TW201830056A - Optical film, polarizing plate and display member using the same including a transparent substrate, a primer layer and an optical functional layer - Google Patents

Abstract

An object of the present invention is to provide an optical film which is excellent in durability, capable of suppressing rainbow spots and interference fringes, has high visibility, and is thin. The invention is also to provide a polarizing plate and a display member using the same. The solution of the present invention is an optical film which is provided on at least one side of a transparent substrate 2 comprising polyethylene terephthalate, and provided with a primer layer 3 and an optical functional layer 4 containing an active energy ray-curable resin. The optical film is characterized in that the in-plane retardation of the transparent substrate 2 is 600 nm or less, the retardation in the thickness direction is 3000 to 8000 nm, and the thickness of the primer layer 3 is 60 to 120 nm. In addition, when the refractive index of the transparent substrate 2 is A and the refractive index of the optical functional layer is B, the refractive index of the primer layer 3 is within the range of {(A+B)/2-0.02} to {(A+B)/2+0.02}.

Description

   Optical film, polarizing plate and display member using the same   

The present invention relates to an optical film used in an image display device and the like, a polarizing plate and a display member using the same.

In a display member such as a liquid crystal display panel or a touch panel, an optical film such as a hard coat film, an anti-reflection film, or an anti-glare film is used. As a transparent substrate constituting an optical film, a cellulose ester film such as triethyl cellulose, which is excellent in transparency or optical isotropy, has been used so far, but the cellulose ester film has durability, especially moisture resistance and heat resistance. Inadequate disadvantages. Therefore, there have been various reviews on the use of polyethylene terephthalate (PET) films as transparent substrates instead of cellulose ester films. PET film has the advantages of excellent transparency, moisture resistance, heat resistance, mechanical strength, and low cost.

However, since polyethylene terephthalate has an aromatic ring in its molecular structure, birefringence occurs in the surface of the PET film. If an optical film using a PET film as a transparent substrate is superimposed on a polarizing film , A color spot such as a rainbow occurs (hereinafter, referred to as "rainbow spot").

As a technique for eliminating iridescence that occurs when PET is used for a transparent substrate, there is a device described in Patent Document 1, for example. In Patent Document 1, the use of a polyester substrate having an in-plane retardation (Re) of 3,000 nm or more improves the rainbow spot when used in a display device.

Prior art literature Patent literature

Patent Document 1 Japanese Patent Publication No. 5556926

With the reduction in thickness and weight of display devices in recent years, it is required to reduce the thickness of optical films, and to reduce the thickness of transparent substrates used for optical films. However, in order to suppress the rainbow spots that occur when a PET film is used, if the in-plane retardation of the PET film is increased as described in Patent Document 1, the thickness of the PET film inevitably becomes larger. That is, when a PET film with high hysteresis is used for a transparent substrate, thinning becomes difficult.

When a PET film is used as a transparent substrate, the refractive index difference between the transparent substrate and the optical function layer formed thereon tends to be large, and there is also a problem that interference fringes are caused by the refractive index difference.

Therefore, an object of the present invention is to provide an optical film which is excellent in durability, suppresses iridescence and interference fringes, has high visibility, and can be reduced in thickness, and a polarizing plate and a display member using the same.

The optical film of the present invention is an optical film provided with a primer layer and an optical function layer containing an active energy ray hardening resin on at least one side of a transparent substrate including polyethylene terephthalate, which is characterized in that it is transparent The in-plane hysteresis of the substrate is below 600 nm, and the hysteresis in the thickness direction is 3000 to 8000 nm, the thickness of the primer layer is 60 to 120 nm, the refractive index of the transparent substrate is taken as A, and the refractive index of the optical function layer is taken as B At this time, the refractive index of the primer layer is in the range of {(A + B) /2-0.02} to {(A + B) /2+0.02}.

The polarizing plate, the display member, and the display device of the present invention each have the hard coat film described above.

