JP2006323259A - Optical filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical filter that can achieve the shortening of film forming processing time and reduction of product costs by simplifying the film forming process of an ND filter and a transmitted light selection filter. <P>SOLUTION: A filter coating layer 14 is provided on one face of a transparent substrate 12 constituting the optical filter 10. This filter coating layer 14 has an ND filter function for controlling the transmittance of the light in a visible light band, and a transmitted light selection filter function for selecting a wavelength of the transmitted visible light. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical filter used in a projection display device and the like. More specifically, the present invention relates to a composite filter function having an ND (Neutral Density) filter function for controlling transmittance and a color selection function (transmitted light selection function). The present invention relates to an optical filter.

In a projection type color display device (projector device), as means for controlling the color balance of an enlarged image that is enlarged and projected on a screen, that is, the color balance of the three primary colors R (red), G (green), and B (blue). There is an optical filter, and this optical filter adjusts the amount of transmitted light for each of RGB to enable color balance (see Patent Documents 1, 2, and 3).
In addition, for such an optical filter, an ND filter function having a non-selective transmittance that almost uniformly transmits each wavelength in the visible spectral range of the light beam and a wavelength of transmitted light (RGB wavelength) are selected. A transmitted light selection filter function is required. Hereinafter, description will be given with reference to the drawings.

FIG. 9 is a schematic cross-sectional view showing an example of the configuration of a conventional optical filter.
As shown in FIG. 9, the optical filter 90 includes a transmitted light selection filter 91 and an ND filter 92 that are separately formed, and these are arranged on the optical path of visible light.
The transmitted light selection filter 91 includes a flat transparent substrate 91a made of glass or the like, and a transmitted light selection filter coat layer 91b formed on one surface of the transparent substrate 91a.
The transmitted light selection filter coat layer 91b selectively transmits light in a region corresponding to the wavelength of R (red), G (green), or B (blue), for example, from the wavelength in the visible spectrum region. (Red), G (Green), or B (Blue) is composed of a metal film suitable for wavelength selection.
The ND filter 92 is composed of a flat transparent substrate 92a made of glass or the like, and an ND filter coat layer 92b formed on one surface of the transparent substrate 91a. The ND filter coat layer 92b is configured by alternately laminating dielectric films and light absorption films.

In such an optical filter 90, when visible light is incident on the transmitted light selection filter 91, the transmitted light selection filter coat layer 91b is a region corresponding to the wavelength of R (red), G (green), or B (blue). One of the lights is selected and transmitted. In this embodiment, light corresponding to the wavelength of B (blue) is selected. The transmission spectrum at this time is shown in FIG.
When the selection light selected by the transmitted light selection filter 91 is incident on the ND filter 92, the transmittance of the selection light is adjusted by the ND filter 92. The transmission spectrum at this time is shown in FIG.

FIG. 11 is a schematic cross-sectional view showing another example of the configuration of a conventional optical filter.
An optical filter 100 shown in FIG. 11 includes a flat transparent substrate 101 made of glass or the like, a transmitted light selection filter coat layer 102 formed on a light incident side surface of the transparent substrate 101, and a transparent substrate 101. And an ND filter coat layer 103 formed on the light emitting side surface.

In such an optical filter 100, visible light incident on the optical filter 100 is transmitted by the transmitted light selection filter coat layer 102, and 1 of the light in the region corresponding to the wavelength of R (red), G (green), or B (blue). Select one. In this embodiment, light corresponding to the wavelength of B (blue) is selected.
Further, the transmittance of the selected light selected by the transmitted light selection filter coat layer 102 is adjusted by the ND filter coat layer 103. The transmission spectrum at this time is shown in FIG.

Next, a manufacturing method in the case where the transmitted light selection filter coat layer 102 and the ND filter coat layer 103 are formed on the transparent substrate 101 of the optical filter 100 shown in FIG. 11 will be described with reference to FIG.
A sputtering method is used to form the transmitted light selection filter coat layer and the ND filter coat layer on the transparent substrate 101 in the optical filter 100.

