JP2006010929A - High reflector - Google Patents

Abstract

[PROBLEMS] To provide a highly reflective mirror having high reflectivity in the visible light region, excellent in durability such as moisture resistance and salt water resistance, and having a small incident angle dependency (the reflectivity hardly varies depending on the incident angle of light). Provided.
A high-reflection mirror in which a silver film, a low-refractive index film, and a high-refractive index film are stacked in this order on a substrate, and each incident angle is 15 degrees, 45 degrees, and 75 degrees. A high-reflecting mirror characterized in that the deviation of the minimum value of the film surface reflectance over the entire visible light region is within 7%. An adhesion improving film may be formed on the opposite side of the silver film from the substrate.
[Selection] Figure 1

Description

  The present invention relates to a high-reflecting mirror mainly used in a backlight module for a small liquid crystal display such as a projection television or a mobile phone.

  Conventionally, a mirror using a metal film for reflection is widely used as a reflecting mirror used in an electronic device such as a flat panel display. It is important to increase the reflectivity of the reflecting mirror in order to improve the luminance and save energy of electronic equipment. For example, a liquid crystal display used for a mobile phone or the like uses a mirror that reflects a backlight, but this mirror uses a film as a substrate for weight reduction, and a reflector having a high reflectance is required. . Further, in order to display an image on a large screen such as a projection television, a plurality of reflecting mirrors are necessary in the optical system, so that the amount of light decreases as the number of reflections increases. As a result, there is a problem that the amount of light finally obtained is reduced and the luminance of the screen is lowered, and a reflector having a higher reflectance than the conventional one is required.

  Conventionally, aluminum is used as a material for a metal film. However, when aluminum is used as the material of the metal film, the reflectance varies depending on the incident angle of light, resulting in a problem that the reflected color varies.

  In order to solve the above problems, silver having a higher reflectance in the visible light region than aluminum is used as a material for the metal film. However, although silver has a higher reflectance in the visible light range than aluminum, it has poor durability such as moisture resistance and salt water resistance due to poor adhesion to the substrate, and it is easily damaged due to weak film strength. There was a problem.

As a mirror having high reflectivity and excellent durability, an Al ₂ O ₃ film, an Ag film, an Al ₂ O ₃ film, and a TiO ₂ film are sequentially laminated on a glass substrate as a metal film using an Ag film. A reflecting mirror is disclosed (for example, refer to Patent Document 1). However, this high reflecting mirror has a problem that since oxygen is introduced when an Al ₂ O ₃ film opposite to the substrate of the Ag film is produced, silver is easily oxidized and the reflectance is lowered.

  Also, a reflective film in which a metal such as Ce or Nd is mixed with Ag in order to improve the adhesion between the Ag film and the substrate is disclosed (for example, see Patent Document 2). However, since this reflective film is a single silver film, only the adhesion between the Ag film and the substrate is described, and the adhesion between the Ag film and other layers is not evaluated at all.

In addition, a reflecting mirror in which an Al ₂ O ₃ film, a ZrO ₂ film, and an SiO ₂ film are formed on an Ag film is disclosed (for example, see Patent Document 3). Here, it is described that the Al ₂ O ₃ film is a protective film for increasing the durability of the Ag film, the ZrO ₂ film is a film for improving the reflection efficiency, and the SiO ₂ film is a protective film. Yes. Moreover, in order to improve the adhesiveness of a board | substrate and Ag film | membrane, forming the film | membrane which consists of chromium oxide between a base material and Ag film | membrane is disclosed (for example, refer patent document 4). In addition, an Al ₂ O ₃ film is formed on the Ag film, and a layer of zirconium oxide, silicon dioxide, titanium oxide, hafnium oxide, tin oxide, antimony oxide, tungsten oxide, or the like is provided to further improve durability. (For example, refer to Patent Document 5). Further, it is disclosed that a base film made of silicon oxide is provided between a substrate and an Ag film in order to improve durability (for example, refer to Patent Document 6). However, these reflective films have a problem in that the reflectance in the visible light region is low.

JP 2003-4919 A JP 2002-226927 A JP-A-5-127004 JP 2000-81505 A JP 2000-241612 A Japanese Patent Laid-Open No. 2001-74922

  The present invention has a high reflectivity in the visible light region, is excellent in durability such as moisture resistance and salt water resistance, and has a small incident angle dependency (the reflectivity hardly varies depending on the incident angle of light). An object of the present invention is to provide a high-reflecting mirror having a high reflectance with respect to incident light.

