TW202215073A - Antifouling layer-equipped optical film - Google Patents

Abstract

The antifouling layer-equipped optical film (F) according to the present invention is provided with a transparent base material (11), a hard coat layer (12), an inorganic oxide foundation layer (13), and an antifouling layer (14) in this order. The antifouling layer (14) is a dry coating membrane disposed on the inorganic oxide foundation layer (13). The elastic recovery measured by a nano-indentation method at a temperature of 25 DEG C and a maximum indentation depth of 200 nm in a surface (14a) on the opposite side of the inorganic oxide foundation layer (13) in the antifouling layer (14) is 76% or more.

Description

Optical film with antifouling layer

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

In order to achieve antifouling properties, for example, an optical film with an antifouling layer is attached to the outer surface on the image display side of a display such as a touch panel display. The optical film with an antifouling layer includes a transparent substrate and an antifouling layer disposed on the outermost surface of one surface side of the transparent substrate. The antifouling layer prevents contaminants such as hand grease from adhering to the display surface, and makes it easy to remove the adhering contaminants. For example, Patent Document 1 below discloses a technique related to such an antifouling layer-attached optical film. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2020-52221

[Problems to be Solved by Invention]

When an optical film with an antifouling layer is used, the contaminants attached to the antifouling layer are removed, for example, by wiping. However, the repeated wiping operation of the antifouling layer causes the antifouling property of the antifouling layer to decrease, and also causes the antifouling layer to peel off. In order to maintain the antifouling function of the antifouling layer-attached optical film, it is not desirable to reduce the antifouling properties of the antifouling layer and to peel off the antifouling layer.

The present invention provides an antifouling layer-attached optical film suitable for ensuring the peeling resistance of the antifouling layer and suppressing the deterioration of the antifouling property. [Technical means to solve problems]

The present invention [1] includes an optical film with an antifouling layer, which comprises a transparent substrate, a hard coat layer, an inorganic oxide base layer and an antifouling layer in sequence, and the antifouling layer is disposed on the inorganic oxide base layer The above dry coating film was measured at a temperature of 25°C and a maximum indentation depth of 200 nm by nanoindentation method. The elastic recovery of the surface of the antifouling layer on the opposite side to the inorganic oxide base layer was measured. The rate is over 76%.

The present invention [2] includes the antifouling layer-attached optical film according to the above [1], wherein the antifouling layer has a thickness of 1 nm or more and 25 nm or less.

The present invention [3] includes the optical film with an antifouling layer according to the above [1] or [2], wherein the inorganic oxide base layer contains silicon dioxide.

The present invention [4] includes the antifouling layer-attached optical film according to any one of the above [1] to [3], wherein the inorganic oxide base layer has a thickness of 50 nm or more.

The present invention [5] includes the antifouling layer-attached optical film according to any one of the above [1] to [4], wherein the hard coat layer has a thickness of 1 μm or more and 50 μm or less. [Effect of invention]

As described above, the optical film with antifouling layer of the present invention is a dry coating film in which the antifouling layer is disposed on the inorganic oxide base layer. Such a configuration is suitable for ensuring that the antifouling layer of the antifouling layer-attached optical film has a high bonding force, and therefore, is suitable for ensuring the peeling resistance of the antifouling layer. In addition, in the optical film with the antifouling layer, under the conditions of the temperature of 25°C and the maximum indentation depth of 200 nm, the surface of the antifouling layer on the opposite side to the inorganic oxide base layer was measured by the nanoindentation method. The elastic recovery rate is above 76%. Such a configuration is suitable for resisting the influence of the wiping operation of the antifouling layer, and suppressing the deterioration of the antifouling property of the antifouling layer.

As shown in FIG. 1 , as an embodiment of the optical film with antifouling layer of the present invention, the optical film F includes a transparent substrate 11 , a hard coat layer 12 , and an inorganic oxide base layer in this order toward one side in the thickness direction T 13 and antifouling layer 14. In the present embodiment, the optical film F includes a transparent substrate 11 , a hard coat layer 12 , an adhesive layer 15 , an inorganic oxide base layer 13 , and an antifouling layer 14 in this order toward one side in the thickness direction T. As shown in FIG. Moreover, the optical film F has the shape which spreads in the direction (plane direction) orthogonal to the thickness direction T.