First, the transparent base material 101 is set on the carrier carried out of the chamber constituting the sputtering apparatus, and this transparent base material is carried into the chamber together with the carrier. This operation is the transparent substrate filling step S11. The time required for this filling step S11 is about 10 to 30 minutes.
Next, a discharge gas (for example, argon) necessary for forming a transmitted light selection filter coat layer is introduced into the chamber and the chamber is evacuated to a vacuum. This operation is the evacuation step S12, and the time required for this step is about 20 to 40 minutes.
A gas plasma is generated in such a reduced-pressure gas atmosphere, the ionized gas is irradiated onto the target material for forming the coating layer, and particles that have jumped out of the target material due to the impact are attached to the surface of the transparent substrate 101, thereby allowing transmission. A light selective filter coat layer is formed. This operation is the transmitted light selective film forming step S13, and the time required for this step is about 100 to 200 minutes.

Next, when the formation of the transmitted light selection filter coat layer on the transparent substrate 101 is completed, the transparent substrate 101 is carried out of the chamber together with the carrier, and the transparent substrate 101 is turned over to transmit the transmitted light selection filter coat. The surface of the layer where no film is formed is listed. This operation is the transparent substrate reversing step S14, and the time required for this step is about 10 to 30 minutes.
Next, a discharge gas (for example, O ₂ , N _2, etc.) necessary for forming the ND filter coat layer is introduced into the chamber and the chamber is evacuated to a vacuum. This operation is the evacuation step S15, and the time required for this step is about 20 to 40 minutes.
By creating a gas plasma in such a reduced pressure gas atmosphere, irradiating the ionized gas onto the target material for forming the coating layer, and attaching particles ejected from the target material by the impact to the back surface of the transparent substrate 101, ND A filter coat layer is formed. This operation is the ND film forming step S16, and the time required for this step is about 5 to 15 minutes.
When film formation of the ND filter coat layer on the transparent substrate 101 is completed, the transparent substrate 101 is carried out of the chamber together with the carrier, and the transparent substrate 101 is taken out from the carrier. This operation is the transparent substrate taking process S17, and the time required for this process is about 10 to 30 minutes.
JP 2004-287302 A JP 2002-107509 A JP 2003-43211 A

However, when an optical filter having a configuration as shown in FIG. 9 is used, one or more ND filters for controlling transmitted light are required in the projector device, which increases the number of parts and increases the cost. Problems such as a complicated assembly process occur.
In order to reduce the number of parts, an ND filter coat layer for controlling transmitted light and a transmitted light selection filter coat layer are separately provided on both surfaces of the transparent substrate, as in the optical filter shown in FIG. The number of parts is reduced.
However, in the optical filter having such a structure, since it is necessary to coat a thin film on both surfaces of the transparent substrate, the manufacturing process becomes complicated as described with reference to FIG. It is not possible to promote the compounding of functions that reduce the number of functions.

In addition, in the conventional optical filter, in order to provide the functions of an ND filter and a transmitted light selection filter, it is necessary to create the ND filter and the transmitted light selection filter by separate processes. For this reason, at the time of film formation of the ND filter, metal nitride or Cr is used, and it is difficult to manufacture with the same film forming apparatus.
In addition, transparent dielectrics are usually laminated in order to provide a selective light transmission function, but these are metal oxides. When forming nitrides and oxides in a thin film deposition apparatus, an introduced gas is used. Since it is necessary to substitute, it is not practical to alternately form nitride and oxide metal in the same film formation chamber.

  The present invention has been made in view of such circumstances, and an object thereof is to simplify the film formation process of the ND filter and the transmitted light selection filter, thereby shortening the film formation process time and reducing the cost of the product. In addition, an object of the present invention is to provide an optical filter that can easily realize multi-function filter products.

  In order to achieve the above object, an optical filter of the present invention has a transparent base material having at least one surface formed as a flat surface, and an ND filter function for controlling the transmittance of a visible light band on the flat surface of the transparent base material. A filter coat layer having a transmitted light selection filter function for selecting the wavelength of visible light is provided.

