JP5045261B2 - Surface mirror - Google Patents

Description

  The present invention relates to a surface mirror in which a metal film and an oxide film are stacked, and more particularly to a surface mirror used in an electronic copying apparatus such as a rear projection television or a scanner that projects an image from the back of a screen.

  In recent years, there are rear projection televisions, flat panel displays, projection televisions, and the like as large-screen display devices. Among them, rear projection televisions are considerably popular because they are inexpensive.

  The rear projection television is a screen that displays a display screen such as a CRT on the screen using an optical system. By reflecting the display light using a mirror, the optical path is extended with a small depth and projected on a large screen. I have to.

  As mirrors used in rear projection televisions, an Ag film is formed on a glass substrate by a silver mirror reaction, and a protective film is formed on the Ag film, a so-called back mirror, and a metal film is formed on the glass surface. A surface mirror is used in which an oxide film is formed thereon, light is incident from the surface of the oxide film, and is reflected by a metal film.

  The back mirror is protected with a durable protective film, and the durability is so good that it can be used in bathrooms, etc., but light reflects on the glass surface as well as on the Ag film. Therefore, there is a problem that a double image is generated in the display displayed on the screen and a problem that the reflectance is low due to absorption of display light by the glass substrate.

  A surface mirror formed by depositing a metal film on the glass surface by physical vapor deposition or the like has a high reflectivity, and the metal film directly reflects display light without passing through the glass, so there is no problem of a double image. .

  For example, Patent Document 1 discloses a surface mirror in which a metal film containing Ag as a main component and added with Pd, Au, and Ru is formed by a sputtering method.

  However, such a mirror is expensive because it uses a precious metal for use in a rear projection television used in general homes, and has a problem in durability against a high temperature and high humidity atmosphere.

Therefore, recently, a surface mirror using Al for the metal film has been used. For example, Patent Document 2 proposes a reflecting mirror in which a thin film is deposited on a substrate in the order of TiO ₂ , AlO ₂ , Al, and TiO ₂ as a surface mirror using Al. The reflectance of this surface mirror is 90% or less, and there is a difficulty in the hardness of the reflective film.

Patent Document 3 proposes a reflecting mirror in which a thin film is deposited in the order of SiO ₂ , Al, Cr, and Al ₂ O _{3 on} a substrate. However, the reflectance of this surface mirror is low, and a rear projector TV or scanner It cannot be used for an electronic copying apparatus such as.

Therefore, the commonly used surface mirror is a reflection mirror of the increased reflection type in which Al, SiO ₂ and TiO ₂ are formed in this order on a glass substrate. If the surface is dirty, it cannot be wiped with a cloth.

In order to solve this defect, Patent Document 4 proposes a surface mirror in which a thin film is deposited in the order of Al, SiO ₂ , TiO ₂ , and SixNy on a substrate. The surface mirror having this film structure shows improved wear resistance, but the structure of the Al film is not improved, so that sufficient hardness and durability are not obtained.

  Recently, surface mirrors are used in electronic copying apparatuses such as scanners in addition to projection television applications. A surface mirror used in an electronic copying apparatus such as a scanner requires a process of cutting a large plate into a strip and performing seaming. In this cutting and seaming process, it is necessary to apply a curing film to the large plate-shaped surface mirror in advance in order to prevent generation of scratches and adhesion of dirt on the surface mirror.

  If the surface mirror film is weak, film peeling occurs in the step of peeling the curing film. Further, even in a sampling test for confirming that film peeling does not occur in a strip shape, film peeling can be easily placed from the edge of the strip, which causes a decrease in yield. Further, even for projection television applications, a curing film is sometimes attached and shipped, and film peeling when the curing film is peeled is a problem as in the case of an electronic copying apparatus such as a scanner.

