JPS61261749A - Formation of color latent image - Google Patents

Abstract

PURPOSE:To obtain a color reproduceable copy erasing the latent image of a black image to obtain a full color copy from an original constituting of black and chromatic colors, forming the latent images of specific color components in a chromatic color image and forming the latent image of the black image independently. CONSTITUTION:To form an electrostatic latent image corresponding to a chromatic color image of an original 1 including black and chromatic color images on a photosensitive body 5 by an electrophotographic method, light enough for the optical fatigue of the photosensitive body 5 is uniformly irradiated to the photosensitive body 5 and then the photosensitive body 5 is electrically charged. In an area of the photosensitive body 5 which corresponds to the part other than a black image part of the original 1, the optical image of the original 1 is exposed to the photosensitive body 5 with the quantity of light required and sufficient for the erase of the optical fatigue and electric charge formed by said respective processes. Electric charge left on the part of the photosensitive body 5 which corresponds to the black image part of the original 1 is destaticized, the photosensitive body 5 is electrically charged to charge the optical fatigue part and the non-fatigue part with different electric potential levels each other and then the optical image of a certain chromatic optical component of the reflected light of the same original is exposed to the same position as said exposure on the photosensitive body 5. Consequently, the black part is reproduced only by black, saving the consumption of toner.

Description

[Detailed description of the invention]! L3! FIELD OF THE INVENTION The present invention relates to a method of forming, on a photoreceptor, an electrostatic latent image corresponding to an image of a certain color component of a chromatic image of an original including black and chromatic images, by electrophotography.

Conventional technology A conventional method for making full-color copies from originals containing black and chromatic images is to sequentially expose the original onto a photoreceptor through three color separation filters: blue, green, and red. A method is known in which the electrostatic latent images are developed with one color each of yellow (Y), magenta (M), and cyan (C) toner, and the images are superimposed and transferred onto the same transfer paper. .

In this case, as shown in Figure 2(a), red (R), green (G)
), blue (B), and black (BL) images, as shown in Figure 2 (b), the red part (R) is Y and M, and the blue part (B) is Y and C1α. :, 5.5. The blue part (B) is M and C, the black part is a combination of Y, M, and C, 1 toner 2 is transferred onto the transfer paper 3 in an overlapping manner, and these colors are expressed as a mixed color. However, black is Y
, M, and C. 1. When expressed by toner color mixture, the spectral transmittance characteristics of B, G, and R color separation filters and Y and M.

Because the spectral reflectance characteristics of toner C are different from ideal characteristics, it is extremely difficult to reproduce a perfect black color, resulting in not only poor color reproducibility but also a large amount of toner consumption, resulting in economical problems. It is also disadvantageous. Therefore, the color separation filter has a neutral density.
74""(ND-z'#")Xli!a71'#
The latent image formed by adding 5 tja and performing exposure 4 times and exposing it through an ND filter or a yellow filter becomes black (
BL) toner is developed, and the toner image developed with Y, M, and C toners is superimposed and transferred. This method improves the reproducibility of the black image, but since the black image cannot be erased independently on the photoreceptor in the normal Carlson process, the black part of the copy is Y, M, C, BL.
The disadvantage that color toners are transferred in an overlapping manner and the amount of toner consumed increases cannot be solved.

In addition, as a method for making two-color copies from two-color originals, such as black and red originals, by using a special photoreceptor and a special process, black images are made using only black toner, and red images are made using red toner. A method of reproducing images using only a single color has been proposed, but the drawback is that the cost is high because the photoreceptor and image-forming process equipment are special, different from those of commonly used monochrome copiers such as black and white. be.

Further, Japanese Patent Publication No. 49-17531 discloses a two-color copying method that utilizes the optical fatigue phenomenon of a photoreceptor. The photofatigue phenomenon is a phenomenon in which when a photoreceptor is irradiated with strong light before being charged with corona, the surface charge of the photosensitive layer due to charging is reduced. In the above method, the photoreceptor is first charged uniformly, and then, for example, black and red originals,..., l# a 3'a ″'
``[l9JL, JU'6-”tah, g**IL”
l'm@? ”'i * n W m L' *
[M' h 'Q b' ”” 7 t M”゛The charge on the remaining parts disappears due to light. Therefore, if development is performed with black toner, black toner will adhere only to the black parts.

The red image corresponding area of the photoreceptor loses a charge of 1, but since the amount of exposure is not large, the charge remains 1 along with the black area.
Since no optical fatigue occurs, when the charging operation is performed again, only the areas corresponding to the black and red images are normally charged, and the other areas are only slightly charged. Therefore, if development is performed with red toner, the red toner will adhere only to the previously adhered black toner and to the red image area, resulting in a black/red copy corresponding to the original. However, with the above method, the latent image of the black image cannot be erased when red toner is developed, so the black and red toners overlap in the black areas on the copy, making it impossible to obtain clear colors and wasting time. It has the disadvantage of being consumed.

