Method for manufacturing a hard coat film

Abstract

To provide a hard coat film excellent in heat shrinkage characteristics (heat resistance), and also excellent in printability, adhesion of a printed layer, optical characteristics, a hard property or curl suppression, in addition to the heat shrinkage characteristics (heat resistance).SOLUTION: In a hard coat film obtained by forming a hard coat layer on both surfaces of a film base material, a thermal shrinkage when the hard coat film is heat-treated at 150°C for 30 minutes is 0.3% or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a hard coat film suitable for applications such as a printing film excellent in heat resistance, printability, hardness, and the like.

Background Art

[0002] Plastic film substrates are widely used as substrates for optical films and the like because of their good transparency and light weight. In particular, polyester films such as polyethylene terephthalate are widely used for the above optical films because of their high transparency and low cost. In addition, since the optical film has very excellent flexibility in addition to the above characteristics, it is used as a flexible circuit board of a component in which a metal wiring is formed on the film.

[0003] However, in order to laminate a conductive material such as silver or copper on a plastic film substrate, it is difficult to obtain adhesion, and the substrate is deformed by thermal energy or light energy for firing the conductive material. Therefore, the film substrates that can be used are very limited.

[0004] Under such circumstances, Patent Document 1 discloses a plastic substrate with a hard coat film having a hard coat film excellent in transparency, anti-blocking property, conductivity, and film-forming property. In addition, Patent Document 2 discloses a hard coat film in which the surface free energy of the film surface is adjusted and the adhesion between the hard coat layer and the printing layer (for example, conductive layer) is excellent.

[0005] In addition, Patent Document 3 discloses a substrate in which a transparent resin layer made of an amorphous thermoplastic resin having a Tg of 200°C or lower or a curable resin prepolymer having a Tg of 200°C or lower and becoming a three-dimensional crosslinked structure by light irradiation is formed on the substrate surface to improve the adhesion to a metal (conductive layer).

[0006] Furthermore, Patent Document 4 discloses a hard coat film having a functional layer on the surface of a polyester film and a hard coat layer on the back surface, wherein the total film thickness of the functional layer and the film thickness of the hard coat layer are adjusted to an appropriate range to suppress curl.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, in the conventional film substrates or hard coat films as disclosed in Patent Documents 1 to 3 above, although improvement in the adhesion (adhesiveness) between the conductive layer and the hard coat layer is observed, the heat shrinkage characteristics (heat resistance) are poor (the heat shrinkage rate is large), and there is room for improvement with respect to damage or deformation of the film due to heat when baking the conductive layer (printing layer) formed on the hard coat layer, for example.

[0009] Also, in the conventional hard coat films as disclosed in Patent Document 4 above, although improvement in curl is observed, the heat shrinkage characteristics (heat resistance) are insufficient.

[0010] Therefore, in order to solve the conventional problems, the object of the present invention is, firstly, to provide a hard coat film having excellent heat shrinkage characteristics (heat resistance), and secondly, to provide a hard coat film that, in addition to heat shrinkage characteristics (heat resistance), maintains high printability and is also excellent in adhesion of the print layer, optical properties, hardness, and curl suppression.

Means for Solving the Problems

[0011] As a result of intensive studies to solve the above problems, the present inventors have found that a hard coat film having excellent heat shrinkage characteristics (heat resistance) can be obtained if the heat shrinkage rate is a predetermined value. Furthermore, as a result of intensive studies, the present inventors have found that by adjusting the surface free energy of the hard coat layer within a predetermined range, when a print layer (for example, a conductive layer) is formed on the hard coat layer, the adhesion between the print layer and the hard coat layer is excellent. Also, by setting the film thickness of the hard coat layer to a predetermined film thickness, it has been found that damage to the film due to heat during firing of, for example, a conductive layer formed on the hard coat layer can be suppressed. In addition, by adjusting the surface curing degree of the hard coat layer within a predetermined range, it has been found that the adhesion to the print layer is improved and curl is reduced.

[0012] The present invention has been completed as a result of studies based on such various findings. That is, the present invention is as follows.

[0013] (First Invention) A hard coat film having hard coat layers formed on both sides of a film substrate, wherein the heat shrinkage rate of the hard coat film when heat-treated at 150°C for 30 minutes is 0.3% or less.

[0014] (Second Invention) The hard coat film according to the first invention, characterized by satisfying the following conditions (I), (II), and (III). Condition (I): The hard coat layer A formed on at least one surface has a surface free energy in the range of 30 mN / m to 55 mN / m. Condition (II): The film thickness D of the hard coat layer A A is 1 μm or more. Condition (III): The surface hardness degree C of the hard coat layer A represented by the following formula (1) A is in the range of 3 to 15. Surface hardness degree C A =(P1 / P2)×100 ··· Formula (1) (However, the peak area of 794 to 823 cm -1 obtained by infrared spectroscopic measurement of the surface of the hard coat layer A is defined as P1, and the peak area of 1658 to 1778 cm -1 is defined as P2.)

[0015] (Third invention) The hard coat layer A has a weight average molecular weight of 600 or more and contains a polyfunctional (meth)acrylate resin having three or more (meth)acryloyl groups in the molecule, and is the hard coat film according to the first or second invention.

[0016] (Fourth invention) The film thickness D of the hard coat layer B formed on the other surface of the hard coat film B and the film thickness D of the hard coat layer A A are in the range of |D A -D B |≦3 μm, and is the hard coat film according to any one of the first to third inventions.

[0017] (Fifth invention) The surface hardness degree C of the hard coat layer A A and the surface hardness degree C represented by the following formula (2) of the hard coat layer B B are in the range of |C A -C B |≦3, and is the hard coat film according to any one of the first to fourth inventions. Surface hardness degree C B=(P3 / P4)×100 ··· Equation (2) (However, the peak area of 794 to 823 cm -1 obtained by infrared spectroscopic measurement of the surface of the hard coat layer B is defined as P3, and the peak area of 1658 to 1778 cm -1 is defined as P4.)

