laboratory, product number: HM-150), haze was determined according to JIS K-7136.

(Total light transmittance)
The total light transmittance was calculated | required by the method based on JISK-7361 using the haze meter (Murakami Color Research Laboratory make, product number; HM-150).

(Ratio with the length (B) of the interface within the reference length (A) (B / A))
The reference length (A) taken in the direction perpendicular to the thickness direction of the hard coat layer obtained by the method described with reference to FIG. 1 and the length of the interface (B) within the reference length (A) ) (B / A).

As shown in Table 1, the hard coat films according to the examples had excellent adhesion, low haze, and sufficiently high total light transmittance. In addition, interference fringes were not confirmed in the hard coat film according to the example.
On the other hand, the hard coat films according to Comparative Examples 1 to 3 had insufficient adhesion, and the hard coat films according to Comparative Examples 4 and 5 had high haze.
Further, the hard coat film according to Reference Example 1 using MEK (boiling point: 79.5 ° C.) having a low boiling point as the solvent was inferior in adhesion.

The hard coat film of the present invention is suitable for a cathode ray tube display (CRT), a liquid crystal display (LCD), a plasma display (PDP), an electroluminescence display (ELD), a touch panel, an electronic paper or the like, particularly a high definition display. Can be used for

DESCRIPTION OF SYMBOLS 10 Hard coat film 11 Base film 12 Hard coat layer 13 Interface 14 Unevenness

Claims (1)

A step of coating a base film made of a (meth) acrylic resin with a hard coat layer composition containing a binder resin and a solvent to form a coating film;
Drying the coating film at a temperature of 90 to 110 ° C. for 1 to 10 minutes; and
A step of curing the dried coating film to form a hard coat layer;
The solvent has a boiling point of 85 to 165 ° C,
The glass transition temperature of the said base film is 110-140 degreeC, The manufacturing method of the hard coat film characterized by the above-mentioned.

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