, 1 By the way, the above-mentioned optical fatigue phenomenon of the photoconductor is caused by charging. □□A0 from 63.3,
Yu, Ka, O □ This was discovered as a result of experiments conducted by the inventors. The reason for this is not clear, but it is thought to be due to the movement of charges within the photoconductive layer of the photoreceptor.

Purpose The present invention provides full-color copying using conventional electrophotography;
Considering the above-mentioned situation in the case of two-color copying, etc., the black image on the original is erased on the latent image by utilizing optical fatigue and its recovery, and R, G as shown in Figure 1 (a) is used. , B, and BL, the chromatic color image portion is Y, M,
Reproduced by mixing C toners, black images are reproduced only with black toner 4, and for example, in two-color copies of two-color originals such as red and black, black images are reproduced with only black toner, and red images are reproduced with red toner. The purpose of the present invention is to provide a method for forming an electrostatic latent image on a photoreceptor corresponding to a color component image that has only chromatic images of a document containing black and chromatic images. do.

Furthermore, the color latent image forming method of the present invention achieves the following objects: (a) uniformly irradiating the photoreceptor with light at an amount sufficient to optically fatigue the photoreceptor; Step 2: (b) Uniformly charging the photoreceptor; (c) In areas on the photoreceptor corresponding to areas other than the black image area of the document, light fatigue and charging formed in each step are removed. A step of exposing the optical image of the original onto a photoreceptor with a sufficient amount of light to erase it; (d) a step of removing the charge remaining on the part of the photoreceptor corresponding to the black image area of the original; (e) a step of photoreceptor. A photoconductor subjected to original exposure in the process of (c) above, and (f) a step in which the photoreceptor is subjected to a charging operation to charge the photo-fatigue area and the non-fatigue area to different potentials.
The present invention is characterized in that it includes a step of exposing a light image of a certain colored light component of reflected light of the same document to two identical positions.

The method of the present invention will be explained in detail below with reference to the drawings.

(A) to (F) in FIG. 3 respectively show the photoreceptor surface potential and charging state corresponding to steps (A) to (F) of the method of the present invention, which will be explained below. In the figure, 5 is a photoconductive layer of the photoreceptor, 6 is a support layer thereof, 7 is a charger, 8 is a static eliminator, and 9 is a color filter.

(a) Uniform exposure process First, the photoreceptor is uniformly irradiated with light at a sufficient amount of light to cause optical fatigue. As a result, the photoconductive layer 5 of the photoreceptor undergoes optical fatigue. The hatched area in the figure indicates a state of optical fatigue. The amount of light required to optically fatigue the photoreceptor is several to several times energetically higher than the image exposure amount used in normal copying processes. In the normal copying process, the entire surface of the photoreceptor is irradiated with light at the end of the process to erase the history of the photoreceptor and initialize it, but the amount of light is such that it does not cause optical fatigue on the photoreceptor. The amount of light is said to be approximately

(b) Charging process The photoreceptor that has suffered photo fatigue is uniformly charged by a charger 7.

In the example shown, it is charged with (-) polarity.

(c) Image exposure step The original image is exposed onto the photoreceptor. In that case, the amount of light is determined by the photoconductor corresponding to the area other than the black image area in the original image.
In the second region, the amount of light is sufficient to erase the optical fatigue and charge formed in each of the above steps. In the example shown in the figure, original]- is red (R), black (BL), blue (B), green (G
) are arranged sequentially from the left. The image exposure of the original is applied only to the parts corresponding to the chromatic images of R, B, and G, so that the optical fatigue of that part of the photoreceptor is recovered, and
Electrostatic charge is removed.

(d) Static elimination step The charge remaining on the portion of the photoconductor corresponding to the black image that was not exposed in the exposure step of (c) is removed by the charge eliminator 8 with an externally applied charge of opposite polarity. In this case, since charges do not move within the photoconductive layer of the photoreceptor, photofatigue in this portion (hatched portion) is not recovered.

(e) Charging process If the charging operation is performed using the charger 7 in this state, the surface potential will not be as shown in the figure due to the difference in charging characteristics between the photo fatigue area (hatched area in the figure) and the fatigue recovery area. A potential difference shown by 8■ is generated.

(f) Image exposure step Next, the same original is exposed at the same position on the photoreceptor 2 where the original was exposed in step (c). In the illustrated example, a blue filter 9 is inserted in the exposure path for color separation, and the photoreceptor 5 is irradiated with an original light image. The light reflected from the inner door (R) and the green (G) portion of the document is cut by the blue filter 9, and no light is reflected from the black image area, resulting in only the light reflected from the blue portion. reaches the photoreceptor 5. therefore,
The potential difference ΔV formed in the charging process (e) is maintained between the black area, red area, and green area, and by appropriately selecting the developing bias, only the latent image in the red and edge areas is formed. can be developed with yellow toner.

□゛ After copying, the yellow toner image formed through the charge removal and charging steps (d) and (e) is transferred to a transfer paper, and then a green filter is inserted between the exposure tips and image exposure is performed. , the obtained red front latent image is
Developed with zenta toner, superimposed and transferred onto the above transfer paper, then performed steps (d) and (e), and exposed through a red filter to convert the resulting blue and edge latent images into cyan. Develop with toner and transfer to the above transfer paper □′
Overlay and transfer. With the above transcription, red,
The green and blue parts are reproduced using toners of three colors: Y, M, and C.

