JP2007256421A - Reflector mirror, its manufacturing method, and image display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aspherical reflector mirror which is excellent in shape precision and can be manufactured by overcoming problems in mirror finishing, and also to provide its manufacturing method and an image display using this reflector mirror. <P>SOLUTION: This reflector mirror 1 has a base 2 having an aspherical surface 21 obtained through cutting or grinding and having asperities exceeding 5nm in a mean average roughness Ra, a film 3 coated on this aspherical surface 21, and a reflector film 4 formed on this coated film 3. This method forms a reflector film 4 on the coated film 3 without mirror polishing the base 2 having an aspherical surface 21 with asperities exceeding 5nm in a mean average roughness Ra. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an aspherical reflector suitably used for reflecting projection light of an image display device such as a rear projection television, a manufacturing method thereof, and an image display device using the reflector.

A rear projection television projects light modulated according to an image signal from an image engine unit by a projection optical system, and projects the projected light onto a screen by reflection of one or a plurality of reflecting mirrors. To display. In a rear projection television aimed at reducing the thickness, an axially symmetric aspherical reflecting mirror that widens the angle of the projected light and reflects it upward may be used as the reflecting mirror that reflects the projected light.

As a method of manufacturing such an axisymmetric aspherical reflecting mirror, there is a method of providing a reflecting film on a mirror-shaped resin base material formed by injection molding. In addition, there is a method of providing a reflective film after further mirror-polishing a metal base material cut into a mirror-like shape by cutting or grinding from a metal material.

There are the following prior arts for aspherical mirror polishing.
JP-A-7-1000075 Japanese Patent Laid-Open No. 2002-200548 JP 2004-351574 A

However, the accuracy of a resin molded product obtained by injection molding is insufficient for a reflector used in a rear projection television. In addition, the machining accuracy of the aspherical surface can be easily obtained by machining, but since the machining trace remains on the surface obtained by machining and the surface roughness is too rough for the mirror surface, the surface roughness required for the mirror surface is required. It is necessary to perform mirror polishing so that

Aspherical mirror polishing is very difficult. For example, the aspherical mold polishing method of Patent Document 1 described above has the following problems. (1) When polishing an inclined surface such as an aspherical shape, it is necessary to feed back a load applied perpendicularly to the surface, and therefore it is necessary to use an expensive processing machine with a B-axis or the like. (2) The distribution of the polishing amount by the polisher changes with changes in processing conditions, that is, changes in processing points. Since the distribution of the polishing amount also changes depending on the shape error shape of the pre-processing, it is necessary to take into account changes in the polishing amount due to changes in these conditions in advance in order to perform correction processing. (3) It takes considerable time to improve the shape accuracy by polishing. (4) In the polishing process, there is often a certain tendency such as an increase in the polishing amount of the outer peripheral portion. For this reason, the processing shape by cutting / grinding processing is taken into consideration in advance for the shape error that would occur due to the polishing process. It is necessary to correct from the design shape. (5) If the material of the base material is changed, all processing conditions must be reviewed.

In the polishing method of Patent Document 2, in addition to the problems of Patent Document 1, since the amount of processing in polishing is extremely small, there is a problem in that it has to be processed into a mirror surface without cracks in the pre-processed state. is there.

In addition to the problems (4) and (5) described above, the precision polishing tool and the precision polishing method of Patent Document 3 have a problem that the shape accuracy deteriorates when the surface roughness is improved by polishing. .

The present invention has been made in view of the above circumstances, and an object thereof is to provide an aspherical reflecting mirror that has good shape accuracy and can overcome the problems of mirror polishing.
Moreover, an object of this invention is to provide the manufacturing method of this reflecting mirror.
Furthermore, an object of the present invention is to provide an image display device using such a reflecting mirror.

In order to achieve the above object, according to the present invention, firstly, a base material having an aspherical surface with an arithmetic average roughness Ra of 5 to 500 nm obtained by cutting or grinding, and the aspherical shape Provided is a reflecting mirror comprising a coating film provided on a surface and a reflective film provided on the coating film.