The present invention provides the following configuration.
A high-reflection mirror in which a silver film, a low-refractive index film, and a high-refractive index film are laminated in this order on a substrate, and the film surface reflection in each case of incident angles of 15 degrees, 45 degrees, and 75 degrees A high-reflection mirror characterized in that the deviation of the lowest value of the rate in the entire visible light range is within 7%.

  The high reflection mirror of the present invention uses silver as the material of the metal film, so that the reflectance in the visible light region can be increased, and further, since it is excellent in durability, it is useful as an optical component for display. It also contributes to brightness improvement and easy optical design. In addition, since the incident angle dependency is small, it is particularly useful as an optical component for a rear projection television having a large number of reflections. Further, since it has a high reflectance regardless of the incident angle of light, it is particularly useful as a backlight module for a liquid crystal display.

  In addition, since the reflectance with respect to obliquely incident light is particularly high, the decrease in reflectance is very small even when the angle of reflection is increased, and when used for optical components for projection televisions, the housing can be made small and useful.

In the high reflection mirror of the present invention, the type of the substrate is not particularly limited, and examples thereof include 1) glass such as soda lime glass, 2) PET (polyethylene terephthalate) resin, acrylic resin, polycarbonate film, and the like. It is preferable to use glass because it is difficult to warp or bend even if it has a large area, and it is preferable to use a film because the weight can be reduced. When the substrate is made of glass, the thickness of the substrate is preferably 0.5 to 8.0 mm in view of the strength and ease of use of the high reflector. When a board | substrate is a film, it is preferable at the point which can be reduced in weight that it is 30-500 micrometers. The shape of the substrate is not particularly limited as long as it is a shape required as a base for various reflecting optical members such as a plane mirror, a concave mirror, a convex mirror, and a trapezoidal mirror. When the high-reflection mirror of the present invention is formed by a sputtering method, the film formed by the sputtering method is superior to the film formed by the vapor deposition method or the like, so that the film can be formed on a large substrate. Is possible. For example, even a substrate having a large area such as an area of 0.1 to ⁵ m ² can be formed, so that it is particularly useful as an optical component for a projection TV having a large area.

  The silver film that reflects light effectively is a film containing silver as a main component, and preferably contains 90 at% or more of silver from the viewpoint of reflectance in the visible light region. By using a silver film, the reflectance in the visible light region can be increased, and the dependence of the reflectance on the incident angle can be reduced. The silver film may contain impurities such as copper, but the content is preferably 10 at% or less. In the present invention, the “visible light region” means a wavelength region of 400 to 800 nm.

  The silver film may be an alloy film of silver and other metals. Specific examples of other metals include Au. An alloy film with Au is preferable because the durability of the silver film is improved. The content of other metals in the alloy film is preferably 0.5 to 10 at% from the viewpoint of improving durability. Further, the silver content in the alloy film is preferably 90 at% or more from the viewpoint of the reflectance in the visible light region.

  The geometric film thickness (hereinafter simply referred to as film thickness) of the silver film is preferably 60 to 200 nm, and particularly preferably 80 to 120 nm. If it is less than 60 nm, the reflectance in the visible light region is lowered, and if it exceeds 200 nm, light absorption occurs due to surface irregularities, resulting in a decrease in the reflectance in the visible light region.

  The low refractive index film of the present invention preferably has a refractive index of 1.35 to 1.75 at a wavelength of 550 nm. Further, the low refractive index film needs to be a transparent film from the viewpoint of reflectivity, and specifically has an extinction coefficient in the visible light region (hereinafter simply referred to as an extinction coefficient) of 0.01 or less. 0.008 or less, and particularly preferably 0.005 or less. Specifically, the material of the low refractive index film is preferably an oxide such as silicon oxide in terms of a small change in optical characteristics. The film thickness of the low refractive index film is preferably 25 to 60 nm, particularly 28 to 45 nm, from the viewpoint of obtaining an optimum reflectance. Further, when the low refractive index film is a silicon oxide film, the silicon content of the silicon oxide film is 90% by mass or more based on the total metal and semiconductor elements in the silicon oxide film. It is preferable at the point which can obtain the film | membrane which has. The silicon oxide film may contain another metal such as aluminum. Here, the refractive index means the real part of the complex refractive index, and the extinction coefficient means the imaginary part of the complex refractive index in the visible light region. Each of them is a spectroscopic ellipsometer (for example, VASE: JA Woollam). Manufactured).

  The low refractive index film may be a single layer or a plurality of layers. In the case of a plurality of layers, it is preferable that all the layers have a refractive index of 1.35 to 1.75 at a wavelength of 550 nm. Even if the low refractive index film has a plurality of layers, it is necessary to be transparent, and the extinction coefficient of all the layers is 0.01 or less, preferably 0.008 or less, particularly preferably 0.005 or less. Further, the total thickness of the plurality of layers is preferably 25 to 60 nm, particularly 28 to 45 nm, from the viewpoint of obtaining an optimum reflectance.

