JP7265682B2 - Optical film with antifouling layer - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical film with an antifouling layer.

From the standpoint of antifouling properties, for example, an optical film with an antifouling layer is attached to the outer surface of a display such as a touch panel display on the image display side. An optical film with an antifouling layer includes a transparent substrate and an antifouling layer disposed on the outermost surface on one side of the transparent substrate. The antifouling layer suppresses adhesion of contaminants such as oil from hands to the surface of the display, and facilitates removal of adhered contaminants. Techniques related to such an optical film with an antifouling layer are described, for example, in Patent Document 1 below.

Japanese Patent Application Laid-Open No. 2020-52221

During use of the optical film with an antifouling layer, contaminants adhering to the antifouling layer are removed by, for example, wiping. However, repeated wiping of the antifouling layer causes deterioration of the antifouling property of the antifouling layer and causes peeling of the antifouling layer. From the viewpoint of the antifouling function of the optical film with an antifouling layer, deterioration in the antifouling property and peeling of the antifouling layer are undesirable.

The present invention provides an optical film with an antifouling layer, which is suitable for suppressing deterioration of the antifouling property while ensuring peeling resistance of the antifouling layer.

The present invention [1] comprises a transparent substrate, a hard coat layer, an inorganic oxide base layer, and an antifouling layer in this order, and the antifouling layer is disposed on the inorganic oxide base layer. The antifouling layer is a dry coating film, and the surface of the antifouling layer opposite to the inorganic oxide underlayer has a hardness of 1.05 GPa or more at 25° C. measured by a nanoindentation method. Includes layered optical films.

In the present invention [2], the product of the elastic recovery rate at 25° C. measured by the nanoindentation method and the hardness (GPa) of the surface of the antifouling layer is 0.8 or more. The optical film with an antifouling layer according to [1] above is included.

The present invention [3] is described in the above [1] or [2], wherein the surface of the antifouling layer has an elastic recovery rate at 25°C measured by a nanoindentation method of 0.76 or more. including an optical film with an antifouling layer.

The present invention [4] includes the optical film with an antifouling layer according to any one of [1] to [3] above, wherein the antifouling layer has a thickness of 1 nm or more and 25 nm or less.

The present invention [5] includes the optical film with an antifouling layer according to any one of [1] to [4] above, wherein the inorganic oxide underlayer contains silicon dioxide.

The present invention [6] includes the optical film with an antifouling layer according to any one of [1] to [5] above, wherein the inorganic oxide underlayer has a thickness of 50 nm or more.

The present invention [7] includes the optical film with an antifouling layer according to any one of [1] to [6] above, wherein the hard coat layer has a thickness of 1 μm or more and 50 μm or less.

As described above, the antifouling layer-attached optical film of the present invention is a dry coating film in which the antifouling layer is disposed on the inorganic oxide underlayer. Such a configuration is suitable for ensuring high bonding strength of the antifouling layer in the optical film with the antifouling layer, and therefore suitable for ensuring the peeling resistance of the antifouling layer. Further, in the optical film with an antifouling layer, the surface of the antifouling layer opposite to the inorganic oxide underlayer has a hardness of 1.05 GPa or more at 25° C. measured by a nanoindentation method. Such a configuration is suitable for suppressing deterioration of the antifouling property of the antifouling layer against wiping work on the antifouling layer.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram of one Embodiment of the optical film of this invention. It is a cross-sectional schematic diagram of the modification of the optical film of this invention (In this modification, an optical film is provided with an antireflection layer). The surface hardness H (horizontal axis) measured for each optical film of Examples 1 to 9 and Comparative Example 1 and the measurement results of the water contact angle θ ₂ after the second eraser sliding test (vertical axis) were plotted. graph.

Optical film F as one embodiment of the optical film with an antifouling layer of the present invention comprises, as shown in FIG. 14 are provided in this order toward one side in the thickness direction T. In the present embodiment, the optical film F includes a transparent base material 11, a hard coat layer 12, an adhesion layer 15, an inorganic oxide base layer 13, and an antifouling layer 14 on one side in the thickness direction T. Prepare in this order. Further, the optical film F has a shape that spreads in a direction perpendicular to the thickness direction T (plane direction).

The transparent base material 11 is a flexible transparent resin film. Materials for the transparent substrate 11 include, for example, polyester resin, polyolefin resin, polystyrene resin, acrylic resin, polycarbonate resin, polyethersulfone resin, polysulfone resin, polyamide resin, polyimide resin, cellulose resin, norbornene resin, polyarylate resin, and polyvinyl alcohol resins. Polyester resins include, for example, polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Polyolefin resins include, for example, polyethylene, polypropylene, and cycloolefin polymers (COP). Cellulose resins include, for example, triacetyl cellulose (TAC). These materials may be used alone, or two or more of them may be used in combination. As the material of the transparent substrate 11, one selected from the group consisting of polyester resin, polyolefin resin, and cellulose resin is used from the viewpoint of transparency and strength, and more preferably PET, COP, and TAC. One selected from the group is used.

The hard coat layer 12 side surface of the transparent substrate 11 may be subjected to a surface modification treatment. Surface modification treatments include, for example, corona treatment, plasma treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment.

From the viewpoint of strength, the thickness of the transparent substrate 11 is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. The thickness of the transparent substrate 11 is preferably 300 μm or less, more preferably 200 μm or less, from the viewpoint of handleability.

The total light transmittance (JIS K 7375-2008) of the transparent substrate 11 is preferably 80% or higher, more preferably 90% or higher, and even more preferably 95% or higher. Such a configuration is suitable for ensuring the transparency required for the optical film F when the optical film F is provided on the surface of a display such as a touch panel display. The total light transmittance of the transparent substrate 11 is, for example, 100% or less.

The hard coat layer 12 is arranged on one surface in the thickness direction T of the transparent substrate 11 . The hard coat layer 12 is a layer for making the exposed surface (upper surface in FIG. 1) of the optical film F less likely to be scratched.

