JPS616656A - Developer - Google Patents

Abstract

PURPOSE:To obtain a developer capable of forming a sharp image high in resolution by controlling triboelectrified charge amt. of each of a binder resin and a colorant, accordingly, that of colored particles and spreading said colored particles on the surface of a developing roll to an extremely thin and uniform thickness. CONSTITUTION:As the binder resin of a main component of the developer 4, resins having a glass transition point of >=50 deg.C, a softening point of 110-160 deg.C, and an acid value of 10-40 are used. It is especially desirable to use a bisphenol type polyester and a stryreneacrylic resin for the binder resin. Dyes, pigments, and carbon black, etc., are generally used as said colorant. It is desirable that a charge amt. of the colored particles obtained from the material selected among said binder resin and said colorant is -0.5--15muC/g, when a positively chargeable photosensitive drum is used. When needed, 0.05-2pts.wt. of fine colloidal paricles same in polarity as the colored particles, and made hydrophilic may be added with an amt. hardly affecting the charge amt. of colored particles in order to enhance the fluidity and agglomeration resistance.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The wand developer of the present invention is used to convert an electrostatic latent image formed on a photoreceptor or dielectric material into a visible image in an electrophotographic device or an electrostatic recording device. This relates to a one-component non-magnetic developer.

[Technical background of the invention and its problems]

Two-component developers consisting of toner and carrier are widely used because of their good image quality.

However, on the other hand, there are drawbacks common to two-component developers as shown below. In other words, ■toner is
After long-term use, the carrier surface becomes contaminated with the toner composition and, as a result, does not carry enough charge. I can get it and become Hiko. (2) The mixture ratio of toner and carrier must be adjusted within a predetermined range, but if used for a long period of time, the mixture ratio will fluctuate and deviate from the predetermined range. (2) Generally, iron powder or glass beads with oxidized surfaces are often used as carriers, but in this case, the surface of the photoreceptor is mechanically damaged by these carriers.

For this reason, various developing methods using a one-component developer consisting only of toner have been proposed. And so,
Many development methods have been proposed that use a developer that is magnetically sensitive and is generally called a magnetic toner.1 Among these,
Those based on US Pat. No. 3,909,258, US Pat. No. 4,121,931, etc. have been put into practical use. However, these methods also have the following drawbacks. In other words, ■Since magnetic toner with relatively low resistivity is used, electrostatic transfer of the developed image on the electrostatic latent image to a support member such as plain paper is solidification, and It has disadvantages such as insufficient transfer in an atmosphere, and (2) 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 that does not contain magnetic powder and has a high specific resistance has been attracting particular attention.

Such developing methods include, for example, US Pat. No. 2,895
No. 847, No. 3,152,012, Special Publication No. 41-9
Examples include methods based on the touchdown method, impression method, and jumping method described in No. 475, No. 45-2877, and No. 54-3624. These methods utilize conventional toners used in two-component systems.

However, in this case, various problems associated with the -component system are unavoidable, as described below.

The first problem is the triboelectrification problem.

In other words, the developer must efficiently interact with the developer carrier and obtain the amount of charge necessary to visualize the electrostatic latent image formed on the photoreceptor drum or dielectric material in a very short time without contact. . However, when a selenium photoreceptor drum is used, the amount of charge required by the developer and the developer carrier to visualize the image is -0.5 to 15 μC/p.
It is.

However, using a developer used in a conventional two-component system, FA tribocharging using a developer carrier and the developer does not provide a sufficient amount of charge to visualize the image.

The reason for this is that developers used in conventional two-component systems require sufficient time to triboelectrically charge the toner and carrier to obtain the amount of charge necessary to form a visible image. There is.

However, if the amount of charge is high, it may cause background fogging, so
Two-component developer band 1! The amount is controlled.

Conventional two-component developers are mainly composed of γ1 resin, which exhibits small condensation under charging power, and by adding a charge control agent, IF
i amount is controlled.