  The high refractive index film of the present invention preferably has a refractive index of 1.8 to 2.8 at a wavelength of 550 nm. Further, the high refractive index film needs to be a transparent film from the viewpoint of reflectivity, and specifically has an extinction coefficient of 0.01 or less, 0.008 or less, particularly 0.005 or less. Is preferred. Specifically, the material for the high refractive index film is preferably at least one selected from the group consisting of niobium oxide, zirconium oxide, tantalum oxide, hafnium oxide, titanium oxide and tin oxide from the viewpoint of reflectivity. Niobium oxide is particularly preferable because it has a high refractive index, a low absorption rate, and a high film formation rate. The material for the high refractive index film may be a complex oxide. The film thickness of the high refractive index film is preferably 30 to 65 nm, particularly 40 to 65 nm, from the viewpoint of obtaining an optimum reflectance. When the high refractive index film is a niobium oxide film, the niobium oxide film has a niobium content of 90% by mass or more based on the total metal elements in the niobium oxide film to obtain a desired refractive index film. It is preferable at the point which can do.

  The high refractive index film may be a single layer or a plurality of layers. When it consists of multiple layers, it is preferable that all the layers have a refractive index of 1.8 to 2.8 at a wavelength of 550 nm. Even if the high refractive index film has a plurality of layers, it is necessary to be transparent, and the extinction coefficient of all the layers is 0.01 or less, preferably 0.008 or less, particularly preferably 0.005 or less. Further, the total thickness of the plurality of layers is preferably 30 to 65 nm, particularly 40 to 65 nm, from the viewpoint of obtaining an optimum reflectance.

  In the present invention, an example in which a low refractive index film and a high refractive index film are laminated once in this order has been described. However, not only once but a plurality of low refractive index films and high refractive index films are arranged in this order. You may laminate | stack. By laminating a plurality of times, it is possible to form a high-reflecting mirror with further improved reflectivity. Furthermore, as a layer farthest from the substrate, another layer for improving durability can be formed.

  In the high reflection mirror of the present invention, a base film may be formed on the substrate side of the silver film. By forming the base film, the adhesion between the silver film and the substrate can be improved, and a highly reflective mirror with excellent durability can be obtained. The material of the base film is preferably at least one selected from the group consisting of oxides, oxynitrides and nitrides from the viewpoint of adhesion between the substrate and the silver film, specifically zinc oxide, oxide It is preferably at least one selected from the group consisting of tin, indium oxide, aluminum oxide, titanium oxide, niobium oxide and chromium oxide. In addition, since silicon oxide has poor adhesion to silver, it can be used as a base film as long as the silicon oxide film and the silver film are not in contact with each other. Further, the material of the base film may be a complex oxide. The film thickness of the base film is preferably 1 to 20 nm, particularly 2 to 10 nm, and more preferably 3 to 7 nm. If the thickness is less than 1 nm, the effect of improving the adhesion is hardly exhibited, and if it exceeds 20 nm, the surface unevenness becomes large and the reflectance becomes low. Further, the base film may be a single layer or a plurality of layers. In the case of a plurality of layers, the total film thickness is preferably in the above range.

  When the base film is a zinc oxide film, the zinc content in the zinc oxide film is preferably 90% by mass or more based on the total metal elements in the zinc oxide film. The zinc oxide film may contain other metals. By containing another metal, the adhesion between the substrate and the silver film can be further improved. Examples of the other metal include aluminum, gallium, tin, titanium, silicon, and the like, and the content thereof is 2 to 10% by mass in terms of oxide, which can improve the adhesion between the substrate and the silver film. Is preferable.

  In the high reflection mirror of the present invention, it is preferable to provide an adhesion improving film on the side opposite to the silver film substrate. The adhesion improving film can prevent oxidation of the silver film, contribute to improvement of moisture resistance of the high reflector, and improve the adhesion between the low refractive index film and the silver film. The adhesion improving film is preferably a transparent film from the viewpoint of reflectance. Specifically, the extinction coefficient is 0.1 or less, preferably 0.05 or less, particularly preferably 0.02 or less. . The material of the adhesion improving film is an oxide having an extinction coefficient of 0.1 or less from the viewpoint of adhesion between the substrate and the silver film, and specifically includes zinc oxide, tin oxide, indium oxide, aluminum oxide, and oxide. It is preferably at least one selected from the group consisting of titanium. In addition, since silicon oxide has poor adhesion to silver, it can be used as a base film as long as the silicon oxide film and the silver film are not in contact with each other. The material of the adhesion improving film may be a complex oxide, and examples thereof include ATO and ITO. The film thickness of the adhesion improving film is preferably 3 to 14 nm, particularly 4 to 12 nm, and more preferably 4 to 6 nm. If the thickness is less than 3 nm, the effect of improving adhesion and preventing oxidation hardly appears, and if it exceeds 14 nm, the surface unevenness becomes large and the reflectance becomes low, which is not preferable. The adhesion improving film may be a single layer or a plurality of layers. In the case of a plurality of layers, the total film thickness is preferably in the above range.

