JPH0642081B2 - Developer - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a developer, and more specifically, in an electrophotographic apparatus or an electrostatic recording apparatus, an electrostatic latent image formed on a photoconductor or a dielectric is visualized as a visible image. And a one-component non-magnetic developing agent.

[Technical background of the invention and its problems]

A two-component developer composed of a toner and a carrier is widely used as the developer because of its good image quality.

However, on the other hand, there are drawbacks common to two-component developers as described below. That is, the toner is
It receives triboelectric charges due to mutual friction between the toner and the carrier, in which case the carrier surface is contaminated by the toner composition when used for a long time,
As a result, sufficient electric charge cannot be obtained. The toner and the carrier must be adjusted to a mixture ratio within a predetermined range, but if used for a long period of time, the mixture ratio fluctuates and deviates from the predetermined range. Generally, iron powder or glass beads whose surface is oxidized is often used as a carrier. In such a case, the carrier mechanically damages the surface of the photoreceptor.

For this reason, various developing methods using a one-component developer composed of only toner have been proposed. Above all,
Many developing methods using a developer having magnetic sensitivity and generally called magnetic toner have been proposed. Among them, those based on U.S. Pat.Nos. 3909258 and 4121931 have been put into practical use. . However, these methods also have the following drawbacks. That is, since a magnetic toner having a relatively small specific resistance is used, it is difficult to electrostatically transfer the developed image on the electrostatic latent image to a supporting member such as plain paper.
In particular, there are drawbacks such that sufficient transfer cannot be obtained in a humid atmosphere, and a color toner cannot be obtained because the toner contains a large amount of magnetic powder.

However, recently, a developing method using a one-component toner containing no magnetic powder and having a large specific resistance has been particularly attracting attention.
Examples of the developing method include those disclosed in US Pat. No. 2,895,847.
No. 3,152,012, Japanese Patent Publication No. 41-9475, 45-2877
No. 54-3624, etc., touchdown method,
Those based on the impression method and the jumping method can be given. These methods utilize conventional toners used in two-component systems.

However, in this case, it is inevitable to derive various problems related to the one-component system, as described below.

The first problem is the problem of triboelectrification.

That is, the developer must efficiently obtain the amount of charge necessary to visualize the electrostatic latent image formed on the photosensitive drum or the dielectric material in a non-contact manner in a very short time with the developer carrying member. . However, when the selenium photosensitive drum is used, the charge amount of the developer and the developer carrying member required for visualizing the image is minus 0.5 to 15 μC / g.

However, when the conventional developer used in the two-component system is used and the developer carrier and the developer are triboelectrified, a sufficient charge amount for visualizing cannot be obtained. The reason for this is that the developer used in the conventional two-component system performs the triboelectric charging between the toner and the carrier for a sufficient time to obtain the amount of charge necessary for forming a visible image. .

However, if the charge amount is high, it can cause fog, so
The charge amount of the two-component developer is controlled.

A conventional two-component developer has a binder resin having a small charge amount as a main component, and a charge control agent is added to control the charge amount.

However, since the use of a large amount of charge control agent affects the image characteristics, the charge amount of the two-component developer is determined by the binder resin as the main component.

According to the experiment, as shown in FIG. 2, the charge amount of the binder resin (blow-off method) is proportional to the acid value of the binder resin (measured by the KOH method). As is clear from FIG.
The binder resin having a low acid value has a low charge amount, and generally, the charge amount of the two-component developer by the blow-off method is 10 to 30 μC / g.

The relationship between the charge amount of the developer by the blow-off method and the charge amount of the developer and the developer carrier is shown in FIG.

As is apparent from FIG. 3, the N component developer does not have a sufficient charge amount for forming a visible image by frictional triboelectric charging between the developer and the developer carrier.

As described above, a developer having a sufficient charge amount for forming a visible image by frictional charging between the developer and the development carrier has not been developed so far.

The second problem is that the developer is applied very thinly and evenly on the surface of the developing roll.

That is, for the developing roll 1 shown in FIG.
The elastic blade is in pressure contact with a pressure of 100 g / cm to 2500 g / cm, the developer present in the developer container is conveyed by the rotation of the developing roll, and the elastic blade makes it extremely thin and even on the developing roll surface. Is applied. For this reason, the developer is required to have good fluidity and aggregation resistance.

