JP2007078779A - Cross dichroic prism, optical device, projector, and manufacturing method for cross dichroic prism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cross dichroic prism capable of displaying excellent video. <P>SOLUTION: On the cross dichroic prism 34, a blue light reflective film 343A and a red light reflective film 343B are formed crossing in a nearly X shape along flanks of four dichroic prisms 341 which are joined on their flanks with adhesives. The red light reflective film 343B is formed continuously without being divided at an intersection position of the nearly X shape. The red light reflective film 343B is provided with a gas barrier layer 343B1 formed as a first layer in contact with a reflective film formation surface 342D. Consequently, a multi-layered film 343B2 is formed after the gas barrier layer 343B1 is formed on a second prism pair 345B, and then an adhesion layer 344 is never exposed to an atmosphere wherein the multi-layered film 343B2 is vaporized, thereby suppressing deterioration and degeneration of the adhesion layer 344. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cross dichroic prism including four triangular prisms, an optical device including the cross dichroic prism, a projector including the optical device, and a method of manufacturing the cross dichroic prism.

  Conventionally, a manufacturing method of a cross dichroic prism that combines and separates colors of light is known (see, for example, Patent Document 1 and Patent Document 2).

The one described in Patent Document 1 is provided with four right-angle prisms whose two side surfaces constituting the right-angle surface are polished flatly, and an inorganic thin film is formed in multiple layers on the right-angle surfaces of the two right-angle prisms. A blue reflective film is formed by vacuum deposition or sputtering. A right-angle surface of the right-angle prism formed with the blue reflection film and a right-angle surface of the right-angle prism not formed with the blue reflection film are bonded with an adhesive to produce a first prism pair. Further, a second prism pair is produced by the same method.
After that, the joint surface of the first prism pair is processed to be flat by polishing, and the flat joint surface is formed of a single film in which a red reflection film is continuously formed by vapor deposition or sputtering. To form. Further, the second prism pair and the first prism pair are bonded together with an adhesive. Then, a cross dichroic prism is manufactured by cutting out a prism having a desired length from the prism column thus manufactured.

The one described in Patent Document 2 optically polishes one of the inclined surfaces sandwiching the right angle with the bottom surface of each of the first to fourth prisms, and polishes each of the first and third prisms. A first light reflecting dichroic film is formed on the sloped surface. Further, a first joining member in which the first light reflecting dichroic film forming surface of the first prism and the polished slope of the second prism are joined with an adhesive, and the first light reflecting dichroic of the third prism A second joining member is produced by joining the film forming surface and the polished slope of the fourth prism with an adhesive.
Thereafter, the bottom surfaces of the first bonding member and the second bonding member are optically polished, and a second light reflecting dichroic film is formed on one of the bottom surfaces by a physical vapor deposition method such as a vacuum vapor deposition method. And the 2nd light reflection dichroic film | membrane and grinding | polishing surface of the bottom face of a 1st joining member and a 2nd joining member are joined with an adhesive agent.

JP 11-352440 A (page 6 left column-page 8 right column) JP-A-10-311907 (right column on page 3-left column on page 5)

However, in the configurations such as Patent Document 1 and Patent Document 2, when the wavelength-selective reflective film is formed after joining the two triangular prisms with the adhesive, the adhesive is formed from the surface on which the wavelength-selective reflective film is formed. Since this layer (hereinafter referred to as an adhesive layer) is exposed, there is a possibility that the adhesive layer is exposed to the atmosphere of vapor deposition and deteriorates or deteriorates. For this reason, there is a problem that the optical characteristics of the deteriorated or altered portion deviate from the target quality specification, which may have a significant adverse effect on the image quality and may be one factor for reducing the yield.
In particular, the portion where the adhesive layer and the wavelength selective reflection film formed when two triangular prisms are joined is located at the center of the cross dichroic prism, so that a projector using the cross dichroic prism displays the portion. The quality at the center of the image may be deteriorated, resulting in a serious quality defect.

  An object of the present invention is to provide a cross dichroic prism, an optical device, a projector, and a method of manufacturing a cross dichroic prism capable of displaying a good image.

  The cross dichroic prism of the present invention is a cross dichroic prism having two types of wavelength-selective reflective films that intersect in a substantially X-shape and are each composed of a plurality of layers. A triangular prism, and two wavelength selective reflection films formed so as to intersect in a substantially X shape along the side surfaces of the four triangular prisms, and one of the two wavelength selective reflection films Is formed continuously without being divided at the substantially X-shaped crossing position, and the first layer in contact with the triangular prism of the wavelength-selective reflecting film formed continuously functions as a gas barrier layer. It is characterized by that.

