JP2007140371A - Surface mirror - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface mirror of a large size having no fine pinhole in diameter of 0.5 mm or less, the mirror that can be used for a rear projection television set using a light source with improved display luminance and image precision such as a DLP (digital light processing) system and a reflective liquid crystal panel. <P>SOLUTION: The surface mirror comprises a metal film and a metal oxide film deposited on a glass substrate, wherein Al film is used for the metal film and a SiNxOy film and a Nb<SB>2</SB>O<SB>5</SB>film are used for the metal oxide film. The Al film, SiNxOy film and Nb<SB>2</SB>O<SB>5</SB>film are successively layered on the glass substrate, or the SiNxOy film, Al film, SiNxOy film and Nb<SB>2</SB>O<SB>5</SB>film are successively layered. <P>COPYRIGHT: (C)2007,JPO&INPIT

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 a rear projection television 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, but the reflectance of this surface mirror is low, and it is used for a rear projector TV. It is not possible.

Therefore, the commonly used surface mirror is a reflection mirror of increasing reflection type, which is formed on a glass substrate in the order of Al, SiO ₂ , TiO ₂ , but this film configuration is wear resistant. If the surface is dirty, it cannot be wiped with a cloth.

As a solution to 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, projection televisions have grown in size to 60 inches or more, and display brightness and image precision have improved, such as Digital Light Processing (Texa Twin Strument, registered trademark) and reflective liquid crystal panels. As a result, a fine pinhole caused by a film defect of a surface mirror, which could not be confirmed in the past, appears as dirt on the screen and impairs the screen quality.

That is, conventionally, a film defect of a surface mirror has been regarded as having no problem if the diameter is 0.5 mm or less, but it has been found that a fine pinhole having a diameter of about 0.3 mm is also problematic. There is a need for large-sized surface mirrors that do not have large pinholes.
JP 2001-226765 A JP-A-6-51110 JP-A-6-130210 JP-A-6-130210

  A large-sized surface mirror without a fine pinhole having a diameter of about 0.3 mm is provided.

Surface reflector of the present invention is a surface mirror to a glass substrate and a metal film and a metal oxide film formed by deposition, Al film on a glass substrate, SiN x O y film are sequentially laminated Nb ₂ O ₅ film It is a surface mirror characterized by becoming.

  The surface reflecting mirror of the present invention is a surface mirror characterized in that SiNxOy is formed between a glass substrate and an Al film in the surface mirror.

  The surface mirror of the present invention makes it possible to provide a surface mirror with few fine pinholes required for a rear projection television.

In order to obtain a surface mirror without a fine pinhole, the occurrence of pinholes in a surface mirror composed of a glass substrate, an Al film, a SiO ₂ film, and Nb ₂ O ₅ was investigated. It has been found that no pinhole is generated in the Al film and the Nb ₂ O ₅ single layer film, and that the pinhole is generated when the SiO ₂ film is formed.

Furthermore, when depositing SiO ₂ using a Si target, a fine abnormal discharge called micro-arcing, which occurs as a result of the formation of a SiO ₂ insulating film on the Si surface and the accumulation of electric charges, occurs locally. It was observed. It was also found that there is a correlation between the frequency of micro arcing and the number of pinholes.

Therefore, it has been specified that pinholes having a diameter of 0.5 mm or less on the surface mirror are caused by micro-arcing when the SiO ₂ film is formed.

Therefore, a method for eliminating this micro arcing during the deposition of SiO ₂ was studied.
As a result, the same refractive index, instead of SiO _2, by using the SiNxOy film having absorption, succeeded in reducing the micro arcing. It was also confirmed that the surface mirror using SiNxOy has the same optical characteristics and durability as the surface mirror using SiO ₂ .

The mechanism by which this SiNxOy film prevents micro arcing has the effect of reducing the voltage at the time of film formation and making it difficult to generate micro arcing by preventing the generation of SiO _{2 which is} the source of micro arcing on the Si target surface. is there.

Surface mirror of the present invention, as these pinholes is very little surface mirror, it has been found Al film on a glass substrate, SiN x O y, a front surface mirror film structure composed of Nb ₂ O _5.

  FIG. 3 is a schematic diagram showing a configuration of the rear projection television 1 in which the surface mirror of the present invention is used. The rear projection television 1 mainly includes a video projection device 2, a reflection mirror 3 that reflects an image projected from the video projection device 2, a screen 4 that reflects an image reflected by the reflection mirror 3, and the like in a casing 5. Consists of. The video projection device 2 includes a display device such as a CRT and an optical system for projecting video.

In the surface mirror 3 of the present invention, as shown in FIG. 1, an Al film 13, a SiNxOy film 14, and a Nb ₂ O ₅ film 15 are deposited in this order on a glass substrate 11 by a physical vapor deposition method. As shown in FIG. 2, a SiNxOy film 12, an Al film 13, a SiNxOy film 14, and an Nb ₂ O ₅ film 15 are deposited in this order on the glass substrate 11 by physical vapor deposition. Thus, the surface mirror 3 ″ is formed to form the reflective film 10 ′.