In Patent Document 5, as a method for improving the adhesion between the glass substrate and the Al metal film serving as a reflective film, a method of modifying the surface of the glass substrate by ion etching, and SiO between the glass substrate and the Al metal film are disclosed. It has been proposed to form ₂ . However, the adhesion between the Al metal film and the oxide film formed on the Al metal film has not been improved.
JP 2001-226765 A JP-A-6-51110 JP-A-6-130210 JP-A-6-130210 JP 2006-337770 A

  When a metal oxide film or metal oxynitride film that acts as a reflective and protective film is formed on the Al film, which is a reflective film, the adhesion between Al and the metal oxide film or metal oxynitride film is weak and sufficient durability Therefore, it is difficult to use it for a surface mirror used in an electronic copying apparatus such as a rear projection television or a scanner. The present invention provides a surface mirror having excellent adhesion between an Al film, which is a reflective film, and a metal oxide film or a metal oxynitride film that functions as a reflection enhancing film and a protective film.

The surface reflector of the present invention is a surface mirror in which a metal film and a metal oxide film, or a metal nitride film and a metal oxide film are formed on a glass substrate, and an Al—AlO _z inclined film, SiN on the glass substrate. _The surface mirror is formed by sequentially stacking an xO _y film and an Nb ₂ O ₅ film.

The surface reflecting mirror of the present invention is a surface mirror characterized in that a SiN _x O _y film is formed between the glass substrate and the Al—AlO _z inclined film in the surface mirror.

Further, in the surface reflecting mirror of the present invention, in the surface mirror, the (Al film thickness) / (Al film thickness + AlO _z gradient film thickness) of the Al—AlO _z inclined film is 0.3. The surface mirror is characterized by the following.

  The surface mirror of the present invention makes it possible to provide a surface mirror having excellent adhesion required for an electronic copying apparatus such as a rear projection television or a scanner.

In the surface mirror of the present invention, as shown in FIG. 1, an Al—AlO _z inclined film 13, a SiN _x O _y film 14, and a Nb ₂ O ₅ film 15 are deposited in this order by physical vapor deposition on a glass substrate 11. Then, as shown in FIG. 2, the surface mirror 1 that forms the reflective film 10, or the SiN _x O _y film 12, the Al—AlO _z inclined film 13, the SiN _x O _y film 14, Nb as shown in FIG. _{The 2} O ₅ film 15 is a surface mirror 1 ′ which is deposited in this order by physical vapor deposition to form a reflective film 10 ′.

  As the glass substrate 11, it is easy to use soda lime glass by a float method having a good surface smoothness and a surface smoothness which is obtained at a relatively low cost as a member having good smoothness and a certain degree of rigidity.

  In addition, if the surface mirror has irregularities, it becomes a light and dark streak and is projected on the screen to cause a problem. Therefore, a polished product obtained by polishing the glass surface to remove undulation is used for the glass substrate 11. preferable.

  Further, when the glass is distorted by its own weight, the image projected on the screen is also distorted. Therefore, glass having a high Young's modulus, for example, high strain point glass can be used as the glass substrate 11.

  Although the thickness of the glass substrate 11 is not particularly limited, the thick glass is less distorted by its own weight when used than the thin glass, and as a result, the image is not distorted. Then, especially in a large-sized television such as a rear projection television, handling at the time of assembling becomes difficult, and further, there is a problem that the burden on the structural material of the transport system is increased when the surface mirror is formed. A thickness of ˜8 mm is desirable.

  As a physical vapor deposition method for forming the reflective films 10 and 10 ′ on the glass substrate 11, methods such as a sputtering method, a vacuum vapor deposition method, and an electron beam vapor deposition method can be used. Among these, the sputtering method is recommended because of easy film formation and good film adhesion.

The SiN _x O _y film 12 formed on the surface of the glass substrate 11 shown in FIG. 2 is an Al film rather than the Al—AlO _z inclined film 13 formed on the glass substrate directly. The film is formed to further increase the crystallinity and improve the adhesion between the glass substrate 11 and the Al—AlO _z inclined film 13, and the film thickness is preferably 1 to 50 nm.