The hard coat layer 12 is a cured product of a curable resin composition. Examples of curable resins contained in the curable resin composition include polyester resins, acrylic resins, urethane resins, acrylic urethane resins, amide resins, silicone resins, epoxy resins, and melamine resins. These curable resins may be used alone, or two or more of them may be used in combination. From the viewpoint of ensuring high hardness of the hard coat layer 12, acrylic urethane resin is preferably used as the curable resin.

Moreover, examples of the curable resin composition include an ultraviolet curable resin composition and a thermosetting resin composition. As the curable resin composition, an ultraviolet curable resin composition is preferably used from the viewpoint of improving the production efficiency of the optical film F because it can be cured without high-temperature heating. The UV-curable resin composition contains at least one selected from the group consisting of UV-curable monomers, UV-curable oligomers, and UV-curable polymers. Specific examples of the UV-curable resin composition include the composition for forming a hard coat layer described in JP-A-2016-179686.

The curable resin composition may contain fine particles. The addition of fine particles to the curable resin composition is useful for adjusting the hardness, adjusting the surface roughness, adjusting the refractive index, and imparting antiglare properties of the hard coat layer 12 . Microparticles include, for example, metal oxide particles, glass particles, and organic particles. Materials for metal oxide particles include, for example, silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide. Materials for the organic particles include, for example, polymethylmethacrylate, polystyrene, polyurethane, acrylic-styrene copolymers, benzoguanamine, melamine, and polycarbonate.

The thickness of the hard coat layer 12 is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more, from the viewpoint of ensuring the hardness of the hard coat layer 12 to ensure the hardness of the surface of the antifouling layer 14 . From the viewpoint of ensuring the flexibility of the optical film F, the thickness of the hard coat layer 12 is preferably 50 μm or less, more preferably 40 μm or less, still more preferably 35 μm or less, and particularly preferably 30 μm or less.

The adhesion layer 15 side surface of the hard coat layer 12 may be subjected to a surface modification treatment. Surface modification treatments include, for example, plasma treatment, corona treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment. From the viewpoint of ensuring high adhesion between the hard coat layer 12 and the adhesion layer 15, the surface of the hard coat layer 12 on the side of the adhesion layer 15 is preferably plasma-treated.

The adhesion layer 15 is a layer for ensuring the adhesion of the inorganic oxide layer (the inorganic oxide base layer 13 in this embodiment) to the transparent substrate 11 . The adhesion layer 15 is arranged on one surface in the thickness direction T of the hard coat layer 12 . Examples of materials for the adhesion layer 15 include metals such as silicon, indium, nickel, chromium, aluminum, tin, gold, silver, platinum, zinc, titanium, tungsten, zirconium, and palladium, alloys of two or more of these metals, and oxides of these metals. The adhesion to both the organic layer (specifically, the hard coat layer 12) and the inorganic oxide layer (specifically, the inorganic oxide underlayer 13 in this embodiment) and the transparency of the adhesion layer 15 are compatible. From a viewpoint, indium tin oxide (ITO) or silicon oxide (SiOx) is preferably used as the material of the adhesion layer 15 . When silicon oxide is used as the material of the adhesion layer 15, preferably SiOx with less oxygen content than the stoichiometric composition is used, and more preferably SiOx with x of 1.2 or more and 1.9 or less is used. .

The thickness of the adhesion layer 15 is preferably 1 nm or more and 10 nm or less from the viewpoint of ensuring both the adhesion between the hard coat layer 12 and the inorganic oxide base layer 13 and the transparency of the adhesion layer 15. .

The inorganic oxide base layer 13 is a layer for ensuring peeling resistance in the antifouling layer 14 . Examples of the material of the inorganic oxide underlayer 13 include silicon dioxide (SiO ₂ ) and magnesium fluoride, preferably silicon dioxide.

The thickness of the inorganic oxide underlayer 13 is preferably 50 nm or more, more preferably 65 nm or more, even more preferably 80 nm or more, and particularly preferably 90 nm or more, from the viewpoint of ensuring the peeling resistance of the antifouling layer 14 . The thickness of the inorganic oxide underlayer 13 is, for example, 300 nm or less.

The antifouling layer 14 is a layer having an antifouling function. The antifouling layer 14 is arranged on one surface in the thickness direction T of the inorganic oxide underlayer 13 . The antifouling layer 14 has a surface 14a (outer surface) on one side in the thickness direction T. As shown in FIG. The antifouling function of the antifouling layer 14 includes a function of suppressing adhesion of contaminants such as hand grease to the exposed surface of the optical film F during use and a function of facilitating removal of adhering contaminants.

Materials for the antifouling layer 14 include, for example, fluorine group-containing organic compounds. As the fluorine group-containing organic compound, an alkoxysilane compound having a perfluoropolyether group is preferably used. Examples of the alkoxysilane compound having a perfluoropolyether group include compounds represented by the following general formula (1).

R ¹ -R ² -X-(CH ₂ ) _m -Si(OR ³ ) ₃ (1)

In general formula (1), R ¹ represents a linear or branched fluorinated alkyl group (having, for example, 1 or more and 20 or less carbon atoms) in which one or more hydrogen atoms in the alkyl group are substituted with fluorine atoms. preferably represents a perfluoroalkyl group in which all hydrogen atoms in an alkyl group are substituted with fluorine atoms.

R ² represents a structure containing at least one repeating structure of perfluoropolyether (PFPE) groups, preferably a structure containing two repeating structures of PFPE groups. Examples of repeating structures of PFPE groups include repeating structures of linear PFPE groups and repeating structures of branched PFPE groups. As the repeating structure of the linear PFPE group, for example, a structure represented by -(OC _n F _2n ) _p - (n represents an integer of 1 or more and 20 or less, p represents an integer of 1 or more and 50 or less The same applies below). As the repeating structure of the branched PFPE group, for example, a structure represented by -(OC(CF ₃ ) ₂ ) _p - and a structure represented by -(OCF ₂ CF(CF ₃ )CF ₂ ) _p - is mentioned. The repeating structure of the PFPE group preferably includes a repeating structure of a linear PFPE group, more preferably -(OCF ₂ ) _p - and -(OC ₂ F ₄ ) _p -.

