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 having excellent heat resistance, printing suitability, 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-mentioned optical films because of their high transparency and low cost. In addition, optical films have very excellent flexibility in addition to the above characteristics, and thus are used as flexible circuit boards of components in which 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] Among 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 a curable resin having a three-dimensional crosslinked structure by light irradiation with an amorphous thermoplastic resin having a Tg of 200°C or less or a curable resin prepolymer having a Tg of 200°C or less is formed on the substrate surface to improve the adhesion to 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, in which curling is suppressed by adjusting the total thickness of the functional layer and the thickness of the hard coat layer to an appropriate range. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2014-189596 [Patent Document 2] Japanese Patent Publication No. 2016-108568 [Patent Document 3] Japanese Patent Publication No. 2014-062375 [Patent Document 4] Japanese Patent Publication No. 2011-20406 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, while conventional film substrates or hard coat films disclosed in the above-mentioned Patent Documents 1 to 3 show improvements in adhesion between the conductive layer and the hard coat layer, they have poor thermal shrinkage characteristics (heat resistance) (high thermal shrinkage rate). For example, there was room for improvement regarding damage and deformation of the film due to heat when the conductive layer (printed layer) formed on the hard coat layer was fired.

[0009] Furthermore, while conventional hard coat films, such as those disclosed in Patent Document 4, show improvement in terms of curling, their thermal shrinkage characteristics (heat resistance) are insufficient.

[0010] Therefore, in order to solve the conventional problems, the objectives of the present invention are, firstly, to provide a hard coat film with excellent heat shrinkage properties (heat resistance), and secondly, to provide a hard coat film that, in addition to heat shrinkage properties (heat resistance), maintains high printability while also being excellent in terms of adhesion to the printed layer, optical properties, hardness, and curl suppression. [Means for solving the problem]

[0011] As a result of diligent research to solve the above problems, the inventors have found that a hard coat film with excellent heat shrinkage properties (heat resistance) can be obtained if a predetermined heat shrinkage rate is used. Furthermore, the inventors conducted extensive research and found that by adjusting the surface free energy of the hard coat layer within a predetermined range, when a printed layer (e.g., a conductive layer) is formed on the hard coat layer, excellent adhesion between the printed layer and the hard coat layer is achieved. They also found that by setting the thickness of the hard coat layer to a predetermined thickness, 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, they found that by adjusting the surface hardness of the hard coat layer within a predetermined range, adhesion with the printed layer is improved and curling is reduced.

[0012] This invention was completed as a result of studies based on these various findings. In other words, the present invention is as follows:

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

[0014] (Second invention) The hard coat film is the hard coat film according to the first invention, characterized in that it satisfies 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 taken as P1, and the peak area of 1658 to 1778 cm -1 is taken 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 it 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 it 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 range of 794-823 cm obtained by infrared spectroscopic measurement of the surface of the hard coat layer B is...) -1 Let P3 be the peak area, which is 1658-1778 cm². -1 Let P4 be the peak area.

[0018] (The sixth invention) The hard coat film according to any one of the first to fifth inventions is characterized in that the film substrate is a polyethylene terephthalate film.

[0019] (The seventh invention) A method for manufacturing a hard coat film, wherein a hard coat layer is formed on both sides of a film substrate, and the hard coat film that satisfies the following conditions (I), (II), and (III) is subjected to a heat treatment at 150°C or higher for 30 seconds or more. 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): Film thickness D of the hard coat layer A A However, it is larger than 1 μm. Condition (III): Surface hardness C of the hard coat layer A, represented by the following formula (1) A However, it falls within the range of 3 to 15. Surface hardening degree C A =(P1 / P2)×100...Equation (1) (However, the range of 794-823 cm obtained by infrared spectroscopic measurement of the surface of the hard coat layer A is...) -1 Let P1 be the peak area, which is 1658-1778 cm². -1 Let P2 be the peak area. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a hard coat film with excellent heat shrinkage properties (heat resistance). Furthermore, according to the present invention, in addition to the heat shrinkage characteristics (heat resistance), it is possible to provide a hard coat film that maintains high printability while also exhibiting excellent adhesion to the printed layer, optical properties, hardness, and curl suppression. [Modes for carrying out the invention]

[0021] Embodiments of the present invention will be described in detail below. In this invention, unless otherwise specified, "○○~△△" means "○○ or greater and △△ or less."

[0022] As described above, the present invention is a hard coat film having hard coat layers formed on both sides of a film substrate, 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 described above).