  When the adhesion improving film is a zinc oxide film, the zinc content in the zinc oxide film is preferably 90% by mass or more based on the total metal elements in the zinc oxide film. The zinc oxide film may contain other metals. By containing another metal, the adhesion between the substrate and the silver film can be further improved. Specific examples of the other metal include one or more selected from the group consisting of gallium, tin, silicon and titanium, and the content of the other metal is 3 to 10% by mass in terms of oxide. It is preferable in terms of stress relaxation. As another metal, aluminum is not preferable in that it has absorption in the visible light region.

  In the case where the adhesion improving film is a zinc oxide film containing one or more selected from the group consisting of gallium, tin and titanium (hereinafter referred to as GSTZO film), it may further contain silicon. By containing silicon, the film is hardly reduced, and a film having stable optical characteristics can be formed. The silicon content in the GSTZO film is preferably 0.05 to 1% by mass with respect to the total metal elements in the GSTZO film.

  Furthermore, it is preferable to form an antioxidant film on the opposite side of the adhesion improving film from the substrate. By forming the antioxidant film, oxidation of the silver film can be prevented more effectively, and the reflectance can be further increased. The antioxidant film preferably has an extinction coefficient of 0.01 or less, particularly 0.001 or less in terms of reflectance and adhesion. Further, it is preferable that oxidation occurs on the surface and oxygen does not diffuse into the inside. Considering the above points, the material of the antioxidant film is preferably one or more oxides selected from the group consisting of aluminum, yttrium, zirconium, and hafnium, or aluminum nitride or oxynitride. The material of the antioxidant film may be silicon nitride. Moreover, since the refractive index after oxidation is preferably smaller than 1.8 in that the reflectance does not decrease, the material of the antioxidant film is preferably aluminum oxide. The antioxidant film may be a single layer or a plurality of layers. Aluminum may be doped with a metal such as Mg, Si, or Zr.

  In particular, when the adhesion improving film is a film having a slight absorption (for example, a GSTZO film), the adhesion to the silver film is sufficient, but the reflectance of the high reflector is small due to the absorption of the adhesion improving film. Also decreases. Therefore, it is preferable to form the adhesion improving film with a thin film thickness (for example, 1 to 3 nm) and further form an antioxidant film with little absorption on the film because the reflectance can be further improved.

  When the antioxidant film is an aluminum oxide film, as a method of forming the aluminum oxide film, the aluminum film is first formed, and then the aluminum film is oxidized by oxygen present in the tank when the upper film is formed. A method of forming an aluminum oxide film is exemplified. The above method is preferable because an aluminum film can be formed in an oxygen-free atmosphere and oxidation of the silver film can be prevented. Moreover, even if an aluminum film is formed, it is preferable because good adhesion is maintained. The film thickness of the aluminum oxide film is preferably 0.5 to 6 nm, particularly preferably 0.5 to 3 nm.

  When the antioxidant layer is an aluminum nitride film, examples of the method for forming the aluminum nitride film include a method of forming an aluminum nitride film by forming aluminum while containing nitrogen in the tank. The film thickness of the aluminum nitride film is preferably 0.5 to 10 nm.

  In particular, it is particularly preferable to use a GSTZO film as the adhesion improving film and an aluminum oxide film as the antioxidant film because both effects of improving durability and improving reflectance can be obtained.

  As described above, the high reflection mirror of the present invention has a multilayer film including a silver film, a low refractive index film, and a high refractive index film formed on one side of the substrate. May be provided. Moreover, the structure of the multilayer film which has on both surfaces may be the same, and may differ.