According to the present invention, two types of wavelength-selective reflecting films composed of a plurality of layers are formed so as to intersect in a substantially X shape along the side surfaces of the four triangular prisms joined to each other by an adhesive. is doing. Further, one of the two wavelength-selective reflecting films is continuously formed without being divided at the substantially X-shaped intersection position. The first layer that is in contact with the triangular prism of the wavelength-selective reflecting film that is continuously formed functions as a gas barrier layer.
For this reason, after joining the two triangular prisms with the adhesive, the first layer functioning as the gas barrier layer is formed, and then the second and subsequent multilayer films are formed, and the adhesive layer is on the first layer. No exposure to the atmosphere for depositing the multilayer film. Therefore, the deterioration and alteration of the adhesive layer can be suppressed, the image quality is not adversely affected, and a good image can be displayed.

  In the cross dichroic prism of the present invention, it is preferable that the first layer is formed of a metal oxide that transmits visible light.

According to this invention, the first layer is formed of a metal oxide that transmits visible light.
For this reason, the first layer can be easily formed by vapor deposition or sputtering.

Furthermore, in the cross dichroic prism of the present invention, the metal oxide is preferably a silicon oxide represented by a general formula of SiO _x and 0.8 ≦ x ≦ 1.7.

According to this invention, the silicon oxide represented by the general formula of SiO _x and 0.8 ≦ x ≦ 1.7 is applied as the metal oxide.
For this reason, for example, silicon oxide (SiO ₂ ) having a value of x larger than 1.7 is applied as the first layer metal oxide, and silicon oxide having a value of x smaller than 0.8 is used. Compared with the structure applied as a single-layer metal oxide, the oxygen permeability can be lowered. Accordingly, it is possible to further suppress deterioration and deterioration of the adhesive layer.

  In the cross dichroic prism of the present invention, the metal oxide is preferably aluminum oxide.

According to this invention, aluminum oxide is applied as the metal oxide.
For this reason, compared with the structure which uses a silicon oxide as a metal oxide of a 1st layer, it becomes possible to reduce the permeability | transmittance of oxygen. Accordingly, it is possible to further suppress deterioration and deterioration of the adhesive layer. Further, by forming a dense multilayer film on the first layer by ion-assisted vapor deposition, it is possible to stabilize the optical characteristics and display a better image. Furthermore, since low temperature vapor deposition is possible, an adhesive agent can be selected easily.

  The optical device according to the present invention includes the cross dichroic prism, a liquid crystal panel disposed close to three of the four surfaces located outside the cross dichroic prism, and the four of the cross dichroic prism. And a projection lens arranged to face a surface other than the three surfaces among the surfaces.

  Furthermore, a projector according to the present invention includes the above-described optical device.

According to these inventions, the above-described cross dichroic prism capable of displaying a good image is provided in the optical device and the projector.
Therefore, it is possible to provide an optical device and a projector that can project a good image.

  The cross dichroic prism manufacturing method of the present invention is the cross dichroic prism manufacturing method described above, wherein the multilayer film formed on the first layer is formed by vapor deposition accompanied with ion assist. To do.

According to this invention, the multilayer film formed on the first layer is formed by the ion-assisted vapor deposition method with ion assist.
For this reason, a multilayer film is formed on the first layer by an ion-assisted deposition method that can form a dense film and can be deposited at a low temperature, so that the optical characteristics can be stabilized and a better image can be displayed. It becomes possible.
Moreover, since low temperature vapor deposition is possible, even if there is a constraint that the refractive index of the adhesive is the same as that of the glass of the triangular prism base material, the adhesive can be easily selected.

  Hereinafter, a projector according to an embodiment of the invention will be described with reference to the drawings.

[Projector configuration]
FIG. 1 is a diagram schematically showing an optical system provided in a projector according to an embodiment of the present invention. FIG. 2 is a perspective view schematically showing a cross dichroic prism. FIG. 3 is a cross-sectional view schematically showing a cross section of the cross dichroic prism on the optical axis plane.

  In FIG. 1, a projector 1 modulates a light beam emitted from a light source in accordance with image information, and enlarges and projects it on a projection surface such as a screen. The projector 1 includes an exterior case (not shown), an optical unit 2, and a power supply unit and a cooling unit (not shown).

  The optical unit 2 is functionally broadly divided into an integrator illumination optical system 21, a color separation optical system 22, a relay optical system 23, an optical device 3, and an optical component housing 25.

  The integrator illumination optical system 21 is an optical system for making the luminous flux emitted from the light source uniform in the illumination optical axis orthogonal plane. The integrator illumination optical system 21 includes a light source device 211, a first lens array 212, a second lens array 213, a polarization conversion element 214, and a superimposing lens 215.

  The light source device 211 includes a light source lamp 216 and a reflector 217. Then, the radial light flux emitted from the light source lamp 216 is reflected by the reflector 217 to become a substantially parallel light flux, and is emitted to the outside. In the present embodiment, a high-pressure mercury lamp is used as the light source lamp 216, and a parabolic mirror is used as the reflector 217. The light source lamp 216 is not limited to a high-pressure mercury lamp, and for example, a metal halide lamp or a halogen lamp may be employed. Moreover, although the parabolic mirror is employ | adopted as the reflector 217, it is not restricted to this, You may employ | adopt the structure which has arrange | positioned the collimating concave lens in the exit surface of the reflector which consists of an ellipsoidal mirror.