[0023] Furthermore, the present invention is a hard coat film in which the hard coat film satisfies the following conditions (I), (II), and (III) in the first invention described above (the second invention described 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): Film thickness D of the hard coat layer A A However, it is larger than 1 μm. Condition (III): Surface hardness C of the hard coat layer A, represented by the following formula (1) A However, it falls within the range of 3 to 15. Surface hardening degree C A =(P1 / P2)×100...Equation (1) (However, the range of 794-823 cm obtained by infrared spectroscopic measurement of the surface of the hard coat layer A is...) -1 Let P1 be the peak area, which is 1658-1778 cm². -1 Let P2 be the peak area.

[0024] (Film substrate) First, let me explain the film substrate mentioned above. The film substrate used in the present invention is not particularly limited, and examples include triacetylcellulose, 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, polyamide-imide, and mixtures thereof. However, from the viewpoint of heat resistance, availability, and cost-effectiveness, it is preferable to use a thermoplastic resin film composed of polyethylene terephthalate, polyethylene naphthalate, or triacetylcellulose. In particular, polyethylene terephthalate film is preferred because it is highly transparent, inexpensive, and readily available.

[0025] (Hard coat layer) Next, the hard coat layer described above will be explained. The hard coat film of the present invention has hard coat layers formed on both sides of the film substrate. The hard coat layer formed on one side of the film substrate will be called "hard coat layer A," and the hard coat layer formed on the other side will be called "hard coat layer B."

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

[0027] In this invention, "thermal shrinkage rate" is the value obtained by measuring it by the following test method and calculating it from the measurement results using the following formulas (3) and (4).

[0028] [Test Method] In accordance with the Japanese Industrial Standard JIS-K-7133, the hard coat film is cut to a size of 120 mm x 120 mm, and the distance between two markings (L0 and T0) marked on the cut test piece in the longitudinal and transverse directions is measured before testing. In this case, the longitudinal and transverse directions are defined as the direction of film flow during hard coat coating, with the direction perpendicular to it being the transverse direction. Next, the test piece is heated in a hot air drying oven heated to a predetermined temperature (150°C) for a specified time (30 minutes), and then allowed to cool to room temperature for at least 30 minutes. The distances between the markings in the longitudinal and transverse directions (L and T) are measured again, and the changes in the distances between the markings in the longitudinal and transverse directions (ΔL and ΔT) for the test piece are calculated using the following formulas (3) and (4). ΔL=[(L-L0) / L0]×100(%) ···(3) ΔT=[(T-T0) / T0]×100(%) ···(4)

[0029] The change in the vertical distance between the gauge marks (ΔL) is called the thermal shrinkage rate of the film in the vertical direction, and the change in the horizontal distance between the gauge marks (ΔT) is called the thermal shrinkage rate of the film in the horizontal direction.

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

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

[0032] The hard coat film of the present invention exhibits excellent heat shrinkage characteristics (heat resistance) because its thermal shrinkage rate is 0.3% or less when heated at 150°C for 30 minutes. This prevents damage or deformation of the film due to heat during, for example, the firing of a printed layer (e.g., a conductive layer) formed on the hard coat layer. Furthermore, a low thermal shrinkage rate reduces dimensional changes in subsequent processes, facilitating alignment during the manufacturing process and expanding its applications to precision electronic devices (such as printed circuit boards and TFT substrates). On the other hand, if the thermal shrinkage rate exceeds 0.3%, the film cannot be prevented from being damaged or deformed as described above, resulting in poor heat resistance.

[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 side of a film substrate and a hard coat layer B on the other side, but it is preferable that the surface free energy of the hard coat layer A formed on at least one side is adjusted to a predetermined range (specifically, in the range of 30 mN / m to 55 mN / m) (condition (I) above). This hard coat layer A contains an electron beam curable resin, which is a binder resin, and a leveling agent for adjusting the surface free energy within the predetermined range described above.

[0034] In this invention, the above-mentioned surface free energy refers to the excess energy possessed by the surface of hard coat layer A compared to the interior (bulk) of the layer. This surface free energy can be measured by using a contact angle meter (for example, the fully automatic contact angle meter DM-701 manufactured by Kyowa Interface Science Co., Ltd.) and analyzing the contact angle between water and hexadecane using the Kaelble-Uy method.

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

[0036] Examples of fluorine-based leveling agents preferably used in the present invention include commercially available products such as Futergent 681 (trade name, manufactured by Neos Co., Ltd.), Futergent 184 (trade name, manufactured by Neos Co., Ltd.), and Futergent 602A (trade name, manufactured by Neos Co., Ltd.).

[0037] In the present invention, the above-mentioned fluorine-based leveling agent may be used in combination with other types of leveling agents, to the extent that it does not inhibit the desired effect. Examples of other types of leveling agents include acrylic-based leveling agents and silicone-based leveling agents.

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

[0039] Furthermore, the hard coat film of the present invention has a hard coat layer A thickness D A It is preferable that the thickness is 1 μm or more (condition (II) above). Note that the film thickness D referred to here is AThis refers to the film thickness of hard coat layer A after curing.