Further, there is no particular problem when the thickness of the SiN _x O _y film 12 is as thick as about 100 nm, but the Al crystallinity is hardly changed at 50 nm or more, so the cost should be 50 nm or less. desirable. Further, it is preferable that the SiN _x O _y film 12 to be formed _satisfies 0 ≦ x ≦ 1.5 and 0.5 ≦ y ≦ 2.0 because the adhesion is improved.

The Al—AlO _z inclined film 13 has a visible light reflectance of 90% or more if the film thickness is 60 nm or more, and the reflectance does not increase even if the thickness is increased to 60 nm or more, so the film thickness is 60 nm. Is enough. However, there is no particular problem even if the film thickness is larger than that.

Al-AlO _z gradient film 13 is a film AlO _z gradient film having a degree of oxidation is changed gradually, which are deposited on the Al film, from the center of the thickness of the Al-AlO _z gradient film, Al The film is more oxidized toward the SiN _x O _y film 14 side on the AlO _z gradient film 13.

The Al—AlO _z inclined film 13 can be obtained by sputtering using an Al target in an atmosphere of an inert gas such as Ar gas and oxygen gas. When the film is formed, the oxygen gas is supplied from one direction of the Al target, and the film can be formed by providing a gradient in oxygen concentration on the Al target.

  In particular, in the in-line type sputtering apparatus, as shown in FIG. 3, an oxygen gas pipe 29 for supplying oxygen gas is installed by shifting to the substrate traveling direction side of the Al target 23, and oxygen gas is introduced from the oxygen gas pipe 29. A method of forming a film with a gradient in the oxygen gas concentration in the width direction of the Al target 23 is effective.

When the degree of oxidation on the side of the Al—AlO _z inclined film 13 in contact with the SiN _x O _y film 14 is too high, it causes a decrease in reflectance. If the degree of oxidation is too small, sufficient film adhesion cannot be obtained. Therefore, the oxidation degree of the Al—AlO _z gradient film in contact with the SiN _x O _y film 14 is preferably 0.1 ≦ z ≦ 1.0. More preferably, 0.2 ≦ z ≦ 0.8.

Moreover, in the film thickness of the Al—AlO _z gradient film, if (Al film thickness) / (Al film thickness + AlO _z gradient film thickness) is too large, sufficient adhesion cannot be obtained. It is desirable that (Al film thickness) / (Al film thickness + AlO _z gradient film thickness) is 0.3 or less.
The value of (the thickness of the Al film) / (the thickness of the Al film + the thickness of the AlO _z inclined film) should be calculated from a spectrum chart obtained by depth direction analysis with an Auger microprobe as shown in FIG. Can do.

(Al film thickness + AlO _z gradient film thickness) 32 is the peak width of the Al spectrum of the Auger microprobe at the analysis intensity = 0. The film thickness 31 of the Al film is a value obtained by subtracting the width at the analysis intensity = 0 where the Al spectrum and the oxygen spectrum overlap from the peak width 32 of the Al spectrum of the Auger microprobe at the analysis intensity = 0. (Al film thickness) / (Al film thickness + AlO _z gradient film thickness) is calculated.

As a measure for improving the corrosion resistance of the Al—AlO _z gradient film 13, it is preferable to contain 0 to 5% by weight or less of one or more metals selected from Mn, Mg, Si, and Nd.

  In order to contain Mn, Mg, Si, and Nd, it is obtained by forming a film in an inert atmosphere such as Ar gas using a target in which Mn, Mg, Si, and Nd are contained in an Al target.

However, if Mn, Mg, Si, and Nd contained in the Al—AlO _z inclined film 13 exceed 5% by weight, the Al crystallinity is impaired and the reflectance is lowered, which is not preferable.

When the thickness of the SiN _x O _y film 14 is set to 30 nm or more, a surface mirror having sufficient hardness, high temperature resistance and high humidity can be obtained as compared with a film in which an Nb ₂ O ₅ film is directly deposited on an Al film. In order to obtain the effect of increasing the reflectivity due to the difference in refractive index with Nb ₂ O ₅ , the thickness of the SiN _x O _y film 14 is preferably 80 ± 40 nm.

