JPS6019508B2 - How to develop an electrostatic latent image - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for developing an electrostatic latent image provided on an electrophotographic copying material or electrostatic recording medium with an aqueous developer.

There are two types of electrophotographic development methods: the Xerox type and the Electrofox type. Both types charge the photoconductive layer of the electrophotographic copying material and form an electrostatic image by irradiating it with light, but the former uses a powder developer. The toner is then transferred and fixed onto a transfer material, and the latter is developed using a wet developer (a toner dispersed in a highly insulating organic solvent).

The method using a wet developer does not require fixing and has the advantage of good halftone reproducibility, but on the other hand, it is hygienic because the vapor of the flammable organic solvent is dissipated, and it is also troublesome to handle.

Furthermore, since the photosensitive layer is wetted, other problems occur, such as staining of non-image areas, that is, scumming. In order to eliminate such disadvantages, development using an aqueous developer has been proposed, for example, in Japanese Patent Publication No. 39-429 and Japanese Patent Publication No. 40-18993. In this developing method, an aqueous developer is supplied in a linear or dotted manner by a special section to the surface of the photoconductive layer of an electrophotographic copying material on which a latent image has been provided, so that only the charged areas are selectively wetted. As the special member, for example, a developing roller with a spiral groove is used. However, such a developing roller requires strict dimensional accuracy and shape so that a sufficient amount of developer adheres to the charged area and no developer adheres to the non-image area, so it is difficult to actually manufacture it. It is extremely difficult to process and is a practical problem.
Non-adsorbent fibers or sand cushions with fine meshes are also used as special members.

These members have the property of being wetted by aqueous developer but not absorbing aqueous developer, so that a sufficient amount of developer adheres to charged areas and does not adhere to non-image areas. In order to do this, it is necessary to form a liquid level of the developer in the area. When the liquid level of the developer exceeds the surface of the member, background staining occurs, and if this is severe, the developer wets and adheres uniformly over the entire surface to be developed, making it impossible to obtain an image. On the other hand, if the liquid level of the developer does not reach the appropriate level on the surface of the member, image unevenness including undeveloped areas called so-called white spots will occur, and when this is severe, the developer will spread over the entire surface of the surface to be developed. There is no wet adhesion at all and no image is obtained. Therefore, in order to obtain a desired image, it is necessary to maintain the relative position between the developer liquid level and the surface of the special member in an appropriate state at all times, but this is actually difficult and poses a practical problem. The present invention is a method for developing a static latent image using an aqueous developer that solves the above-mentioned problems at once, and provides a high-resolution image free from background smudges.In addition, the members required to carry out this method are as follows: This method does not require any special processing and is extremely easy to implement.

That is, the present invention applies an aqueous developer to an aqueous developer applying member in which a hydrophobic part and an absorbent member capable of absorbing and retaining an aqueous developer in minute voids therein are sequentially arranged facing a surface to be developed. of an electrostatic latent image, the aqueous developer-applying member is brought into contact with or close to the surface to be developed having the electrostatic latent image, and the aqueous development surface is selectively wet-adhered to the electrostatic latent image. This is a developing method.

The surface to be developed to which the aqueous developer is applied is the electrostatic latent image forming surface of an electrophotographic copying material or an electrostatic recording material.

In electrophotographic copying materials, a static exposure latent image is formed by charging and exposing the material in a conventional manner, and in electrostatic recording materials, a needle electrode is brought into contact with or very close to the top of the recording layer and a high voltage pulse is applied to the material. , and a static latent image is formed on the surface of the recording layer. The developing method of the present invention relates to an improvement in the method of developing the static exposure latent image thus obtained using an aqueous developer. As the aqueous developer for developing the electrostatic latent image, any known aqueous developer used for developing electrostatic latent images formed on electrophotographic copying materials or electrostatic recording materials can be used.

Typical examples of such aqueous developers are as follows. A dye solution type developer whose main ingredient is a liquid dye such as crystal violet.

In order to adjust the viscosity, surface tension, etc. of the developer, a substantially water-soluble polymeric substance such as a resin, starch polysaccharide, rubber, or latex may be included. The remainder is mostly water. '.

} A pigment-dispersed developer whose main component is a pigment such as carbon black. Water-soluble dyes and polymer substances can be blended into this. Shiichi Reactive color developer.