  According to the optical filter of the present invention, since the filter coat layer having both functions of the ND filter and the transmitted light selection filter is provided on one side which is a flat surface of the transparent base material, the film formation location of the filter coat layer is a transparent substrate. Only one side of the material is required, and accordingly, the film forming process time of the ND filter and the transmitted light selection filter on the transparent substrate can be shortened, and the cost of the optical filter product can be reduced, and the filter coat layer It is possible to add an optical function such as a lens function or a polarization function to the other surface of the transparent substrate on which no is formed, and thus a single optical filter can be multifunctional.

(Embodiment 1)
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of the configuration of an optical filter according to an embodiment of the present invention.
As shown in FIG. 1, the optical filter 10 is provided on a transparent substrate 12 made of glass or the like, one surface of which is a flat surface or a surface in which both surfaces are parallel to each other, and one surface of the transparent substrate 12. And a filter coat layer 14.
The filter coat layer 14 has R (red), G (green) or B (blue) based on the ND filter function for controlling the transmittance of light in the visible light band corresponding to 400 nm to 700 nm and the wavelength of the visible light to be transmitted. ) And a transmitted light selection filter function for selecting one of the light in the region corresponding to the wavelength.
Further, the transmitted light selection filter function of the filter coat layer 14 includes a first dielectric film (Nb ₂ O ₅ , TiO ₂ , Ta ₂ O _5, etc.) made of a transparent dielectric material having a high refractive index, and a low refractive index. The second dielectric film (SiO ₂ or the like) made of the transparent dielectric material is alternately laminated one or more layers.

The filter coat layer 14 in such an optical filter 10 is designed by a method already established, for example, an optical simulation. For example, a case where a filter that passes a wavelength in a G (green) band (500 to 560 nm) is designed will be described.
First, filter design values are described in FIG. In FIG. 2, layer numbers 1 to 34 indicate the order of film formation from the transparent substrate 12. The film forming materials and physical film thicknesses (nm) for the layer numbers 1 to 34 are as shown in FIG. Further, the transmission spectrum at this time is as shown in FIG.

On the other hand, a layer number 34 between a certain layer, for example, a first dielectric film Nb ₂ O ₅ corresponding to the layer number 33 and a second dielectric film SiO ₂ corresponding to the layer number 35. A Nb metal film is inserted at a position corresponding to. The filter coat layer 14 at this time has design values as shown in FIG. Further, in FIG. 4, layer numbers 1 to 35 indicate the order of film formation from the transparent substrate 12, and the film forming materials and physical film thicknesses (nm) for the layer numbers 1 to 35 are shown in FIG. Street. Further, the transmission spectrum at this time is as shown in FIG.

Thus, between the laminated films of the first dielectric film Nb ₂ O ₅ corresponding to the layer number 33 near the incident side of the visible light with respect to the filter coat layer 14 and the second dielectric film SiO ₂ corresponding to the layer number 35. The average transmittance of the G (green) band (500 to 560 nm) is 68.6% while the transmittance without the ND filter function is 98.9%. It becomes. And the average transmittance | permeability can be arbitrarily adjusted with the film thickness of a metal film.

Next, a manufacturing method in the case where the filter coat layer 14 is formed on the transparent substrate 12 of the optical filter 10 shown in FIG. 1 will be described with reference to FIG.
A sputtering method is used to form a filter coat layer on the transparent substrate 12 in the optical filter 10.

First, the transparent base material 12 is set on the carrier carried out of the chamber constituting the sputtering apparatus, and this transparent base material 12 is carried into the chamber together with the carrier. This operation is the transparent substrate filling step S21. The time required for this filling step S21 is about 10 to 30 minutes.
Next, a discharge gas (for example, a gas such as O ₂ , N _2, or argon) necessary for forming the transmitted light selection filter coat layer is introduced into the chamber, and the chamber is evacuated to a vacuum. This operation is the evacuation step S22, and the time required for this step is about 20 to 40 minutes.

