JP2015217654A - Hard coat film, front plate of display element and display device using the same, and method for improving peel resistance of coating film of thin hard coat film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hard coat film which satisfies visibility with polarized sunglasses, thinness, and peel resistance of a coating film.SOLUTION: The hard coat film comprises one or more resin layers including a hard coat layer on a stretched polyester film having a thickness of 4 to 12 μm and a degree of orientation of 2.0 or less. The hard coat layer is formed of a hard coat-forming composition containing an ionizing radiation-curable resin A. The one or more resin layers have a curling value of 14 mm or less as measured by the following conditions, and a ratio of [thickness of stretched polyester film]/[thickness of hard coat layer] is 0.7 to 4.0. (Curling value): compositions which form each layer of the one or more resin layers are coated on a stretched polyester film having a thickness of 25 μm and a degree of orientation of 1.5, dried, and irradiated with ionizing radiation to form respective layers in order and allowed to stand for 5 minutes. Thereafter, a sample of 10 cm square is cut out, and the sample is placed on a horizontal rack so that the polyester side faces the rack. Height of four corners of the sample which are lifted up from the rack is measured, and an average of the four corners is taken as the curling value of the sample.

Description

  The present invention relates to a hard coat film, a front plate and a display device of a display element using the same, and a method for improving the peel resistance of a thin hard coat film.

  In recent years, the use of liquid crystal display devices (LCDs) has been expanded, and the use of smartphones and the like used outdoors has also expanded. In recent years, there has been an increasing demand for miniaturization and thinning.

  Such an LCD performs display by transmitting / shielding light generated by a light source such as external light or a front light or a backlight to a liquid crystal panel having a liquid crystal cell sandwiched between two polarizing plates. Due to such a structure, when the LCD is observed with the polarized sunglasses on, the observer views the linearly polarized light emitted from the LCD through the polarized sunglasses. At this time, there is a problem that the screen becomes invisible (visibility is lowered) depending on the angle formed between the polarizing plate absorption axis on the LCD viewer side and the absorption axis of the polarized sunglasses.

In order to solve the problem of the decrease in visibility, a technique using a λ / 4 retardation film using a cycloolefin polymer has been proposed as in Patent Document 1. In addition, as in Patent Document 2, a technique using a polyester resin having high retardation has been proposed.
However, the cycloolefin polymer used in Patent Document 1 is originally brittle and lacks toughness, but the problem becomes serious when the thickness is reduced.
On the other hand, the polyester resin used in Patent Document 2 has no problem regarding physical strength such as toughness and rigidity, but it is difficult to achieve both high retardation and thin film.

JP 2011-1113018 A JP2011-107198A

The present inventors have examined a material having physical strength that can be used for polarized sunglasses and that can withstand use even at a thickness of 20 μm or less in order to meet the demand for thinning.
Specifically, intensive studies were conducted using stretched polyester films (PET, PEN, etc.). Since the stretched polyester film has large anisotropy, it can be thinned to a thickness of 4 to 12 μm while securing a quarter wavelength, and further has excellent solvent resistance and flexibility, and is also suitable for processing. It is excellent.

On the other hand, a stretched polyester film having a thickness of 4 to 12 μm is not sufficient in rigidity and hardness. For this reason, the present inventors studied to provide a hard coat layer on the polyester film.
However, when a hard coat layer was provided on the polyester film, a phenomenon occurred in which the coating film (hard coat layer or the like) on the polyester film peeled even when the primer layer was provided.

The present inventors examined the cause of peeling of the coating film on a stretched polyester film having a thickness of 4 to 12 μm. As a result, first, it was found that the peeling interface of the laminate having the primer layer and the hard coat layer on the polyester film was an interface between the polyester film and the primer layer. And the fact that peeling has occurred at the interface (the interface between the polyester film and the primer layer) that is originally excellent in adhesion and good in peel resistance is that a hard coat layer is formed on a stretched polyester film having a thickness of 4 to 12 μm. In the case of forming, it has been found that an exfoliation resistance higher than usual is required.
As a result of further research, although the base material relaxed the stress generated when the hard coat layer was cured and shrunk in the thick base material, the thin base material could hardly relieve the stress. It was found that the stress applied to the coating film interface was the cause of the peeling of not only the hard coat layer but the entire coating film on the substrate.

As described above, the inventors of the present invention have solved this problem in the development of a hard coat film that simultaneously satisfies the requirements for polarized sunglasses, thickness reduction, and peeling resistance of the coating film.
That is, the hard coat film of the present invention, the front plate and display device of the display element using the same, and the method for improving the peel resistance of the thin hard coat film are as described in [1] to [15] below. It is.

[1] One or more resin layers including a hard coat layer are formed on a stretched polyester film having a thickness of 4 to 12 μm and an orientation degree of 2.0 or less, and the hard coat layer is an ionizing radiation curable resin. A curl value measured by the following conditions is 14 mm or less, and [thickness of stretched polyester film] / [hard coat layer] is formed from a hard coat layer forming composition containing A. A hard coat film having a ratio of [thickness] of 0.7 to 4.0.
(Curl value)
The composition forming each layer constituting the one or more resin layers is coated on a stretched polyester film having a thickness of 25 μm and an orientation degree of 1.5, dried and irradiated with ionizing radiation to form each layer in order, and left for 5 minutes. After the sample is cut out in a 10 cm square, the sample is placed on a horizontal table so that the polyester film side faces the table side. The height at which the four corners of the sample float from the table is measured, and the average value of the four corners is taken as the curl value of the sample.

[2] The one or more resin layers include a primer layer on the stretched polyester film side from the hard coat layer, and the primer layer is formed from a primer layer forming composition containing an ionizing radiation curable resin B. The hard coat film according to the above [1].
[3] The hard coat film according to [2], wherein the ionizing radiation curable resin B includes a urethane (meth) acrylate oligomer and a polyester (meth) acrylate monomer.
[4] The hard coat according to any one of the above [1] to [3], wherein the hard coat layer is formed from a hard coat layer forming composition containing an ionizing radiation curable resin A and a thermoplastic resin A. the film.
[5] The hard coat film according to [4], wherein the thermoplastic resin A is a thermoplastic resin having no reactive functional group in the molecule.
[6] The hard coat film according to [4] or [5], wherein the thermoplastic resin A is polymethyl methacrylate.
[7] In any one of the above [4] to [6], the mass ratio of the ionizing radiation curable resin A and the thermoplastic resin A in the hard coat layer forming composition is 5: 5 to 9: 1. The hard coat film as described.

[8] The hard coat film according to any one of [1] to [7], wherein the one or more resin layers include a thermoplastic resin layer closer to the stretched polyester film than the hard coat layer.
[9] The hard coat film according to [8], wherein the one or more resin layers include the primer layer, the thermoplastic resin layer, and the hard coat layer in this order from the stretched polyester film side.
[10] The above-mentioned [8] or [9], wherein the thermoplastic resin layer contains the thermoplastic resin B, and the thermoplastic resin layer B is a thermoplastic resin having no reactive functional group in the molecule. ] The hard coat film as described in.
[11] The above [8] to [8], wherein the thermoplastic resin layer contains a conductive agent, the hard coat layer contains conductive fine particles, and the thermoplastic resin layer and the hard coat layer surface are electrically connected. 10]. The hard coat film according to any one of [10].
[12] The hard coat film according to the above [11], which is grounded from the surface of the hard coat layer.

[13] A front plate of a display element, which is formed by laminating a polarizing plate and the hard coat film according to any one of [1] to [12].
[14] A display device comprising the hard coat film according to any one of [1] to [12] on a front surface of a display element.
[15] A stretched polyester film having a thickness of 4 to 12 μm and an orientation degree of 2.0 or less has one or more resin layers including a hard coat layer, and the hard coat layer is an ionizing radiation curable resin. When producing a hard coat film formed from a hard coat layer forming composition containing A, the hard coat layer is formed from a hard coat layer forming composition containing an ionizing radiation curable resin, and the one or more resins A layer having a curl value measured under the following conditions of 14 mm or less is selected, and the ratio of [stretched polyester film thickness] / [hard coat layer thickness] is 0.7 to 4.0. A method for improving the peel resistance of a hard coat film.
[Curl value]
The composition forming each layer constituting the one or more resin layers is coated on a stretched polyester film having a thickness of 25 μm and an orientation degree of 1.5, dried and irradiated with ionizing radiation to form each layer in order, and left for 5 minutes. After the sample is cut out in a 10 cm square, the sample is placed on a horizontal table so that the polyester film side faces the table side. The height at which the four corners of the sample float from the table is measured, and the average value of the four corners is taken as the curl value of the sample.