  In the high reflecting mirror of the present invention, the minimum value in the entire visible light region of the reflectance of the film surface to the layer in contact with the air of the high reflecting mirror (hereinafter referred to as film surface reflectance) has an incident angle of 0. It is preferably 85% or more, particularly 88% or more in the range of ˜75 degrees. Specifically, the minimum value of the film surface reflectance over the entire visible light region is 85% or more, particularly 88% or more, and more preferably 91% or more at incident angles of 15, 45, and 75 degrees. preferable. Moreover, it is preferable that the maximum value of the film surface reflectance in the entire visible light region is 95% or more, particularly 96% or more when the incident angle is in the range of 0 to 75 degrees. Specifically, it is preferable that the maximum value of the film surface reflectance in the entire visible light region is 95% or more, particularly 96% or more when the incident angles are 15 degrees, 45 degrees, and 75 degrees. Since the highly reflective mirror of the present invention has a high film surface reflectance as described above, an image can be projected without lowering the brightness even when reflection is repeated in an electronic device such as a projection television or a liquid crystal display. It becomes possible. The incident angle means an angle with respect to a line perpendicular to the film surface.

  Furthermore, the high reflecting mirror of the present invention has a characteristic that the incident angle dependency of the reflectance with respect to the incident angle is small. Due to the above characteristics, even when the reflection angle is increased, the decrease in reflectance is small. For example, even when the reflection is repeated in an electronic device such as a projection television or a liquid crystal display, the casing in which the high-reflection mirror is placed is reduced. can do. Incident angle dependence refers to fluctuations in reflectance due to the incident angle of light. Specifically, the incident angle dependency is determined by measuring the deviation of the maximum value or the minimum value of the entire surface of the visible light region of the film surface reflectance in the cases where the incident angles are 15 degrees, 45 degrees, and 75 degrees, respectively. Is possible. The incident angle deviation of the maximum value is preferably within 2%, particularly within 1%, from the viewpoint that the incident angle dependency is small. The minimum incident angle deviation is 7% or less, and particularly preferably 5% or less, because the incident angle dependency is small.

  The high reflection mirror of the present invention can be formed by sputtering using a metal target and a metal oxide target. A method for manufacturing a high reflection mirror in the case where the high reflection mirror has a structure such as a silver film, an adhesion improving film, an antioxidant film, a low refractive index film, and a high refractive index film in order from the substrate will be described below. First, on a substrate, 1) a base film is formed by a reactive sputtering method using a metal target, and 2) a silver film is formed on the base film by a sputtering method using a silver or silver alloy target, 3) An adhesion improving film is formed on the silver film by sputtering using a metal oxide target, and 4) an antioxidant film is formed on the adhesion improving film by sputtering using a metal target. ) A low refractive index film is formed on the antioxidant film by a reactive sputtering method using a metal target. 6) A high refractive index film is formed on the low refractive index film by a metal target using a reactive sputtering method. To form. In the case of forming the adhesion improving film of 3), it is preferable to form the adhesion improving film in an atmosphere in which an oxidizing gas such as oxygen does not exist in order to prevent silver oxidation and decrease in reflectance. When the adhesion improving film is formed, the content of the oxidizing gas in the sputtering gas is preferably 10% by volume or less.

  As shown in FIG. 1, the high reflecting mirror 10 of the present invention has a configuration such as a silver film 2, an adhesion improving film 3, an antioxidant film 4, a low refractive index film 5, and a high refractive index film 6 in order from the substrate 1. Have.

  As the sputtering method, an alternating current (AC) or direct current (DC) sputtering method can be used. The DC sputtering method includes a pulse DC sputtering method. AC sputtering or pulse DC sputtering is effective in preventing abnormal discharge. In addition, AC or DC reactive sputtering is effective in that a dense film can be formed. Compared with vapor deposition, sputtering is superior in that it can be deposited on a large-area substrate, has a small deviation in film thickness distribution, and has little deviation in in-plane brightness even after repeated reflections. ing.

  The high reflection mirror of the present invention is effective as a reflection member of a light source such as a display display used in a flat panel display, a projection television, a mobile phone, and the like.

  Hereinafter, examples (Examples 1, 2, 5, and 6) and comparative examples (Examples 3 and 4) of the high reflection mirror of the present invention will be described in detail. However, the present invention is not limited to the above embodiments.

(Example 1)
In a vacuum chamber, a cleaned soda lime glass plate (100 mm × 100 mm × 2 mm thickness) was installed as a substrate, and a zinc oxide target (aluminum oxide content 3 mass%, zinc oxide content) with aluminum added as a target 97 mass%), a silver alloy target to which Au is added (Au content 2 at%, silver content 98 at%), a zinc oxide target to which gallium and silicon are added (gallium oxide content 5.7 mass%, silicon oxide) Content 0.1%, zinc oxide content 94.2 mass%, metal silicon target (boron-doped polycrystalline target, silicon content 99.999 mass%), metal niobium target (niobium content 99) 0.9 mass%) and aluminum alloy target (aluminum content 99.99 mass%) It installed in the opposing position of the board | substrate of a sword upper part, and the inside of a vacuum chamber was exhausted to 2 * 10 <-3> Pa. The size of the target surface was 177.8 mm × 381 mm, respectively. And the highly reflective mirror was obtained by forming the film of the following A) -F) in order.