  The first lens array 212 has a configuration in which small lenses having a substantially rectangular outline when viewed from the illumination optical axis direction are arranged in a matrix. Each small lens divides the light beam emitted from the light source lamp 216 into partial light beams and emits them in the direction of the illumination optical axis.

  The second lens array 213 has substantially the same configuration as the first lens array 212, and includes a configuration in which small lenses are arranged in a matrix. The second lens array 213 has a function of forming an image of each small lens of the first lens array 212 on a liquid crystal panel 31 (to be described later) of the optical device 3 together with the superimposing lens 215.

  The polarization conversion element 214 converts the light from the second lens array 213 into substantially one type of polarized light, thereby improving the light use efficiency in the optical device 3. Specifically, each partial light beam converted into approximately one type of polarized light by the polarization conversion element 214 is finally substantially superimposed on a liquid crystal panel 31 (to be described later) of the optical device 3 by the superimposing lens 215. In a projector using a liquid crystal panel 31 of a type that modulates polarized light, only one type of polarized light can be used, and therefore approximately half of the light flux from the light source lamp 216 that emits randomly polarized light is not used. For this reason, by using the polarization conversion element 214, the light beam emitted from the light source lamp 216 is converted into substantially one type of polarized light, and the light use efficiency in the optical device 3 is enhanced. Such a polarization conversion element 214 is introduced in, for example, Japanese Patent Application Laid-Open No. 8-304739.

  The color separation optical system 22 includes two dichroic mirrors 221 and 222 and a reflection mirror 223. A plurality of partial light beams emitted from the integrator illumination optical system 21 are separated into three color lights of red (R), green (G), and blue (B) by two dichroic mirrors 221 and 222.

  The relay optical system 23 includes an incident side lens 231, a relay lens 233, and reflection mirrors 232 and 234. The relay optical system 23 has a function of guiding the blue light, which is the color light separated by the color separation optical system 22, to a blue light liquid crystal panel 31 described later of the optical device 3.

  At this time, in the dichroic mirror 221 of the color separation optical system 22, among the light beams emitted from the integrator illumination optical system 21, the blue light component and the green light component are transmitted, and the red light component is reflected. The red light reflected by the dichroic mirror 221 is reflected by the reflection mirror 223, passes through the field lens 218, and reaches a later-described red light liquid crystal panel 31. The field lens 218 converts each partial light beam emitted from the second lens array 213 into a light beam parallel to the central axis (principal ray). The same applies to the field lens 218 provided on the light incident side of the other liquid crystal panel 31 for green light and blue light.

  Of the blue light and green light transmitted through the dichroic mirror 221, the green light is reflected by the dichroic mirror 222, passes through the field lens 218, and reaches a later-described green light liquid crystal panel 31. On the other hand, the blue light passes through the dichroic mirror 222, passes through the relay optical system 23, passes through the field lens 218, and reaches a liquid crystal panel 31 for blue light to be described later.

  The relay optical system 23 is configured to pass blue light out of the three color lights, but is not limited thereto, and may be configured to pass red light, for example.

  The optical device 3 modulates an incident light beam according to image information to form a color image (optical image), and enlarges and projects the formed color image. As shown in FIG. 1, the optical device 3 includes three liquid crystal panels 31 (a liquid crystal panel for red light 31R, a liquid crystal panel for green light 31G, and a liquid crystal panel for blue light 31B), The liquid crystal panel 31 includes an incident side polarizing plate 32 and an optical conversion plate 33, a cross dichroic prism 34, a head body 4, and a projection lens 5 that are disposed to face the light beam incident side and the light beam emission side, respectively. Of these, the three liquid crystal panels 31, the three optical conversion plates 33, and the cross dichroic prism 34 are integrated to form the optical device body 30. The optical device main body 30 includes a holding frame for holding the liquid crystal panel 31 and a second optical conversion plate 33B in addition to the liquid crystal panel 31, the optical conversion plate 33, and the cross dichroic prism 34. A holding member that holds the liquid crystal panel 31 to the cross dichroic prism 34 is provided.

  The incident-side polarizing plate 32 receives light of each color whose polarization direction is aligned in substantially one direction by the polarization conversion element 214, and is substantially the same as the polarization axis of the light beam aligned by the polarization conversion element 214 among the incident light beams. Only polarized light in the direction (first polarization direction) is transmitted, and other light beams are absorbed. Although not shown, the incident-side polarizing plate 32 has a configuration in which a polarizing film is pasted on a translucent substrate. In the present embodiment, the incident-side polarizing plate 32 is configured separately from the optical device main body 30, but may be configured to be integrated with the optical device main body 30. In addition, a configuration in which a polarizing film is attached to the field lens 218 without using a translucent substrate may be employed.