According to the present invention, it is possible to provide an optical film that is excellent in durability, suppresses iridescence and interference fringes, has high visibility, and can be made thinner, and a polarizing plate and a display member using the same.

1‧‧‧ optical film

2‧‧‧ transparent substrate

3‧‧‧ primer layer

4‧‧‧ Optical Function Layer

FIG. 1 is a schematic cross-sectional view of an optical film according to an embodiment.

Implementation of the invention

FIG. 1 is a schematic cross-sectional view of an optical film according to an embodiment.

The optical film 1 is one in which a primer layer 3 and an optical function layer 4 are sequentially laminated on one surface of the transparent substrate 2.

    (Transparent substrate)    

The transparent base material 2 is a thin film that serves as a substrate for the optical film 1. The thickness of the transparent substrate 2 is preferably 12 to 40 μm. When the thickness of the transparent substrate 2 is less than 12 μm, the transparent substrate 2 becomes too thin, and the hardness of the optical function layer 4 and the strength of the optical film 1 decrease. On the other hand, if the thickness of the transparent base material 2 exceeds 40 μm, the optical film 1 becomes thicker, which cannot contribute to the reduction in thickness of a display member using the optical film 1.

As the transparent substrate 2, a PET film having an in-plane retardation (Re) of 600 nm or less and a thickness direction retardation of 3000 to 8000 nm is used. By using PET films with in-plane retardation and retardation in the thickness direction within this range, rainbow spots can be suppressed when the optical film 1 is superposed on the polarizing plate or when a polarizer is provided on the optical film 1, and the transparent substrate 2 can be realized. Thin film. When the in-plane hysteresis exceeds 600 nm or the thickness-direction hysteresis exceeds 8000 nm, the thickness of the transparent substrate 2 is not suitable as it is thicker than the aforementioned 40 μm. In addition, when the retardation in the thickness direction is less than 3000 nm, it is not suitable because the hardness of the surface of the optical function layer 4 when the optical film 1 is configured is reduced.

In addition, the PET film is excellent in low moisture permeability (water vapor barrier property), transparency, heat resistance, and mechanical strength. By using the PET film as the transparent substrate 2, the durability of the optical film 1 can be improved. In addition, since PET films are cheap, they are also advantageous in terms of manufacturing costs. Polyvinyl alcohol (PVA) films used for polarizing plates have high hygroscopicity, swell due to absorption of moisture, and change in size. Therefore, in order to protect against moisture, a protective film is generally laminated on both sides. Since the optical film 1 of this embodiment uses a PET film having water vapor barrier properties (low moisture permeability) as the transparent base material 2, it is particularly suitable as a protective film for a polarizing plate.

    (Primer layer)    

The primer layer 3 has a function as an easy-adhesion layer that increases the adhesion of the optical function layer 4 to the transparent base material 2 and a function of reducing the refractive index difference between the transparent base material 2 and the optical function layer 4. The primer layer 3 is formed by, for example, applying a composition for forming a primer layer containing at least an active energy ray-curable resin on the surface of the transparent substrate 2 and curing it. The thickness of the primer layer 3 is set to 60 to 120 nm. If the thickness of the primer layer 3 deviates from this range, interference fringes occur when the optical film 1 is used in an image display device, and the visibility of the image display device is reduced. The thickness of the primer layer 3 is more preferably 80 to 100 nm, and within this range, the occurrence of interference fringes can be more suppressed.

    (Optical Function Layer)    

The optical function layer 4 is a layer that provides various optical functions and surface hardness such as scratch resistance, low reflection, and anti-glare properties to the optical film 1. The optical function layer 4 can be formed by, for example, hardening an optical function layer-forming composition containing at least an active energy ray-curable resin on the surface of the primer layer 3. The thickness of the optical function layer 4 is preferably 1 to 20 μm. If the thickness of the optical function layer 4 is less than 1 μm, the hardness of the optical function layer 4 is insufficient. On the other hand, if the thickness of the optical function layer 4 exceeds 20 μm, the thickness of the optical film 1 becomes thicker, which cannot contribute to the reduction in thickness of the display member using the optical film 1.