R ³ represents an alkyl group having 1 to 4 carbon atoms, preferably a methyl group.

X represents an ether group, a carbonyl group, an amino group, or an amide group, preferably an ether group.

m represents an integer of 1 or more. In addition, m represents an integer of preferably 20 or less, more preferably 10 or less, and even more preferably 5 or less.

Among such alkoxysilane compounds having a perfluoropolyether group, compounds represented by the following general formula (2) are preferably used.

CF ₃ —(OCF ₂ ) _q —(OC ₂ F ₄ ) _r —O—(CH ₂ ) ₃ —Si(OCH ₃ ) ₃ (2)

In general formula (2), q represents an integer of 1 or more and 50 or less, and r represents an integer of 1 or more and 50 or less.

Moreover, the alkoxysilane compound having a perfluoropolyether group may be used alone, or two or more kinds thereof may be used in combination.

The antifouling layer 14 is a film (dry coating film) formed by a dry coating method. Dry coating methods include sputtering, vacuum deposition, and CVD. The antifouling layer 14 is preferably a film (vacuum vapor deposition film) formed by a vacuum vapor deposition method.

The material of the antifouling layer 14 contains an alkoxysilane compound having a perfluoropolyether group, and the antifouling layer 14 is a dry coating film (preferably a vacuum deposition film). It is suitable for ensuring high bonding strength of the antifouling layer 14 to the antifouling layer 13, and therefore suitable for ensuring the peeling resistance of the antifouling layer 14. The high antifouling property of the antifouling layer 14 helps maintain the antifouling function of the antifouling layer 14 .

The surface 14a of the antifouling layer 14 has a hardness of 1.05 GPa or more, preferably 1.1 GPa or more, and more preferably 1.15 GPa or more at 25° C. measured by a nanoindentation method. , more preferably 1.2 GPa or more, particularly preferably 1.25 GPa or more, particularly preferably 1.3 GPa or more. Such a configuration is suitable for suppressing deterioration of the antifouling property of the antifouling layer 14 against wiping operation on the antifouling layer 14 . The hardness (surface hardness H) of the surface 14a of the antifouling layer 14 at 25° C. measured by the nanoindentation method is preferably 30 GPa or less, more preferably 20 GPa or less, and still more preferably 15 GPa or less. Such a configuration is suitable for ensuring the flexibility of the antifouling layer 14 and therefore suitable for ensuring the flexibility of the optical film F.

The nanoindentation method is a technique for measuring various physical properties of samples on a nanometer scale. In this embodiment, the nanoindentation method is performed in compliance with ISO14577. In the nanoindentation method, a process of pushing an indenter into a sample set on a stage (loading process) and then a process of withdrawing the indenter from the sample (unloading process) are performed. The load acting between the indenter and the sample and the relative displacement of the indenter with respect to the sample are measured (load-displacement measurement). This makes it possible to obtain a load-displacement curve. From this load-displacement curve, physical properties such as hardness and elastic modulus based on nanometer scale measurement can be obtained for the measurement sample. For the load-displacement measurement of the antifouling layer surface by the nanoindentation method, for example, a nanoindenter (trade name “Triboindenter”, manufactured by Hysitron) can be used. In the measurement, the measurement mode is single indentation measurement, the measurement temperature is 25°C, the indenter used is a Berkovich (triangular pyramid) type diamond indenter, and the maximum indentation depth (maximum The displacement H1) is set to 200 nm, the pressing speed of the indenter is set to 20 nm/sec, and the withdrawal speed of the indenter from the measurement sample in the unloading process is set to 20 nm/sec. Based on the load-displacement curve obtained by this measurement, the maximum load Pmax (the load acting on the indenter at the maximum displacement H1), the projected contact area Ap (the projected area of the contact area between the indenter and the sample at the maximum load) , and the plastic deformation amount H2 (the depth of the recess maintained on the sample surface after the indenter is released from the sample surface) after the unloading process can be obtained. Then, the hardness (=Pmax/Ap) of the surface of the antifouling layer can be calculated from the maximum load Pmax and the projected contact area Ap. Further, from the maximum displacement H1 and the amount of plastic deformation H2, the elastic recovery rate (=(H1-H2)/H1) of the antifouling layer surface that has undergone load application and subsequent unloading can be calculated.

Methods for adjusting the surface hardness H of the antifouling layer 14 include, for example, adjusting the hardness and adjusting the thickness of the hard coat layer 12, and adjusting the hardness and adjusting the thickness of the base layer for the antifouling layer 14. is mentioned.

The elastic recovery rate (elastic recovery rate R) at 25° C. of the surface 14a of the antifouling layer 14 measured by the nanoindentation method is preferably 0.76 or more, more preferably 0.80 or more, and more preferably 0.80 or more. It is preferably 0.815 or more, particularly preferably 0.85 or more. Such a configuration is suitable for suppressing deterioration of the antifouling property of the antifouling layer 14 against wiping operation on the antifouling layer 14 . The elastic recovery rate (elastic recovery rate R) at 25° C. of the surface 14a of the antifouling layer 14 measured by the nanoindentation method is preferably 1.0 or less, more preferably 0.95 or less. Such a configuration is suitable for ensuring the flexibility of the antifouling layer 14 and therefore suitable for ensuring the flexibility of the optical film F. Methods for adjusting the elastic recovery rate R of the antifouling layer 14 include, for example, adjusting the hardness and elastic modulus of the hard coat layer 12, and adjusting the hardness and elastic modulus of the underlying layer for the antifouling layer 14. adjustments are included.

The product of the surface hardness H (GPa) and the elastic recovery rate R in the antifouling layer 14 is preferably 0.8 or more, more preferably 0.9 or more, still more preferably 1.0 or more, and particularly preferably 1.1. That's it. Such a configuration is suitable for suppressing deterioration of the antifouling property of the antifouling layer 14 against wiping operation on the antifouling layer 14 . The product of the surface hardness H (GPa) and the elastic recovery rate R in the antifouling layer 14 is preferably 2.0 or less, more preferably 1.7 or less, and even more preferably 1.5 or less. Such a configuration is suitable for ensuring the flexibility of the antifouling layer 14 and therefore suitable for ensuring the flexibility of the optical film F.

