JP2010266866A - Polygon mirror, optical scanner, and electrophotographic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polygon mirror that requires a low cost, has high productivity, and also has small reflectance variation in a large incident angle range, to provide a method of manufacturing the polygon mirror, and further to provide an inexpensive and compact optical scanner and electrophotographic device. <P>SOLUTION: In the polygon mirror having a plurality of reflecting surfaces for reflecting light, a single layer film is formed on the reflecting surfaces. In the single layer film, the film thickness of the film thickness distribution is uniform in a position corresponding to the incident angle of a Brewster angle or smaller, and the film thickness provide the reflectance at the Brewster angle in the position corresponding to the incident angle exceeding the Brewster angle. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a reflective polygon mirror mounted on an optical scanning device used in electrophotographic equipment and the like, and more particularly to a film formed on a reflective surface of a polygon mirror. The present invention also relates to an optical scanning device and an electrophotographic apparatus.

  2. Description of the Related Art Conventionally, in an optical scanning device such as a laser beam printer, a light beam (laser light beam) light-modulated on the surface of an image carrier through a rotating polygon mirror (polygon mirror) as disclosed in Japanese Patent Publication No. 62-36210. The image information is written and read out by optical scanning.

   FIG. 8 is a schematic diagram illustrating an exemplary configuration of a main part of the optical scanning device. In FIG. 8, a light beam emitted from a light source unit 1 such as a semiconductor laser is converted into a parallel light beam by a collimator lens 2 and condensed by a cylindrical lens 83 having a refractive power only in the sub-scanning direction. The light is incident linearly on the deflecting / reflecting surface 4a. The collimator lens 2 and the cylindrical lens 83 constitute an imaging optical system. The surface to be scanned by the light beam reflected and deflected by the deflecting / reflecting surface 4a is formed by a lens 87a having a negative refractive power composed of a spherical surface constituting the scanning lens 87 and a lens 87b having a toric surface having mutually different refractive powers in two directions. The light is guided onto 89 to form spots. The deflector 4 is rotated in the direction of arrow 86 by the motor 85 about the rotation shaft 82 to optically scan the deflection scanning surface on the surface to be scanned 89 in the direction of arrow 90 (main scanning direction).

  In many cases, the polygon mirror is made of aluminum, plastic, glass or the like. Then, by applying a vapor deposition film or an anodic oxide film on the reflection surface, the reflectance is increased, the angle dependency is eliminated, or oxidation is prevented.

Japanese Examined Patent Publication No. 62-36210

  In many cases, the reflective surface of a polygon mirror as an optical deflector is provided with a reflection-enhancing film or the like by a vacuum deposition method, so that differences in film thickness due to manufacturing errors or partial film thickness differences due to manufacturing methods are reflected. Due to the variation in characteristics, it was necessary to use a highly accurate vapor deposition device, to reduce the influence by increasing the basic reflectivity with a multilayer film structure, or to perform a special vapor deposition method . For this reason, it has led to an increase in cost and a factor of reducing the degree of freedom of the film.

  In the method of applying an amorphous fluororesin film on the anodized film, the angle dependency of the reflectance is reduced by the anodized film, and the durability against dew condensation is increased by the amorphous fluororesin film. In this anodic oxidation process, the polygon mirror needs to be sufficiently cleaned, so that a large-scale apparatus is required and there is a problem in terms of cost.

  In order to solve the above problems, it has been proposed that a single layer film can be formed at a lower cost than the above two examples by a rotary wet film forming method. However, when the polygon mirror is formed by the rotary wet film forming method, the entire reflecting surface is immersed in the coating solution, and therefore the coating solution is applied to the surface other than the reflecting surface. As a result, there was a tendency that the coating liquid adhering to the surface other than the reflection surface during the rotation film formation was concentrated on the reflection surface, resulting in a tendency that the variation in film thickness increased or an accidental film disturbance occurred. Therefore, it has been a challenge to improve the productivity of the rotary wet film forming method and reduce the cost.

  Further, in recent years, the range of incident angles of light incident on the polygon mirror tends to widen due to the desire to make the optical scanning device compact. On the other hand, various optical films are formed on the reflective surface of the polygon mirror for uniform angle of reflectivity, but these optical films have an angle (Brewster angle) that totally transmits p-polarized light. In other words, there is always an angle that matches the reflectivity of the lower layer when the incident angle range is taken across the Brewster angle. Assuming that a uniform film thickness is formed in a polygon mirror that is desired to have a constant reflectivity with respect to the incident angle range, the reflectivity can be reduced especially when the incident angle spreads to the wide angle side from the Brewster angle. There was a tendency that the fluctuation width was wide and it was difficult to obtain the angular uniformity of the reflectance. For this reason, it has been difficult to obtain a polygon mirror that can cope with a wide range of incident angles with conventional techniques, and as a result, it has been difficult to obtain a compact optical scanning device.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a polygon mirror that can be manufactured at low cost with high productivity and a manufacturing method thereof, and provides a polygon mirror that has a low reflectance change in a wide incident angle range and a manufacturing method thereof. The purpose is to do.

  It is another object of the present invention to provide an inexpensive and compact optical scanning device and electrophotographic apparatus.

  The present invention is a polygon mirror having a plurality of reflection surfaces for reflecting light, wherein the reflection surface is formed by forming a single layer film made of a material having a refractive index of 1.45 or less on a substrate. Is a polygon mirror.

  In this polygon mirror, the substance having a refractive index of 1.45 or less is preferably an amorphous fluororesin.

  The thickness of the single layer film is preferably 85 to 110 nm.

  Further, the single layer film is preferably formed by a wet film forming method.

  It is also preferable that the single-layer film is formed by a rotating wet film forming method in which a solution containing a substance having a refractive index of 1.45 or less is applied to a reflecting surface, and then the reflecting surface is rotated in the radial direction. .

