JP2010092003A - Antireflection film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antireflection film which has high transparency and excellent mechanical characteristics. <P>SOLUTION: A hard coat layer 2 and an antireflection layer 4 are laminated on a transparent base material film 1 and the antireflection layer 4 is formed of four or more layers of a laminate constituted by alternately laminating a high refractive index material layer and a low refractive index material layer and following conditions are satisfied: (1) in the transparent base material film; a PET film having thickness of 70 to 200 μm, haze of 0.5% or less and total light transmittance of 88% or more is used, (2) in the hard coat layer; a photocurable resin of 3 to 20 μm thickness is used, haze is 0.4% or less, total light transmittance is 89% or more and when a pencil hardness test is performed five times by using 3H pencils with 500 g load, the layer is not injured two or more times, (3) The antireflection layer; total thickness is 100 to 300 nm, and (4) in the antireflection film; haze is 0.4% or less, total light transmittance is 92% or more and luminous reflectance is 0.9% or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an antireflection film having good post-processability and high transparency.

  In an optical display device such as an LCD, CRT, or plasma display panel, an antireflection film that prevents reflection of external light such as sunlight or a fluorescent lamp is often used. In particular, for outdoor use where the reflection of outside light is large, an antireflection film, that is, an AR film, having a reflectance that is almost zero is required.

  In general, the AR film uses a dry coating technique capable of forming a thin film having a thickness of several nanometers. Among these, the sputtering method is a thin film with higher visibility than other dry coating methods such as vapor deposition, ion plating, and CVD because it has higher film thickness uniformity and fewer defects such as pinholes. Can be formed. In addition, since a dense film can be formed, it is possible to form a thin film with extremely excellent mechanical properties.

  The antireflection film is often used in LCD applications, and an antireflection layer configuration in which the antireflection film is laminated on a protective film of a polarizing plate is common. A triacetyl cellulose (TAC) film is used as a protective film for this polarizing plate, that is, a base material for an antireflection film, because of its good hygroscopicity and very high transparency. However, when this TAC film is used for purposes other than LCD applications, it has the great advantage of high transparency, but (1) it tends to cause appearance defects such as discoloration and corrosion due to hydrolysis, etc., and is environmentally durable. Is bad. (2) Poor workability in the subsequent process. (3) There is a problem that it is difficult to supply for purposes other than LCD applications. Therefore, in the case of using for LCD applications, development of an antireflection film having transparency using a substrate other than TAC is desired.

  Of course, an antireflection film using a substrate other than TAC, particularly polyethylene terephthalate (PET) has been proposed. For example, as a technique using a PET film, there are Patent Documents 1 and 2. In general, dry coating methods, especially sputtering methods, have high film thickness uniformity, as described above, so that reflection with extremely low reflectivity based on a dense optical design with multiple layers stacked. Preventive film can be made. The price is that the process cost is high. As a result, the price is higher and the price is higher than that of the antireflection film prepared by the wet method. For this reason, even if a PET film or the like, which is inferior in optical performance as compared with TAC or the like, is used as a base material, there is no demand at present.

Japanese Patent No. 3141129 JP-A-9-193328

  In view of the above, the present invention provides an antireflection film having extremely high transparency and excellent mechanical properties and high added value performance even when a polyethylene terephthalate film is used as a base material. The task was to do.

