Hard coating film

Abstract

[Problem] To provide a hard coating film in which the occurrence of cracks or the like during construction is suppressed while excellent scratch resistance is exhibited. [Solution] A hard coating film comprising a base material and a hard coating layer disposed on one main surface of the base material. In a mandrel bend test carried out in accordance with JIS K 5600-5-1 by using a cylindrical mandrel bend tester and bringing a base material-side surface of the hard coating film into contact with a mandrel, when the diameter of the mandrel at which cracks occur in the hard coating layer is defined as D μm, and the total thickness of the hard coating film is defined as α μm, D / α is 130 or less.

Description

Hard coat film

[0001] This invention relates to a hard coat film.

[0002] Hard coat films are used to protect an object from scratches, cracks, and other damage by being applied to the object. A hard coat film typically consists of a resin film as a base material and a hard coat layer that is superior to the resin film in terms of hardness, scratch resistance, and weather resistance. The hard coat layer is mainly formed using a composition containing components that exhibit hard coat properties.

[0003] Examples of applications for such hard coat films include window films applied to windows of moving objects such as automobiles and buildings, and optical films used to protect the screens of display devices such as displays. For example, window films applied to the outside (exterior side) of windows are required to have high hardness and excellent scratch resistance and weather resistance in order to protect the windows.

[0004] Patent Document 1 discloses a hard coat film in which a silicone-based hard coat layer is provided on one surface of a multilayer substrate made by laminating multiple resin films. Patent Document 1 also states that this hard coat film has excellent impact resistance and weather resistance, and is particularly suitable for application to the outer surface of windows.

[0005] Japanese Patent Publication No. 2002-36441

[0006] Hard coat films are stored in rolled form before installation, and may be subjected to bending and other forces during installation. However, as mentioned above, hard coat films are required to be highly rigid. Therefore, hard coat films lack flexibility, and when forces from installation work or other processes act on them, there is a problem that cracks, breaks, etc. occur in the hard parts of the hard coat film, i.e., the hard coat layer.

[0007] This invention has been made in view of the above circumstances, and aims to provide a hard coat film that exhibits excellent scratch resistance while suppressing the occurrence of cracks and other damage during application.

[0008] The embodiments of the present invention are as follows.

[0009] [1] A hard coat film having a base material and a hard coat layer disposed on one main surface of the base material, wherein in a mandrel bending test performed in accordance with JIS K 5600-5-1 using a cylindrical mandrel bending tester, with the base material side of the hard coat film in contact with the mandrel, the diameter of the mandrel at which a crack occurs in the hard coat layer is D μm, and the total thickness of the hard coat film is α μm, and D / α is 130 or less.

[0010] [2] The hard coat film according to [1], wherein when the thickness of the hard coat layer is B μm, 100 B / α is greater than 0% and 8% or less.

[0011] [3] The hard coat film according to [1] or [2], wherein the infrared shielding rate of the hard coat film is 10% or more.

[0012] [4] The hard coat film described in [3], wherein the infrared shielding rate of the hard coat film is 50% or more.

[0013] [5] A hard coat film according to any one of [1] to [4], wherein the shielding coefficient of the hard coat film is 0.99 or less.

[0014] [6] The hard coat film described in [5], wherein the shielding coefficient of the hard coat film is 0.90 or less.

[0015] [7] The hard coat film is a window film as described in any of [1] to [6].

[0016] [8] The window film is the hard coat film described in [7], which is a window film that is applied to the outside of a window.

[0017] [9] The hard coat film is a film used in the field of optics, as described in any of [1] to [6].

[0018] According to the present invention, it is possible to provide a hard coat film that exhibits excellent scratch resistance while suppressing the occurrence of cracks and other damage during application.

[0019] Figure 1A is a schematic cross-sectional view showing an example of the configuration of the hard coat film according to this embodiment. Figure 1B is a schematic cross-sectional view showing an example of the configuration of the hard coat film according to this embodiment. Figure 2A is a schematic cross-sectional view showing another example of the configuration of the hard coat film according to this embodiment. Figure 2B is a schematic cross-sectional view showing another example of the configuration of the hard coat film according to this embodiment.

[0020] The present invention will now be described in detail based on specific embodiments.

[0021] (1. Hard Coat Film) A hard coat film comprises, for example, a substrate made of a resin film and a hard coat layer that is harder than the substrate.

[0022] Hard coat film is stored in a roll before application, and during application, it is unwound from the roll and subjected to bending and other forces when applied to the substrate. However, the hard coat layer of hard coat film is highly rigid and lacks flexibility. Therefore, for example, if the hard coat film is bent during application, the hard coat layer cannot conform to the substrate, leading to problems such as cracks and breaks in the hard coat layer.

[0023] Therefore, it was difficult to achieve both the full potential of properties resulting from high hardness (such as scratch resistance and weather resistance) and the suppression of cracks and fractures in the hard coat layer.

[0024] In this embodiment, as described below, the ease with which cracks occur in the hard coat layer and the total thickness of the hard coat film are controlled to control the conformability of the hard coat layer to the substrate, thereby controlling the occurrence of cracks in the hard coat layer. As a result, it is possible to suppress the occurrence of cracks in the hard coat layer due to bending, etc., while maintaining the high hardness of the hard coat layer.