The water contact angle (pure water contact angle) of the surface 14a of the antifouling layer 14 is preferably 110° or more, preferably 111° or more, more preferably 112° or more, still more preferably 113° or more, and particularly preferably 114° or more. A configuration in which the water contact angle on the surface 14 a is as high as this is suitable for achieving high antifouling properties in the antifouling layer 14 . The water contact angle is, for example, 130° or less. The water contact angle is obtained by forming a water droplet (pure water droplet) with a diameter of 2 mm or less on the surface 14a (exposed surface) of the antifouling layer 14 and measuring the contact angle of the water droplet with respect to the surface 14a. . The water contact angle of the surface 14a can be adjusted, for example, by adjusting the composition of the antifouling layer 14, the roughness of the surface 14a, the composition of the hard coat layer 12, and the roughness of the surface of the hard coat layer 12 on the antifouling layer 14 side. , can be adjusted.

The thickness of the antifouling layer 14 is preferably 1 nm or more, more preferably 3 nm or more, even more preferably 5 nm or more, and particularly preferably 7 nm or more. Such a configuration is suitable for achieving the above surface hardness in the antifouling layer 14 . The thickness of the antifouling layer 14 is preferably 25 nm or less, more preferably 20 nm or less, still more preferably 18 nm or less. Such a configuration is suitable for achieving the above water contact angle in the antifouling layer 14 .

The optical film F is produced by preparing the transparent base material 11 and then sequentially forming the hard coat layer 12, the adhesion layer 15, and the antifouling layer 14 on the transparent base material 11 by, for example, a roll-to-roll method. can.

The hard coat layer 12 can be formed, for example, by coating a curable resin composition on the transparent substrate 11 to form a coating film and then curing the coating film. When the curable resin composition contains an ultraviolet-curable resin, the coating film is cured by ultraviolet irradiation. When the curable resin composition contains a thermosetting resin, the coating is cured by heating.

The exposed surface of the hard coat layer 12 formed on the transparent substrate 11 is subjected to a surface modification treatment as necessary. When plasma processing is performed as surface modification processing, argon gas, for example, is used as an inert gas. Also, the discharge power in the plasma treatment is, for example, 10 W or more and, for example, 10000 W or less.

The inorganic oxide underlayer 13 is formed by depositing a material using a dry coating method. Dry coating methods include sputtering, vacuum deposition, and CVD, with sputtering being preferred.

In the sputtering method, a negative voltage is applied to a target placed on a cathode while gas is introduced into the sputtering chamber under vacuum conditions. As a result, glow discharge is generated to ionize the gas atoms, and the gas ions collide with the target surface at high speed, ejecting the target material from the target surface and depositing the ejected target material on a predetermined surface. Reactive sputtering is preferable as the sputtering method from the viewpoint of film formation rate. In reactive sputtering, a metal target is used as the target, and a mixed gas of an inert gas such as argon and oxygen (reactive gas) is used as the above gas. By adjusting the flow rate ratio (sccm) between the inert gas and oxygen, the proportion of oxygen contained in the inorganic oxide to be deposited can be adjusted.

Power sources for carrying out the sputtering method include, for example, DC power sources, AC power sources, RF power sources, and MFAC power sources (AC power sources with a frequency band of several kHz to several MHz). The discharge voltage in the sputtering method is, for example, 200 V or higher and, for example, 1000 V or lower. Also, the film forming pressure in the sputtering chamber where the sputtering method is performed is preferably 0.01 Pa or higher, more preferably 0.05 Pa or higher, and still more preferably 0.1 Pa or higher. Such a configuration is preferable from the viewpoint of forming the antifouling layer 14 in which the material is densely deposited. Also, the film formation pressure is, for example, 2 Pa or less from the viewpoint of discharge stability.

The antifouling layer 14 is formed on the inorganic oxide base layer 13 by forming a film of, for example, a fluorine group-containing organic compound by a dry coating method. Dry coating methods include, for example, a vacuum deposition method, a sputtering method, and a CVD method, and preferably a vacuum deposition method is used.

For example, the optical film F can be manufactured as described above. The optical film F is used with the transparent substrate 11 side attached to an adherend via, for example, an adhesive. Examples of the adherend include a transparent cover arranged on the image display side of a display such as a touch panel display.

The optical film F is a dry coating film in which the antifouling layer 14 is arranged on the inorganic oxide underlayer 13 as described above. Such a configuration is suitable for ensuring high bonding strength of the antifouling layer 14 in the optical film F, and therefore suitable for ensuring the peeling resistance of the antifouling layer 14 . The high antifouling property of the antifouling layer 14 helps maintain the antifouling function of the antifouling layer 14 .

In the optical film F, the surface hardness H of the surface 14a of the antifouling layer 14 (the surface of the antifouling layer 14 opposite to the inorganic oxide underlayer 13) measured by the nanoindentation method at 25°C was As described above, it is 1.05 GPa or more, preferably 1.1 GPa or more, more preferably 1.15 GPa or more, still more preferably 1.2 GPa or more, even more preferably 1.25 GPa or more, and particularly preferably 1.3 GPa. That's it. Such a configuration is suitable for suppressing deterioration of the antifouling property of the antifouling layer 14 against wiping operation on the antifouling layer 14 .

In addition, in the optical film F, the elastic recovery rate R at 25° C. of the surface 14a of the antifouling layer 14 measured by the nanoindentation method is preferably 0.76 or more, more preferably 0.76 or more, as described above. It is 0.80 or more, more preferably 0.815 or more, and particularly preferably 0.85 or more. Such a configuration is suitable for suppressing deterioration of the antifouling property of the antifouling layer 14 against wiping operation on the antifouling layer 14 .

