JPH1010847A - Color image forming device and manufacture thereof adopting plural led array heads for use as recording means - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an image quality of the color electro-photographic image, and to simplify the color image forming device constitution by effectively adopting even a LED array chip provided with a light generating cell whose light emission brightness flactuation is relatively large. SOLUTION: In this device, LED array writer heads 117a, 117b, 117c and 117d severally forming latent image on photoreceptor 101a, 101b, 101c and 101d corresponding to cyan, magenta, yellow and black, is severally provided with plural light generating cell, and forms respective image of cyan, magenta, yellow and black on a paper sheet 106 by performing electrification, exposure, development and transfer with use of photoreceptors 101a to 101d. As the LED array writer head 117c for the yellow image forming, a product whose emission brightness fluctuation of the light generating cell is larger than the respective LED array writer head 117a, 117b or 117d for cyan, magenta or black image forming.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming technique using recording means including an LED array head, and more particularly, to a full-color image forming apparatus by electrophotography using a plurality of the LED array heads. And a method for manufacturing the image forming apparatus. The full-color image forming apparatus according to the present invention can be applied to, for example, a color printer or a color copying machine.

[0002]

2. Description of the Related Art
When forming an image by electrophotography using an LED array head in which a plurality of LED array chips are arranged, in order to improve the quality of the formed image, for each light emitting cell in each LED array chip, The variation of the light emission luminance of each light emitting cell is corrected. For this reason, after the LED array chip is manufactured, the driving means for the LED array chip corrects the light emission pulse width or the driving current for each light emitting cell for each individual cell, thereby making the exposure amount uniform.

When the above-described electrophotographic image forming technique is applied to full-color image forming, the above-described LE is required.
It is necessary to form a plurality of primary color images using a plurality of D array heads (for example, a cyan image, a magenta image, a yellow image, and a black image as four primary color images for full color image formation).

However, in the LED array head, compensating the variation in the light emission luminance of each light emitting cell has a problem that the structure of the driving means is complicated and the apparatus cost is high. This difficulty is particularly remarkable in the case of full-color image formation.

On the other hand, in recent years, variation in light emission luminance of each light emitting cell of an LED array chip has been gradually improved due to improvements in an LED manufacturing process, an LED manufacturing apparatus, and a semiconductor film material as a material. It has become to.

However, it has not yet been improved to such an extent that a satisfactory full-color image can be formed by using the manufactured LED array chip unconditionally for forming all primary colors. Therefore, the light emission luminance variation of the light emitting cell is, for example, 5%.
A desired image quality is obtained by selectively adopting only the LED array chips within the range.

Accordingly, one object of the present invention is to reduce the variation in light emission luminance in the driving means of a plurality of LED array heads used in a color image forming apparatus and to reduce the image quality required for a color image by electrophotography. An object of the present invention is to provide a means for improving the image quality and simplify the apparatus configuration in color image formation.

Another object of the present invention is to improve the image quality required for a color image by effectively utilizing an LED array chip having a relatively large variation in light emission luminance of a light emitting cell.

[0009]

According to the present invention, there is provided an image forming apparatus for forming a full-color image by an electrophotographic process, wherein the four primary colors cyan and magenta for forming an image are provided. , Four LED array writer heads are used as optical recording means for exposing and recording a latent image on each of the four photoconductors corresponding to yellow and black, and the LED array writer head is A plurality of light emitting cells are provided, and using each of the photoconductors, a cyan image, a magenta image, a yellow image, and a black image are formed on the image forming medium by performing processes of charging, exposure, development, and transfer. In an image forming apparatus for forming a full-color image on an image forming medium, (1) an LED for forming the yellow image
A color image forming apparatus using an array writer head having a larger variation in light emission luminance of the light emitting cells than the LED array writer head for forming the cyan, magenta and black images, (2) the yellow, LE for cyan and magenta image formation
A color image forming apparatus using a D array writer head having a larger variation in light emission luminance of a light emitting cell than the LED array writer head for forming the black image; and (3) the cyan and magenta images. As the LED array writer head for forming, an LED array writer head having a larger variation in light emission luminance of the light emitting cells than the LED array writer head for forming the black image is used, and the LED for forming the yellow image is used.
A color image forming apparatus is provided, which uses an array writer head having a larger variation in light emission luminance of light emitting cells than the LED array writer head for forming the cyan and magenta images.

