JP2005208212A - Method for forming reflective film, and rotary polygon mirror - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently form a reflective film on two or more formed film surfaces of a substrate for a rotary polygon mirror, and to provide a rotary polygon mirror manufactured efficiently. <P>SOLUTION: In a lower part in a vacuum tub 21 of a sputtering device 20, a target 23a for the reflective film and a target 23b for a protective film are arranged, and in an upside of the vacuum tub 21, a substrate holding part 22 is arranged. The substrate 1 for a rotary polygon mirror is fixed to the substrate holding part 22 so that the center axis line C2 may be at right angles to the targets 23a, 23b and the formed film surfaces 5 comprising a tilt angle to the center axis line C2 may face the targets 23a, 23b. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of forming a reflective film on a rotary polygon mirror substrate having a plurality of film formation surfaces, which is used in a polygon mirror or the like, and a rotary polygon mirror having a reflective film formed on such a rotary polygon mirror substrate. .

  A rotary polygon mirror such as a polygon mirror is known as one of means for scanning a laser beam or the like. The rotating polygon mirror includes, for example, a rotating polygon mirror substrate having a prismatic shape or a truncated pyramid shape, and a reflective film formed on a plurality of film forming surfaces provided along the outer periphery of the rotating polygon mirror substrate. Consists of. When the rotary polygon mirror is rotated at a high speed by a motor or the like and the laser beam is irradiated toward the film formation surface (reflection surface) on which the reflection film is formed, the incident angle of the laser beam with respect to the reflection surface changes relatively. Laser light is scanned.

Here, as a conventional method of manufacturing such a rotating polygon mirror, a method of forming a film on the outer peripheral portion of the rotating polygon mirror substrate one by one or two is used. For example, when two films are formed on six film formation surfaces, a substrate holder that exposes two film formation surfaces adjacent to each other by a specific ridge line among the six film formation surfaces is used (for example, Patent Document 1). The substrate holder has an opening through which two film formation surfaces are exposed. A mask is attached to the opening so that the vapor deposition flow does not circulate to another film formation surface adjacent to the two film formation surfaces exposed from the opening. According to such a film forming method, the mask prevents the reflective film from being formed on the remaining four film forming surfaces. In addition, when forming a reflecting film in another film-forming surface, a substrate holder is rotated 120 degree | times.
JP 2000-8163 A

However, in the method of forming one surface or two surfaces on a plurality of film formation surfaces, it has been necessary to perform film formation on a single rotary polygon mirror substrate in a plurality of times. When film formation is performed in a plurality of times, the film formation takes time, and the possibility of dust or scratches on the film formation surface or the reflection surface increases. In addition, the substrate holder that exposes only a specific film-forming surface is expensive because it requires a complicated shape, which increases production costs. Further, in the substrate holder as described above, since the ridge line between the film formation surface at the first film formation and the film formation surface at the second film formation is covered with a mask, a reflective film is formed on the ridge line. There was something I couldn't do.
The present invention has been made to solve such a problem, and efficiently forms a reflective film on a plurality of film-forming surfaces of a substrate for a rotating polygon mirror, and the rotating polygon mirror manufactured as described above. The purpose is to provide.

The invention according to claim 1 of the present invention that solves the above problems is provided on the outer peripheral portion of the rotary polygon mirror substrate having a central axis, and on a plurality of film formation surfaces having a tilt angle with respect to the central axis. When forming a reflective film by sputtering, a substrate holding unit for holding the rotary polygon mirror substrate is disposed opposite to a target that is a film raw material of the reflective film, and the rotary polygon mirror substrate is attached to the plurality of polygon mirrors. The reflective film forming method is characterized in that the film forming surface is fixed to the substrate holding portion so that the film surface faces the target and the central axis is substantially orthogonal to the target.
In this reflective film forming method, the rotating polygon mirror substrate is arranged so that all the film formation surfaces can be seen from the target, and the central axis of the rotating polygon mirror substrate and the target are substantially orthogonal. When sputtering is performed in this state, a reflective film is formed on all the film formation surfaces at once.