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

According to experiments, as shown in FIG. 2, the amount of charge of the A6 binder resin (blow-off method) is proportional to the acid value of the binder resin (measured by the KOH method). As is clear from Figure 2, a binder resin with a low acid value also has a low charge amount. Generally, the charge amount by the blow-off method of a two-component developer is 10 to 30 μC/
It is y.

Further, FIG. 3 shows 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.

As is clear from FIG. 3, in the two-component developer, a sufficient amount of charge to form a visible image cannot be obtained by frictional charging between the developer and the developer carrier.

As mentioned above, to date, no developer has been developed that has a sufficient amount of charge to form a visible image due to frictional charging between the developer and the developer carrier.

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

That is, for the developing roll 1 shown in FIG.
When the elastic grade is pressed at a pressure of 1OOIZσ to z500F/m, the developer present in the developer container is
It is conveyed by the rotation of the developing roll, and is applied very thinly and evenly onto the surface of the developing roll by an elastic blade. For this reason, the developer is required to have good fluidity and agglomeration resistance.

However, although the developer present in the developer container is transported by the rotation of the developing roll, it sometimes becomes cohesive and becomes lumpy, resulting in the problem that the developer is not coated on the surface of the developing roll. There is.

In addition, the developer transported by the rotation of the developing roll is
When the elastic grade and the developing roll + i1 are brought into contact, the pressure is suddenly high, and the developer softens and sticks to the developing roll surface due to frictional heat. There is a problem in preventing the application of developer evenly. These causes include
The binder resin of the developer has a low softening point and a low glass transition point.

Furthermore, if the softening point is high,
There are problems that hinder its use in ordinary office copying machines.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and by controlling the amount of triboelectric charge of the developer, it is possible to coat the developing agent extremely thinly and uniformly on the surface of the developing roll, and to achieve high resolution with excellent fluidity and agglomeration resistance. An object of the present invention is to provide a developer capable of forming sharp visualized images.

[Key points of invention]

In the colored particles formed by dispersing a coloring agent in a binder resin, the present invention controls the amount of charge of the colored particles by controlling the amount of charge of each of the binder resin and the colorant. The main idea is to apply the above-mentioned colored particles extremely thinly and uniformly to obtain a developer that has the effect of producing sharp images with high resolution.

That is, the present invention provides a developing roll that rotates while carrying a one-component developer on its surface and develops a latent image by supplying the developer to the electrostatic latent image, and the developer gi! In order to uniformly apply the developer onto the surface of the roll, a developing device basically consisting of an elastic blade placed in pressure contact with the surface of the developing roll is used to generate a static latent image in a non-contact manner. In the developing method, 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,
It is desirable to use a developer characterized by an acid value of 10 to 40, particularly bisphenol type polynisder resin and styrene-acrylic resin.

The above-mentioned coloring agents are generally dyes, pigments, carbon black, etc., and examples of such coloring agents include nutrients such as nicrosine dyes, carmine dyes, basic dyes, acid dyes, oil dyes, and anthraquinone dyes. 5 Benzidine-based yellow organic pigment.

Gynanthrin-based organic pigments, rhodamine-based organic pigments.

Pigment-rich furnace plaques such as inorganic pigments such as tantalocyanine-based organic pigments, zinc oxide, titanium oxide, and red iron oxide, acetylene dicarbonate, thermal black, and other carbon blanks can be mentioned.

Next, a manufacturing method for obtaining the developer of the present invention will be explained below by showing an example.

First, binder resin and colorant are mixed in a ball mill, V-type mixer,
The mixture is mixed using a mixer such as a mold mixer or a Kooning blender.
The mixture is kneaded using a pressure kneader, etc., and the mixture is crushed using a crusher such as a hammer mill, jet mill, or ball mill, and the resulting powder is further classified using a sieve or air classification. Particles of a predetermined particle size (
colored particles).