[0025] The hard coat film according to this embodiment is suitably used in applications where scratch resistance, weather resistance, etc., are required. The hard coat film according to this embodiment is preferably used as a window film. When used as a window film, examples of the adherend include windows of mobile vehicles such as automobiles, windows of buildings, etc. The window to which the hard coat film according to this embodiment is attached may be made of glass material or glass substitute material such as plastic. Furthermore, the window film may be a film attached to the outside of the window (the side to which direct sunlight enters) or a film attached to the inside of the window. That is, in the case of a mobile vehicle such as an automobile, it may be the window surface on the outside of the vehicle or the window surface on the inside of the vehicle, and in the case of a building, it may be the window surface on the outside or the window surface on the inside. In this embodiment, it is preferable that the film be attached to the outside of the window.

[0026] Window films can be applied, for example, by a method known as wet application. Specifically, wet application involves applying an aqueous medium to at least one of the film contact surfaces, bringing the adhesive layer surface into contact with the substrate, and removing the aqueous medium as necessary. The aqueous medium is used as a so-called application liquid. An aqueous medium refers to a liquid containing 50% by mass or more (up to 100% by mass) of water, preferably 70% by mass or more, more preferably 85% by mass or more, and most preferably water as the aqueous medium. In addition, the application liquid for wet application usually contains a surfactant to improve the slipperiness between the substrate and the film.

[0027] Next, the adhesive layer surface is brought into contact with the substrate. That is, the adhesive layer surface of the film is aligned with the substrate. At this point, the release liner is removed. The window film's installation position can be adjusted by sliding the film against the substrate using a water-based medium (application liquid). After that, the water-based medium is removed and the window film is applied to the substrate.

[0028] One method for removing (discharging) the aqueous medium present between the adherend and the window film is to sequentially and uniformly rub the film surface with a squeegee to push out and remove the aqueous medium. In this process, air bubbles formed between the window film and the adherend can be pushed out, and wrinkles formed in the window film can be smoothed out.

[0029] Furthermore, the hard coat film according to this embodiment is preferably used as an optical film used in the field of optics. In particular, it is preferably an optical film used for screen protection of a display. Examples of display devices for the display include liquid crystal (LCD) displays, light-emitting diode (LED) displays, organic electroluminescent (organic EL) displays, and electrophoretic displays (electronic paper). Examples of display configurations include flexible displays such as stretchable displays and rollable displays, micro-LED displays, mini-LED displays, and large-screen tiling displays. These may also be touch panels equipped with position input means.

[0030] As shown in Figure 1A, the hard coat film 1 according to this embodiment comprises a substrate 10 and a hard coat layer 20. The hard coat layer 20 is formed on the main surface 10a of the substrate 10.

[0031] The total thickness of the hard coat film may be 10 to 500 μm, 20 to 300 μm, 30 to 200 μm, or 40 to 175 μm. The total thickness of the hard coat film is the sum of the thicknesses of the layers that make up the hard coat film. Therefore, if the hard coat film has layers other than the substrate and the hard coat layer, the thickness of the layers other than the substrate and the hard coat layer is also included in the total thickness of the hard coat film.

[0032] The thickness of the hard coat layer may be 0.5 to 20 μm, 1 to 15 μm, 2 to 10 μm, or 3 to 7 μm, from the viewpoint of surface hardness, scratch resistance, and weather resistance of the hard coat film.

[0033] The thickness of layers other than the hard coat layer in a hard coat film may be 10 to 500 μm, 20 to 300 μm, 30 to 200 μm, or 40 to 175 μm. The thickness of layers other than the hard coat layer is the sum of the thicknesses of the layers constituting the hard coat film minus the thickness of the hard coat layer. Therefore, if the hard coat film has layers other than the substrate and the hard coat layer, the thickness of the substrate and the layers other than the hard coat layer is included in the thickness of layers other than the hard coat layer.

[0034] (1.1. Relationship between the flexibility of the hard coat layer and the total thickness of the hard coat film) In this embodiment, the flexibility of the hard coat layer and the total thickness of the hard coat film are controlled. The flexibility of the hard coat layer is evaluated by a mandrel bending test. Specifically, in accordance with JIS K 5600-5-1, a cylindrical mandrel bending tester is used to perform a mandrel bending test by bringing the surface of the hard coat film facing the substrate (in Figure 1A, the main surface opposite to the main surface 10a of the substrate 10) into contact with the mandrel. In the mandrel bending test, the hard coat film is folded so as to wrap around a mandrel of a predetermined diameter, and it is visually observed whether cracks occur in the hard coat layer. Compared to a mandrel with a larger diameter, a mandrel with a smaller diameter has a larger curvature, resulting in a greater degree of bending of the hard coat film. That is, when a mandrel with a smaller diameter is used, cracks are more likely to occur in the hard coat layer. Therefore, bending tests are performed sequentially starting with the mandrel with the largest diameter, and the diameter of the mandrel when cracks first occur is defined as Dμm. For example, if a crack first appears in the hard coat layer when using a mandrel with a diameter of 8 mm, then D will be 8000 μm.

