JPH0735910A - Multilayered reflection interference film - Google Patents

Abstract

PURPOSE:To provide the multilayered reflection interference films which reflect light having specific wavelengths nearly uniformly over a wide range of a curved reflection surface. CONSTITUTION:The multilayered reflection interference films are provided with plural reflection interference films 24, 25, 26, 27 formed by alternately depositing dielectric materials varying refractive indices by evaporation on curved surfaces. The thicknesses of the respective reflection interference films are so set that the film thicknesses at any of the plural points E, F, G, H varying in vapor deposition speeds on the curved surfaces at any of these points are equaled to nearly 1/4 the wavelengths of the specified light. The spacings between the design wavelengths corresponding to the respective film thicknesses are so set as to be nearly equaled to the reflection wavelength band width having prescribed reflectivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer reflection interference film which is capable of almost uniformly reflecting light having a specific wavelength over a wide range of a curved reflecting surface and which can be easily formed.

[0002]

2. Description of the Related Art A discharge lamp in which a reflection interference film (hereinafter referred to as a reflection film) is formed on the outer surface of a discharge lamp, and light generated by plasma is reflected by the reflection film to enhance the intensity of irradiation light. Has been proposed (for details, refer to JP-A-53-25084).

As shown in FIG. 9, in this discharge lamp, a reflection film 2 made of a thin film of zirconium dioxide and a thin film of silica (neither is shown) is provided on the side opposite to the irradiation side of a cylindrical lamp body 1.
The thickness of each thin film is set to the wavelength of the light to be reflected, that is, about ¼ of the design wavelength.

[0004]

However, this discharge lamp has the following problems. (1) In order to form the reflection film 2 on the lamp body 1, the lamp body 1 is attached inside the vacuum container 3 as shown by a virtual line in FIG. The evaporation material 5 is made to fly upward from the located evaporation source 4 and vapor-deposited on the lower surface of the lamp body 1. According to this vacuum vapor deposition method, the vapor deposition rate in the radial direction at each portion of the lower surface of the lamp body is different. The thickness of the reflection film is thickest at the lowermost portion 6 of the lamp body, and gradually becomes thinner as the distance from the lowermost portion 6 increases.

(2) Therefore, when the film is formed with the film thickness in the lowermost portion 6 corresponding to the design wavelength, the lowermost portion 6 has a certain wavelength bandwidth a centered on the design wavelength as shown in FIG. Although the light is reflected, the wavelength of the reflected wave is gradually shortened in other portions, and the light of the wavelength to be reflected cannot be sufficiently strengthened.

In order to solve the above problems, there has been proposed a discharge lamp in which a reflecting film 2a having a constant thickness is formed on the side opposite to the irradiation side of the lamp body 1 as shown in FIG. According to the above, it is possible to reflect light having a desired wavelength over the entire surface of the reflective film 2a.

However, in order to form a reflection film having a constant thickness on the outer surface of the cylindrical lamp body 1, as shown in FIG. 12, the lamp body 1 is rotated about its axes 7, 7. However (see arrow b), it is necessary to perform vacuum vapor deposition, which complicates the work and equipment for vapor deposition, resulting in an increase in the manufacturing cost of the product. In the figure, 8 is a drive motor, 9 is a gear for rotation, 10 is a rack, and 11 is a mask for preventing vapor deposition.

Further, in order to reflect light having a specific wavelength over a wide range of the spherical reflecting surface, as shown in FIG. 13, a light shielding plate 13 formed in a fan (fan) shape below the sphere 12 is formed. Is arranged, and the vapor deposition material 5 is vapor-deposited on the lower surface 14 of the sphere while rotating the sphere 12 in the direction of arrow m. However, this method requires a high level of technology to set the contour line 15 of the shading board 13, and since trial and error is repeated many times, there is a problem that a large amount of time is spent preparing for the film forming work. .