However, the developer existing in the developer container is conveyed by the rotation of the developing roll, but in some cases, the developer is not applied to the surface of the developing roll because it becomes cohesive and lumpy. .

Also, the developer conveyed by the rotation of the developing roll is
Under the pressure contact force between the elastic blade and the developing roll, a high pressure is suddenly applied, and the developer is softened and fixed on the surface of the developing roll by frictional heat.
There is a problem that it becomes difficult to apply the developer on the surface of the developing roll very thinly and evenly. The causes are that the binder resin of the developer has a low softening point and the glass transition point is low.

Further, if the softening point becomes high, the fixing temperature becomes high, and there is a problem that it is difficult to use it in a normal office copying machine.

[Object of the Invention]

The present invention has been made in view of the above-mentioned problems, and by controlling the triboelectric charge amount of the developer, it can be applied extremely thinly and uniformly on the surface of the developing roll, and the fluidity and the aggregation resistance are excellent. It is an object to provide a developer capable of forming a highly sharp visualized image.

[Outline of Invention]

The present invention, in the binder resin, in the colored particles obtained by dispersing the colorant, by controlling the charge amount of the binder resin,
The main point is to obtain a developer having an effect of obtaining a sharp image with high resolution by controlling the charge amount of the colored particles and applying the colored particles to the surface of the developing roll in an extremely thin and uniform manner.

That is, the present invention relates to a developing roll that carries a one-component developer on the surface thereof, rotates, and develops the latent image by supplying the developer to the electrostatic latent image, and the developing roll on the surface of the developing roll. In a method of developing an electrostatic latent image in a non-contact manner using a developing device basically composed of an elastic blade arranged so as to be in pressure contact with the surface of the developing roll in order to apply the agent uniformly, The binder resin which is the main component of the developer applied to the roll has a glass transition point of 50 ° C. or higher, a softening point of 110 ° C. to 160 ° C., and an acid value of 10 to
The developer is characterized in that it is 40, and particularly preferably a bisphenol type polyester resin and a styrene-acrylic resin.

The above-mentioned colorants are generally dyes, pigments, carbon black and the like, and examples of such colorants include nicrocin dyes, carmine dyes, various basic dyes, acid dyes, oil dyes, anthraquinone dyes; benzidine. Pigments such as organic yellow organic pigments, quinantrine organic pigments, rhodamine organic pigments, phthalocyanine organic pigments, inorganic pigments such as zinc oxide, titanium oxide and red iron oxide; furnace black, acetylene black, thermal black and other carbon blacks. be able to.

Next, a manufacturing method for obtaining the developer of the present invention will be described below with reference to an example.

First, the binder resin and the colorant are mixed with a ball mill, a V-type mixer, and S.
Mix with a mixer such as a mold mixer or a cooling blender, and knead the resulting mixture with a double-arm kneader, a three-roll kneader, a pressure kneader, etc. The powder is crushed by a crusher, and the obtained powder is classified by a sieve, an air classifier or the like to prepare particles having a predetermined particle size (colored particles).

In the production of such colored particles, the type of the binder resin to be used, the type of the colorant to be dispersed, and the compounding ratio affect the charge amount of the colored particles to be obtained. To be done.

The charge amount of the colored particles obtained from the material selected from the above-mentioned binder resin and colorant is preferably minus 0.5 to 15 μC / g when a positive charging photosensitive drum is used.

If necessary, in order to improve the fluidity and the aggregation resistance of the developer, 0.05 to 2 parts by weight of hydrophobized colloidal fine particles having the same polarity as that of the colored particles are used to affect the charge amount of the colored particles. Even if it is added to the extent that it does not exist, it will not be a problem.

〔The invention's effect〕

The developer according to the present invention has various effects listed below.

(i) A developer that can be applied extremely thinly and uniformly to the surface of the developing roll is obtained.

(ii) A developer capable of obtaining efficient triboelectric charging can be obtained.

(iii) A developer having good fluidity and resistance to aggregation can be obtained.

(iv) A sharp image with high resolution can be obtained.

Example of Invention

 The present invention will be described below with reference to examples.

Example 1 Styrene-acrylic resin (Mn16.300, Mw328.000 softening point 12
92 parts by weight of 5 ° C., glass transition point of 61.2 ° C., acid value of 14.5) and 8 parts by weight of carbon black were mixed by a ball mill for about 2 hours and then kneaded by a pressure kneader for about 1 hour.