[0035] In the present embodiment, when the total thickness of the hard coat film is α μm, it is preferable that D / α is 130 or less. In the mandrel bending test, as the hard coat layer where cracks are likely to occur (the diameter of the mandrel where cracks occur is large), a hard coat layer with a large thickness tends to be prone to cracking during bending. And the force to bend the hard coat film acting before or during construction is almost constant and hardly depends on the thickness of the hard coat film. Therefore, even in the case of a hard coat layer where cracks are likely to occur (the diameter of the mandrel where cracks occur is large) in the mandrel bending test, by controlling the relationship between the total thickness of the hard coat film and the diameter of the mandrel as described above, cracks and fractures are unlikely to occur during actual construction.

[0036] From the above viewpoints, D / α may be 10 to 115, or may be 25 to 100, or may be 40 to 90, or may be 50 to 80, or may be 60 to 70.

[0037] (1.2. Relationship between the thickness of the hard coat layer and the total thickness of the hard coat film) In the present embodiment, when the thickness of the hard coat layer is B μm, it is preferable that 100B / α indicating the ratio of the thickness of the hard coat layer to the total thickness α of the hard coat film is more than 0% and 8% or less. Thereby, even when a force to bend the hard coat film acts, the force applied to the hard coat layer becomes small, and cracks and fractures are less likely to occur in the hard coat layer.

[0038] From the above viewpoints, 100B / α may be 0.5 to 7%, or may be 1 to 6%, or may be 1.5 to 5%, or may be 2 to 3%.

[0039] In this embodiment, when the thickness other than the hard coat layer is A μm, it is preferable that 100A / α, which represents the ratio of the thickness other than the hard coat layer in the total thickness α of the hard coat film, is 92% or more and less than 100%. Thereby, it becomes easier for 100B / α described above to satisfy the desired range, and even when a force for bending the hard coat film acts, the force applied to the hard coat layer becomes small, and cracks and fractures are less likely to occur in the hard coat layer.

[0040] From the above viewpoints, 100A / α may be 93 to 99.5%, or may be 96 to 99%, or may be 95 to 98.5%, or may be 97 to 98%.

[0041] (1.3. Hard coat layer) The hard coat layer according to this embodiment is superior in hard coat properties such as hardness, scratch resistance, and weather resistance to the base material. The hard coat film is attached to the adherend so that the hard coat layer is exposed to the outside. Therefore, even if some external force is applied to the hard coat film after construction, it is difficult for the base material to be damaged. In addition, since it is difficult for direct external force to be transmitted to the adherend (for example, windows of automobiles or buildings), excellent impact resistance can be exhibited. Furthermore, even if the adherend is cracked, it is possible to suppress the fragments from scattering, so excellent scattering prevention properties can be exhibited. Therefore, safety can be enhanced.

[0042] The hard coat layer may have functions other than hard coat properties. Examples of such functions include ultraviolet absorption, infrared absorption, low reflectivity, heat insulation, antifogging, sound insulation, antiglare, high transparency, high refractive index, oil absorption, fingerprint resistance, and scratch repair properties.

[0043] The formation weight per unit area of the hard coat layer is preferably 1 to 20 g / m 2 from the viewpoint of improving the surface hardness, scratch resistance, and weather resistance of the hard coat film, more preferably 3 to 15 g / m 2 and even more preferably 3 to 10 g / m 2

[0044] The hard coat layer is preferably composed of a material that can impart high hardness, scratch resistance, and weather resistance. The hard coat layer according to the present embodiment is preferably obtained by applying and drying a composition for forming a hard coat layer.

[0045] (1.3.1. Composition for forming hard coat layer) In the present embodiment, the composition for forming a hard coat layer preferably contains a siloxane compound. A siloxane compound is a silicon compound having a siloxane bond, and examples thereof include inorganic silica-based compounds (including poly silicic acid), polyorganosiloxane-based compounds, and the like.

[0046] The inorganic silica-based compound and the polyorganosiloxane-based compound can be obtained, for example, by the following methods. That is, a method of partially or completely hydrolyzing and polycondensing an alkoxysilane compound represented by the following general formula (1) using an inorganic acid such as hydrochloric acid or sulfuric acid, or an organic acid such as oxalic acid or acetic acid is exemplified. R 1 n Si(OR 2 ) 4-n ...(1) In the general formula (1), R 1 is a non-hydrolyzable group, which is an alkyl group, a substituted alkyl group (substituents: halogen atom, epoxy group, (meth)acryloyloxy group, etc.), an alkenyl group, an aryl group or an aralkyl group, R 2 is a lower alkyl group, and n is an integer of 0 or 1 or more and 3 or less. When there are a plurality of R 1 and OR 2 respectively, the plurality of R 1 may be the same or different, and the plurality of OR 2 may be the same or different.

[0047] In the general formula (1), when the compound in which n is 0, that is, tetraalkoxysilane is completely hydrolyzed, inorganic silica is obtained, and when it is partially hydrolyzed, a polyorganosiloxane or a mixture of an inorganic silica-based and a polyorganosiloxane-based is obtained. On the other hand, in the compound where n is 1 or more and 3 or less, since it has a non-hydrolyzable group, a polyorganosiloxane is obtained by partial or complete hydrolysis. At this time, an appropriate organic solvent may be used to perform hydrolysis uniformly.