The SiN _x O _y film 14 is obtained by sputtering in a mixed gas atmosphere of Ar gas, oxygen gas, and nitrogen gas using a Si target. As the Si target, one containing B or Al is generally used. The ratio of Ar gas, oxygen gas, and nitrogen gas is optimally set to Ar gas: 35-80%, oxygen gas: 15-45%, and nitrogen gas: 5-25%.

In addition, the SiN _x O _y film 14 to be formed is preferably set to 0 ≦ x ≦ 1.5 and 0.5 ≦ y ≦ 2.0, because the adhesion between the films is improved.

The Nb ₂ O ₅ film 15 is obtained by sputtering using an Nb target in an atmosphere containing 50 to 100% by weight of oxygen with respect to Ar gas, and is formed for the purpose of protecting the metal film and increasing reflection. .

In order to use the surface mirrors 1 and 1 ′ in an electronic copying apparatus such as a rear projection television and a scanner, the Nb ₂ O ₅ film 15 has a thickness of 30 nm or more, so that it has sufficient high temperature resistance, high humidity resistance and wear resistance. Is obtained. In order to obtain the effect of increasing the reflectivity due to the difference in refractive index from SiN _x O _y , the thickness of the Nb ₂ O ₅ film 15 is preferably 60 ± 40 nm.

  Hereinafter, as an embodiment of the present invention, film formation by an in-line sputtering method using the film formation apparatus shown in FIG. 3 will be described in detail. However, the reflecting mirror of the present invention is limited to this film formation method. is not.

Example 1
A surface mirror 1 having a film configuration shown in FIG. 1 was manufactured using a float glass plate having a thickness of 3 mm and a size of 1000 mm × 600 mm which had been washed and dried. All the films were formed by sputtering.

  First, in an atmosphere of Ar gas 100 (sccm), oxygen gas 70 (sccm) and pressure 0.10 (pa), a high frequency power supply device (not shown) (output 3 k, 2 A) was used, and a voltage of 1000 V was applied. Reactive plasma was generated, and the glass was passed under the reactive plasma at a speed of about 1 (m / min) to modify the surface of the plate glass.

Subsequently, an atmosphere of Ar gas 300 (sccm), oxygen gas 10 (sccm), and pressure 0.58 Pa using a dual cathode (not shown) with an Al target 23 attached using a medium frequency power supply device (not shown). Then, an Al—AlO _z inclined film 13 having a thickness of 70 nm was formed.

Note that when forming the Al—AlO _z inclined film 13, oxygen gas was introduced through an oxygen gas pipe 29 that was shifted in position on the Si target 24 side where the SiN _x O _y film 14 was formed.

Next, a SiN _x O _y film 14 having a thickness of 80 nm is used, and a power supply device similar to the power supply device used when forming the Al—AlO _z inclined film 13 is used, and a cathode (not shown) attached with a Si target is used. Then, a film was formed in an atmosphere of Ar 150 (sccm), oxygen 90 (sccm), nitrogen 25 (sccm) pressure 0.69 (pa).

Further, a 60 nm thick Nb ₂ O ₅ film was formed on the SiN _x O _y film 14 using a Nb target. The film formation is performed using a power supply device similar to the power supply device used when forming the Al—AlO _z inclined film 13, using a cathode (not shown) with an Nb target attached thereto, Ar 170 (sccm), oxygen 100 The film was formed in an atmosphere of (sccm) and a pressure of 0.64 (pa).

The surface mirror 1 was measured with an Auger microprobe (JAMP30 manufactured by JEOL Ltd.), and the result of FIG. 6 was obtained. As a result of calculating the value of (Al film thickness) / (Al film thickness + AlO _z film thickness) from FIG. 6, it was 0.07.