The present invention also relates to a method for manufacturing a polygon mirror having a film formed on a reflective surface, the coating step of applying a solution containing a substance forming the film to the reflective surface, and the subsequent reflective surface in the radial direction. In the manufacturing method of the polygon mirror having a coating film forming step of forming a coating film made of a solution on the reflecting surface by rotating the polygon mirror
In the coating step, when the shortest distance between the reflecting surface and the rotation axis is Ri, the solution is applied only to a portion of the polygon mirror that is not less than Ri from the rotation axis. It is.

  In this method, in the coating step, the solution is stored in a tank, the distance between the solution surface formed in the tank and the axis of rotation is R, and the point farthest from the axis in the reflecting surface and the axis It is preferable that the coating is carried out by rotating with Ri ≦ R ≦ Ro, where Ro is the distance to.

  Further, it is preferable to perform the coating by rotating at a rotation speed or less at which the coating liquid surface does not violately wave.

  Further, in the coating step, it is preferable to perform the coating by storing the solution in a tank and immersing the polygon mirror in the solution so that the reflection surface is in contact with the liquid surface formed in the tank.

  Alternatively, in the coating step, it is preferable to perform the coating by pressing a soft medium impregnated with the solution against the reflecting surface.

  In the coating step, it is also preferable to perform coating by spraying a coating solution only on the reflective surface.

  The present invention is also a polygon mirror manufactured by the above method.

  Furthermore, the present invention is a polygon mirror having a plurality of reflection surfaces for reflecting light, and having a film having a film thickness distribution on the reflection surface.

  In this polygon mirror, it is preferable that the film thickness distribution is a film thickness at which a reflectance at the Brewster angle can be obtained at a position corresponding to an incident angle of 10 to 70 °.

  The film thickness distribution is uniform at a position corresponding to an incident angle equal to or smaller than the Brewster angle, and a reflectance at the Brewster angle is obtained at a position corresponding to an incident angle exceeding the Brewster angle. A film thickness is also preferred.

  Alternatively, it is also preferable that the film thickness distribution has an inclination that becomes uniformly thin from a position corresponding to an incident angle of 10 ° to 70 °.

  The present invention also provides a light source, an imaging optical system that focuses and collects light emitted from the light source, an optical deflector that reflects and deflects the focused light, and the deflected light is scanned. An optical scanning device including a scanning lens that leads to a surface, wherein the optical deflector includes the polygon mirror described above.

The present invention further includes means for charging the photoreceptor, exposure means for exposing the charged photoreceptor to form a latent image, toner image forming means for supplying toner to the latent image to form a toner image, and the toner In an electrophotographic apparatus having a transfer means for transferring an image to a transfer material, and a cleaning means for removing residues and foreign matters on the surface of the photoreceptor.
An electrophotographic apparatus comprising the optical scanning device as the exposure means.

  As described above, according to the present invention, in a reflective polygon mirror mounted on an optical scanning device used in an electrophotographic apparatus or the like, a substance having a refractive index of 1.45 or less on the reflective surface of the polygon mirror, particularly By forming a single layer of amorphous fluororesin, which is a low refractive index film material, by a rotary wet film formation method, it is possible to manufacture a polygon mirror at a lower cost than vacuum deposition or anodization. .

  Further, according to the present invention, in the rotary wet film forming method of the polygon mirror, when the shortest distance between the reflecting surface and the rotation axis at the time of application is Ri, the application liquid is applied only to the area of Ri or more of the polygon mirror. Thus, variations in film thickness and accidental film disturbance can be suppressed, and the productivity of the polygon mirror can be improved. Therefore, the polygon mirror can be made inexpensive.

  The optical scanning device of the present invention provided with such a polygon mirror, and the electrophotographic apparatus provided with this optical scanning device can be produced at low cost.

  Furthermore, by providing the film formed on the reflecting surface of the polygon mirror with an appropriate film thickness distribution, the angle uniformity of the reflectance can be obtained over a wide range of incident angles. In addition, this contributes to the compactness of the optical scanning device, and the optical scanning device can be manufactured at a lower cost. Furthermore, the electrophotographic apparatus of the present invention provided with such an optical scanning device can be made compact and can be reduced in cost.

It is a graph explaining the relationship between the film thickness which concerns on Experimental example 1, an incident angle, and a reflectance. It is a graph explaining the relationship between the film thickness which concerns on Experimental example 1, and the reflectance difference in the incident angle of 15-56 degrees. It is a figure explaining the dipping concerning Example 1. FIG. It is a figure explaining the rotary wet film-forming method which concerns on Example 2. FIG. 6 is a photograph explaining “liquid accumulation trace” and “flow stain trace” according to Example 3. FIG. FIG. 10 is a schematic diagram for explaining “liquid accumulation trace” and “flow stain trace” according to the third embodiment. It is a figure explaining the relationship between the amorphous fluororesin solution density | concentration which concerns on Example 4, and the reflectance difference in 15-56 degrees of incident angles. It is the schematic which shows the principal part structural example of an optical scanning device. FIG. 10 is a schematic diagram of film shape disturbance according to Example 7. FIG. 10 is a diagram illustrating an outline of a coating method according to Example 8. FIG. 10 is a diagram illustrating an outline of Application Example II according to Example 9. FIG. 10 is a diagram showing an outline of Application Example III according to Example 9. FIG. 10 is a diagram showing an outline of Application Example IV according to Example 9. FIG. 10 is a diagram illustrating an outline of Application Example V according to Example 9. According to Example 10 is a diagram for explaining a relationship between reflectance and the incident angle upon a uniform film thickness when forming the SiO ₂ aluminum substrate. According to Example 10, a film thickness, for explaining the relationship between the incident angle and reflectance diagram when the desired film thickness distribution when forming the SiO ₂ aluminum substrate. (A) is a film thickness distribution state with respect to the incident angle, and (a) is a diagram for explaining the reflectance with respect to the incident angle at this time.

  That is, the present invention relates to a reflection type polygon mirror mounted on an optical scanning device used in an electrophotographic apparatus or the like, in which a single layer film of a material having a refractive index of 1.45 or less is formed on the reflection surface of the polygon mirror. It is a mirror.

  By forming the single-layer film on the reflection surface, it is possible to suppress the dependence of reflectance on the incident angle of light incident on the reflection surface. This eliminates the need for strict control during film formation.