In addition, the optical function layer 4 may include various inorganic fine particles or organic fine particles (fillers) according to its function. For example, when hard-coating property is provided to the optical function layer 4, the optical function layer 4 may contain inorganic fine particles such as colloidal silica. In this case, as the colloidal silica, an average particle diameter of 80 nm or less is used. When the average particle diameter of the colloidal silica exceeds 80 nm, the transparency of the optical film is reduced. The lower limit value of the average particle diameter of the colloidal silica is not particularly limited, but one having an average particle diameter of 5 nm or more can be preferably used. The amount of colloidal silica added is 20 to 50% by mass based on the total solid content contained in the composition for forming a hard coat layer. If the amount of colloidal silica added is less than 20% by mass of the solid content of the resin, the hardness of the hard coat layer becomes insufficient. On the other hand, if the amount of colloidal silica added exceeds 50% by mass of the solid content of the resin, the optical function layer becomes brittle, resulting in a decrease in hardness.

Here, the relationship between the refractive indices of the transparent substrate 2, the primer layer 3, and the optical function layer 4 will be described. Hereinafter, the refractive index of the transparent base material 2 is referred to as A, the refractive index of the optical function layer 4 is referred to as B, and the refractive index of the primer layer 3 is referred to as C. In the optical film 1 of the present invention, the refractive index C of the primer layer 3 satisfies the following condition (1).

(A + B) /2-0.02≦C≦ (A + B) /2+0.02… (1)

By setting the thickness of the primer layer in the range of 60 to 120 μm and the refractive index C in the range of the above condition (1), it is possible to suppress the refractive index difference caused by the transparent substrate 2 and the optical function layer 4. The occurrence of interference fringes. If the refractive index C of the primer layer is lower than the lower limit of the above condition (1), the refractive index difference between the transparent substrate 2 and the primer layer 3 is greater than the refractive index difference between the optical function layer 4 and the primer layer 3. The refractive index C of the paint layer exceeds the upper limit of the above condition (1), the refractive index difference between the optical function layer 4 and the primer layer 3 is larger than the refractive index difference between the transparent substrate 2 and the primer layer 3, so in either case The suppression effect of the interference fringes caused by the primer layer 3 is reduced.

As an example, the refractive index of the PET film used as the transparent substrate 2 can be set within a range of 1.62 to 1.66, the refractive index of the optical function layer 4 can be set within a range of 1.46 to 1.56, and the refraction of the primer layer 3 can be set. The rate is set in the range of 1.53 to 1.62.

In addition, the active energy ray-curable resin used in the primer layer 3 and the optical function layer 4 is a resin that is polymerized and hardened by irradiation with active energy rays such as ultraviolet rays and electron rays. For example, monofunctional and difunctional Or trifunctional or more (meth) acrylate monomer. In addition, in this specification, "(meth) acrylate" is a general term for both acrylate and methacrylate, and "(meth) acrylfluorenyl" is both acrylfluorenyl and methacrylfluorenyl. The general term.