In addition, in the optical film F, the product of the surface hardness H and the elastic recovery rate R in the antifouling layer 14 is preferably 0.8 or more, more preferably 0.9 or more, and still more preferably 0.9 or more, as described above. 1.0 or more, particularly preferably 1.1 or more. Such a configuration is suitable for suppressing deterioration of the antifouling property of the antifouling layer 14 against wiping operation on the antifouling layer 14 .

As described above, the optical film F is suitable for suppressing deterioration of the antifouling property while ensuring the peeling resistance of the antifouling layer 14 .

The optical film F may include a layer having a predetermined optical function (optical function layer). When the optical functional layer includes a plurality of layers, it is preferable that the layer of the optical functional layer on the antifouling layer 14 side also serves as the inorganic oxide underlayer 13 described above.

FIG. 2 shows a case where the optical film F has an optical functional layer 20 between the adhesion layer 15 and the antifouling layer 14 . The optical function layer 20 has a layer that also serves as the inorganic oxide base layer 13 on the antifouling layer 14 side surface, as will be described later.

The optical function layer 20 is arranged on one surface in the thickness direction T of the adhesion layer 15 . In this modified example, the optical function layer 20 is an antireflection layer for suppressing the reflection intensity of external light. That is, the optical film F is an antireflection film with an antifouling layer in this modified example.

The optical function layer 20 (antireflection layer) has high refractive index layers with relatively high refractive index and low refractive index layers with relatively low refractive index alternately in the thickness direction. In the antireflection layer, the net reflected light intensity is attenuated by interference between reflected light at multiple interfaces in multiple thin layers (high refractive index layer, low refractive index layer) included in the same layer. Further, in the antireflection layer, by adjusting the optical film thickness (the product of the refractive index and the thickness) of each thin layer, it is possible to develop an interference effect that attenuates the intensity of the reflected light. Specifically, in this embodiment, the optical function layer 20 as such an antireflection layer includes a first high refractive index layer 21, a first low refractive index layer 22, a second high refractive index layer 23, A second low refractive index layer 24 that also serves as the above-mentioned inorganic oxide underlayer 13 is provided in this order toward one side in the thickness direction T. As shown in FIG.

Each of the first high refractive index layer 21 and the second high refractive index layer 23 is made of a high refractive index material having a refractive index of preferably 1.9 or more at a wavelength of 550 nm. From the viewpoint of achieving both a high refractive index and low absorption of visible light, examples of high refractive index materials include niobium oxide (Nb ₂ O ₅ ), titanium oxide, zirconium oxide, tin-doped indium oxide (ITO), and antimony. Doped tin oxide (ATO) is mentioned, preferably niobium oxide is used.

The optical film thickness (product of refractive index and thickness) of the first high refractive index layer 21 is, for example, 20 nm or more, and is, for example, 55 nm or less. The optical film thickness of the second high refractive index layer 23 is, for example, 60 nm or more and is, for example, 330 nm or less.

Each of the first low refractive index layer 22 and the second low refractive index layer 24 is made of a low refractive index material having a refractive index of preferably 1.6 or less at a wavelength of 550 nm. From the viewpoint of achieving both a low refractive index and low absorption of visible light, low refractive index materials include, for example, silicon dioxide (SiO ₂ ) and magnesium fluoride, preferably silicon dioxide. SiO ₂ and magnesium fluoride are also preferred materials for the inorganic oxide underlayer 13, as described above.

The optical film thickness of the first low refractive index layer 22 is, for example, 15 nm or more and is, for example, 70 nm or less. The optical film thickness of the second low refractive index layer 24 is, for example, 100 nm or more and, for example, 160 nm or less.

The first high refractive index layer 21, the first low refractive index layer 22, and the second high refractive index layer 23 can each be formed by depositing materials using a dry coating method. The second low refractive index layer 24, which also serves as the inorganic oxide underlayer 13, is formed by depositing a material using a dry coating method. Dry coating methods include sputtering, vacuum deposition, and CVD, with sputtering being preferred. As the sputtering method, reactive sputtering is preferable from the viewpoint of film formation speed. The conditions of the sputtering method are the same as those described above as the conditions of the sputtering method for forming the inorganic oxide underlayer 13 .

In the optical film F shown in FIG. 2, the antifouling layer 14 is a dry coating film arranged on the second low refractive index layer 24 (inorganic oxide underlayer 13). In the optical film F shown in FIG. 2, the hardness (surface hardness H) of the surface 14a of the antifouling layer 14 at 25° C. measured by the nanoindentation method is 1.05 GPa or more, preferably 1.1 GPa. Above, it is more preferably 1.15 GPa or more, still more preferably 1.2 GPa or more, even more preferably 1.25 GPa or more, and particularly preferably 1.3 GPa or more. In the optical film F shown in FIG. 2, the elastic recovery rate (elastic recovery rate R) of the surface 14a of the antifouling layer 14 at 25° C. measured by the nanoindentation method is preferably 0.76 or more, more preferably. is 0.80 or more, more preferably 0.815 or more, and particularly preferably 0.85 or more. In the optical film F shown in FIG. 2, the product of the surface hardness H (GPa) and the elastic recovery rate R in the antifouling layer 14 is preferably 0.8 or more, more preferably 0.9 or more, and still more preferably 1.5. 0 or more, particularly preferably 1.1 or more. Such an optical film F is suitable for suppressing deterioration of the antifouling property while ensuring peeling resistance in the antifouling layer 14 .

EXAMPLES The present invention will be specifically described below with reference to Examples. The invention is not limited to the examples. In addition, the specific numerical values such as the compounding amount (content), physical property values, parameters, etc. described below are the corresponding compounding amounts ( content), physical properties, parameters, etc. The upper limit (value defined as “less than” or “less than”) or lower limit (value defined as “greater than” or “exceeding”) can be substituted.