The transparent substrate 11 is a flexible transparent resin film. As the material of the transparent substrate 11, for example, polyester resin, polyolefin resin, polystyrene resin, acrylic resin, polycarbonate resin, polyether resin, polyamide resin, polyamide resin, polyamide resin can be mentioned. Amine resin, cellulose resin, norbornene resin, polyarylate resin and polyvinyl alcohol resin. As polyester resin, polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate are mentioned, for example. As a polyolefin resin, polyethylene, a polypropylene, and a cycloolefin polymer (COP) are mentioned, for example. As a cellulose resin, triacetyl cellulose (TAC) is mentioned, for example. These materials may be used alone or in combination of two or more. As the material of the transparent base material 11, from the viewpoint of transparency and strength, one selected from the group consisting of polyester resin, polyolefin resin, and cellulose resin can be used, and it is more preferable to use one selected from PET, One of the groups consisting of COP and TAC.

Surface modification treatment may also be performed on the side surface of the hard coat layer 12 of the transparent substrate 11 . As the surface modification treatment, for example, corona treatment, plasma treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment may be mentioned.

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 still more preferably 20 μm or more. From the viewpoint of workability, the thickness of the transparent base material 11 is preferably 300 μm or less, and more preferably 200 μm or less.

The total light transmittance (JIS K 7375-2008) of the transparent substrate 11 is preferably 80% or more, more preferably 90% or more, and still more preferably 95% or more. When the optical film F is provided on the surface of a display such as a touch panel display, such a configuration is suitable for ensuring the transparency required for the optical film F. 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 used to make the exposed surface (the upper surface in FIG. 1 ) of the optical film F difficult to form scratches.

The hard coat layer 12 is a cured product of the curable resin composition. Examples of the curable resin contained in the curable resin composition include polyester resins, acrylic resins, urethane resins, urethane acrylate resins, amide resins, polysiloxane resins, cyclic resins Oxygen resin, and melamine resin. These curable resins may be used alone or in combination of two or more. From the viewpoint of securing high hardness of the hard coat layer 12, it is preferable to use a urethane acrylate resin as the curable resin.

Moreover, as a curable resin composition, an ultraviolet curable resin composition and a thermosetting resin composition are mentioned, for example. As a curable resin composition, it is preferable to use an ultraviolet curable resin composition, and since it can harden|cure without high temperature heating, it contributes to the improvement of the manufacturing efficiency of the optical film F. The UV-curable resin composition includes at least one selected from the group consisting of UV-curable monomers, UV-curable oligomers, and UV-curable polymers. As a specific example of an ultraviolet curable resin composition, the composition for hard-coat layer formation described in Unexamined-Japanese-Patent No. 2016-179686 is mentioned.

The curable resin composition may contain fine particles. The preparation of fine particles in the curable resin composition helps to adjust the hardness, surface roughness, and refractive index of the hard coat layer 12 , and to impart anti-glare properties to the hard coat layer 12 . As the fine particles, for example, metal oxide particles, glass particles, and organic particles may be mentioned. As the material of the metal oxide particles, for example, silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide can be mentioned. As a material of an organic particle, polymethyl methacrylate, polystyrene, polyurethane, acrylic resin-styrene copolymer, benzoguanamine, melamine, and polycarbonate are mentioned, for example.

In order to ensure the hardness of the hard coat layer 12 and thus the hardness of the surface of the antifouling layer 14, the thickness of the hard coat layer 12 is preferably 1 μm or more, more preferably 3 μm or more, and more preferably 5 μm or more. From the viewpoint of securing 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.

Surface modification treatment may also be performed on the side surface of the adhesive layer 15 of the hard coat layer 12 . As the surface modification treatment, for example, plasma treatment, corona treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment may be mentioned. In order to ensure high adhesion between the hard coat layer 12 and the adhesive layer 15 , it is preferable to perform plasma treatment on the side surface of the adhesive layer 15 of the hard coat layer 12 .