  Although not shown, the liquid crystal panel 31 has a configuration in which a liquid crystal, which is an electro-optical material, is hermetically sealed between a pair of transparent glass substrates, and the liquid crystal panel 31 includes a liquid crystal panel 31 according to a drive signal output from the control substrate. The orientation state is controlled, and the polarization direction of the polarized light beam emitted from the incident side polarizing plate 32 is modulated.

  The optical conversion plate 33 includes a first optical conversion plate 33A and a second optical conversion plate 33B.

  The first optical conversion plate 33A has substantially the same configuration as the above-described incident-side polarizing plate 32, and transmits only polarized light in a predetermined direction (second polarization direction) among the incident light beams, and other light beams. It absorbs.

  The second optical conversion plate 33B transmits only polarized light in a predetermined direction among the light beams emitted from the liquid crystal panel 31, absorbs other light beams, and enlarges the viewing angle of the light beams emitted from the liquid crystal panel 31. To do.

  The cross dichroic prism 34 combines the red light, the blue light, and the green light incident from the optical conversion plate 33 to form a color image and outputs the color image to the projection lens 5. A detailed description of the cross dichroic prism 34 will be described later.

  The projection lens 5 is disposed such that the tip portion can be exposed from an exterior case (not shown), and enlarges and projects the color image formed by the cross dichroic prism 34. The projection lens 5 is configured as a combined lens in which a plurality of lenses are housed in a cylindrical lens barrel. In addition, the projection lens 5 may be provided with a lever for changing the relative positions of the plurality of lenses so that the focus of the projected image can be adjusted and the magnification can be adjusted.

  The head body 4 is made of a metal material such as an aluminum alloy or a magnesium alloy, and integrates the optical device main body 30 and the projection lens 5 and attaches the integrated unit to the optical component housing 25. is there.

  The optical component casing 25 is a molded product made of synthetic resin, and a predetermined illumination optical axis is set therein, and the optical components 31 to 34 described above are arranged at predetermined positions with respect to the illumination optical axis. The optical component housing 25 is not limited to a synthetic resin molded product, but may be composed of a metal member.

[Configuration of cross dichroic prism]
The cross dichroic prism 34 is an optical element that includes three incident end faces on which the respective color lights emitted from the optical conversion plate 33 are incident, and forms a color image by combining optical images modulated for the respective color lights. As shown in FIG. 2, the cross dichroic prism 34 is formed in a square shape in plan view by bonding the apex angles of dichroic prisms 341 as four triangular prisms close to the center. That is, the red light side dichroic prism 341A on which red light from the liquid crystal panel 31R for red light enters, the blue light side dichroic prism 341B on which blue light from the liquid crystal panel 31B for blue light enters, and the green light enter. The green light side dichroic prism 341C and the projection lens side dichroic prism 341D from which the combined light is emitted are close to each other and formed in a square shape in plan view. These red light side dichroic prisms 341A and the like are referred to as BK7 and are formed of borosilicate crown optical glass having a d-line refractive index of 1.51633.

  Further, such a cross dichroic prism 34 is a combination of the first prism pair 345A in which the red light side dichroic prism 341A and the projection lens side dichroic prism 341D are combined, and the blue light side dichroic prism 341B and the green light side dichroic prism 341C. It is formed by bonding the second prism pair 345B. A detailed manufacturing method of the cross dichroic prism 34 will be described later.

  As shown in FIG. 3, these dichroic prisms 341 are provided with an incident / exit surface 342 </ b> A through which light from the optical conversion plate 33 enters or exits the projection lens 5.

  Further, the surface of the first prism pair 345A facing the red light dichroic prism 341A of the projection lens side dichroic prism 341D and the surface of the second prism pair 345B facing the green light side dichroic prism 341C of the blue light side dichroic prism 341B. On the surface, a reflective film forming surface 342B on which the wavelength selective reflective film 343 is provided is provided. A blue light reflecting film 343A that reflects only blue light and transmits light of other wavelengths is formed on the surface of the reflecting film forming surface 342B. Further, the blue light reflecting film 343A is formed so as to be arranged in a state of being divided into two on the same plane when the first and second prism pairs 345A and 345B are attached to form the cross dichroic prism 34. ing.

Here, the blue light reflection film 343A is also referred to as a dielectric multilayer film, and a silicon oxide (SiO ₂ ) thin film and a tantalum oxide (Ta ₂ O ₅ ) thin film are alternately formed from the side in contact with the reflection film forming surface 342B. A total of 25 layers are stacked to form a thickness of about several tens of μm. That is, the blue light reflecting film 343A is formed in a state of reflecting blue light by alternately laminating a thin film having a low refractive index and a thin film having a high refractive index at an appropriate thickness. Note that magnesium fluoride (MgF ₂ ) may be used instead of silicon oxide as the low refractive index material. Further, as a high refractive index material, titanium oxide (TiO ₂ ) or niobium oxide (Nb ₂ O ₅ ) may be used instead of tantalum oxide.