According to the second aspect of the present invention, a reflective film is formed by a sputtering method on a plurality of film-forming surfaces that are provided on an outer peripheral portion of a rotary polygon mirror substrate having a central axis and have a tilt angle with respect to the central axis. The cylindrical substrate holding unit that holds the substrate for the rotary polygon mirror is rotatably supported around a rotation axis along the length direction thereof, and a target that is a film material of the reflective film is supported on the substrate holding unit. The rotating polygon mirror substrate is disposed toward the outer peripheral portion, and the substrate holding portion is disposed so that the plurality of film forming surfaces face the target side and the central axis is substantially orthogonal to the target. The reflective film forming method is characterized in that the film is formed on the rotary polygon mirror substrate while being fixed and rotating the substrate holding portion around the rotation axis.
In this reflective film formation method, the rotary polygon mirror substrate is arranged so that all the film formation surfaces can be seen from the target, and the central axis of the rotary polygon mirror substrate is substantially orthogonal to the target, and the substrate is held. Since sputtering is performed while rotating the part, a reflective film is formed on all the film formation surfaces at once.

According to a third aspect of the present invention, in the method for forming a reflective film according to the first or second aspect, the rotating polygon mirror substrate is a polygon mirror substrate having six film forming surfaces. And
According to this reflection film forming method, film formation is simultaneously performed by sputtering on the six film formation surfaces of the polygon mirror substrate. For this reason, a reflective film can be formed at a time, and a polygon mirror can be manufactured efficiently.

According to a fourth aspect of the present invention, there is provided a rotary polygon mirror comprising a base having a through hole in the center and a plurality of film forming surfaces extending from an edge of the base and having a tilt angle with respect to the central axis of the through hole. A rotary polygon mirror having a reflecting film formed on a substrate for reflecting light to reflect light, wherein the reflecting film includes the film-forming surfaces, an extension line of the film-forming surface at the base, and the center. The rotary polygon mirror is characterized in that it is formed on the entire surface excluding the periphery of the through hole on the surface facing the intersection with the axis.
In this rotary polygon mirror, when a plurality of film formation surfaces are viewed from a direction that is parallel to the central axis, the reflective film is reliably formed on the ridge lines of two adjacent film formation surfaces and the ridge line with the base. Therefore, an effective area as a region for reflecting light is large, and a high-quality reflecting surface can be obtained.

According to the present invention, the reflective film is sputtered in a state where the substrate for the rotary polygon mirror is fixed so that the plurality of film formation surfaces face the target side and the central axis is substantially orthogonal to the target. As a result, the rotating polygon mirror can be manufactured more efficiently than in the case where the film formation is performed multiple times for each film formation surface. Moreover, since a special holding tool is not required, manufacturing cost can be reduced. Furthermore, since a reflective film can be formed without any breaks on all film formation surfaces including the boundary between two adjacent film formation surfaces, a high-quality rotating polygonal mirror can be obtained.
In addition, the rotary polygon mirror reflects the light because the reflective film is formed on the entire surface except the periphery of the through-hole when viewed from the direction parallel to the central axis and where all the film formation surfaces are visible. You can take a larger area.

The best mode for carrying out the invention will be described in detail with reference to the drawings.
1 to 3 show a rotating polygon mirror substrate according to the first embodiment.
The rotating polygon mirror substrate 1 is a thin plastic molded product, and includes a regular hexagonal base 2 and six side parts 3 extending obliquely downward from the sides of the base 2.
The base 2 has a through hole 4 formed at the center thereof. The central axis C1 of the through hole 4 coincides with the base 2, that is, the central axis C2 of the rotary polygon mirror substrate 1.
The outer surface of each side portion 3 is a film formation surface 5 on which a reflective film is formed. As shown in FIG. 2, each film-forming surface 5 has substantially the same tilt angle θ with respect to the central axis C2. Here, the tilt angle θ is an angle at the intersection point P1 between the extension line L1 parallel to the film formation surface 5 and the central axis C2.
Further, as shown in FIG. 1, the upper end portion of the side portion 3 is connected to the base portion 2, and the boundary is defined by a ridge line 6. The side end portion of the side portion 3 is connected to the side end portion of the other adjacent side portion 3, and the boundary is defined by the ridge line 7. As shown in FIG. 3, regular hexagonal openings 8 are formed by the lower ends of the side portions 3.

In addition, in the base 2, the area of the top surface 2a defined by the intersection P1, that is, the ridgeline 6, is smaller than the area of the opening 8 defined by the lower end of each side 3, and a small area portion. (Small enclosure).
The central axis C2 serves as a rotation axis when a reflective film is formed on the rotary polygon mirror substrate 1 to form a polygon mirror.