  The hard coat film of the present invention, the front plate and display device of the display element using the same, and the method for improving the adhesion of the thin hard coat film are the visibility, thinning and anti-peeling resistance of the paint film with polarized sunglasses. Sex can be satisfied at the same time.

[Hard coat film]
The hard coat film of the present invention has one or more resin layers (hereinafter simply referred to as “resin layer”) including a hard coat layer on a stretched polyester film having a thickness of 4 to 12 μm and an orientation degree of 2.0 or less. The hard coat layer is formed from a hard coat layer forming composition containing the ionizing radiation curable resin A, and the curl value measured by the one or more resin layers under the following conditions is 14 mm. The ratio of [thickness of stretched polyester film] / [thickness of hard coat layer] is 0.7 to 4.0.
(Curl value)
The composition forming each layer constituting the one or more resin layers is coated on a stretched polyester film having a thickness of 25 μm and an orientation degree of 1.5, dried and irradiated with ionizing radiation to form each layer in order, and left for 5 minutes. After the sample is cut out in a 10 cm square, the sample is placed on a horizontal table so that the polyester film side faces the table side. The height at which the four corners of the sample float from the table is measured, and the average value of the four corners is taken as the curl value of the sample.

Although the hard coat film of the present invention may be used on the outermost surface of the display like a normal hard coat film, it is not always the best in consideration of the problems of visibility by polarizing sunglasses, thinning, and peeling resistance of the coating film. There is no need to use it on the surface. For example, in the case of a liquid crystal display, it may be used anywhere as long as it is opposite to the backlight of the liquid crystal element. As will be described later, when the hard coat film of the present invention is used as a protective film for a polarizing plate, the visibility of polarized sunglasses can be improved while making the entire display thinner.
Since the hard coat film of the present invention is used as described above, hardness which is a performance required for a normal hard coat film is not so important. In order to eliminate inconveniences in the process, it is preferable to improve the rigidity and toughness.

<Stretched polyester film>
A stretched polyester film having a thickness of 4 to 12 μm and an orientation degree of 2.0 or less is used.

A stretched polyester film having a thickness of 4 to 12 μm becomes a substantially ¼ wavelength phase difference film having a phase difference of 550 nm of about 80 to 170 nm, and can prevent a decrease in visibility due to polarized sunglasses. The stretched polyester film preferably has a thickness of 5 to 12 μm.
When a resin layer such as a hard coat layer is formed on such a thin stretched polyester film, as described above, the stretched polyester film cannot relieve stress due to shrinkage of the hard coat layer, and is formed on the film. All the resin layers such as the hard coat layer are peeled off. However, when the resin layer satisfies the condition of the curl value described later, the peel resistance can be improved.
Even when a cycloolefin polymer and a polycarbonate are used, it is possible to obtain a substantially quarter-wave retardation film having a thickness of 4 to 12 μm and a retardation of 550 nm of about 80 to 170 nm. However, cycloolefin polymers are extremely fragile and cannot be used, and polycarbonate is inferior in solvent resistance. If the substrate thickness is too thin, the substrate may be broken by solvent and tension when the resin layer is applied. There is no use.

Moreover, peeling resistance can be made favorable by the orientation degree of a stretched polyester film being 2.0 or less.
The degree of orientation, when the maximum value of the surface orientation parameter Y of the stretched polyester film Y _max, the minimum value Y _min, which is a value represented by Y _max / Y _min. The surface orientation parameter Y is an absorption intensity (I ₁₃₄₀ ) at ₁₃₄₀ cm ⁻¹ on the one-time reflection spectrum of the FTIR-S polarized ATR method measured by rotating the stretched polyester film surface in-plane every 10 ° as an orientation parameter. And the absorption intensity (I ₁₄₁₀ ) at ₁₄₁₀ cm ⁻¹ [I ₁₃₄₀ / I ₁₄₁₀ ]. More specifically, it can be determined by the method described in the examples.

The stretched polyester film described above can be formed, for example, by stretching a polyester film such as polyethylene terephthalate, polyethylene naphthalate, or polyethylene terephthalate uniaxially or biaxially. The stretched polyester film is preferably biaxially stretched from the viewpoints of solvent resistance, processability and the like.
The degree of orientation of the stretched polyester film correlates with the difference in magnification between longitudinal stretching (stretching in the orientation axis direction) and lateral stretching. That is, the orientation degree can be reduced by reducing the magnification difference between the longitudinal stretching and the transverse stretching, and the orientation degree can be increased by increasing the magnification difference between the longitudinal stretching and the transverse stretching.
Further, the phase difference of 550 nm of the stretched polyester film can be increased by increasing the stretch ratio, increasing the difference between the longitudinal stretch and the lateral stretch, etc., decreasing the stretch ratio, and the longitudinal stretch and the lateral stretch. It can be made smaller by reducing the difference in magnification.

The stretched polyester film preferably contains an ultraviolet absorber. The ultraviolet absorber is not particularly limited, and an organic or inorganic ultraviolet absorber can be used. Among these, an organic ultraviolet absorber having excellent transparency is preferably used. A benzotriazole type ultraviolet absorber, a benzophenone type ultraviolet absorber, etc. can be used for an ultraviolet absorber.
Content of a ultraviolet absorber is about 3-15 mass% in a stretched polyester film.

The stretched polyester film preferably has a peelable base material laminated on the surface opposite to the surface having the resin layer in order to improve the peel resistance and handling properties of the resin layer.
The timing of laminating the peelable substrate on the stretched polyester film may be before or after the formation of the resin layer such as the hard coat layer, but may be after the formation of the resin layer. From the viewpoint, it is preferable before the resin layer is formed.
The peelable substrate is formed after the resin layer is formed, after the hard coat film is slit to a predetermined width, or after the hard coat film is cut into a predetermined size, or the hard coat film is applied to a polarizing plate or the like. What is necessary is just to peel from a stretched polyester film, after bonding to a body.

<One or more resin layers>
Although the stretched polyester film having a thickness of 4 to 12 μm or less and an orientation degree of 2.0 or less can improve the visibility by polarized sunglasses and can be thinned, a resin layer such as a hard coat layer is provided. In some cases, there is a problem that the resin layer peels off. Therefore, the present invention prevents the resin layer from peeling off, assuming that one or more resin layers including the hard coat layer satisfy a predetermined condition.
Specifically, in the present invention, one or more resin layers including the hard coat layer have a curl value measured under the following conditions of 14 mm or less. The curl value is preferably 10 μm or less, and more preferably 8 μm or less.
(Curl value)
The composition forming each layer constituting the one or more resin layers is coated on a stretched polyester film having a thickness of 25 μm and an orientation degree of 1.5, dried and irradiated with ionizing radiation to form each layer in order, and left for 5 minutes. After the sample is cut out in a 10 cm square, the sample is placed on a horizontal table so that the polyester film side faces the table side. The height at which the four corners of the sample float from the table is measured, and the average value of the four corners is taken as the curl value of the sample.

In the measurement of the curl value, the drying conditions of one or more resin layers provided on a stretched polyester film having a thickness of 25 μm and an orientation degree of 1.5 are 30 to 60 seconds at 60 to 80 ° C. for each layer.
In the measurement of the curl value, a resin layer containing an ionizing radiation curable resin may be irradiated with an amount of ionizing radiation necessary to cure the resin layer. When a plurality of layers containing an ionizing radiation curable resin are present, an amount of ionizing radiation necessary for curing is irradiated immediately after each layer is formed (before another layer is formed). If the irradiation dose is usually 50 to 200 mJ / cm ^2, the resin layer containing the ionizing radiation curable resin can be cured.
When calculating the curl value, the curl values of 10 samples are measured, and the average is taken as the curl value.
The one or more resin layers include at least a hard coat layer. Moreover, it is preferable that the one or more resin layers include a primer layer and / or a thermoplastic resin layer described later in addition to the hard coat layer. The primer layer and the thermoplastic resin layer are located between the stretched polyester film and the hard coat layer. Moreover, when it has a primer layer and a thermoplastic resin layer simultaneously, it is preferable to have a primer layer, a thermoplastic resin layer, and a hard-coat layer in this order on a stretched polyester film.