The invention according to claim 1 is an antireflection film obtained by sequentially laminating at least a hard coat layer and an antireflection layer on at least one surface of a transparent substrate film, and the antireflection layer is a high It consists of a laminate of four or more layers in which a refractive material layer and a low refractive index layer are alternately laminated, the outermost layer of the antireflection layer is a low refractive index layer, and the following conditions (1) to (4) It is an antireflection film characterized by satisfying all of the above.
(1) Transparent base film: A polyethylene terephthalate film having a thickness of 70 μm to 200 μm and a haze of 0.5% or less is used.
(2) Hard coat layer: A photocurable resin having a thickness of 3 μm to 20 μm is used.
(3) Antireflection layer: The total thickness is 100 to 300 nm.
(4) Antireflection film: haze is 0.4% or less, total light transmittance is 92% or more, and luminous reflectance is 0.9% or less.
The invention according to claim 2 is the antireflection film according to claim 1, wherein the total light transmittance of the transparent substrate film (1) is 88% or more.
In the invention according to claim 3, the haze of the (2) hard coat layer is 0.4% or less, the total light transmittance is 89% or more, and a pencil hardness test (JIS K5400-1990). 3. The antireflection film according to claim 1, wherein when the surface of the hard coat layer is tested 5 times with a 3 H pencil under a load of 500 g, two or more scratches are not damaged.
The invention according to claim 4 is characterized in that the antireflective layer has a low refractive index layer made of silicon oxide and a high refractive index layer made of niobium oxide, and is laminated by a dry coating method using a sputtering method. The antireflection film according to any one of claims 1 to 3. In addition, silicon oxide (SiOx) here refers mainly to silicon dioxide (SiO ₂ ). However, when oxygen is deficient or increased, x of SiOx changes within a range of 1.8 to 2.2.
The invention according to claim 5 is the antireflection film according to claim 4, wherein the pressure at the time of lamination of the antireflection layer by the sputtering method is 0.1 to 0.6 Pa.
The invention according to claim 6 is formed of a metal, an alloy made of two or more metals, a metal compound, or a mixture thereof between the hard coat layer and the antireflection layer. 6. The antireflection film according to claim 1, further comprising a primer layer comprising the above.
The invention according to claim 7 is the antireflection film according to any one of claims 1 to 6, wherein an antifouling layer is provided on the antireflection layer.
The invention according to claim 8 is the antireflection film according to claim 7, wherein the antifouling layer is a fluorine compound formed by a vacuum deposition method.
The invention according to claim 9 is the antireflection according to claim 7 or 8, wherein a water droplet contact angle on the antifouling layer side surface is 100 ° or more and a haze is 0.3% or less. It is a film.
The invention according to claim 10 uses steel wool # 0000, damages the antifouling layer even after 10 reciprocations in an environment of a load of 1.5 kg / cm ² , a temperature of 25 ° C. and a humidity of 55% Rh. The antireflection film according to claim 7, wherein the antireflection film is not attached.

  According to the antireflection film prepared in the present invention, it is possible to produce an antireflection film having high transparency and excellent mechanical properties such as a scratch resistance test and a pencil hardness test.

It is sectional drawing which showed one Embodiment of the antireflection film of this invention.

  Embodiments of the present invention will be described below. FIG. 1 is a cross-sectional view showing an embodiment of the antireflection film of the present invention. In FIG. 1, an antireflection film 100 of the present invention has a hard coat layer 2, a primer layer 3, and an antireflection layer 4 sequentially laminated on a transparent substrate film 1. Further, an antifouling layer 5 is laminated on the antireflection layer 4.

  As the transparent substrate film 1 in the present invention, a polyethylene terephthalate (PET) film is used. The thickness of the transparent base film 1 may be appropriately selected according to the intended use, but usually a thickness of 70 μm or more and 200 μm or less is used. If the thickness is less than 70 μm, even if a hard coat layer is formed, the mechanical properties are weakened, which is not preferable.

  In the present invention, the PET film that is the transparent substrate film 1 may contain additives such as a plasticizer, an ultraviolet absorber, and an anti-deterioration agent, but it is necessary to select a highly transparent film. Therefore, an additive or the like in the form of a particle is not preferable because it lowers the light transmittance and the straightness of light and lowers the transparency. As far as possible, particulate additives inside should be avoided. In terms of handling, an easy-adhesion layer or the like is necessary, but it is necessary to coat the PET outside with as little surface roughness as possible. Further, the transparency of the film can be determined by the values of haze and light transmittance. In the present invention, a PET film having a haze of 0.5% or less is used. By using such a PET film, even when a hard coat layer and an antireflection layer are formed on the PET film, an antireflection film having high transparency can be obtained. In the present invention, it is preferable to use a PET film having a total light transmittance of 88% or more. By using such a PET film, even when a hard coat layer and an antireflection layer are formed on the PET film, an antireflection film having higher transparency can be obtained. Both haze and total light transmittance as used in the present invention are measured according to JIS K7136-2000.