The adhesion layer 15 is a layer for ensuring the adhesion of the inorganic oxide layer (in this embodiment, the inorganic oxide base layer 13 ) 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 the material of the adhesion layer 15 include metals such as silicon, indium, nickel, chromium, aluminum, tin, gold, silver, platinum, zinc, titanium, tungsten, zirconium, and palladium, and alloys of two or more of these metals. , and oxides of these metals. In order to have both adhesiveness to both the organic layer (specifically, the hard coat layer 12 ) and the inorganic oxide layer (specifically, the inorganic oxide base layer 13 in this embodiment), and the transparency of the adhesive layer 15 As the material of the adhesion layer 15, indium tin oxide (ITO) or silicon oxide (SiOx) is preferably used. When silicon oxide is used as the material of the adhesion layer 15, it is preferable to use SiOx whose oxygen content is less than the stoichiometric composition, and it is more preferable to use SiOx whose x is 1.2 or more and 1.9 or less.

In order to ensure the adhesion between the hard coat layer 12 and the inorganic oxide base layer 13 and to achieve the transparency of the adhesion layer 15, the thickness of the adhesion layer 15 is preferably 1 nm or more and 10 nm or less.

The inorganic oxide base layer 13 is a layer for securing peeling resistance in the antifouling layer 14 . As the material of the inorganic oxide base layer 13 , for example, silicon dioxide (SiO ₂ ) and magnesium fluoride can be exemplified, and silicon dioxide is preferably used.

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

The antifouling layer 14 is a layer having an antifouling function. The antifouling layer 14 is disposed on one surface in the thickness direction T of the inorganic oxide base layer 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 preventing contaminants such as hand grease from adhering to the exposed surface of the film when the optical film F is used, and a function of making the adhered contaminants easily removed.

As the material of the antifouling layer 14, for example, a fluorine group-containing organic compound can be mentioned. As the organic compound containing a fluorine group, an alkoxysilane compound having a perfluoropolyether group is preferably used. As an alkoxysilane compound which has a perfluoropolyether group, the compound represented by following general formula (1) is mentioned, for example.

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

In the general formula (1), R ¹ represents a linear or branched fluorinated alkyl group in which one or more hydrogen atoms in the alkyl group are substituted with a fluorine atom (the number of carbon atoms is, for example, 1 to 20), preferably Represents a perfluoroalkyl group in which all hydrogen atoms of an alkyl group are replaced by fluorine atoms.

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

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. Moreover, m represents an integer which is preferably 20 or less, more preferably 10 or less, and still more preferably 5 or less.

Among the alkoxysilane compounds having such a perfluoropolyether group, those 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 the 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 which has a perfluoropolyether group may be used individually, and may use 2 or more types together.

The antifouling layer 14 is a film (dry coating film) formed by a dry coating method. As a dry coating method, a sputtering method, a vacuum vapor deposition method, and CVD (Chemical Vapor Deposition, chemical vapor deposition) are mentioned. The antifouling layer 14 is preferably a film formed by a vacuum deposition method (vacuum deposition film).

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 evaporation film), which is suitable for ensuring that the antifouling layer 14 is resistant to inorganic substances. The oxide base layer 13 has high bonding force, and thus is suitable for ensuring the peeling resistance of the antifouling layer 14 . The antifouling layer 14 has high peeling resistance, which helps to maintain the antifouling function of the antifouling layer 14 .

Under the conditions of a temperature of 25° C. and a maximum indentation depth of 200 nm, the elastic recovery rate obtained by measuring the surface 14a of the antifouling layer 14 by a nanoindentation method is more than 76%, preferably more than 80%, more preferably 81.5% % or more, more preferably 85% or more. Such a configuration is suitable for resisting the influence of the wiping operation on the antifouling layer 14 and suppressing the deterioration of the antifouling property of the antifouling layer 14 . The elastic recovery ratio of the surface 14a of the antifouling layer 14 is preferably 100% or less, and more preferably 95% or less. Such a configuration is suitable for securing the flexibility of the antifouling layer 14 and, therefore, suitable for securing the flexibility of the optical film F.