  The glass substrate 11 can be a plate glass manufactured by a float process, and a glass surface on which the Al film 13 or the SiNxOy film 12 is formed can be suitably used by performing an ion etching process before forming the film. .

  In addition, it is preferable to use a glass called a high flatness glass with less surface waviness or a glass having excellent polished flatness.

  As physical vapor deposition, methods such as sputtering, vacuum vapor deposition, and electron beam vapor deposition can be used. Among these, the sputtering method is recommended because of easy film formation and good film adhesion.

  The SiNxOy film 12 formed on the surface of the glass substrate 11 shown in FIG. 2 further improves the crystallinity of the Al film than the film on which the Al film 13 formed thereon is directly deposited. The film is formed in order to improve the adhesion between the glass substrate 11 and the Al film 13, and the film thickness is preferably 1 to 50 nm. Further, there is no particular problem even when the thickness of the SiNxOy film 12 is as thick as about 100 nm, but the Al crystallinity is hardly changed at 50 nm or more, so that it is desirable to make it 50 nm or less in terms of cost.

  If the Al film 13 has a thickness of 60 nm or more, a visible light reflectance of 90% or more can be obtained, and even if the thickness is increased at 60 nm or more, the reflectance does not increase. It is. However, there is no particular problem even if the film thickness is larger than that.

  The Al film can be obtained by sputtering using an aluminum target in an inert atmosphere such as Ar gas.

  As the Al film, as a countermeasure for improving the corrosion resistance of Al, a film containing one or more metals selected from Mn, Mg, Si, and Nd of 0 to 5% by weight or less can be used. 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 aluminum target.

  However, if Mn, Mg, Si, or Nd contained in the Al film exceeds 5% by weight, the Al crystallinity is impaired and the reflectance is lowered, which is not preferable.

  Further, Mn, Mg, Si, and Nd contained in the Al film in order to improve the durability performance destroys the crystal structure of the Al film and lowers the reflectivity. Therefore, the content is preferably suppressed as much as possible.

The SiNxOy film 14 on the Al film also has an effect of improving the adhesion between the Al film 13 and the uppermost Nb ₂ O ₅ film 15.

If the thickness of the SiNxOy film 14 is 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 from Nb ₂ O ₅ , the thickness of the SiNxOy film 14 is preferably 80 ± 40 nm.

  The SiNxOy film 14 is obtained by sputtering in a mixed gas atmosphere of Ar gas, oxygen gas, and nitrogen gas using a Si target. In general, a Si target containing B or Al is 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%.

However, if the amount of nitrogen is too small relative to oxygen, a SiO ₂ film is formed. Arcing occurs and pinholes increase. On the other hand, if it is too much, Si ₃ N _{4 is formed} , which adversely affects the optical properties and durability of the surface mirror.

  Further, it is preferable that the SiNxOy film 14 to be formed satisfies 0.5 ≦ x ≦ 1.5 and 0.5 ≦ y ≦ 1.9.

The Nb ₂ O ₅ film 15 is obtained by using a niobium target and performing sputtering 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 mirror 13 for a rear projection television, by setting the thickness of the Nb ₂ O ₅ film 15 to 30 nm or more, sufficient high temperature resistance / high humidity resistance and wear resistance can be obtained. In order to obtain the effect of increasing the reflectivity due to the difference in refractive index from SiNxOy, the thickness of the Nb ₂ O ₅ film 15 is preferably 60 ± 40 nm.

  Hereinafter, as an example of the present invention, an embodiment in which a sputtering method is employed as a film forming method will be described in detail. However, the reflecting mirror of the present invention is not limited to this film forming method.

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

  First, in an atmosphere of Ar100 (sccm), oxygen 70 (sccm) and a vacuum pressure of 0.10 pa, a high-frequency power supply (output 3k, 2A) is used, and a voltage of 1000 V is applied to generate reactive plasma, The glass surface was modified by passing the glass under a neutral plasma at a speed of about 1 (mm / min).

  Next, using a dual cathode with a Si target attached using a medium frequency power source, a thickness of 30 nm in an atmosphere of argon 120 (sccm), oxygen 60 (sccm), nitrogen 35 (sccm) and a degree of vacuum of 0.30 (pa). A SiNx0y film 12 was formed.

  Next, on the SiNxOy film, an Al film 13 having a thickness of 80 nm was formed in an Ar300 (sccm) atmosphere using a dual cathode with an Al target attached using the same power supply.

  Next, the SiNxOy film 14 having a thickness of 80 nm is formed in an atmosphere of Ar120 (sccm), oxygen 70 (sccm), nitrogen 35 (sccm) pressure 0.46 (pa) using the same power source and cathode and a Si target. A film was formed.