Examples of the monofunctional (meth) acrylate compound include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, N-butyl (meth) acrylate, isobutyl (meth) acrylate, tertiary butyl (meth) acrylate, propylene oxide (meth) acrylate, allyl morpholine, allyl vinyl pyrrolidine Ketone, tetrahydrofurfuryl acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isopropyl (meth) acrylate Ester, isodecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, cetyl (meth) acrylate, octadecyl (meth) acrylate, (meth) Benzyl acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethyl carbitol (meth) acrylate, phosphoric acid (meth) acrylate, Ethylene oxide modified phosphoric acid (meth) acrylate, phenoxy (meth) acrylate, oxirane modified phenoxy (meth) acrylate, propylene oxide modified phenoxy (meth) acrylate Ester, nonylphenol (meth) acrylate, ethylene oxide modified nonylphenol (meth) acrylate, propylene oxide modified nonylphenol (meth) acrylate, methoxydiethylene glycol (Meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, 2- (meth) acryloxyethyl-2-hydroxypropyl Phthalates, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- (meth) acryloxyethyl hydrogen phthalate, 2- (methyl) Propylene hydroxypropyl hydrogen phthalate, 2- (meth) propylene Ethoxypropyl hexahydrophthalate, 2- (meth) acrylic ethoxypropyl tetrahydrophthalate, dimethylaminoethyl (meth) acrylate, (formaldehyde) (Propyl) trifluoroethyl acrylate, tetrafluoropropyl (meth) acrylate, hexafluoropropyl (meth) acrylate, octafluoropropyl (meth) acrylate, derived from 2-adamantane, adamantanediol The adamantane derivatives such as adamantane acrylate having a monovalent mono (meth) acrylate, mono (meth) acrylate, ethoxylated o-phenylphenol acrylate, and the like.

Examples of the bifunctional (meth) acrylate compound include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, butanediol di (meth) acrylate , Hexanediol di (meth) acrylate, nonanediol di (meth) acrylate, ethoxylated hexanediol di (meth) acrylate, propoxylated hexanediol di (meth) Acrylate, polyethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethoxy Bis (meth) acrylates such as neopentyl glycol di (meth) acrylate, hydroxytrimethylacetate neopentyl glycol di (meth) acrylate, 9,9-bis [4- [2- Propylene ethoxyethoxy] phenyl] fluorene, 2,2-bis [4- (methacryl ethoxyethoxy) phenyl] propane and the like.

Examples of the trifunctional or higher (meth) acrylate compound include trimethylolpropane tri (meth) acrylate, ethoxylated trimethylolpropane tri (meth) acrylate, and propoxylate. Tris (methyl) of trimethylolpropane tri (meth) acrylate, 2-hydroxyethyl isotricyanate tri (meth) acrylate, glycerol tri (meth) acrylate, etc. Trifunctional (meth) acrylate compounds such as acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, or pentaerythritol Tetrakis (meth) acrylate, trimethylolpropane tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, trimethylolpropane penta ( (Meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane hexa (meth) acrylate, etc. A polyfunctional (meth) acrylate compound in which a portion of the acrylate is substituted with an alkyl group or ε-caprolactone .

Moreover, as an active-energy-ray-curable resin, a urethane (meth) acrylate can also be used. Examples of the urethane (meth) acrylate include a product obtained by reacting an isocyanate monomer or a prepolymer with a polyester polyol, and a (meth) acrylate having a hydroxyl group Body response.

Examples of the urethane (meth) acrylate include pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate hexamethylene diisocyanate amino group Formate prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate toluene diisocyanate urethane prepolymer, pentaerythritol triacrylate isophorone diisocyanate Urethane prepolymer, dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymer, and the like.

The above active energy ray-curable resins may be used singly or in combination of two or more kinds. The above-mentioned active energy ray-curable resin may be a monomer in the composition for forming a primer layer or the composition for forming a hard coat layer, or may be an oligomer partially polymerized.

A photopolymerization initiator is also added to the composition for forming a primer layer or the composition for forming an optical function layer. Examples of the photopolymerization initiator include 2,2-ethoxyacetophenone, 1-hydroxycyclohexylphenyl ketone, diphenylethylene dione, benzoin, benzoin methyl ether, benzene Ethyl ethyl ether, p-chlorodiphenyl ketone, p-methoxydiphenyl ketone, Michelin, acetophenone, 2-chlorothioxanthone, and the like. These can be used individually or in combination of 2 or more types.