In one embodiment of the present invention, the variation in the light emission luminance of the light emitting cells of the LED array writer head for forming the yellow image is in the range of more than 5% and 10% or less of the average light emission luminance. The variation in the light emission luminance of the light emitting cells of the LED array writer head for forming magenta and black images is within 5% of the average light emission luminance.

In one embodiment of the present invention, the variation in the light emission luminance of the light emitting cells of the LED array writer head for forming the yellow, cyan and magenta images is within a range exceeding 5% of the average light emission luminance and not more than 10%. The variation in light emission luminance of the light emitting cells of the LED array writer head for forming the black image is 5% of the average light emission luminance.
Within the following range.

In one embodiment of the present invention, the variation in the light emission luminance of the light emitting cells of the LED array writer head for forming the yellow image is in the range of more than 8% to 10% or less of the average light emission luminance. Also, the variation in the light emission luminance of the light emitting cells of the LED array writer head for magenta image formation exceeds 5% of the average light emission luminance and is 8%.
%, And the variation in the light emission luminance of the light emitting cells of the LED array writer head for forming the black image is within 5% of the average light emission luminance.

In one embodiment of the present invention, the LED array writer head includes a plurality of LED chips having a plurality of light emitting cells arranged so that the plurality of light emitting cells are arranged one-dimensionally.

Further, according to the present invention, there is provided an image forming apparatus for forming a full-color image by an electrophotographic process, wherein the four primary colors cyan, magenta, yellow and black are formed. In response to the above, four LED array writer heads are used as optical recording means for exposing and recording a latent image on each of four photoconductors as image carriers, and the LED array writer head includes a plurality of light emitting cells. And forming a cyan image, a magenta image, a yellow image, and a black image on an image forming medium by performing charging, exposing, developing, and transferring processes using each of the photoconductors. (1) (a) a method of manufacturing an image forming apparatus for forming a full-color image on the LED array writer head; Measuring the variation of the light emission luminance of the light emitting cells of each LED array for each of the large number of LED arrays; (C) LE for forming the yellow image
2nd rank LED as D array writer head
A method of manufacturing a color image forming apparatus, wherein an array is selectively adopted and the first rank LED array is selectively adopted as an LED array writer head for forming the cyan, magenta and black images, [2] (A) measuring the light emission luminance variation of the light emitting cells of each LED array for each of a large number of LED arrays to constitute the LED array writer head; and (b) measuring the light emission luminance variation of each LED array based on the measurement result. Ranking a first rank having a small size and a second rank having a large variation in the emission luminance,
(C) selecting and adopting the second rank LED array as the LED array writer head for the yellow, cyan and magenta image formation, and the first rank LED array as the LED array writer head for the black image formation And [3] (a) the emission luminance of the light emitting cells of each LED array for each of a large number of LED arrays that constitute the LED array writer head. Measuring the variation, and (b) setting each LED array based on the measurement result to a first rank having a small magnitude of the light emission luminance variation, a second rank having a medium magnitude of the light emission luminance variation, and a second rank having a medium magnitude of the light emission luminance variation. Rank the third rank with the larger size,
(C) the third rank LED array is selectively adopted as the LED array writer head for the yellow image formation, and the LE for the cyan and magenta image formation.
2nd rank LED as D array writer head
An array is selected and adopted, and L for forming the black image is formed.
LE of the first rank as an ED array writer head
A method for manufacturing a color image forming apparatus, wherein a method for selectively adopting a D array is provided.

In one embodiment of the present invention, the first rank has a variation in emission luminance within 5% or less of the average emission luminance, and the second rank has a variation in emission luminance exceeding 5% of the average emission luminance. And it is within the range of 10% or less.

In one aspect of the present invention, the first rank has a variation in emission luminance within 5% or less of the average emission luminance, and the second rank has a variation in emission luminance exceeding 5% of the average emission luminance. In the third rank, the variation in the light emission luminance is more than 8% and not more than 10% of the average light emission luminance in the third rank.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of an electrophotographic printer using an LED array chip, which is an image forming apparatus according to the present invention, as recording means.