Further, an Nb ₂ O ₅ film was formed to 60 nm on the SiNxOy film 14 using an Nb target. Film formation was performed in an atmosphere of Ar300 (sccm), oxygen 120 (sccm), and pressure 0.28 (pa) using a Nb target using the same power source and cathode.

Example 2
A reflecting mirror 3 ′ different from that in Example 1 in which SiNxOy is not formed between the glass substrate 11 and the Al film 13 shown in FIG. The production of this reflecting mirror was performed under exactly the same conditions as in Example 1 except that no SiNxOy was formed between the glass substrate 11 and the Al film 13.

Comparative Example 1
A surface mirror was fabricated in the same manner as in Example 1, except that a SiO ₂ film was formed using a Si target instead of SiNxOy in Example 1. The thickness of the SiO ₂ film was the same as the thickness of SiNxOy.

[Evaluation of pinhole]
Regarding the surface mirrors of Example 1, Example 2, and Comparative Example 1, the occurrence of pinholes was evaluated. The evaluation method confirmed the generation | occurrence | production number of the pinhole of diameter 0.3mm-0.5mm in ten glass substrates of 1000 mm x 600 mm size. Confirmation of the number of occurrences was performed immediately after the start of film formation, after 6 hours, 12 hours, and 24 hours after the start of film formation.

  Table 1 shows the number of confirmed pinholes. The number of generated pinholes in Table 1 is the number of pinholes confirmed in 10 samples.

As shown in Table 1, Examples 1 and 2 of a surface mirror with SiNxOy, the occurrence of pinholes after 24 hours, but was very small, Comparative Example 1 using the SiO ₂ is deposited The number of pinholes immediately after is small, but the number of pinholes increases with time, and it was found that a surface mirror without a pinhole cannot be produced after 12 hours.

[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 reflectors of Examples 1 and ₂ were almost the same as Comparative Example 1, and it was confirmed that there was no significant change in reflectivity even when the SiO ₂ film was changed to a SiNxOy film.
[Evaluation of durability]
The durability of the following evaluation items was evaluated with respect to Example 1, Example 2, and Comparative Example 1.

  Adhesion: Adhesive tape (Scotch Mending Tape 3M # 800) is attached to the film, then peeled off, and the film formed per 45 mmφ is peeled off. The number of pinholes (number) generated in the film is measured with a microscope. Observe and measure.

Hardness: A weight of 450 g / cm ² is placed on the film surface with a nell of 6 sheets stacked, and this is reciprocated 500 times at a stroke distance of 100 mm, and the change in transmittance of the sliding part is measured. .

  Moisture resistance: leave in an atmosphere of 50 ° C. and 95% RH for 24 hours. Then, clean and confirm that there is no abnormality in appearance quality before and after the test.

  High temperature resistance: Leave in an atmosphere at 70 ° C. for 24 hours. Then, clean and confirm that there is no abnormality in appearance quality before and after the test.

  High and low temperature resistance: 1 cycle is a cycle of standing in an atmosphere of 40 ° C. and 30% RH for 24 hours, allowing to stand for 1 hour, leaving in an atmosphere of −10 ° C. for 24 hours, and then allowing to stand for 1 hour. Perform cycle. Then, clean and confirm that there is no abnormality in appearance quality before and after the test.

  Salt water resistance performance: Leave in a 5% salt water atmosphere at 35 ° C. for 240 hours. Thereafter, it is washed and it is confirmed that there is no abnormality in appearance quality before and after the test (salt spray test ISO 9227).

  Table 3 shows the durability evaluation results.

There was almost no difference in durability between Examples 1 and 2 and Comparative Example 1, and it was confirmed that there was no problem in durability even when the SiO ₂ film was changed to SiNxOy.

It is a schematic sectional drawing which shows the film | membrane structure of the surface mirror of Example 2 of this invention. It is a schematic sectional drawing which shows the film | membrane structure of the surface mirror of Example 1 of this invention. It is the schematic which shows the structure of a rear projection television. 6 is a schematic cross-sectional view showing a film configuration of a surface mirror of Comparative Example 1. FIG.

Explanation of symbols

1 rear projection television 2 video projector 3 surface mirror 4 Screen 5 casing 10 reflective film 11 glass substrate 12 SiN x O y film 13 Al film 14 SiN x O y film 15 _Nb 2 _{O 5} film 16 SiO ₂ film

Claims (2)

The surface mirror to a glass substrate and a metal film and a metal oxide film formed by deposition, Al film on a glass substrate, SiN x O y film, a front surface mirror, characterized in that formed by sequentially laminating a Nb ₂ O ₅ film .   2. The surface mirror according to claim 1, wherein SiNxOy is formed between the glass substrate and the Al film.

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