Further, a solvent may be appropriately added to the composition for forming a primer layer or the composition for forming an optical function layer. Examples of the solvent include dibutyl ether, dimethoxymethane, dimethoxyethane, diethoxyethane, propylene oxide, 1,4-di Alkane, 1,3-dioxolane, 1,3,5-tri Ethers such as alkane, tetrahydrofuran, anisole and phenyl ether, polyethylene glycol methyl ether, or acetone, methyl ethyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, methyl Ketones such as isobutyl ketone, cyclopentanone, cyclohexanone and methyl cyclohexanone, or ethyl formate, propyl formate, n-pentyl formate, methyl acetate, ethyl acetate, methyl propionate, Ester such as ethyl propionate, n-pentyl acetate and γ-butyrolactone, and cellosolvents such as methyl cellosolve, cellosolve, butyl cellosolve, cellosolve acetate. These can be used individually or in combination of 2 or more types.

In addition, antifouling agents, surface modifiers, leveling agents, refractive index modifiers, photosensitizers, conductive materials, etc. may be added to the composition for forming the primer layer or the composition for forming the optical function layer, if necessary. Of additives.

The optical film 1 of this embodiment can be coated with the above-mentioned coating composition for forming a primer layer by a wet coating method on at least one side of the transparent substrate 2 by roll-to-roll, and the coating film is irradiated with electron beams or After the active energy ray-curable resin is hardened by an ultraviolet ray or the like, the coating liquid of the above-mentioned composition for forming an optical function layer is applied to the primer layer 3 by a wet coating method, and the coating film is irradiated with electron rays or ultraviolet rays The active energy ray and the like are formed by curing an active energy ray-curable resin. As the wet coating method, a flow coating method, a spray coating method, a roll coating method, a gravure roll coating method, an air blade coating method, a blade coating method, a line blade coating method, a knife coating method, a reverse coating method, and a transfer roll coating can be adopted. Well-known methods such as a method, a micro gravure coating method, a kiss coating method, a casting coating method, a slot die coating method, a calendar coating method, a die coating method, and the like. When the coating film is hardened by ultraviolet irradiation, a high-pressure mercury lamp, a halogen lamp, a xenon lamp, a fusion lamp, or the like can be used during the ultraviolet irradiation. The amount of ultraviolet radiation is usually about 100 to 800 mJ / cm ² .

In the optical film 1 of this embodiment, since a PET film is used as the transparent base material 2, the moisture permeability is lower than that of an ethyl cellulose cellulose film such as triethyl cellulose, and the water vapor barrier property is excellent. In addition, the PET film is also excellent in heat resistance and mechanical strength, and by using the PET film as the transparent substrate 2, the durability of the optical film 1 can be improved. In addition, PET films are suitable as optical films for use in image display devices because they are highly transparent and inexpensive.

In general, if an optical film using a PET film as the transparent substrate 2 is used in an image display device, the rainbow spots caused by the birefringence of PET itself or the refractive indices of the transparent substrate 2 and the optical function layer 4 The interference fringes caused by the difference are easy to occur. These iridescent spots or interference fringes are the main reason for reducing the visibility of the image display device. However, in the optical film 1 of this embodiment, by using a PET film having an in-plane retardation of 600 nm or less and a thickness direction retardation of 3000 to 8000 nm as the transparent substrate 2, the occurrence of iridescence can be suppressed. In addition, by setting the refractive index C of the primer layer 3 within the above range, interference fringes caused by the refractive index difference between the transparent substrate 2 and the optical function layer 4 can be suppressed.

    (Other modifications)    

Furthermore, the optical film 1 of this embodiment may be used to form a polarizing plate. Specifically, a polarizing film is formed by adsorbing and aligning iodine or dye on a PVA film, and by bonding the optical film 1 of this embodiment on both sides of the polarizing film as a protective film, a polarizing plate can be formed. Alternatively, a polarizing plate can be formed by providing a polarizing layer on the other side of the transparent substrate 2 of the optical film 1 shown in FIG. 1 (the side on which the optical function layer 4 is not provided) by a well-known method. In this case, the optical film 1 or another protective film may be further bonded to the polarizing layer. The polarizing layer can be formed by, for example, adsorbing and aligning iodine or a dye on a PVA film.