In view of the above-mentioned problems, the present invention reflects light having a specific wavelength almost uniformly over a wide range of a curved reflecting surface without using a complicated vapor deposition equipment or a light shielding plate. An object is to provide a multilayer reflection interference film.

[0010]

In order to solve the above problems, the present invention has the following means. (Claim 1) A plurality of reflection interference films formed by alternately depositing dielectric materials having different refractive indexes on a curved surface are provided, and the thickness of each reflection interference film is one of a plurality of positions on the curved surface having different deposition rates. Is set so that the film thickness at that location is approximately equal to one-quarter of the specified wavelength of light, and the intervals between the design wavelengths corresponding to the respective film thicknesses are reflections having a predetermined reflectance. A multilayer reflection interference film, which is set to be substantially equal to the wavelength bandwidth. (Claim 2) The multilayer reflection interference film according to claim 1, wherein the specified wavelength of light is 365 nanometers.

[0011]

[Action]

(1) Since the plurality of reflection interference films reflect the light having the specific wavelength at different portions of the reflection surface, it is possible to uniformly reflect the light of the specific wavelength over a wide range of the reflection surface. (2) Since the reflectance of the reflected light by each reflection interference film is set to a predetermined value, the intensity of the reflected light can be strengthened together with the effect of the above (1).

(3) When depositing a thin film, since the object to be vapor-deposited does not rotate and a light-shielding board is not used as in the prior art, the film-forming work is easy. (4) When the specific wavelength is specified to be 365 nm, it becomes possible to provide a high-intensity ultraviolet lamp, which can greatly contribute to the progress of image forming and ultraviolet drying technology.

[0013]

EXAMPLES The basic principle of the case where the multilayer reflection interference film of the present invention is applied to the outside of a cylindrical curved surface will be first described, and then the examples will be described in detail. When vacuum deposition is performed on the lower surface of the cylindrical object in the same manner as described in paragraph No. 0004, a deposition material (not shown) is applied to the tangent line 22 passing through the lowermost point E of the object 21, as shown in FIG. The light enters vertically (arrow c) and a thin film 23 is formed on the lower surface of the object 21.

Assuming that the film thickness at point _E is T _E, and the film thickness (radial thickness) at point F on an arc separated by a central angle θ from this point E is T _F , this T _F is the radius. It is calculated by the formula (1) in consideration of the decrease of the vapor deposition rate in the direction. T _F = T _E × cos θ Equation (1)

Here, the wavelength of the light to be reflected is set to 3
When set to 65 nm, the film thickness at point E is 3
This is a quarter of 65 nanometers, or 91.25 nanometers. Now, assuming that θ = 60 degrees, the film thickness T F at the point _F becomes T _F = 91.25 × cos 60 degrees = 45.5 nanometers using the formula (1), and the design corresponding to this film thickness T _F The wavelength will be 182 nanometers. That is, the point F cannot reflect light of 365 nanometers.

Conversely, if the design wavelength at point F is set to 365 nanometers, the design wavelength at point E will be 730 nanometers and light of 365 nanometers cannot be reflected.

However, at three points E and F at the same time, 3
There is a method of reflecting light of 65 nanometers. That is, it is a method in which a thin film having a design wavelength of 365 nm at point E and a thin film having a design wavelength of 730 nm at point E are laminated in two layers.

Extending this idea, it is possible to uniformly reflect light of 365 nm at a plurality of points on the arc from point E to point F. That is, the range of the design wavelength from 365 nanometers to 730 nanometers is divided into a plurality of stages in the manner described below, and the reflection interference film having a film thickness corresponding to each wavelength of the divided design wavelengths. Is laminated in a plurality of layers.

