JP2009222852A - Antireflection film - Google Patents

Abstract

To provide an antireflection film for use in an optical display device such as an LCD and the like by a dry coating method having both an antireflection effect and chemical resistance.
An antireflection laminate is formed on at least one surface of a transparent substrate film, and the antireflection laminate comprises a high refractive index thin film and a low refractive index thin film from the transparent substrate film side. An antireflection film comprising a laminate having an odd number of layers of 5 or more alternately laminated in order, wherein the outermost high refractive index layer is zirconium oxide.
[Selection] Figure 1

Description

The present invention relates to an antireflection film by a dry coating method.

In an optical display device such as an LCD, an antireflection laminate is used for the purpose of improving visibility due to the spread of mobile devices such as digital cameras, mobile phones, and digital video cameras, and car navigation.
As such an antireflection laminate, a laminate in which a low refractive index thin film and a high refractive index thin film are laminated is widely used. Moreover, the outermost layer is almost always a low refractive index thin film in optical design, and silicon oxide is widely used as the material. However, in recent years, the chemical resistance of the antireflection laminate has also become important, and an antireflection laminate having high alkali resistance is desired. However, the compatibility between the antireflection effect and the chemical resistance is not always sufficient, and further improvement is required.
Japanese Patent Laid-Open No. 5-34505 JP-A-2005-70616

Specifically, the present invention has been made to provide an antireflection film having both an antireflection effect and chemical resistance.

  In the first aspect of the present invention, an antireflection laminate is formed on at least one surface of the transparent substrate film, and the antireflection laminate is formed of a high refractive index thin film from the transparent substrate film side. An antireflection film comprising a laminate having an odd number of layers of five or more layers in which low refractive index thin films are alternately laminated in this order, wherein the outermost high refractive index layer is zirconium oxide.

  The present invention described in claim 2 is the antireflection film according to claim 1, wherein the low refractive index thin film is silicon oxide, and the high refractive index thin film other than the outermost layer is niobium oxide.

  The present invention according to claim 3 is the antireflection film according to claim 1 or 2, wherein the thickness of the outermost high refractive index layer is 10 nm or more and 30 nm or less.

  According to the present invention, it is possible to provide an antireflection film having chemical resistance without impairing the antireflection effect.

  In FIG. 1, the cross-sectional schematic diagram which shows a structure of an example of the electroconductive antireflection film of this invention of this invention was shown. The antireflection film 8 of the present invention shown in FIG. 1 is provided with a hard coat layer 1-b on a transparent substrate film 1, and an antireflection laminate 7 is laminated on the hard coat layer 1-b. In the antireflection laminate 7, the first high refractive index thin film 2, the first low refractive index thin film 3, the second high refractive index thin film 4, and the second low refractive index are sequentially formed from the transparent base film 1 side. An index thin film 5 and a third high refractive index thin film 6 are provided. The present invention is characterized in that the third high-refractive-index thin film 6 which is the outermost layer in this case is zirconium oxide.

In the antireflection film of the present invention, the first high refractive index thin film 2 and the first low refractive index thin film 3 are used.
High antireflection performance can be obtained by forming an antireflection laminate having a structure of five or more layers, comprising the second high refractive index thin film 4, the second low refractive index thin film 5, and the third high refractive index thin film 6 in this order. It can be set as the antireflection film which has.

  In the antireflection film of the present invention, the outermost layer (third high refractive index thin film) of the antireflection laminate is a high refractive index layer made of zirconium oxide, whereby an antireflection film having high alkali resistance, We were able to.

  Usually, in an antireflection film, when antireflection performance is exhibited by a laminated structure of a high refractive index thin film and a low refractive index thin film, a low refractive index thin film made of silicon oxide may be provided as the outermost layer. Many. However, the silicon oxide thin film has insufficient alkali resistance, and the resulting antireflection laminate has low alkali resistance. Therefore, the present inventors have formed an antireflection film having not only high antireflection performance but also high alkali resistance by forming a high refractive index thin film made of zirconium oxide as the outermost layer of the antireflection laminate. I was able to.

  In the antireflection film of the present invention, the thickness of the high refractive index thin film made of zirconium oxide as the outermost layer is preferably in the range of 10 nm to 30 nm. When the thickness of the high refractive index thin film made of zirconium oxide as the outermost layer is less than 10 nm, an antireflection film having sufficient alkali resistance may not be obtained. On the other hand, when the thickness of the high refractive index thin film made of zirconium oxide as the outermost layer exceeds 30 nm, an antireflection film having sufficient antireflection performance may not be obtained.