Nanoindentation is a technique for measuring various physical properties of samples at the nanoscale. In this embodiment, the nanoindentation is implemented in accordance with ISO14577. In the nanoindentation method, the process of pressing the indenter into the sample set on the platform (load application process), and then the process of pulling out the indenter from the sample (load removal process), in a series of processes, The load acting between the indenter and the sample and the relative displacement of the indenter with respect to the sample were measured (load-displacement measurement). Thereby, a load-displacement curve can be obtained. From this load-displacement curve, various physical properties by nanoscale measurement can be obtained for the measurement sample. For the load-displacement measurement of the surface of the antifouling layer by the nanoindentation method, for example, a nanoindenter (trade name "Triboindenter", manufactured by Hysitron Corporation) can be used. In this measurement, the measurement mode is set to single indentation measurement, the measurement temperature is set to 25°C, the indenter used is a Berkovich (triangular pyramid) type diamond indenter, and the maximum indentation of the indenter to the measurement sample during the load application process The depth (maximum displacement H1) was set to 200 nm, the indentation speed of the indenter was set to 20 nm/sec, and the speed of the indenter pulled out from the measurement sample during the load removal process was 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 contact projected 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 of the sample surface after the load removal process (the depth of the concave part of the sample surface maintained by the indenter after leaving the sample surface). Then, the hardness of the surface of the antifouling layer (=Pmax/Ap) can be calculated according to the maximum load Pmax and the contact projected area Ap. In addition, the elastic recovery rate (=(H1-H2)/H1) of the surface of the antifouling layer after load application and subsequent load removal can be calculated from the maximum displacement H1 and the plastic deformation amount H2.

As a method of adjusting the elastic recovery rate of the surface 14a of the antifouling layer 14, for example, adjusting the hardness and elastic modulus of the hard coat layer 12, and adjusting the hardness and elastic modulus of the inorganic oxide base layer 13 can be exemplified.

The hardness of the surface 14a of the antifouling layer 14 measured by the nanoindentation method at 25°C is preferably 1.05 GPa or more, more preferably 1.1 GPa or more, more preferably 1.15 GPa or more, and more preferably 1.2 GPa The above is more preferably 1.25 GPa or more, particularly preferably 1.3 GPa or more. Such a configuration is suitable for resisting the influence of the wiping operation on the antifouling layer 14 and suppressing the deterioration of the antifouling property of the antifouling layer 14 . The hardness 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 securing the flexibility of the antifouling layer 14 and, therefore, suitable for securing the flexibility of the optical film F. As a method of adjusting the hardness of the surface 14 a of the antifouling layer 14 , for example, adjusting the hardness and thickness of the hard coat layer 12 and adjusting the hardness and thickness of the base layer for the antifouling layer 14 can be exemplified.

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, further preferably 113° or more, especially preferably Above 114°. The constitution that the water contact angle of the surface 14 a is so high is suitable for realizing the high antifouling property of the antifouling layer 14 . The water contact angle is, for example, 130° or less. The water contact angle was obtained by measuring the contact angle of the water droplet with respect to the surface 14a by forming a water droplet (droplet of pure water) with a diameter of 2 mm or less on the surface 14a (exposed surface) of the antifouling layer 14 . For example, the water contact angle of the surface 14a can be adjusted 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 side surface of the antifouling layer 14 of the hard coat layer 12.

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

After preparing the transparent base material 11 , the optical film F can be produced by forming the hard coat layer 12 , the adhesive layer 15 , and the antifouling layer 14 on the transparent base material 11 in this order by, for example, a roll-to-roll method.

For example, after coating a curable resin composition on the transparent base material 11 to form a coating film, the hard coating layer 12 can be formed by curing the coating film. When the curable resin composition contains an ultraviolet ray resin, the above-mentioned coating film is cured by irradiating ultraviolet rays. When the curable resin composition contains a thermosetting resin, the coating film is cured by heating.

The exposed surface of the hard coat layer 12 formed on the transparent substrate 11 is subjected to surface modification treatment as necessary. In the case of performing the plasma treatment as the surface modification treatment, for example, argon gas is used as the inert gas. In addition, the discharge power at the time of plasma treatment is, for example, 10 W or more, and, for example, 10,000 W or less.

The inorganic oxide base layer 13 is formed by forming a film material by a dry coating method. As a dry coating method, a sputtering method, a vacuum vapor deposition method, and CVD are mentioned, Preferably, a sputtering method is used.

In the sputtering method, a gas is introduced into a sputtering chamber under vacuum conditions, and a negative voltage is applied to a target arranged on a cathode. Thereby, a glow discharge is generated, gas atoms are ionized, the gas ions collide with the target surface at a high speed, the target material is ejected from the target surface, and the ejected target material is deposited on a predetermined surface. From the viewpoint of the film-forming speed, reactive sputtering is preferable as the sputtering method. In reactive sputtering, a metal target is used as a target, and a mixed gas of an inert gas such as argon and oxygen (reactive gas) is used as the gas. By adjusting the flow ratio (sccm) of the inert gas and the oxygen gas, the ratio of the oxygen contained in the inorganic oxide of the film can be adjusted.