For example, Special Publication No. 42-27190 or Tsubaki Publication No. 4
Those described in Publication No. 3-41 which develop color by reacting components in the photoconductive layer or electrostatic recording material with other components in the developer, or those in which two or more components develop color by a catalyst etc. A substance that exists in the photoconductive layer or electrostatic recording material and is colored by a catalyst, etc. in the developer (in this case, the catalyst, etc. is only contained in water), or in the photoconductive layer or electrostatic recording material. Examples include those in which such a catalyst is present and color is developed by the use of other catalysts present in the developer. Next, the aqueous developer applying member for applying the aqueous developer as described above to the static latent image forming surface is composed of a hydrophobic member and an absorbent member capable of absorbing and retaining the aqueous developer in fine voids therein.

A hydrophobic region is a plate-like, sheet-like, or layer-like region having many minute gaps, and the shape of the gaps can be arbitrarily selected.
For example, circular or polygonal holes, grid-like slits, etc. can be used. The hydrophobic member preferably also has water repellency, and specifically includes silk and woven fabrics such as Teflon, vinylidene fluoride, polyethylene, and nylon, and stainless steel whose surface is coated with a hydrophobic and water-repellent substance. Examples include metal mesh screens, punched plates, and porous membranes made of hydrophobic, water-soluble substances such as Teflon or vinylidene fluoride. Note that the hydrophobic part of the present invention can also be obtained by surface-treating a member having a large number of fine gaps with a waterproofing agent or a water-repellent agent such as silicone. The absorbent member capable of absorbing and retaining the aqueous developer in its internal minute voids may be any material that has the function of absorbing and retaining the aqueous developer by permeating it through capillary action, and its shape may be plate-like,
You can find any shape such as cylindrical or band shape.

Absorbent materials include porous metals such as porous stainless steel, ceramics such as unglazed porcelain, porous rubbers such as sponge rubber, textiles such as cotton cloth, gauze, lace, cotton, felt, glass fiber aggregates, and paper. fiber aggregates, glass beads, etc.
Particle aggregates such as sand can be used, and if these absorbent particles are surface-treated with a hydrophilic substance, the function of penetrating and absorbing the aqueous developer becomes more effective. In the present invention, during development, an aqueous developer applying section consisting of a hydrophobic member and an absorbent member capable of absorbing and retaining the aqueous developer in microscopic voids therein is placed facing the surface to be developed. The members are arranged in sequence.

Then, the aqueous developer is supplied from the developer container to the aqueous developer applying unit, and the aqueous developer applying member is brought into contact with or close to the latent image forming surface of the silkworm. The mechanism by which a static latent image is developed by such means will be explained with reference to FIG.

The aqueous developer 1 stored in the developer container 2 permeates into the gap between the absorbent elements 3 by capillary action and absorbs into the absorbent member 4.
is absorbed and retained.

At this time, it is impossible for the aqueous developer 1 to penetrate into the many minute gaps formed in the hydrophobic, more preferably twill aqueous member 5, so that the liquid level of the aqueous developer 1 is easily maintained on surfaces. i.e. hydrophobic,
More preferably, the water-repellent member 5 not only acts as a curtain to prevent the surface of the aqueous developer 1 from reaching the surface to be developed, but also prevents the surface of the aqueous developer 1 from coming into contact with the surface to be developed. It also plays the role of maintaining uniformity at a position extremely close to the surface to be developed, without being exposed. When the aqueous developer 1 is attracted to the electrostatic latent image forming surface due to the action of electrolysis formed by the electrostatic latent image, the aqueous developer 1 is absorbed into the hydrophobic, more preferably water-repellent member 5. The aqueous developer 1 moves along the walls of the fine gaps and wetly adheres to the surface on which the electrostatic latent image is formed due to an electrocapillary phenomenon based on the action of the surface charge on the surface to be developed. If the surface to be developed is porous, the aqueous developer 1 will penetrate into the gaps inside the surface to be developed due to electroosmosis or the like. When the aqueous developer 1 wetly adheres to the image forming surface of the electrostatic tank, the surface charge on the developed surface is discharged and disappears, but in normal cases, due to the presence of wetting hysteresis, the aqueous developer 1 adheres to the image forming surface of the electrostatic port. Maintain wet adhesion. In this way, the aqueous developer can be selectively wet-adhered only to the electrostatic image forming surface. Here, when the electrostatic latent image is an electrostatic latent image formed by corona discharge or the like, the bias voltage applying power source 8 is not necessarily required.

Of course, as is known in ordinary electrophotographic technology, when the purpose is to compensate for insufficient exposure or to perform reversal development, a direct current or alternating current bias voltage applying power source is used. Further, if the static lightning latent image is formed by the PIP effect, photovoltaic effect, memory effect, etc., positive or reversal development is possible by using a bias voltage power source. As shown in FIG. 2, the aqueous developer applying section may be a roller-shaped roller having a water-absorbing member on the inside and a hydrophobic or water-repellent member on the outside.