A) ... (Formation of base film (zinc oxide film))
Argon gas is introduced into the vacuum chamber as a sputtering gas at a rate of 300 sccm, and an aluminum-doped zinc oxide film is formed on the glass substrate by a DC sputtering method using a zinc oxide target to which aluminum is added under the condition of an input power of 1 kW. The film was formed with a thickness of 5 nm. The components of the aluminum-doped zinc oxide film were the same as the target.

B) ... (formation of silver alloy film)
After exhausting the residual gas, argon gas as a sputtering gas was introduced into the vacuum chamber at a rate of 300 sccm, and a DC sputtering method was used on the base film using a silver alloy target to which Au was added under the condition of an input power of 1 kW. A silver alloy film was formed with a thickness of 100 nm. The composition of the silver alloy film was equivalent to that of the target.

C) ... (Formation of adhesion improving film (zinc oxide film))
After exhausting the residual gas, argon gas is introduced into the vacuum chamber as a sputtering gas at a rate of 300 sccm, and a silver alloy is used by a DC sputtering method using a zinc oxide target to which gallium and silicon are added under conditions of an input power of 1 kW. A gallium and silicon-doped zinc oxide film (refractive index at a wavelength of 550 nm: 1.99, extinction coefficient: 0.017) was formed to a thickness of 1.5 nm on the film. The components of the gallium-doped zinc oxide film were the same as the target.

D) ... (Formation of antioxidant film (aluminum film))
After exhausting the residual gas, argon gas was introduced as a sputtering gas into the vacuum chamber at a rate of 300 sccm, and an aluminum alloy target was used on the adhesion improving film by a DC sputtering method with an input power of 0.3 kW. The film was formed with a thickness of 1 nm. The components of the aluminum film were the same as the target.

E) ... (Formation of low refractive index film (silicon oxide film))
After exhausting the residual gas, oxygen gas is introduced as a sputtering gas into the vacuum chamber at a rate of 450 sccm, and a silicon oxide film is formed on the antioxidant film by a AC sputtering method using a metal silicon target under the condition of an input power of 2 kW. (Refractive index at a wavelength of 550 nm: 1.46, extinction coefficient: 0) was formed with a film thickness of 30 nm.

F) ... (Formation of high refractive index film (niobium oxide film))
After exhausting the residual gas, oxygen gas is introduced into the 450 sccm vacuum chamber as a sputtering gas, and a niobium oxide film (wavelength is formed on the low refractive index film using a metallic niobium target by DC sputtering under the condition of an input power of 2 kW. Refractive index at 550 nm: 2.30, extinction coefficient: 0) was formed with a film thickness of 43 nm.

The aluminum film formed in D) is oxidized during the formation of the silicon oxide film formed in E) to become an aluminum oxide film (refractive index at wavelength 550 nm: 1.77, extinction coefficient: 0). Was confirmed.
The durability of the formed high reflection mirror was evaluated by the following method. The results of (1) to (4) are shown in Table 1, and the result of (5) is shown in Table 2.

(1) High temperature and humidity resistance test The formed high reflection mirror was cut into a 50 mm square and used for a sample. The sample was allowed to stand for 24 hours in an atmosphere having a temperature of 50 ° C. and a relative humidity of 95%, and the presence or absence of film peeling or corrosion after the standing was confirmed. ○: There was no peeling of the film, and no corrosion was detected. X: Peeling and corrosion were detected on the film.

(2) Salt water test The formed high reflection mirror was cut into a 50 mm square and used as a sample. The sample was immersed in salt water containing 5% by mass of sodium chloride for 24 hours, and the presence or absence of film peeling or corrosion after immersion was confirmed. ○: There was no peeling of the film, and no corrosion was detected. X: Peeling and corrosion were detected on the film.

(3) Tape peeling test Adhesive tape No. was formed on the film surface of the formed high reflector. 610 (manufactured by Sumitomo 3M Co., Ltd.) was strongly pasted by hand, and the presence or absence of film peeling after peeling off vigorously was confirmed. ○: There was no peeling of the film. X: Peeling of the film was observed.

(4) Gauze rubbing test Gauze I (manufactured by Nippon Pharmacy) strongly rubbed 20 times on the film surface of the formed high-reflection mirror, and the presence or absence of film peeling or scratches after rubbing was confirmed. ○: There was no peeling of the film and no detection of scratches. X: Peeling and scratches were detected on the film.