This reflecting mirror is a coating provided on the surface of the substrate without mirror polishing.
And has a structure in which a reflective film is provided on a smooth coating surface. Shape accuracy can be ensured by cutting or grinding. Therefore, by providing a coating film on the surface of the base material, the surface roughness required for the reflecting mirror can be easily obtained, a lot of polishing time is required, an expensive apparatus is required, and the shape accuracy deteriorates. Mirror polishing problems such as complicated settings can be overcome.

Secondly, the present invention provides a coating process for forming a coating on the aspherical surface of a substrate having an aspherical surface with an arithmetic average roughness Ra of 5 to 500 nm, and a reflective film on the coating And a reflecting film forming step for providing a reflecting mirror.

According to this method of manufacturing a reflecting mirror, a simple method of providing a coating film on the surface of a base material is used to fill and smooth the unevenness of the surface of the base material to obtain the surface roughness required for the reflecting mirror. Mirror polishing problems such as polishing time required, expensive equipment required, shape accuracy deteriorated, and complicated condition setting can be overcome. Shape accuracy can be ensured by processing the substrate.

Third, the present invention is characterized in that, in the method for producing the second reflecting mirror, the coating composition for forming the coating film has a viscosity at 25 ° C. in the range of 3.5 to 0.3 cP. A method of manufacturing a reflector is provided.

In order to fill and smooth the unevenness of the substrate surface with the coating film, the viscosity of the coating composition forming the coating film is important. If the viscosity is too high, it becomes difficult to smooth the coating film itself, If the viscosity is too low, it becomes difficult to fill and smooth the unevenness of the substrate surface.

Fourthly, in the second reflecting mirror manufacturing method of the present invention, the coating composition for forming the coating film has a general formula: RSiX ₃ (wherein R is a carbon number having a polymerizable reactive group). Represents an organic group of 2 or more, and X represents a hydrolyzable functional group).

This organosilicon compound is excellent in adhesion to the substrate surface and a reflective film provided on the coating film as a film-forming material, and is suitable for filling and smoothing the unevenness of the substrate surface.

Fifthly, the present invention provides an image display device characterized in that the first reflecting mirror is used as a reflecting mirror for widening the angle of projection light.

Since the reflecting mirror is a high-performance aspherical reflecting mirror with good shape accuracy and surface smoothness, an image display device using the reflecting mirror for reflection for widening the angle of projection light is thin. And image quality can be improved.

Hereinafter, although the reflector of the present invention, its manufacturing method, and an embodiment of an image display device are explained, the present invention is not limited to the following embodiments.

1A to 1C show a flowchart of the manufacturing process of the reflecting mirror of the present invention. FIG.
A substrate 2 shown in FIG. 1A for manufacturing the reflecting mirror 1 shown in FIG. 1 is made of metal, plastic, ceramic, etc. formed into an aspherical shape such as an axisymmetric aspherical surface by cutting or grinding. It is. Cutting is a processing method that cuts a workpiece into a predetermined shape using a blade as a tool, and grinding is a processing method that uses a grindstone as a tool to cut the surface of the workpiece into a predetermined shape. is there. The axisymmetric aspheric shape can be formed by controlling the relative distance of the workpiece or tool in the axial direction while moving the tool at a predetermined feed pitch in the radial direction of the workpiece while rotating the workpiece. .

The arithmetic average roughness Ra of the surface obtained by cutting or grinding is about 20 n with a medium finish.
m. The arithmetic average roughness Ra of the surface required for the reflector is less than 5 nm. It is not impossible to obtain a mirror-finished surface having an arithmetic average roughness Ra of less than 5 nm by cutting or grinding, but the processing time becomes extremely long and is not practical. The arithmetic average roughness Ra obtained by cutting or grinding is usually in the range of 5 nm to several μm, but the arithmetic average roughness Ra that can be covered with the coating film is about 5 nm to 500 nm. On the aspherical surface 21 that has been cut or ground, wavy irregularities with a feed pitch are formed as processing marks.

In the manufacturing process of the reflecting mirror of the present invention, as shown in FIG. 1 (b), a coating process is provided in which the coating film 3 is provided on the aspherical surface 21 of the substrate 2. The unevenness of the surface 21 is coated, the surface of the coating film 3 is newly provided on the surface of the base material 2, and the surface roughness required as a reflecting mirror is obtained by utilizing the smoothness of the surface of the coating film 3.

