JPH07234315A - Optical multilayered film filter - Google Patents

Abstract

PURPOSE:To provide optical multilayered film which have a capacity to shield UV and IF rays and excellent heat resistance and moisture resistance and are producible at a low cost by forming multilayered dielectric films designed to shield the IR rays on a transparent glass substrate having specific UV ray transmittance. CONSTITUTION:This optical multilayered films filter is obtd. by forming the multilayered dielectric films designed to shield the IR rays on the transparent glass substrate, of which the transmittance of the UV rays of a wavelength <=360nm is <=10%. A more preferable embodiment in such a case is the transparent glass substrate consisting of crystallized glass having a coefft. of thermal expansion of -10 to 15X10<-7>/ deg.C at 30 to 750 deg.C. The UV rays are mostly shielded by the transparent glass substrate and the IR rays are mostly shielded by the multilayered dielectric films if such optical multilayered films are used and, therefore, almost only the visible light is eventually transmitted. The glass substrate which is strong to thermal shock and is little in thermal stress is obtd. if crystallized glass of low expansion is particularly selected and, therefore, such substrate is more preferable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical multilayer film filter, and more specifically, it substantially blocks both ultraviolet rays and infrared rays emitted from a light source of a projection type image display device such as a liquid crystal projector or an overhead projector. The present invention relates to an optical multilayer filter having the capability of

[0002]

2. Description of the Related Art Generally, an arc tube such as a metal halide lamp, a xenon lamp or a halogen lamp is used as a light source of a projection type image display device such as a liquid crystal projector or an overhead projector.

Incidentally, in addition to visible light, a large amount of ultraviolet rays and infrared rays are radiated from these arc tubes, and when these radiations are applied to optical parts such as lenses and reflection mirrors of the projection type image display device. , Easily deteriorate optical components.

Therefore, in this type of device, it is required that the ultraviolet rays and infrared rays emitted from the arc tube are shielded before the optical parts are irradiated. Therefore, the ultraviolet ray shielding filter ( For example, a UV cut filter) and an infrared shielding filter (cold filter) are provided, or an optical multilayer film filter in which a dielectric multilayer film having a function of blocking both ultraviolet rays and infrared rays is formed on a transparent glass substrate is provided.

[0005]

However, when the UV cut filter and the cold filter are provided between the arc tube and the optical parts, the number of parts increases and it becomes necessary to perform optical adjustment, resulting in high cost. Cheap.

An optical multilayer filter having a dielectric multilayer film for blocking both ultraviolet rays and infrared rays formed on a transparent glass substrate has 30 or more film layers, resulting in high film formation cost. As a result, the stress of the film becomes large, the film is peeled off due to heat shock or the like, and the moisture in the atmosphere is absorbed, so that the optical characteristics are likely to change greatly.

The present invention has been made in view of the above circumstances, and it has excellent heat resistance and moisture resistance because it has a small film stress while having the ability to shield ultraviolet rays and infrared rays, and can be manufactured at low cost. It is intended to provide a multilayer filter.

[0008]

The optical multilayer filter of the present invention has a transmittance of ultraviolet rays having a wavelength of 360 nm or less of 10 or less.
% Or less, a dielectric multi-layer film designed to block infrared rays is formed on a transparent glass substrate.

In a preferred embodiment of the present invention, the transparent glass substrate has a temperature of 30 to 750 ° C. of −10 to −10.
It is characterized by being made of crystallized glass having a thermal expansion coefficient of 15 × 10 ⁻⁷ / ° C.

[0010]

When the optical multilayer filter of the present invention is used, ultraviolet rays are substantially shielded by the transparent glass substrate and infrared rays are almost shielded by the dielectric multilayer film, so that only visible light is transmitted.

The UV transmittance of glass is mainly determined by its composition, and Fe ₂ O ₃ and TiO ₂ are contained in the glass.
_When components such as ₂ and CeO ₂ are added, the value becomes low and the shielding ability becomes high. Even a normal window glass can obtain such transmittance characteristics if its thickness is considerably increased. However, the ultraviolet transmittance at a wavelength of 360 nm or less is 10 when the thickness is such that it is used as a substrate of an optical multilayer film filter.
In order to obtain glass having a content of not more than%, it is necessary to add the above components in a certain amount or more.