[0018] (Sixth Invention) The hard coat film according to any one of the first to fifth inventions, wherein the film base material is a polyethylene terephthalate film.

[0019] (Seventh Invention) A method for manufacturing a hard coat film having hard coat layers formed on both surfaces of a film base material, characterized in that the hard coat film satisfying the following conditions (I), (II) and (III) is subjected to a heat treatment at 150 ° C or higher for 30 seconds or longer. Condition (I): The hard coat layer A formed on at least one surface has a surface free energy in the range of 30 mN / m to 55 mN / m. Condition (II): The film thickness D A of the hard coat layer A is 1 μm or more. Condition (III): The surface hardness C A of the hard coat layer A represented by the following formula (1) is in the range of 3 to 15. Surface hardness C A =(P1 / P2)×100 ··· Equation (1) (However, the peak area of 794 to 823 cm -1 obtained by infrared spectroscopic measurement of the surface of the hard coat layer A is defined as P1, and the peak area of 1658 to 1778 cm -1 is defined as P2.)

Advantages of the Invention

[0020] According to the present invention, a hard coat film excellent in heat shrinkage characteristics (heat resistance) can be provided. In addition, according to the present invention, in addition to this heat shrinkage property (heat resistance), it is possible to provide a hard coat film that maintains high printability and is excellent in adhesion, optical properties, hardness, and curl suppression of the print layer.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be described in detail. In the present invention, unless otherwise specified, "○○ to △△" means "○○ or more and △△ or less".

[0022] As described above, the present invention is a hard coat film having hard coat layers formed on both surfaces of a film substrate, and is characterized in that the heat shrinkage rate when the hard coat film is heat-treated at 150 ° C. for 30 minutes is 0.3% or less (the first invention above).

[0023] Further, the present invention is a hard coat film characterized in that, in the first invention above, the hard coat film satisfies the following conditions (I), (II), and (III) (the second invention above). Condition (I): The hard coat layer A formed on at least one surface has a surface free energy in the range of 30 mN / m to 55 mN / m. Condition (II): The film thickness D of the hard coat layer A A is 1 μm or more. Condition (III): The surface hardness degree C of the hard coat layer A represented by the following formula (1) A is in the range of 3 to 15. Surface hardness degree C A =(P1 / P2)×100 ··· Formula (1) (However, the peak area in the range of 794 to 823 cm obtained by infrared spectroscopic measurement of the surface of the hard coat layer A is defined as P1, and the peak area in the range of 1658 to 1778 cm is defined as P2.) -1 is defined as P1, and the peak area in the range of 1658 to 1778 cm -1 is defined as P2.)

[0024] (Film substrate) First, the film substrate will be described. The film substrate used in the present invention is not particularly limited, and examples thereof include triacetyl cellulose, polyethylene terephthalate, cycloolefin polymer, polycarbonate, polyethylene naphthalate, polyethylene, polytrimethylene terephthalate, polypropylene, polybutylene terephthalate, polybutylene naphthalate, polystyrene, polymethyl methacrylate, polystyrene glycidyl methacrylate, aromatic polyimide, alicyclic polyimide, polyamideimide, and mixtures thereof. However, from the viewpoints of heat resistance, availability, and economy, it is preferable to use a thermoplastic resin film made of polyethylene terephthalate, polyethylene naphthalate, or triacetyl cellulose as a constituent material. In particular, a polyethylene terephthalate film is suitable because of its high transparency, low cost, and easy availability.

[0025] (Hard coat layer) Next, the hard coat layer will be described. In the hard coat film of the present invention, hard coat layers are formed on both surfaces of the film substrate. The hard coat layer formed on one surface of the film substrate is referred to as "hard coat layer A", and the hard coat layer formed on the other surface is referred to as "hard coat layer B".

[0026] The hard coat film of the present invention has hard coat layers formed on both surfaces of the film substrate. For example, hard coat layer A is formed on one surface of the film substrate, and hard coat layer B is formed on the other surface. The hard coat film is characterized in that its heat shrinkage rate when heat-treated at 150°C for 30 minutes is 0.3% or less.

[0027] In the present invention, the "heat shrinkage rate" is a value measured by the following test method and calculated by the following formulas (3) and (4) from the measurement results.

[0028] [Test method] Using the test method in accordance with Japanese Industrial Standard JIS-K-7133, the above hard coat film is cut into a size of 120 mm × 120 mm, and the distances between the two reference lines (L0 and T0) marked in the longitudinal and transverse directions on the cut test piece before the test are measured. In this case, the longitudinal and transverse directions refer to the flow direction of the film during hard coat coating as the longitudinal direction, and the perpendicular direction to it as the transverse direction. Then, after heating in a hot air drying oven at a predetermined temperature (150 °C) for a specified time (30 minutes), it is conditioned at room temperature for at least 30 minutes, and the distances between the reference lines in the longitudinal and transverse directions (L and T) are measured again. Using the following formulas (3) and (4), the changes in the distances between the reference lines in the longitudinal and transverse directions (ΔL and ΔT) of the above test piece are calculated. ΔL = [(L - L0) / L0] × 100 (%) ···(3) ΔT = [(T - T0) / T0] × 100 (%) ···(4)

[0029] And the change in the distance between the reference lines in the longitudinal direction (ΔL) is called the longitudinal thermal shrinkage rate of the film, and the change in the distance between the reference lines in the transverse direction (ΔT) is called the transverse thermal shrinkage rate of the film.

[0030] In the present invention, when the hard coat film is heat-treated at 150 °C for 30 minutes, the thermal shrinkage rate being 0.3% or less means that both the longitudinal thermal shrinkage rate of the film and the transverse thermal shrinkage rate of the film are 0.3% or less.

[0031] Such a hard coat film with a thermal shrinkage rate of 0.3% or less when heat-treated at 150 °C for 30 minutes can be obtained, for example, by adjusting the heating conditions (temperature, time, etc.) during the heat treatment (annealing treatment) for a hard coat film having hard coat layers formed on both sides of a film substrate. In addition to this, it is also possible to obtain the above hard coat film, for example, by changing the type of the film substrate or by changing the type of the binder resin used in the hard coat layer.