As a power source for implementing the sputtering method, for example, a DC (Direct Current) power source, an AC (Alternating Current, alternating current) power source, an RF (Radio Frequency, radio frequency) power source, and an MFAC (Medium Frequency Alternating Current) power source can be exemplified. Wave AC) power supply (AC power supply with a frequency band of several kHz to several MHz). The discharge voltage of the sputtering method is, for example, 200 V or more and, for example, 1000 V or less. Moreover, the film-forming pressure in the sputtering chamber in which the sputtering method is performed is preferably 0.01 Pa or more, more preferably 0.05 Pa or more, and still more preferably 0.1 Pa or more. This configuration is suitable for forming the antifouling layer 14 in which the material is densely deposited, so it is preferable. In addition, from the viewpoint of discharge stability, the film-forming gas pressure is, for example, 2 Pa or less.

On the inorganic oxide base layer 13 , a film of an organic compound containing a fluorine group is formed by, for example, a dry coating method, thereby forming an antifouling layer 14 . As a dry coating method, a vacuum vapor deposition method, a sputtering method, and CVD are mentioned, for example, Preferably, a vacuum vapor deposition method is used.

For example, the optical film F can be manufactured as described above. For example, the optical film F is used by bonding the transparent base material 11 side to the adherend via an adhesive. As a to-be-adhered body, the transparent cover arrange|positioned at the image display side of displays, such as a touch panel display, is mentioned, for example.

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

For the optical film F, as described above, the elastic recovery rate obtained by measuring the surface 14a of the antifouling layer 14 by the nanoindentation method under the conditions of a temperature of 25° C. and a maximum indentation depth of 200 nm is more than 76%, preferably It is 80% or more, more preferably 81.5% or more, and still more preferably 85% or more. Such a configuration is suitable for resisting the influence of the wiping operation on the antifouling layer 14 and suppressing the deterioration of the antifouling property of the antifouling layer 14 .

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

The optical film F may have a layer (optical function layer) having a predetermined optical function. When the optical functional layer includes a plurality of layers, the layer on the side surface of the antifouling layer 14 of the optical functional layer is preferably also used as the above-mentioned inorganic oxide base layer 13 .

FIG. 2 shows the case where the optical film F includes the optical functional layer 20 between the adhesive layer 15 and the antifouling layer 14 . As described below, the optical functional layer 20 has a layer on the surface of the antifouling layer 14 that also serves as the inorganic oxide base layer 13 .

The optical functional layer 20 is disposed on one surface in the thickness direction T of the adhesive layer 15 . In this modification, the optical functional layer 20 is an anti-reflection layer used to suppress the reflection intensity of external light. That is, in this modification, the optical film F is an antireflection film with an antifouling layer attached.

The optical function layer 20 (anti-reflection layer) alternately has a high refractive index layer with a relatively large refractive index and a low refractive index layer with a relatively small refractive index in the thickness direction. In the anti-reflection layer, the net reflected light intensity is attenuated by the interference between the reflected light generated by the multiple interfaces of the multiple thin layers (high-refractive index layer, low-refractive index layer) contained in the layer. In addition, in the antireflection layer, by adjusting the optical film thickness (the product of the refractive index and the thickness) of each thin layer, the interference effect of attenuating the reflected light intensity can be exhibited. In this embodiment, specifically, the optical function layer 20 serving as an anti-reflection layer has a first high refractive index layer 21, a first low refractive index layer 22, a second high refractive index layer 21, and a second high refractive index layer in sequence toward one side of the thickness direction T. The refractive index layer 23 also serves as the second low refractive index layer 24 of the above-mentioned inorganic oxide base layer 13 .

The first high-refractive index layer 21 and the second high-refractive index layer 23 each contain a high-refractive-index material whose refractive index at a wavelength of 550 nm is preferably 1.9 or more. In order to have both 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 oxide. Tin (ATO), preferably niobium oxide is used.