  On the transparent substrate film 1, the hard coat layer 2 for sufficiently exhibiting the mechanical strength of the antireflection layer 4 is provided. As the hard coat layer 2 in the present invention, an ionizing ray or an ultraviolet curable resin is used. An acrylic resin such as an ultraviolet curable acrylic ester, acrylamide, methacrylic ester, methacrylamide, or an organic silicon type is used. Resins and polysiloxane resins are optimal. A polymerization initiator may be added to these materials in order to improve curability. When it has an easily bonding layer on the single side | surface of PET film, it is preferable to apply the hard-coat layer 2 to the easily bonding surface side. It has the effect of lowering the haze and further increasing the adhesion between the hard coat and the PET film. The thickness of the hard coat layer 2 is preferably 3 to 20 μm. When the thickness of the hard coat layer 2 is less than 3 μm, the mechanical strength is weak, and the thickness is not particularly problematic in terms of performance, but when it exceeds 20 μm, the warp of the film increases and the post-processability deteriorates.

In the antireflection film of the present invention, since the antireflection layer is extremely thin, the hardness of the entire antireflection film layer is easily affected by the hardness of the hard coat as the underlayer. Therefore, it is necessary to select a hard coat layer having as high mechanical strength as possible. In the present invention, when a hard coat layer surface is tested five times with a 3H pencil under a load of 500 g by a pencil hardness test (JIS K5400-1990), a hard coat layer that is not damaged by two or more is used. It is preferable. By using such a hard coat layer, even when an antireflection layer is formed on the hard coat layer, the antireflection film surface can have an antireflection film having sufficient scratch resistance.
In the present invention, the hard coat layer preferably has a haze of 0.4% or less and a total light transmittance of 89% or more. By using such a hard coat layer, even when an antireflection layer is formed on the hard coat layer, an antireflection film having high transparency can be obtained.

  Surface treatment may be applied to the hard coat layer 2 on the side opposite to the surface in contact with the transparent base film 1. At this time, examples of the surface treatment method include corona discharge treatment, electron beam treatment, flame treatment, glow discharge treatment, and atmospheric pressure plasma treatment. In the present invention, it is particularly preferable to perform a low temperature plasma surface treatment. By performing the low temperature plasma treatment, the hydrophilicity is improved and the surface is moderately roughened, thereby improving the adhesion with a thin film to be subsequently laminated.

  Thereafter, the primer layer 3 may be provided on the hard coat layer 2. Examples of the material of the primer layer 3 include metals such as silicon, nickel, chromium, tin, gold, silver, platinum, zinc, titanium, tungsten, aluminum, zirconium, and palladium, or alloys composed of two or more of these metals. Or oxides, fluorides, sulfides, nitrides and the like of these, which may be a mixture. Further, the primer layer 3 may have two or more layers.

  The primer layer 3 is used for improving adhesion. The thickness should just be a grade which does not impair the transparency of the transparent base film 1, Preferably, it is a physical film thickness and is about 1 nm or more and 10 nm or less. These primer layers are preferably formed by a dry coating method such as a sputtering method, a reactive sputtering method, a vapor deposition method, an ion plating method, or a chemical vapor deposition (CVD) method. In particular, a sputtering method is preferable.