[0032] The hard coat film of the present invention has excellent heat shrinkage characteristics (heat resistance) because the heat shrinkage rate when the hard coat film is heat-treated at 150°C for 30 minutes is 0.3% or less. For example, it can prevent damage and deformation of the film due to heat when firing a printed layer (e.g., a conductive layer) formed on the hard coat layer. Also, when the heat shrinkage rate is small, the dimensional change in the subsequent process becomes small, which has the advantages that alignment in the process becomes easy and the application range also expands to precise electronic devices (such as printed wiring boards and TFT substrates). On the other hand, when the above heat shrinkage rate exceeds 0.3%, the above-mentioned film damage and deformation cannot be prevented, and the heat resistance is inferior.

[0033] <Hard coat layer A> As described above, the hard coat film of the present invention has, for example, a hard coat layer A on one surface of the film substrate and a hard coat layer B on the other surface. However, it is preferable that the hard coat layer A formed on at least one surface has a surface free energy adjusted within a predetermined range (specifically, in the range of 30 mN / m to 55 mN / m) (the above condition (I)). This hard coat layer A contains an electron beam curable resin as a binder resin and a leveling agent for adjusting the surface free energy within the above predetermined range.

[0034] In the present invention, the above surface free energy refers to the energy that the surface of the hard coat layer A has excessively compared to the inside of the layer (bulk). This surface free energy can be measured by analyzing the contact angles with water and hexadecane by the Kaelble-Uy method using a contact angle meter (e.g., a fully automatic contact angle meter DM-701 manufactured by Kyowa Interface Science Co., Ltd.).

[0035] As described above, for the hard coat film of the present invention, it is preferable that the hard coat layer A on at least one surface has a surface free energy in the range of 30 mN / m to 55 mN / m. By adjusting the surface free energy of the hard coat layer A within the above-mentioned predetermined range, when a printing layer (for example, a conductive layer) is formed on the hard coat layer A, the adhesion between the printing layer and the hard coat layer A is excellent. Such a hard coat layer A can adjust the surface free energy of the hard coat layer A within the range of 30 mN / m to 55 mN / m, for example, by containing a fluorine-based leveling agent containing at least a hexafluoropropene oligomer derivative.

[0036] Specific examples of the fluorine-based leveling agent preferably used in the present invention include commercially available F-Tergeant 681 (trade name, manufactured by Neos Co., Ltd.), F-Tergeant 184 (trade name, manufactured by Neos Co., Ltd.), F-Tergeant 602A (trade name, manufactured by Neos Co., Ltd.), and the like.

[0037] In the present invention, within a range that does not inhibit the desired effects, the above-mentioned fluorine-based leveling agent and other types of leveling agents may be used in combination. Examples of other types of leveling agents include acrylic-based leveling agents and silicone-based leveling agents.

[0038] The blending amount of the above-mentioned fluorine-based leveling agent for adjusting the surface free energy of the hard coat layer A in the present invention is preferably in the range of 0.1% by weight to 3.0% by weight based on the electron beam curable resin which is the binder resin of the hard coat layer A. If the blending amount of the leveling agent is less than 0.1% by weight, it is difficult to obtain the effect of adjusting the surface free energy due to the small absolute amount of the leveling agent. If it exceeds 3.0% by weight, the impurities in the coating film increase, which may cause a decrease in hardness.

[0039] Further, for the hard coat film of the present invention, the film thickness D of the hard coat layer A A is preferably 1 μm or more (the above-mentioned condition (II)). Here, the film thickness D AThis refers to the film thickness after curing of the hard coat layer A.

[0040] The film thickness D of the hard coat layer A A If it is less than 1 μm, the heat resistance is insufficient, and for example, it is difficult to suppress deformation of the substrate due to thermal energy or light energy (firing heat) for firing the conductive material, so it is not preferable. On the other hand, when the film thickness D of the hard coat layer A A is too thick, the flexibility when used as a printing film is impaired. Therefore, in the present invention, the film thickness D A is preferably 20 μm or less.

[0041] Further, in the hard coat film of the present invention, the surface hardness degree C of the hard coat layer A A is preferably in the range of 3 to 15 (the above condition (III)). In the present invention, particularly, it is preferably in the range of 5 to 15, and more preferably in the range of 6 to 12. The surface hardness degree C of the hard coat layer A A If it is less than 3, the curing of the hard coat layer A has progressed too much, the flexibility when used as a printing film is impaired, and the adhesion to the printing layer (for example, the conductive layer) deteriorates. On the other hand, when the surface hardness degree C of the hard coat layer A A exceeds 15, the curing of the hard coat layer A is insufficient, so the desired hardness as the hard coat layer A cannot be obtained, and the desired heat resistance required for the hard coat layer A is difficult to obtain, and the hard coat film is likely to deteriorate due to firing heat, which is not preferable.

[0042] Such a surface hardness degree C of the hard coat layer A A can be calculated by the following formula (1). Surface hardness degree C A =(P1 / P2)×100 ··· Formula (1)

[0043] Here, P1 is 794 to 823 cm obtained by infrared spectroscopic measurement of the surface of the above hard coat layer A -1is the peak area and represents the peak derived from the carbon-carbon double bond of the (meth)acryloyl group. Also, P2 is the peak area in the range of 1658 to 1778 cm -1 obtained by infrared spectroscopic measurement of the surface of the above hard coat layer A, and represents the peak of the carbon-oxygen stretching vibration derived from the carbonyl group. Therefore, the above surface hardness C A indicates the degree of progress of the curing of the hard coat layer A. For example, the larger this value, the more unreacted (meth)acryloyl groups remain.

[0044] In addition, the above infrared spectroscopic measurement can be performed using an infrared spectrophotometer (for example, FT-IR Spectrometer Spectrum 100 (manufactured by PerkinElmer Japan)). On the spectrum chart with the obtained horizontal axis as the wave number (cm -1 ) and the vertical axis as the absorbance, a baseline is drawn at 794 to 823 cm -1 , 1658 to 1778 cm -1 respectively, and the areas enclosed by this baseline and the spectrum curve are defined as the above P1 and P2, respectively.