Next, the sputtering apparatus 20 used for forming the reflective film will be described with reference to FIG.
The sputtering apparatus 20 has a vacuum chamber 21 that can be decompressed. A substrate holding part 22 is provided in the upper part of the vacuum chamber 21. Two targets 23 a and 23 b serving as film materials are disposed in the lower part of the vacuum chamber 21. The vacuum chamber 21 is provided with a gas introduction part 24 for introducing an inert gas (for example, argon gas) into the vacuum chamber 21.

  The board | substrate holding | maintenance part 22 has the disk shape arrange | positioned horizontally. A support shaft 25 is attached to the upper surface 22 a of the substrate holding part 22 on the central axis C <b> 3 of the substrate holding part 22. The support shaft 25 is rotatably supported by the vacuum chamber 21, and the support shaft 25 and the substrate holder 22 can be rotated by a motor (not shown). Further, a screw hole 27 is provided on the lower surface 22b of the substrate holding part 22 on a predetermined circumference centered on the central axis C3. The screw holes 27 are used for fixing the rotary polygon mirror substrate 1 to the substrate holding part 22, and hexagon socket bolts 26 are screwed into the screw holes 27.

The two targets 23 a and 23 b are centered on the central axis C <b> 3 of the substrate holding part 22 and have the same height on the circumference having the same diameter as the circumference in which the screw hole 27 is provided. It is arranged toward 22. That is, in FIG. 4, a straight line passing through the center of the target 23 a facing vertically and the center of the screw hole 27 is parallel to the central axis C <b> 3. Similarly, straight lines passing through the centers of the target 23b and the screw hole 27 facing vertically are also parallel to the central axis C3. Moreover, the size of each target 23a, 23b is large enough for film-forming of each rotary polygon mirror substrate 1 arranged facing each other.
The target 23a is made of aluminum. A sputtering power supply 28a for applying a predetermined voltage to the target 23a is connected to the target 23a. The target 23b is made of silicon dioxide. A sputtering power supply 28b for applying a predetermined voltage to the target 23b is connected to the target 23b.

Next, a process of forming a reflective film on the rotary polygon mirror substrate 1 as shown in FIG. 1 using the sputtering apparatus 20 as shown in FIG. 4 will be described.
First, the rotary polygon mirror substrate 1 is fixed to the substrate holding unit 22 in a state where the vacuum chamber 21 is at atmospheric pressure. The rotary polygon mirror substrate 1 is arranged so that the base portion 2 faces downward and the opening 8 (see FIG. 3) is covered with the substrate holding portion 22. Further, the hexagon socket head cap screw 26 is screwed into the screw hole 27 of the substrate holding portion 22 while the hexagon socket head cap bolt 26 is inserted into the through hole 4 (see FIG. 1) of the base portion 2.
That is, the periphery of the through hole 4 of the base portion 2 is supported by the head portion 26 a of the hexagon socket head bolt 26 fixed to the substrate holding portion 22. Thereby, the rotating polygon mirror substrate 1 has the central axis C2 substantially orthogonal to the targets 23a and 23b, and all of the plurality of film formation surfaces 5 are arranged toward the targets 23a and 23b.

After the rotary polygon mirror substrate 1 is fixed to the substrate holder 22, the vacuum chamber 21 is evacuated by a vacuum pump (not shown). When the pressure in the vacuum chamber 21 reaches a predetermined value, an inert gas such as argon gas is introduced into the vacuum chamber 21 from the gas introduction unit 24, and the pressure in the vacuum chamber 21 is set to about 1 to 8 × 10 ⁻³ Pa. Adjust to. Further, the substrate holding unit 22 is rotated around the central axis C3 while maintaining the state where the substrate holding unit 22 is opposed to the targets 23a and 23b. When the substrate holding part 22 starts to rotate, the rotating polygon mirror substrate 1 starts to revolve around the central axis C3.
Further, the sputtering power supply 28a is operated, a voltage is applied to the target 23a, and the ionized inert gas collides with the target 23a. As a result, the aluminum knocked out of the target 23 a by the collision accumulates on the surface of the rotating polygon mirror substrate 1 that rotates together with the substrate holding part 22, and is formed on the film formation surface 5 and the head 26 a of the hexagon socket head cap bolt 26. An aluminum thin film (reflection film) is formed on the surface (top surface) 2a of the supported base 2.