[0048] Specific examples of alkoxysilane compounds represented by general formula (1) include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, and butyltrimethoxysilane. Examples include lan, phenyltrimethoxysilane, phenyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-acryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, dimethyldimethoxysilane, methylphenyldimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, divinyldimethoxysilane, divinyldiethoxysilane, trivinylmethoxysilane, trivinylethoxysilane, etc., and one or more of these can be used in combination.

[0049] Furthermore, when synthesizing silicon compounds having siloxane bonds, aluminum compounds (e.g., aluminum chloride or trialkoxyaluminum) can be used.

[0050] Furthermore, as an alternative method, a silicon compound raw material can be treated with sodium metasilicate, sodium orthosilicate, or water glass (a mixture of sodium silicates), and subjected to hydrolysis by reacting it with an acid such as hydrochloric acid, sulfuric acid, or nitric acid, or a metal compound such as magnesium chloride or calcium sulfate.

[0051] This hydrolysis process generates free silicic acid, which polymerizes readily and rapidly forms siloxane bonds. Depending on the type of raw material, a mixture of linear, cyclic, and network-like silicon compounds (silicon compounds containing siloxane bonds) is usually obtained.

[0052] Polysilicic acid obtained from water glass is usually composed mainly of a chain-like structure represented by the following general formula (2).

[0053] In general formula (2), m represents the degree of polymerization, and R is hydrogen, silicon, or a metal such as magnesium or aluminum.

[0054] Furthermore, as a constituent material for the hard coat layer, for example, silica gel (SiO₂) X nH₂O can also be used.

[0055] The hard coat layer may be composed mainly of siloxane compounds, but may also contain components other than siloxane compounds. The content of siloxane compounds in 100% by mass of the hard coat layer is preferably 90% by mass or more, more preferably 95% by mass or more, and the upper limit may be 100% by mass or less, or 99.9% by mass or less.

[0056] The hard coat layer forming composition does not necessarily have to contain a siloxane compound. An example of a hard coat layer forming composition that does not contain a siloxane compound is an active energy ray curable hard coat layer forming composition. The hard coat layer forming composition preferably contains an active energy ray curable resin and a photopolymerization initiator.

[0057] The active energy ray-curable resin is not particularly limited, and conventionally known resins can be selected. Examples include active energy ray-curable monomers, oligomers, or compositions containing them.

[0058] Examples of active energy ray-curable monomers include polyfunctional (meth)acrylates. Examples of active energy ray-curable oligomers include urethane (meth)acrylates, polyester (meth)acrylates, polyether (meth)acrylates, and silicone (meth)acrylates.

[0059] When the active energy ray curable resin is an ultraviolet (UV) curable resin, the hard coat layer forming composition preferably contains a photopolymerization initiator. This allows for efficient formation of the hard coat layer when the hard coat layer forming composition is irradiated with ultraviolet light. Here, a photopolymerization initiator refers to a compound that generates radical species upon irradiation with active energy rays such as ultraviolet light. The photopolymerization initiator can be selected from known photopolymerization initiators depending on the type of active energy ray curable resin used.

[0060] (1.3.2. Other Additives) The hard coat layer forming composition may optionally contain other additives, to the extent that it does not impair the effects of the present invention. Examples of other additives include antioxidants, ultraviolet absorbers, infrared absorbers, antistatic agents, colorants, polymerization accelerators, polymerization inhibitors, leveling agents, plasticizers, antiviral agents, antibacterial agents, fillers, and diluent solvents.

[0061] (1.4. Substrate) The substrate is a material that provides rigidity to the hard coat film and functions as a substrate that supports the hard coat layer. The material of the substrate is not particularly limited as long as it has the above-mentioned function. In this embodiment, a resin film is preferably used.

[0062] Examples of such resin films include polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyolefin resins such as polyethylene, polypropylene, poly-methylpentene-1, and polybutene-1; polyurethane resins; polycarbonate resins; polyvinyl chloride resins; polyethersulfone resins; polyethylene sulfide resins; styrene resins; acrylic resins; polyamide resins; and cellulose resins such as cellulose acetate, or films made of these materials or laminated films. Furthermore, in order to increase the biomass content of the hard coat film, materials with a high biomass content may be used as the resin film constituting the base material, or, from the perspective of SDGs, materials that can be recycled or reused may be used, or recycled or reused materials may be used.

[0063] Among these, films made of polyolefin resins and polyester resins, or laminated films thereof, which have excellent mechanical strength and cost-effectiveness, are preferred, and films made of polyester resins or laminated films thereof are particularly preferred.

[0064] To improve adhesion to the layer provided on the substrate, one or both sides of the substrate may be surface-treated by oxidation, embossing, or other methods, or another layer such as a primer layer may be formed. Examples of oxidation methods include corona discharge treatment, chromic acid treatment (wet), flame treatment, hot air treatment, and ozone / ultraviolet irradiation treatment. Examples of embossing methods include sandblasting and solvent treatment.