In addition, the optical film 1 of this embodiment can be used for display members such as an anti-reflection film or an anti-glare film used in an image display device in addition to a hard coating film. The antireflection film can be formed by providing an antireflection layer in which a plurality of layers having different refractive indices are laminated on the optical function layer 4 shown in FIG. 1. As an example of the structure of the anti-reflection film, an optical function layer 4, a high refractive index layer, and a low refractive index layer having a lower refractive index than the high refractive index layer are laminated in this order on the transparent substrate 2. Between the optical function layer 4 and the high refractive index layer, a middle refractive index layer having a lower refractive index than the high refractive index layer and a higher refractive index than the low refractive index layer may be further provided. The anti-glare film can be formed by blending a filler in the optical function layer 4 shown in FIG. 1 so that the surface of the optical function layer 4 exhibits fine unevenness.

The optical film 1 of this embodiment can be used in combination with a liquid crystal panel or the like to constitute a display device. Examples of the configuration of the display device include an anti-reflection film, a polarizing plate, a liquid crystal panel, a polarizing plate, and a backlight unit in which an anti-reflective film using the hard-coated film of this embodiment is laminated in this order from the observation side. In addition, the touch sensor may be further laminated to form a display device with the touch sensor.

The optical film 1 of this embodiment can be used as a display device such as a smart phone, a tablet computer, a notebook computer, or a display device (touch panel) with a touch sensor. Examples of the optical film include a polarizing plate, an anti-reflection film, and anti-glare properties, in addition to the hard-coated film. Specifically, the optical film 1 according to this embodiment can be a film provided on the outermost surface of a display panel such as a liquid crystal display device, or can be provided on the outermost surface of an on-cell or in-cell touch panel. Film, or in a touch panel assembled by a direct bonding method or an air gap method, as an intermediate film provided between the touch sensor and the display panel.

In this embodiment, an example in which the primer layer 3 and the optical function layer 4 are provided on one surface of the transparent substrate 2 will be described. However, the primer layer 3 and the transparent substrate 2 may be provided on both surfaces. Optical film of the optical function layer 4.

    [Example]    

Hereinafter, embodiments of the present invention will be described in detail. In the following examples and comparative examples, as an example of the optical film, a hard-coated film (that is, the optical functional layer is a hard-coat layer) is produced. However, the optical film of the present invention is not limited to the hard-coated film.

    <Composition for forming primer layer>    

The following materials were mixed at the ratios shown in Table 1 to prepare primers 1 to 7 (referred to as coating liquids P1 to P7). The unit of the mixing ratio of each material shown in Table 1 is "mass part". In addition, Table 1 shows the refractive indexes of the primer layer-forming compositions 1 to 7 after curing.

    ‧Resin material 1    

Trade name: UF8001G (non-yellowing oligomeric urethane acrylate), Kyoeisha Chemical Co., Ltd.

    ‧Resin material 2    

Product name: A-LEN-10 (ethoxylated o-phenylphenol acrylate), Shin Nakamura Chemical Industry Co., Ltd.

    ‧Resin material 3    

Product name: A-BPEF (9,9-bis [4- (2-propenyloxyethoxy) phenyl] 苯基), Shin Nakamura Chemical Industry Co., Ltd.

    ‧Polymerization initiator    

Trade name: Irgacure (registered trademark) 184 (1-hydroxycyclohexylphenyl ketone), BASF

    ‧Solvent    

Methyl ethyl ketone (MEK)

Polyethylene glycol monomethyl ether (PGME)

    <Composition for forming hard coat layer>    

The following materials were mixed at the ratios described in Table 2 to prepare compositions 1 to 3 for hard coat layer formation (referred to as coating liquids H1 to H3). The unit of the mixing ratio of each material shown in Table 2 is "mass part." In addition, Table 2 also shows the refractive indexes after hardening the compositions 1 to 3 for forming a hard coat layer.