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

The first low-refractive index layer 22 and the second low-refractive index layer 24 each contain a low-refractive-index material whose refractive index at a wavelength of 550 nm is preferably 1.6 or less. In order to have both low refractive index and low absorption of visible light, as the low refractive index material, for example, silicon dioxide (SiO ₂ ) and magnesium fluoride can be exemplified, and silicon dioxide is preferably used. As mentioned above, SiO ₂ and magnesium fluoride are also suitable as materials for the inorganic oxide base layer 13 .

The optical film thickness of the first low refractive index layer 22 is, for example, 15 nm or more and, 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 be formed by forming a film of material by a dry coating method, respectively. The second low-refractive-index layer 24 that also serves as the inorganic oxide base layer 13 can be formed by forming a material by a dry coating method. As a dry coating method, a sputtering method, a vacuum vapor deposition method, and CVD are mentioned, Preferably, a sputtering method is used. As a sputtering method, reactive sputtering is preferable from the viewpoint of the film-forming speed. Among the conditions of the sputtering method, the conditions of the sputtering method related to the formation of the inorganic oxide base layer 13 are the same as those described above.

In the optical film F shown in FIG. 2, the antifouling layer 14 is a dry coating film disposed on the second low refractive index layer 24 (inorganic oxide base layer 13). In the optical film F shown in FIG. 2, the elastic recovery ratio obtained by measuring the surface 14a of the antifouling layer 14 by the nanoindentation method under the conditions of a temperature of 25°C and a maximum indentation depth of 200 nm as described above is 76 % or more, preferably 80% or more, more preferably 81.5% or more, and still more preferably 85% or more. Such an optical film F is suitable for securing the peeling resistance of the antifouling layer 14 and suppressing the deterioration of the antifouling property. [Example]

The present invention will be specifically described below with reference to Examples. The present invention is not limited to the Examples. In addition, the specific numerical values such as the compounding amount (content), physical property value, parameter, etc. described below can be replaced by the corresponding compounding amount (content), physical property value, parameter, etc. described in the above-mentioned "Embodiment". "under" or "under" value) or lower limit (defined as "above" or "over" value).

[Example 1] First, a hard coat layer was formed on one side of a polyethylene terephthalate (PET) film (thickness 50 μm) as a transparent substrate (hard coat layer forming step). Specifically, first, the following components were mixed to obtain a mixed solution: a butyl acetate solution (trade name "UNIDIC17- 806", solid content concentration 80% by mass, manufactured by DIC Corporation) 100 parts by mass (in terms of solid content), photopolymerization initiator (trade name "IRGACURE 906", manufactured by BASF Corporation) 5 mass parts, leveling agent (trade name "IRGACURE906", manufactured by BASF Corporation) Name "GRANDICPC4100", manufactured by DIC Corporation) 0.01 part by mass. Next, the solid content concentration of the mixed solution was adjusted to 36% by adding a mixed solvent of cyclopentanone (CPN) and propylene glycol monomethyl ether (PGM) (the mass ratio of CPN to PGM was 45:55). Thereby, an ultraviolet curable resin composition (varnish) was prepared. Next, the resin composition was coated on one side of the PET film to form a coating film. Next, after drying this coating film by heating, it hardens by irradiating an ultraviolet-ray. The heating temperature was set to 90° C., and the heating time was set to 60 seconds. When irradiating ultraviolet rays, a high-pressure mercury lamp was used as a light source, and ultraviolet rays with a wavelength of 365 nm were used, and the cumulative irradiation light amount was set to 300 mJ/cm ² . Thereby, a hard coat layer (HC) with a thickness of 5 μm was formed on the PET film.

Next, plasma treatment was performed on the surface of the HC layer of the HC layer-attached PET film under a vacuum environment of 1.0 Pa by means of a roll-to-roll plasma treatment device. The plasma treatment used argon as the inert gas, and the discharge power was set to 780 W.

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

Next, an antifouling layer is formed (antifouling layer forming step). Specifically, an antifouling layer with a thickness of 12 nm was formed on the inorganic oxide base layer by a vacuum evaporation method using an alkoxysilane compound containing a perfluoropolyether group as an evaporation source. The vapor deposition source was a solid content obtained by drying "KY1903-1" (perfluoropolyether group-containing alkoxysilane compound, solid content concentration: 20 mass %) manufactured by Shin-Etsu Chemical Co., Ltd. In addition, the heating temperature of the vapor deposition source of the vacuum vapor deposition method was made into 260 degreeC.