[0065] The thickness of the base material is not particularly limited as long as it exhibits a predetermined rigidity, and can be set appropriately according to the intended use. In this embodiment, from the viewpoint of ensuring mechanical strength suitable for workability during construction, the thickness of the base material may be 5 to 200 μm, 10 to 100 μm, 20 to 80 μm, or 30 to 60 μm.

[0066] In this embodiment, the hard coat film may have other components as long as the effects of the present invention are obtained. That is, the hard coat film may have layers other than the substrate and the hard coat layer. For example, in order to securely fix the window film to the adherend, as shown in Figure 1B, an adhesive layer 30 may be arranged on the main surface 10b of the substrate 10 opposite to the main surface 10a on which the hard coat layer 20 is formed. If an adhesive layer 30 is arranged, a release sheet may be arranged on the main surface 30a of the adhesive layer 30 to protect the adhesive layer 30 until it is attached to the adherend (not shown).

[0067] (1.5. Adhesive Layer) The adhesive layer may consist of one layer (single layer) or of two or more layers. If the adhesive layer has multiple layers, these layers may be identical or different from one another, and there are no particular restrictions on the combination of layers that make up these multiple layers.

[0068] The thickness of the adhesive layer may be 1 to 100 μm, preferably 4 to 70 μm, more preferably 7 to 50 μm, even more preferably 10 to 40 μm, and particularly preferably 12 to 30 μm. This makes it easier to achieve suitable adhesive properties.

[0069] The composition of the adhesive constituting the adhesive layer is not particularly limited. For example, it may be any of the following: acrylic adhesive, polyester adhesive, polyurethane adhesive, rubber adhesive, silicone adhesive, etc. Furthermore, the adhesive may be of emulsion type, solvent type, or solvent-free type. In addition, the adhesive may or may not have a cross-linked structure.

[0070] When the composition of the adhesive is an acrylic adhesive having a crosslinked structure, an example of such an adhesive is one obtained by crosslinking an adhesive composition containing a (meth)acrylic acid ester polymer and a crosslinking agent. In this specification, (meth)acrylic acid refers to both acrylic acid and methacrylic acid. Furthermore, the concept of "polymer" also includes the concept of "polymer."

[0071] Examples of (meth)acrylic acid ester polymers include polymers that contain units derived from alkyl (meth)acrylic acid esters and units derived from monomers having reactive functional groups in the molecule (reactive functional group-containing monomers) as monomer units.

[0072] Examples of alkyl (meth)acrylates include alkyl (meth)acrylates in which the alkyl group has 1 to 20 carbon atoms. Examples of monomers containing reactive functional groups include monomers having a hydroxyl group in the molecule (hydroxyl group-containing monomers) and monomers having a carboxyl group in the molecule (carboxyl group-containing monomers).

[0073] Preferred crosslinking agents are those that react with the reactive functional groups of the (meth)acrylic acid ester polymer, such as isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-based crosslinking agents.

[0074] The adhesive may contain additives commonly used in adhesives, as needed. Examples of such additives include ultraviolet absorbers, infrared absorbers, tackifiers, fillers, softeners, antioxidants, light stabilizers, crosslinking agents, colorants, modifiers, rust inhibitors, flame retardants, hydrolysis inhibitors, surface lubricants, corrosion inhibitors, heat stabilizers, lubricants, antistatic agents, polymerization inhibitors, catalysts, leveling agents, thickeners, dispersants, defoamers, and surfactants.

[0075] (1.6. Functional Layer) In addition to the substrate and the hard coat layer, the hard coat film may also have a functional layer. This allows the hard coat film to be given various functions. Examples of functions that the functional layer may have include heat shielding, ultraviolet absorption, low reflectivity, anti-fogging, sound insulation, anti-glare, high transparency, high refractive index, oil absorption, weather resistance, fingerprint resistance, scratch repair, etc. In this embodiment, it is preferable that the functional layer is a layer having heat shielding properties (heat shielding layer).

[0076] The functional layer is usually preferably formed on the side of the substrate opposite to the side on which the hard coat layer is formed. When the adhesive layer is formed on the side of the substrate opposite to the side on which the hard coat layer is formed, the functional layer 40 is preferably formed between the substrate 10 and the adhesive layer 30, as shown in Figure 2A. Also, as shown in Figure 2B, in order to improve adhesion, the functional layer 40 may be formed on a substrate 11 separate from the substrate 10 on which the hard coat layer 20 is formed, and integrated with the substrate 10 via another adhesive layer 31.

[0077] If the functional layer is a heat-shielding layer, the heat-shielding layer may be infrared-absorbing, infrared-reflective, or both infrared-absorbing and infrared-reflective. This allows, for example, when a hard coat film is applied to the outside of a window, which is the substrate, to reduce the amount of infrared radiation incident on the inside of the window and suppress the rise in temperature on the inside.

[0078] The thickness of the functional layer is not particularly limited as long as it exhibits the predetermined function, and can be set appropriately according to the intended use. In this embodiment, the thickness of the functional layer may be 0.1 to 10 μm, 0.4 to 6 μm, 0.8 to 3 μm, or 1 to 2 μm.