    ‧Resin material 4    

Product Name: A-TMM-3L (Pentaerythritol Triacrylate), New Nakamura Chemical Industry Co., Ltd.

    ‧Resin material 5    

Product Name: BPE-80N (2,2-bis [4- (methacryloxyethoxy) phenyl] propane), Shin Nakamura Chemical Industry Co., Ltd.

    ‧Inorganic fine particles    

Commodity name: MEK-ST (colloidal silica, average particle size 15nm), Nissan Chemical Industry Co., Ltd.

    ‧Polymerization initiator    

Trade name: Irgacure (registered trademark) 184 (1-hydroxycyclohexylphenyl ketone), BASF

    ‧Solvent    

Methyl ethyl ketone (MEK)

Polyethylene glycol monomethyl ether (PGME)

    (Examples 1 to 21 and Comparative Examples 2 to 8)    

As the transparent substrate, a PET film having in-plane retardation, thickness-direction retardation, and thickness shown in Table 3 was used. On one side of the transparent substrate, the coating liquid of the composition for forming the primer layer shown in Table 3 was applied and dried by a bar coating method, and then irradiated with a 200-mJ / m ² irradiation amount using a metal halide lamp The coating film is hardened by ultraviolet rays to form a primer layer. In addition, the application amount of the coating liquid of the composition for forming a primer layer was adjusted so that the thickness of the cured film became the value shown in Table 3.

Next, on the formed primer layer, the coating liquid of the composition for forming a hard coat layer shown in Table 3 was applied and dried by a bar coating method, and then a metal halide lamp was used to irradiate 200 mJ of light. / m ² irradiates ultraviolet rays to harden the coating film to form a hard coat layer. In addition, the application amount of the coating liquid of the composition for forming a hard coat layer was adjusted so that the thickness of the cured film became the value shown in Table 3.

    (Comparative example 1)    

As the transparent substrate, a triethylammonium cellulose film having in-plane retardation, thickness-direction retardation, and thickness shown in Table 3 was used. On one side of the transparent substrate, a primer layer is not formed, and the coating liquid of the composition for forming a hard coat layer shown in Table 3 is applied and dried by a bar coating method, and then a metal halide lamp is used to The irradiation dose is 200 mJ / m ^{2 and the} coating film is hardened by irradiating ultraviolet rays to form a hard coat layer. In addition, the application amount of the coating liquid of the composition for forming a hard coat layer was adjusted so that the thickness of the cured film became the value shown in Table 3.

For the hard-coated films obtained in Examples 1 to 21 and Comparative Examples 1 to 8, the degree of rainbow spots, the degree of interference fringes, moisture permeability, and pencil hardness were evaluated. The evaluation methods and evaluation criteria are as follows.

    <Rainbow spot>    

The hard-coated films of each example and each comparative example were sandwiched between two polarizing plates, and the degree of rainbow spots was visually observed, and evaluated using the following criteria.

：: No rainbow spots were seen.

(Circle): A rainbow spot is seen slightly, but it is fully suppressed.

△: Iris is seen.

×: The rainbow spot is noticeably noticeable.

    <Interference fringes>    

On the surface of the transparent substrate of the hard-coated film of each example and each comparative example (the surface on which the primer layer and the hard-coat layer are not laminated), a matte black coating is applied, and directly under the three-wavelength fluorescent lamp. The degree of interference fringes on the surface of the low-refractive-index layer was visually observed, and evaluated using the following criteria.

：: No interference fringes were seen.

○: Interference fringes are slightly seen, but have been sufficiently suppressed.

Δ: Interference fringes are seen.

×: Interference fringes are noticeable.