[Example 1]
First, a hard coat layer was formed on one side of a polyethylene terephthalate (PET) film (trade name “50U48”, thickness 50 μm, manufactured by Toray Industries, Inc.) as a transparent substrate (hard coat layer forming step). Specifically, first, a mixture of UV-curable monomers and oligomers (containing urethane acrylate as a main component) in a butyl acetate solution (trade name “Unidic 17-806”, solid content concentration 80% by mass, manufactured by DIC Corporation) ) 100 parts by mass (in terms of solid content), a photopolymerization initiator (trade name “IRGACURE906”, manufactured by BASF) 5 parts by mass, and a leveling agent (trade name “GRANDICPC4100”, manufactured by DIC) 0.01 parts by mass were mixed to obtain a mixture. Next, a mixed solvent of cyclopentanone (CPN) and propylene glycol monomethyl ether (PGM) (the mass ratio of CPN and PGM is 45:55) was added to adjust the solid content concentration of the mixed liquid to 36%. Thus, an ultraviolet curable resin composition (varnish) was prepared. Next, the resin composition was applied to one side of the PET film to form a coating film. Next, this coating film was dried by heating and then cured by UV irradiation. The heating temperature was 90° C. and the heating time was 60 seconds. In the ultraviolet irradiation, a high-pressure mercury lamp was used as a light source, ultraviolet rays with a wavelength of 365 nm were used, and the cumulative irradiation light amount was 300 mJ/cm ² . As a result, a hard coat layer (HC) having a thickness of 5 μm was formed on the PET film.

Next, the HC layer surface of the HC layer-attached PET film was plasma-treated under a vacuum atmosphere of 1.0 Pa using a roll-to-roll type plasma treatment apparatus. In this plasma treatment, argon gas was used as an inert gas, and the discharge power was 780W.

Next, an adhesion layer and an inorganic oxide base layer were sequentially formed on the HC layer of the HC layer-attached PET film after the plasma treatment (sputter film formation step). Specifically, an indium tin oxide (ITO) layer having a thickness of 2.0 nm as an adhesion layer and an inorganic oxide layer were formed on the HC layer of the HC layer-attached PET film by a roll-to-roll type sputtering deposition apparatus. A SiO ₂ layer with a thickness of 165 nm as an underlayer was sequentially formed. In the formation of the adhesion layer, an ITO target was used, argon gas as an inert gas, oxygen gas as a reactive gas of 10 parts by volume with respect to 100 parts by volume of argon gas, and a discharge voltage of 350 V were used. The pressure in the film chamber (film formation pressure) was set to 0.4 Pa, and the ITO layer was formed by MFAC sputtering. In the formation of the inorganic oxide underlayer, a Si target is used, 100 parts by volume of argon gas and 30 parts by volume of oxygen gas are used, the discharge voltage is 350 V, the film formation pressure is 0.3 Pa, and MFAC sputtering is performed to form SiO ₂ formed a layer.

Next, an antifouling layer was formed (antifouling layer forming step). Specifically, an antifouling layer having a thickness of 12 nm was formed on the inorganic oxide underlayer by a vacuum deposition method using an alkoxysilane compound containing a perfluoropolyether group as a deposition source. The vapor deposition source is a solid content obtained by drying "KY1903-1" (perfluoropolyether group-containing alkoxysilane compound, solid content concentration 20% by mass) manufactured by Shin-Etsu Chemical Co., Ltd. Moreover, the heating temperature of the vapor deposition source in the vacuum vapor deposition method was set to 260.degree.

The optical film of Example 1 was produced as described above. In the optical film of Example 1, a transparent substrate (resin film), a hard coat layer, an adhesion layer, an inorganic oxide base layer, and an antifouling layer are arranged in this order toward one side in the thickness direction. Prepare.

[Example 2]
An optical film of Example 2 was produced in the same manner as the optical film of Example 1, except that the thickness of the HC layer was changed from 5 μm to 10 μm.

[Example 3]
The optical film of Example 3 was prepared in the same manner as the optical film of Example 1, except that the thickness of the HC layer was changed to 10 µm instead of 5 µm, and the thickness of the inorganic oxide underlayer was changed to 100 nm instead of 165 nm. A film was produced.

[Example 4]
An optical film of Example 4 was produced in the same manner as the optical film of Example 1, except that the film formation pressure during formation of the inorganic oxide underlayer was changed from 0.3 Pa to 0.1 Pa.

[Example 5]
The same as the optical film of Example 1, except that the thickness of the HC layer was changed from 5 µm to 10 µm, and the film formation pressure during formation of the inorganic oxide underlayer was changed from 0.3 Pa to 0.1 Pa. Then, an optical film of Example 5 was produced.

[Example 6]
An optical film of Example 6 was produced in the same manner as the optical film of Example 1, except that the thickness of the antifouling layer was changed from 12 nm to 8 nm.

[Example 7]
An optical film of Example 7 was produced in the same manner as the optical film of Example 1, except that the thickness of the antifouling layer was changed from 12 nm to 6 nm.

[Example 8]
An optical film of Example 8 was produced in the same manner as the optical film of Example 1, except that the thickness of the antifouling layer was changed from 12 nm to 16 nm.

[Example 9]
First, a hard coat layer was formed on one side of a PET film (trade name “50U48”, thickness 50 μm, manufactured by Toray Industries, Inc.) as a transparent substrate. Specifically, first, UV-curable multifunctional acrylate resin (trade name “Z-850-50H-D”, solid content concentration 44% by mass, manufactured by Aica Kogyo Co., Ltd.) 100 parts by mass (solid content conversion), light 4 parts by mass of a polymerization initiator (trade name “OMNIRAD2959”, manufactured by BASF) and 0.05 parts by mass of a leveling agent (trade name “LE-303”, manufactured by Kyoeisha Chemical Co., Ltd.) are mixed to obtain a mixed solution. rice field. Next, by adding methyl isobutyl ketone to this mixed liquid, the solid content concentration of the mixed liquid was adjusted to 40%. Thus, an ultraviolet curable resin composition (varnish) was prepared. Next, the resin composition was applied to one side of the PET film to form a coating film. Next, this coating film was dried by heating and then cured by UV irradiation. The heating temperature was 80° C. and the heating time was 60 seconds. In the ultraviolet irradiation, a high-pressure mercury lamp was used as a light source, ultraviolet rays with a wavelength of 365 nm were used, and the cumulative irradiation light amount was 300 mJ/cm ² . As a result, a hard coat layer (HC) having a thickness of 5 μm was formed on the PET film.