  An adhesive surface 342C is formed on the surface of the red light side dichroic prism 341A and the green light side dichroic prism 341C that faces the reflective film forming surface 342B. An adhesive is injected between the adhesive surface 342C and the blue light reflecting film 343A to form an adhesive layer 344.

  Further, on the surface of the blue light side dichroic prism 341B and the green light side dichroic prism 341C facing the first prism pair 345A, a reflection film forming surface 342D on which the wavelength selective reflection film 343 is provided is provided. On the surface of the reflection film forming surface 342D, a red light reflection film 343B that reflects only red light having a wavelength of, for example, 850 nm and transmits light of other wavelengths is formed. The red light reflection film 343B is formed so as to be disposed as one continuous film on the same plane when the first and second prism pairs 345A and 345B are attached to form the cross dichroic prism 34. That is, the red light reflecting film 343B and the blue light reflecting film 343A are formed so as to intersect in a substantially X shape along the side surfaces of the four dichroic prisms 341. Further, the red light reflecting film 343B is continuously formed without being divided at the substantially X-shaped intersection position.

Here, the red light reflecting film 343B is formed to have a thickness of about several tens of μm by alternately stacking 29 layers of silicon oxide thin films and tantalum oxide thin films alternately from the side where the reflecting film forming surface 342D contacts. Yes. Specifically, the red light reflecting film 343B includes a gas barrier layer 343B1 provided as a first layer in contact with the reflecting film forming surface 342D. The gas barrier layer 343B1 is formed of silicon oxide as a metal oxide that transmits SiO _x and visible light represented by a general formula of 0.8 ≦ x ≦ 1.7. Further, on the surface of the gas barrier layer 343B1, a multilayer film 343B2 formed by alternately stacking a total of 28 tantalum oxide thin films and silicon oxide thin films is provided.

  A flat joint surface 342E is formed on the surface of the red light side dichroic prism 341A and the projection lens side dichroic prism 341D that faces the second prism pair 345B. Further, an adhesive layer 344 made of an adhesive is also formed between the joint surface 342E and the red light reflecting film 343B.

  In FIG. 3, the wavelength-selective reflecting film 343 and the adhesive layer 344 are shown with large thickness dimensions for easy understanding of the description, but in actuality, the thickness dimension is several tens of μm on the surface of the dichroic prism 341. Thus, it is formed in a film shape and is formed in a minute dimension with respect to the size of the dichroic prism 341.

  With the above configuration, the cross dichroic prism 34 reflects the red light incident on the red light side dichroic prism 341A to the projection lens side dichroic prism 341D by the red light reflecting film 343B, and the blue light incident on the blue light side dichroic prism 341B. Is reflected to the projection lens side by the blue light reflecting film 343A, and the green light incident from the green light side dichroic prism 341C is transmitted as it is to the projection lens side dichroic prism, and the respective color lights are combined to form a color image and projected. The light exits from the incident / exit surface 342A of the lens side dichroic prism 341D.

[Method of manufacturing cross dichroic prism]
Next, a method for manufacturing the cross dichroic prism 34 as described above will be described with reference to FIGS. 4A and 4B are diagrams showing a method of manufacturing a cross dichroic prism. FIG. 4A is a diagram showing a process of placing a blue light side dichroic prism and a green light side dichroic prism on a manufacturing jig, and FIG. The figure which shows the process of adhere | attaching the light side dichroic prism and the green light side dichroic prism, (C) is a figure which shows the process of forming a gas barrier layer in a 2nd prism pair, (D) is a multilayer film part in a 2nd prism pair. The figure which shows the process to form, (E) is a figure which shows the process of combining the 1st and 2nd prism pair, and adhere | attaching. FIG. 5 is a perspective view showing a cross dichroic prism formed by bonding and fixing the first and second prism pairs. In FIG. 4, the thickness dimensions of the wavelength-selective reflective film 343 and the adhesive layer 344 are exaggerated and displayed larger than the actual thickness in order to make the explanation easy to understand.

  In order to manufacture the cross dichroic prism 34, first, four dichroic prisms 341 are manufactured. That is, for example, a dichroic prism 341 having a triangular prism having an isosceles right section is manufactured by cutting and polishing a borosilicate crown optical glass called BK7.

  Next, of the dichroic prism 341 manufactured in this way, a vacuum deposition method, an ion assist deposition method, an ion plating method, a sputtering method, etc. are applied to the surface of the reflective film forming surface 342B of the blue light side dichroic prism 341B. The blue light reflecting film 343A is formed by using this. Further, the blue light reflecting film 343A is also formed on the surface of the reflecting film forming surface 342B of the projection lens side dichroic prism 341D.