A gas plasma is generated in such a reduced-pressure gas atmosphere, and ionized gas is irradiated onto a target material (Nb, Si, etc.) for forming a coat layer, and particles that have jumped out of the target material due to the impact are applied to the surface of the transparent substrate 12 By attaching them, the first dielectric film Nb ₂ O ₅ and the second dielectric film SiO ₂ of the filter coat layer 14 are sequentially and alternately formed according to the layer numbers shown in FIG. In the process corresponding to the layer number 34, a discharge gas (for example, argon) different from that used when forming the first dielectric film Nb ₂ O ₅ and the first dielectric film Nb ₂ O ₅ is introduced. A gas plasma is generated in a reduced-pressure gas atmosphere, and an ionized gas is irradiated onto a target material (Nb or the like) for forming a coat layer. A metal film for an ND filter is formed by depositing on the surface of the film Nb ₂ O ₅ . Thereafter, a second dielectric film SiO ₂ corresponding to the layer number 35 is formed on the surface of the metal film. The operation at this time is the surface film forming step S23, and the time required for this step is about 100 to 200 minutes.
When the film formation of the filter coat layer 14 on the transparent substrate 121 is completed, the transparent substrate 12 is carried out of the chamber together with the carrier, and the transparent substrate 12 is taken out of the carrier. This operation is the transparent substrate taking step S24, and the time required for this step is about 10 to 30 minutes.

  In this embodiment, since the filter coat layer 14 having both functions of the ND filter and the transmitted light selection filter is provided on one surface of the transparent substrate 12, the film coating location of the filter coat layer 14 is provided. Requires only one side of the transparent substrate 12, and accordingly, the film formation process time of the ND filter and the transmitted light selection filter on the transparent substrate 12 is compared to the conventional process as shown in FIG. S14 to S16 can be omitted, and the manufacturing time can be shortened by about 170 to 300 minutes. Thereby, the productivity of the optical filter is improved, and the cost of the product can be reduced.

In the first embodiment, the case where the present invention is applied to a G (green) band-pass filter has been described. However, the present invention is not limited to this, and the present invention is not limited to this, but can be applied to an R (red) or B (blue) band-pass filter. Can also be applied.
Further, the ND filter metal film interposed between the first dielectric film Nb ₂ O ₅ and the first dielectric film Nb ₂ O ₅ is provided at one place as shown in the above embodiment. It is not restricted and two or more places may be sufficient.
Further, in this first embodiment, first dielectric layer Nb ₂ O ₅ and the first dielectric layer Nb ₂ O ₅ is an incident-side side of the visible light intervention point of the metal film for the ND filter to the filter coating layer 14 The ND filter metal film is interposed between the first dielectric film Nb ₂ O ₅ and the first dielectric film Nb ₂ O ₅ other than the outermost layer of the filter coat layer 14. And any location between the laminated structures.
The reason why the metal film is provided between the laminated structures other than the outermost layer of the filter coat layer 14 is to prevent the metal film from being oxidized and to prevent the ND filter function from being deteriorated.

Further, the embodiment according to the present invention is characterized in that the functions of a transmitted light selection filter and an ND filter are realized by a sputtering apparatus that can use two types of target materials.
In this case, since the types of targets that can be mounted on the sputtering apparatus (film forming apparatus) are limited (usually about 1 to 4, excluding special objects), it is very significant that it can be made with two types of targets. is there. In order to achieve this, in the present invention, transparent dielectric films SiO ₂ and Nb ₂ O ₅ and Nb which is a metal film thereof are used. Also, this can be combined with other metals. When TiO ₂ is used, an ND film can be formed by using a Ti metal film, and when using SiO ₂ , an Si metal film. It becomes possible.

(Embodiment 2)
Next, another embodiment of the optical filter according to the present invention will be described with reference to FIG.
FIG. 7 is a schematic cross-sectional view when an optical lens function is added to the optical filter.
In FIG. 7, the transparent substrate 22 of the optical filter 10 has a surface 22a on which the filter coat layer 14 is formed and a convex optical lens 22b formed on the surface opposite to the plane 22a.

  Usually, in a plano-convex lens in which one is a flat surface and the other is convex, a film having a transmitted light selection filter function or an ND filter function cannot be formed on the convex surface. This is because when the thin film is coated on the convex surface, the coating film thickness has a distribution due to the influence of the curved surface, so that a desired transmission wavelength region cannot be obtained with a transmitted light selection filter. Moreover, if it is an ND filter, it is because a uniform transmittance | permeability cannot be obtained because a film thickness will change. Therefore, with the conventional method, it has been impossible to impart functions to the transmitted light selection filter and the ND filter with respect to the plano-convex lens. However, it becomes possible to produce a plano-convex lens having both functions by coating the thin film of the present invention.

