JPH03191370A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a developed picture having high image density and stable high-definition by forming a grain layer, which is triboelectrified to the opposite polarity of toner on an elastic regulating member in advance. CONSTITUTION:A surface where an elastic blade 5 abuts on a developing sleeve is coated with fine grain 9 of resin, in advance before the operation of this device is started; the fine grain 9 is positively triboelectrified, the opposite polarity of toner, when the fine grain 9 and the toner are in friction. As the grain 9 with which the elastic blade 5 is coated, one whose volumetric mean grain size is smaller than that of the toner is preferable. By the presence of the grain 9, releasability of the toner grain 9 from the blade 5 and lubricating ability are improved, and rolling of the toner grain in a nip part is improved. Since the distribution of triboelectrification is made sharp, image density is stable and high from the beginning, and a developed picture having high- definition can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device for an electrophotographic apparatus such as a laser beam printer.

[Conventional technology]

A method has been proposed in which an elastic member such as urethane rubber is brought into contact with the developing sleeve to coat a thin layer of toner at the nip between the sleeve and the elastic member. Since the toner is actively charged in the process, it is possible to increase the image density and there is an advantage that a better image can be obtained.

[Problem that the invention is trying to solve]

However, in the above conventional example, when outputting images, there was a problem that the density of the solid image was low (hereinafter referred to as "initial density rise") from the initial stage until about 300 deer prints were made. . This is the amount of triboelectric charge (hereinafter referred to as tribo) that the toner particles on the sleeve have.
The distribution changes depending on the usage time (this is possible. In other words, when printing, for example, a deer on about 300 sheets from the beginning, it is not possible to apply sufficient triboelectricity to the toner particles on the sleeve, and the triboelectric distribution changes as shown in Figure 6. As shown, it is broad, and the tribo remains low even on average.

On the other hand, after printing approximately 300 sheets, for example, the toner is sufficiently circulated and stirred near the sleeve.
Since the toner particles receive sufficient triboelectric charge due to frictional charging with the sleeve and blade, the triboelectric distribution becomes sharp as shown in FIG. 7, and the average triboelectric charge becomes high. For this reason, the developability is different between the initial stage and after approximately 300 prints, and in the initial stage, the tribo distribution of toner on the sleeve is broad, and there are many toners with low tribo, which is thought to cause a decrease in density. .

[Means to solve the problem]

According to the present invention, in a developing device in which an elastic regulating member is brought into contact with a developer carrier, a particle layer charged to a polarity opposite to that of the developer is provided on at least the surface of the elastic regulating member that comes into contact with the developer carrier. This improves the rolling properties of the developer particles at the nip between the elastic regulating member and the developer carrier, and also sharpens the tribo distribution, resulting in stable image density from the initial stage. This allows a developed image of image quality to be obtained.

〔Example〕

Hereinafter, the present invention will be described in detail based on the accompanying drawings.

FIG. 1 shows a sectional view of a first embodiment of a developing device in which the present invention is applied to a laser beam printer using a reversal development method.

In FIG. 1, the electrophotographic photosensitive drum l is charged with a negative potential by a primary charger (not shown), for example, Vd=-.
After being charged to 650V, it is exposed to light by an exposure means (not shown) such as a laser beam to form a negative latent image (for example, potential Vi!
= -100V) is created. This latent image is visualized by reversal development using a developing device using negatively charged high resistance component magnetic toner. That is, toner adheres to the area of the drum that is irradiated with light and becomes visible.

In this example, the following magnetic toner was used.

The above components were put into the steps of mixing, kneading, coarsely pulverizing, and pulverizing into 9 classifications to obtain a classified toner product having a volume average particle diameter of 10 μm. To 100 parts by weight of this classified product, 0.9 parts by weight of silica fine particles treated with dimethyl silicone oil for improving toner fluidity and/or toner charge control are externally added and mixed to form negatively chargeable high resistance toner T. did.

The developing roll 2, which forms a developing section in close opposition to the photosensitive drum 1, is composed of a non-magnetic conductive sleeve 4 made of aluminum or the like that encloses a magnet roll 3, and its surface is roughened by sandblasting or the like. The developing roll 2 carries the magnetic toner T in the container 7 by magnetic force and conveys it by rotating in the direction of the arrow.