In the main body of the apparatus shown in FIG. 1, four image (latent image) forming sections, that is, image forming sections Pa, Pb, Pc and Pd are arranged in order from the upstream side (right side in FIG. 1). I have. These image forming units form images of four different colors (cyan, magenta, yellow and black) by respective processes of charging, exposure, development and transfer. The image forming units Pa, Pb, Pc and Pd are provided with electrophotographic photosensitive drums (hereinafter simply referred to as photosensitive drums) 101a, 101b, 101c and 1 as dedicated image carriers, respectively.
01d is provided, and the image forming paper (image forming medium) in which the toner images formed on the photosensitive drums are carried and conveyed by the paper carrier 108 moving adjacent to each image forming unit. The image forming paper 106 transferred onto the toner image 106 and further onto the toner image
After the toner image is fixed by heating and pressurizing the toner image, the toner image is discharged to the apparatus main body. While rotating the photosensitive drums 101a, 101b, 101c and 101d clockwise in FIG. 1, a process for each photosensitive drum is executed.

Next, a description will be given in order from the image forming section. The photosensitive drums 101a, 101b, and 1 are rotatably disposed.
Exposure lamps 12 are provided around and above 01c and 101d.
1a, 121b, 121c and 121d, charger 102
a, 102b, 102c and 102d, LED array writer heads 117a, 117b for exposing image information,
117c and 117d, potential sensors 122a and 122
b, 122c and 122d are provided. First, the photosensitive drums 101a, 101b, 101c and 101 are charged by the chargers 102a, 102b, 102c and 102d.
d is uniformly charged. LED array writer head 1
Irradiation is performed by 17a, 117b, 117c, and 117d to form a latent image on each photosensitive drum according to an image signal.

The developing units 103a, 103b, 103c and 103d are filled with a predetermined amount of developer (toner) of each color of cyan, magenta, yellow and black by a supply device (not shown). The developer is supplied onto the photosensitive drums 101a, 101b, 101c and 101d, and forms a visible image (toner image) corresponding to the latent image formed by the exposure.

Image forming paper 10 to which a toner image is transferred
Reference numeral 6 is accommodated in a paper cassette 160 and is supplied onto a belt-shaped paper carrier 108 via a paper feed roller 113a and a registration roller 113b. The sheet is conveyed to the positions 101b, 101c and 101d. Here, the paper carrier 10
Numeral 8 is a sheet made of a dielectric resin sheet such as a PET sheet, a polyvinylidene fluoride resin sheet, or a polyurethane resin sheet. Both ends are overlapped and joined together to form an endless shape. (Seamless) belt is used (in the case of a belt having a seam, there is a case where a means for detecting a seam position is provided and a toner image is not transferred on the seam in some cases) . Paper carrier 108
Is wound around rollers 111 and 111 on the upstream side and a roller 110 on the downstream side. When the paper carrier 108 starts rotating, the image forming paper 106
3b is conveyed onto the paper carrier 108. At this time, the image writing signal is turned ON, and an image is formed on the most upstream photosensitive drum 101a at a certain timing. And
In the lower part of the photosensitive drum 101a, the image forming paper 106 is pressed against the photosensitive drum 101a under a uniform pressure condition by a transfer pressing member 141a using a mylar, and an electric field is applied by a transfer charger 104a.
a is the image forming sheet 1
06. The image forming paper 106 is held on a paper carrier 108 by an electrostatic attraction force.
The sheet is conveyed to the next image forming section Pb, and a magenta toner image is transferred by the photosensitive drum 101b in the same manner as described above. Hereinafter, the photosensitive drum 1 is formed in the same manner as described above.
01c and 101d transfer yellow and black toner images, respectively. These four colors (cyan,
The magenta, yellow, and black images are formed with a predetermined positional relationship with respect to the image forming sheet 106 for forming a predetermined full-color image. 14
1b, 141c and 141d are transfer pressing members,
04b, 104c and 104d are transfer chargers.

The image forming paper 106 onto which the four color toner images have been transferred is neutralized by a separation charger 114 and a peeling charger 115, and the paper carrier 10 is attenuated by the attenuation of the electrostatic attraction force.
8 and is transported to the fixing unit 107.