When the aluminum thin film is formed to a predetermined thickness, the sputtering power supply 28a is stopped, and the application of voltage to the target 23a is stopped. Then, the sputtering power supply 28b is activated to start sputtering with the target 23b. By applying a voltage to the target 23b, inert gas ions strike the surface of the target 23b, and as a result, the top surface 2a of the base 2 supported by the film formation surface 5 and the head 26a of the hexagon socket head cap bolt 26 is obtained. A silicon dioxide thin film is formed on the formed aluminum thin film.
When the silicon dioxide thin film is formed to a predetermined thickness, the sputtering power supply 28b is stopped and the voltage application to the target 23b is stopped. This silicon dioxide thin film functions as a protective film for the aluminum thin film.

The rotating polygon mirror manufactured in this way is shown in FIG.
The rotary polygon mirror 30 has a reflective film (aluminum thin film) and a protective film (silicon dioxide thin film) laminated in this order on the surfaces of all the side portions 3, that is, on all the film formation surfaces 5, so that the reflection surface 31 is formed. Is formed. In addition, on the top surface 2a of the base 2 arranged toward the targets 23a and 23b, a reflective film and a protective film are laminated in this order on the entire surface excluding the peripheral portion 4a of the through hole 4. The reason why the film is not formed on the peripheral portion 4 a of the through-hole 4 is that it is masked by the head portion 26 a of the hexagon socket head bolt 26. In addition, a reflective film and a protective film are uniformly formed on the ridge line 7 that is a boundary between two adjacent film formation surfaces 5 and also on the ridge line 6 that is a boundary between each film formation surface 5 and the top surface 2a. ing.

According to this embodiment, when forming a reflective film by sputtering on the rotary polygon mirror substrate 1 having a plurality of film-forming surfaces 5 having a tilt angle θ with respect to the central axis C2, the base 2 is placed on the target 23a. , 23b and the central axis C2 and the targets 23a, 23b are arranged so as to be substantially orthogonal to each other, so that a reflective film can be formed on all the film formation surfaces 5 at once. For this reason, the time required for film formation can be shortened, and the working efficiency is improved. Further, according to such a film forming method, the reflective film can be formed on all the film forming surfaces 5 and the ridgelines 6 and 7 thereof. Since no specially shaped substrate holding part or mask is required, the rotary polygon mirror substrate 1 can be easily set and the manufacturing cost can be reduced.
The rotating polygon mirror 30 as a result of the film forming method also has a reflection film formed on all the film forming surfaces 5 and the ridges 6 and 7, so that light can be reflected in a wide area. This is possible, and a high-quality reflecting surface 31 is obtained.

In the sputtering apparatus 20, the targets 23 a and 23 b may be installed downward in the upper part of the vacuum chamber 21. In this case, the substrate holding part 22 is arranged at the lower part in the vacuum chamber 21, and a screw hole 27 is provided on the surface 22 a side which becomes the upper surface of the substrate holding part 22. Further, instead of rotating the substrate holding part 22, the two targets 23a and 23b may be rotated around the central axis C3. Further, the substrate holding part 22 and the targets 23 a and 23 b may be arranged in parallel to the height direction of the vacuum chamber 21.
In order to firmly attach the reflective film to the film forming surface 5 of the plastic rotary polygon mirror substrate 1, an adhesion layer may be formed on the film forming surface 5, and the reflective film may be formed on the adhesion layer. . In this case, a silicon dioxide film is preferable as the adhesion layer.
The film material of the reflective film may be silver or gold, or other metal material or alloy instead of aluminum. The protective film can be made of a material other than silicon dioxide as long as it is transparent to the reflected light.

  In addition, this film forming method includes, for example, an arbitrary number of three or more film forming surfaces 5 such as an optical component having four film forming surfaces 5 or an optical component having five or eight film forming surfaces 5. It can apply to an optical component provided with. Further, when the optical component is a polygon mirror substrate, a truncated pyramid shaped substrate may be used. The substrate material is not limited to plastic, and glass, metal, or the like can be used.

Next, a second embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same component as said 1st embodiment. Moreover, the description which overlaps with 1st embodiment is abbreviate | omitted.
This embodiment is characterized in that a sputtering apparatus 40 as shown in FIG. 6 is used for forming a reflective film on a rotary polygon mirror substrate as shown in FIGS. 1 to 3 by a sputtering method.