The kneaded product was cooled, coarsely pulverized with a hammer mill, finely pulverized with a jet mill, and classified with a classifier to give colored particles of 5 to 25 μm. Next, 100 parts by weight of the colored particles and 0.5 part by weight of colloidal fine particles (Aerosil R972, manufactured by Nippon Aerosil Co., Ltd.) are mixed in a ball mill, and the colloidal fine particles are adhered to the surface of the colored particles to obtain a 50% weight average particle diameter. 11.5 mm
Was used as the developer.

When the charge amount of this developer was measured, it was −6.8 μC / g.

Using this developer, in the developing device shown in FIG. 1, when a visualized image was formed under the conditions of the surface potential of the photosensitive drum plus 900 V and the developing bias minus 500 V, the image density was 1.5 and the resolution was 5 lp / mm. A good image with no image was obtained. In addition, it was fixed with a heat roll fixing device 14
Fixing started from 0 ° C, and offset did not occur even at 210 ° C.

Example 2 Bisphenol type polyester resin (Mn4.100, Mw32.00
0, softening point 135 ℃, glass transition point 78.5 ℃, acid value 20.2) 92
Part by weight and 8 parts by weight of carbon black were dispersed in a ball mill for 2 hours, and then colored particles were obtained in the same manner as in Example 1.

100 parts by weight of the colored particles and 1 part by weight of colloidal fine particles are adhered to the surface of the colored particles in the same manner as in Example 1.
A developer having a% weight average particle diameter of 13.1 μm was used.

The charge amount of the developer was −9.5 μC / g. When a visualized image was formed under the same conditions as in Example 1, a good image with an image density of 1.51 and a resolution of 5.6 lp / mm and no background fog was obtained.

Further, fixing started at 150 ° C and no offset occurred at 140 ° C to 220 ° C.

Example 3 Bisphenol type polyester resin (softening point (R & B
Method) 135 ° C., glass transition point 81.2 ° C., acid value 35) 92 parts by weight and carbon black 8 parts by weight were dispersed and mixed, and then colored particles were obtained in the same manner as in Example 1 to obtain 100 parts by weight of colored particles and colloidal form. A developer was prepared in the same manner as in Example 1 except that 0.8 parts by weight of the fine particles were used. The 50% weight average particle size of this developer is 11.8μ.
When the visible image was formed in the same manner as in Example 1, the image density was minus 13.6 μC / g.
1.4, a good image with a resolution of 5 lp / mm and no background fog was obtained, and fixing started at 160 ° C and no offset occurred at 140 ° C to 220 ° C.

Comparative Examples 1 to 3 using binder resins having different softening points, glass transition points and acid values,
In the same manner as in Example 1, 92 parts by weight of the binder resin and 8 parts by weight of carbon black were dispersed and mixed to obtain a developer.

The characteristics were examined in the same manner as in Example 1 and the results shown in the table were obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a developing device used in the present invention, FIG. 2 is a characteristic diagram showing a relationship between an acid value of a binder resin and a charge amount of a developer by a blow-off method, and FIG. FIG. 3 is a characteristic diagram showing the relationship between the charge amount of the agent by the blow-off method and the charge amount obtained by the developing method shown in FIG. 1. 1. ...... Developing roll, 2. …… Elastic blade 3. ...... Developer container, 4. …… Developer 5. ...... Photosensitive drum, 6. ...... Rigid metal piece 7. …… Side wall

Claims (4)

[Claims] 1. A developing roll that carries a one-component developer on the surface thereof and rotates to supply the developer to an electrostatic latent image to develop the latent image, and the developer on the surface of the developing roll. Used in a method for developing an electrostatic latent image in a non-contact manner by using a developing device basically composed of an elastic blade arranged so as to be in pressure contact with the surface of the developing roll in order to uniformly apply Characterized in that the binder resin, which is the main component of the developer applied to the developing roll, has a glass transition point of 50 ° C or higher, a softening point of 110 ° C to 160 ° C, and an acid value of 10 to 40. 2. A colloidal silica of 0.05-2 in the developer.
The developer according to claim 1, wherein the developer is added by weight. 3. The developer according to claim 1, wherein the binder resin is a biphenyl type polyester resin. 4. The developer according to claim 1, wherein the binder resin is styrene-acrylic resin.