(Hard coat layer)
As described above, the hard coat film of the present invention is not necessarily used on the outermost surface. Accordingly, the performance of the hard coat layer in the present invention is different from that of a normal hard coat layer. Specifically, it is most important to configure the hard coat layer so that the hard coat film has good peel resistance. In addition, it is preferable to configure the hard coat layer so that the rigidity and toughness are good while improving the peel resistance of the hard coat film, and if necessary, the hard coat layer is formed so that the hardness is good It is more preferable to do. Such a hard coat layer can be formed from a hard coat layer forming composition containing the ionizing radiation curable resin A.
The ionizing radiation curable resin A forms a cured product by irradiation with ionizing radiation, and a polymerizable monomer, a polymerizable oligomer, or the like can be used.
The polymerizable monomer tends to improve the hardness and rigidity of the hard coat film. On the other hand, the polymerizable oligomer tends not to impair the peel resistance and toughness of the hard coat film. Therefore, it is preferable to use a polymerizable oligomer from the viewpoint of peel resistance, which is regarded as most important in the hard coat film of the present invention. Furthermore, from the viewpoint of imparting hardness and rigidity, a polymerizable oligomer and a polymerizable monomer are used in combination. It is preferable to do.

Examples of the polymerizable monomer or oligomer include a (meth) acrylate monomer or oligomer having a radically polymerizable unsaturated group in the molecule.
Examples of the polymerizable (meth) acrylate monomer or oligomer include urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, melamine (meth) acrylate, polyfluoroalkyl (meth) acrylate, silicone (meth) acrylate, and the like. The monomer or oligomer of these is mentioned. These polymerizable monomers or oligomers may be used alone or in combination of two or more.

  Among the polymerizable (meth) acrylate monomers or oligomers described above, the polymerizable urethane (meth) acrylate monomer or oligomer imparts hardness and rigidity to the hard coat film, and due to the elasticity of the urethane bond, peel resistance and toughness. Is preferable in that it can be improved.

The polymerizable urethane (meth) acrylate monomer or oligomer can be obtained by, for example, these reactions using (a) a (meth) acrylate monomer containing a hydroxyl group and (b) an isocyanate compound as raw materials.
(A) Examples of the (meth) acrylate monomer having a hydroxyl group include pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 2-hydroxy-3-acryloyloxypropyl (meth) acrylate, and the like. In addition, (a) As a (meth) acrylate monomer containing a hydroxyl group, by using a low-functional (meth) acrylate monomer such as 2-hydroxy-3-acryloyloxypropyl (meth) acrylate, peeling resistance And toughness can be made better. Further, (a) as a (meth) acrylate monomer having a hydroxyl group, it is preferable in that a balance between hardness and rigidity, peel resistance and toughness can be improved by using both polyfunctionality and low functionality. . In that case, it is suitable to use together the polyfunctional (meth) acrylate monomer which has a hydroxyl group, and the low functional (meth) acrylate monomer which has a hydroxyl group in the mass ratio of 8: 2 to 6: 4.
(B) Examples of the isocyanate compound include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and the like.

  In addition to the above (a) and (b), (c) another compound capable of reacting with an isocyanate compound may be used in combination. Examples of the other compound (c) include compounds containing active hydrogen such as carboxylic acid and amine. When an amine is used as the other compound of (c), a urea bond is formed by the reaction of (b) and (c) separately from the urethane bond, and when a carboxylic acid is used as the compound of (c), Carboxylic anhydride is formed by the reaction of (b) and (c). In addition to (a) and (b), the use of another compound (c) is preferred in that a stronger bond can be formed.

  The polymerizable (meth) acrylate monomer or oligomer may be a part of the molecular skeleton, modified with alkylene oxide such as ethylene oxide or propylene oxide, caprolactone, isocyanuric acid, alkyl, cyclic alkyl, aromatic. Those modified with a cyclic skeleton such as bisphenol can also be used. The polymerizable (meth) acrylate monomer and oligomer having a cyclic skeleton can reduce shrinkage when cured with ionizing radiation, and can easily balance the hardness and rigidity of the hard coat film with the resistance to peeling and toughness. It is suitable. As the polymerizable (meth) acrylate monomer and oligomer having a cyclic skeleton, for example, those described in JP-A-2009-203428, JP-A-2008-24724, and JP-A-2007-284650 can be used. .

The number of functional groups of the polymerizable (meth) acrylate monomer or oligomer is not particularly limited. When the polyfunctionality is 3 or more, the hardness and rigidity of the hard coat film can be improved. From the viewpoint of hardness and rigidity, the number of functional groups is preferably 3-8, and more preferably 3-6. On the other hand, when the functional group has a low functionality of 2, the peel resistance and toughness of the hard coat film tend not to be impaired. Therefore, it is preferable to use a low-functional (meth) acrylate from the viewpoint of peel resistance, which is most important in the hard coat film of the present invention, and from the viewpoint of imparting hardness and rigidity, a polyfunctional (meta) ) It is preferable to use acrylate together.
As bifunctional (meth) acrylate monomers, 2-hydroxy-3-acryloyloxypropyl (meth) acrylate, polyethylene glycol di (meth) acrylate, propoxylated ethoxylated bisphenol A di (meth) acrylate, ethoxylated bisphenol A di (Meth) acrylate, 1,6-hexanediol di (meth) acrylate and the like can be mentioned.
A monofunctional (meth) acrylate monomer may be further used for adjusting the hardness and viscosity of the composition. Examples of the monofunctional (meth) acrylate monomer include hydroxyethyl acrylate (HEA), glycidyl methacrylate, methoxypolyethylene glycol (meth) acrylate, isostearyl (meth) acrylate, 2-acryloyloxyethyl succinate, and the like.

The molecular weight of the polymerizable (meth) acrylate monomer is preferably less than 1,000, more preferably 200 to 800, from the viewpoint of improving the hardness of the hard coat film.
The weight average molecular weight of the polymerizable (meth) acrylate oligomer (weight average molecular weight in terms of polystyrene measured by GPC method) is preferably 1,000 to 20,000, and preferably 1,000 to 10,000. More preferably, it is more preferably 1,100 to 3,000.

When the ionizing radiation curable resin A is an ultraviolet curable compound, the hard coat layer forming composition preferably contains additives such as a photopolymerization initiator and a photopolymerization accelerator.
Examples of the photopolymerization initiator include acetophenone, benzophenone, Michler's ketone, benzoin, benzylmethyl ketal, benzoylbenzoate, α-acyloxime ester, thioxanthone and the like.
Further, the photopolymerization accelerator is capable of reducing the polymerization obstacle due to air at the time of curing and increasing the curing speed. For example, p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester, etc. Can be mentioned.

  The content of the ionizing radiation curable resin in the total resin components of the hard coat layer forming composition is preferably 50% by mass or more, and preferably 60% by mass or more from the viewpoint of the hardness and rigidity of the hard coat layer. Is more preferable, and it is still more preferable that it is 70 mass% or more.

  The hard coat layer forming composition may contain a thermoplastic resin A. By containing the thermoplastic resin A, when the hard coat film has a thermoplastic resin layer described later, the adhesion between the layer and the hard coat layer can be improved. Further, when the hard coat layer contains conductive fine particles to be described later, the thermoplastic resin A improves the dispersibility of the conductive fine particles in the hard coat layer forming composition and also causes deformation (curing shrinkage) of the hard coat layer. By suppressing, it is preferable in that the stability with time of the surface resistivity can be improved and the peel resistance can be easily improved.

  It is preferable that the thermoplastic resin A does not have a reactive functional group in the molecule. When there is a reactive functional group in the molecule, the reactive functional group reacts to cause curing shrinkage in the hard coat layer, and physical properties such as surface resistivity change over time or peeling resistance decreases. There is. Reactive groups include functional groups having unsaturated double bonds such as acryloyl groups and vinyl groups, cyclic ether groups such as epoxy rings and oxetane rings, ring-opening polymerizable groups such as lactone rings, and isocyanates that form urethane. Groups and the like. These reactive functional groups may be included as long as they do not cause a change in surface resistivity due to curing shrinkage in the hard coat layer.

  The thermoplastic resin A preferably has a side chain. The thermoplastic resin having a side chain can have excellent aging stability of physical properties such as surface resistivity because the side chain becomes a steric hindrance and other components hardly move in the hard coat layer. . The side chain may have any structure, but preferably does not have the above-described reactive functional group in the molecule.

  The thermoplastic resin A preferably has a glass transition temperature of 80 to 120 ° C., more preferably 90 to 110 ° C., in order to easily exhibit the above-described effects. Further, from the viewpoint of the strength and coating suitability of the hard coat layer, the weight average molecular weight (polystyrene equivalent weight average molecular weight measured by GPC method) of the thermoplastic resin is preferably 20,000 to 200,000. More preferably, it is 100,000.