Next, a method of dividing the design wavelength range will be described. As already described in paragraph number 0005, each point on the reflecting surface reflects light having a certain wavelength bandwidth. Therefore, by dividing the design wavelength range so that the wavelength bandwidths of the reflected waves are not separated from each other and do not overlap excessively, it is possible to minimize the types of reflective interference films, which is economical. Is. At this time, if the design wavelength range is divided by using a reflection wavelength bandwidth (hereinafter referred to as an effective reflection wavelength bandwidth) having a reflectance of 90% or more, the intensity of reflected light can be uniformly increased. it can.

Generally, the wavelength band width of the reflected wave increases with an increase in the number of layers of the thin film forming the reflection interference film, and when it reaches a certain value, it tends to hardly change even if the number of layers changes. The effective reflection wavelength bandwidth corresponding to the number of layers of each reflection interference film adopted in this embodiment is 50 to 100.
Since it is nanometer, it is designed wavelength range (365-73
(0 nanometer) is divided into four stages of 390, 475, 565, 680 nanometers.

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1, 2 and 4 to 8 show an embodiment of the present invention. The design wavelengths of the main parts of the multilayer reflection interference film 20 of this embodiment are 680, 565, 475, 39, respectively.
4 types of 0 nm reflection interference films 24, 25, 2
6, 27, which are laminated close to each other on the outer surface of a cylindrical tube body 28 made of quartz glass as shown in FIG. In FIG. 1, hatching showing the cross section of each reflection interference film is omitted for clarity.

More specifically, each reflection interference film (hereinafter referred to as a reflection film) 24, 25, 26, 27 is made of silicon dioxide (SiO ₂ , refractive index = 2.10) as shown in FIG.
Thin film 29 of zirconium dioxide and thin film 30 of zirconium dioxide (ZrO ₂ , refractive index = 1.47) are alternately laminated, and the number of layers of each reflective film 24, 25, 26, 27 is 16 layers, There are 17 layers, 12 layers, and 13 layers. Further, the thickness of the thin film at the lowermost portion E of the tubular body of each reflective film 24, 25, 26, 27 is one-fourth of each design wavelength described above, that is, 170.913, 141.25, 118.65, 97. ．
It is 462 nanometers.

In order to strengthen the bond between the reflective film 24 closest to the tube body 28 and the outer surface 33 of the tube body, as shown in FIG. 2, a thin film of silicon dioxide of the same material as the tube body 28. Three
0a is inserted. To form each thin film 29, 30, 30a, a sputtering method, a CVD method or the like may be used in addition to the vacuum deposition method shown in FIG. Tube 2 during film formation
Since No. 8 is in a stationary state, the film forming work is easy.

Next, the operation of this multilayer reflection interference film will be described. Now, as shown in FIG. 1, the central portion O of the pipe 28 is
A line light source 35 is arranged at the point E, and points E and G (center angle E when the light emitted by the line light source 35 is incident on the multilayer reflection interference film).
OG = 30 degrees), H point (center angle EOH = 45 degrees), and reflected light 36, 37 at point F (center angle EOF = 60 degrees).
The characteristics of Nos. 38 and 39 are shown in FIGS.
8 has a transmittance of 100%).

Observation of these figures reveals the following. (1) At the thick point E, the reflection films 24, 25, 26,
The reflected waves reflected from 27 are mutually strengthened or weakened to create reflected light having a large reflectance and a wide wavelength band. Then, this reflected light moves to the left in the drawing as the film thickness decreases, and the reflected wavelength bandwidth gradually narrows.

(2) The light having the wavelength of 365 nm specified above (see paragraph number 0015) is included in each of the reflected lights 36, 37, 38, 39 shown in FIGS. According to the reflection interference film, light of 365 nm is reflected with a reflectance close to 100% over a wide range of center angles from 0 to 60 degrees.

FIG. 8 shows the relationship between the change of the central angle and the film thickness of each reflective film, and the relationship between the change of the central angle and the change of the design wavelength of each reflective film. In order to facilitate understanding of this figure, the effective reflection wavelength bandwidths J, K, L and M corresponding to the respective design wavelengths are all connected to each other through one boundary line 42, 43 and 44. The following matters can be understood by observing this figure.