The coating composition for forming the coating film 3 can be smoothed by filling the unevenness of the machined surface 21 of the substrate 2, having good adhesion to the surface of the substrate 2, and provided on the coating film 3. It is required that the adhesiveness with the reflection film 4 to be obtained is good and that the thermal expansion coefficient is close to those of the base material 2 and the reflection film 4.

As a film forming component of such a coating composition, the general formula: RSiX ₃ (wherein R represents an organic group having 2 or more carbon atoms having a polymerizable reactive group, and X represents a hydrolyzable functional group. An organosilicon compound represented by the formula (1) can be preferably used. Examples of the organic group having an R polymerizable reactive group of the organosilicon compound include a vinyl group, an allyl group, an acrylic group, a methacryl group, an epoxy group, a mercapto group, a cyano group, an isocyano group, and an amino group. be able to. Specific examples of the hydrolyzable functional group of X include alkoxy groups such as methoxy group, ethoxy group, and methoxyethoxy group, halogen groups such as chloro group and bromo group, and acyloxy groups.

Specific examples of the organosilicon compound include, for example, vinyl trialkoxysilane, vinyltrichlorosilane, vinyltri (β-methoxy-ethoxy) silane, allyltrialkoxysilane, acryloxypropyltrialkoxysilane, methacryloxypropyltrialkoxysilane, methacryl Oxypropyl dialkoxymethylsilane, γ-glycidoxypropyltrialkoxysilane, β- (3,4-epoxycyclohexyl) -ethyltrialkoxysilane, mercaptopropyltrialkoxysilane, γ-aminopropyltrialkoxysilane, N-β (Aminoethyl) -γ-aminopropylmethyl dialkoxysilane and the like.

The amount of the organosilicon compound used is 10 to 70% by weight, particularly 20 to 10% by weight of the solid content in the coating composition.
The range of 60% by weight is desirable. If the blending amount is too small, the adhesion with the reflective film tends to be insufficient. On the other hand, when there are too many compounding quantities, the coating film 3 will be cracked and the smoothness required for a reflective mirror may not be maintained.

Moreover, in order to make the thermal expansion coefficient of the coating film 3 close to the reflective film 4 and to improve the adhesion with the reflective film 4, it is preferable to blend inorganic oxide fine particles having an average particle diameter of 1 to 200 nm. Such inorganic oxide fine particles include Si, Al, Sn, Sb, Ta, Ce, La, Fe, and Zn.
, W, Zr, In, Ti, one or more kinds of oxide fine particles or composite fine particles selected from metals. _{Specifically, SiO 2, SnO 2, Sb} 2 O 5, CeO 2
, ZrO ₂ , TiO _{2 and} other inorganic oxide fine particles dispersed in a dispersion medium such as water, alcohols or other organic solvents in a colloidal form, or Si, A1, Sn, Sb,
Exemplified colloidal dispersion of composite fine particles composed of two or more inorganic oxides of Ta, Ce, La, Fe, Zn, W, Zr, In, Ti in water, alcohol or other organic solvents can do.

The blending amount of the inorganic oxide fine particles is 5 to 80% by weight, particularly 10 to 5% by weight of the solid content in the coating composition.
The range of 0% by weight is desirable. When there are too few compounding quantities, adhesiveness with a reflective film may become inadequate. Moreover, when there are too many compounding quantities, a crack will arise in the coating film 3, and the smoothness required for a reflective mirror may be unable to be maintained.

The viscosity of the coating composition is an important factor because it affects the smoothness of the resulting coating film 3. In order to fill and smooth the unevenness of the surface 21 of the substrate 2 with the coating film 3, the viscosity of the coating composition at 25 ° C. is preferably in the range of 3.5 to 0.3 cP. If the viscosity is too high, it is difficult to smooth the coating film 3 itself. On the other hand, if the viscosity is too low, it may be difficult to fill the unevenness on the surface of the substrate 2 and smooth it.