As the thermoplastic resin A, acrylic resin, cellulose resin, urethane resin, vinyl chloride resin, polyester resin, polyolefin resin, polycarbonate, nylon, polystyrene, ABS resin, and the like can be used. Among these, an acrylic resin that easily exhibits the effects described above is preferable, and among the acrylic resins, polymethyl methacrylate is preferable.
In addition, when a hard coat film has the below-mentioned thermoplastic resin layer, it is preferable that the thermoplastic resin in a hard coat layer shall be the same kind as the thermoplastic resin of a thermoplastic resin layer from an adhesive viewpoint.

  When the hard coat layer forming composition contains the thermoplastic resin A in addition to the ionizing radiation curable resin A, the mass ratio of the ionizing radiation curable resin A and the thermoplastic resin A in the hard coat layer forming composition is From the viewpoint of the balance between the effect of containing the thermoplastic resin A and the hardness and rigidity of the hard coat film, 5: 5 to 9: 1 is preferable, and 6: 4 to 8: 2. More preferably.

The hard coat layer may contain conductive fine particles. By containing conductive fine particles in the hard coat layer, the conductivity of the thermoplastic resin layer and the surface of the hard coat layer can be made conductive when the thermoplastic resin layer described later is imparted with conductivity, and the human body comes into contact. It is possible to release static electricity generated at the time. In addition, when there is no hard coat layer on the thermoplastic resin layer imparted with conductivity, it becomes difficult to achieve stability over time of the surface resistivity due to insufficient strength of the thermoplastic resin layer. By providing a hard coat layer containing conductive fine particles on the applied thermoplastic resin layer, the temporal stability of the surface resistivity can be improved.
Hereinafter, a hard coat film having a hard coat layer containing conductive fine particles on a thermoplastic resin layer imparted with conductivity may be referred to as a “conductive hard coat film”. Further, the thermoplastic resin layer imparted with conductivity may be referred to as “first conductive layer”, and the hard coat layer containing conductive fine particles may be referred to as “second conductive layer”.

By disposing the conductive hard coat film on various display elements, it is possible to prevent the display device from being damaged by static electricity. Examples of the display element include a liquid crystal display element, an EL display element, and a plasma display element. As a failure due to static electricity of the display device, there is a phenomenon that the liquid crystal display element becomes clouded. When a conductive hard coat film is installed on a liquid crystal display element, it is preferable in that white turbidity can be prevented.
Moreover, in a liquid crystal display device with a touch panel, there are many opportunities for a human body to contact. Since the conventional touch panel has a touch panel installed on the liquid crystal display element and the constituent members of the touch panel have conductivity, there is no problem of white turbidity of the liquid crystal display element during operation. However, since the in-cell touch panel that has recently appeared incorporates a touch panel function in the liquid crystal display element, static electricity generated on the liquid crystal display element cannot be released, and there is a problem of cloudiness. Here, it is preferable that the conductive hard coat film is installed on the in-cell touch panel liquid crystal element in order to prevent white turbidity.

  The hard coat layer (second conductive layer) containing conductive fine particles allows the static electricity that has reached the thermoplastic resin layer (first conductive layer) imparted with conductivity to flow further in the thickness direction, thereby enabling grounding to be described later. Have a role to play. Accordingly, the first conductive layer has conductivity in the plane direction (X direction, Y direction) and the thickness direction (z direction), whereas the second conductive layer has conductivity in the thickness direction. The second conductive layer has a role different from that of the first conductive layer in that the conductivity in the plane direction is not necessarily required.

The conductive fine particles are not particularly limited, and for example, coated fine particles in which a conductive coating layer is formed on the surface of the core fine particles are preferably used.
The core fine particles are not particularly limited, and examples thereof include inorganic fine particles such as colloidal silica fine particles and silicon oxide fine particles, fine polymer particles such as fluororesin fine particles, acrylic resin particles, and silicone resin particles, and fine particles such as organic inorganic composite particles. . Further, no particular limitation is imposed on the material constituting the conductive coating layer, Au, Ag, Cu, Al , Fe, Ni, Pd, metals or alloys such as Pt, tin oxide (SnO _2), antimony oxide ( Examples thereof include metal oxides such as Sb ₂ O ₅ ), antimony tin oxide (ATO), indium tin oxide (ITO), aluminum zinc oxide (AZO), fluorinated tin oxide (FTO), and ZnO.
Among such conductive fine particles, gold plated fine particles in which the core particles are coated with gold are preferable from the viewpoint of improving the conduction from the first conductive layer.

  The average particle diameter of the conductive fine particles is preferably equal to or larger than the thickness of the hard coat layer in order to obtain a predetermined surface resistivity. Specifically, the average particle diameter of the conductive fine particles is preferably 0.4 to 2.0 times, more preferably 0.5 to 1.6 times the thickness of the hard coat layer. . By setting it to 0.4 times or more, conduction from the thermoplastic resin layer can be improved, and by setting it to 2.0 times or less, it is possible to prevent the conductive fine particles from falling off the hard coat layer. The average particle diameter of the conductive fine particles is a value obtained by TEM observation and measuring the particle diameters of ten electron conductive conductive agents and averaging the obtained values.

  The content of the conductive fine particles is preferably 0.5 to 2.0 parts by mass, and preferably 0.5 to 1.5 parts by mass with respect to 100 parts by mass of all resin components of the hard coat layer. More preferred. By setting it as 0.5 mass part or more, the conduction | electrical_connection from a thermoplastic resin layer can be made favorable, and the coating property of a hard-coat layer and the fall of hardness can be prevented by setting it as 2.0 mass part or less. . A more preferable upper limit of the content of the conductive fine particles is 1.5 parts by mass.

The surface resistivity of the surface of the hard coat layer (second conductive layer) of the conductive hard coat film effectively prevents defects in the display device such as white turbidity of the liquid crystal screen, while the touch panel is a capacitance type. From the viewpoint of operability, it is preferably 1.0 × 10 ^{8 to} 2.0 × 10 ⁹ Ω / □.
In this case, the surface resistivity on the thermoplastic resin layer (first conductive layer) is preferably 1.0 × 10 ^{8 to} 2.0 × 10 ⁹ Ω / □. When the surface resistivity of the thermoplastic resin layer (first conductive layer) is less than 1.0 × 10 ⁸ Ω / □, the surface resistivity in a state where the hard coat layer (second conductive layer) is laminated is 1 Even if it is 0.0 × 10 ⁸ Ω / □ or more, the operability of the capacitive touch panel tends to be adversely affected. If the surface resistivity of the thermoplastic resin layer exceeds 2.0 × 10 ⁹ Ω / □, the surface resistivity with the hard coat layer laminated is 2.0 × 10 ⁹ Ω / □ or less. It becomes impossible to effectively prevent white turbidity of the liquid crystal screen.

In the present invention, the ratio of [thickness of stretched polyester film] / [thickness of hard coat layer] is set to 0.7 to 4.0. By setting the ratio to 0.7 or more, the curl value can be easily adjusted within the range of the present invention, and the peel resistance can be improved. By setting the ratio to 4.0 or less, the hard coat layer It is possible to prevent insufficient strength due to the fact that the thickness becomes thinner than necessary. In addition, it is preferable that the said ratio is 1.0-2.5, and it is more preferable that it is 1.3-2.0.
The thickness of the hard coat layer is not particularly limited as long as it satisfies the above ratio, but is preferably 2 to 10 μm.

  The pencil hardness of JIS K5600-5-4 (1999) on the surface of the hard coat layer is preferably 2H or more. By setting the pencil hardness to 2H or more, the hardness and rigidity of the hard coat film can be easily improved. The upper limit of the pencil hardness on the surface of the hard coat layer is that the hardness is reduced and the toughness is improved, and another layer on the hard coat layer (for example, an adhesive layer for laminating with a polarizing plate as described later) From the viewpoint of adhesiveness when forming the film), it is preferable to set it to about 3H. Since the touch panel is repeatedly pressed and high adhesion and toughness are required, the hard coat film of the present invention is installed on the touch panel components and the touch panel by setting the upper limit of the pencil hardness of the hard coat layer to 3H. When used as a constituent member of an optical member, a remarkable effect can be exhibited. In addition, when using a hard coat film as a structural member of a touch panel or an optical member installed on a touch panel, it is preferable to use a hard coat film in locations other than the outermost surface of these structural members.