  The single layer film can be formed by a vacuum film formation method typified by vapor deposition or sputtering or a wet film formation method using a solution, but the equipment used in the vacuum film formation method has high equipment costs. A wet film-forming method that can reduce the equipment cost is particularly desirable.

  The wet film-forming method is a method or solution in which a desired film quality or a solution containing a film quality precursor is applied to a substrate, and the solvent of the solution is removed or the precursor is reacted to form a desired film on the substrate. In this method, a desired film is formed by a reaction between a substrate and a substance in a solution.

  As a wet film forming method, a solution wet film forming method typified by dip coating or spin coating, or an aluminum oxide thin film can be formed by using an anodic oxidation method particularly when the polygon mirror base material is aluminum. However, it is particularly desirable to use a solution wet film-forming method with a low burden of coating equipment.

  The solution wet film forming method is a method in which a solution obtained by dissolving a film forming substance in a solvent is applied to a surface on which a film is to be formed, and dried or baked to obtain a film.

  The dip coating and spin coating are suitable for forming one surface or two parallel surfaces, but for the formation of polyhedrons found in the polygon mirror, a rotating film forming method in which the reflecting surface is in the radial direction of rotation is used. Most desirable. The meaning of taking the reflecting surface in the radial direction of rotation is that the normal line of the reflecting surface coincides with the rotating radial direction.

  The film material to be deposited on the reflective surface of the polygon mirror can be appropriately determined in consideration of the durability under the use conditions. For example, amorphous fluororesin, fluoroacrylate, silicon dioxide or the like can be used. Among these, an amorphous fluororesin that is inert to ozone and water and does not show corrosion due to the influence of moisture and corrosion of the substrate is particularly desirable. As the amorphous fluororesin, for example, a substance represented by structural formula (1) or structural formula (2) can be used.

  The refractive index of the amorphous fluororesin has a refractive index of 1.34 with respect to light having a wavelength of 680 nm, and when this amorphous fluororesin is deposited on the reflective surface of the polygon mirror at 88 to 109 nm, The change in reflectance at an incident angle of 15 to 56 ° can be suppressed to within ± 1.0%.

  When the film having the above thickness is formed by the above rotation film forming method, it is desirable that the solvent evaporation rate is low in the film forming process. Since the evaporation rate of the solvent becomes slower as the boiling point of the solvent becomes higher, the boiling point of the solvent is particularly preferably 180 ° C. or higher. A solvent that evaporates at a temperature that does not deform the substrate is desirable. For example, when an aluminum substrate is used, the boiling point of the solvent is preferably 280 ° C. or lower.

  As other physical properties relating to the solvent, it is preferable that there is little change in the structure due to the environment and that it is odorless in the working environment.

  As the solvent, for example, a substance represented by the structural formula (3) can be preferably used.

  The base material on which the single-layer film is formed is not particularly limited as long as it can be used for polygon mirrors such as aluminum, plastic, and glass.

  In a polygon mirror in which a single layer film of amorphous fluororesin is formed on the base material, the solution remains at the end of the reflection surface after rotating film formation, or traces of the solution flowing in a streak pattern on the reflection surface may remain. In order to form a uniform film with good productivity, it is desirable to rotate the film around 2000 to 4000 rpm, and to continue rotating for 60 seconds or more.

  In a rotational film formation method for a polygon mirror in which a single layer film of OLE_LINK1 amorphous fluororesin OLE_LINK1 is formed on the base material, a desired film thickness is formed with high productivity when forming the film at the above rotation speed and rotation time. For this purpose, it is most desirable to use a 1.5 to 3.0% solution.

  The polygon mirror formed by the method as described above has little angle dependency of the reflectance, and it becomes possible to manufacture a polygon mirror excellent in durability against condensation on the reflecting surface at a very low cost. That is, an optical scanning device, an electrophotographic apparatus and the like equipped with a polygon mirror formed by the above method can be manufactured at a lower cost than conventional ones.

  In the rotary wet film formation, a coating process for coating the coating liquid on the reflecting surface of the polygon mirror, and subsequently, a film thickness control process for rotating the polygon mirror while controlling the rotation speed to obtain a desired film thickness. Have. Usually, it also has a baking step in which the solvent contained in the coating solution is skipped to dry and fix the film. In the coating process of the rotary wet film forming method, it is preferable to apply the coating liquid to a region equal to or greater than Ri from the rotation axis of the polygon mirror, where Ri is the shortest distance between the reflecting surface and the rotation axis. The application region is governed by the process of applying a desired coating solution to the reflecting surface before entering the rotation for controlling the film thickness. Even if it is applied up to an area of less than Ri in the coating process, it is possible to control the film thickness as long as the coating is sufficiently applied to the reflecting surface. However, it is particularly desirable to apply only to the area of Ri or more in terms of suppressing variations in film thickness and accidental film disturbance.

  As an example of a method for applying the coating liquid to the reflecting surface, it is possible to immerse the reflecting surface in the coating liquid while rotating a polygon mirror. In this case, in order to apply only to a region of Ri or more from the rotation axis, when the distance between the point farthest from the axis in the reflecting surface and the axis is Ro, the distance between the rotation axis and the coating liquid surface is as follows. It must be less than Ro and greater than Ri. When coating is performed by rotating a regular n-prism polygon mirror having a regular n-gonal prism shape with the central axis of the regular n-prism as a rotation axis, Ri is a radius of a cylinder inscribed in the reflective surface, and Ro Is the radius of the cylinder circumscribing the reflecting surface. When R is the distance between the solution surface and the rotation axis, the region where Ri ≦ R ≦ Ro is the region between the inscribed cylinder and the circumscribed cylinder. At this time, the relationship between Ro and Ri is Ri / Ro = cos (circumference ratio / n).

  Further, it is preferable that the rotation speed when the reflecting surface is immersed in the coating liquid while rotating the polygon mirror does not cause the coating liquid surface to violately. Here, the fact that the wave does not violately means that the coating liquid does not touch the area below Ri from the rotation axis. For example, in the case of a 6-sided polygon mirror having a circumscribed cylinder radius of 20 mm and a reflecting surface having a hexagonal column shape, it is desirable that the speed be 200 rpm or less.