[0079] (1.7. Physical Properties of Hard Coat Film) The hard coat film according to this embodiment preferably has the following physical properties.

[0080] (1.7.1. Infrared shielding rate of hard coat film) The hard coat film according to this embodiment preferably has a light shielding rate (infrared shielding rate) of 10% or more in the wavelength range of 780 to 2500 nm. This allows the hard coat film to exhibit good heat shielding properties, which can suppress the rise in surface temperature of components and people inside buildings and automobiles, as well as suppress the rise in temperature of the interior space.

[0081] The infrared shielding rate is preferably 15% or more, more preferably 30% or more, even more preferably 40% or more, particularly preferably 50% or more, and most preferably 65% ​​or more.

[0082] The infrared shielding rate of a hard coat film can be calculated from the infrared transmittance measured in accordance with JIS A 5759:2016. The specific measurement method will be explained in the examples described later.

[0083] (1.7.2. Shading coefficient of hard coat film) The shading coefficient of the hard coat film according to this embodiment is preferably 0.99 or less, more preferably 0.95 or less, even more preferably 0.92 or less, even more preferably 0.90 or less, and most preferably 0.88 or less. This improves the heat shielding capacity of the substrate (for example, a window) to which the hard coat film is attached, and provides an energy-saving effect.

[0084] The shielding coefficient of the hard coat film can be measured in accordance with JIS A 5759:2016. The specific measurement method will be explained in the examples described later.

[0085] (1.7.3. Scratch Resistance of Hard Coat Film) The hard coat film according to this embodiment contains 250 g / cm³ of #0000 steel wool. 2 After moving the steel wool back and forth 10 times while applying pressure on the hard coat layer, it is preferable that there are 20 or fewer scratches, more preferably 10 or fewer, even more preferably 3 or fewer, and particularly preferable that no scratches are observed. This suppresses the occurrence of scratches on the hard coat layer during and after application. Scratch resistance can be measured by the method shown in the test examples described later.

[0086] (1.8. Manufacturing of Hard Coat Film) The method for manufacturing the hard coat film is not particularly limited and may be manufactured by known methods. For example, a hard coat layer may be formed on one main surface of a resin film used as a substrate. Specifically, the coating solution of the hard coat layer forming composition Q described above is applied to one main surface of the resin film. The coating solution of the hard coat layer forming composition Q can be prepared by mixing the components constituting the hard coat layer forming composition Q and, if necessary, using a known diluent. Examples of methods for applying the coating solution include bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating. After coating, the hard coat layer is formed on the resin film by drying.

[0087] If the hard coat film has an adhesive layer, the adhesive layer can be obtained by applying a coating solution of a composition for forming the adhesive layer (adhesive composition) to the other main surface of a resin film that does not have a hard coat layer, and then drying it. If the adhesive composition contains a crosslinking agent, an adhesive layer containing a crosslinked structure may be obtained by heating, curing, etc., of the adhesive composition as necessary.

[0088] If the hard coat film has layers other than the substrate, hard coat layer, and adhesive layer, the layer can be obtained by applying a composition for forming the layer onto the other main surface of the resin film used as the substrate, and then drying and curing it. Alternatively, the material constituting the layer may be bonded to the substrate via an adhesive layer or the like, or the layer formed on a separate resin film may be bonded to the substrate via an adhesive layer or the like.

[0089] In this specification, when "X to Y" (where X and Y are any numbers) is written, unless otherwise specified, it includes the meaning of "greater than or equal to X and less than or equal to Y," as well as "preferably greater than X" or "preferably less than Y." Similarly, when "greater than or equal to X" (where X is any number) is written, unless otherwise specified, it includes the meaning of "preferably greater than X," and when "less than or equal to Y" (where Y is any number) is written, unless otherwise specified, it also includes the meaning of "preferably less than Y."

[0090] Although embodiments of the present invention have been described above, the present invention is not limited in any way to the embodiments described above, and may be modified in various ways within the scope of the present invention.

[0091] The invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0092] (Example 1) (Manufacturing of hard coat film) A polyethylene terephthalate (PET) film with a thickness of 50 μm was prepared as a substrate. A siloxane-based hard coat agent containing a siloxane compound (manufactured by Doken Co., Ltd., product name "Surcoat SCH720") was applied to one main surface of the PET film using a Meyer bar so that the thickness after drying was 4 μm. After coating, it was dried at 130°C for 3 minutes to obtain a hard coat film (total thickness α = 54 μm) having the structure of "substrate (thickness 50 μm) / hard coat layer (thickness B = 4 μm)".

[0093] (Examples 2 to 4 and Comparative Example 1) Hard coat films were obtained by the same method as in Example 1, except that the hard coat layer was coated to the thickness shown in Table 1.

[0094] (Example 5) As the first substrate, a polyethylene terephthalate (PET) film with a thickness of 50 μm (manufactured by Teijin Film Solutions Co., Ltd., product name "Tetron Film HB3-50", containing an ultraviolet absorber) was prepared. A mixture (coating liquid) of two types of acrylic resins (manufactured by Doken Co., Ltd., product name "Surcoat Primer SCP531" and product name "Surcoat Primer SCP500") was applied to one main surface of the PET film using a Meyer bar so that the thickness after drying would be 1 μm. After coating, it was dried at 100°C for 1 minute to form a primer layer.