In the developing roll 2, an elastic blade 5 (urethane rubber with a thickness I, Om m and a hardness of 65°) held in a container 7 by a blade holding member 6 is applied with linear pressure (sleeve longitudinal direction 1c).
The sleeve is in contact with the center of the developing roll in the forward direction relative to the rotating direction with a contact pressure of 15 g/cm (contact pressure per m), and is made to be thinner than the minimum gap between the sleeve and drum in the developing section. A developer layer 8 is formed.

Further, the developing roll 2 is supplied with an alternating current voltage (for example, a rectangular wave,
A developing bias consisting of a DC voltage of -500 V superimposed on a peak-to-peak voltage of 1,400 V and a frequency of 1,800 Hz was applied.
An oscillating electric field is formed in the developing section to develop an electrostatic latent image.

The surface of the elastic blade 5 which contacts the developing sleeve is coated with fine resin particles 9, which are triboelectrically charged to the opposite polarity to the toner when they rub against the toner, before the apparatus starts operating. In practice, fine resin particles can be attached to paper, cloth, etc., and applied to the surface of the elastic blade while being rubbed. When an image was output using the developing device of this example, the solid black image density was 1.42D, vertical,
A black image with a width of 5 mm (hereinafter referred to as 50 density) is 1.45
A high-density image labeled D was obtained. Also, the effect is 2
It lasted about 00 copies. In addition, as in the conventional example (in a developing device that does not apply positively charged resin particles, the initial solid density is 1).
．． The 35D 15° density was 1,390, and it took about 300 deer prints before the density rose.

In the present invention, after about 300 deer prints, fine silica particles externally added to the toner adhere to the surface of the elastic blade and the contact area of the developing sleeve, forming a layer of silica.
This was done with the focus on the fact that by improving the releasability between the blade and the toner, toner particles roll better at the nip portion of the elastic blade, and sufficient frictional electrification is achieved.

The particles applied to the elastic blade are particles whose volume average particle diameter is smaller than that of the toner (preferably, the volume average particle diameter is 115 or less than that of the toner.The volume average particle diameter is determined by the coulter counter. (can be measured using
Preferably, the presence of these particles improves the releasability and lubricity between the blade and the toner particles,
This has the effect of improving the rolling of toner particles in the nip portion.

Furthermore, when fine particles that are charged to the opposite polarity to the toner due to friction with the toner particles are applied as in this example, the friction with the fine particles imparts a sufficient charge to the toner particles, which is particularly effective. .

Further, the positively charged resin particles electrostatically adsorb the silica particles externally added to the toner, and have the effect of promoting the formation of a silica layer on the surface of the elastic blade.

The positively chargeable resin particles used in this example are produced by a spray drying method, a suspension polymerization method, an emulsion polymerization method, a seed polymerization method, or the like. From the viewpoint of particle shape retention, it is preferable that the resin of the positively chargeable resin particles has a weight average molecular weight of 10,000 to 200,000 as determined by GPC chromatography. Examples of the resin fine particles of the present invention include methyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, N-methyl-N-phenylaminoethyl methacrylate, diethylaminoethyl methacrylamide, and dimethylaminoethyl methacrylamide.

Resin particles obtained by polymerizing vinyl monomers such as 4-vinylpyridine and 2-vinylpyridine or a mixture of these monomers are used. In order to impart positive chargeability to the resin particles, a method of polymerizing monomers using a nitrogen-containing polymerization initiator may be used, or a method of polymerizing a monomer composition containing a nitrogen-containing vinyl monomer may be used. It's okay.

The above resin fine particles have a volume average particle diameter of 0.1-1.0 μm.
range, and the amount of triboelectric charge is 50 to 600 μC/g
Preferably, the range is .

The embodiments of the present invention have been described above using a negatively chargeable, high-resistance component magnetic toner as a developer.

It can be applied regardless of whether it is magnetic or non-magnetic.

In addition, as for the material of the elastic blade, other rubber elastic bodies or resin elastic bodies can be used, and as shown in Fig. 5, the elastic blade is in contact with the belly in one direction counter to the rotating direction of the sleeve. It is also effective for developing devices.

[Example 2] As explained in Example 1, at least the surface of the elastic blade that contacts the developing sleeve is coated in advance with particles having a smaller particle size than that of the toner, and further with particles having a polarity opposite to that of the toner. By doing so, the "rise of initial concentration" can be improved.

The present embodiment has the additional purpose of further sustaining this effect, and is characterized in that the surface of the elastic blade in contact with the developing sleeve is roughened and the fine particles are applied thereto.