[0040] Hard coat layer A thickness D A If the thickness is less than 1 μm, it is undesirable because it will result in insufficient heat resistance, making it difficult to suppress deformation of the substrate due to thermal energy or light energy (heat of firing) used to fire conductive materials, for example. On the other hand, the thickness D of the hard coat layer A A If the film thickness becomes too thick, the flexibility required for use as a printing film will be compromised. Therefore, in this invention, the film thickness D A It is preferable that the particle size is 20 μm or less.

[0041] Furthermore, the hard coat film of the present invention has a surface hardness of C of the hard coat layer A. A However, it is preferable that it be in the range of 3 to 15 (condition (III) above). In the present invention, it is particularly preferable that it be in the range of 5 to 15, and more preferably in the range of 6 to 12. Surface hardness C of hard coat layer A A If the hardness level is less than 3, the hard coat layer A has hardened too much, impairing its flexibility when used as a printing film and worsening its adhesion to the printing layer (e.g., conductive layer). On the other hand, the surface hardness level C of the hard coat layer A A If the value exceeds 15, the hard coat layer A will not harden sufficiently, resulting in an inability to obtain the desired hardness of the hard coat layer A, difficulty in obtaining the desired heat resistance required for the hard coat layer A, and a tendency for the hard coat film to deteriorate due to the heat of firing, which is undesirable.

[0042] The surface hardness of such hard coat layer A is C A This can be calculated using the following formula (1). Surface hardening degree C A =(P1 / P2)×100...Equation (1)

[0043] Here, P1 is 794-823 cm², obtained by infrared spectroscopic spectroscopy of the surface of the hard coat layer A. -1This represents the peak area, which is derived from the carbon-carbon double bond of the (meth)acryloyl group. P2 is also obtained by infrared spectroscopy of the surface of the hard coat layer A, and is 1658-1778 cm². -1 This is the peak area, representing the peak of carbon-oxygen stretching vibration originating from the carbonyl group. Therefore, the above surface hardening degree C A This value indicates the degree of hardening of hard coat layer A; for example, a higher value indicates that unreacted (meth)acryloyl groups remain.

[0044] The infrared spectroscopic spectra described above can be measured using an infrared spectrophotometer (for example, the FT-IR Spectrometer Spectrum 100 (manufactured by PerkinElmer Japan)). The horizontal axis of the obtained spectrum is the wavenumber (cm²). -1 ) and on a spectral chart with absorbance on the vertical axis, 794~823 cm⁻¹ -1 , 1658~1778cm -1 A baseline is drawn on each side, and the areas enclosed by this baseline and the spectral curve are defined as P1 and P2, respectively.

[0045] In the hard coat film of the present invention, the surface hardness C of the hard coat layer A A To adjust this to the predetermined range mentioned above, it is possible to control it, for example, by adjusting the cumulative light intensity of ultraviolet or electron beam irradiation during the curing of hard coat layer A. The cumulative light intensity varies depending on the electron beam curable resin used in the binder resin of hard coat layer A and cannot be determined in general terms, but for example, if a polyfunctional (meth)acrylate resin having three or more (meth)acryloyl groups is included, the cumulative light intensity is 150-270 mJ / cm². 2 It is preferable that it be within the range of [specify range].

[0046] The electron beam curable resin used in the hard coat layer A of the present invention preferably contains at least a polyfunctional (meth)acrylate resin having three or more (meth)acryloyl groups in its molecule, in order to stably ensure adhesion between the hard coat layer A and the film substrate, while also obtaining heat resistance to prevent deformation of the substrate due to firing heat generated by thermal energy and light energy when forming the electrical circuit.

[0047] In the present invention, a polyfunctional (meth)acrylate resin having three or more (meth)acryloyl groups in its molecule is preferably used, and refers to an electron beam or UV-curable (meth)acrylate resin having three or more (meth)acryloyl groups in its molecule. The number of (meth)acryloyl groups contained in the molecule is preferably 3 to 6, and more preferably 4 to 6. If there are more than 6 (meth)acryloyl groups in the molecule, for example, when heat treatment is performed to bake the ink of the printing layer in a later process, the unreacted (meth)acryloyl groups may become active again, and the hard coat film may curl. On the other hand, if the number of (meth)acryloyl groups contained in the molecule is less than 3, it may be difficult to obtain the desired heat resistance required for the hard coat layer A, and the hard coat film may be prone to deterioration due to the heat of baking.

