JPH02236569A - Electrostatic latent image development method - Google Patents

Abstract

PURPOSE:To realize excellent gradation reproductivity and the reproduction of a thin character without surface staining by charging the toner of each developer into the same polarity while developing an image, and varying the electrifying amount of each toner. CONSTITUTION:Developing parts 44 and 45 which have plural independent developing sleeves are provided, and latent image is developed in each developing unit. Viewing the constitution of the developing parts 44 and 45 based on the unit of the 44, developer of two-component system composed of the toner and carrier is housed. The developer is held on the developing sleeve 41 incorporating a magnet 411, and the electrostatic latent image on a photosensitive body 1 is developed with it. While developing the image, the toner of each developer is charged into the same polarity, and the electrifying amount of each toner is varied. Thus, the gradation reproductivity is improved, and an image, where a thin character is excellently reproduced without surface staining can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrostatic latent image developing method, and more particularly to an electrostatic latent image developing method that can produce 1q of images with excellent gradation reproducibility.

[Prior Art] In a conventional magnetic brush developing machine, in response to the demand for high-speed development, a required developed density was secured by increasing the number of rotations of the magnetic brush.

A developing machine is configured using a plurality of magnetic brushes to increase the contact area between the magnetic brushes and the latent image carrier in the developing section,
There is a multi-component magnetic brush development method that provides high-speed development characteristics with little density loss without increasing the rotational speed of the magnetic brush.

The fourth section explains the operating principle of this multi-component magnetic brush development method.
This will be described below with reference to the figures. First, the developer held on the surface of the sleeve (2) by the magnetic force of the fixed magnetic roller moves clockwise as the sleeve (2) rotates. Next, since N1 and S4, A and B, and N1 and 83 of fixed magnetic rollers It moves in the magnetic field formed between Sleeve E and Sleeve E, and moves to the position of magnetic pole S4 on Sleeve E without entering between Sleeve E and Sleeve E. The developer transferred onto the sleeve (2) further moves clockwise as the sleeve (2) rotates, and is peeled off from the surface of the sleeve (2) by a scraper placed at position C of the fixed magnetic roller (2).

In such a multi-component magnetic brush development method, since the contact area between the developer and the latent image carrier can be increased in the IJO, development with high image density can be expected.

However, in recent years, higher image quality has been sought, and in particular, faithful reproduction of color originals has become necessary.

For such needs, the unit shown in FIG. 4 cannot provide images with sufficiently excellent reproducibility. One of the reasons for this is that, in the case of photographic originals, images with excellent reproducibility cannot be produced unless the gradation is good in either black-and-white copies or color copies.

Also, in the unit shown in Figure 4, 1~
Since the sharpness moves, especially if the original is a thin line, the sharpness will be worse than the original, and the characters will become thicker.

Therefore, various gradation improvement techniques have been proposed. One of them is, for example, a conductive layer of 10 dS, a leading layer, and an insulating layer.
In a method of forming a color-separated latent image by subjecting a photoreceptor consisting of layers to primary charging, secondary charging, simultaneous color separation exposure, and full-surface exposure, there is a method in which gradation control is performed in the secondary charging and simultaneous color separation exposure step.

Another method is to resolve the latent image into halftone dots, create a peripheral electric field in the entire image, and effectively utilize the development edge effect to reproduce halftones in dots, improving gradation (using a screen). γ improvement method).

In addition to the above methods, there are a γ-improving method using dot erase, a γ-improving method using a superimposition method (latent image γ superimposition method, image γ superimposition method), and the like.

[Problems to be Solved by the Invention] However, none of the above gradation improvement methods focuses on the toner in the developing section, and improvements from this aspect are expected.

The present invention has been made in view of the above points, and its purpose is to:
By paying attention to the toner in the developing section and improving its structure, gradation reproducibility is improved, there is no background smearing, and thin text is reproduced well, and images with excellent color reproduction can be obtained when copying in color. An object of the present invention is to provide a method for developing an electrostatic latent image.

[Means for Solving the Problems] According to the present invention, an electrostatic latent image is formed on an image carrier, a first developer is applied thereto, and a second developer is subsequently applied thereto. Provided is an electrostatic latent image developing method characterized in that the toners being developed in each developer are charged to the same polarity, and the amounts of charge of both toners are different. .