  The antireflection layer 4 includes a single layer of a low refractive index transparent thin film layer having a light refractive index of less than 1.6 at a wavelength of 550 nm and a light extinction coefficient of 0.5 or less at a wavelength of 550 nm, or a wavelength of 550 nm. High refractive index transparent thin film layer having a light refractive index of 1.9 or higher, low refractive index transparent thin film layer having a light refractive index of less than 1.6, medium refractive index of light having a refractive index of about 1.6 to 1.9 Examples include a multi-layered optical thin film having a different refractive index such as a transparent thin film layer. A multi-layer antireflection layer is particularly preferable because it has a very low reflectance and high antireflection performance. The antireflection layer 4 of the present invention is composed of a laminate of four or more layers in which high refractive material layers and low refractive index layers are alternately laminated, and the outermost layer is a low refractive index layer. Specifically, as the antireflection layer 4, a high refractive index transparent thin film layer, a low refractive index transparent thin film layer, a high refractive index transparent thin film layer, and a low refractive index transparent thin film layer were laminated in order from the substrate side. The thing of composition is mentioned.

The antireflection layer 4 made of these optical thin film layers can be formed by a dry coating method such as sputtering, reactive sputtering, vapor deposition, ion plating, or chemical vapor deposition (CVD). It is preferable to use a sputtering method that has high film thickness uniformity and few defects such as pinholes, and that is excellent in visibility, dense, and capable of forming a thin film with excellent mechanical properties such as scratch resistance. Among them, the dual magnetron sputtering (DMS) method, in which film formation is performed by applying a voltage in the middle frequency region, is optimal because higher productivity can be obtained by higher film formation speed and higher discharge stability.
In addition, when employ | adopting sputtering method, it is preferable that the pressure at the time of lamination | stacking of an antireflection layer is 0.1-0.6 Pa. The reason is that a sufficient sputtering rate and film density can be obtained.

  As a material for the high refractive index transparent thin film layer, metals such as indium, tin, titanium, zinc, zirconium, niobium, magnesium, bismuth, cerium, tantalum, aluminum, germanium, potassium, antimony, neodymium, lanthanum, thorium, hafnium, Or the alloy which consists of 2 or more types of these metals, these oxides, fluoride, sulfide, nitride etc. are mentioned. Specific examples include titanium oxide, niobium oxide, zirconium oxide, tantalum oxide, zinc oxide, indium oxide, and cerium oxide, but are not limited thereto. In addition, when a plurality of layers are stacked, it is not always necessary to select the same material, and the material may be appropriately selected according to the purpose. In particular, when sputtering is used, niobium oxide is suitable because of the small number of pinholes in the thin film produced.

Examples of the material for the low refractive index transparent thin film layer include, but are not limited to, materials such as silicon oxide, magnesium fluoride, barium fluoride, calcium fluoride, hafnium fluoride, and lanthanum fluoride. Furthermore, when a plurality of layers are stacked, it is not always necessary to select the same material, and the material may be appropriately selected according to the purpose. In particular, silicon oxide is an optimal material in terms of optical characteristics, mechanical strength, cost, film formation appropriateness, and the like. In addition, silicon oxide (SiOx) here refers mainly to silicon dioxide (SiO ₂ ). However, when oxygen is deficient or increased, x of SiOx changes within a range of 1.8 to 2.2.
The total thickness of the antireflection layer is 100 to 300 nm. If it is less than 100 nm, sufficient reflection performance cannot be obtained, which is not preferable, and if it exceeds 300 nm, productivity is poor, which is not preferable.

  An antifouling layer 5 may be provided on the outermost surface layer on the antireflection layer 4 as necessary. The antifouling layer 5 can be a fluorine compound formed by a vacuum deposition method, and is a layer obtained from a fluorine-containing silicon compound having two or more silicon atoms bonded to a reactive functional group. preferable. The reactive functional group in the present invention means a group capable of reacting with and bonding to the uppermost layer of the antireflection layer 4. Moreover, it is a layer formed by making the reactive functional groups of a fluorine-containing silicon compound react. Thereby, it is hard to get dirt on the surface, and even if it gets dirty, the wiping performance can be improved. Here, the film formation method of the antifouling layer is not particularly limited, but a film formation method by vacuum vapor deposition is suitable. According to this method, when the film is continuously formed, it is possible to form the film with good uniformity of the film thickness.