[0048] Specific examples of polyfunctional (meth)acrylate resins having three or more (meth)acryloyl groups in the molecule, which are 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 polyfunctional (meth)acrylate resins preferably have a weight-average molecular weight of 600 or more, and more preferably 750 or more. A weight-average molecular weight of less than 600 is undesirable because it causes excessive curling due to curing shrinkage. The upper limit of the weight-average molecular weight is preferably 2000 or less, and more preferably 1500 or less. If the weight-average molecular weight is greater than 2000, it is difficult to obtain the desired heat resistance required for hard coat layer A, and there is a risk that the hard coat film will deteriorate easily due to the heat of firing.

[0050] Furthermore, in the present invention, a polyfunctional (meth)acrylate resin having three or more functions, i.e., three or more (meth)acryloyl groups in the molecule, can be used in combination with other electron beam curable resins to the extent that the desired effect is not inhibited. The other electron beam curable resin used in combination is a transparent resin that polymerizes and hardens by irradiation with an electron beam or ultraviolet light, and 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 consisting of ultraviolet-curable polyfunctional acrylates having two or more (meth)acryloyl groups in the molecule. Specific examples of UV-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, and dipentaerythritol hexa(meth)acrylate, as well as dia(meth)acrylate of bisphenol A diglycidyl ether. Examples include epoxy (meth)acrylates such as acrylate, diacrylate of neopentyl glycol diglycidyl ether, and di(meth)acrylate of 1,6-hexanediol diglycidyl ether; polyester (meth)acrylates that can be obtained by esterifying a polyhydric alcohol with a polyhydric carboxylic acid and / or its anhydride with acrylic acid; urethane (meth)acrylates obtained by reacting a polyhydric alcohol with a polyhydric isocyanate and a hydroxyl group-containing (meth)acrylate; and polysiloxane poly(meth)acrylates.

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

[0052] The coating solution for forming the hard coat layer A contains, in addition to the electron beam-curable resin and leveling agent, a photopolymerization initiator, defoamer, lubricant, ultraviolet absorber, light stabilizer, polymerization inhibitor, wetting dispersant, rheology control agent, antioxidant, antifouling agent, antistatic agent, conductive agent, etc., as needed. The solvent can be appropriately selected from known organic solvents, etc.

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

[0054] Any known coating method can be used to apply the coating liquid for forming the hard coat layer A onto the film substrate. Examples include the reverse coating method, gravure coating method, bar coating method, die coating method, spray coating method, kiss coating method, wire bar coating method, and curtain coating method, and these coating methods may be used individually or in combination.

[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 2.0 nm or less. This is preferable because an arithmetic mean height (Sa) of 2.0 nm or less on the surface of the hard coat layer A allows for the formation of a uniform printed layer (such as a conductive layer) on the hard coat layer A.

[0056] Here, arithmetic mean height (Sa) is defined in ISO 25178 and is a parameter that extends Ra (arithmetic mean roughness of a line: defined in the annex of JIS B 0031 (1994) / JIS B 0061 (1994)) to surfaces. It represents the average of the absolute differences in height of each point relative to the average plane of the surface. Specifically, it can be calculated from the data of the film surface roughness curve measured with a surface roughness meter. Typically, by applying a hard coat coating layer with a thickness of 1 μm or more, it is possible to achieve a Sa of 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 has the hard coat layer A formed on one side of the film substrate and the hard coat layer B formed on the other side.

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

[0059] This hard coat layer B contains at least an electron beam curable resin as a binder resin. There are no particular restrictions on the electron beam curable resin used in the hard coat layer B of the present invention; for example, the same resin as that used in the hard coat layer A described above can be used.

[0060] In addition to the electron beam-curable resin, which is the binder resin, the hard coat layer B may contain a leveling agent to adjust the surface free energy within a predetermined range, similar to the hard coat layer A. In this case, for example, a fluorine-based leveling agent used in hard coat layer A can be used. By adjusting the surface free energy within a predetermined range in hard coat layer B as well, when a printed layer (e.g., a conductive layer) is formed on hard coat layer B, the adhesion between the printed layer and hard coat layer B can be improved.

[0061] In the present invention, the thickness D of the hard coat layer B is B and the film thickness D of the hard coat layer A. A And, |D A -D B It is preferable that it is in the range of |≤3μm, |D A -D B It is even more preferable that the thickness difference between hard coat layer A and hard coat layer B is within the above range, as this cancels out the curling of the hard coat layer due to curing shrinkage. Note that the thickness D referred to here is B This refers to the film thickness of hard coat layer B after curing.