The optical film of Example 1 was produced in the above manner. The optical film of Example 1 includes a resin film, a hard coat layer, an adhesive layer, an inorganic oxide base layer, and an antifouling layer in this order toward one side in the thickness direction.

[Example 2] The 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 to 10 μm instead of 5 μm.

[Example 3] Examples were produced 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 base layer was changed to 100 nm instead of 165 nm 3 Optical film.

[Example 4] The optical film of Example 4 was produced in the same manner as the optical film of Example 1, except that the film-forming gas pressure at the time of forming the inorganic oxide base layer was changed to 0.1 Pa instead of 0.3 Pa.

[Example 5] The thickness of the HC layer was changed to 10 μm instead of 5 μm, and the film-forming pressure when forming the inorganic oxide base layer was changed to 0.1 Pa instead of 0.3 Pa, except that the same procedure as the optical film of Example 1 was carried out. The optical film of Example 5 was produced in the same manner.

[Example 6] The 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 to 8 nm instead of 12 nm.

[Example 7] The 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 to 6 nm instead of 12 nm.

[Example 8] The 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 to 16 nm instead of 12 nm.

[Comparative Example 1] Comparative Example 1 was produced 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 base layer was changed to 30 nm instead of 165 nm the optical film.

<Hardness and elastic recovery rate of the surface of the antifouling layer> For the surfaces of the antifouling layers of the optical films of Examples 1 to 8 and Comparative Example 1, load-displacement measurement was performed by a nanoindentation method. Specifically, first, a measurement sample (5 mm×5 mm) was cut out from the optical film. Next, a nanoindenter (trade name "Triboindenter", manufactured by Hysitron Corporation) was used to perform load-displacement measurement on the surface of the antifouling layer of the measurement sample in accordance with ISO14577, and a load-displacement curve was obtained. In this measurement, the measurement mode is set to single indentation measurement, the measurement temperature is set to 25°C, the indenter is set to a Berkovich (triangular pyramid) type diamond indenter, and the maximum indentation depth of the indenter to the measurement sample during the load application process (Maximum displacement H1) was set to 200 nm, the indenter’s indentation speed was set to 20 nm/sec, and the indenter’s pull-out speed from the measurement sample during the load removal process was set to 20 nm/sec. Based on the obtained load-displacement curve, obtain the maximum load Pmax (the load acting on the indenter at the maximum displacement H1), the contact projected area Ap (the projected area of the contact area between the indenter and the sample at the maximum load), and the load removal The amount of plastic deformation H2 on the surface of the sample after the process (the depth of the concave portion of the surface of the sample maintained by the indenter after it leaves the surface of the sample). Then, the surface hardness of the antifouling layer (=Pmax/Ap) was calculated according to the maximum load Pmax and the contact projected area Ap. Furthermore, 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 the load was applied and the load was removed was calculated. These surface hardness (GPa) and elastic recovery rate (%) are shown in Table 1.

<Water Contact Angle> For each of the optical films of Examples 1 to 8 and Comparative Example 1, the water contact angle on the surface of the antifouling layer was investigated. First, water droplets were formed by dropping about 1 μL of pure water on the surface of the antifouling layer of the optical film. 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 Scratch Test> For each of the optical films of Examples 1 to 8 and Comparative Example 1, the degree to which the antifouling properties of the antifouling layer surface decreased after the eraser scratch test was investigated. Specifically, first, an eraser was moved back and forth on the surface of the antifouling layer of the optical film to scratch, and a scratch test (first eraser scratch test) was carried out. In this test, an eraser (Φ6 mm) manufactured by Minoan Company was used, the load of the eraser on the surface of the antifouling layer was set to 1 kg/6 mmΦ, and the scratching distance of the eraser on the surface of the antifouling layer (one-way reciprocating movement) ) was set to 20 mm, the scratching speed of the eraser was set to 40 rpm, and the number of times the eraser moved back and forth on the surface of the antifouling layer was set to 3000 times. Next, the water contact angle at the portion scratched by the eraser on the surface of the antifouling layer of the optical film was measured by the same method as the measurement method of the initial water contact angle θ ₀ . The measurement results are shown in Table ₁ as the water contact angle θ1 after the first eraser scratch test.