[0045] In the hard coat film of the present invention, in order to adjust the surface hardness C A of the hard coat layer A to the above predetermined range, for example, during the curing of the hard coat layer A, it can be controlled by adjusting the integrated light amount of ultraviolet rays or electron beam irradiation. The integrated light amount varies depending on the electron beam curable resin used for the binder resin of the hard coat layer A and cannot be generally determined. However, for example, when a polyfunctional (meth)acrylate resin having 3 or more (meth)acryloyl groups is included, the integrated light amount is preferably in the range of 150 to 270 mJ / cm 2 .

[0046] As the electron beam curable resin used for the hard coat layer A of the present invention, in order to stably ensure the adhesion between the hard coat layer A and the film substrate and obtain heat resistance to prevent deformation of the substrate due to the baking heat generated by thermal energy or light energy when forming an electric circuit, it is preferable to contain at least a polyfunctional (meth)acrylate resin having three or more (meth)acryloyl groups in the molecule.

[0047] The polyfunctional (meth)acrylate resin having three or more (meth)acryloyl groups in the molecule, which is preferably used in the present invention, refers to a resin composed of an electron beam or ultraviolet curable (meth)acrylate resin having three or more (meth)acryloyl groups in the molecule. The number of (meth)acryloyl groups contained in the molecule is preferably 3 to 6, and more preferably 4 to 6. When more than 6 (meth)acryloyl groups are contained in the molecule, for example, when heat treatment is performed to bake the ink of the printing layer in a subsequent process, the unreacted (meth)acryloyl groups become active again, and there is a possibility that the hard coat film curls. On the other hand, when the number of (meth)acryloyl groups contained in the molecule is less than 3, it is difficult to obtain the desired heat resistance required for the hard coat layer A, and there is a risk that the hard coat film is easily deteriorated by the baking heat.

[0048] Specific examples of the polyfunctional (meth)acrylate resin having three or more (meth)acryloyl groups in the molecule, which is preferably used in the present invention, include polyol poly(meth)acrylates such as neopentyl glycol di(meth)acrylate, 1,6 - hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, pentaerythritol tetra(meth)acrylate, and pentaerythritol tri(meth)acrylate.

[0049] Furthermore, such a polyfunctional (meth)acrylate resin preferably has a weight average molecular weight of 600 or more, more preferably 750 or more. If the weight average molecular weight is less than 600, curling due to curing shrinkage is too strong, which is not preferable. Also, as the upper limit of the weight average molecular weight, 2000 or less is preferable, and 1500 or less is more preferable. If the weight average molecular weight is greater than 2000, it is difficult to obtain the desired heat resistance required for the hard coat layer A, and there is a risk that the hard coat film will be easily deteriorated by the firing heat.

[0050] In the present invention, the above trifunctional or higher functional, that is, polyfunctional (meth)acrylate resin having three or more (meth)acryloyl groups in the molecule can be used in combination with other electron beam curable resins within a range that does not inhibit the desired effects. The other electron beam curable resins to be used in combination are transparent resins that polymerize and cure by irradiating with an electron beam, ultraviolet rays, etc. For example, they can be appropriately selected from oligomers and polymers such as acrylic monomers, urethane acrylate resins, polyester acrylate resins, and epoxy acrylate resins. Preferred monomers include those composed of ultraviolet curable polyfunctional acrylates having two or more (meth)acryloyl groups in the molecule. Specific examples of ultraviolet curable polyfunctional acrylates having two or more (meth)acryloyl groups in the molecule include polyol polyacrylates such as neopentyl glycol di(meth)acrylate, 1,6 - hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy (meth)acrylates such as diacrylate of bisphenol A diglycidyl ether, diacrylate of neopentyl glycol diglycidyl ether, di(meth)acrylate of 1,6 - hexanediol diglycidyl ether, polyester (meth)acrylates that can be obtained by esterifying polyhydric alcohols, polyvalent carboxylic acids and / or their anhydrides with acrylic acid, urethane (meth)acrylates obtained by reacting polyhydric alcohols, polyvalent isocyanates and hydroxyl group - containing (meth)acrylates, polysiloxane poly(meth)acrylates, and the like.

[0051] In the hard coat film of the present invention, when a polyfunctional (meth) acrylate resin having three or more (meth) acryloyl groups in the molecule is used as the electron beam curable resin which is the binder resin of the hard coat layer A, the blending amount of such a polyfunctional (meth) acrylate resin is preferably 25 to 100% by mass, more preferably 50 to 100% by mass, still more preferably 80 to 100% by mass with respect to the total weight of the electron beam curable resin in the hard coat layer A.

[0052] In the coating liquid for forming the hard coat layer A, in addition to the electron beam curable resin and the leveling agent in the solvent, if necessary, a photoinitiator, an antifoaming agent, a lubricant, an ultraviolet absorber, a light stabilizer, a polymerization inhibitor, a wetting dispersant, a rheology control agent, an antioxidant, an antifouling agent, an antistatic agent, a conductive agent, etc. are blended. The above solvent can be appropriately selected from known organic solvents and the like and used.

[0053] The hard coat layer A is formed by applying a coating liquid for forming the hard coat layer A on one side of a film substrate, drying it, and then curing it by ultraviolet or electron beam irradiation treatment. The adjustment of the integrated light amount of ultraviolet rays or electron beams during the curing of the hard coat layer A is as described above.

[0054] To apply the coating liquid for forming the hard coat layer A onto the film substrate, any known coating method can be used. For example, a reverse coat method, a gravure coat method, a bar coat method, a die coat method, a spray coat method, a kiss coat method, a wire bar coat method, a curtain coat method, etc. can be mentioned, and these coating methods can be used alone or in combination of a plurality.