  Another example of the method of applying the coating liquid to the reflective surface is to apply only to the reflective surface by immersing the reflective surface in contact with the coating liquid surface with the reflective surface sequentially parallel to the coating liquid surface. In this case, the reflecting surface is made the coating liquid surface while maintaining a constant rotation so that the coating liquid is not attracted by gravity and spreads from the rotation axis to a region less than Ri (in the case of a regular n-prism polygon mirror). It is particularly desirable to touch.

  Another example of the method of applying the coating liquid to the reflective surface is to press a soft medium impregnated with the coating liquid against the reflective surface. In this case, when the medium is pressed against the reflection surface, a medium that is sufficiently soft so that the reflection surface is not scratched and can sufficiently contain the coating liquid can be selected as appropriate. A foamed sponge is particularly suitable.

  Another example of the method for applying the coating liquid to the reflective surface is to spray the coating liquid onto the reflective surface. In this case, it is particularly desirable that the angle of spraying perpendicularly to the rotation axis of the polygon mirror and spraying the coating liquid is an elevation angle.

  If the coating liquid is applied to the reflection surface by the above-described method, the application area on the polygon mirror is only an area of Ri or more from the rotation axis (in the case of a regular n-prism polygon mirror, outside the inscribed cylinder of the reflection surface). The film thickness variation is reduced, a high quality film is stably obtained, the occurrence of accidental film disturbance is suppressed, the manufacturing defect loss is reduced, and the polygon mirror is highly productive. It can be manufactured at low cost. In addition, an optical scanning device, an electrophotographic apparatus, and the like on which a polygon mirror formed by the above method is mounted can be manufactured at a higher quality and at a lower cost than conventional ones.

  In addition, by intentionally having an appropriate film thickness distribution on the film formed on the reflective surface, the angle dependency of the reflectance can be further suppressed, and a more compact optical scanning device can be obtained. preferable.

  In general, if the film thickness does not cause multiple reflection in the film, the reflectance tends to decrease as the film thickness increases in the incident angle range narrower than the Brewster angle. On the other hand, in the incident angle range wider than the Brewster angle, the reflectance tends to increase as the film thickness increases. This is utilized in the present invention.

  In other words, the film thickness at which the reflectance of the Brewster angle can be obtained is theoretically determined for each incident angle, so that the film thickness is faithfully formed on the reflecting surface to suppress the angle dependency of the reflectance. It is particularly desirable from the viewpoint of.

  When the incident angle of P-polarized light is limited to a range narrower than the Brewster angle, it is easy to realize the uniformity of reflectance with a uniform film thickness. At this time, the reflectance rapidly increases on the wide angle side from the Brewster angle. Therefore, an ideal film shape can be obtained by guaranteeing uniform reflectance on the narrower angle side than the Brewster angle with a desired uniform film thickness, and reducing the film thickness only in the area irradiated with light at a wider angle than the Brewster angle. Can be approximated. This technique is also particularly desirable in that film formation is easier than changing the film thickness over the entire range of the film.

  In a film forming method generally used as a film forming method for a polygon mirror, an advanced film forming technique is required to obtain an arbitrary film thickness, and the number of man-hours is often increased. Therefore, it is desirable from the viewpoint of actual production to approximate an ideal film shape by providing a uniform thickness distribution.

  A film having such a film thickness distribution can be formed by a dipping method with a controlled pulling speed, but a rotating wet film forming method is particularly desirable for a polygon mirror that is a polyhedron. In the rotary wet film formation method, after applying the solution to the reflective surface, the solution is collected on the exit side of the polygon rotation (upstream side in the rotation direction) and rotated from the entry side (downstream side in the rotation direction). A film having a film thickness gradient can be formed. This gradient can be controlled by the rotational speed, the solution concentration, and the like.

  In the present invention, the form of the optical deflector is not particularly limited by the present invention except that it has the polygon mirror of the present invention, and can take any form as long as it is an optical scanning apparatus that can be used in electrophotographic equipment. .

  The form of the optical scanning apparatus of the present invention is not particularly limited by the present invention except that the optical deflector is provided, and any form can be adopted as long as it can be used for electrophotographic equipment.

  In general, an optical scanning apparatus includes a light source, an imaging optical system that focuses and collects light emitted from the light source, an optical deflector that reflects and deflects the focused light, and deflected light. A scanning lens for guiding the light to the surface to be scanned. In the optical scanning device of the present invention, the optical deflector includes the above-described polygon mirror in such a configuration.

  The electrophotographic apparatus of the present invention is not particularly limited by the present invention except that it includes the above-described optical scanning device. For example, the electrophotographic apparatus of the present invention includes an electrophotographic apparatus, and the configuration thereof includes a photoconductor. Charging means, exposure means for exposing a charged photoreceptor to form a latent image, toner image forming means for supplying toner to the latent image to form a toner image, and transfer for transferring the toner image to a transfer material And a cleaning means for removing residues and foreign matters on the surface of the photoreceptor, and the optical scanning device is provided as the exposure means.

(Experimental example 1)
In this experimental example, a film formed by measuring the base material of the polygon mirror with an ellipsometer to estimate the optical properties of the reflecting surface of the polygon mirror, and further applying a coating solution by dipping on a glass plate and drying it. In the same manner, the optical properties of the film material were estimated by measuring with an ellipsometer, and then the reflectance when the film material was applied to the polygon mirror was numerically analyzed.

  Aluminum was used for the polygon mirror substrate, and the coating solution used was a solution in which 2% by mass of fluoroacrylate was dissolved in a substance represented by structural formula (3) (trade name: CT-solv.180: manufactured by Asahi Glass Co., Ltd.).

   1 and 2 show the numerical analysis results when the film material is formed on the polygon mirror as described above. The horizontal axis in FIG. 1 represents the incident angle of light, and the vertical axis represents the reflectance. The horizontal axis in FIG. 2 represents the thickness of the film on the polygon mirror reflecting surface, and the vertical axis represents the difference in reflectance between incident angles of 15 ° and 56 °. FIG. 2 confirms that the film thickness at which the difference in reflectance is zero is 93 nm and 166 nm. From FIG. 1, it can be seen that the reflectance varies greatly with the incident angle at the film thickness of 166 nm. Therefore, it can be said that the film thickness with an angle difference of reflectance of 1% or less is 84 to 104 nm.