Further, the surface tension of the coating composition is preferably as low as possible, specifically, it is preferably lower than the surface tension of water at 25 ° C. of 72 nm / m. When surface tension is higher than this, wettability with a base material will deteriorate and there exists a possibility that the smoothness of a coating film may be impaired. In order to reduce the surface tension of the coating composition, it is preferable to add a surfactant called a leveling agent.

The method for coating the substrate 2 with the coating composition is not limited as long as a uniform coating film can be formed in an axially symmetric aspherical shape, and examples thereof include a dipping method and a spin coating method. After the coating composition is applied to the substrate 2, drying and curing are performed to form the coating film 3.

The film thickness of the coating film 3 is not limited as long as it can cover the unevenness of the surface 21 of the substrate 2, but is in the range of about 0.05 to 30 μm, preferably 0.5 to 10 μm. When the film thickness of the coating film is too thin, it becomes difficult to fill and smooth the unevenness on the surface of the base material, while when the film thickness is too thick, the smoothness of the coating film may be impaired.

In the mirror polishing process, polishing is performed up to the maximum depth of unevenness on the substrate surface. For this reason, the surface of the coating film on which the reflective film is provided differs from the surface of the substrate on which the reflective film is provided in the case of mirror polishing by the thickness of the coating film. Therefore, there is no optical influence.

Next, as shown in FIG. 1 (c), a thin film having a high reflectance such as silver, gold, aluminum, nickel / chromium, nickel / gold, rhodium, etc. A reflective film forming process is performed in which the reflective film 4 is formed by a method such as physical vapor deposition such as sputtering, liquid coating, or wet plating.
(Example)

The Example of the manufacturing method of a reflective mirror is shown. Single-crystal diamond tool with a tip radius of 1 mm (product name “Single-crystal diamond cutting tool New Debite” manufactured by Allied Material Co., Ltd.)
The aluminum alloy (A5056) is cut while spraying oil mist using a fly cut tool attached to the outer periphery of a disk having an outer diameter of 60 mm. The machining conditions are a workpiece feed pitch of 10 μm in the circumferential direction and a feed pitch of 50 μm in the radial direction, and the surface roughness at this time is 20 μm.
nmRa.

The method for forming the coating composition is as follows. Butyl cellosolve 68g, methanol 1
39 g and 61 g of γ-glycidoxypropyltrimethoxysilane were mixed. To this mixture, 17 g of a 0.1N hydrochloric acid aqueous solution was added dropwise with stirring. After further stirring for 3 hours, the mixture was aged overnight. Methanol-dispersed SiO ₂ fine particle sol (made by Catalyst Chemical Industry Co.,
181 g of trade name “Oscar 1132” (solid content concentration 30%), diglycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name “Denacol EX-421”) 26
g Magnesium perchlorate 3g, Silicone surfactant (Nippon Unicar Co., Ltd., trade name "L-7001") 0.15g, Silicone surfactant (Nihon Unicar Co., Ltd., trade name "L-7604" ) 0.05 g, phenolic antioxidant (manufactured by Kawaguchi Chemical Co., Ltd.,
0.6 g of a product name “ANTAGE CRYSTAL”) and 3.7 g of a benzotriazole ultraviolet absorber (product name “TINUVIN 213” manufactured by Ciba Specialty Chemicals Co., Ltd.) were added, stirred for 4 hours, and then aged for a whole day and night. did. The viscosity of this coating composition at 25 ° C. was 2.0 cP.

This coating composition was applied on a substrate made of aluminum alloy after turning by a dipping method (pulling speed 35 cm / min). The coated substrate was heat-cured at 125 ° C. for 3 hours to form a 2.5 μm-thick coating film on the substrate.

A reflective film was formed on the base material on which the coating film was formed by vacuum deposition. Arithmetic mean roughness R of this mirror
When a was measured with a non-contact type roughness meter, it was less than 5 nm. Further, when the shape accuracy was measured with a three-dimensional measuring instrument, it was within an allowable error.

In the thus obtained reflector 1 of the present invention, the uneven surface 21 having an axisymmetric aspherical shape with an arithmetic average roughness Ra exceeding 5 nm obtained by cutting or grinding the base material 2 has a smooth surface. It has a structure in which the reflective film 4 is provided on the smooth surface of the coating film 3 that is covered with the coating film 3.