Thereafter, as shown in FIG. 4A, the blue light side dichroic prism 341B and the green light side dichroic prism 341C are placed in a state where the blue light reflecting film 343A and the bonding surface 342C face each other, for example, of a manufacturing jig (not shown). Place on the mounting surface. Then, an adhesive is injected between the blue light reflecting film 343A and the adhesive surface 342C, and pressed in a direction in which the blue light side dichroic prism 341B and the green light side dichroic prism 341C are brought close to each other. As the adhesive, an adhesive having good translucency, glass adhesion, and precision, for example, trade name UT20 (manufactured by Adel Co., Ltd.) is used. As a result, the adhesive can be uniformly filled between the blue light reflecting film 343A and the adhesive surface 342C, and the substantially thin adhesive layer 344 is formed. Then, as shown in FIG. 4B, the adhesive is solidified to form the second prism pair 345B.
Here, although not shown, the red light side dichroic prism 341A and the projection lens side dichroic prism 341D are similarly bonded to form the first prism pair 345A.

Then, as shown in FIG. 4C, the surface of the reflective film forming surface 342D of the second prism pair 345B is made of SiO _x and 0.8 ≦ x ≦ 1. 7 is formed. The silicon oxide gas barrier layer 343B1 represented by the general formula 7 is formed. Here, the film formation of the gas barrier layer 343B1 is performed in a chamber having a low temperature of, for example, 150 ° C. or less and an atmosphere having an extremely low oxygen concentration. Thereby, it can prevent that the contact bonding layer 344 deteriorates and changes in quality.
Thereafter, as shown in FIG. 4D, a multilayer film 343B2 is formed on the surface of the gas barrier layer 343B1 by using an ion-assisted deposition method. Thereby, the red light reflecting film 343B is formed on the second prism pair 345B.
Here, the film formation of the gas barrier layer 343B1 and the multilayer film 343B2 may be performed continuously with the same apparatus, or may be performed discontinuously with different apparatuses.

Thereafter, the first and second prism pairs 345A and 345B are combined, and as shown in FIG. 4E, the red light reflection film 343B formed on the second prism pair 345B and the first prism pair 345A are joined. An adhesive is injected between the surface 342E and an adhesive layer 344 is formed to bond and fix these first and second prism pairs 345A and 345B. For this purpose, for example, holding members (not shown) are inserted at positions where the adhesive layer 344 is formed at both end positions 346 (see FIG. 5) of the first and second prism pairs 345A and 345B, and the first and second prisms are formed. The positions of the pairs 345A and 345B are determined, and an adhesive is injected to form the adhesive layer 344. As a result, a columnar cross dichroic prism 347 as shown in FIG. 5 is formed. Thereafter, the columnar cross dichroic prism 347 is cut into a size (indicated by a broken line in FIG. 5) that can be attached to the optical device 3.
Thus, the cross dichroic prism 34 of the present embodiment is manufactured.

[Effects of Embodiment]
In the projector 1 of the present embodiment as described above, a plurality of cross dichroic prisms 34 are crossed in a substantially X shape along the side surfaces of the four dichroic prisms 341 bonded to each other side surface by an adhesive. A blue light reflection film 343A and a red light reflection film 343B made of layers are formed. Further, the red light reflection film 343B is continuously formed without being divided at the substantially X-shaped intersection position. The red light reflecting film 343B is provided with a gas barrier layer 343B1 formed as a first layer in contact with the reflecting film forming surface 342D.
Therefore, after bonding the blue light side dichroic prism 341B and the green light side dichroic prism 341C with an adhesive, the gas barrier layer 343B1 is formed and then the multilayer film 343B2 is formed, and the adhesive layer 344 deposits the multilayer film 343B2. You will not be exposed to the atmosphere. Therefore, it is possible to suppress deterioration and deterioration of the adhesive layer 344 of the cross dichroic prism 34. Therefore, the cross dichroic prism 34 can display a good image without adversely affecting the image quality.
Further, the optical device 3 and the projector 1 in which such a cross dichroic prism 34 is built can project a good image.

The gas barrier layer 343B1 provided as the first layer is formed of a metal oxide that transmits visible light.
Therefore, the gas barrier layer 343B1 can be easily formed by a vapor deposition method or a sputtering method.

Further, the gas barrier layer 343B1 is formed of silicon oxide represented by a general formula of SiO _x and 0.8 ≦ x ≦ 1.7.
For this reason, the oxygen permeability can be lowered as compared with the configuration in which the gas barrier layer 343B1 is formed of, for example, silicon oxide having a value x greater than 1.7. Therefore, deterioration and deterioration of the adhesive layer 344 can be further suppressed.
In particular, when the multilayer film 343B2 is formed by an ion-assisted deposition method, the deposition is performed in an atmosphere of oxygen ions activated by plasma, but the general condition of SiO _x and 0.8 ≦ x ≦ 1.7 By applying the silicon oxide represented by the formula, deterioration and alteration of the adhesive layer due to oxygen ions can be suppressed. Therefore, by forming the dense multilayer film 343B2 on the gas barrier layer 343B1, the optical characteristics can be stabilized, and a better image can be displayed.
Further, since the low temperature deposition can be performed, the adhesive can be easily selected even if there is a restriction that the refractive index of the adhesive is the same as that of the borosilicate crown optical glass of the base material of the dichroic prism 341.