  In addition to the above results, Table 1 shows the numerical analysis results for other film materials obtained in the same manner.

  As can be seen from Table 1, the smaller the refractive index, the wider the width of the film thickness at which the angle difference is 1% or less, and it can be said that a material having a low refractive index is suitable for reducing the angle dependency of the reflectance. More preferably, an amorphous fluororesin is most suitable for the purpose of the present invention.

[Example 1]
In this example, an amorphous fluororesin is applied to an aluminum substrate, and the angle dependency of reflectance is suppressed.

  Dipping, which is a typical wet film forming method, was performed. As shown in FIG. 3, an aluminum polygon mirror (before film formation) 4b made of aluminum having two parallel reflecting surfaces 4a is fully immersed in the coating solution 5, and this is pulled up and baked to form an amorphous fluororesin film. After forming, the reflectance of the reflecting surface was measured.

  As the coating liquid, an amorphous fluororesin (trade name: Cytop CTL-802: manufactured by Asahi Glass Co., Ltd.) is added to a substance (trade name: CT-solv. 180: manufactured by Asahi Glass Co., Ltd.) represented by the structural formula (2.0). When a mass% dissolved solution is used, the pulling rate is raised at 80 mm / min, and baking is performed at 170 ° C. for 30 minutes, a film thickness of about 100 nm is formed. The change in reflectance at an incident angle of 15 to 56 ° at that time is 1 0.0% or less.

[Example 2]
In this example, when an amorphous fluororesin is applied to a polyhedral polygon mirror, the rotating wet film-forming method of the present invention is effective.

  Six polygon mirrors 4b before film formation made of aluminum having a circumscribed cylinder diameter of 40 mm and six reflecting surfaces forming regular hexagonal columns are passed through the shaft as shown in FIG. 2.9% amorphous fluororesin (trade name: Cytop CTL-802: manufactured by Asahi Glass Co., Ltd.) solution (solvent is a substance represented by structural formula (3) (trade name: CT-solv. 180: manufactured by Asahi Glass Co., Ltd.) ) While immersing the reflective surface of the polygon mirror at a depth of 1.2 mm in the solution in the tank filled with), separating the reflective surface from the solution and then rotating at 2000 rpm for 120 seconds to form a thin film, Firing was performed at 170 ° C. for 30 minutes. An amorphous fluororesin film having a thickness of about 100 nm was uniformly formed on the reflecting surface, and the change in reflectance at an incident angle of 15 to 56 ° was within 1.0%.

  Further, the results of the condensation durability test and the ozone durability test on the polygon mirror thus obtained indicate that the amorphous fluororesin film is a film having excellent moisture resistance and ozone resistance.

  In the condensation durability test, the polygon mirror on which the amorphous fluororesin was formed was left in a furnace at 60 ° C. and 90% for 10 hours, and this was repeated three times. When the change in reflectivity before and after each test was observed, it can be said that the decrease in reflectivity is 2.0% or less even after the third test and there is almost no change in reflectivity. In the ozone durability test, the polygon mirror formed with the amorphous fluororesin was left for 100 hours in an environment of 45 ° C. and 95% and ozone concentration of 1 ppm, and the reflectance before and after the experiment was measured. No decrease in reflectivity was observed.

  In other words, even after repeated dew condensation tests, the reflectance decreased to 2.0% or less, and no change was observed in the ozone durability test. Therefore, the amorphous fluororesin is resistant to moisture and ozone. It is very effective as a coating film on the reflective surface of a polygon mirror.

Example 3
In this embodiment, when an amorphous fluororesin is applied to a polygon mirror having a circumscribed cylinder diameter of 40 mm and six reflecting surfaces made of aluminum forming a regular hexagonal column, the optimum number of rotations and rotation for forming a uniform film. A method for obtaining time is shown.

  Rotational wet film formation was performed in the same manner as in Example 2 using only the rotation speed and rotation time as parameters.

  FIG. 5 is a photograph of the reflective surface of the polygon mirror when the film is rotated (a) at 1500 rpm and 120 sec and is rotated (a) at 2500 rpm and 120 sec. FIG. 6 is an image diagram supplementing FIG. It is.

  When the rotation time is fixed at 120 sec and rotation film formation is performed in increments of 500 rpm at a rotation speed of 1000 to 3000 rpm, the liquid as shown in FIG. 60 sometimes appeared. At 2500 rpm or higher, a trace ("flow spot trace" 61) in which the liquid as shown in FIG. When rotated at 2000 rpm, the “liquid accumulation trace” was suppressed to 0.5 mm or less, and the “flow stain trace” was not confirmed. Table 2 summarizes the results. In the table, for example, 0/10 indicates that after 10 tests, a liquid pool mark or a flow stain mark was observed.

  Liquid traces seen when rotating at 1000 rpm and 1500 rpm for 120 seconds can be prevented by rotating at 2000 rpm for 10 seconds after rotating for 120 seconds. Further, a flow spot observed when rotating at 2500 rpm and 3000 rpm for 120 seconds can be prevented by rotating at 2500 rpm for 20 seconds, or 3000 rpm for 15 seconds and then rotating at 2000 rpm for 120 seconds.

  Further, when the rotational speed was fixed at 2000 rpm and the rotational film thickness was rotated in 30-sec increments from 30 to 150 sec, the "liquid pool trace" may be confirmed to be 0.5 mm or more at 90 sec or less, and 120 sec or more. Then, it was confirmed to be 0.5 mm or less. The results are summarized in Table 3.