Next, the eraser was moved back and forth again to scratch the surface of the antifouling layer of the optical film, and a scratch test (second eraser scratch test) was performed. The scratch conditions are the same as those of the first eraser scratch test (the number of times the eraser is moved back and forth is set as a total of 6000 round trips in the first eraser scratch test and the subsequent second eraser scratch test). Next, the water contact angle at the portion scratched by the eraser on the surface of the antifouling layer of the optical film was measured by the same method as the measurement method of 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 scratch test. FIG. 3 is a graph in which the elastic recovery ratio and the water contact angle θ ₂ of each of the optical films of Examples 1 to 8 and Comparative Example 1 are plotted. In the graph of FIG. 3 , the horizontal axis represents the elastic recovery rate (%), and the vertical axis represents the water contact angle θ ₂ (°). In FIG. 3 , the dot graphs E1 to E8 show the measurement results of Examples 1 to 8, and the dot graph C1 shows the measurement results of Comparative Example 1.

<Evaluate> The optical films of Examples 1 to 8 are compared with the optical films of Comparative Example 1, and the water on the surface of the antifouling layer is in contact with the water after the eraser scratch test (the first eraser scratch test, the second eraser scratch test) The degree of angular drop is significantly smaller and, therefore, the antifouling property drops significantly less (at the surface of the antifouling layer, the less the water contact angle drops, the less the antifouling property drops).

[Table 1] Thickness of HC layer (μm) Inorganic oxide base layer Antifouling layer Thickness (nm) Film forming pressure (Pa) Thickness (nm) Surface hardness (GPa) Elastic recovery rate (%) Water contact angle θ ₀ (°) Water contact angle θ ₁ (°) Water contact angle θ ₂ (°) Example 1 5 165 0.3 12 1.19 81.87 113.9 101.8 100.0 Example 2 10 165 0.3 12 1.25 82.80 114.7 101.9 101.0 Example 3 10 100 0.3 12 1.07 80.77 115.3 102.0 96.1 Example 4 5 165 0.1 12 1.29 86.13 115.1 101.5 100.8 Example 5 10 165 0.1 12 1.33 86.10 117.1 103.0 102.5 Example 6 5 165 0.3 8 1.19 81.86 115.1 101.4 100.7 Example 7 5 165 0.3 6 1.18 81.86 116.3 96.3 92.4 Example 8 5 165 0.3 16 1.19 81.87 111.7 101.1 98.5 Comparative Example 1 10 30 0.3 12 1.01 75.00 115.4 83.5 70.0

11: Transparent substrate 12: Hard coating 13: Inorganic oxide base layer 14: Antifouling layer 14a: Surface 15: Adhesive layer 20: Optical functional layer 21: 1st high refractive index layer 22: 1st low refractive index layer 23: Second high refractive index layer 24: Second low refractive index layer F: Optical film (optical film with antifouling layer)

FIG. 1 is a schematic cross-sectional view of one embodiment of the optical film of the present invention. 2 is a schematic cross-sectional view of a modification of the optical film of the present invention (in this modification, the optical film is provided with an antireflection layer). 3 is a graph plotting the measured results of the elastic recovery ratios (horizontal axis) and the water contact angle θ ₂ (vertical axis) after the second eraser scratch test for the optical films of Examples 1 to 8 and Comparative Example 1 chart.

11: Transparent substrate

12: Hard coating

13: Inorganic oxide base layer

14: Antifouling layer

14a: Surface

15: Adhesive layer

F: Optical film (optical film with antifouling layer)

Claims (5)

An optical film with an antifouling layer, comprising a transparent substrate, a hard coat layer, an inorganic oxide base layer and an antifouling layer in sequence, The antifouling layer is a dry coating film disposed on the inorganic oxide base layer, Under the conditions of temperature of 25°C and maximum indentation depth of 200 nm, the elastic recovery ratio of the surface of the antifouling layer on the opposite side to the inorganic oxide layer was measured by nanoindentation method to be more than 76%. The optical film with an antifouling layer according to claim 1, wherein the antifouling layer has a thickness of not less than 1 nm and not more than 25 nm. The optical film with an antifouling layer according to claim 1 or 2, wherein the above-mentioned inorganic oxide base layer comprises silicon dioxide. The optical film with an antifouling layer according to claim 1 or 2, wherein the inorganic oxide base layer has a thickness of 50 nm or more. The optical film with an antifouling layer according to claim 1 or 2, wherein the hard coat layer has a thickness of 1 μm or more and 50 μm or less.

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