The fixing section 107 includes a fixing roller 171, a pressure roller 172, heat-resistant cleaning members 173 and 174 for cleaning these rollers,
Heaters 175 and 176 for heating 1 and 172, an oil application roller 177 for applying a release agent oil such as dimethyl silicon to the fixing roller 171, and a thermistor 179 for controlling the fixing temperature are provided. The image forming paper 106 conveyed from the paper carrier 108 to the fixing unit 107 is heated and pressed here so that the toner image is fixed on the surface of the image forming paper 106 to form the predetermined full-color image.
The image forming paper 106 on which the toner image has been fixed and the full-color image has been formed is then discharged outside the apparatus (outside the apparatus body).

Each of the photosensitive drums 101a, 101b, 101c and 101d after the transfer, that is, when the toner image is gone.
Indicates that the developer remaining on the surface
5a, 105b, 105c and 105d remove and prepare for the subsequent latent image formation. The developer remaining on the paper carrier 108 is neutralized by the belt static eliminator 112 to remove the electrostatic attraction force, and is then scraped into the collection chamber 109 by the rotatable fur brush 116. As another means for removing the developer, a blade or a nonwoven fabric and a combination thereof are also used.

As described above, in an electrophotographic image forming apparatus including four image forming units each having a photosensitive drum and an LED array writer head, the LED array writer head in each of the four image forming units has its LE
It is characterized by the magnitude of the D emission luminance variation. Each LED array writer head 117a, 117b, 11
As an example of the characteristic combination of the emission luminance variations of 7c and 117d, those shown in Table 1 below are exemplified.

[0027]

[Table 1] Here, the emission luminance variation is represented by a ratio of a difference between the minimum emission luminance value and the maximum emission luminance value in the same LED array writer head to the average emission luminance value. In addition, the same LED
In the array writer head, the driving means of each array chip is adjusted so that the average light emission luminance value of each of all the array chips becomes the same.

When an image was formed using the apparatuses of Examples 1 to 3 as described above, the following results were obtained.

Example 1 shows the LED of the image forming section of all colors.
It was confirmed that the quality was as good as that of an image formed when an array writer head having an emission luminance variation of 5% or less was used as the array writer head.

In Examples 2 and 3, slight unevenness of color was generated, but as streak-like unevenness, the unevenness was inconspicuous, and it was confirmed that the quality was practically acceptable. In addition, although Example 3 is included in the range of Example 2, it was recognized that the image quality of Example 2 in the range of Example 3 was better than that of Example 2 out of the range of Example 3.

The image forming apparatus of the above embodiment can be manufactured, for example, as follows.

(A) A large number of LED arrays are manufactured in advance to constitute an LED array writer head, and the emission luminance variation of the light emitting cells is measured for each of them (light emission luminance variation measuring step), (b) next,
Based on the measurement result in the emission luminance variation measurement step,
(C) ranking each LED array into a plurality of ranks classified according to the magnitude of the variation in light emission luminance; and (c) as the LED array writer head for forming the primary color images, (Selection and adoption step).

The above ranking and selective adoption can be performed, for example, as shown in Table 1 above. As long as the variation in light emission luminance is 5% or less, there is no particular problem as an LED array writer head. In the manufacture of LED arrays, the variation in light emission luminance is about 15% at the maximum. In the above embodiment, the light emission luminance variation of more than 10% is not adopted, and those of 10% or less are ranked. It is used in a specific combination.

It is considered that the object of the present invention is achieved by adopting the above-described combinations based on the magnitude of the variation in the light emission luminance of the LED array writer head due to the human visual characteristics with respect to the image quality. That is, among the four primary colors, the luminosity factor for black is the highest, the luminosity factor for yellow is the lowest, and the luminosity factor for cyan and magenta is considered to be based on the middle between the former two. In the above-described embodiment, the LED that can be used without deteriorating the image quality required for a color image is provided by giving the tolerance of the variation in the emission luminance in response to such visual characteristics.
The range of the array is expanded, and the yield is improved and the cost is reduced.

[0035]

As described above, according to the present invention,
In manufacturing the image forming apparatus, the LED array chips are selected according to the rank of the light emission luminance variation, and an LED array writer head having a small light emission luminance variation (for example, 5% or less) reproduces and forms a full-color image. The primary colors cyan, magenta, yellow and black are used for black, and those having large variation in light emission luminance (for example, those having a luminance of 5% or more and 10% or less or 8% or more and 10% or less) are used for yellow. In magenta, by using the above-mentioned or the above-mentioned small or one having an intermediate between them, an image forming apparatus which hardly deteriorates in image quality and does not interfere with actual use was manufactured. Reduce the percentage of LED array chips that have not been adopted
The present invention can be realized without effectively using an array chip and without making a defective LED array writer head. Thus, the above objects are achieved by the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an electrophotographic printer using an LED array chip as a recording unit, which is an image forming apparatus according to the present invention.

