JPS5977460A - Formation of color image - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming color images, and more particularly, to forming a color image by controlling the apparent surface voltage level on the photoconductive surface of an electrophotographic member or other photoconductive member. The present invention relates to a method in which the apparent surface voltage can be relatively roughly adjusted by obtaining Dmax, )E, and Dmax can be finely adjusted without considering deterioration in color tone. In addition, Dm
The requirements of the aX 7 actor vary with different color toners and different photoconductors.

Electrophotographic imaging methods include U.S. Patent No. 4,02 LaB.
It is preferred, but not limited to, to use the electrophotographic members described in No. 5 or US Pat. No. 4.2-6.9,9 J-9. Is such an electrophotographic material high-speed and high-resolution? present.

To form an electrophotographic color image, first, a corona generating device is used to charge the photoconductive surface of the electrophotographic member to an apparent surface voltage, and the photoconductive surface is charged with the above-described 1ii.
i give Then a charged photoconductive surface? Exposure to photonic energy projected through the color-separating transparent laminate forms an electrostatic latent image in the photoconductive direction. Finally, a specific toner is applied to the electrostatic latent image to make it a visible image.

The various color toners used to form color images exhibit individual non-linear characteristics specific to that toner, particularly in the relationship between the density gradient in high density areas and the apparent surface voltage established on the photoconductive surface. exhibits. The present invention uses such relationships for the various toners used to obtain and vary the desired density. desired maX
The density will vary depending on each of the different color toners used.

Conventionally, to form a color image with a desired maximum density, the exposure intensity, the exposure period, or both have been varied. However, in this method, the maximum
It was not possible to consistently reproduce the concentrations over and over again.

In forming color images, it is advantageous to reduce the variables so that images can be formed consistently and repeatedly.

The present invention charges the photoconductive surface of an electrophotographic member with a corona generator to a predetermined apparent surface voltage corresponding to a selected optical density, and then exposes it to an image pattern to form a latent image of the pattern; In forming xerographic color images by toning with color toners exhibiting specific color density characteristics, the maximum color density (D
maX) is varied incrementally to a value that specifically corresponds to each color toner used.

The present invention will be explained with reference to the drawings.

The present invention provides a method for forming color images in which a preselected DmaX density is obtained by roughly controlling the apparent surface voltage level (ASVI) on the photoconductive surface of an electrophotographic member. Do it like this.

FIG. 1 diagrammatically shows the steps of a method for forming color images according to the invention. A photoconductive member 1o having a leading side 12 facing downward is mounted on a carriage 14. In step 1, the carriage 14 is positioned at a home position above the exposure station. A corona generator [16 is provided adjacent to the copyboard 20. A light energy source 18 is located below the copyboard 20. A color separation transparent plate 22 is placed on the copyboard 20. An apparent surface voltage (ASVI) sensor 24 is provided adjacent the corona generating device 16. The functional stations include a toning station 26 and an image transfer station 28. 12 are sequentially transferred to the functional stations of the above functions.

Step 2 shown in FIG. 1 shows a state in which the photoconductive surface is transferred to the L side of the corona generating device 16 and the ASV sensor 24. In this step, a measurement signal 25 is applied from the ASV sensor 24 to the control unit 80. Operator input is provided to the corona generator 16 corresponding to the desired concentration and a feedback control variable responsive to the measurement signal 25 from the ASV sensor 24 .

Operation of the control unit 30 can be carried out manually or automatically. Note that this control unit will be described in detail later.

FIG. 2 is a characteristic diagram showing the general relationship between the density of a color toner, for example cyan, and the apparent surface voltage level. Generally, when forming a color image, a composite image is formed using toners of four colors: yellow, magenta, cyan, and black. Each of these color toners has a photoconductive direction 12.
It exhibits distinct characteristics depending on the concentration related to the apparent surface voltage set to . Further, toners of different colors and hues can be applied separately in different density ranges, as shown by the eight curves in FIG. 2, so that the density desired by the user can be varied.