That is, in the present invention, a developing section having a plurality of independent developing sleeves is provided, and each developing unit develops a latent image to obtain a faithfully reproduced image (even color reproduction) of the original. This enables development suitable for high image quality.

In the following, an example of the invention will be described in more general detail in connection with a copying process, with reference to the accompanying drawing (FIG. 1).

First, the surface of a photoreceptor (inorganic photoreceptor, organic photoreceptor) 1 is uniformly charged positively or negatively by a charger 2 . Whether the photoreceptor is positively charged or negatively charged is selected depending on the type (property) of the photoreceptor 1. For example, if the photoreceptor is Se-based, it will be positively charged. Image exposure is performed on this by the optical system 3 to form an electrostatic charge image, and this electrostatic charge image is visualized in a developing section.

The visible image (toner image) is transferred to the transfer paper 8 by the transfer charger 5.
The transfer paper 8 is separated from the photoreceptor 1 by the separation charger 6 and the separation claw 9 and sent to the fixing process. Further, the photoreceptor 1 is cleaned by a cleaning section 10.

The present invention is characterized by this developing section. The developing section is 44 and 4
It consists of two units of 5. Looking at its configuration based on 44 units, two-component developer consisting of toner and carrier is housed. The developer is magnet 41
The electrostatic charge image on the photoreceptor 1 is developed. Since only toner is consumed each time development is repeated, a sensor 42 detects the toner degree of the developer and new toner is supplied so that the toner degree is always constant. . 43 is a paddle wheel for stirring the developer. Note that a bias may be applied to the developing sleeve 41 as necessary. The unit 45 also has the same configuration as the unit 44.

The reasons for providing two developing units in this way are: ■ To improve gradation reproducibility; ■ To avoid background smudges and to reproduce thin characters; ■ For color copying, to have excellent color reproduction. This is to improve the performance.

In the case of an electrophotographic copying machine, the gradation reproduction curve is generally set as shown in FIG.

Considering mainly the copying of documents, the original @ density is about 0.3 for the reproduction of thin characters and fine lines such as pencil originals, but it is also about 0.1 to output at a high density and avoid background stains. At a concentration of , the toner does not adhere to the toner.

Also, even if the dark background color is developed, the light density background color is difficult to develop.

Therefore, the gradation reproduction curve has poor halftone (light density) reproducibility. The good characteristics of this tone reproduction curve are {q
This is a feature of the present invention. In the present invention, excellent gradation can be achieved by changing the composition of the developer stored in the developing section (44, 45).

That is, in the present invention, the toners being developed in each developer are charged to the same polarity, and the amounts of charge of the two toners are different.

In this way, the toner being developed is charged to the same polarity, and
In order to make the two toners have different charging matrices, for example, the developer may be made of two components, carrier particles and toner particles, and each carrier particle and each toner particle of the first developer and the second developer may be made of two components. are made of the same substance, and the first developer and the second developer may have different carrier/toner mixing ratios. It goes without saying that carrier particles and/or toner particles may be a combination of different materials in the first developer and the second developer as long as the above polarity and chargeability conditions are satisfied.

Next, a specific example will be explained.

First, a latent image is created using a conventional method. Then, the developing section 4
A two-component developer having a high charge amount (Q/M) (Q/M=25 μC/CI or more) is stored as a first developer.

The gradation reproduction curve here reproduces b in FIG. The next developing section 45 stores a two-component developer (Q/M=25 μC/g or less) with a low charge amount (Q/M) as a second developer. At this 45, the gradation reproduction curve is a in Figure 2.
As a result, the gradation reproduction curve C in FIG. 2 is obtained, and image reproduction superior to conventional development methods is possible. Therefore, the present invention is an extremely effective means for reproducing black and white images or especially painterly color images.

[Example] Next, the present invention will be explained with reference to Examples. Note that parts are based on weight.

Example 1 Average particle diameter of approximately 100μ as carrier for two-component developer
m steel beads (Microshot SF-100 manufactured by Fr Tobrator Co., Ltd.) were prepared.