[0062] Furthermore, in the present invention, the surface hardness C of the hard coat layer A A And the surface hardness C of the hard coat layer B, as expressed by the following formula (2) B And, |C A -C B It is preferable that it is in the range of |≦3, and |C A -C B It is more preferable that the value is in the range of |≤1|. Surface hardening degree C B =(P3 / P4)×100...Equation (2)

[0063] Here, P3 is 794-823 cm², obtained by infrared spectroscopic spectroscopy of the surface of the hard coat layer B. -1This represents the peak area, which is derived from the carbon-carbon double bond of the (meth)acryloyl group. P4 is also obtained by infrared spectroscopic spectroscopy of the surface of the hard coat layer B, and is located at 1658-1778 cm². -1 This is the peak area, representing the peak of carbon-oxygen stretching vibration originating from the carbonyl group. Therefore, the above surface hardening degree C B This value indicates the degree of hardening of hard coat layer B; for example, a larger value indicates that unreacted (meth)acryloyl groups remain. The infrared spectroscopic spectrum of hard coat layer B can be measured in the same manner as described above for hard coat layer A.

[0064] It is preferable that the difference in surface hardness between hard coat layer A and hard coat layer B is within the above range, as this allows the stresses of hardening shrinkage generated in hard coat layer A and hard coat layer B to easily counteract each other on both sides of the film substrate, thereby canceling out curl.

[0065] To adjust the surface hardness of hard coat layer B so that the difference in surface hardness between hard coat layer A and hard coat layer B falls within the above range, one method is to adjust the integrated light intensity of ultraviolet or electron beam irradiation during the curing of hard coat layer B. The integrated light intensity will vary depending on the resin and additives used in hard coat layer B and cannot be determined definitively, but for example, it may be ±50 mJ / cm² compared to the integrated light intensity of hard coat layer A. 2 It is preferable that it be within the range of [specify range].

[0066] The coating solution for forming the hard coat layer B may contain, in addition to the electron beam-curable resin, a leveling agent, a photopolymerization initiator, an antifoaming agent, a lubricant, an ultraviolet absorber, a light stabilizer, a polymerization inhibitor, a wetting and dispersing agent, a rheology control agent, an antioxidant, an antifouling agent, an antistatic agent, a conductive agent, and the like, as needed, in the solvent. The solvent may be appropriately selected from known organic solvents and the like.

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

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

[0069] The hard coat layer B formed as described above preferably has an arithmetic mean height (Sa) of 3 nm or more, and preferably 30 nm or less. When the arithmetic mean height (Sa) of the hard coat layer B is 3 nm or more, a hard coat film with excellent blocking resistance during film winding can be obtained. Furthermore, if the arithmetic mean height (Sa) of the hard coat layer B is greater than 30 nm, there is a risk of increased haze in the hard coat film, which is undesirable. As the arithmetic mean height (Sa) has been explained above, a redundant explanation will be omitted.

[0070] One method for adjusting the surface roughness of the hard coat layer B to a predetermined range is to include, for example, inorganic or organic fine particles with an average primary particle size of about 10 nm to 100 nm in the hard coat layer B.

[0071] A hard coat film, formed by creating a hard coat layer on both sides of the film substrate described above, may be subjected to heat treatment (annealing). By appropriately adjusting the heating conditions (temperature, time, etc.) during this heat treatment, it is possible to obtain a hard coat film with excellent heat shrinkage characteristics (heat resistance), such that the heat shrinkage rate when the hard coat film, formed by creating a hard coat layer on both sides of the film substrate, is heated at 150°C for 30 minutes, is 0.3% or less. In this case, suitable heating conditions include, for example, a temperature of 150°C or higher and a time of 30 seconds or more. Furthermore, this heat treatment can be carried out, for example, in a hot air drying oven.

[0072] Furthermore, the present invention also provides a method for manufacturing a hard coat film. Specifically, the method for manufacturing a hard coat film according to the present invention is a method for manufacturing a hard coat film in which a hard coat layer is formed on both sides of a film substrate, 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 more. 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): Film thickness D of the hard coat layer A A However, it is larger than 1 μm. Condition (III): Surface hardness C of the hard coat layer A, represented by the following formula (1) A However, it falls within the range of 3 to 15. Surface hardening degree C A =(P1 / P2)×100...Equation (1) (However, the range of 794-823 cm obtained by infrared spectroscopic measurement of the surface of the hard coat layer A is...) -1 Let P1 be the peak area, which is 1658-1778 cm². -1 Let P2 be the peak area.

[0073] Conditions (I), (II), and (III) above have been described previously, so a redundant explanation will be omitted here. The heat treatment described above has also been described previously.

[0074] By the hard coat film manufacturing method of the present invention described above, a hard coat film can be obtained that has excellent heat shrinkage properties (heat resistance), maintains high printability, and also exhibits excellent adhesion of the printed layer, optical properties, hardness, and curl suppression.