    <Water vapor transmission rate (water vapor transmission rate)>    

For the hard-coated films of Examples and Comparative Examples, the water vapor transmission rate in an environment of a temperature of 40 ° C and a relative humidity of 90% RH was measured according to JIS-Z208. When the measured water vapor transmission rate is 80 g / m ² / day or less, it is judged that the water vapor barrier property is sufficient.

    <Pencil hardness>    

According to JIS K5600 (4.9N load), a pencil scratch tester (HA-301, TESTER Industries Co., Ltd.) was used to measure the pencil hardness of the surface of the hard coating layer. When the measured pencil hardness is 2H or more, it is judged that the surface hardness is sufficient.

Materials used in the hard-coated films of Examples 1 to 21 and Comparative Examples 1 to 8 and their physical property values, as well as evaluation values of rainbow spots, interference fringes, moisture permeability, and pencil hardness are also displayed.

The hard-coating films of Examples 1 to 21, iridescence and interference fringes, were sufficiently suppressed to such an extent that the visibility of the image when used in an image display device was not impaired, and the water vapor barrier properties and surface hardness were also excellent. In addition, the hard coat films of Examples 1 to 3, 6 to 11, 20, and 21 having a thickness of the primer layer within a range of 80 to 100 nm were more effective in reducing interference fringes than other examples, and could not be visually confirmed.

In contrast, the hard-coated film of Comparative Example 1 has low water vapor barrier properties because triacetam cellulose is used for the transparent substrate.

Since the hard-coated film of Comparative Example 2 uses a PET film with high hysteresis (in-plane retardation of 10000 nm) as a transparent substrate, although the iridescence is suppressed, the transparent substrate is thicker than those of Examples 1-21. Therefore, it was confirmed that the hard coating film of Comparative Example 2 is not suitable for thinning.

In the hard-coated film of Comparative Example 3, since a PET film having a thickness direction retardation of less than 3000 nm was used as a transparent substrate, the surface hardness of the hard-coated layer was reduced.

Although the hard-coated film of Comparative Example 4 uses a PET film having relatively low in-plane retardation as a transparent substrate, the in-plane retardation of the PET film exceeds 600 nm, and rainbow spots cannot be sufficiently suppressed.

In the hard coat films of Comparative Examples 5 and 6, since the thickness of the primer layer was outside the range of 60 to 120 nm, interference fringes could not be sufficiently suppressed.

The hard coat films of Comparative Examples 7 and 8 cannot reduce the refractive index difference of the transparent substrate and the primer layer or the refractive index of the hard coat layer and the primer layer because the refractive index of the primer layer is outside the range of the above condition (1). Poor, as a result, interference fringes cannot be sufficiently suppressed.

As described above, according to the present invention, it has been confirmed that an optical film can be provided which is excellent in durability, suppresses iridescence and interference fringes, has high visibility, and can be made thinner.

Industrial availability

The optical film of the present invention is a film used for an image display device, such as a hard-coated film, a low-reflection film, an anti-glare film, a protective film for a polarizing plate, and the like.

Claims (5)

    An optical film is an optical film provided with a primer layer and an optical function layer containing an active energy ray-curable resin on at least one side of a transparent substrate including polyethylene terephthalate, characterized in that: The in-plane hysteresis of the transparent substrate is 600 nm or less, and the thickness direction hysteresis is 3000 to 8000 nm. The thickness of the primer layer is 60 to 120 nm. The refractive index of the transparent substrate is taken as A, and the optical function layer is refracted. When the rate is taken as B, the refractive index of the primer layer is in the range of {(A + B) /2-0.02} ~ {(A + B) /2+0.02}.         For example, the optical film of claim 1, wherein the thickness of the optical function layer is 1 to 20 nm, and the refractive index B of the optical function layer is 1.46 to 1.56.         For example, the optical film of claim 1 or 2, wherein the pencil hardness of the optical function layer is 2H or more.         A polarizing plate having an optical film according to any one of claims 1 to 3.         A display member having the optical film according to any one of claims 1 to 3.