[0055] The hard coat layer A formed on one side of the film substrate as described above preferably has an arithmetic mean height (Sa) of its surface of 2.0 nm or less. It is preferable that the arithmetic mean height (Sa) of the surface of the hard coat layer A is 2.0 nm or less because a uniform printing layer (such as a conductive layer) can be formed on the hard coat layer A.

[0056] Note that the arithmetic mean height (Sa) here is defined in ISO 25178, and it is a parameter obtained by extending Ra (arithmetic mean roughness of the line: defined in the appendix of JIS B 0031 (1994) / JIS B 0061 (1994)) to a surface, which represents the average of the absolute values of the height differences of each point with respect to the average surface of the surface. Specifically, it can be calculated from the data of the film surface roughness curve measured by a surface roughness meter. Generally, by providing the hard coat coating layer with a thickness of 1 μm or more, it is possible to make Sa 2.0 nm or less without being affected by the roughness of the substrate surface.

[0057] <Hard coat layer B> The hard coat film of the present invention forms the above hard coat layer A on one surface of the film substrate, and forms a hard coat layer B on the other surface.

[0058] As described above, polyester films such as polyethylene terephthalate, which are suitable as film substrates, may cause a phenomenon in which oligomers precipitate on the film surface and the substrate whitens in a high-temperature and high-humidity environment. However, by providing the above hard coat layers A and B on both surfaces of the film substrate, precipitation of oligomers can be prevented, and changes in optical properties such as the transmittance and haze of, for example, a conductive film to which the hard coat film of the present invention is applied can be suppressed even in a high-temperature and high-humidity environment.

[0059] This hard coat layer B contains at least an electron beam curable resin as a binder resin. The electron beam curable resin used for the hard coat layer B of the present invention is not particularly limited, and for example, the same resin as the above-described hard coat layer A can be used.

[0060] In the hard coat layer B, in addition to the electron beam curable resin which is a binder resin, a leveling agent for adjusting the surface free energy within a predetermined range can be contained in the same manner as in the hard coat layer A. As the leveling agent in this case, for example, the fluorine-based leveling agent used for the hard coat layer A can be used. By adjusting the surface free energy within a predetermined range also in the hard coat layer B, when a printing layer (for example, a conductive layer) is formed on the hard coat layer B, the adhesion between the printing layer and the hard coat layer B can be improved.

[0061] In the present invention, the film thickness D of the hard coat layer B B and the film thickness D of the hard coat layer A A are preferably in the range of |D A - D B | ≤ 3 μm, and more preferably in the range of |D A - D B | ≤ 1 μm. Since the curl of the hard coat layer due to curing shrinkage is offset by the film thickness difference between the hard coat layer A and the hard coat layer B being within the above range, it is preferable. Here, the film thickness D B refers to the film thickness after curing of the hard coat layer B.

[0062] Further, in the present invention, the surface curing degree C of the hard coat layer A A and the surface curing degree C represented by the following formula (2) of the hard coat layer B B are preferably in the range of |C A - C B | ≤ 3, and more preferably in the range of |C A - C B | ≤ 1. The surface curing degree C B = (P3 / P4) × 100 ··· Formula (2)

[0063] Here, P3 is 794 to 823 cm obtained by infrared spectroscopic measurement of the surface of the hard coat layer B -1is the peak area and represents the peak derived from the carbon-carbon double bond of the (meth)acryloyl group. Also, P4 is the peak area obtained by infrared spectroscopic measurement of the surface of the above hard coat layer B in the range of 1658 to 1778 cm -1 and represents the peak of the carbon-oxygen stretching vibration derived from the carbonyl group. Therefore, the above surface hardness C B indicates the degree of progress of the curing of the hard coat layer B. For example, the larger this value is, the more unreacted (meth)acryloyl groups remain. The infrared spectroscopic measurement of the above hard coat layer B can be performed in the same manner as that of the above hard coat layer A.

[0064] It is preferable that the difference in the surface hardness between the hard coat layer A and the hard coat layer B is within the above range because the stress of curing shrinkage generated in the hard coat layer A and the hard coat layer B is likely to counteract on both sides of the film substrate, and the curl is canceled out.

[0065] As a method for adjusting the surface hardness of the hard coat layer B so that the difference in the surface hardness between the hard coat layer A and the hard coat layer B is within the above range, for example, when curing the hard coat layer B, it can be performed by adjusting the integrated light quantity of ultraviolet rays or electron beam irradiation. The integrated light quantity varies depending on the resin and additives used for the hard coat layer B and cannot be determined unconditionally. For example, compared with the integrated light quantity of the hard coat layer A, it is preferably in the range of ±50 mJ / cm 2 .

[0066] In the coating liquid for forming the above hard coat layer B, in addition to the above electron beam curable resin in a solvent, if necessary, a leveling agent, a photoinitiator, an antifoaming agent, a lubricant, an ultraviolet absorber, a light stabilizer, a polymerization inhibitor, a wetting dispersant, a rheology control agent, an antioxidant, an antifouling agent, an antistatic agent, a conductive agent, etc. are blended. The above solvent can be appropriately selected from known organic solvents and the like and used.

[0067] The above hard coat layer B is formed by applying a coating liquid for forming the hard coat layer B onto the surface of the film substrate opposite to the surface on which the hard coat layer A of the film substrate is formed, drying it, and then curing it by ultraviolet ray or electron beam irradiation treatment. The adjustment of the integrated light quantity of ultraviolet rays or electron beam irradiation during the curing of the hard coat layer B is as described above.

[0068] The method of applying the coating liquid for forming the above hard coat layer B onto the film substrate is not particularly limited, and the same coating method as in the case of the above hard coat layer A can be used.

[0069] The arithmetic mean height (Sa) of the surface of the hard coat layer B formed as described above is preferably 3 nm or more and preferably 30 nm or less. When the arithmetic mean height (Sa) of the surface of the hard coat layer B is 3 nm or more, a hard coat film excellent in blocking resistance during winding of the film can be obtained. Also, when the arithmetic mean height (Sa) of the surface of the hard coat layer B is greater than 30 nm, the haze of the hard coat film may increase, which is not preferable. Since the arithmetic mean height (Sa) is as described above, duplicate explanations are omitted.