[0075] As described in detail above, according to the present invention, a hard coat film with excellent heat resistance (heat shrinkage characteristics) can be obtained by heating a hard coat film, which has hard coat layers formed on both sides of a film substrate, at 150°C for 30 minutes, to a thermal shrinkage rate of 0.3% or less. Furthermore, according to the present invention, by further satisfying the three conditions (I), (II), and (III) mentioned above, in addition to heat resistance (thermal shrinkage characteristics), a hard coat film can be obtained that maintains high printability while also exhibiting excellent adhesion to the printed layer, optical properties, hardness, and curl suppression. [Examples]

[0076] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0077] (Example 1) A hard coat layer solution A with a solid content of 40% was prepared by mixing 70 / 30 parts by weight of butyl acetate / 1-propanol (NPA), 100 parts by weight of an electron beam curable resin mainly composed of urethane acrylate having 4 (meth)acryloyl groups (product name: EBECRYL5129, manufactured by Daicel Ornex Co., Ltd., weight-average molecular weight 800), 2 parts by weight of a photopolymerization initiator (product name: Omunirad-184, manufactured by BASF Japan Ltd.), and 0.3 parts by weight of a leveling agent (product name: Futergent 184, manufactured by Neos Co., Ltd.). This solution was then applied to one side of a 125 μm thick polyethylene terephthalate (PET) film (product name: A4300, manufactured by Toyobo Co., Ltd.) using a Meyer bar so that the film thickness after drying was 3 μm. Next, this coating layer was dried at 80°C for 1 minute to evaporate the solvent, and then exposed to an integrated light intensity of 250 mJ / cm². 2A hard coat film was obtained by curing it with ultraviolet irradiation to form a hard coat layer A.

[0078] Next, hard coat coating liquid B, having the same composition as hard coat coating liquid A, was applied to the other side of the hard coat film on which the hard coat layer A was formed, using a Meyer bar so that the film thickness after drying would be 3 μm. Then, this coating layer was dried at 80°C for 1 minute to evaporate the solvent, and then exposed to an integrated light intensity of 250 mJ / cm². 2 The hard coat layer B was formed by curing with ultraviolet irradiation.

[0079] Next, the double-sided hard coat film, on which hard coat layer A and hard coat layer B were formed on both sides as described above, was placed in a drying oven (small hot air circulation type drying oven manufactured by Abezel Co., Ltd.) heated to 150°C for annealing treatment. After 30 seconds, it was removed and cooled to room temperature under atmospheric conditions. In this way, a hard coat film of Example 1 was obtained, having hard coat layer A and hard coat layer B on both sides of the PET film, respectively.

[0080] (Example 2) The electron beam curable resin in the hard coat layer coating solution A of Example 1 was replaced with an electron beam curable resin mainly composed of an oligomeric acrylate having three (meth)acryloyl groups (product name: NK Ester A-GL-Y-9E, manufactured by Shin Nakamura Chemical Co., Ltd., weight-average molecular weight 1500), and hard coat layer A was formed by coating it using a Meyer bar so that the film thickness after drying was 4 μm. The hard coat film of Example 2 was prepared in the same manner as in Example 1, except that hard coat layer B was formed in the same manner as in Example 1.

[0081] (Example 3) The hard coat film of Example 3 was prepared in the same manner as in Example 1, except that a double-sided hard coat film, on which hard coat layer A and hard coat layer B were formed on both sides in the same manner as in Example 1, was placed in the above-mentioned drying oven heated to 200°C and removed after 60 seconds.

[0082] (Example 4) The electron beam curable resin in the hard coat layer coating liquid B of Example 1 was replaced with an electron beam curable resin mainly composed of urethane acrylate having three (meth)acryloyl groups (product name: EBECRYL4265, manufactured by Daicel Ornex Co., Ltd., weight-average molecular weight 700), and the hard coat layer B was formed by coating it using a Meyer bar so that the film thickness after drying was 6 μm. The hard coat film of Example 4 was prepared in the same manner as in Example 1, except that the hard coat layer A was formed in the same manner as in Example 1.

[0083] (Example 5) The electron beam curable resin in the hard coat layer coating liquid B of Example 1 was replaced with an electron beam curable resin mainly composed of urethane acrylate having 6 (meth)acryloyl groups (product name: EBECRYL220, manufactured by Daicel Ornex Co., Ltd., weight-average molecular weight 1000), and hard coat layer B was formed by coating it using a Meyer bar so that the film thickness after drying was 4 μm. The hard coat film of Example 5 was prepared in the same manner as in Example 1, except that hard coat layer A was formed in the same manner as in Example 1.

[0084] (Comparative Example 1) A hard coat film of Comparative Example 1 was prepared in the same manner as in Example 1, except that a double-sided hard coat film, on which hard coat layer A and hard coat layer B were formed on both sides in the same manner as in Example 1, was placed in the above-mentioned drying oven heated to 120°C and removed after 10 seconds.