(Thermoplastic resin layer)
The hard coat film of the present invention preferably has a thermoplastic resin layer on the stretched polyester film side from the hard coat layer. The thermoplastic resin layer is in close contact with the hard coat layer, and when the hard coat film has a primer layer to be described later, the thermoplastic resin layer can be in close contact with the primer layer to improve the peel resistance. In addition, as described above, when the thermoplastic resin layer is given conductivity, the first conductive layer is provided with conductivity while synergizing with the second conductive layer while ensuring the strength of the hard coat film. can do.

The thermoplastic resin layer can be formed from a thermoplastic resin layer forming composition containing the thermoplastic resin B.
As the thermoplastic resin B used in the thermoplastic resin layer, the same resins as those exemplified as the thermoplastic resin A contained in the hard coat layer can be used. The preferred embodiment of the thermoplastic resin B is the same as the preferred embodiment of the thermoplastic resin A.
For example, the thermoplastic resin B of the thermoplastic resin layer preferably has no reactive functional group in the molecule, and preferably has a side chain. By not having a reactive functional group in the molecule, the reactive functional group reacts to cause curing shrinkage in the thermoplastic resin layer, so that physical properties such as surface resistivity change over time, Decrease in peelability can be prevented. Further, by having a side chain, the side chain becomes steric hindrance, making it difficult for other components to move in the thermoplastic resin layer, and improving the temporal stability of physical properties such as surface resistivity. it can.

  The content ratio of the thermoplastic resin B in all the resin components of the thermoplastic resin layer forming composition is preferably 50% by mass or more, and 70% by mass or more from the viewpoints of adhesion and physical properties over time. More preferably, it is more preferably 90% by mass or more.

The thermoplastic resin layer forming composition may contain an ionizing radiation curable resin C. By containing the ionizing radiation curable resin C, it is possible to prevent the hardness of the hard coat layer from being lowered due to the thermoplastic resin layer becoming extremely soft. However, when the ionizing radiation curable resin C is contained in the thermoplastic resin layer forming composition, the temporal stability of physical properties such as the peel resistance and surface resistivity of the resin layer tends to be impaired. For this reason, when the ionizing radiation curable resin C is contained in the thermoplastic resin layer forming composition, as the ionizing radiation curable resin, a polyfunctional urethane (meth) acrylate having two or more radically polymerizable unsaturated groups in the molecule. It is preferable to use an oligomer. By using the polyfunctional urethane (meth) acrylate oligomer, it is possible to prevent the hardness of the hard coat layer from being lowered while suppressing deterioration of the surface resistivity over time and the peel resistance.
As the polyfunctional urethane (meth) acrylate oligomer, those exemplified for the ionizing radiation curable resin A can be used.

  When the ionizing radiation curable resin C is included in the thermoplastic resin layer forming composition, the temporal stability of physical properties such as surface resistivity (the surface resistivity changes due to the change in the spacing of the conductive agent due to the reaction of the ionizing radiation curable resin C) From the viewpoint of the balance between the resin layer and the peel resistance of the resin layer, the thermoplastic resin B is preferably 100 parts by mass, and the ionizing radiation curable resin C is preferably 50 parts by mass or less. It is more preferable to use a mass part.

When imparting conductivity to the thermoplastic resin layer to form the first conductive layer, the thermoplastic resin layer forming composition may contain a conductive agent.
Examples of the conductive agent include ion conductive conductive agents such as quaternary ammonium salts and lithium salts, and electronic conductive conductive agents such as metal fine particles, metal oxide fine particles, carbon nanotubes, coating fine particles, and polyethylene dioxythiophene particles. An electron conductive type conductive agent that is not easily affected by humidity is preferably used. Among the electron conductive type conductive agents, metal oxide fine particles are preferable from the viewpoint of long-term storage, heat resistance, moist heat resistance, and light resistance.

The metal constituting the metal fine particle is not particularly limited, and examples thereof include Au, Ag, Cu, Al, Fe, Ni, Pd, and Pt.
The metal oxide constituting the metal oxide fine particles is not particularly limited. For example, tin oxide (SnO ₂ ), antimony oxide (Sb ₂ O ₅ ), antimony tin oxide (ATO), indium tin oxide (ITO) , Aluminum zinc oxide (AZO), fluorinated tin oxide (FTO), ZnO and the like.
The coating fine particles are not particularly limited, and examples thereof include conventionally known fine particles having a configuration in which a conductive coating layer is formed on the surface of core fine particles. The core fine particles are not particularly limited, and examples thereof include inorganic fine particles such as colloidal silica fine particles and silicon oxide fine particles, fine polymer particles such as fluororesin fine particles, acrylic resin particles, and silicone resin particles, and fine particles such as organic inorganic composite particles. . Moreover, it does not specifically limit as a material which comprises a conductive coating layer, For example, the metal mentioned above or these alloys, the metal oxide mentioned above, etc. are mentioned.

  The electron conductive conductive agent preferably has an average particle size of 6 to 40 nm. By setting the thickness to 6 nm or more, the electron-conducting conductive agents can easily come into contact with each other in the first conductive layer. Therefore, the amount of the conductive agent added to impart sufficient conductivity can be suppressed to 40 nm or less. Thereby, it can prevent that transparency and the adhesiveness between other layers are impaired. The more preferable lower limit of the average particle diameter of the electron conduction type conductive agent is 7 nm, and the more preferable upper limit is 20 nm. The average particle diameter of the electron conductive conductive agent is a value obtained by TEM observation and measuring the particle diameter of ten electron conductive conductive agents and averaging the obtained values.

  The electron conduction type conductive agent is preferably chain-like or needle-like. The electron conductive conductive agent having such a shape can reduce the variation in surface resistivity even when the first conductive layer is somewhat deformed (curing shrinkage or expansion / contraction due to temperature and humidity).

The content of the electron conductive conductive agent in the first conductive layer is appropriately adjusted according to the type, shape, size, and the like of the electron conductive conductive agent to be used. For example, for 100 parts by mass of the resin component 100 to 300 parts by mass, more preferably 150 to 250 parts by mass. By setting it as 100 parts by mass or more, the surface resistivity of the first conductive layer can be easily reduced to 2.0 × 10 ⁹ Ω / □ or less, and by setting it to 300 parts by mass or less, the surface resistivity of the first conductive layer can be reduced. It can be easily increased to 1.0 × 10 ⁸ Ω / □ or more.

The thickness of the thermoplastic resin layer is preferably thinner than the thickness of the hard coat layer in order to prevent a decrease in the hardness of the hard coat layer. In addition, from the viewpoint of temporal stability of physical properties such as hardness and surface resistivity of the hard coat layer, the ratio of [hard coat layer thickness] / [thermoplastic resin layer thickness] is 1.5 to 50. Is preferably 4-20, more preferably 5-15, and still more preferably 10-13.
In addition, the thickness of a hard-coat layer and a thermoplastic resin layer is the value which observed and measured the cross section using the electron microscope (for example, SEM, TEM, STEM, etc.).

(Primer layer)
The hard coat film of the present invention preferably has a primer layer on the stretched polyester film side than the hard coat layer. The primer layer is preferably formed in contact with the stretched polyester film.
When providing a primer layer, it is suitable to form from the primer layer forming composition containing the ionizing radiation curable resin B. Usually, as the primer layer, a thermoplastic resin is often used from the viewpoint of adhesion and curling prevention due to shrinkage of the coating film (for example, JP-A-5-186621, JP-A-11-42751, JP-A-Heihei 1993). 11-300918 and JP-A-11-300928). In particular, when the thickness of the substrate is thin as in the present invention, curling is likely to occur. Therefore, the use of a curable resin (especially an ionizing radiation curable resin) tends to be avoided. However, the present inventors have found that it is possible to easily prevent peeling of the resin layer from the polyester film by using an ionizing radiation curable resin. The reason for this is considered to be that when an ionizing radiation curable resin is used for the primer layer, the primer layer has good crosslinkability, and recoatability when another layer is formed on the primer layer can be improved.
Moreover, in this invention, the electroconductivity of an electroconductive hard coat film can be made favorable by forming a primer layer from the primer layer forming composition containing ionizing radiation-curable resin B. This is presumably because the first conductive layer is prevented from being mixed with the primer layer when the primer layer is sufficiently crosslinked by ionizing radiation.

  As the ionizing radiation curable resin B, general-purpose polymerizable monomers and polymerizable oligomers exemplified for the ionizing radiation curable resin A can be used. From the viewpoint of peel resistance, adhesion and strength, it is preferable to use a urethane (meth) acrylate monomer or oligomer and a polyester (meth) acrylate monomer or oligomer in combination as the ionizing radiation curable resin B. It is more preferable to use a (meth) acrylate oligomer and a polyester (meth) acrylate monomer in combination, and it is more preferable to use a polyfunctional urethane (meth) acrylate oligomer and a polyfunctional polyester (meth) acrylate monomer in combination. At that time, the urethane (meth) acrylate monomer or oligomer and the polyester (meth) acrylate monomer or oligomer are preferably in a mass ratio of 1:10 to 10: 1.