  The sputtering apparatus 40 includes a vacuum chamber 41 that can be depressurized, and a gas introduction unit 42 that can introduce an inert gas or the like is attached to the vacuum chamber 41. Further, in the vacuum chamber 41, a substrate holding portion 43 for holding the rotary polygon mirror substrate 1 is arranged along the height direction of the vacuum chamber 41, and the substrate holding portion 43 is sandwiched between the left and right sides. Two targets 44a and 44b are arranged.

The substrate holding portion 43 has an outer peripheral portion 45 formed in a cylindrical shape, and a total of eight screw holes 46 are provided at positions 90 ° out of phase along the length direction of the outer peripheral portion 45. Yes. Further, the substrate holding portion 43 is supported by the vacuum chamber 41 so as to be rotatable around a central axis (rotation axis) C4 along the length direction of the outer peripheral portion 45. The rotation shaft of the substrate holding unit 43 is connected to a motor (not shown) so that the substrate holding unit 43 can be rotated at a predetermined speed during film formation.
Each of the targets 44 a and 44 b is arranged so as to be substantially orthogonal to the radial direction of the outer peripheral portion 45. The size of each of the targets 44a and 44b is large enough to form a film on the two rotary polygon mirror substrates 1 arranged to face each other. The target 44a is made of aluminum and connected to a sputtering power source 47a. The target 44b is made of silicon and connected to a sputtering power supply 47b.

Next, a process for forming a reflective film using such a sputtering apparatus 40 will be described.
First, the rotary polygon mirror substrate 1 is fixed to the substrate holding portion 43 so that the central axis C <b> 2 coincides with the radial direction of the substrate holding portion 43. Specifically, the hexagon socket head bolt 48 is screwed into the screw hole 46 of the substrate holder 43 while the hexagon socket head bolt 48 is inserted into the through hole 4 (see FIG. 1) of the base portion 2 of the rotary polygon mirror substrate 1. Enter. Accordingly, the periphery of the through hole 4 of the base portion 2 is supported by the head portion 48 a of the hexagon socket head bolt 48, and the rotary polygon mirror substrate 1 is positioned and fixed to the substrate holder 43 via the hexagon socket head bolt 48. The

When the rotary polygon mirror substrate 1 is fixed, the vacuum chamber 41 is evacuated. Thereafter, an inert gas such as argon gas and oxygen gas are introduced, the pressure in the vacuum chamber 41 is adjusted to about 1 to 8 × 10 ⁻³ Pa, and the substrate holding portion 43 is rotated about its central axis C4. As the substrate holder 43 rotates, the rotating polygon mirror substrate 1 revolves around the central axis C4.
Then, the sputtering power supply 47b is operated to apply a voltage to the target 44b, and silicon is knocked out of the target 44b with ions of an inert gas. From this silicon and oxygen gas, a silicon dioxide thin film is formed on exposed portions on the film formation surface 5 of the side portion 3 and the top portion 2a of the base portion 2 of the rotary polygon mirror substrate 1.
When the silicon dioxide thin film is formed with a predetermined thickness, voltage application to the target 44b is stopped. Then, an aluminum thin film is formed using this silicon dioxide thin film as an adhesion layer. That is, the introduction of oxygen gas is stopped, and the pressure in the vacuum chamber 41 is adjusted to about 1 to 8 × 10 ⁻³ Pa only with the inert gas. Next, the sputtering power supply 47a is operated to apply a voltage to the target 44a, and an aluminum thin film is formed on the silicon dioxide thin film of the rotary polygon mirror substrate 1.
When the aluminum thin film is formed to a predetermined thickness, voltage application to the target 44a is stopped, and a protective film made of a silicon dioxide thin film is formed on the aluminum thin film in the same manner as the adhesion layer.

  As shown in FIG. 5, the rotary polygon mirror manufactured in this way has an adhesion layer (silicon dioxide thin film) on the six film formation surfaces 5 and the entire surface excluding the peripheral portion 4a of the through hole 4 on the base 2. ), A reflective film (aluminum thin film), and a protective film (silicon dioxide thin film) are laminated in this order. The reflection surface 31 formed on the outer surface of the side portion 3 by the deposition of these thin films is on the ridge line 7 that becomes the boundary between two adjacent film formation surfaces 5 or the boundary between each film formation surface 5 and the top surface 2a. Also on the ridgeline 6, the adhesion layer, the reflective film, and the protective film are uniformly formed.