Example 2
A surface mirror 1 ′ having a film configuration shown in FIG. 2 was prepared using a washed and dried float glass plate having a thickness of 3 mm and a size of 1000 mm × 600 mm. All the films were formed by sputtering.

  First, in an atmosphere of Ar100 (sccm), oxygen 70 (sccm) and a pressure of 0.10 pa, a high-frequency power supply device (not shown) (output 3k, 2A) is used to generate a reactive plasma by applying a voltage of 1000 V, Under the reactive plasma, the glass was passed at a rate of about 1 (m / min) to modify the glass surface.

  Next, using a medium frequency power source (not shown) and using a dual cathode (not shown) with an Si target 22 attached thereto, argon 180 (sccm), oxygen 20 (sccm), nitrogen 10 (sccm), and pressure 0.35 (pa). ), A SiNx0y film 12 having a thickness of 10 nm was formed.

Next, using a power supply device similar to the power supply device used when forming the SiNxOy film 12 on the SiN _x O _y film 12, using a dual cathode (not shown) with an Al target 23 attached, Ar300 ( A 70 nm thick Al—AlO _z inclined film 13 was formed in an atmosphere of sccm), oxygen 10 (sccm), and pressure 0.58 (Pa).

Note that when forming the Al—AlO _z inclined film 13, oxygen gas was introduced through an oxygen gas pipe 29 that was shifted in position on the Si target 24 side where the SiN _x O _y film 14 was formed.

Next, an SiN _x O _y film 14 having a thickness of 80 nm and an Nb ₂ O ₅ film 15 having a thickness of 60 nm were formed on the SiN _x O _y film 14 in the same manner as in Example 1.

  The result of measuring this surface mirror with an Auger microprobe (JAMP30 manufactured by JEOL Ltd.) is shown in FIG.

As a result of calculating the value of (Al film thickness) / (Al film thickness + AlO _z film thickness) from FIG. 7, it was 0.09.

Comparative Example 1
Instead of the Al—AlO _z inclined film 13, an Al film 16 was formed. Except for the above, film formation was performed in the same manner as in Example 2 to fabricate a surface mirror 1 ″. The Al film 16 was made of Ar300 (sccm), pressure 0.52 (using a dual cathode (not shown) with an Al target attached thereto. A film having a thickness of 70 nm was formed in an atmosphere of Pa).

FIG. 7 shows the result of measuring the surface mirror 1 ″ produced in Comparative Example 1 with an Auger microprobe in the same manner as in Example 1. From FIG. 8, (Al film thickness) / (Metal Al film thickness). As a result of calculating the ratio of the film thickness of the + AlO _z film, it was 0.42.

  In addition, in the result of FIGS. 6-8 measured with the Auger microprobe, it is because Ca was detected because it analyzed in the depth direction until it reached the glass substrate, and Ca was not detected from the reflective film. .

[Evaluation of adhesion]
With respect to the surface mirrors of Example 1, Example 2, and Comparative Example 1, the adhesion evaluation of the reflective film was performed. In the evaluation method, a surface mirror glass having a size of 1000 mm × 600 mm immediately after film formation is cooled at room temperature for 30 minutes, and then a curing film SPV224 (hereinafter referred to as a curing film) manufactured by Nitto Denko is pasted. Then, with the curing film attached, the strip is cut into 15 mm × 200 mm strips with a wheel cutter. Wet seaming was performed on the strips, and water adhering to the strips was wiped off with a waste cloth and dried with hot air at 45 ° C. Using a dried strip, after a predetermined time had elapsed, the curing film was peeled off from the reflective film, and the adhesion of the reflective film was evaluated.

  The angle at which the curing film was peeled off was set to the direction perpendicular to the reflective film surface, and the film was peeled off instantaneously for evaluation. The evaluation results are shown in Table 1.

  For strips that did not peel off the reflective film due to peeling of the curing film, film peeling evaluation was performed using a Scotch transparent film tape # 610 (hereinafter referred to as # 610 tape) manufactured by 3M Corporation in the United States. Carried out.