[0070] Examples of the method of adjusting the surface roughness of the hard coat layer B to a predetermined range include a method of containing inorganic or organic fine particles having an average primary particle size of about 10 nm to 100 nm in the hard coat layer B.

[0071] It is also possible to perform heat treatment (annealing treatment) on the hard coat film obtained by forming hard coat layers on both sides of the above film substrate. By appropriately adjusting the heating conditions (temperature, time, etc.) during this heat treatment, a hard coat film excellent in heat shrinkage characteristics (heat resistance) with a heat shrinkage rate of 0.3% or less when the hard coat film having hard coat layers formed on both sides of the film substrate is heat-treated at 150 °C for 30 minutes can be obtained. As the heating conditions in this case, for example, it is preferable that the temperature is 150 °C or higher and the time is 30 seconds or longer. Further, this heat treatment can be performed, for example, in a hot air drying furnace.

[0072] The present invention also provides a method for manufacturing a hard coat film. That is, the method for manufacturing a hard coat film of the present invention is a method for manufacturing a hard coat film in which hard coat layers are formed on both sides of a film substrate, and the hard coat film satisfying the following conditions (I), (II), and (III) is subjected to heat treatment at 150 °C or higher and 30 seconds or longer. Condition (I): The hard coat layer A formed on at least one surface has a surface free energy in the range of 30 mN / m to 55 mN / m. Condition (II): The film thickness D of the hard coat layer A A is 1 μm or more. Condition (III): The surface hardness degree C of the hard coat layer A represented by the following formula (1) A is in the range of 3 to 15. Surface hardness degree C A =(P1 / P2)×100 ··· Formula (1) (However, the peak area in the range of 794 to 823 cm -1 obtained by infrared spectroscopic measurement of the surface of the hard coat layer A is defined as P1, and the peak area in the range of 1658 to 1778 cm -1 is defined as P2.)

[0073] Since the above conditions (I), (II), and (III) are as described above, duplicate explanations are omitted here. Also, the above heat treatment is as described above.

[0074] By the method for producing a hard coat film of the present invention described above, a hard coat film excellent in heat shrinkage characteristics (heat resistance), maintaining high printability, and also excellent in adhesion of the print layer, optical characteristics, hardness, and curl suppression can be obtained.

[0075] As described in detail above, according to the present invention, when a hard coat film having hard coat layers formed on both surfaces of a film substrate is heat-treated at 150 ° C. for 30 minutes, the heat shrinkage rate is 0.3% or less, whereby a hard coat film excellent in heat resistance (heat shrinkage characteristics) can be obtained. Further, according to the present invention, when the hard coat film further satisfies the above three conditions (I), (II), and (III), in addition to this heat resistance (heat shrinkage characteristics), while maintaining high printability, a hard coat film excellent in adhesion of the print layer, optical characteristics, hardness, and curl suppression can be obtained.

Examples

[0076] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[0077] (Example 1) A butyl acetate / 1-propanol (NPA) = 70 / 30 parts by weight, an electron beam curable resin (trade name: EBECRYL5129, manufactured by Daicel Ornex Co., Ltd., weight average molecular weight 800) having 4 (meth)acryloyl groups as a main component, 100 parts by weight, a photopolymerization initiator (trade name: Omunirad-184, manufactured by BASF Japan Ltd.) 2 parts by weight, and a leveling agent (trade name: Fujent 184, manufactured by Neos Co., Ltd.) 0.3 parts by weight were mixed to prepare a hard coat layer coating liquid A having a solid content concentration of 40%. It was applied to one surface of a 125 μm-thick polyethylene terephthalate (PET) film (trade name: A4300, manufactured by Toyobo Co., Ltd.) using a Mayer bar so that the film thickness after drying would be 3 μm. Next, this coated layer was dried at 80 ° C. for 1 minute to volatilize the solvent, and then the integrated light amount was 250 mJ / cm 2A hard coat film having a hard coat layer A formed by curing through ultraviolet irradiation treatment was obtained.

[0078] Next, on the other surface of the hard coat film having the hard coat layer A formed thereon, a hard coat layer coating liquid B having the same composition as the hard coat layer coating liquid A was applied using a Mayer bar so that the film thickness after drying would be 3 μm. Then, this coated layer was dried at 80°C for 1 minute to volatilize the solvent, and then cured by ultraviolet irradiation treatment with an integrated light quantity of 250 mJ / cm 2 to form a hard coat layer B.

[0079] Next, the double-sided hard coat film having the hard coat layer A and the hard coat layer B formed on both surfaces as described above was placed in a drying oven heated to 150°C (a small hot air circulation drying oven manufactured by Avezel Co., Ltd.) and left to stand for annealing treatment. After taking it out 30 seconds later, it was cooled to room temperature in the atmosphere. In this way, a hard coat film of Example 1 having a hard coat layer A and a hard coat layer B on both surfaces of the PET film was obtained.

[0080] (Example 2) The electron beam curable resin of the hard coat layer coating liquid A of Example 1 was changed to an electron beam curable resin (trade name: NK Ester A-GL-Y-9E, manufactured by Shin-Nakamura Chemical Co., Ltd., weight average molecular weight 1500) mainly composed of an oligomer-based acrylate having 3 (meth)acryloyl groups. A hard coat layer A was formed by coating using a Mayer bar so that the film thickness after drying would be 4 μm. For the hard coat layer B, a hard coat film of Example 2 was produced in the same manner as in Example 1, except that it was formed in the same manner as in Example 1.

[0081] (Example 3) A double-sided hard coat film having a hard coat layer A and a hard coat layer B formed on both surfaces in the same manner as in Example 1 was placed in the above drying oven heated to 200°C and left to stand. A hard coat film of Example 3 was produced in the same manner as in Example 1, except that it was taken out 60 seconds later.