FIG. 2 shows a view of the vicinity of the blade of this embodiment. The elastic blade 25 that comes into contact with the sleeve has a minute recess 26 on its surface.
is formed. The average depth of No. 26 is preferably smaller than the volume average particle size of the toner so as not to inhibit the rolling of the toner, and more preferably smaller than the particle size of the toner that contributes to at least development, and is preferably about 0.1 to 5 μm. .

In this example, a recess of approximately 1.0 μm was provided along the direction perpendicular to the rotational direction of the developing sleeve (the longitudinal direction of the blade). In this example, the concave portion was formed by pouring rubber into a mold and integrally molding the blade holding member and the rubber blade.

By applying the fine particles used in [Example 1] to the above elastic blade, the fine particles are retained in the recesses of the blade as shown in Fig. 2, making it possible to further sustain the effect of increasing the concentration, and the initial Since then, it has become possible to stably form images with sufficiently high density over a long period of time.

[Embodiment 3] A developing device using a developing sleeve having a resin layer containing conductive carbon and graphite on its surface has been proposed (Japanese Patent Applications No. 63-108803 and Japanese Patent Application No. 63-106463). This developing device has the excellent feature of preventing excessive charging of the toner present on the developing sleeve and stabilizing the charging of the toner, but the initial triboelectricity of the toner tended to be even lower.

In Embodiment 3 shown in FIG. 3, a case will be described in which the present invention is applied to a developing device using the above-mentioned conductive resin sleeve.

The sleeve 34 in FIG. 3 is made of 50% by weight phenolic resin as a binder and 5% by weight conductive carbon (CONDUCTEX900 manufactured by Columbia).

A coating agent made by kneading graphite (C3PE manufactured by Nippon Graphite Co., Ltd.) at a weight ratio of 45% was diluted with methyl cellosolve and methanol, and a film thickness of 5 was formed by spraying it onto the developing sleeve.
It was coated to a thickness of μm and heat-cured at 150° C. for 30 minutes. The center line average roughness Ra of the surface is 0.3
~5.0 μm, and the constitutional resistance value is 5.0 μm. OX 10°Ω
cm.

When the present invention was applied under the same conditions as [Example 1] except for the sleeve, the initial solid black image density was 1.42.
The D.50 density was 1.45D, and stable images without density changes and sleeve ghosts were obtained over time of use.

In addition, if fine particles were not applied to the elastic blade in advance, the initial solid density was 1.30D, and the 50 density was 1.35.
It was D, and it took about 500 deer prints to reach the desired density.

Here, FIG. 4 shows the results of measuring the initial tribo distribution of the [conventional example] and [the present invention] in Example 3.

It can be seen that the present invention has a sharper tribo distribution and a higher amount of charge.

As described above, the present invention is particularly effective for a developing device using a conductive resin sleeve, and is capable of making the initial toner tribo distribution high (and sharp) to increase and stabilize the image density from the beginning. was completed.

〔Effect of the invention〕

As explained above, by forming in advance a particle layer that is triboelectrically charged to the opposite polarity to the toner on at least the portion of the elastic regulating member that contacts the developer carrying member, the elastic regulating member and the developer carrying member are This improves the rolling properties of toner particles at the nip with the toner, making the tribo distribution high and sharp. As a result, it is possible to obtain a developed image with high image density from the initial stage and with high quality in a stable manner.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a developing device embodying the present invention. FIG. 2 is a diagram of the vicinity of the elastic blade of the second embodiment. FIG. 3 is a sectional view of the developing device of the third embodiment. FIG. 4 is a diagram showing the effects of the present invention according to a third embodiment. FIG. 5 is a sectional view of a developing device according to another embodiment of the present invention. FIG. 6 is a toner tribo distribution diagram at the initial stage of durability using a conventional developing device. FIG. 7 is a tribo distribution diagram after printing approximately 300 sheets using a conventional developing device. 1 is a photosensitive drum, 2 is a developing roll, 3 is a developing magnet roll, 4 is a developing sleeve, 5.25 is an elastic blade, and 9 is a fine particle layer formed on the elastic blade. Ni'; 3 words 4-0 2O -IC+ and accumulation [μC]

Claims (1)

[Scope of Claims] A developing device including a developer carrier that supports and transports developer, and an elastic regulating member that contacts the developer carrier and forms a developer layer, comprising: at least the developer of the elastic regulating member; At the carrier contact part,
A developing device characterized in that a particle layer is formed in advance to be charged to a polarity opposite to that of a developer.