[Other Embodiments]
The present invention is not limited to the above-described embodiment, but includes modifications and improvements as long as the object of the present invention can be achieved.

For example, the gas barrier layer 343B1 may be formed using aluminum oxide (Al ₂ O ₃ ).
Even in such a configuration, the oxygen permeability can be lowered and deterioration and deterioration of the adhesive layer 344 can be further suppressed as compared with the configuration in which the gas barrier layer 343B1 is formed of silicon oxide, as in the above embodiment. Can do.

Further, although the configuration using the ion-assisted vapor deposition method that can form a dense multilayer film even at a temperature of 200 ° C. or lower is illustrated, a configuration using normal vapor deposition that does not use ion assist may be used.
When such normal vapor deposition is used, a temperature of about 300 ° C. must be set in order to form a dense multilayer film similar to the case of using the ion-assisted vapor deposition method, but the adhesive layer 344 forms the multilayer film 343B2 as a multilayer film. It is not exposed to the atmosphere for vapor deposition, and deterioration and deterioration of the adhesive layer 344 of the cross dichroic prism 34 can be suppressed.

  Furthermore, although the configuration in which the gas barrier layer 343B1 is provided as the first layer of the red light reflecting film 343B is illustrated, a configuration in which a gas barrier layer is provided as the first layer of the blue light reflecting film 343A may be employed. Further, a gas barrier layer may be provided as the first layer of the green light reflecting film that reflects green light.

  Although the best configuration for carrying out the present invention has been disclosed in the above description, the present invention is not limited to this. That is, the invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of materials, quantity, and other detailed configurations.

  Therefore, the description limited to the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such is included in this invention.

  Next, the effect of this invention is demonstrated based on a specific Example.

[Relationship between gas barrier layer and oxygen permeability]
First, the relationship between the gas barrier layer and the oxygen permeability will be described.
Samples of Examples 1 to 3 and Comparative Examples 1 to 4 were formed on a PET (polyethylene terephthalate) sheet by forming a gas barrier layer having a material and thickness as shown in Table 1 below. And the oxygen amount per 1 m < ² > permeate | transmitted with these samples on the 1st was measured as oxygen permeability.
Here, a PET film having a thickness of 12 μm was used.
The oxygen permeability was measured using an oxygen gas permeability measuring device OXTRON (manufactured by MOCON).
Furthermore, the element concentration in the gas barrier layer was measured by the XPS method using an X-ray photoelectron spectrometer SSX-100 type (manufactured by Silicon Systems).
In the following description, for example, a silicon oxide represented by SiO _0.8 is referred to as a silicon oxide having x of 0.8.

As shown in Table 1, it was confirmed that the samples of Examples 1 to 3 had an oxygen permeability smaller than 10 cc / m ² / day. Moreover, it was confirmed that the samples of Comparative Examples 1 to 4 are larger than 10 cc / m ² / day.
That is, when the gas barrier layer is formed of a silicon oxide having x of 0.8 and 1.7 and when formed of aluminum oxide, it is confirmed that the oxygen permeability is smaller than 10 cc / m ² / day. It was.
It is also confirmed that the gas barrier layer is larger than 10 cc / m ² / day when x is made of silicon oxide less than 0.8 or larger than 1.7 and when no gas barrier layer is provided. It was done.
From these, it was confirmed that the oxygen permeability can be further lowered by the configuration of the present invention.

[Relationship between gas barrier layer and light transmittance]
Next, the relationship between the gas barrier layer and the light transmittance will be described.
FIG. 6 is a graph showing the relationship between the gas barrier layer and the light transmittance.
An adhesive (trade name: UT20, manufactured by Adel) was applied to quartz glass. Further, a red light reflecting film having a gas barrier layer and a multilayer film as shown in Table 2 below was formed thereon, and samples of Examples 11 to 13 and Comparative Examples 11 and 12 were generated.
Then, light was incident perpendicularly on these samples, and the light transmittance was measured.

As shown in FIG. 6, the samples of Examples 11 to 13 and Comparative Example 11 were confirmed to have higher transmittance than the sample of Comparative Example 12.
Thereby, it was confirmed that even if the configuration of the present invention is applied, the light transmittance is not lowered.