Next, the HC layer surface of the HC layer-attached PET film was plasma-treated under a vacuum atmosphere of 1.0 Pa using a roll-to-roll type plasma treatment apparatus. In this plasma treatment, argon gas was used as an inert gas, and the discharge power was set to 150W.

Next, an adhesion layer and an antireflection layer were sequentially formed on the HC layer of the HC layer-attached PET film after the plasma treatment. Specifically, an indium tin oxide (ITO) layer having a thickness of 1.5 nm was formed as an adhesion layer on the HC layer of the HC layer-attached PET film after the plasma treatment using a roll-to-roll type sputtering deposition apparatus. , a 12 nm thick Nb ₂ O ₅ layer as the first high refractive index layer, a 28 nm thick SiO ₂ layer as the first low refractive index layer, and a 100 nm thick Nb layer as the second high refractive index layer. _{A 2} O ₅ layer and a 85 nm thick SiO ₂ layer as a second low refractive index layer were sequentially formed. In the formation of the adhesion layer, an ITO target was used, argon gas was used as an inert gas, oxygen gas was used as a reactive gas in an amount of 10 parts by volume with respect to 100 parts by volume of argon gas, and the discharge voltage was set to 400 V. The pressure in the film chamber (film formation pressure) was set to 0.2 Pa, and the ITO layer was formed by MFAC sputtering. In the formation of the first high refractive index layer, a Nb target is used, 100 parts by volume of argon gas and 5 parts by volume of oxygen gas are used, the discharge voltage is 415 V, the film formation pressure is 0.7 Pa, and the Nb target is formed by MFAC sputtering. ₂ O ₅ layers were deposited. In the formation of the first low refractive index layer, a Si target is used, 100 parts by volume of argon gas and 30 parts by volume of oxygen gas are used, the discharge voltage is 350 V, the film formation pressure is 0.7 Pa, and MFAC sputtering is performed to form SiO. _Two layers were deposited. In the formation of the second high refractive index layer, a Nb target is used, 100 parts by volume of argon gas and 13 parts by volume of oxygen gas are used, the discharge voltage is 460 V, the film formation pressure is 0.7 Pa, and the Nb target is formed by MFAC sputtering. ₂ O ₅ layers were deposited. In the formation of the second low refractive index layer, a Si target is used, 100 parts by volume of argon gas and 30 parts by volume of oxygen gas are used, the discharge voltage is 340 V, the film formation pressure is 0.7 Pa, and MFAC sputtering is performed to form SiO. _Two layers were deposited. As described above, antireflection layers (first high refractive index layer, first low refractive index layer, second high refractive index layer, second low refractive index layer) was laminated. In this example, the second low refractive index layer is the inorganic oxide base layer for the antifouling layer.

Next, an antifouling layer was formed on the formed antireflection layer (that is, on the second low refractive index layer). Specifically, it is the same as the antifouling layer forming step in Example 1.

An optical film of Example 9 was produced as described above. The optical film of Example 9 comprises a transparent substrate (resin film), a hard coat layer, an adhesion layer, an antireflection layer (including a second low refractive index layer that is an inorganic oxide underlayer), and an antifouling layer. and layers in this order toward one side in the thickness direction.

[Comparative Example 1]
The thickness of the HC layer was changed to 10 μm instead of 5 μm, and the thickness of the inorganic oxide underlayer was changed to 30 nm instead of 165 nm. An optical film was produced.

<Hardness and elastic recovery rate of antifouling layer surface>
The surface of the antifouling layer of each of the optical films of Examples 1 to 9 and Comparative Example 1 was subjected to load-displacement measurement by a nanoindentation method. Specifically, first, a measurement sample (5 mm×5 mm) was cut out from the optical film. Next, using a nanoindenter (trade name “Triboindenter”, manufactured by Hysitron), the load-displacement measurement of the antifouling layer surface of the measurement sample was performed according to ISO14577 to obtain a load-displacement curve. In this measurement, the measurement mode is single indentation measurement, the measurement temperature is 25°C, the indenter used is a Berkovich (triangular pyramid) type diamond indenter, and the maximum indentation depth (maximum The displacement H1) was set to 200 nm, the pressing speed of the indenter was set to 20 nm/sec, and the withdrawal speed of the indenter from the measurement sample during the unloading process was set to 20 nm/sec. Based on the obtained load-displacement curve, the maximum load Pmax (the load acting on the indenter at the maximum displacement H1), the projected contact area Ap (the projected area of the contact area between the indenter and the sample at the maximum load), and , the amount of plastic deformation H2 on the sample surface after the unloading process (the depth of the concave portion maintained on the sample surface after the indenter is released from the sample surface) was obtained. Then, the surface hardness (=Pmax/Ap) of the antifouling layer was calculated from the maximum load Pmax and the projected contact area Ap. Also, from the maximum displacement H1 and the amount of plastic deformation H2, the elastic recovery rate (=(H1-H2)/H1) of the surface of the antifouling layer after applying a load and then unloading was calculated. Table 1 shows these surface hardness (GPa) and elastic recovery rate .

<Water contact angle>
For each of the optical films of Examples 1 to 9 and Comparative Example 1, the contact angle of water on the antifouling layer surface was examined. First, about 1 μL of pure water was dropped on the surface of the antifouling layer of the optical film to form water droplets. Next, the angle formed by the surface of the water droplet on the surface of the antifouling layer and the surface of the antifouling layer was measured. A contact angle meter (trade name “DMo-501”, manufactured by Kyowa Interface Science Co., Ltd.) was used for the measurement. The measurement results are shown in Table 1 as the initial water contact angle θ ₀ .