(Embodiment 3)
Next, still another embodiment of the optical filter according to the present invention will be described with reference to FIG.
FIG. 8 is a schematic cross-sectional view when an optical polarization function is added to the optical filter.
In FIG. 8, the transparent substrate 12 of the optical filter 10 has a plane in which both surfaces are parallel to each other, and an ND filter that controls the transmittance of light in the visible light band is provided on one surface of the transparent substrate 12. A filter coat layer 14 having a function and a transmitted light selection filter function for selecting the wavelength of visible light to be transmitted is provided. A polarizing film 16 is provided on the other surface of the transparent substrate 12.

  In general, there is a member for attaching a film material inside the liquid crystal projector. This is the polarizing film glass in front of the liquid crystal panel. By using the optical filter according to the present invention for this polarizing film glass, it becomes possible to create a multifunction filter having a polarizing function, a selective light transmission function, and an ND filter function.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the summary described in the claim, it can implement also with another various form.

It is typical sectional drawing which shows an example of a structure of the optical filter in embodiment of this invention. It is a figure which shows the design value of the band pass filter which permeate | transmits the green band of the optical filter in this Embodiment. It is a transmission spectrum figure of the band pass filter which permeate | transmits the green band of the optical filter in this Embodiment. It is a figure which shows the design value at the time of interposing the metal film in the band pass filter which permeate | transmits the green zone | band of the optical filter in this Embodiment. It is a transmission spectrum figure at the time of interposing a metal film in the band pass filter which permeate | transmits the green zone | band of the optical filter in this Embodiment. It is process explanatory drawing which shows the manufacturing method in the case of forming a filter-coat layer into the transparent base material of the optical filter in this Embodiment. It is typical sectional drawing which shows the other Example of the optical filter in embodiment of this invention. It is typical sectional drawing which shows other embodiment of the optical filter concerning this invention. It is typical sectional drawing which shows an example of a structure of the conventional optical filter. It is a transmission spectrum figure of the conventional optical filter. It is typical sectional drawing which shows the other example of a structure of the conventional optical filter. It is a transmission spectrum figure of the optical filter shown in the other conventional example. It is process explanatory drawing which shows the manufacturing method in the case of forming the filter coat layer of the conventional optical filter into a film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Optical filter, 12 ... Transparent base material, 14 ... Filter coat layer, 22 ... Transparent base material, 22b ... Optical lens, 16 ... Polarizing film.

Claims (8)

A transparent base material on which at least one surface is flat;
A filter coat layer having an ND filter function for controlling the transmittance of the visible light band and a transmitted light selection filter function for selecting the wavelength of the visible light to be transmitted is provided on the plane of the transparent substrate.
An optical filter characterized by the above.   The transmitted light selection filter function of the filter coat layer is such that a first dielectric film made of a transparent dielectric material having a high refractive index and a second dielectric film made of a transparent dielectric material having a low refractive index are alternately alternated. The optical filter according to claim 1, wherein the optical filter is configured by stacking.   2. The optical filter according to claim 1, wherein the ND filter function of the filter coat layer is constituted by at least one metal film.   The transmitted light selection filter function of the filter coat layer is such that a first dielectric film made of a transparent dielectric material having a high refractive index and a second dielectric film made of a transparent dielectric material having a low refractive index are alternately alternated. The ND filter coat layer has an ND filter function of at least one layer of metal film, and the metal film is between the stacked structure of the first dielectric film and the second dielectric film. The optical filter according to claim 1, wherein the optical filter is interposed between the optical filter and the optical filter.   5. The optical filter according to claim 4, wherein the metal film is interposed between a laminated structure of the first dielectric film and the second dielectric film other than the outermost layer of the filter coat layer.   The optical filter according to claim 4, wherein the first and second transparent dielectrics are oxides of a metal material constituting the metal film.   The optical filter according to claim 1, wherein the transparent substrate is an optical lens, and a surface of the optical lens on which the filter coat layer is formed is a flat surface.   The optical filter according to claim 1, wherein a polarizing film is provided on the other surface of the transparent substrate.

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