[0082] (Example 4) The electron beam curable resin of the hard coat layer coating liquid B in Example 1 was changed to an electron beam curable resin (trade name: EBECRYL 4265, manufactured by Daicel Ornex Co., Ltd., weight average molecular weight 700) mainly composed of urethane acrylate having three (meth)acryloyl groups, and using a Meyer bar, it was coated so that the film thickness after drying became 6 μm to form a hard coat layer B. Except that the hard coat layer A was formed in the same manner as in Example 1, a hard coat film of Example 4 was produced in the same manner as in Example 1.

[0083] (Example 5) The electron beam curable resin of the hard coat layer coating liquid B in Example 1 was changed to an electron beam curable resin (trade name: EBECRYL 220, manufactured by Daicel Ornex Co., Ltd., weight average molecular weight 1000) mainly composed of urethane acrylate having six (meth)acryloyl groups, and using a Meyer bar, it was coated so that the film thickness after drying became 4 μm to form a hard coat layer B. Except that the hard coat layer A was formed in the same manner as in Example 1, a hard coat film of Example 5 was produced in the same manner as in Example 1.

[0084] (Comparative Example 1) A double-sided hard coat film having a hard coat layer A and a hard coat layer B formed on both sides in the same manner as in Example 1 was placed in the above drying furnace heated to 120°C and allowed to stand, and taken out after 10 seconds. Except for this, a hard coat film of Comparative Example 1 was produced in the same manner as in Example 1.

[0085] (Comparative Example 2) The electron beam curable resin of the hard coat layer coating liquid A in Example 1 was changed to an electron beam curable resin (trade name: EBECRYL 4858, manufactured by Daicel Ornex Co., Ltd., weight average molecular weight 400) mainly composed of urethane acrylate having two (meth)acryloyl groups, and using a Meyer bar, it was coated so that the film thickness after drying became 7 μm to form a hard coat layer A. Except that the hard coat layer B was formed in the same manner as in Example 1, a hard coat film of Comparative Example 2 was produced in the same manner as in Example 1.

[0086] <Evaluation> For each of the hard coat films of the examples and comparative examples prepared as described above, evaluations were made for the following items, and the results are summarized in Table 2. Also, the configurations and the like of the hard coat films of the examples and comparative examples are summarized in Table 1.

[0087] <Surface free energy> The surface free energy of the hard coat layer A of each hard coat film was measured as follows. Using a contact angle meter (fully automatic contact angle meter DM-701 manufactured by Kyowa Interface Science Co., Ltd.), the contact angles of the surface of the hard coat layer were measured using pure water and hexadecane, and the surface free energy was calculated by analyzing using the Kaelble-Uy method from the values of the contact angles.

[0088] <Film thickness of the hard coat layer> The film thickness D of the hard coat layer A of each hard coat film A and the film thickness D of the hard coat layer B B were measured by a film thickness measurement system F20 (manufactured by Filmetrics Co., Ltd.). Also, from the results, the value of |D A - D B | was calculated. Note that the film thickness after coating and drying the coating liquid was the same as the film thickness after curing by ultraviolet irradiation.

[0089] <Surface curing degree of the hard coat layer> The surface curing degree C of the hard coat layer A of each hard coat film A was determined as follows. Using an infrared spectrophotometer (FT-IR Spectrometer Spectrum 100 (manufactured by PerkinElmer Japan)), infrared spectral measurement of the surface of the hard coat layer A was performed. On the spectrum chart with the obtained horizontal axis as the wave number (cm -1 ), and the vertical axis as the absorbance, in the range of 794 - 823 cm -1 , 1658 - 1778 cm -1A baseline was drawn for each, and the areas enclosed by this baseline and the spectral curves were defined as peak area P1 and peak area P2, respectively. The surface hardness C was determined by the above formula (1). A was obtained. Also, for the surface hardness C of the hard coat layer B of each hard coat film B infrared spectroscopic measurement of the surface of the hard coat layer B was performed in the same manner as above, and it was determined by the above formula (2). Also, from the above results, the value of |C A - C B | was calculated.

[0090] <Thermal shrinkage rate> The longitudinal and transverse thermal shrinkage rates of each hard coat film were determined by the above test method. "TD" in Table 2 represents the longitudinal thermal shrinkage rate, and "MD" represents the transverse thermal shrinkage rate, respectively.

[0091] <Surface flatness> Using a three-dimensional surface roughness meter "VertScan2.0" manufactured by Rhodia Systems Co., Ltd., the roughness curve of the film surface was measured, and the arithmetic mean height (Sa) of the surface of the hard coat layer A was determined from the data of this film surface roughness curve.

[0092] <Optical properties> The total light transmittance and haze value (ΔHaze) of each hard coat film were measured using a haze meter "HM150" manufactured by Murakami Color Research Laboratory. Also, for the visual evaluation, each hard coat film was placed between a light source (fluorescent lamp) and the line of sight, and the hard coat film was tilted at an appropriate angle so that all the light from the light source could be transmitted, and the evaluation was performed according to the following criteria. 〇: Even through the hard coat film, there is no problem with permeability, and the optical properties are excellent. ×: When viewed through the hard coat film, it appears whitish, and the optical properties are inferior.

[0093] <Adhesion of the printing layer> On the hard coat layer A of each hard coat film obtained in the examples and comparative examples, a copper nanoparticle paste (product name: CP-100, manufactured by Harima Chemicals, Inc.) was applied in a thickness of 20 μm and a 5×5 cm square using a desktop screen printing machine (product name: DP-320, manufactured by Neuron Precision Industry Co., Ltd.), and then photo-fired by xenon flash light irradiation (xenon pulsed light irradiation device S-200, manufactured by XENON Corporation) to form a printed layer (conductive layer), thereby obtaining a conductive film. The adhesion evaluation of the printed layer (conductive layer) of the obtained conductive film was carried out in accordance with the cross-cut method described in JIS-K5600-5-6. Specifically, on the surface of the printed layer (conductive layer) of the obtained conductive film, using a checkerboard peeling test jig, 100 cross-cuts of 1 mm 2 were made. An adhesive tape No. 252 manufactured by Sekisui Chemical Co., Ltd. was pasted thereon, and after uniformly pressing it using a spatula, the adhesive tape was peeled off in the 180-degree direction, and the residual rate of the printed layer (conductive layer) (the ratio of the remaining number of cross-cuts) was determined and evaluated according to the following three-level criteria. If the evaluation was ◎ or ○, it was judged that the adhesion was good. ◎: Residual rate of 95% or more 〇: Residual rate of 75% or more and less than 95% ×: Residual rate less than 75%