<Eraser sliding test>
For each of the optical films of Examples 1 to 9 and Comparative Example 1, the degree of deterioration of the antifouling property of the surface of the antifouling layer due to an eraser sliding test was examined. Specifically, first, a sliding test was performed in which an eraser was slid and reciprocated on the surface of the antifouling layer of the optical film (first eraser sliding test). In this test, an eraser (Φ6 mm) manufactured by Minoan was used, the load of the eraser on the antifouling layer surface was 1 kg/6 mmΦ, and the sliding distance of the eraser on the antifouling layer surface (one way in reciprocating motion) was 20 mm. , the eraser was slid at a speed of 40 rpm, and the eraser was reciprocated 3000 times with respect to the antifouling layer surface. Next, the water contact angle of the eraser-sliding portion on the surface of the antifouling layer of the optical film was measured by the same method as that for measuring the initial water contact angle θ ₀ . The measurement results are shown in Table 1 as the water contact angle θ ₁ after the first eraser sliding test.

Next, a sliding test was conducted in which an eraser was further slid and reciprocated on the surface of the antifouling layer of the optical film (second eraser sliding test). The sliding conditions were the same as in the first eraser sliding test (the number of times the eraser was reciprocated was 6000 reciprocations in total for the first eraser sliding test and the subsequent second eraser sliding test). ). Next, the water contact angle of the eraser-sliding portion on the surface of the antifouling layer of the optical film was measured by the same method as that for measuring the initial water contact angle θ ₀ . The measurement results are shown in Table 1 as the water contact angle _θ2 after the second eraser sliding test. FIG. 3 is a graph plotting the surface hardness H and the water contact angle θ ₂ of each optical film of Examples 1 to 9 and Comparative Example 1. FIG. In the graph of FIG. 3, the horizontal axis represents the surface hardness H (GPa), and the vertical axis represents the water contact angle θ ₂ (°). In FIG. 3, plots E1 to E9 represent the measurement results for Examples 1 to 9, and plot C1 represents the measurement results for Comparative Example 1.

<evaluation>
In each of the optical films of Examples 1 to 9, compared with the optical film of Comparative Example 1, the antifouling layer by passing through the eraser sliding test (first eraser sliding test, second eraser sliding test) The degree of decrease in water contact angle on the surface is significantly smaller, and therefore the decrease in antifouling property is significantly smaller (on the surface of the antifouling layer, the smaller the decrease in water contact angle, the smaller the decrease in antifouling property).

The above-described embodiments are examples of the present invention, and the present invention should not be construed as being limited by the embodiments. Variations of the invention that are obvious to those skilled in the art are included in the following claims.

The optical film with an antifouling layer of the present invention can be applied to, for example, an antireflection film with an antifouling layer, a transparent conductive film with an antifouling layer, and an electromagnetic shielding film with an antifouling layer.

F Optical film (optical film with antifouling layer)
11 transparent substrate 12 hard coat layer 13 inorganic oxide base layer 14 antifouling layer 14a surface 15 adhesion layer 20 optical function layer 21 first high refractive index layer 22 first low refractive index layer 23 second high refractive index layer 24 second 2 Low refractive index layer

Claims (6)

comprising a transparent substrate, a hard coat layer, an inorganic oxide base layer, and an antifouling layer in this order,
wherein the inorganic oxide underlayer comprises silicon dioxide;
The antifouling layer is a vacuum deposition film of a perfluoropolyether group-containing alkoxysilane compound disposed on the inorganic oxide underlayer, and has a thickness of 7 nm or more,
The perfluoropolyether group-containing alkoxysilane compound is a compound represented by the following general formula (1),
R ¹ -R ² -X-(CH ₂ ) _m -Si(OR ³ ) ₃ (1)
In general formula (1), R ¹ represents a perfluoroalkyl group, and R ² represents a perfluoropolyether group repeating structure containing —(OCF ₂ ) _p — and —(OC ₂ F ₄ ) _p —. , p represents an integer of 1 to 50, R ³ represents an alkyl group having 1 to 4 carbon atoms, X represents an ether group, a carbonyl group, an amino group, or an amide group, and m is an integer of 1 or more. represents
An optical film with an antifouling layer, wherein the surface of the antifouling layer opposite to the inorganic oxide underlayer has a hardness of 1.05 GPa or more at 25° C. measured by a nanoindentation method. comprising a transparent substrate, a hard coat layer, an inorganic oxide base layer, and an antifouling layer in this order,
wherein the inorganic oxide underlayer comprises silicon dioxide;
The antifouling layer is a vacuum deposition film of a perfluoropolyether group-containing alkoxysilane compound disposed on the inorganic oxide underlayer,
The perfluoropolyether group-containing alkoxysilane compound is a compound represented by the following general formula (1),
R ¹ -R ² -X-(CH ₂ ) _m -Si(OR ³ ) ₃ (1)
In general formula (1), R ¹ represents a perfluoroalkyl group, and R ² represents a perfluoropolyether group repeating structure containing —(OCF ₂ ) _p — and —(OC ₂ F ₄ ) _p —. , p represents an integer of 1 to 50, R ³ represents an alkyl group having 1 to 4 carbon atoms, X represents an ether group, a carbonyl group, an amino group, or an amide group, and m is an integer of 1 or more. represents
The surface of the antifouling layer opposite to the inorganic oxide underlayer has a hardness at 25°C measured by a nanoindentation method of 1.05 GPa or more;
An optical film with an antifouling layer, wherein the product of the elastic recovery rate at 25° C. measured by a nanoindentation method and the hardness (GPa) of the surface of the antifouling layer is 0.8 or more. 3. The optical film with an antifouling layer according to claim 1, wherein the surface of the antifouling layer has an elastic recovery rate of 0.76 or more at 25[deg.] C. measured by a nanoindentation method. The optical film with an antifouling layer according to any one of claims 1 to 3, wherein the antifouling layer has a thickness of 25 nm or less. The optical film with an antifouling layer according to any one of claims 1 to 4, wherein the inorganic oxide underlayer has a thickness of more than 100 nm. The optical film with an antifouling layer according to any one of claims 1 to 5, wherein the hard coat layer has a thickness of 1 µm or more and 50 µm or less.

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