  Liquid traces generated when rotating at 2000 rpm for 30 seconds, 60 seconds, and 90 seconds can be prevented by extending the rotation time. Moreover, after rotating for 30 seconds, 60 seconds, and 90 seconds, it can prevent also by rotating for 15 seconds at 3000 rpm. Considering the cheapest mechanism in terms of device production from this example, when applying a rotating film formation method of amorphous fluororesin to a 6-sided polygon mirror made of aluminum with a circumscribed cylinder diameter of 40 mm, when the rotational speed is fixed It can be said that it is desirable to rotate at 2000 rpm for 120 seconds or more. By performing rotation under the above conditions, it is possible to form a uniform film very stably using an inexpensive apparatus.

Example 4
In this example, only the concentration of the solution was used as a parameter, and the optimum liquid concentration was determined by measuring the angular difference in reflectance as in Example 2.

  FIG. 7 shows the results of measuring the angular difference in reflectivity by applying the rotary wet film formation method with the liquid concentration in the range of 1.5 to 4.0 wt% (the film thicknesses of the prepared films are different from each other). Although the data showed some variation, a rough upward curve was drawn as a rough tendency, and the concentration at which the angle dependence of reflectance was considered to be the smallest was 2.9 to 3.0 wt%.

  In this example, even when the angle dependency is large as in the case where the liquid concentration is 1.5%, the angle dependency can be suppressed by adjusting other manufacturing conditions, for example, the rotation speed.

Example 5
An optical scanning device is constructed by arranging the polygon mirrors of Examples 1 to 3 in a scanner motor and arranging them as shown in FIG. 8 together with a rotatable optical deflector, light source (semiconductor laser), imaging optical system, and scanning lens. did. Furthermore, an electrophotographic apparatus was configured using this optical scanning device. Here, as the electrophotographic apparatus, a means for charging the photoreceptor, an exposure means for exposing the charged photoreceptor to form a latent image, a toner image forming means for forming a toner image by supplying toner to the latent image, An electrophotographic apparatus having a transfer means for transferring the toner image to a transfer material and a cleaning means for removing residues and foreign matter on the surface of the photoreceptor is used, and the optical scanning apparatus is used as the exposure means.

  When this electrophotographic apparatus was used to repeatedly output a pattern image and a photographic image, both the image quality and the durability reached the level using a conventional polygon mirror. That is, the polygon mirror of the present invention satisfies the performance required for the conventional polygon mirror, and there is no problem even if it is used in place of the conventional polygon mirror.

Example 6
In this embodiment, by applying the area where the coating liquid is applied to the polygon mirror only to the area Ri or more from the rotation axis (outside the reflecting surface inscribed cylinder), variation in film thickness and reflectance angle dependence is achieved. It can be suppressed.

  A 6-sided polygon mirror with a reflective surface forming a regular hexagonal column with a circumscribed cylinder radius of 20 mm (inscribed cylinder radius Ri = 17.3 mm) is coated with an amorphous fluororesin by a rotational film forming method, and the film thickness is controlled to rotate. Before entering, the experiment was performed under the conditions shown in Table 4 where R is the distance between the rotating shaft and the coating liquid surface in order to apply the coating liquid to the reflecting surface. The results at that time are shown in Table 5. The number of measurements is 30 for each condition. The coating liquid is a substance (trade name: CT-solv.180: manufactured by Asahi Glass Co., Ltd.) represented by Structural Formula (3) containing 2.7% by mass of an amorphous fluororesin (trade name: Cytop CTL-802: manufactured by Asahi Glass Co., Ltd.). )).

  As a procedure of the coating process, the coating was rotated at 40 rpm and held at a distance shown in Table 4 for 10 seconds.

  The rotation speed and rotation time in the coating film forming step were set to 120 seconds at 2000 rpm.

  The conditions for firing the coating film were 40 minutes in a 180 ° C. heating furnace.

  It can be said that the conditions A and B have smaller variations in reflectance than the conditions C and D at the incident angles of 15 °, 35 °, and 56 ° with the reflecting surface inscribed cylinder radius Ri (= 17.3 mm) as a boundary. In other words, since the variation in reflectance is nothing but the variation in film thickness, it can be understood that the variation in film thickness can be suppressed when the application region is limited to the outside of the inscribed cylinder. In addition, when comparing with “PP” that represents the difference between the maximum value and the minimum value among the reflectances at incident angles of 15 °, 35 °, and 56 °, the conditions A and B are half more uneven than the conditions C and D. It can be said that That is, when the application region is limited to the outside of the reflecting surface inscribed cylinder, it is preferable that variation in reflectance angle dependency is suppressed.

  In addition, the variation in reflectance and the variation in film thickness that occur under conditions C and D can be prevented by starting rotation after removing the solution applied to the inside of the reflection surface inscribed circle. When considering a simple apparatus configuration, it is desirable to apply the solution only to the outer side of the inscribed circle on the reflecting surface, rather than using the solution removing means as described above.

Example 7
In the present embodiment, it is shown that accidental film disturbance can be suppressed by applying the application area to the polygon mirror only to an area of Ri or more from the rotation axis (outside the reflecting surface inscribed cylinder).

A SiO ₂ solkel film was applied to a four-sided polygon mirror having a radius of 10 mm on the circumscribed cylinder and a reflecting surface forming a regular quadrangular prism by a rotary wet film forming method, and a liquid as shown in FIG. The occurrence rates of “flow spots” 61, which are traces, or “liquid pools” 60, which are traces of liquid remaining in the region of 0.3 mm from the end of the reflection surface, were compared. The coating solution is isopropyl alcohol containing 2% by mass of ethyl silicate. The experimental conditions were as shown in Table 6. The number of measurements is 120 for each condition.

  As a procedure of the coating process, the coating was rotated at a distance of Table 6 at 40 rpm for 10 seconds.

  The rotation speed and rotation time in the coating film forming step were set to 120 seconds at 2000 rpm.

  The conditions for firing the coating film were 40 minutes in a 180 ° C. heating furnace.

  As can be seen from Table 6, when the application region is only outside the reflecting surface inscribed cylinder (Conditions A and B), compared to the case where the application region exists up to the inside of the reflecting surface inscribed cylinder (Conditions C and D), It can be seen that the occurrence rate is low for both “flow spots” and “liquid pool”. That is, it is preferable that accidental disturbance of the film shape is suppressed by limiting the application region to the outside of the reflecting surface inscribed cylinder.

