JPH0210948B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrophotography, and more particularly to a photoconductor for forming an electrical latent image and a recording method thereof.

FIG. 1 shows the configuration of a laser beam printer to which the present invention can be applied. A photoconductive drum 1 is uniformly charged with a charger 2. Next, the laser beam image 3 is irradiated while scanning in parallel to the drum axis. The charge latent image thus created on the drum is developed by a developing device 4 to form a toner image on the drum. Next, this is transferred onto the recording paper 5 while a transfer device 6 applies a corona charge for transfer. After the afterimage is erased using a post-transfer erasing lamp, the toner image remaining on the drum is cleaned using a cleaner.

Although the toner image formed in the manner described above corresponds to the charge image on the drum, a problem arises because the optical image used is coherent monochromatic light, typically a laser beam. In other words, when the drum is irradiated with laser beam light, the laser light causes interference in the photosensitive area of the photoconductor layer, forming a striped pattern of light, so the latent charge image created by the light irradiation also becomes a striped pattern. . Therefore, the developed and transferred toner image also has a superimposed pattern of light and shade. This pattern is
This tends to occur in the midtones and background areas of images. In order to eliminate the pattern thus generated, conventional methods have been used to adjust the development and overexpose the image, but these methods have had drawbacks such as poor reproduction of intermediate tones and the loss of fine lines. Further, as for the development method, it was necessary to use reversal development (adhering toner to the exposed area), which is less likely to produce such a pattern, and to avoid using the regular development method.

An object of the present invention is to provide a photoconductor and a recording method therefor that do not cause such inconvenience, and for this purpose, interference of laser beam light within the photoconductor layer is reduced or prevented. .

FIGS. 2 to 5 show examples of various conventional photoconductors and how interference fringes are formed.

FIG. 2 shows a structure having a main photosensitive layer in the middle of the photoconductor layer, with 10, 11,
Twelve photoconductors, , are stacked. The main photosensitive layer of this photoconductor is the photoconductor layer 11. For example, on a mirror-finished Al substrate, 50μ of Se for the photoconductive layer 10, 1μ of Se-Te for the photoconductive layer 11, and 2μ of Se for the photoconductive layer 12 are deposited. When used, it becomes a photoconductor with high sensitivity to light of 600 to 900 nm. Moreover, the photoconductor layer can easily transmit light of 600 nm or more. When a photoconductor having such a structure is irradiated with semiconductor laser light l ₁ l ₂ of, for example, 780 nm, the laser light l ₁ l ₂ passes through the photoconductive layer, and part of it is absorbed and exposed to light by the photoconductive layer, but part of it is passes through, and a portion is reflected at the interface with the photoconductive layer.
The laser beam light that has passed through the photoconductive layer is reflected by the substrate 9, passes through the photoconductive layer again, and advances to the photoconductive layer. At this time, the reflected light l ₁ ′ and
l ₂ ″, l ₃ ′ and l ₁ interfere, creating a pattern of light intensity stripes inside the photoconductive layer. Since the photoconductive layer is exposed to this light intensity pattern, a latent charge image is formed by this. The above explanation shows a typical path of light that forms a striped pattern, but there are other types of reflected light at the interface of the photoconductive layer that also cause the formation of interference fringes. .

In FIG. 3, a photoconductive layer ( ) 13 and a photoconductive layer ( ) 14 are formed on a substrate 9, the photoconductive layer ( ) acts as a photosensitive layer, and the photoconductive layer ( ) has a function of transporting charges. FIG. 3 is a diagram showing a photoconductor. In FIG. 3, laser light l ₁ is reflected within the photoconductive layer ( ) and interferes with laser light l ₂ .

As described above, interference may occur within the photoconductor, or in addition to the above explanation, interference may occur within the surface protective layer, surface insulating layer, and underlayer, which are the constituent elements of the recording medium including the photoconductor. Since the photoconductive layer is exposed to light, the above-mentioned striped pattern occurs in the image.

The present invention is intended to reduce and eliminate such interference fringe patterns, and provides a method for achieving the above object by reducing and eliminating reflections at the interfaces of multilayer photosensitive layers as shown in FIGS. 2 and 3. It is. Interference occurs due to reflections at the boundaries of layers in a multilayer structure or reflections at the substrate. To prevent interference due to reflection with the substrate, make the substrate a light absorber.

Make the surface of the substrate light scattering.

It is possible that However, reflections at interlayer interfaces occur when there is an abrupt change in the refractive index at the boundaries of adjacent photoconductor layers (e.g., when adjacent layers have different compositions). Therefore, in order to eliminate this reflection, the refractive index at the interface should not be changed suddenly, but should be changed gradually to the extent that no reflection occurs. One way to do this is to control the amount of metal evaporated while depositing the layer, ie to gradually change the composition at the interface of the layer. 4 to 6 show embodiments of the present invention.

In FIG. 4, the optical properties (refractive index) at the boundary of the photoconductor layer ( ) 11 are gradually changed to suppress reflection at the boundary surface, and as shown in FIG.
This reduces the _{interference of}
The content of
This can be obtained by suppressing the amount of Te evaporated during vapor deposition. This method is applied to the photoconductor layer ( ) 14 in FIG.
When applied to this method, reflection at the boundary between the photoconductor layer ( ) 13 and the photoconductor layer ( ) 14 can be reduced.

FIG. 5 shows a method in which a method of providing a light absorption layer 15 to prevent reflection on the substrate 9 is combined with the method of FIG. The light absorption layer 15 is made of, for example, an Al substrate treated with black alumite treatment (oxidized film treatment), or a resin mixed with carbon, color pigments, or dyes.
It may be applied to a thickness of about 0.1 to 1 μm. If such methods are used in combination, no interference fringes will occur at all.

FIG. 6 shows the method of FIG. 4 combined with a method of eliminating interference by using a substrate 9 having a light-scattering surface and scattering the reflected light on the substrate surface. , satin finish, sandblasting, etc.

The methods shown in FIGS. 5 and 6 can also be applied to the photoconductor having the structure shown in FIG.

As described above, the present invention uses a photoconductive recording material for electrophotography in which reflections at the boundaries of a multilayer photoconductor are reduced or eliminated so that interference does not occur, and a coherent optical image is transmitted through part or all of the recording material. Since the above-mentioned recording medium is irradiated with a charge latent image to form a charge latent image, a good image can be obtained since interference striped images are not generated in the image.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a laser beam printer, FIGS. 2 and 3 are diagrams illustrating an example in which interference fringes are produced by a laser beam, and FIGS. 4 to 6 are examples of the present invention. 9...Substrate, 10-12...Photoconductive layer.

Claims (1)

[Claims] 1. In an electrophotographic method in which a recording medium is irradiated with an optical image of coherent light to form an electrical latent image, light having a wavelength that passes through the recording medium is used as the coherent light, As a recording medium, a multilayered photoconductor is used, in which the refractive index is gradually changed at the boundaries between adjacent photoconductors, and a light absorption layer is provided at the boundary between the substrate and the photoconductor. An electrophotographic method characterized by forming a charge latent image. 2 In electrophotography, in which a recording medium is irradiated with an optical image of coherent light to form an electrical latent image, light of a wavelength that passes through the recording medium is used as the coherent light, and the recording medium has a multilayer structure. A photoconductor is used in which the refractive index at the boundary between adjacent photoconductors is gradually changed, and the surface of the substrate on the photoconductor layer side is used as a light-scattering surface to form a charge latent image. An electrophotographic method characterized by forming.