Further, a mixture of the following formulation was kneaded under heating on two rolls, cooled, and then crushed and classified to produce a toner for a two-component developer having a particle size of 5 to 20 μm.

Boristyrene (Esso!!!0-125)
100 parts metal-containing dye (Spiron Black 8th, manufactured by Hodogaya Chemical Co., Ltd.) 5 parts Rikiichibon Black (#44 manufactured by Mitsubishi Kasei Corporation) 10 parts These carriers (100 parts) and toner (1.5 parts) were mixed to form a two-component system. A developer was prepared. The toner charge ratio (Q/M) of this developer by the blow-off method was -32 μC/q.

Further, 100 parts of these carriers and 3.0 parts of toner were mixed to prepare a two-component developer. The toner charge ratio (Q/M) of this developer by the blow-off method was -16 μC/CJ.

As described above, Q/M was varied by changing the toner concentration in the developer. The developer with higher Q/M was placed in unit 44, and the developer with lower Q/M was placed in unit 45 in FIG. 1, and an image output test was conducted.

Example 2 The carrier of Example 1 (steel beads with an average particle diameter of about 100 μm) was prepared as a carrier for a two-component developer.

Meanwhile, the mixture of the following formulation was heated on two roll mills.
After kneading under heat and cooling, the mixture was crushed and classified to produce a toner for a two-component developer having a particle size of 5 to 20 μm.

Polystyrene (Esso D-125 > 10
0 parts Dye (Special Black 3B manufactured by Orient Chemical Co., Ltd.) 5 parts Carbon black (1144 manufactured by Mitsubishi Kasei Corporation) 100 parts These carrier 1 (} Part O and 1.5 parts of toner were mixed to prepare a two-component developer. .The Q/M for this developer is 3.
It was measured to be 2 μC/g.

Further, 100 parts of these carriers and 3.0 parts of toner were mixed to prepare a two-component developer. The Q/M in this developer was measured to be 16 μC/C2.

As described above, Q/M was changed by changing the toner concentration in the developer. The developer with higher Q/M was stored in 44 developing units, and the developer with lower Q/M was stored in 45 developing units, and an image production test was conducted.

As shown in FIG. 1, in Example 1, the image was produced by charging the photoreceptor with Se to +700 V and copying at a speed of 20 copies per minute. Further, in Example 2, an organic photoreceptor was used as the photoreceptor, and the photoreceptor was charged to -750V, and copying was performed at a speed of 20 copies per minute.

When image production was carried out, it was possible to obtain a C curve as the gradation reproduction curve shown in FIG. 2 for both Examples 1 and 2. (20-level Kodak Gray Scale (KG)
When I looked at how many steps to reproduce S) as the original, I found 14 steps. ) Next, examples of color toners are shown.

A toner was prepared by replacing the metal-containing dye in Example 1 with salicylic acid zinc salt (Bontron E-84, manufactured by Orient Chemical Co., Ltd.) and carbon black, and using the marking materials shown in Table 1 below. When a developer similar to the above was prepared and examined, it was possible to obtain the gradation reproduction curve for each color toner as a coloring material.

Table 1 [Effects of the Invention] As is clear from the above explanation, the method of the present invention can
It has excellent printability, no background stains, good reproduction of thin characters, and can form images with excellent color reproduction in the case of color copying.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an apparatus for carrying out the method of the present invention, Fig. 2 is a graph showing a tone reproduction curve of the present invention, and Fig. 3 is a general tone reproduction of an electrophotographic reproduction machine. The graph showing the curve, FIG. 4, is an explanatory diagram showing the conventional multi-component magnetic brush method.

Claims (3)

[Claims] (1) In a developing method in which an electrostatic latent image is formed on an image carrier, a first developer is applied thereto, and then a second developer is applied to the image. An electrostatic latent image developing method characterized in that the toners are charged to the same polarity, and the amounts of charge of both toners are different. (2) The electrostatic latent image developing method according to claim 1, wherein the developer comprises a two-component system of carrier particles and toner particles. (3) A patent in which each carrier particle and each toner particle of the first developer and the second developer are made of the same substance, and the carrier/toner mixing ratio of the first developer and the second developer is different. An electrostatic latent image developing method according to claim 1.