[0095] Next, a siloxane-based hard coat agent containing a siloxane compound (manufactured by Doken Co., Ltd., product name "Surcoat SCH720") was applied to the surface of the primer layer using a Meyer bar so that the thickness after drying would be 3 μm. After application, it was dried at 130°C for 3 minutes to form a hard coat layer (thickness B = 3 μm).

[0096] Next, an acrylic adhesive (UV-absorbing) was applied to the side of the first substrate opposite to the side where the primer layer and hard coat layer were provided, using a comma coater. After application, it was dried at 100°C for 3 minutes to form a first adhesive layer with a thickness of 10 μm. Furthermore, a 50 μm thick polyethylene terephthalate (PET) film (manufactured by Teijin Film Solutions Co., Ltd., product name "Tetron Film HB3-50", containing a UV absorber) was laminated onto the exposed surface of this first adhesive layer as a second substrate.

[0097] Furthermore, on the second substrate, an acrylic adhesive was applied using a comma coater to the surface opposite to the surface on which the first adhesive layer, the first substrate, the primer layer, and the hard coat layer were provided, and then dried at 100°C for 3 minutes to form a second adhesive layer (UV absorbing) with a thickness of 14 μm.

[0098] The surface of the second adhesive layer was bonded to the surface of a release sheet, which had a release layer formed on one side of a polyethylene terephthalate sheet with a thickness of 25 μm. This resulted in a hard coat film (total thickness α = 153 μm) having the following configuration: "release sheet / second adhesive layer / second substrate / first adhesive layer / first substrate / primer layer / hard coat layer".

[0099] (Example 6) In the same manner as in Example 5, a laminate was obtained in which a primer layer and a hard coat layer were provided on one main surface of the first substrate, and a first adhesive layer was formed on the other main surface. Next, instead of the second substrate, a polyethylene terephthalate (PET) film with a thickness of 50 μm (manufactured by Toyobo Co., Ltd., product name "Cosmoshine A4360") was prepared as the third substrate, and a near-infrared cut coat layer (thickness: 1.5 μm) was provided on one main surface of the PET film, and the near-infrared cut coat layer and the first adhesive layer were bonded together.

[0100] Furthermore, on the third substrate, a second adhesive layer (ultraviolet-absorbing) was formed on the side opposite to the side where the near-infrared cut coating layer, the first adhesive layer, the first substrate, the primer layer, and the hard coat layer were provided, and it was bonded to the release layer surface of the release sheet of Example 5. Other conditions were the same as in Example 5. As a result, a hard coat film (total thickness α = 154.5 μm) having the configuration of "release sheet / second adhesive layer / third substrate / near-infrared cut coating layer / first adhesive layer / first substrate / primer layer / hard coat layer" was obtained.

[0101] (Reference Example 1) A polyethylene terephthalate (PET) film with a thickness of 50 μm was used. In other words, no hard coat layer was formed on the PET film.

[0102] The hard coat films prepared in the examples and comparative examples (Examples 1 to 6, Comparative Example 1, and Reference Example 1) were subjected to the following measurements and evaluations. Furthermore, the ratio of the hard coat layer thickness B to the total thickness of the hard coat film (100B / α (%)) was calculated from the total thickness α and the hard coat layer thickness B of each hard coat film. Additionally, the ratio of the thickness A of the layers other than the hard coat layer to the total thickness (100A / α (%)) was calculated from the total thickness α and the thickness A of the layers other than the hard coat layer of each hard coat film. The results are shown in Table 1.

[0103] (Cylindrical Mandrel Flexing Test) The hard coat films prepared in the examples and comparative examples were subjected to a mandrel bending test in accordance with JIS K5600-5-1 (1999) using a cylindrical mandrel bending tester (TQC Corporation, KT-SP1820). In this test, the substrate (Examples 1-4 and Comparative Example 1) or release sheet (Examples 5 and 6) was brought into contact with the mandrel. The test was started with a mandrel with a large diameter, and if no cracks were visually observed in the hard coat layer, the test was changed to a mandrel with a smaller diameter, and the diameter of the mandrel when cracks were first visually observed in the hard coat layer was defined as D μm. For example, if no cracks occurred in the hard coat layer when using a mandrel with a diameter of 10 mm, but cracks occurred in the hard coat layer when using a mandrel with a diameter of 8 mm, then D is 8000 μm (8 mm). The ratio D / α was calculated from the obtained value D and the total thickness α of the hard coat film. The results are shown in Table 1. Note that no test was performed for Reference Example 1.

[0104] (Scratch resistance of the hard coat layer) The scratch resistance of the hard coat layer of the hard coat film was evaluated as follows. For the hard coat films obtained in Examples 1 to 4, Comparative Example 1, and Reference Example 1, first, an adhesive layer (thickness: 14 μm) similar to the second adhesive layer of Example 5 formed on a release sheet was laminated to a PET film as a base material. The release sheet was peeled off, and the exposed adhesive layer was attached to a float glass plate with a thickness of 3 mm. For the hard coat films obtained in Examples 5 and 6, the release sheet was peeled off, and the exposed second adhesive layer was attached to a float glass plate with a thickness of 3 mm.