At this time, in order to have sufficient antifouling performance, it is preferable that at least the water droplet contact angle is 100 ° or more. Thereby, the wiping property of the dirt on the surface is improved. Further, since the friction coefficient is lowered, the scratch resistance can be further improved. In addition, the antifouling layer of the present invention uses steel wool # 0000 and is not damaged even when rubbed 10 times in an environment of a load of 1.5 kg / cm ² , a temperature of 25 ° C., and a humidity of 55% Rh. Is particularly preferable from the viewpoint of scratch resistance.

  The antireflection film of the present invention thus obtained has a haze of 0.4% or less, a total light transmittance of 92% or more, and a luminous reflectance (JIS Z8701-1982) of 0.9% or less. Is preferred.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not limited to the following Example.

As shown in FIG. 1, a 100 μm thick PET film was used for the transparent substrate film 1, an ultraviolet curable acrylic resin was applied, dried and UV cured, and a hard coat layer 2 having an arbitrary thickness was provided. Glow plasma treatment is performed, and the primer layer 3 is formed by sputtering to form a SiO layer with a film thickness of 3 nm, and then the antireflection layer 4 is formed by sputtering and under any deposition pressure condition. Nb ₂ O ₅ / SiO ₂ / Nb ₂ O ₅ / SiO ₂ from the hard coat side, and the film thickness of each layer was 15 nm / 25 nm / 105 nm / 85 nm, respectively.

[Example 1]
A PET film having a haze of 0.34% and a total light transmittance of 93.4% was used as the transparent substrate film. The hard coat layer has a thickness of 5 μm, a haze of 0.35%, a total light transmittance of 94.2%, and a pencil hardness test of 5/5 under a load of 3H and a load of 500 g. The antireflection layer was formed under a pressure forming condition of 0.3 Pa for the antireflection layer.

[Example 2]
A PET film having a haze of 0.27% and a total light transmittance of 90.4% was used for the transparent substrate film. The hard coat layer has a thickness of 4 μm, a haze of 0.2%, a total light transmittance of 89.9%, a pencil hardness of 3H, 500 g overload and 4/5. The antireflection layer was formed under a pressure forming condition of 0.3 Pa for the antireflection layer.

[Comparative Example 1]
A PET film having a haze of 1.0% and a total light transmittance of 89% was used as the transparent substrate film. The hard coat layer has a thickness of 5 μm, a haze of 0.95%, a total light transmittance of 89.5%, and a pencil hardness test of 5/5 under a load of 3H and a load of 500 g. The antireflection layer was formed at a film formation pressure of 0.3 Pa.

[Comparative Example 2]
A PET film having a haze of 0.27% and a total light transmittance of 90.4% was used for the transparent substrate film. The hard coat layer has a thickness of 3 μm, a haze of 0.18%, a total light transmittance of 90.3%, and a pencil hardness test of 2/5 at 2H under a load of 500 g. The antireflection layer was formed at a film formation pressure of 0.3 Pa.

  Thereafter, an antifouling layer was formed by vacuum deposition.

[Evaluation]
Samples obtained in Examples and Comparative Examples were evaluated by the following methods. The results are shown in Table 1.

(Optical property evaluation)
(1) Luminous reflectance measurement Measurement was carried out using a U4000 type spectrophotometer manufactured by Hitachi, Ltd. The back side of the sample was subjected to a treatment for cutting off reflection from the back side with a matte black paint spray, and a specular reflection 5 ° unit was used for the measurement.
The luminous reflectance was measured according to JIS Z8701-1982.

(2) Haze and total light transmittance measurement Measurement was carried out using NDH-2000 manufactured by Nippon Denshoku. At this time, incident light was incident from the antifouling layer (antireflection layer) side.
Both haze and total light transmittance were performed in accordance with JIS K7136-2000.