Step 8 of FIG. 1 shows the photoconductive member 1o being returned to its home position above the exposure station. Here, the photoconductive direction 12 is brought into intimate contact engagement with a color separation transparent plate 22 mounted on a copyboard 2°. Photoconductive surface 12 is then exposed to a predetermined intensity of light energy from light source 18 through color separation transparent plate 22 for a period of time. This forms an electrostatic latent image in the photoconductive direction 12 corresponding to the image carried by the color separation transparent plate 22.

Step 4 of FIG. 1 shows photoconductive surface 12 being transferred above toning station 26. Step 4 of FIG.

In this step, the electrostatic latent image carried by photoconductive surface 12 is developed and immediately toned with toner of the appropriate color. At this time, one selected toning unit is energized to apply the selected color toner to the entire light guiding surface 12, fixing the selected color toner particles, and converting the electrostatic latent image into a visible image. .

Step 5 of FIG. 1 depicts the placement of photoconductive surface 12, bearing a toner image thereon, above transfer station 28. FIG. In this step, the toner image is transferred to the receptacle member.

Set up the color separation transparent plate 22 for the next coloring cycle, repeat steps 1 to 5 described above using this transparent plate 22 and the corresponding color toner, and apply each of the four transparent plates and Φ Steps 1 to 5 above are repeated for each color toner to form a composite color proof.

According to the method of the present invention, the density can be finely adjusted by controlling the level of the apparent surface voltage (As, V) set on the photoconductive surface 12. The apparent surface voltage (
ASV) is set on the photoconductive surface 12 by bringing the photoconductive surface 12 closer to the collology generating device 16 and translating it. The corona generator 16 generates a corona discharge field, ie, an output level proportional to the high voltage from the high voltage source supplied to the corona generator 16. A, SV sensor 2
4 can be an electrometer that measures the ASV, ie the charge level, on the photoconductive surface and generates a measurement signal 25 that is proportional to the ASV level.

The control unit 30 contains a programmable memory capable of storing non-linear characteristics of the density gradient for each color toner used with respect to changes in the apparent surface voltage of the photoconductive surface 12.

The control unit 30 is supplied with measurement signals from the ASV sensor 24 . The operator provides input corresponding to the desired or selected density for a particular color toner. The control unit 30 determines the desired ASV level from the desired density input and the characteristics of the particular color toner stored in the control unit's memory. The control unit compares the measured signal 25 with the predetermined ASV level and determines the measured signal 25.
Corona generator 16 is deactivated when ASV equals the predetermined ASV level.

The operator uses a densitometer to measure for each color toner the optical density of the color desired to form a color image. This densitometer reading constitutes an operator input corresponding to the desired or selected density value for a particular color toner. It should be noted that the method of the present invention may also be applied to forming images using only black toner. can.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram diagrammatically illustrating the sequential process steps fr of the color image forming method according to the present invention, and FIG. 2 is an illustration of the apparent surface voltage and density set on the photoconductive surface for various toners. FIG. ]0...Photoconductive member I2...Photoconductive surface]4
... Carriage 16 ... Corona generator 1
8...Light source 20...Copyboard 2
2... Color separation transparent plate 24... Apparent surface voltage sensor 26... Toning station 2B... Transfer station 30... Control unit. Patent Applicant Coulter Systems Corporation

Claims (1)

Claims: 1. The photoconductive side of an electrophotographic member is charged by a corona generator to a predetermined apparent surface voltage corresponding to a selected optical density and then exposed to an image pattern to form a latent image of the pattern. By selectively varying the apparent surface voltage applied to the photoconductive surface to form and subsequently toning with color toners exhibiting specific color density characteristics to form xerographic color images, the maximum Color m degrees (Dma)
A method for forming color images, characterized in that x) is incrementally varied to a value that is specific to each color toner used. & A method as claimed in claim 1, characterized in that the apparent surface voltage is varied significantly to incrementally vary the maximum color density change (Dmax) for any selected color toner. Method.