[0094] <Scratch resistance> According to the test method in accordance with JIS-K5600-5-10, when a steel wool #0000 (manufactured by Nippon Steel Wool Co., Ltd.) with a diameter of 25 mm was pressed against the surface of the hard coat layer A of each hard coat film at 1 kgf and reciprocated 10 times, the scratched state of the hard coat surface was visually observed for the reflected light from an oblique upper direction using a three-wavelength daylight white fluorescent lamp (Panasonic Park, F.L 15EX-N 15W) as the light source. The evaluation criteria are as follows. Products evaluated as ◎ or ○ were considered to pass the scratch resistance test. ◎: No scratches are visible. ○: Some scratches are visible, but at a level that does not cause practical problems. △: Fine scratches are visible. ×: The scratches are very prominent.

[0095] <Heat resistance> On the hard coat layer A of each hard coat film, using a copper nanoparticle paste (product name: CP-100, manufactured by Harima Chemicals, Inc.), printing lines with line widths of 200 μm, 100 μm, and 50 μm were formed with a desktop screen printing machine (product name: DP-320, manufactured by Newlong Precision Industry Co., Ltd.). After printing, light baking was performed according to a conventional method by xenon flash light irradiation (xenon pulsed light irradiation device S-200, manufactured by XENON Corporation) (irradiation voltage 3 kV, irradiation time 1.2 ms). Each printed line after light baking was magnified and observed with a laser microscope (product name: VH-6300, manufactured by Nikon Corporation) to determine the presence or absence of film damage. Specifically, this film damage refers to the overall or partial deformation of the film, or the occurrence of depressions or bulges in the light irradiation part. The evaluation criteria are as follows. ○: No film damage ×: Film damage

[0096] <Printing suitability> On the hard coat layer A of each hard coat film, using a desktop screen printing machine (product name: DP-320, manufactured by Newlong Precision Industry Co., Ltd.), a copper nanoparticle paste (product name: CP-100, manufactured by Harima Chemicals, Inc.) was applied with a film thickness of 20 μm and a 5×5 cm square, and light baking was performed by xenon flash light irradiation (xenon pulsed light irradiation device S-200, manufactured by XENON Corporation) to obtain a conductive film of a printed layer (conductive layer). When the area of the obtained printed layer was X cm 2 The reproducibility of the wiring, obtained by the following formula, was evaluated according to the following two-level criteria. If it was an ○ evaluation, it was judged that the printing suitability was good. Formula: (5×5) / X×100 〇: Within 100%±5 ×: 100%±5 or more

[0097] <Curling property> Each hard coat film cut into a 10×10 cm square with a cutter was placed flat in a Safe Bender dryer (product name: N50-S5, manufactured by Satake Chemical Machinery Co., Ltd.) heated to 150°C for 2 hours, and then the presence or absence of film warping was visually observed. The evaluation criteria are as follows. ○: No warping ×: Warping

[0098]

Table 1

[0099]

Table 2

[0100] From the results of Table 1 and Table 2, it can be seen that the hard coat films according to the examples of the present invention all have good heat resistance, and moreover, the adhesion, optical properties, scratch resistance, printability, and curl characteristics of the printing layer are good. That is, according to the present invention, a hard coat film excellent in heat resistance (heat shrinkage characteristics) can be provided, and in addition to this heat resistance (heat shrinkage characteristics), a hard coat film excellent in adhesion, optical properties, hardness, and curl suppression of the printing layer while maintaining high printability can also be provided. Therefore, the hard coat film of the present invention is suitable for applications such as conductive films formed with a printing layer such as a conductive layer.

[0101] On the other hand, the hard coat films of Comparative Examples 1 and 2 with a heat shrinkage rate greater than 0.3% cannot obtain the required heat resistance. That is, in comparative examples that do not meet the requirements of the hard coat film of the present invention, it is difficult to obtain a hard coat film excellent in heat resistance (heat shrinkage characteristics).

Claims

1. A method for manufacturing a hard coat film having hard coat layers formed on both sides of a film substrate, wherein the film substrate is a polyethylene terephthalate film, the hard coat layer A formed on at least one surface of the film substrate contains an electron beam curable resin, and the electron beam curable resin is a polyfunctional (meth)acrylate resin having a weight average molecular weight of 600 or more and having three or more (meth)acryloyl groups in the molecule, the hard coat film is heat-treated at 150°C or higher and 200°C or lower for 30 seconds or more and 60 seconds or less without applying tension, and the hard coat film after the heat treatment satisfies the following conditions (I), (II) and (III), A method for manufacturing a hard coat film, characterized in that when the hard coat film after the heat treatment is heat-treated at 150°C for 30 minutes, the longitudinal thermal shrinkage rate and the transverse thermal shrinkage rate are both 0.2% or less. Condition (I): The hard coat layer A formed on at least one surface has a surface free energy in the range of 30 mN / m to 55 mN / m. Condition (II): The film thickness D of the hard coat layer A Ａ is 1 μm or more. Condition (III): The surface hardness degree C of the hard coat layer A represented by the following formula (1) Ａ is in the range of 3 to 15. Surface hardness C Ａ = (P1 / P2) × 100... Equation (1) (However, the peak area of 794 to 823 cm obtained by infrared spectroscopic measurement of the surface of the hard coat layer A is defined as P1, and the peak area of 1658 to 1778 cm is defined as P2.) －１ is defined as P1, and the peak area of 1658 to 1778 cm －１ is defined as P2.)

2. The method for manufacturing a hard coat film according to claim 1, wherein the heat treatment of the hard coat film is performed at 150°C for 30 seconds or at 200°C for 60 seconds.

Images