(Mechanical property evaluation)
(3) Scratch resistance test Steel wool # 0000 is fixed to a scratch tester, a load of 500,1000 gf is applied, and a 10-round scratch test is performed on the antireflection layer of each sample. The number of scratches) was visually observed. Judgment criteria are shown below.
◎: No scratch ○: Less than 10 scratches ×: 10 or more scratches

(4) Pencil hardness test A load of 500 gf was applied to an arbitrary pencil, the film was traced five times, and the abrasion state (number of scratches) of the sample was visually observed. If 5 lines are drawn and there are no flaws, 5/5 is indicated. If there are 5 flaws, 0/5 is indicated. Judgment criteria are shown below. The pencil used was 2H-3H.
A: 5/5, 4/5
○: 3/5
Δ: 2/5
X: 1/5, 0/5

  Also for the antireflection films prepared in Comparative Examples 1 and 2, since the film is formed by the sputtering method, a precise optical design is possible and sufficient antireflection performance can be obtained. However, it can be seen that each evaluation item is inferior. On the other hand, when the antireflection film prepared in Examples 1 and 2 was used, good results could be obtained in optical properties, mechanical properties, and all performances. Thereby, it can confirm that it has the outstanding antireflection function, the outstanding mechanical characteristic, and the outstanding environmental durability.

DESCRIPTION OF SYMBOLS 1 Transparent base film 2 Hard-coat layer 3 Primer layer 4 Antireflection layer 5 Antifouling layer 100 Antireflection film

Claims (10)

An antireflection film obtained by sequentially laminating at least a hard coat layer and an antireflection layer on at least one surface of a transparent substrate film, wherein the antireflection layer comprises a high refractive material layer and a low refractive index layer. Reflection comprising four or more layers laminated alternately, the outermost layer of the antireflection layer being a low refractive index layer and satisfying all the following conditions (1) to (4) Prevention film.
(1) Transparent base film: A polyethylene terephthalate film having a thickness of 70 μm to 200 μm and a haze of 0.5% or less is used.
(2) Hard coat layer: A photocurable resin having a thickness of 3 μm to 20 μm is used.
(3) Antireflection layer: The total thickness is 100 to 300 nm.
(4) Antireflection film: haze is 0.4% or less, total light transmittance is 92% or more, and luminous reflectance is 0.9% or less.   2. The antireflection film according to claim 1, wherein the total light transmittance of the (1) transparent substrate film is 88% or more.   (2) The hard coat layer has a haze of 0.4% or less, a total light transmittance of 89% or more, and a pencil hardness test (JIS K5400-1990). The antireflection film according to claim 1 or 2, wherein two or more scratches are not scratched when the surface of the coating layer is tested five times.   4. The antireflection layer according to claim 1, wherein the low refractive index layer is silicon oxide and the high refractive index layer is niobium oxide, and is laminated by a dry coating method using a sputtering method. An antireflection film according to claim 1.   The antireflection film according to claim 4, wherein a pressure applied when the antireflection layer is laminated by the sputtering method is 0.1 to 0.6 Pa.   Between the hard coat layer and the antireflection layer, a primer layer made of a metal, an alloy made of two or more metals, a metal compound, or a mixture thereof was provided. The antireflection film according to any one of claims 1 to 5.   The antireflection film according to any one of claims 1 to 6, wherein an antifouling layer is provided on the antireflection layer.   8. The antireflection film according to claim 7, wherein the antifouling layer is a fluorine compound formed by a vacuum vapor deposition method.   The antireflection film according to claim 7 or 8, wherein a water droplet contact angle on the antifouling layer side surface is 100 ° or more and a haze is 0.3% or less. A steel wool # 0000 is used, and the antifouling layer is not damaged even after 10 reciprocations in an environment of a load of 1.5 kg / cm ² , a temperature of 25 ° C. and a humidity of 55% Rh. Item 10. The antireflection film according to any one of Items 7 to 9.

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