  In addition, flow spots, liquid pools, and the like that frequently occur under conditions C and D can be suppressed to 1.5% or less if rotation is started after removing the solution applied to the inner surface of the reflecting surface inscribed circle. However, when considering a cheaper and simpler device configuration, it is desirable to apply the solution only on the outer side of the inscribed circle on the reflecting surface, rather than using the solution removing means as described above.

Example 8
In the present embodiment, a most preferable example of a method of applying a coating solution to a reflecting surface before entering a rotation for controlling the film thickness in the rotary wet film forming method will be described.

  In a 6-sided polygon mirror with a circumscribed cylindrical radius of 20 mm and a reflective surface forming a regular hexagonal column, the rotational speed is 40 rpm, the distance R between the rotation axis and the coating liquid surface is a parameter, and the coating time until coating on the entire reflective surface is performed. saw.

  The procedure is shown in FIG. In FIG. 10, a four-sided polygon mirror is shown for simplicity. First, the polygon mirror to be formed is set on the coating solution so that Ri <R <Ro, and here the polygon mirror is not in contact with the coating solution. Next, when the polygon mirror is rotated, the liquid is applied to the corners of the polygon mirror (part indicated by 10 in the figure). Further, this liquid is wet and spread by the rotation, and finally the coating liquid is applied to the entire reflecting surface 4a. The coating solution is an amorphous fluororesin (trade name: CYTOP CTL-802: manufactured by Asahi Glass Co., Ltd.) (structural formula (1)) containing 2.0% by mass of a substance (trade name: CT- solv.180: manufactured by Asahi Glass Co., Ltd.)).

  From the results shown in Table 7, it can be seen that the coating liquid is completely applied and spreads on the reflective surface even if the reflective surface is not completely immersed in the coating liquid surface.

  Next, Table 8 shows the results of application in the same manner as described above, with the application time being 5 seconds, the distance between the rotation axis and the application liquid surface being fixed at 18.0 and 19.0 mm, and the rotation speed being a parameter. In the table, ◯ indicates that the coating solution wets and spreads well over the entire reflecting surface, Δ indicates that the coating spreads in 5 to 20 seconds, and x indicates that the coating does not spread within 20 seconds. As can be seen from this table, it was confirmed that the coating spreads at 300 rpm or less at R = 18.0 mm, and the coating spreads at 160 rpm or less at R = 19.0 mm. Even when R = 18.0 mm, when the rotational speed exceeds 300 rpm, it was confirmed that the coating liquid surface was violently swirled and the desired amount could not be applied. Under this experimental condition, the rotational speed should be 200 rpm or less. It can be said that it is reasonable.

Example 9
In this embodiment, typical examples that can be considered in the method of applying the coating liquid to the reflective surface before entering the rotation for controlling the film thickness in the rotary wet film forming method are shown below, and the coating situation is shown in Table 9. It was. The polygon mirror is a circumscribed cylinder radius of 10.0 mm, a four-sided polygon mirror (inscribed cylinder radius of 7.1 mm) whose reflecting surface is a regular quadrangular prism, and the coating solution is amorphous fluorine resin (trade name: Cytop CTL-802). : Asahi Glass Co., Ltd.) is a substance represented by Structural Formula (3) containing 2.0% by mass (trade name: CT-solv.180: Asahi Glass Co., Ltd.). The number of tests is 10 for each.

  Application Example I was the method described in Example 7, and the rotation speed was 40 rpm, the application time was 5 sec, and the distance R between the rotation axis and the coating liquid surface was 8.0 mm.

  In the application example II, as schematically shown in FIG. 11, first, the reflective surface is immersed in parallel with the coating liquid surface and the reflective surface is in contact with the coating liquid surface. It is conceivable that the reflecting surface is once leveled and then brought into contact with the coating liquid surface, but here, the polygon mirror is rotated at a constant rotation so that the applied liquid does not spread to the area inside the reflecting surface inscribed cylinder ( 30 rpm), the coating liquid level was raised at the timing when the reflecting surface became horizontal, and the reflecting surface was brought into contact with the coating liquid surface for coating.

  In Application Example III, as schematically shown in FIG. 12, the medium 6 sufficiently containing the coating liquid is sequentially pressed against the reflective surface to apply the coating liquid only to the reflective surface. Here, a foamed sponge (a white wiper manufactured by Bridgestone) having sufficient softness so that the medium sufficiently contains the coating liquid and does not damage the reflecting surface was used.

  In Application Example IV, as schematically shown in FIG. 13, the coating liquid was applied to the reflective surface by spraying the coating liquid from the nozzle 7 onto the reflective surface. Here, the flow rate of the jet was 10 ml / sec, the diameter of the blowout cross section was 1 mm, the blowout direction was set at 70 ° in elevation, and the horigon mirror was rotated at 10 rpm.

  Application Example V was the same application method as Application Example I except that, as shown in FIG. 14, the distance between the rotating shaft and the application liquid surface was 6.0.

  Coating is performed by the above method, a coating film forming step is performed at a rotation speed of 2000 rpm, a rotation time of 120 seconds, and a film is formed by baking at 180 ° C. The incident angles are 15 °, 35 °, 56 as in Example 6. Table 9 shows the result of observing the flow spot by obtaining “PP” representing the difference between the maximum value and the minimum value in the reflectance of ° and calculating the standard deviation thereof (PP variation).

  As can be seen from Table 9, if the application area is other than the application example V where the application area exists until the reflection surface inscribed cylinder is turned inward, the application area is outside the reflection surface inscribed cylinder. It was confirmed that both the disturbance of the film thickness can be suppressed very well, which is preferable.

Example 10
In this example, it is shown that the angle uniformity of reflectance can be obtained by providing a film thickness distribution with respect to a wide range of p-polarized light incident angles.

FIG. 15 is a diagram showing a case where a uniform film of SiO ₂ is formed on an aluminum base material as an example showing the relationship between the film thickness, the incident angle, and the reflectance when a uniform film thickness is formed. It is confirmed that there are incident angles and Brewster angles that exhibit a constant reflectance regardless of the film thickness. At this time, it can be said that the reflectivity decreases as the film thickness increases on the narrower angle side than the Brewster angle, and conversely, the reflectivity increases as the film thickness increases on the wide angle side than the Brewster angle.

