JPH05127018A - Strain removing method for substrate subjected to vapor deposition and filter - Google Patents

Abstract

PURPOSE:To remove strains without deteriorating the reflection spectral characteristics of the dichroic filter, etc. CONSTITUTION:Equivalent refraction film units of a symmetrical structure having the refractive index approximately equal to the refractive index of a substrate 1 are repetitively laminated on the rear surface side of the dichroic filter, etc., and the thickness of the laminated films 3 thereof is approximately equaled to the thickness of the refractive index of the multilayered films 2 on the front side surface of the substrate 1. The equivalent refraction film units are formed to have approximately the same refractive index as the refractive index of the substrate 1 by symmetrically combining low-refractive index materials (L) and high-refractive index materials (H, M) like (L/H/L), (H/L/H), (L/M/L), etc. Since the multilayered films 3 having approximately the same thickness as the thickness of the front side surface, on the rear surface side of the substrate 1, the strains are relieved. Further, the reflection spectral characteristics do not change since the multilayered films are approximately the same as the substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing distortion of a vapor-deposited substrate for removing distortion of an interference filter such as a dichroic filter.

[0002]

2. Description of the Related Art When a multi-layer film is deposited on the front side of a glass substrate by sputtering, ion plating, ion assist, etc., and an interference filter having a predetermined reflection spectral characteristic is manufactured, the strength of the deposited film is increased. Stress also increases and the substrate distorts to a spherical surface as shown in FIG. This distortion cannot be ignored when used as a precision interferometer or as part of a high precision image transfer system. In high-definition liquid crystal vision, dichroic filters for separating R, G, and B are arranged in front of each liquid crystal panel to separate light from a high-intensity lamp. In order to suppress the temperature rise of the LCD panel, the spectral characteristics of the dichroic filter must be stable regardless of the temperature rise of itself.

[0003]

As a means for removing the distortion of the dichroic filter as shown in FIG. 5, it is possible to bond other substrates, but since the adhesive is used, the spectral characteristic This leads to lower costs and higher costs. The present invention is to deposit a multilayer film on the back side of the substrate in order to remove distortion without deteriorating the reflection spectral characteristic of the interference filter, which will be described in detail below.

[0004]

[Means for Solving the Problems] Equivalent refractive film units having a symmetrical structure having a refractive index substantially equal to that of the substrate are repeatedly laminated on the back surface of a substrate having a multilayer film deposited on the front surface, and are substantially equal to the multilayer film. Make it thick. The equivalent refractive film unit is
The equivalent refractive index that is approximately equal to that of the glass substrate (L / M /
L), (L / H / L), (H / L / H), and the like, which are obtained by symmetrically combining various refractive index substances and adjusting the film thickness. This equivalent refraction film unit is repeatedly laminated on the back side to the same thickness as the multilayer film on the front surface of the substrate, but when the antireflection film is applied, the equivalent refraction film unit is thinned by that amount. Also, the optical thickness of the equivalent refractive film unit is smaller than the required wavelength.

[0005]

[Function] The interference fringes of the dichroic filter having the multilayer film deposited on the back surface of the substrate having the multilayer film deposited on its front surface and having a thickness substantially equal to that of the multilayer film and having an equivalent refractive index substantially the same as that of the substrate are As shown in Fig. 2, a vertical stripe pattern is formed, and the distortion of the substrate is removed. It is understood that the stress of the multilayer film on the front surface of the glass substrate was offset by the stress from the equivalent refraction film unit evaporated film on the back surface. The spectrum that has passed through the multilayer film on the front side passes through the equivalent refractive film unit that has the same refractive index as glass without deterioration in characteristics. It is a feature of the present invention that this equivalent refractive film unit laminated film does not affect the reflection spectral characteristics of the dichroic filter. In FIG. 3, the thick line b is the reflection characteristic curve of the dichroic filter before the treatment, and the thin line a is the reflection characteristic curve of the dichroic filter in which the equivalent refraction film unit is laminated on the back side, which are almost the same in a predetermined wavelength range. It is understood that it has a spectral characteristic and does not influence the dichroic filter reflection spectral characteristic.