Next, by performing steps (a), (b), and (c), the latent image in the black area formed on the photoreceptor is developed with black toner, and then transferred onto the same transfer paper in an overlapping manner. The image in the black area is reproduced with only black toner.
You can get a copy of the color.

1・ 11. Incidentally, the development with the black toner may be performed before the development with the color toner, and the image may be transferred onto the transfer paper first.

Further, in the above embodiment, an example was explained in which an original in four colors of R, G, B, and BL is reproduced, but a full-color copy can also be obtained from an original containing mixed intermediate colors by the same process. .

Next, a two-color copy is made from a two-color original with red and black images drawn on a white background.
An embodiment of a method for forming a latent image on a red image portion when copying only a red image in one color will be described with reference to FIG.

The steps in this case are the same in order as the steps explained in FIG. By reducing the difference in the amount and emphasizing the black part, the latent image of the red part obtained by exposing through a cyan filter in the image exposure process of ) is different from the color latent image formation method used when making full-color copies.

In the process of the present invention, the photoconductive layer of the photoreceptor undergoes charge generation during the charging process and '1i' within the photoconductive layer during photofatigue recovery.
isss. 2v(7)--A charge generation layer (CG L) which shares the functions of 60't' and 36.2, respectively.
generating layer) and charge transport layer (
CTL: char-ge transfer
It is preferable to use a functionally separated organic photoreceptor consisting of 1ayer). A photoreceptor constructed by laminating two charge generation layers using bisazo pigments and a charge transfer layer consisting of a triphenylamine charge transfer agent dissolved in polycarbonate. The above process was carried out using , with good results.

As described above, the method of the present invention produces black images.
When producing a full-color copy or a two-color copy from an original having a chromatic image and a chromatic image, erase the latent image of the black image and form a latent image of an image of a specific color component only for the chromatic image, In addition, since the latent image of the black image can be formed independently, the black image can be reproduced with only black toner, resulting in a bright image with excellent color reproducibility.
Not only can a clear copy be obtained, but also the effect of reducing toner consumption can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram illustrating a color reproduction method of a color copy made from a latent image obtained by the method of the present invention, and Fig. 2 is a schematic diagram illustrating a color reproduction method of a color copy made from a latent image obtained by a conventional method. Schematic diagrams explaining the color reproduction method, Figures 3 and 4
Each figure is a schematic diagram explaining an embodiment of the color latent image forming method of the present invention in the order of steps. 1... Original 2... Color toner 3... Transfer paper 4... Black toner 5... Photoconductor
6... Support layer 7 Charger 8... Static eliminator 9.10.11... Filter inspection W Zhao i 1! I F j, a floor 1
Eyes and stomach (2) Procedural amendment July 1011], □4 ``゛"""°""", 1 1 Indication of the case゛)'j 1985 Patent Application No. 10
No. 2726 pa) Aggression・1 2 Name of the invention 8″) Color, Ue, 5yo・kawa□j 3 Person making the amendment■ (Patent related to the incident r l'
+ Applicant, Minoru YflX Okigei Name (Name) (674) Ricoh Co., Ltd. 4 Agent Address 2-32-4 Nishi-Shinbashi, Minato-ku, Tokyo Kaji Kogyo BiJ Shi'll111Liton (433) 4564
Postal code: 105 Name: Patent attorney (6313)
Takehisa Ito 5 Date of amendment order (voluntary)
- Month, Day 6, 1939, Detailed Description of the Invention column 7 of the specification to be amended, Contents of the amendment (1) From page 12, line 20 of the specification letter to page 13, line 3, “The process of the present invention . . . "Share the functions of each person" is corrected to "-For example, due to the photosensitive characteristics of the photoreceptor." (2) On page 13 of the same book, lines 6 to 10, ``It is better to use a photoreceptor'' is corrected to ``to attach.''

Claims (2)

[Claims] (1) In a method of forming an electrostatic latent image on a photoreceptor corresponding to an image of a certain color component of a chromatic image of a document containing black and chromatic images by electrophotography, (a) on the photoreceptor; (b) Uniformly charging the photoreceptor; (c) On the photoreceptor corresponding to areas other than the black image area of the document. a step of exposing the photoreceptor to the original optical image with a necessary and sufficient amount of light to erase the optical fatigue and charge formed in each of the above steps in the area (d) corresponding to the black image area of the original on the photoreceptor; (e) performing a charging operation on the photoconductor to charge the photo-fatigue area and the non-fatigue area at different potentials; and (f) the step (c) above. A latent image forming method comprising the step of exposing a light image of a certain colored light component of reflected light of the same document to the same position on a photoconductor where the document was exposed. (2) The latent image forming method according to claim 1, wherein the photoreceptor is a functionally separated organic photoreceptor comprising a charge transfer layer and a charge generation layer.