The reflecting mirror 1 of the present invention can maintain the surface roughness of the intermediate finish level that can be easily obtained by cutting or grinding, so that the creation of the axisymmetric aspherical shape of the substrate can be easily achieved, and it is a very difficult axisymmetric aspherical surface. There is no need to mirror the shape.

Therefore, it is possible to overcome the problems of mirror polishing such as requiring a lot of polishing time, requiring an expensive apparatus, deteriorating shape accuracy, and complicated setting of conditions. Since the shape accuracy of the aspherical shape is obtained by cutting or grinding, the shape accuracy necessary for the mirror surface is good. Moreover,
The substrate 2 can be protected from scratches caused by the coating film 3 being assembled. Even if the coating film 3 is damaged, it can be repaired by peeling off the coating film 3 and reattaching the film.

Next, an embodiment of an image display device using the reflecting mirror of the present invention will be described with reference to FIG. The image display device 10 is a thin rear projection television. A transmissive screen 12 occupying most of the front area is disposed in front of the thin casing 11, and an image is displayed on the screen 12. The light modulated in accordance with the image signal from the image engine unit 14 accommodated in the support frame 13 disposed on the back side of the lower screen 12 in the housing 11 is substantially vertically upward by the projection optical system 15. The first mirror 1 of the plane mirror is projected.
6 is reflected to the rear second mirror 17, and the second mirror 17 having an axisymmetric aspherical mirror surface widens the reflected light and reflects it to the ceiling surface side of the housing 11. The projection light from the second mirror 17 is reflected by the third mirror 18, the projection light is projected on the entire back surface of the screen 12, and an image is displayed by the light transmitted through the screen 12.

The reflecting mirror of the present invention is used as the second mirror 17 of the image display device 10. The second mirror 17 has a function of reflecting and widening the angle of the projected light, and is an important part for accurately traveling the light, and requires a precise axisymmetric aspherical shape. The reflecting mirror of the present invention is suitable for such applications. The reflecting mirror of the present invention can be used, for example, in an optical head of a scanner that reads a document. The optical head of the scanner can be used as a reflecting mirror that reflects and guides light from a light source reflected from a document to an optical system that projects the reduced light onto a solid-state imaging device.

The reflecting mirror of the present invention can be used as a reflecting mirror for widening the angle of projection light arranged in, for example, a rear projection television.
The manufacturing method of the reflecting mirror of this invention can be utilized in the field | area which manufactures this reflecting mirror.
The image display device of the present invention can be used as a rear projection television.

(A)-(c) is sectional drawing which shows the manufacturing process of the reflective mirror of this invention. It is a block diagram which shows an example of the image display apparatus using the reflective mirror of this invention.

Explanation of symbols

1: Reflecting mirror, 2: Base material, 21: Aspherical surface, 3: Coating film, 4: Reflecting film, 10: Image display device, 11: Housing, 12: Screen, 13: Support frame, 14: Image Engine unit, 15: projection optical system, 16: first mirror, 17: second mirror, 18: third mirror

Claims (5)

A base material having an aspherical surface with an arithmetic average roughness Ra of 5 to 500 nm obtained by cutting or grinding;
A coating film provided on the aspherical surface;
And a reflective film provided on the coating film. A coating step of providing a coating film on the aspherical surface of the substrate having an aspherical surface with an arithmetic average roughness Ra of 5 to 500 nm;
A reflective film forming step of providing a reflective film on the coating film. In the manufacturing method of the reflective mirror of Claim 2,
The method for producing a reflecting mirror, wherein the coating composition for forming the coating film has a viscosity at 25 ° C. in the range of 3.5 to 0.3 cP. In the manufacturing method of the reflective mirror of Claim 2,
The coating composition for forming the coating film has the general formula: RSiX ₃ (wherein R represents an organic group having 2 or more carbon atoms having a polymerizable reactive group, and X represents a hydrolyzable functional group. The manufacturing method of the reflective mirror characterized by including the organosilicon compound shown by this. An image display device, wherein the reflecting mirror according to claim 1 is used as a reflecting mirror for widening the angle of projection light.

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