  In the antireflection film of the present invention, the low refractive index thin film (first low refractive index thin film, second low refractive index thin film) has aspects such as optical characteristics, mechanical strength, film forming suitability, and cost. Therefore, silicon oxide can be preferably used. Further, niobium oxide can be suitably used for the high refractive index thin films (the first high refractive index thin film and the second high refractive index thin film) other than the outermost layer because there are few defects in the film.

  In addition, in the antireflection film of the present invention, it is sufficient that five or more high refractive index thin films and low refractive index thin films are alternately provided in order from the transparent base film side. In this order, a seven-layer structure of a high refractive index thin film, a low refractive index thin film, a high refractive index thin film, a low refractive index thin film, a high refractive index thin film, a low refractive index thin film, and a high refractive index thin film may be used. However, considering the manufacturing cost, the antireflection film of the present invention is preferably an antireflection film having an antireflection laminate having a five-layer structure as shown in FIG.

  Moreover, in the antireflection film of the present invention, a hard coat is provided as necessary.

  The transparent substrate film 1 may be a film having transparency, but in an antireflection film for an optical display device, triacetyl cellulose (TAC), polyethylene tetephthalate (PET), polyethylene naphthalate (PEN) Films such as acrylic are used because of their optical properties and mechanical properties. In particular, TAC films are used for LCD applications that have rapidly spread. In other applications, PET films are widely used. The thickness of the transparent substrate film 1 may be appropriately selected according to the intended use, but usually a film having a thickness of about 25 to 300 μm is used from the viewpoint of mechanical strength and handling properties and optical device design. To do. Furthermore, the transparent substrate film 1 may contain additives such as a plasticizer, an ultraviolet absorber, and a deterioration inhibitor, if necessary.

A hard coat layer may be formed on at least one surface on the transparent substrate film 1.
When this hard coat layer is formed between the transparent substrate film 1 and the antireflection laminate, it is for the purpose of improving adhesion and when it is formed on the opposite surface, it is protected by improving mechanical strength. There is a purpose of adding functions. The hard coat is made of ionizing radiation, UV curable resin or thermosetting resin, and UV curable acrylic esters, acrylamides, methacrylic esters, methacrylamide, etc. Resin and polysiloxane resin are most suitable. A polymerization initiator may be added to these materials in order to improve curability. The thickness of the hard coat layer is 0.5 μm or more, preferably 3 to 20 μm. Further, the hard coat layer 1-b may be subjected to an antiglare treatment (a treatment for artificially reducing reflected light by scattering) by dispersing transparent fine particles having an average particle size of 0.01 to 3 μm.

  Before forming the antireflection laminate, surface treatment may be performed for the purpose of improving the adhesion strength. At this time, examples of the surface treatment method include corona discharge treatment, glow discharge treatment, ion beam treatment, atmospheric pressure plasma treatment, and saponification treatment.

  When it is necessary to further improve the adhesion strength, a primer layer may be provided after the surface treatment and before the formation of the antireflection laminate. As a material of the primer layer, for example, a metal such as silicon, nickel, chromium, tin, gold, silver, platinum, zinc, titanium, tungsten, zirconium, palladium, or an alloy composed of two or more of these metals, or These oxides, fluorides, sulfides, nitrides and the like can be mentioned. In particular, for example, a primer layer such as Si or SiOx using silicon is excellent as a primer layer of an antireflection laminate using an oxide thin film. 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. Further, the thickness of the primer layer may be determined according to the purpose, but the range of about 1 to 20 nm is preferable, and the primer layer has a thickness that does not affect the optical properties of the antireflection laminate to be formed. It is preferable to be provided.

  In the antireflection film of the present invention, the antireflection laminate provided on the transparent substrate film is preferably formed by a sputtering method. The antireflection laminate of the present invention is formed by a dry coating method (vacuum film forming 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. At this time, the formed thin film has high film thickness uniformity and has few defects such as pinholes, so that it can be made a thin film with excellent visibility, and the formed thin film is dense and has scratch resistance, etc. It is preferable to use a sputtering method capable of forming a thin film having excellent mechanical properties. 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.

  As a material for the high refractive index thin film, niobium oxide, titanium oxide, indium oxide, tin oxide, zinc oxide, zirconium oxide, tantalum oxide, hafnium oxide, or a mixture thereof, or a low refractive index material such as silicon oxide. And a mixture thereof. In particular, niobium oxide and titanium oxide having a high refractive index are widely used for antireflection film applications. Among these, niobium oxide is suitable for sputtering because of its small number of defects in the thin film.