FIG. 16A) shows the film thickness distribution when a SiO ₂ film is formed on the reflective surface of the aluminum base. Since the position on the reflection surface of the polygon mirror and the incident angle of light have a one-to-one relationship, the horizontal axis represents the corresponding incident angle. This film thickness distribution was determined as follows. That is, the film thickness at which the reflectivity (78.8%) at the Brewster angle (55 °) was obtained at each reflection surface position corresponding to an incident angle of 10 to 70 ° was calculated.

   FIG. 16A) shows the reflectance when this film thickness distribution is obtained. From this figure, it is confirmed that the reflectance is constant with respect to the incident angle when the film thickness distribution is formed.

  Table 10 shows the incidence of TiO2, Al2O3, SiO2 and amorphous fluororesin (trade name: CYTOP CTL-802: manufactured by Asahi Glass Co., Ltd.) formed on the aluminum substrate by dipping with a uniform film thickness. The reflectance at an angle of 10 to 70 ° is shown. B. A. Is the Brewster angle. It can be seen that the reflectance is relatively uniform on the narrower side than the Brewster angle for each film, but the reflectance changes abruptly on the wide angle side of the Brewster angle.

  Table 11 shows the results of measuring the reflectance at that time by forming various kinds of films with a single layer on the aluminum base material with dipping and having a film thickness distribution. At this time, a film thickness showing the same reflectance as that of the Brewster angle was calculated, and the film was formed by controlling the pulling speed so that the film thickness was formed at each position on the reflecting surface. As can be seen from Table 11, it was confirmed that the reflectance was uniform without depending on the angle by providing the film thickness distribution.

  As can be seen from Table 10 and Table 11, when the incident angle range of the P-polarized light is wide, it was confirmed that the angle uniformity of the reflectance can be obtained by providing the film thickness distribution as described above.

  The reflectivity of the Brewster angle does not depend on the film thickness of the surface layer formed on the reflection surface, and indicates the reflectivity up to the lower layer. That is, the reflectance of the base material when the number of layers is 1, and the remaining layers excluding the surface layer when the number of layers is plural. Therefore, regardless of the material of the lower layer and the number of layers, the angular uniformity of the reflectance can be realized by forming the film thickness distribution as described above as in Table 11.

Example 11
In this embodiment, it is shown that the angle uniformity of the reflectance can be obtained by reducing the film thickness of the region where the P-polarized light is incident at a wider angle than the Brewster angle with respect to the film formed on the reflecting surface.

  Table 12 shows that when various films are formed on a polygon mirror made of an aluminum base material, the narrow angle side from the Brewster angle is set to a uniform film thickness and the wide film side from the Brewster angle is formed slightly thinner than the uniform film thickness. The reflectance is shown. The method of determining the film thickness on the wide angle side from the Brewster angle is a film thickness that provides the reflectance at the Brewster angle. Here, the film thickness is such that the reflectance at the Brewster angle can be obtained at an incident angle of 70 °.

  At this time, it was confirmed that the angle uniformity of the reflectivity was obtained more than the case of Table 10 (overall uniform film thickness).

Example 12
In this embodiment, the optical film formed on the reflecting surface is provided with a uniform thickness, and the reflectance angle uniformity is obtained.

  Table 13 shows the reflectance when a uniform slope is provided in the film thickness distribution when various films are formed on the polygon mirror of the aluminum base. The method of determining the slope is to find a slope that minimizes the change in reflectance according to each film material. For example, the film thickness gradient of the amorphous fluororesin is 40% (when the thinnest part of the film is 1, the thickest part is 1.4).

  At this time, it was confirmed that the angle uniformity of the reflectance was obtained as compared with the case of the uniform film thickness shown in Table 10.

Example 13
In the same manner as in Example 5, an optical scanning device and further an electrophotographic apparatus were configured using the polygon mirrors of Examples 10 to 12, and evaluated. Both image quality and durability have reached the level using conventional polygon mirrors.

1 Light source 2 Collator lens 4 Optical deflector 4a Reflecting surface 4b Polygon mirror (before film formation)
5 Coating solution 6 Medium containing coating solution (foam sponge)
7 Coating liquid spray nozzle 10 Reflective surface portion 60 coated with coating liquid Pool 61 Liquid stain 82 Rotating shaft 83 Cylindrical lens 85 Motor 86 Rotating direction 87 Scanning lens 89 Scanned surface 90 Scanning direction

Claims (6)

  A polygon mirror having a plurality of reflection surfaces for reflecting light, wherein the polygon mirror has a film having a film thickness distribution on the reflection surface.   The polygon mirror according to claim 1, wherein the film thickness distribution is a film thickness at which a reflectance at a Brewster angle is obtained at a position corresponding to an incident angle of 10 to 70 °.   The film thickness distribution is uniform at a position corresponding to an incident angle equal to or smaller than the Brewster angle, and a film thickness at which a reflectance at the Brewster angle is obtained at a position corresponding to an incident angle exceeding the Brewster angle. The polygon mirror according to claim 1.   2. The polygon mirror according to claim 1, wherein the film thickness distribution is inclined so as to be uniformly thin from a position corresponding to an incident angle of 10 ° to 70 °.   A light source, an imaging optical system that focuses and collects light emitted from the light source, an optical deflector that reflects and deflects the imaged light, and a scanning lens that guides the deflected light to the surface to be scanned An optical scanning device comprising: the optical deflector comprising the polygon mirror according to claim 1. Means for charging the photosensitive member, exposure means for exposing the charged photosensitive member to form a latent image, toner image forming means for supplying toner to the latent image to form a toner image, and transferring the toner image to a transfer material In an electrophotographic apparatus having a transfer means for cleaning, and a cleaning means for removing residues and foreign matters on the surface of the photoreceptor,
An electrophotographic apparatus comprising the optical scanning device according to claim 5 as the exposure means.

Images