Further, when crystallized glass of low expansion is particularly selected as the material of the glass substrate, it is resistant to heat shock,
Further, a glass substrate having a small thermal strain can be obtained, which is preferable. As such a crystallized glass, SiO ₂ 55-70%, Al ₂ O ₃ 20-35, in weight percentage, is used.
%, Li ₂ O 3-5%, TiO ₂ 1-3%, ZrO
_{2 1~4%, P 2 O 5} 1~5%, Na 2 O 0~4
%, K ₂ O 0 to 4%, β-quartz solid solution crystals are deposited, and the coefficient of thermal expansion at a temperature of 30 to 750 ° C. is −
Crystallized glass of 10 to 15 × 10 ⁻⁷ / ° C. may be mentioned, and since this crystallized glass is excellent in the ability to absorb and block ultraviolet rays by the action of TiO ₂ , it is suitable as the glass substrate of the present invention. is there.

The dielectric multilayer film is formed by alternately stacking a high refractive index material and a low refractive index material. In the present invention, only the ability to shield infrared rays is required, so the number of film layers is small. It is possible to do so, specifically, 10 to 25 layers. As a high refractive index material, TiO 2 is used.
₂ , low-refractive-index materials such as Ta ₂ O ₅ and ZrO ₂ include
SiO ₂ , MgF ₂ or the like is used. Further, a vapor deposition method or a sputtering method is suitable as a method for forming a film of these materials on a substrate.

[0014]

The optical multi-layer film filter of the present invention will be described in detail below based on examples.

First, by weight percentage, SiO ₂ 67%, A
l ₂ O ₃ 23%, Li ₂ O 4%, TiO ₂ 2%,
ZrO ₂ 3%, P ₂ O ₅ 1% composition, 30-
Glass made of transparent crystallized glass (Neoceram N-0 manufactured by Nippon Electric Glass Co., Ltd.) having a coefficient of thermal expansion of −3 × 10 ⁻⁷ / ° C. at a temperature of 750 ° C. and a size of 60 × 90 × 1.3 mm. The substrate was prepared.

Next, a dielectric multilayer film was formed by alternately depositing 15 layers of a low refractive index material (SiO ₂ ) and a high refractive index material (TiO ₂ ) on this glass substrate by a vapor deposition method. This dielectric multilayer film is composed of SiO ₂ and TiO ₂
Are formed by forming films on the glass substrate in the order of the numbers shown in Table 1, and are designed to block infrared rays. The optical film thickness in Table 1 has a central wavelength of 890n.
It was designed under the condition of m.

[0017]

[Table 1]

After producing an optical multilayer filter in which a dielectric multilayer film was formed on a transparent glass substrate in this manner, the transmittance in the ultraviolet region, visible region and infrared region was examined, and the results are shown in FIG. .

The horizontal axis of the graph in FIG. 1 represents wavelength and the vertical axis represents transmittance. As is clear from this graph, wavelength 360
The transmittance in the ultraviolet region of nm or less is 5% or less, and the wavelength is 40.
The transmittance in the visible region of 0 to 700 nm was about 90%, and the transmittance in the near infrared region of wavelength 750 to 1000 nm was 5% or less.

The transmittance is measured by using a spectrophotometer under the condition that the light source is vertically incident on the glass substrate.

In order to examine the heat resistance of this optical multilayer filter, it was placed in an electric furnace and the following (1) to (5)
The heat cycle test was performed in the process. (1) The temperature is raised from room temperature to 450 ° C. at a rate of 20 ° C./minute, held for 5 minutes, and then naturally cooled to 100 ° C. (2) The temperature is raised from 100 ° C. to 450 ° C. at a rate of 20 ° C./minute, held for 5 minutes, and then naturally cooled to 100 ° C. (3) Same as step (2) above. (4) Same as step (2) above. (5) The temperature is raised from 100 ° C. to 500 ° C. at a rate of 20 ° C./min, held for 5 minutes, and then naturally cooled to room temperature.

Observation of the optical multi-layer film filter after the thermal cycle test revealed that no abnormality such as film peeling was observed and the heat resistance was excellent.

[0023]

As described above, the optical multi-layer film filter of the present invention has the ability to substantially shield both ultraviolet rays and infrared rays, but has a small film stress, and therefore has excellent heat resistance and moisture resistance,
Moreover, it can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a graph showing a transmittance curve of an optical multilayer filter of the present invention.

Claims (2)

[Claims] 1. An optical system comprising a transparent glass substrate having a transmittance of 10% or less for ultraviolet rays having a wavelength of 360 nm or less and a dielectric multilayer film designed to shield infrared rays. Multilayer filter. 2. The transparent glass substrate is made of crystallized glass having a coefficient of thermal expansion of −10 to 15 × 10 ⁻⁷ / ° C. at a temperature of 30 to 750 ° C.
Optical multilayer filter.