Examples of the material used for the low refractive thin film include silicon oxide, titanium nitride, magnesium fluoride, barium fluoride, calcium fluoride, hafnium fluoride, lanthanum fluoride, and the like, which are appropriately selected according to the purpose. ing. Among these, silicon oxide is most suitable from the viewpoint of its optical characteristics, mechanical strength, suitability for film formation, cost, and the like.
Zirconium oxide used for the outermost high-refractive-index thin film layer has excellent chemical resistance, particularly alkali resistance, for example, when compared with silicon oxide. The refractive index is about 2, although it depends on the manufacturing method. The thickness is not particularly limited depending on the purpose. However, 30 nm or less is desirable in order to obtain a sufficient antireflection effect. On the other hand, 10 nm or more is desirable to obtain a sufficient chemical resistance effect.

Hereinafter, an example of an embodiment of the antireflection film of the present invention will be described using examples.
[Common conditions for Examples and Comparative Examples]
A TAC film having a thickness of 80 μm is used as the transparent base film 1, and an ultraviolet curable acrylic resin is applied in advance to the surface on which the antireflection laminate 7 is formed, followed by drying and UV curing, and a hard coat layer having a thickness of about 5 μm. 1-b was provided as a transparent base film with a hard coat. Thereafter, the surface of the hard coat layer was treated by glow discharge. Thereafter, a silicon layer of about 5 nm or less was provided as a primer layer by a sputtering method. Thereafter, the antireflection laminate 7 was formed by a dual magnetron sputtering method. Silicon oxide was used for the low refractive index thin film. Niobium oxide was used for the high refractive index thin film other than the outermost layer.

[Example 1]
The structure of the antireflection laminate is a five-layer structure, and from the transparent base film side, niobium oxide (15 nm) / silicon oxide (33 nm) / niobium oxide (65 nm) / silicon oxide (49 nm) / zirconium oxide (20 nm) did.

[Example 2]
The structure of the antireflection laminate is a five-layer structure, and from the transparent substrate film side, niobium oxide (18 nm) / silicon oxide (39 nm) / niobium oxide (47 nm) / silicon oxide (78 nm) / zirconium oxide (10 nm) did.

[Example 3]
The structure of the antireflection laminate is a five-layer structure, and from the transparent base film side, niobium oxide (12 nm) / silicon oxide (39 nm) / niobium oxide (65 nm) / silicon oxide (43 nm) / zirconium oxide (25 nm) did.

[Comparative Example 1]
In order to confirm the effect of the example, an antireflection laminate having an outermost layer of a low refractive index layer was produced as a comparative example. The structure of the antireflection laminate was a four-layer structure, and from the transparent base film side, niobium oxide (22 nm) / silicon oxide (33 nm) / niobium oxide (49 nm) / silicon oxide (99 nm).

[Evaluation]
The obtained sample was evaluated by the following method.
(1) Reflectance Y
Measurements were made using a Hitachi U4000 spectrophotometer. A regular reflection unit of 5 ° was used. Color calculation was performed with a 2 ° field of view and a D65 light source. The results are shown in Table 1.
(2) Chemical resistance As an evaluation of chemical resistance, alkali resistance was examined. One drop of a 5% aqueous solution of NaOH was deposited on the antireflective laminate, allowed to stand for 30 minutes, wiped off, and the appearance change was visually observed. The case where there was no change was marked with ◯, the slight change was marked with Δ, and the big change was marked with ×. The results are shown in Table 1.

前記実施例および比較例の結果、本発明の実施例の反射防止フィルムは、比較例の反射防止フィルムと比べて、反射防止効果を充分保ち、耐薬品性が向上していることが確認でき
た。

As a result of the examples and comparative examples, it was confirmed that the antireflection film of the examples of the present invention sufficiently maintained the antireflection effect and improved the chemical resistance compared to the antireflection film of the comparative example. .

It is a cross-sectional schematic diagram which shows the structural example of the antireflection film of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transparent base film 1-b ... Hard coat 2 ... High refractive index thin film 3 ... Low refractive index thin film 4 ... High refractive index thin film 5 ... Low refractive index thin film 6 ... High refractive index thin film 7 ... Antireflection laminated body 8 ... Antireflection film

Claims (3)

An antireflective laminate is formed on at least one surface of the transparent substrate film, and the antireflective laminate is alternately laminated with a high refractive index thin film and a low refractive index thin film in this order from the transparent substrate film side. An antireflection film comprising an odd-numbered laminate of five or more layers, wherein the outermost high refractive index layer is zirconium oxide 2. The antireflection film according to claim 1, wherein the thickness of the outermost high refractive index thin film is 10 nm or more and 30 nm or less. The antireflective film according to claim 1 or 2, wherein the low refractive index thin film is silicon oxide and the high refractive index thin film other than the outermost layer is niobium oxide.

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