As described above, the polyfunctional urethane (meth) acrylate oligomer can be obtained by, for example, these reactions using a (meth) acrylate monomer containing a hydroxyl group and an isocyanate compound as raw materials. The polyfunctional urethane (meth) acrylate oligomer preferably has a weight average molecular weight (polystyrene equivalent weight average molecular weight measured by GPC method) of 1,000 to 20,000, preferably 2,000 to 15,000. Is more preferable.
Examples of the polyfunctional polyester (meth) acrylate monomer include pentaerythritol tri (meth) acrylate and pentaerythritol tetra (meth) acrylate. The molecular weight of the polyfunctional polyester (meth) acrylate monomer is preferably less than 1,000, and more preferably 200 to 800.

  The content of ionizing radiation curable resin B in all resin components of the primer layer forming composition is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 90% by mass or more. Preferably, it is further more preferable that it is 100 mass%.

  The thickness of the primer layer is preferably 0.05 to 0.50 μm from the viewpoint of balance between stress relaxation due to curing shrinkage of the hard coat layer, improvement in adhesion, and thinning of the hard coat film, and 0.20 to 0 μm. More preferably, it is 30 μm. From the above viewpoint, the ratio of [hard coat layer thickness] / [primer layer thickness] is preferably 5 to 50, more preferably 10 to 40, and more preferably 20 to 35. More preferably, it is more preferably 25-30. In addition, the thickness of a hard-coat layer and a primer layer is the value which observed and measured the cross section using the electron microscope (for example, SEM, TEM, STEM, etc.).

<Earth treatment>
The conductive hard coat film is preferably subjected to a ground treatment from the surface of the second conductive layer in order to appropriately prevent problems of the display device.
When the conductive hard coat film is installed on various display elements, it may be used by being bonded to another member (polarizing plate or the like), and in this case, the second conductive layer may not be exposed on the surface. Therefore, it is preferable to perform grounding from the surface of the second conductive layer before installing on the display element.

The grounding process includes a technique of connecting the surface of the second conductive layer to another conductive member. At this time, it is preferable that the surface of the conductive layer and the other conductive member are connected via a conducting wire. Moreover, it is preferable that the conducting wire is fixed to the surface of the second conductive layer with a conductive adhesive material such as silver paste, carbon tape, or metal tape.
The ground treatment may be performed at one place on the surface of the second conductive layer or at a plurality of places. In addition, from the viewpoint of not affecting the optical characteristics, other conductive members are located outside the effective area of the hard coat film (outside the range where the image can be visually recognized), the outer edge of the second conductive layer, and the hard coat film. It is preferable to install outside the system.
The area of the conductive adhesive material on the second conductive layer is preferably 1 mm ² to 1 cm ² . By setting the area to 1 mm ² or more, a plurality of conductive fine particles in the second conductive layer can come into contact with the conductive adhesive material, and grounding can be made more effective, and the area can be set to 1 cm ² or less. By doing so, it is possible to prevent the ground portion from being visually recognized from the outside.

The other conductive member that is connected to or in close contact with the surface of the second conductive layer preferably has a volume resistivity of 1.0 × 10 ⁶ Ωm or less from the viewpoint of more effective grounding. It is more preferably 10 ³ Ωm or less, further preferably 1.0 Ωm or less, and particularly preferably 1.0 × 10 ⁻³ Ωm or less.
Examples of such other conductive members include silicon, carbon, iron, aluminum, copper, gold, silver, and alloys such as nichrome.

(Layer structure of hard coat film)
Examples of the layer configuration of the hard coat film of the present invention include the following (1) to (8). Note that “/” indicates a layer interface.
(1) Stretched polyester film / primer layer / thermoplastic resin layer (non-conductive) / hard coat layer (contains no conductive fine particles)
(2) Stretched polyester film / primer layer / hard coat layer (contains no conductive particles)
(3) Stretched polyester film / thermoplastic resin layer (non-conductive) / hard coat layer (contains no conductive fine particles)
(4) Stretched polyester film / primer layer / thermoplastic resin layer (first conductive layer) / hard coat layer (second conductive layer)
(5) Removable film / adhesive layer / stretched polyester film / primer layer / thermoplastic resin layer (non-conductive) / hard coat layer (contains no conductive particles)
(6) Peelable film / adhesive layer / stretched polyester film / primer layer / hard coat layer (contains no conductive fine particles)
(7) Peelable film / adhesive layer / stretched polyester film / thermoplastic resin layer (non-conductive) / hard coat layer (non-conducting fine particles)
(8) Peelable film / adhesive layer / stretched polyester film / primer layer / thermoplastic resin layer (first conductive layer) / hard coat layer (second conductive layer)

The hard coat film of the present invention is a member for a front plate of various display elements such as a liquid crystal display element, an in-cell touch panel liquid crystal display element, an EL display element, a plasma display element, and other optical members such as a polarizing plate and a retardation plate. It can be used as a constituent member of a touch panel. By using the hard coat film of the present invention as a member for a front plate of a display element, a constituent member of a touch panel, etc., the display element and the touch panel can be thinned while improving the visibility with polarized sunglasses. The resin layer on the material does not peel off. Moreover, the trouble by the static electricity of a display apparatus can be prevented by using an electroconductive hard coat film in that case.
In addition, when using the hard coat film of the present invention as a member for a front plate of various display elements, a constituent member of a touch panel, or the like, it is used by being bonded to another member such as a polarizing plate or a retardation plate from the viewpoint of handleability. It is preferable. For example, when used for a front plate of a liquid crystal display element, it is preferable to bond the hard coat film of the present invention and a polarizing plate together. By laminating the polarizing plate and the hard coat film of the present invention, the hard coat film of the present invention can act as a polarizing plate protective film, and the display device can be further reduced in thickness. The direction when the hard coat film of the present invention is bonded to another member such as a polarizing plate is not particularly limited. However, in the case of a conductive hard coat film, the hard coat film is hardened from the viewpoint of the temporal stability of the conductivity. More preferably, the coating layer side is bonded to another member such as a polarizing plate.

[Display device]
The display device of the present invention has the hard coat film of the present invention on the front surface of the display element.
Examples of the display element include a liquid crystal display element, an in-cell touch panel liquid crystal display element, an EL display element, and a plasma display element.
The in-cell touch panel liquid crystal element is a liquid crystal element in which a liquid crystal is sandwiched between two glass substrates, and a touch panel function such as a resistive film type, a capacitance type, and an optical type is incorporated therein. Examples of the liquid crystal display method of the in-cell touch panel liquid crystal element include an IPS method, a VA method, a multi-domain method, an OCB method, an STN method, and a TSTN method.
In-cell touch panel liquid crystal elements are described in, for example, Japanese Patent Application Laid-Open Nos. 2011-76602 and 2011-222009.

On the display element, for example, each member can be installed in the order of (1) to (3) below. Note that “/” indicates the interface of each member.
(1) Display element / hard coat film / retardation plate / polarizing plate (2) Display element / retardation plate / polarizing plate / hard coat film (3) Display element / retardation plate / hard coat film / polarizing plate In the aspects 1) to (3), it is preferable to install a surface protection plate such as a glass plate or a plastic plate on the outermost surface. The members are preferably bonded with an adhesive or the like.

[Method for improving adhesion of thin hard coat film]
The method for improving the adhesion of a thin hard coat film of the present invention has one or more resin layers including a hard coat layer on a stretched polyester film having a thickness of 4 to 12 μm and an orientation degree of 2.0 or less. When producing a hard coat film, the hard coat layer is formed from a hard coat layer forming composition containing the ionizing radiation curable resin A, and the curl value measured under the following conditions as the one or more resin layers is 14 mm or less. And a ratio of [thickness of stretched polyester film] / [thickness of hard coat layer] is set to 0.7 to 4.0.
[Curl value]
The composition forming each layer constituting the one or more resin layers is coated on a stretched polyester film having a thickness of 25 μm and an orientation degree of 1.5, dried and irradiated with ionizing radiation to form each layer in order, and left for 5 minutes. After the sample is cut out in a 10 cm square, the sample is placed on a horizontal table so that the polyester film side faces the table side. The height at which the four corners of the sample float from the table is measured, and the average value of the four corners is taken as the curl value of the sample.