[Explanation of symbols]

101a, 101b, 101c, 101d Photosensitive drums 102a, 102b, 102c, 102d Chargers 103a, 103b, 103c, 103d Developing devices 104a, 104b, 104c, 104d Transfer chargers 105a, 105b, 105c, 105d Cleaning unit 106 Image forming paper 107 Fixing Unit 108 Paper Carrier 109 Toner Collection Chamber 110 Driving Roller 111 Roller 112 Belt Static eliminator 113a Feed Roller 113b Registration Roller 114 Separation Charger 115 Peeling Charger 116 Fur Brush 117a, 117b, 117c, 117d LED Array Writer Head 121a , 121b, 121c, 121d Pre-exposure lamps 122a, 122b, 122c, 122d Potential sensors 141a, 141b, 141c, 141d The pressing member 160 paper cassette 171 fixing roller 172 pressure roller 173 and 174, the cleaning member 175, 176 heater 177 oil applying roller 179 thermistor

Claims (12)

[Claims] 1. An image forming apparatus for forming a full-color image by an electrophotographic process, comprising four image carriers corresponding to four primary colors cyan, magenta, yellow, and black for image formation. The four LED array writer heads are used as optical recording means for exposing and recording a latent image on each of the LED arrays. The LED array writer head includes a plurality of light emitting cells, and is charged by using each of the photoconductors. In an image forming apparatus that performs a process of exposure, development and transfer to form a cyan image, a magenta image, a yellow image and a black image on an image forming medium to form a full-color image on the image forming medium,
A color image forming method comprising: using an LED array writer head for forming the yellow image having a larger variation in light emission luminance of light emitting cells than the LED array writer head for forming the cyan, magenta and black images. apparatus. 2. An image forming apparatus for forming a full-color image by an electrophotographic process, comprising four image carriers corresponding to four primary colors cyan, magenta, yellow and black for image formation. The four LED array writer heads are used as optical recording means for exposing and recording a latent image on each of the LED arrays. The LED array writer head includes a plurality of light emitting cells, and is charged by using each of the photoconductors. In an image forming apparatus that performs a process of exposure, development and transfer to form a cyan image, a magenta image, a yellow image and a black image on an image forming medium to form a full-color image on the image forming medium,
L for forming the yellow, cyan and magenta images
A color image forming apparatus comprising: an ED array writer head having a larger variation in light emission luminance of light emitting cells than an LED array writer head for forming a black image. 3. An image forming apparatus for forming a full-color image by an electrophotographic process, comprising four image carriers corresponding to four primary colors cyan, magenta, yellow and black for image formation. The four LED array writer heads are used as optical recording means for exposing and recording a latent image on each of the LED arrays. The LED array writer head includes a plurality of light emitting cells, and is charged by using each of the photoconductors. In an image forming apparatus that performs a process of exposure, development and transfer to form a cyan image, a magenta image, a yellow image and a black image on an image forming medium to form a full-color image on the image forming medium,
The LED array writer head for forming the cyan and magenta images has the L
A light emitting cell having a larger variation in light emission luminance than the ED array writer head is used, and as the LED array writer head for the yellow image formation, the light emission cells are more luminous than the LED array writer head for the cyan and magenta image formation. A color image forming apparatus using a device having a large variation in light emission luminance. 4. The variation in light emission luminance of the light emitting cells of the LED array writer head for forming the yellow image is more than 5% and not more than 10% of the average light emission luminance, and the cyan, magenta and black image formation is performed. 2. The color image forming apparatus according to claim 1, wherein the variation in the light emission luminance of the light emitting cells of the LED array writer head is within 5% of the average light emission luminance. 5. The variation in the light emission luminance of the light emitting cells of the LED array writer head for forming the yellow, cyan and magenta images exceeds 5% of the average light emission luminance and is 10% or less.
The light emitting cell of the LED array writer head for forming a black image has a light emission luminance variation of 5% or less of an average light emission luminance. Color image forming apparatus. 6. A variation in light emission luminance of the light emitting cells of the LED array writer head for forming the yellow image is more than 8% and not more than 10% of the average light emission luminance, and is used for forming the cyan and magenta images. The variation in the light emission luminance of the light emitting cells of the LED array writer head is more than 5% and not more than 8% of the average light emission luminance,
The variation in the light emission luminance of the light emitting cells of the LED array writer head for forming the black image is 5 times the average light emission luminance.