(5) Film surface reflectivity The film surface reflectivity of the formed high reflector is measured using a spectrophotometer ART-25GT (manufactured by Spectrometer Co., Ltd.) at each of incident angles of 15 degrees, 45 degrees, and 75 degrees. The minimum value and the maximum value in the entire visible light range were calculated. The incident angle means an angle with respect to a line perpendicular to the film surface.

(Example 2)
In Example 1, instead of forming an aluminum film as an anti-oxidation film, argon gas was introduced as a sputtering gas at 200 sccm and nitrogen gas was introduced into a 200 sccm vacuum chamber, and AC reactive sputtering was performed under the condition of an input power of 0.5 kW. The same treatment as in Example 1 was conducted except that an aluminum nitride film (refractive index at a wavelength of 550 nm: 1.93, extinction coefficient: 0) was formed to a thickness of 1 nm as an antioxidant film using an aluminum alloy target. A highly reflective mirror was formed. The formed high reflection mirror was evaluated in the same manner as in Example 1. The results of (1) to (4) are shown in Table 1, and the result of (5) is shown in Table 2.

(Example 3) (Comparative example)
In Example 1, D)... A high reflecting mirror is formed in the same manner as in Example 1 except that no antioxidant film is formed. The formed high reflection mirror is evaluated in the same manner as in Example 1. The results of (1) to (4) are shown in Table 1, and the result of (5) is shown in Table 2.

(Example 4) (Comparative example)
In a vacuum chamber, a cleaned soda lime glass plate (100 mm × 100 mm × 2 mm thickness) was installed as a substrate, and a zinc oxide target (aluminum oxide content 3 mass%, zinc oxide content) with aluminum added as a target 97 mass%), silver target (silver content 100 at%), aluminum alloy target (aluminum content 99.99 mass%), zirconium target (zirconium content 99.99 mass%), metal silicon target (boron dope) The polycrystalline target and silicon content of 99.999% by mass) were placed at positions facing the substrate above the cathode, respectively, and the inside of the vacuum chamber was evacuated to 2 × 10 −3 Pa. The size of the target surface was 177.8 mm × 381 mm, respectively. And the highly reflective mirror was obtained by forming the film of the following A) -E) in order.

A) ... (Formation of zinc oxide film)
Argon gas is introduced into the vacuum chamber as a sputtering gas at a rate of 300 sccm, and an aluminum-doped zinc oxide film is formed on the glass substrate by a DC sputtering method using a zinc oxide target to which aluminum is added under the condition of an input power of 1 kW. The film was formed with a thickness of 5 nm. The components of the aluminum-doped zinc oxide film were the same as the target.

B) ... (Formation of silver film)
After exhausting the remaining gas, argon gas as a sputtering gas was introduced into the vacuum chamber at a rate of 300 sccm, and a silver film was formed on the zinc oxide film at a thickness of 100 nm using a silver target under a condition of an input power of 1 kW by DC sputtering. The film thickness was formed. The component of the silver film was equivalent to the target.

C) ... (Formation of aluminum oxide film)
After exhausting the residual gas, oxygen gas was introduced into the vacuum chamber as a sputtering gas at a rate of 450 sccm, and the metal aluminum target (aluminum content of 99.99 mass%) was applied under the condition of an input power of 2 kW by the AC reactive sputtering method. ), An aluminum oxide film (refractive index at a wavelength of 550 nm: 1.7, extinction coefficient: 0) is formed to a thickness of 69 nm on the silver film.

D) ... (Formation of zirconium oxide film)
After exhausting the remaining gas, oxygen gas was introduced into the vacuum chamber as a sputtering gas at a rate of 450 sccm, and the metal zirconium target (zirconium content 99.99 mass%) was applied under the condition of an input power of 2 kW by the AC reactive sputtering method. ) Is used to form a zirconium oxide film (refractive index at a wavelength of 550 nm: 2.11, extinction coefficient: 0) with a thickness of 57 nm on the aluminum oxide film.

E) ... (Formation of silicon oxide film)
After exhausting the remaining gas, oxygen gas is introduced into the vacuum chamber as a sputtering gas at a rate of 450 sccm, and a silicon oxide film is formed on the zirconium oxide film using a metal silicon target by an AC sputtering method under the condition of an input power of 2 kW. (Refractive index at a wavelength of 550 nm: 1.46, extinction coefficient: 0) is formed with a film thickness of 20 nm.

  The formed high reflection mirror is evaluated in the same manner as in Example 1. The results of (1) to (4) are shown in Table 1, and the result of (5) is shown in Table 2.