In this case, the aqueous developer applying member contains the developer by the developer supply roller 9. In a roller-shaped aqueous developer applying member as shown in FIG. 3, the developer is supplied from inside the roller. By replacing the aqueous developer applying member with a conventional aqueous developer applying member, the developing method of the present invention can be carried out as is in an ordinary known copying machine. That is, the electrophotographic copying material 6 is charged by a charger 12 in a conventional manner, an electrostatic latent image is formed on the electrophotographic copying material 6 by image irradiation by an exposure device 14, and the visible image is transferred to the loaf 11 using an aqueous developer. Transfer one piece of transfer paper using the following method. The developer remaining on the electrophotographic copying material 6 is removed by the cleaning device 12, and the process is repeated again.
Example 1 Using electronic recopy photosensitive paper as an electrophotographic copying material,
1. Add methylene full to the aqueous developer. A skin t% aqueous solution was used.

In the developing device shown in FIG. 1, a hydrophobic member consisting of five layers of gauze was used, and a hydrophobic and water-repellent member was a 100-mesh nylon silk cloth surface-treated with a commercially available waterproofing agent.

Here, the electronic recopy photosensitive paper was charged and exposed in a conventional manner to give an electrostatic latent image to the photoconductive layer.

When the photosensitive paper having this electrostatic latent image was placed as shown in Figure 1 and the conductive backup roller 7 was moved back and forth once, a clear blue image with no background stains and excellent scale image power was formed. . Comparative Example 1 When the developing operation was carried out in the same manner as in Example 1 except that the hydrophobic/water repellent member was not used, an unclear image with poor resolution and significant background staining was formed.

For further comparison, Example 1 was used except that no absorbent material was used.
When a similar development operation was carried out, a blue image with white spots and significant image unevenness was formed. Even if the amount of aqueous developer is varied, the image may be a blue image with significant image unevenness with white spots, or a region of the developing surface may be wetly adhered with the aqueous developer and no image appears. A blue image was formed with significant image unevenness present. From these results, the precision required to control the amount of aqueous developer is extremely high, and it is practically impossible to develop wide electronic recopy photosensitive paper, especially B-5 size or larger, using the method shown here. It is.

Example 2 Using electronic recopy photosensitive paper as an electrophotographic copying material,
An aqueous developer having the following composition was used.

Water 50 parts by weight Polymer material (hydroxyethylcellulose) 1 part by weight Carbon black 2 parts by weight Formalin 3 parts by weight Aluminum ammonium sulfate 4 parts by weight Methylene flue
In the 6 weight part developing device shown in FIG. 2, porous sponge rubber was used for the absorbent part, and a 100 mesh nylon silk cloth surface-treated with a commercially available waterproofing agent was used for the hydrophobic and hydrophilic members.

The electronic recopy photosensitive paper was then charged and exposed in a conventional manner to give an electrostatic latent image to the photoconductive layer.

When the photosensitive paper having this electrostatic tank image was placed as shown in FIG. 2 and developed at a development speed of 500 skin/sec, a clear black image with excellent resolution and no background stain was formed.
Brief Explanation of the Drawings Figure 1 is an explanatory diagram specifically showing an aqueous developer applying member in order to explain the developing mechanism of the present invention, and Figure 2 is an explanatory diagram in which a roller-shaped aqueous developer applying member is used. FIG. 3 is an explanatory diagram of a developing device having a developer supply section inside a roller-shaped aqueous developer applying member, and FIG. 4 is an explanatory diagram of an aqueous developer applying member of the type shown in FIG. FIG. 7 is an explanatory diagram of a developing device showing another example of use.

1... Aqueous developer, 2... Phenomena container, 3
...Absorbent member element, 4...Absorbent member, 5...Hydrophobic/water repellent member, 6...
・Electrophotographic copying material, 7... Conductive backup roller, 8... Power source for bias voltage application, 9...
...Developer supply roller, 10...・．． transfer paper,
11...Transfer roller, 12...Cleaning device, 13...Charger, 14...
・Exposure device.

Little brother l figure 2 Plan 3 Figure 4

Claims (1)

[Claims] 1. Supplying an aqueous developer to an aqueous developer applying member in which a hydrophobic member and an absorbent member capable of absorbing and retaining the aqueous developer in minute voids therein are sequentially arranged opposite to the surface to be developed; 1. A method for developing an electrostatic latent image, which comprises bringing an aqueous developer applying member into contact with or close to a surface to be developed having an electrostatic latent image to selectively and wetly adhere an aqueous developer to the electrostatic latent image.