[0085] (Comparative Example 2) A hard coat film of Comparative Example 2 was prepared in the same manner as in Example 1, except that the electron beam curable resin in the hard coat layer coating solution A of Example 1 was replaced with an electron beam curable resin mainly composed of urethane acrylate having two (meth)acryloyl groups (product name: EBECRYL4858, manufactured by Daicel Ornex Co., Ltd., weight-average molecular weight 400), and hard coat layer A was formed by coating it using a Meyer bar so that the film thickness after drying was 7 μm, and hard coat layer B was formed in the same manner as in Example 1.

[0086] <Rating> The hard coat films prepared in the examples and comparative examples as described above were evaluated for each of the following items, and the results are summarized in Table 2. The composition and other details of the hard coat films in 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 (Kyowa Interface Science Co., Ltd., fully automatic contact angle meter DM-701), the contact angle of the hard coat layer surface was measured using pure water and hexadecane. The surface free energy was then calculated by analyzing the contact angle values ​​using the Kaelble-Uy method.

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

[0089] <Surface hardness of the hard coat layer> Surface hardness C of the hard coat layer A of each hard coat film A This was calculated as follows: The infrared spectroscopic spectrum of the surface of the hard coat layer A was measured using an infrared spectrophotometer (FT-IR Spectrometer Spectrum 100 (manufactured by PerkinElmer Japan)). The obtained horizontal axis represents the wavenumber (cm). -1 ) and on a spectral chart with absorbance on the vertical axis, 794~823 cm⁻¹ -1 , 1658~1778cm -1A baseline is drawn on each side, and the areas enclosed by this baseline and the spectral curve are defined as peak area P1 and peak area P2, respectively. The surface hardness C is then calculated using the aforementioned equation (1). A They sought it. Furthermore, the surface hardness C of the hard coat layer B of each hard coat film B Similarly, the infrared spectroscopic spectrum of the surface of hard coat layer B was measured and obtained using the aforementioned equation (2). Furthermore, from the above results, |C A -C B The value of | was calculated.

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

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

[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 Technology Laboratory. Visual evaluation was also performed by placing each hard coat film between a light source (fluorescent lamp) and the line of sight, tilting the film at an appropriate angle so that all of the light from the light source could pass through, and evaluating it according to the following criteria. ○: Transparency is not a problem even through a hard coat film, and it has excellent optical properties. ×: When viewed through a hard coat film, it appears whitish and has inferior optical properties.

[0093] <Adhesion of the printed layer> On the hard coat layer A of each hard coat film obtained in the examples and comparative examples, copper nanoparticle paste (product name: CP-100, manufactured by Harima Chemicals, Inc.) was applied to a thickness of 20 μm and a 5 × 5 cm square using a desktop screen printing machine (product name: DP-320, manufactured by Newlong Precision Industries Co., Ltd.), and a conductive film was obtained by light firing using xenon flash light irradiation (xenon pulsed light irradiation device S-200, manufactured by XENON Corporation) to form a printed layer (conductive layer). The adhesion of the printed layer (conductive layer) of the obtained conductive film was evaluated in accordance with the cross-cut method described in JIS-K5600-5-6. Specifically, a cross-cut peel test jig was used on the printed layer (conductive layer) surface of the obtained conductive film, measuring 1 mm. 2 One hundred cross-cuts were prepared, and adhesive tape No. 252 manufactured by Sekisui Chemical Co., Ltd. was applied to them. After pressing evenly with a spatula, the adhesive tape was peeled off in a 180-degree direction, and the remaining rate of the printed layer (conductive layer) (ratio of the number of remaining cross-cuts) was determined and evaluated according to the following three-stage criteria. A rating of ◎ or ○ indicated good adhesion. ◎: Survival rate 95% or more ○: Survival rate between 75% and less than 95% ×: Survival rate less than 75%

[0094] <Scratch resistance> In accordance with the JIS-K5600-5-10 test method, a 25mm diameter steel wool #0000 (manufactured by Nippon Steel Wool Co., Ltd.) was pressed against the hard coat layer A of each hard coat film with 1 kgf of pressure and moved back and forth 10 times. The scratch condition of the hard coat surface was observed visually from an oblique angle above, using a three-wavelength daylight fluorescent lamp (Panasonic Palook, FL 15EX-N 15W) as the light source. The evaluation criteria were as follows: Products with a ◎ or ○ rating were considered to have passed the scratch resistance test. ◎: No injuries observed. ○: There are some minor scratches, but they do not affect its practical use. △: Minor scratches are visible. ×: The scratches are very noticeable.