[Relationship between the gas barrier layer provided on the red light reflecting film and the reflectance of red light]
Next, the relationship between the gas barrier layer provided on the red light reflecting film and the reflectance of red light will be described.
Samples of Examples 21 to 24 and Comparative Examples 21 to 24 were prepared by applying an adhesive to quartz glass and forming a red light reflecting film having a gas barrier layer and a multilayer film as shown in Table 3 below. Was generated.
Then, light was incident on these samples at an incident angle of 45 degrees, and the light transmittance was measured.

  Here, in Table 3, the optical film thickness is a value when λ / 4 = 1.0 and λ = 850 nm. The material of the second layer is tantalum oxide. Further, in the third and subsequent layers, silicon oxide and tantalum oxide are alternately formed.

Although not shown here, it was confirmed that the transmittance of red light having a wavelength of 850 nm was about 0% in any of the samples of Examples 21 to 24 and Comparative Examples 21 to 24. That is, it was confirmed that the reflectance of red light was about 100%.
Thus, it was confirmed that even when the configuration of the present invention is applied to the red light reflecting film, the red light reflectance is not lowered.

[Relationship between gas barrier layer provided on blue light reflection film and blue light reflectance]
Next, the relationship between the gas barrier layer provided on the blue light reflecting film and the reflectance of blue light will be described.
Similarly to the sample of Example 21, a blue light reflecting film having a gas barrier layer and a multilayer film as shown in Table 4 below was formed, and samples of Examples 31 to 34 and Comparative Examples 31 to 34 were generated. .
Then, light was incident on these samples at an incident angle of 45 degrees, and the light transmittance was measured.

  Here, in Table 4, the optical film thickness is a value when λ / 4 = 1.0 and λ = 525 nm. The second and subsequent layers have the same configuration as the sample of Example 21.

Although not shown here, it was confirmed that the transmittance of blue light was about 0% in any of the samples of Examples 31 to 34 and Comparative Examples 31 to 34. That is, it was confirmed that the reflectance of blue light was about 100%.
Thus, it was confirmed that even when the configuration of the present invention is applied to the blue light reflecting film, the blue light reflectance is not lowered.

  The present invention can be used for a cross dichroic prism of an optical device built in a projector.

It is a figure which shows typically the optical system provided in the inside of the projector which concerns on one Embodiment of this invention. It is a perspective view which shows typically the cross dichroic prism in the said one Embodiment. It is sectional drawing which shows typically the cross section in the optical axis surface of the cross dichroic prism in the said one Embodiment. It is a figure which shows the manufacturing method of the cross dichroic prism in the said one Embodiment, (A) is a figure which shows the process of mounting a blue light side dichroic prism and a green light side dichroic prism in a manufacturing jig, (B), The figure which shows the process of adhere | attaching a blue light side dichroic prism and the green light side dichroic prism, (C) is a figure which shows the process of forming a gas barrier layer in a 2nd prism pair, (D) is a multilayer film part in a 2nd prism pair (E) is a figure which shows the process of combining and adhere | attaching a 1st and 2nd prism pair. 2 is a perspective view showing a cross dichroic prism formed by bonding and fixing a first and second prism pair in the embodiment. FIG. It is a graph which shows the relationship between the gas barrier layer in the Example of this invention, and the light transmittance.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Projector, 3 ... Optical apparatus, 34 ... Cross dichroic prism, 341 ... Dichroic prism as a triangular prism, 343 ... Wavelength selective reflection film, 343B1 ... Gas barrier layer, 343B2 ... Multilayer film

Claims (7)

A cross dichroic prism having two types of wavelength-selective reflecting films that intersect in a substantially X shape and each have a plurality of layers,
Four triangular prisms joined to each other by an adhesive, and two wavelength-selective reflecting films formed so as to intersect in a substantially X shape along the side surfaces of the four triangular prisms One of the two wavelength-selective reflection films is continuously formed without being divided at the substantially X-shaped intersection position, and the triangular prism of the wavelength-selective reflection film formed continuously A cross dichroic prism, wherein the first layer in contact with the prism functions as a gas barrier layer. The cross dichroic prism according to claim 1,
The cross dichroic prism, wherein the first layer is formed of a metal oxide that transmits visible light. The cross dichroic prism according to claim 2,
The cross dichroic prism, wherein the metal oxide is a silicon oxide represented by a general formula of SiO _x and 0.8 ≦ x ≦ 1.7. The cross dichroic prism according to claim 2,
The cross dichroic prism, wherein the metal oxide is aluminum oxide.   5. The cross dichroic prism according to claim 1, a liquid crystal panel arranged close to each of three surfaces among four surfaces positioned outside the cross dichroic prism, and the cross dichroic prism An optical device comprising: a projection lens disposed opposite to the four surfaces other than the three surfaces.   A projector comprising the optical device according to claim 5. A method of manufacturing the cross dichroic prism according to any one of claims 1 to 4,
A method of manufacturing a cross dichroic prism, comprising: forming a multilayer film formed on the first layer by vapor deposition accompanied with ion assist.

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