  According to the method for improving coating film adhesion of a thin hard coat film of the present invention, it is possible to prevent the resin layer from peeling off during the production of the hard coat film or over time.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited at all by these examples. In Examples, “part” and “%” are based on mass unless otherwise specified.

<Measurement of orientation>
The orientation degree of the biaxially stretched polyester films A to C used in Examples and Comparative Examples was measured by the following method using UVIR FTS600 (manufactured by Bio-Rad, FT-IR).
The degree of orientation of the biaxially stretched polyester film was defined by the orientation parameter Y, and the measurement of the orientation parameter Y was performed by infrared absorption spectrum analysis in one reflection of the FTIR-S polarized ATR method.
That is, the measurement surface of the biaxially stretched polyester film is set in a one-time reflection ATR accessory device, the spectrum of one-time reflection is measured, and after the baseline is optimized, the absorption intensity (I ₁₃₄₀ ) at ₁₃₄₀ cm ⁻¹ and 1410 cm ⁻ The absorption intensity at ¹ (I ₁₄₁₀ ) is quantified. Here, the absorption band of 1340 cm ⁻¹ is ωCH ₂ longitudinal vibration, which indicates the presence of the trans isomer, and the intensity quantitatively indicates the concentration of the trans isomer, that is, the state of strong orientation in which the polyester molecules are stretched. Is. The absorption band of 1410 cm ⁻¹ is C = C stretching vibration, and the absorption intensity in in-plane rotation is constant, so that the absorption intensity is normalized as a reference band. The orientation parameter Y is expressed by an equation, and the orientation distribution is measured in the same manner in the range of 0 ° to 170 ° by rotating in-plane every 10 ° starting from the orientation axis direction of the biaxially stretched polyester film. . The direction of the orientation axis of the biaxially stretched polyester film is set on the light source so that the polarizing plate i and the polarizing plate ii are in a crossed Nicol state, and the biaxially stretched polyester is further interposed between the polarizing plates i and ii. A direction parallel to the absorption axis of the polarizing plate ii when the film was installed and the polyester film was rotated to obtain the lowest brightness was defined as the orientation axis direction of the polyester film.
Y = I ₁₃₄₀ / I ₁₄₁₀
The maximum value among the 18 orientation parameters Y thus measured was Y _max , the minimum value was Y _min , and Y _max / Y _min was the degree of orientation of the biaxially stretched polyester film.

<Measurement of curl value>
The curl value was measured for one or more resin layers in each example and comparative example.
Each layer constituting one or more resin layers is formed on a biaxially stretched polyester film having a thickness of 25 μm and an orientation degree of 1.5 under the same conditions as in the examples and comparative examples, and a sample is placed in a 10 cm square after being left for 5 minutes. After cutting, place the sample on a horizontal table so that the polyester film side faces the table. The height at which the four corners of the sample float from the table is measured, and the average value of the four corners is taken as the curl value of the sample. The curl value of 10 samples was measured, and the average was taken as the curl value.

<Removal of coating film>
The degree of peeling from the base material of one or more resin layers of the hard coat films of Examples and Comparative Examples was visually evaluated. If the area of 80% or more of the resin layer is in close contact with the substrate without peeling off, ◎, if the area of 50% or more and less than 80% is in close contact without peeling off, adheres without peeling. Those having an area of less than 50% were evaluated as x.

<Visibility with polarized sunglasses>
The hard coat films of Examples and Comparative Examples are laminated on the liquid crystal element via the adhesive layer (b) having a thickness of 20 μm, and the screen is displayed in white or substantially white, through commercially available polarized sunglasses, or polarized. It was evaluated whether the unevenness of the rainbow pattern could be visually recognized from various angles through the board.
○: Rainbow pattern is not visible ×: Rainbow pattern is visible

<Pencil hardness>
The surface of the hard coat layer is conditioned for 2 hours under conditions of a temperature of 25 ° C. and a relative humidity of 60%, and then specified in JIS K5600-5-4 (1999) using a test pencil specified in JIS S-6006. According to the pencil hardness evaluation method, the pencil hardness of the hard coat layer surface was measured under a load of 4.9 N.

<Surface resistivity>
Based on JIS K6911, the surface resistivity (Ω / □) of the hard coat layer immediately after the production of the hard coat film (excluding the hard coat film of Example 5) was measured. High resistivity meter Hi-Lester UP MCP-HT450 (Mitsubishi Chemical Co., Ltd.) is used, and URS probe MCP-HTP14 (Mitsubishi Chemical Co., Ltd.) is used as the probe, in an environment of temperature 25 ± 4 ° C. and humidity 50 ± 10%. The surface resistivity (Ω / □) was measured at an applied voltage of 500V.
<Stability of surface resistivity over time>
The surface resistivity (Ω / □) of the hard coat layer after holding the hard coat film (excluding the hard coat film of Example 5) at 80 ° C. for 100 hours was measured, and the surface resistance after holding at 80 ° C. for 100 hours was measured. Ratio) / (surface resistivity immediately after manufacture) was calculated. Further, the surface of the hard coat layer was rubbed 10 times (stroke 100 mm) with steel wool (No. 0000) applied with a load of 100 g, and it was visually confirmed whether or not scratch marks were visually recognized on the hard coat layer surface. As a result, the ratio was 0.5 or more and less than 3 and no scratch marks were observed, “◎”, and the ratio was 0.5 or more and less than 3, but scratch marks were observed as “◯”. .

<Biaxially stretched polyester film>
The following biaxially stretched polyester films were prepared.
Biaxially stretched polyester film 1 (thickness 10 μm, orientation degree 1.1, wavelength 589.3 nm phase difference 110 nm)
-Biaxially stretched polyester film 2 (thickness 5 μm, degree of orientation 0.8, phase difference 185 nm with a wavelength of 589.3 nm)
Biaxially stretched polyester film 3 (thickness 38 μm, orientation 2.1, wavelength 589.3 nm retardation 1275 nm)

<Synthesis of urethane acrylate oligomer>
To a flask equipped with a thermometer, a condenser and a stirrer, 10.6 parts of isophorone diisocyanate (manufactured by Daicel Huls, IPDI), 10.0 parts of N-methylpyrrolidone as a solvent, and 20.0 parts of ethyl acetate are added. While maintaining the temperature at 40 ° C. or lower, 1.1 parts of N, N′-dimethylaminopropylamine was dropped from the dropping funnel over 20 minutes. Thereafter, 38.3 parts of pentaerythritol triacrylate (Osaka Organic Chemical Co., Ltd., Biscoat 300) and 0.0001 part of tin octylate as a catalyst were added, the temperature was raised to 80 ° C., the temperature was kept for 2 hours, and the urethanization reaction was continued. Urea-modified urethane acrylate oligomer A1 was obtained (weight average molecular weight 1,300, average number of functional groups 6).

[Example 1]
(1) Formation of primer layer On the biaxially stretched polyester film 1, a primer layer forming composition X having the following formulation was applied by slit reverse coating so that the dry coating thickness was 0.25 μm, and 60 ° C. And dried for 2 minutes and irradiated with ultraviolet rays at an irradiation amount of 150 mJ / cm ² to form a primer layer.
<Primer layer forming composition X>
5 parts of a mixture of polyfunctional urethane acrylate oligomer, pentaerythritol triacrylate, and pentaerythritol tetraacrylate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., UV5501) diluted with 47.5 parts of toluene and 47.5 parts of methyl ethyl ketone.
(2) Formation of thermoplastic resin layer HRAG acrylic (25) MIBK (thermoplastic resin, weight average molecular weight 70,000, glass transition temperature 100 ° C.) manufactured by DNP Fine Chemical Co. is dissolved in propylene glycol monomethyl ether, and further a JGC catalyst V3560 (ATO dispersion, ATO average particle diameter 8 nm) manufactured by Kasei Co., Ltd. was added and stirred, and adjusted so that the final solid content was 8%, and the ratio of thermoplastic resin: ATO was 100: 200 (mass ratio). A composition Y for forming a thermoplastic resin layer was obtained.
On the primer layer, the thermoplastic resin layer-forming composition X is applied by slit reverse coating so that the dry coating thickness is 0.6 μm, dried at 60 ° C. for 2 minutes, and then the thermoplastic resin layer (first Conductive layer) was formed.