[0105] Steel wool with a grit of #0000 was placed on the hard coat layer of a hard coat film, and the steel wool was subjected to abrasion testing at 250 g / cm² using a flat abrasion tester (PA-2A, manufactured by Daiei Kagaku Seiki Seisakusho). 2 The steel wool was moved back and forth 10 times while applying pressure. Afterwards, the areas on the hard coat layer where the steel wool was moved were visually observed, and scratches were evaluated according to the following criteria. In addition, tests were conducted using the same method as above, with the steel wool moved back and forth 20 times and 30 times. For Reference Example 1, the above test was performed on a PET film. The results are shown in Table 1. A: No scratches were observed A': 1 to 3 scratches were observed B: 4 to 10 scratches were observed C: 11 to 20 scratches were observed D: 21 or more scratches were observed

[0106] (Shielding coefficient and infrared shielding rate of hard coat film) For the hard coat films obtained in Examples 1 to 4, Comparative Example 1, and Reference Example 1, first, an adhesive layer (thickness: 14 μm) similar to the second adhesive layer of Example 5 formed on a release sheet was laminated to a PET film as a base material. The release sheet was peeled off, and the exposed adhesive layer was attached to a float glass plate with a thickness of 3 mm. For the hard coat films obtained in Examples 5 and 6, the release sheet was peeled off, and the exposed second adhesive layer was attached to a float glass plate with a thickness of 3 mm.

[0107] After performing background measurements on the float glass plate in advance, the solar transmittance and solar reflectance of the hard coat film were measured from the hard coat layer side using a spectrophotometer (Shimadzu Corporation, product name "UV-3600") in accordance with JIS A 5759:2016. The amount of heat inflow was calculated from the measured values, and the shading coefficient was calculated using the following formula (1). The results are shown in Table 1. Shading coefficient = Amount of heat inflow to the measured sample / Amount of heat inflow to the float glass (1)

[0108] Furthermore, in the above measurements, the light transmittance (infrared transmittance) (%) in the wavelength range of 780 to 2500 nm was calculated, and the value obtained by subtracting this value from 100% was defined as the infrared shielding rate (%). The results are shown in Table 1.

[0109] (Crack Initiation Evaluation) Using the hard coat films obtained in Examples 1 to 6 and Comparative Example 1, a water application evaluation was performed to simulate actual application, and crack initiation was evaluated. For Examples 1 to 4 and Comparative Example 1, similar to the evaluation of the scratch resistance of the hard coat layer described above, an adhesive layer (thickness: 14 μm) similar to the second adhesive layer of Example 5 formed on the release sheet was provided on the PET film used as the base material. No evaluation was performed for Reference Example 1.

[0110] Specifically, a 10% by mass aqueous solution of an anionic surfactant was sprayed onto the entire outer surface of the windshield (Volvo S60 model) using a sprayer. Then, the adhesive layer of the hard coat film obtained in Examples 1-6 and Comparative Example 1 was placed on the windshield surface, and the hard coat film was applied manually using a squeegee while pressing it down. This process was repeated five times. After the application, the hard coat layer was visually inspected for cracks and evaluated according to the following criteria: A: One or fewer cracks were found in the hard coat layer. D: Two or more cracks were found in the hard coat layer.

[0111]

[0112] Table 1 shows that the hard coat film of the example suppressed crack formation during work and exhibited excellent scratch resistance.

[0113] The hard coat film of the present invention is suitable, for example, as a protective film for windows of moving objects such as automobiles, windows of buildings, or as an optical film used in display devices such as various displays.

[0114] 1...Hard coat film 10, 11...Substrate 20...Hard coat layer 30, 31...Adhesive layer 40...Functional layer (heat shielding layer)

Claims

1. A hard coat film having a base material and a hard coat layer disposed on one main surface of the base material, wherein in a mandrel bending test performed in accordance with JIS K 5600-5-1 using a cylindrical mandrel bending tester, with the surface of the hard coat film on the base material side in contact with the mandrel, the hard coat film has a diameter of D μm at which cracks occur in the hard coat layer, and the total thickness of the hard coat film is α μm, and D / α is 130 or less.

2. The hard coat film according to claim 1, wherein when the thickness of the hard coat layer is B μm, 100B / α is greater than 0% and less than or equal to 8%.

3. The hard coat film according to claim 1 or 2, wherein the infrared shielding rate of the hard coat film is 10% or more.

4. The hard coat film according to claim 3, wherein the infrared shielding rate of the hard coat film is 50% or more.

5. The hard coat film according to claim 1 or 2, wherein the shielding coefficient of the hard coat film is 0.99 or less.

6. The hard coat film according to claim 5, wherein the shielding coefficient of the hard coat film is 0.90 or less.

7. The hard coat film according to claim 1 or 2, wherein the hard coat film is a window film.

8. The hard coat film according to claim 7, wherein the window film is a film that is affixed to the outside of a window.

9. The hard coat film according to claim 1 or 2, wherein the hard coat film is a film used in the field of optics.

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