[0006]

EXAMPLE A dichroic filter is formed by stacking 15 (L / H / L) units on the front surface of a substrate 1 made of glass having a refractive index of 1.52 and a thickness of 200 μm.
Here, L is silicon dioxide (SiO ₂ : refractive index = 1.45) and has a thickness of 36.2 nm, and H is titanium dioxide (TiO ₂ : refractive index = 2.3) and has a thickness of 45.65 nm. .. As an equivalent refraction film unit deposited on the back side of the substrate 1, (L / M /
L) is symmetrical and L is SiO ₂ and the thickness is 25.88.
nm and M are alumina (Al ₂ O ₃ : refractive index = 1.62) and the thickness is 14.17 nm. Therefore, the equivalent refractive film unit has a thickness of 2 × (thickness of low refractive index material) + (thickness of high refractive index material) of 70.26 nm, and the refractive index is about 1.5.
become. This equivalent refraction film unit is laminated 23 times, and the multilayer film 3 having substantially the same thickness as the multilayer film 2 on the front surface is deposited. A multilayer film having a thickness substantially equal to that of the multilayer film 2 is formed by repeatedly stacking an equivalent refractive film unit having a symmetrical structure having a refractive index substantially equal to that of the substrate 1 on the back surface of the substrate 1 having the multilayer film 2 deposited on the front surface. It is a feature of the present invention that 3 is vapor-deposited.

The equivalent refraction film unit having a symmetric structure is (L / H / L), (H / L / H) in addition to the above (L / M / L).
A combination of the above is conceivable. L is a low refractive index material such as SiO ₂ , and M and H are high refractive index materials such as TiO ₂ and Al ₂ O ₃ . The thicknesses L, M, and H are appropriately selected so that the equivalent refractive index is substantially equal to the refractive index of the substrate 1. The optical film thickness of the equivalent refraction film unit is smaller than the required wavelength. Also,
When L = 0, there is only M or H, and the refractive index of the equivalent refractive film unit is equal to that of M or H. Similarly, the refractive index of the equivalent refractive film unit when H or M = 0 is equal to L.

The multilayer film 3 deposited on the back surface of the dichroic filter is apparently the same as glass. In order to perform the antireflection film treatment on the multilayer film 3, the thickness of the multilayer film 3 may be reduced by the amount of the antireflection film. A three-layer type (A / 2B / C) known as an antireflection film is adopted. A is alumina (Al ₂ O ₃ ) and has a thickness of 83.33 nm, and B is zirconium oxide (ZrO ₂ : refraction). Rate = 2.05) and 65.85n
m and C are hook magnesium (MgF ₂ : refractive index = 1.3)
In 9), it is 97.12 nm. Therefore, the equivalent refraction film unit is laminated 20 times on the back side of the substrate 1, and the antireflection film of this thickness is laminated thereon. The reflection spectral characteristic of this filter is shown in FIG. This is the same as the well-known characteristic of the antireflection film.

[0009]

In summary, according to the present invention, an equivalent refractive film unit having a symmetrical structure having a refractive index substantially equal to that of the substrate 1 is repeatedly laminated on the back surface of the substrate 1 on which the multilayer film 2 is vapor-deposited on the front surface to form a multilayer structure. Since the thickness is substantially equal to that of the film 2, distortion can be removed without impairing the spectral characteristics of the filter. In particular, even in a use environment in which a thermal load from a light source such as a high-definition liquid crystal vision is large, it is possible to maintain the non-curvature as shown in FIG. 1 and eliminate the thermal influence on the liquid crystal panel arranged behind.

[Brief description of drawings]

FIG. 1 is a front view of an embodiment in which an equivalent refraction film unit is laminated on the back surface of a filter.

FIG. 2 is an interference fringe pattern of the filter of FIG.

FIG. 3 is a reflection spectral characteristic diagram of an example in which an equivalent refraction film unit is laminated on the back surface of a filter.

FIG. 4 is a reflection spectral characteristic diagram of an example in which an equivalent refraction film unit is laminated on the back side of a filter and an antireflection film is further laminated thereon.

FIG. 5 is a front view of a conventional dichroic filter.

[Explanation of symbols]

 1 substrate 2 multilayer film 3 multilayer film

Claims (4)

[Claims] 1. A multi-layered film having a thickness substantially equal to that of the multi-layered film and having substantially the same equivalent refractive index as the substrate is deposited on the back side of the substrate having the multi-layered film deposited on the front side. A method for removing distortion of a substrate to be deposited. 2. An equivalent refraction film unit having a symmetrical structure having a refraction index substantially equal to that of the substrate is repeatedly laminated on the back side of a substrate having a multi-layer film vapor-deposited on the front side to obtain a thickness substantially equal to that of the multi-layer film. , Distortion removal method for substrate to be deposited. 3. An equivalent refraction film unit having a symmetrical structure having a refractive index substantially equal to that of this substrate is repeatedly laminated on the back surface of a substrate having a multilayer film deposited on its front surface, and an antireflection film is laminated thereon. A method of removing strain on a substrate to be vapor-deposited so that the thickness is approximately equal to that of the multilayer film. 4. An equivalent refraction film unit having a symmetrical structure having a refraction index substantially equal to that of the substrate is repeatedly laminated on the back side of a substrate having a multi-layer film vapor-deposited on the front side to obtain a thickness substantially equal to that of the multi-layer film. At the same time, a filter that makes the optical film thickness of this equivalent refraction film unit smaller than the spectral wavelength.