% Or less.
The color image forming apparatus according to any one of the above. 7. The LED array writer head according to claim 1, wherein an LED chip having a plurality of light emitting cells is arranged such that a plurality of the light emitting cells are arranged one-dimensionally. The color image forming apparatus according to any one of the above. 8. An image forming apparatus for forming a full-color image by an electrophotographic process, wherein four image carriers corresponding to four primary colors cyan, magenta, yellow and black for image formation are provided. The four LED array writer heads are used as optical recording means for exposing and recording a latent image on each of the LED arrays. The LED array writer head includes a plurality of light emitting cells, and is charged by using each of the photoconductors. , An image forming apparatus that forms a cyan image, a magenta image, a yellow image, and a black image on an image forming medium by performing processes of exposure, development, and transfer to form a full-color image on the image forming medium (A) for each of a large number of LED arrays to constitute the LED array writer head, And (b) ranking each LED array into a first rank having a small emission luminance variation and a second rank having a large emission luminance variation based on the measurement result. (C) selecting and adopting the second rank LED array as the LED array writer head for the yellow image formation, and the first rank LED array writer head for the cyan, magenta and black image formation. A method for manufacturing a color image forming apparatus, wherein the LED array is selectively adopted. 9. An image forming apparatus for forming a full-color image by an electrophotographic process, wherein four image carriers corresponding to four primary colors cyan, magenta, yellow and black for image formation are provided. The four LED array writer heads are used as optical recording means for exposing and recording a latent image on each of the LED arrays. The LED array writer head includes a plurality of light emitting cells, and is charged by using each of the photoconductors. , An image forming apparatus that forms a cyan image, a magenta image, a yellow image, and a black image on an image forming medium by performing processes of exposure, development, and transfer to form a full-color image on the image forming medium (A) for each of a large number of LED arrays to constitute the LED array writer head, And (b) ranking each LED array into a first rank having a small emission luminance variation and a second rank having a large emission luminance variation based on the measurement result. (C) selecting and adopting the second rank LED array as the LED array writer head for the yellow, cyan and magenta image formation, and the first rank as the LED array writer head for the black image formation A method for manufacturing a color image forming apparatus, wherein the LED array is selectively adopted. 10. An image forming apparatus for forming a full-color image by an electrophotographic process, wherein four image bearing members corresponding to four primary colors cyan, magenta, yellow and black for image formation are provided. The four LED array writer heads are used as optical recording means for exposing and recording a latent image on each of the LED arrays. The LED array writer head includes a plurality of light emitting cells, and is charged by using each of the photoconductors. , An image forming apparatus that forms a cyan image, a magenta image, a yellow image, and a black image on an image forming medium by performing processes of exposure, development, and transfer to form a full-color image on the image forming medium (A) Each LED array for each of a number of LED arrays to constitute the LED array writer head (B) measuring each of the LED arrays based on the measurement result as a first rank having a small emission luminance variation and a second rank having a moderate emission luminance variation. (C) selecting and adopting the LED array of the third rank as the LED array writer head for forming the yellow image, and selecting the cyan and magenta images. LE for formation
2nd rank LED as D array writer head
An array is selected and adopted, and L for forming the black image is formed.
LE of the first rank as an ED array writer head
A method for manufacturing a color image forming apparatus, wherein a D array is selectively adopted. 11. The first rank has a variation in light emission luminance of 5% or less of the average light emission luminance, and the second rank has a light emission luminance variation of more than 5% and 10% or less of the average light emission luminance. 9. The method of claim 8, wherein
10. The method for producing a color image forming apparatus according to any one of claims 1 to 9. 12. The first rank has a variation in light emission luminance of 5% or less of the average light emission luminance, and the second rank has a light emission luminance variation of more than 5% and 8% or less of the average light emission luminance. The method of manufacturing a color image forming apparatus according to claim 10, wherein the third rank has a variation in light emission luminance within a range of more than 8% and not more than 10% of an average light emission luminance.