[0095] <Heat resistance> On the hard coat layer A of each hard coat film, printed lines with widths of 200 μm, 100 μm, and 50 μm were formed using a desktop screen printing machine (product name: DP-320, manufactured by Newlong Precision Industries Co., Ltd.) with copper nanoparticle paste (product name: CP-100, manufactured by Harima Chemicals Co., Ltd.). After printing, the films were photo-cured according to a standard method using xenon flash light irradiation (xenon pulsed light irradiation device S-200, manufactured by XENON Corporation) (irradiation voltage 3kV, irradiation time 1.2 ms). After photo-curing, each printed line was observed under magnification using a laser microscope (product name: VH-6300, manufactured by Nikon Corporation) to determine whether or not there was film damage. Specifically, this film damage refers to deformation of the entire or partial film, or indentation or blistering in the light-irradiated area. The evaluation criteria are as follows. ○: No film damage ×: Film damage present

[0096] <Printability> On the hard coat layer A of each hard coat film, copper nanoparticle paste (product name: CP-100, manufactured by Harima Chemicals, Inc.) was applied to a thickness of 20 μm and a 5 × 5 cm square using a desktop screen printing machine (product name: DP-320, manufactured by Newlong Precision Industries Co., Ltd.), and the printed layer (conductive layer) was obtained by light firing using xenon flash light irradiation (xenon pulsed light irradiation device S-200, manufactured by XENON Corporation). The area of ​​the resulting printed layer is X cm 2 In this case, the reproducibility of the wiring, calculated using the following formula, was evaluated according to the following two-stage criteria. A score of ○ indicated good printability. Formula: (5×5) / X×100 ○: Within 100% ± 5 ×: 100% ± 5 or more

[0097] <Curl characteristics> Each hard coat film, cut to a size of 10 x 10 cm using a cutter, was placed flat in a SafeVen dryer (product name: N50-S5, manufactured by Satake Chemical Machinery Industry Co., Ltd.) heated to 150°C for 2 hours. After that, the presence or absence of film curling was visually observed. The evaluation criteria are as follows. ○: No warping ×: Warping present

[0098] [Table 1]

[0099] [Table 2]

[0100] The results in Tables 1 and 2 show that the hard coat films according to the embodiments of the present invention all exhibit good heat resistance, as well as good adhesion of the printed layer, optical properties, scratch resistance, printability, and curl characteristics. In other words, the present invention provides a hard coat film with excellent heat resistance (thermal shrinkage characteristics), and in addition to this heat resistance (thermal shrinkage characteristics), it also provides a hard coat film that maintains high printability while also exhibiting excellent adhesion of the printed layer, optical properties, hardness, and curl suppression. Therefore, the hard coat film of the present invention is suitable for applications such as conductive films with printed layers, such as conductive layers.

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

Claims

1. A hard-coated film having hard-coat layers formed on both sides of a film substrate, 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 contains 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; A hard coat film characterized in that when the hard coat film is heat treated at 150° C. for 30 minutes, the heat shrinkage in both the longitudinal direction and the transverse direction is 0.2% or less.

2. The hard-coated film described in Claim 1, characterized in that the hard-coated film is subjected to a heat treatment at 150°C or higher and 200°C or lower for 30 seconds or higher and 60 seconds or lower before the heat treatment when measuring the thermal shrinkage rate.

3. A hard-coated film as described in claim 1 or 2, characterized in that the hard-coated film is subjected to a heat treatment at 150°C for 30 seconds or at 200°C for 60 seconds before the heat treatment when measuring the thermal shrinkage rate.

4. 4. The hard coat film according to claim 1, wherein the hard coat film satisfies 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): Thickness D of the hard coat layer A Ａ However, it is 1 μm or more. Condition (III): The surface hardness C of the hard coat layer A is represented by the following formula (1): Ａ is in the range of 3 to 15. Surface hardening degree C Ａ = (P1 / P2)×100... Equation (1) (However, the wavelength range of 794 to 823 cm obtained by infrared spectroscopy of the surface of the hard coat layer A is －１ The peak area of ​​1658 to 1778 cm －１ The peak area of ​​is designated as P2.)

5. The 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 But, |D Ａ -D Ｂ 5. The hard coat film according to claim 1, wherein the thickness of the hard coat film is in the range of |≦3 μm.

6. Surface hardness C of the hard coat layer A Ａ and the surface hardness C of the hard coat layer B, which is represented by the following formula (2): Ｂ But, |C Ａ -C Ｂ 6. The hard coat film according to claim 1, wherein the range of |≦3. Surface hardening degree C Ｂ = (P3 / P4) × 100... Equation (2) (However, the wavelength range of 794 to 823 cm obtained by infrared spectroscopy of the surface of the hard coat layer B is －１ The peak area of ​​1658 to 1778 cm －１ The peak area of ​​is designated as P4.)