According to this embodiment, when forming a reflective film by sputtering on the rotary polygon mirror substrate 1 having a plurality of film formation surfaces 5 having a tilt angle θ with respect to the central axis C2, the base 2 is placed on the target 44a. , 44b and the central axis C2 of the rotary polygon mirror substrate 1 and the targets 44a, 44b are arranged so as to be substantially orthogonal to each other, so that the reflection film can be formed on all the film formation surfaces 5 at once. . For this reason, the time required for film formation can be shortened, and the working efficiency is improved. Further, according to such a film forming method, the reflective film can be formed on all the film forming surfaces 5 and the ridgelines 6 and 7 thereof.
The rotating polygon mirror 30 as a result of the film forming method also has a reflection film formed on all the film forming surfaces 5 and the ridges 6 and 7, so that light can be reflected in a wide area. A possible high quality reflective surface 31 is obtained. Moreover, since the adhesion layer is provided, the adhesion strength between the reflective film and the rotary polygon mirror substrate 1 is high, and the durability is excellent.

In FIG. 6, the central axis C <b> 4 of the substrate holder 43 and the height direction of the vacuum chamber 41 coincide with each other, but the central axis C <b> 4 of the substrate holder 43 is provided horizontally with respect to the vacuum chamber 41. May be.
Further, the outer peripheral portion 45 of the substrate holding portion 43 is not limited to a cylindrical shape, and may be a prismatic shape such as a hexagonal prism. In this case, the screw hole 46 is provided so as to be orthogonal to the central axis C4 along the length direction of the substrate holding portion 43 and orthogonal to the side surface having the prism shape.
Further, a reflective film may be formed directly on the film formation surface without forming an adhesion layer. Further, silicon dioxide may be used for the target 44b. In this case, the gas introduced into the vacuum chamber 41 may be only an inert gas or a mixed gas of an inert gas and an oxygen gas.

1 is a perspective view of a rotary polygon mirror substrate in an embodiment of the present invention. FIG. 4 is a side view of the rotary polygon mirror substrate, with the upper half in cross section. It is the figure which looked at the board | substrate for rotary polygon mirrors from the lower side. It is a figure which shows the structure of the sputtering device in embodiment of this invention. It is a top view of the rotary polygon mirror in the embodiment of the present invention. It is a figure which shows the structure of the sputtering device in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating polygon mirror substrate 2 Base 2a Top surface 3 Side 4 Through hole 4a Peripheral part
5 Deposition surfaces 22, 43 Substrate holders 23a, 23b, 44a, 44b Target 30 Rotating polygon mirror 31 Reflecting surface C2 Center axis C3 Center axis (rotation axis)
C4 Center axis (rotary axis)
L1 extension line P1 intersection

Claims (4)

  When a reflective film is formed by sputtering on a plurality of film formation surfaces provided on the outer peripheral portion of a rotating polygon mirror substrate having a central axis and having an inclination angle with respect to the central axis, it becomes a film material for the reflective film A substrate holding part for holding the rotary polygon mirror substrate is disposed opposite to the target, the rotary polygon mirror substrate is arranged such that the plurality of film formation surfaces face the target side, and the central axis is A method for forming a reflective film, wherein the reflective film is fixed to the substrate holder so as to be substantially orthogonal to the target.   In forming a reflective film by sputtering on a plurality of film-forming surfaces provided on the outer peripheral portion of a rotating polygon mirror substrate having a central axis and having an inclination angle with respect to the central axis, the substrate for the rotating polygon mirror is provided. A cylindrical substrate holding part to be held is rotatably supported around a rotation axis along its length direction, and a target that is a film raw material for the reflective film is arranged toward the outer peripheral part of the substrate holding part, The rotating polygon mirror substrate is fixed to the substrate holding portion such that the plurality of film formation surfaces face the target side and the central axis is substantially orthogonal to the target, and the substrate holding portion is A method of forming a reflective film, wherein the film is formed on the rotary polygon mirror substrate while rotating about the rotation axis.   The method for forming a reflective film according to claim 1, wherein the rotary polygon mirror substrate is a polygon mirror substrate having six film formation surfaces. A reflective film is formed on a rotating polygon mirror substrate having a base having a through hole in the center and a plurality of film forming surfaces extending from the edge of the base and having an inclination angle with respect to the central axis of the through hole The reflective polygonal mirror is a reflective surface that reflects light, and the reflective film is formed on each of the film formation surfaces and a surface of the base portion that extends toward the intersection of the extension line of the film formation surface and the central axis. The rotary polygon mirror is formed on the entire surface excluding the periphery of the through hole.

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