  A # 610 tape was attached to the reflective film of the surface mirror, and after 30 seconds, it was peeled off with the edge of the # 610 tape.

  The # 610 tape is applied with an eraser in accordance with the cross-cut tape method described in JIS K 5400, taking care that no air enters the edge of the strip so that the # 610 tape protrudes from both edges of the strip. The surface of the tape was rubbed to completely adhere # 610 tape to the reflective film.

  One to two minutes after the # 610 tape was attached, one end of the # 610 tape was held and peeled off instantaneously in the direction perpendicular to the reflective film surface to evaluate the adhesion. The evaluation of adhesion was performed based on the number of film peeling when the cured film was peeled off and when the # 610 tape was peeled off.

  In addition, the evaluation of adhesion was carried out on strips that had passed each time, 1 hour, 1 day, 7 days, and 14 days after the formation of the reflective film. The evaluation results are shown in Table 1.

As shown in Table 1, in Comparative Example 1, film peeling occurred even when the cured film was peeled off. As a result of analyzing the peeled portion with an Auger microprobe (JAMP30 manufactured by JEOL Ltd.), it was confirmed that the peeled portion was peeled off at the interface between the Al film 16 and the SiN _x O _y film 13. On the other hand, with respect to the surface mirror using the Al—AlO _z inclined film produced in Examples 1 and 2, the reflective film was not peeled off after 1 hour to 14 days after film formation, It was confirmed that the adhesion of the reflective film was maintained over time.

[Evaluation of reflectivity]
With respect to Example 1, Example 2, and Comparative Example 1, the reflectance by the visible light wavelength at an incident angle of 8 degrees was measured with a spectrophotometer (U-400 type, manufactured by Hitachi, Ltd.). The measurement results of the reflectance are shown in Table 2.

The reflectances of the reflectors of Examples 1 and 2 were almost the same as those of Comparative Example 1, and it was confirmed that there was no significant change in reflectance even when the Al film was changed to an Al—AlO _z inclined film.

It is a schematic sectional drawing which shows the film | membrane structure of the surface mirror of Example 1 of this invention. It is a schematic sectional drawing which shows the film | membrane structure of the surface mirror of Example 2 of this invention. Schematic diagram of in-line sputtering equipment 6 is a schematic cross-sectional view showing a film configuration of a surface mirror of Comparative Example 1. FIG. Explanatory drawing for calculating the value of (Al film thickness) / (Al film thickness + AlO _z gradient film thickness). The measurement result with the Auger microprobe of Example 1. The measurement result with the Auger microprobe of Example 2. The measurement result with the Auger microprobe of the comparative example 1.

Explanation of symbols

1, 1 ′, 1 ″ surface mirror 10, 10 ′, 10 ″ reflective film 11 glass substrate 12 SiN _x O _y film 13 Al—AlO _z inclined film 14 SiN _x O _y film 15 Nb ₂ O ₅ film 16 Al film 21 In-line sputtering device 22 Si target 23 Al target 24 Si target 25 Nb target 26 Oxygen gas 27 Argon gas 28 Nitrogen gas 29 Oxygen gas piping

Claims (2)

In a surface mirror in which a metal film and a metal oxide film are formed on a glass substrate, an Al—AlO _z inclined film, a SiN _x O _y film, and an Nb ₂ O ₅ film are sequentially stacked on the glass substrate. The Al—AlO _z inclined film is formed by forming an AlO _z film that is oxidized on the Al film as it goes to the SiN _x O _y film side, and in contact with the SiN _x O _y film. 0.1 ≦ z ≦ 1.0, and (Al film thickness) / (Al film thickness + AlO _z gradient film thickness) of the Al—AlO _z gradient film is 0.3 or less. A surface mirror characterized by that. A SiN _x O _y film is formed between the glass substrate and the Al—AlO _z gradient film, and an Al—AlO _z gradient film, a SiN _x O _y film, and an Nb ₂ O ₅ film are sequentially stacked thereon . The surface mirror according to claim 1.

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