(Example 5)
In Example 1, instead of forming a gallium and silicon-doped zinc oxide film as an adhesion improving film, after exhausting the residual gas, argon gas was introduced into the vacuum chamber as a sputtering gas at a rate of 300 sccm and charged by DC sputtering. A tin-doped indium oxide film (refractive index at a wavelength of 550 nm: 1.96, extinction coefficient: 0.021) using an indium oxide target to which tin is added (content of tin oxide: 10% by mass) under the condition of electric power of 1 kW Was processed in the same manner as in Example 1 except that the film thickness was 10 nm. The components of the tin-doped indium oxide film were equivalent to the target. The formed high reflection mirror was evaluated in the same manner as in Example 1. The results of (1) to (4) are shown in Table 1, and the result of (5) is shown in Table 2.

(Example 6)
In Example 1, instead of forming a gallium and silicon-doped zinc oxide film as an adhesion improving film, after exhausting the residual gas, argon gas was introduced into the vacuum chamber as a sputtering gas at a rate of 300 sccm and charged by DC sputtering. An antimony-doped tin oxide film (refractive index at a wavelength of 550 nm: 2.17, extinction coefficient: 0.039) using an antimony-added tin oxide target (antimony oxide content: 3% by mass) under the condition of electric power of 1 kW ) Was formed in a film thickness of 10 nm, and a high-reflection mirror was formed in the same manner as in Example 1. The components of the antimony-doped tin oxide film were equivalent to the target. The formed high reflection mirror was evaluated in the same manner as in Example 1. The results of (1) to (4) are shown in Table 1, and the result of (5) is shown in Table 2.

  Table 3 shows the film configuration of each example.

  The high reflecting mirrors of Examples 1, 2, 5 and 6 are further excellent in optical characteristics because a thin adhesion improving layer having a slight absorption is formed and an antioxidant layer having little absorption is laminated. In addition, in the entire visible light region, the minimum value of the film surface reflectance is as high as 91% or more, the maximum value is as high as 97% or more, the minimum incident angle deviation is 3% or less, and the maximum incident angle deviation is 0. Less than 5%.

  On the other hand, since the high reflecting mirror of Example 3 does not have an antioxidant film, its optical characteristics are not good. The high reflection mirror of Example 4 is not preferable because the minimum value of the film surface reflectance in the entire visible light region when incident at 15 degrees is as low as 73.8%.

  The high reflection mirror of the present invention is useful as a high reflection mirror used in a backlight module for a small liquid crystal display such as a projection television or a mobile phone.

It is sectional drawing of the high reflective mirror of this invention.

Explanation of symbols

1: Substrate 2: Silver film 3: Adhesion improving film 4: Antioxidation film 5: Low refractive index film 6: High refractive index film 10: High reflector

Claims (10)

  A high-reflection mirror in which a silver film, a low-refractive index film, and a high-refractive index film are laminated in this order on a substrate, and the film surface reflection in each case of incident angles of 15 degrees, 45 degrees, and 75 degrees A high-reflection mirror characterized in that the deviation of the lowest value of the rate in the entire visible light range is within 7%.   The high reflection mirror according to claim 1, wherein an adhesion improving film is formed on the opposite side of the silver film from the substrate, and an antioxidant layer is formed on the opposite side of the adhesion improving layer from the substrate.   The high reflection mirror according to claim 2, wherein the material of the adhesion improving film is at least one selected from the group consisting of zinc oxide, tin oxide, indium oxide, aluminum oxide, and titanium oxide.   The said adhesion improvement film | membrane is a zinc oxide film | membrane, the said zinc oxide film | membrane contains another metal, and the said other metal is 1 or more types chosen from the group which consists of gallium, tin, and titanium. High reflector.   5. The high reflector according to claim 4, wherein the content of one or more selected from the group consisting of gallium, tin, and titanium is 3 to 10 mass% in total with respect to all metal elements in the zinc oxide film.   The material of the antioxidant film is at least one selected from the group consisting of one or more oxides selected from the group consisting of aluminum, yttrium, zirconium, and hafnium, an aluminum nitride or oxynitride, and silicon nitride. The high reflecting mirror according to claim 2.   The film thickness of the adhesion improving film is 1 to 3 nm, the material of the antioxidant film is aluminum oxide, and the film thickness of the antioxidant film is 0.5 to 6 nm. High-reflection mirror described.   The film thickness of the adhesion improving film is 1 to 3 nm, the material of the antioxidant film is aluminum nitride, and the film thickness of the antioxidant film is 0.5 to 10 nm. High-reflection mirror described.   The high reflection mirror according to claim 2, wherein the adhesion improving film is formed by a sputtering method in an atmosphere in which no oxidizing gas exists. A display display in which the high reflecting mirror according to claim 1 is used as a reflecting member of a light source of a display display.

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