(3) Formation of hard coat layer Next, a hard coat layer (second conductive layer) was formed on the thermoplastic resin layer (first conductive layer) by the following method.
(Formation of hard coat layer)
Urethane acrylate oligomer A1 and HRAG acrylic (25) MIBK (thermoplastic resin) manufactured by DNP Fine Chemical Co., methyl ethyl ketone (MEK) / isopropanol (so that the solid content of the two components is 70 parts and 30 parts in order, respectively) IPA) was added to a mixed solvent, stirred and dissolved to obtain a solution a.
Next, 4 parts by mass of a photopolymerization initiator (BASF Japan, Irgacure 184) and leveling agent (10-301 (TL), manufactured by Dainichi Seika Kogyo Co., Ltd.) are 0 with respect to 100 parts of the solid content of the solution a. .2 parts was added and stirred to prepare solution b.
Next, the conductive component dispersion (DNP Fine Chemical Co., Ltd., Bright dispersion, conductive fine particle average particle size 4.6 μm, solid content 25%) is added to 100 parts of the resin component of the solution b, and the active ingredient becomes 0.83 parts. Finally, an ultraviolet absorber (BASF Japan, TINUVI477) was added to 6 parts with respect to 100 parts of the solid content of the solution b and stirred, and the total solid content was 25%. A hard coat layer forming composition Z was obtained.
The hard coat layer-forming composition Z was applied on the thermoplastic resin layer (first conductive layer) previously formed by slit reverse coating so that the coating thickness after drying was 7 μm to form a coating film. After drying the obtained coating film at 70 ° C. for 1 minute, the coating film is cured by irradiating with ultraviolet rays at an ultraviolet irradiation amount of 80 mJ / cm ² to form a 7 μm thick hard coat layer (second conductive layer). A hard coat film was obtained.

[Example 2]
A hard coat film was obtained in the same manner as in Example 1 except that the biaxially stretched polyester film 1 was changed to the biaxially stretched polyester film 2.

[Example 3]
Example 1 except that the urethane acrylate oligomer A1 in the hard coat layer forming composition Z was changed to a polyfunctional polyester acrylate oligomer (manufactured by Toagosei Co., Ltd .: M-9050, weight average molecular weight 418, average number of functional groups 3). Similarly, a hard coat film was obtained.

[Example 4]
A hard coat film was obtained in the same manner as in Example 1 except that the hard coat layer was formed directly on the primer layer using the hard coat layer forming composition having the following formulation without forming the thermoplastic resin layer.
<Hard Coat Layer Forming Composition of Example 4>
The hard coat layer forming composition Z does not contain a conductive fine particle dispersion.

[Example 5]
A hard coat film was obtained in the same manner as in Example 1 except that the thickness of the hard coat layer was changed to 2.5 μm.

[Example 6]
A hard coat film was obtained in the same manner as in Example 1 except that the thickness of the hard coat layer was changed to 10 μm.

[Comparative Example 1]
A hard coat film was obtained in the same manner as in Example 1 except that the biaxially stretched polyester film 1 was changed to the biaxially stretched polyester film 3.

[Comparative Example 2]
A hard coat film was obtained in the same manner as in Example 1 except that the urethane acrylate oligomer A1 in the hard coat layer forming composition Z was changed to pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd .: KAYARAD PET-30). .

[Comparative Example 3]
A hard coat film was obtained in the same manner as in Example 1 except that the urethane acrylate oligomer A1 in the hard coat layer forming composition Z was changed to dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku Co., Ltd .: KAYARAD DPHA). .

[Comparative Example 4]
A hard coat film was obtained in the same manner as in Example 1 except that the primer layer forming composition X was changed to the following, and ultraviolet rays were not irradiated during the formation of the primer layer.
<Primer layer forming composition of Comparative Example 5>
・ Polyester resin (Toyobo, Byron 200) 5 parts ・ Methyl ethyl ketone 66 parts ・ Toluene 33 parts

[Comparative Example 5]
A hard coat film was obtained in the same manner as in Example 1 except that the primer layer forming composition X was changed to the following, and ultraviolet rays were not irradiated during the formation of the primer layer.
<Primer layer forming composition of Comparative Example 5>
・ Polyester resin (Toyobo Co., Ltd., Byron 290) 5 parts ・ Methyl ethyl ketone 66 parts ・ Toluene 33 parts

[Comparative Example 6]
A hard coat film was obtained in the same manner as in Example 1 except that the thickness of the hard coat layer was changed to 1 μm.

[Comparative Example 7]
A hard coat film was obtained in the same manner as in Example 1 except that the thickness of the hard coat layer was changed to 15 μm.

From the results in Table 1, it can be seen that the hard coat films of Examples 1 to 6 can simultaneously satisfy the visibility, thickness reduction, and peeling resistance of the coating film with polarized sunglasses.
Further, by performing grounding from the surface of the hard coat layer (second conductive layer) of the hard coat films of Examples 1 to 3 and 5 to 6, and placing the grounded hard coat film on the display device It was possible to prevent problems such as whitening of the display device due to static electricity.

Claims (15)

A stretched polyester film having a thickness of 4 to 12 μm and an orientation degree of 2.0 or less has one or more resin layers including a hard coat layer, and the hard coat layer includes an ionizing radiation curable resin A. The curl value of the one or more resin layers measured under the following conditions is 14 mm or less, and [thickness of stretched polyester film] / [thickness of hardcoat layer]. A hard coat film having a ratio of 0.7 to 4.0.
(Curl value)
The composition forming each layer constituting the one or more resin layers is coated on a stretched polyester film having a thickness of 25 μm and an orientation degree of 1.5, dried and irradiated with ionizing radiation to form each layer in order, and left for 5 minutes. After the sample is cut out in a 10 cm square, the sample is placed on a horizontal table so that the polyester film side faces the table side. The height at which the four corners of the sample float from the table is measured, and the average value of the four corners is taken as the curl value of the sample.   The one or more resin layers have a primer layer closer to the stretched polyester film than the hard coat layer, and the primer layer is formed from a primer layer forming composition containing an ionizing radiation curable resin B. Item 2. The hard coat film according to Item 1.   The hard coat film according to claim 2, wherein the ionizing radiation curable resin B includes a urethane (meth) acrylate oligomer and a polyester (meth) acrylate monomer.   The hard coat film according to claim 1, wherein the hard coat layer is formed from a hard coat layer forming composition containing an ionizing radiation curable resin A and a thermoplastic resin A.   The hard coat film according to claim 4, wherein the thermoplastic resin A is a thermoplastic resin having no reactive functional group in the molecule.   The hard coat film according to claim 4 or 5, wherein the thermoplastic resin A is polymethyl methacrylate.   The hard coat film according to any one of claims 4 to 6, wherein a mass ratio of the ionizing radiation curable resin A and the thermoplastic resin A in the hard coat layer forming composition is 5: 5 to 9: 1. .   The hard coat film according to claim 1, wherein the one or more resin layers include a thermoplastic resin layer on the stretched polyester film side of the hard coat layer.   The hard coat film according to claim 8, wherein the one or more resin layers include the primer layer, the thermoplastic resin layer, and the hard coat layer in this order from the stretched polyester film side.   The hard coat film according to claim 8 or 9, wherein the thermoplastic resin layer comprises a thermoplastic resin B, and the thermoplastic resin B is a thermoplastic resin having no reactive functional group in the molecule. .   The thermoplastic resin layer contains a conductive agent, the hard coat layer contains conductive fine particles, and the thermoplastic resin layer and the hard coat layer surface are electrically connected to each other. The hard coat film as described.   The hard coat film according to claim 11, which is grounded from the surface of the hard coat layer.   A front plate of a display element, which is formed by bonding a polarizing plate and the hard coat film according to claim 1.   The display apparatus which has the hard coat film in any one of Claims 1-12 in the front surface of a display element. A stretched polyester film having a thickness of 4 to 12 μm and an orientation degree of 2.0 or less has one or more resin layers including a hard coat layer, and the hard coat layer includes an ionizing radiation curable resin A. When producing a hard coat film formed from the hard coat layer forming composition, the one or more resin layers are selected such that the curl value measured under the following conditions is 14 mm or less, and [stretched polyester film The ratio of [thickness] / [hard coat layer thickness] to 0.7 to 4.0 is a method for improving the peel resistance of a thin hard coat film.
[Curl value]
The composition forming each layer constituting the one or more resin layers is coated on a stretched polyester film having a thickness of 25 μm and an orientation degree of 1.5, dried and irradiated with ionizing radiation to form each layer in order, and left for 5 minutes. After the sample is cut out in a 10 cm square, the sample is placed on a horizontal table so that the polyester film side faces the table side. The height at which the four corners of the sample float from the table is measured, and the average value of the four corners is taken as the curl value of the sample.