(1) Each of the reflection films 24, 25, 26 and 27 has 365 different reflection surface portions A, B, C and D, respectively.
It reflects light of nanometers and effectively uses the reflecting surface in the range of the central angle of about 60 degrees as a whole. (2) On the other hand, one type of conventional reflection interference film (for example, Japanese Patent Laid-Open No. 53-25084) reflects light of 365 nm in a portion D of the reflecting surface, that is, in the range of a central angle of about 30 degrees. Therefore, the utilization of the reflective surface is about half that of the present invention.

(3) The respective portions A, B, C, D of the reflecting surface gradually become narrower as the central angle increases. This is due to the film thickness change curves 45, 46, 47 of the respective reflecting films. This is because the film thickness rapidly decreases as the central angle increases, as indicated by 48, and even if another reflective film is laminated, the increase in the reflective surface that reflects light with a wavelength of 365 nm is slight. Is.

The present invention is not limited to the above-mentioned embodiments, and for example, the material forming the thin film may be another material other than silicon dioxide or zirconium dioxide, and the reflecting surface. Instead of dividing into four, it may be finely divided, and further, the multilayer reflection interference film of the present invention may be applied to the surface of a spherical surface or a rotating body other than a spherical surface, and the like. It goes without saying that various changes can be made without departing from the above.

[0031]

As described above, the present invention exhibits the following excellent effects. (1) Since the plurality of reflection interference films reflect the light having the specific wavelength at different portions of the reflection surface, it is possible to uniformly reflect the light of the specific wavelength over a wide range of the reflection surface. (2) Since the reflectance of the reflected light by each reflection interference film is set to a predetermined value, the intensity of the reflected light can be strengthened together with the effect of the above (1).

(3) When depositing a thin film, the object to be vapor-deposited is not rotated or a light-shielding board is not used as in the conventional case, so that the film-forming work is easy. (4) When the specific wavelength is specified to be 365 nm, it becomes possible to provide a high-intensity ultraviolet lamp, which can greatly contribute to the progress of image forming and ultraviolet drying technology.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged view of a II portion in FIG.

FIG. 3 is a cross section for explaining the basic principle of the present invention.

FIG. 4 is a diagram showing the reflection characteristics of the multilayer reflection interference film shown in FIG.

FIG. 5 is also a diagram showing reflection identification.

FIG. 6 is likewise a diagram showing a reflection characteristic.

FIG. 7 is likewise a diagram showing a reflection characteristic.

FIG. 8 is a diagram illustrating the operation of a plurality of reflection interference films.

FIG. 9 is a cross-sectional view illustrating a conventional reflection interference film and a vacuum deposition method.

10 is a diagram showing the reflection characteristics of the reflection interference film in FIG.

FIG. 11 is a cross-sectional view illustrating another conventional reflection interference film.

FIG. 12 is a cross-sectional view of an apparatus for performing vacuum evaporation while rotating a cylindrical object.

FIG. 13 is a cross-sectional view of an apparatus for performing vacuum vapor deposition while rotating a sphere.

FIG. 14 is a plan view of the light blocking plate in FIG.

[Explanation of symbols]

 24, 25, 26, 27 Reflective interference film

Claims (2)

[Claims] 1. A plurality of reflection interference films formed by alternately depositing dielectric materials having different refractive indexes on a curved surface, each reflection interference film having a film thickness at any of a plurality of positions on the curved surface having different deposition rates. Is set so that the film thickness at that location is approximately equal to one-quarter of the specified wavelength of light, and the intervals between the design wavelengths corresponding to the respective film thicknesses are reflections having a predetermined reflectance. A multilayer reflection interference film, which is set to be substantially equal to the wavelength bandwidth. 2. The multilayer reflective interference film according to claim 1, wherein the specified wavelength of light is 365 nanometers.