In the production of these colored particles9, the type of binder resin to be used, the type of colorant to be dispersed, and the blending ratio will affect the amount of charge of the colored particles obtained, so appropriate charging should be carried out. amount is selected.

When a positively charged photosensitive drum is used, the amount of charge of the colored particles obtained from the materials selected from the above-mentioned binder resin and colorant is preferably -0.5 to 15 μC/liter.

In addition, if necessary, in order to improve the fluidity and agglomeration resistance of the developer, 0.05 to 2 parts by weight of hydrophobized colloidal fine particles having the same polarity as the colored particles may be added, which will affect the amount of charge on the colored particles. Even if it is added to the extent that it does not cause any damage, there is no problem at all.

〔Effect of the invention〕

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

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

(11) A developer can be obtained that provides efficient triboelectric charging.

(lit) UM with good fluidity and cohesiveness
An image agent is obtained.

(1v) Sharp images with high resolution can be obtained.

[Embodiments of the invention]

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

Example 1 Styrene y-acrylic resin (Mn 1 f3.300.1
14W328.000 Softening point 125℃, Glass transition point 6
1.2°G, acid value 145) and 8 parts by weight of carbon black were mixed in a ball mill for about 2 hours, and then kneaded in a pressure kneader for about 1 hour.

After cooling the mixed material, it was coarsely pulverized with a hammer mill, finely pulverized with a jet mill, and classified with a classifier to obtain color-matching particles of 5 to 25z+m. Next, 100 parts by weight of the colored particles and 0.5 parts by weight of colloidal fine particles (Aerosil 9722 manufactured by Nippon Aerosil Co., Ltd.) were mixed in a ball mill, and the colloidal fine particles were adhered to the interface of the colored particles to give a weight average of 50 kg. The developer had a particle size of 11.5-1.

The amount of charge of this developer was measured and found to be -6 BpC/f.
Met.

Using this developer, in the developing device shown in FIG.
When a visualized image was formed under the conditions of a photoreceptor drum surface potential glass of 900V and a 'gL image bias of minus 500V, the image density was 15. A good image with no ground cover was obtained with a resolution of 5 Lp/wx. Furthermore, when fixing was performed using a heat roll fixing device, fixing started at 140°C, and no offset occurred even at 210°C.

Example 2 Bisphenol type polyester [fat (Mn 4, 100°MW 32.000. Softening point 135°C, glass transition point 78
．． 5℃.

After dispersing 92 parts by weight of acid value 20.2 and 8 parts by weight of carbon black in a ball mill for 2 hours, 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 the colloid fine particles were attached to the surface of the colored particles in the same manner as in Example 1.
A developer having a 0% weighted average particle size of 13.1 μm was used.

When a visualized image was formed under the same conditions as in Example 1, in which the charge amount of the developer was -9.5/lC/f, the image density was 1.51, and the resolution was 5.6 tp/IM. No good images were obtained.

Also, fixing starts from 150℃, and 140" from 0 to 220℃
No offset occurred.

Example 3 Bisphenol type polyester resin (softening point (R&B method) 135°C, glass transition point 81.2°C, acid value 35) 92
After dispersing and mixing parts by weight and 8 parts by gravity of carbon black,
Colored particles were obtained in the same manner as in Example 1, and 100 parts by weight of colored particles and 0.8 parts by weight of colloidal fine particles were used in the same manner as in Example 1 to prepare a developer. The 50% weight average particle diameter of this developer was 11.8 μm, and the charge amount was -13.6 μC/f.A visible image was formed in the same manner as in Example 1, and the image density was 1.4. A good image with a resolution of 5 L and 97 m without background fog was obtained, and fixing started from 160°C and from 140°C to 2
I wanted an offset to occur at 20°C.

Comparative Examples 1 to 3 Using binder resins with different softening points, glass transition points, and acid values,
Similar to Example 1, 92 parts by weight of binder resin.

After dispersing and mixing 8 parts by weight of carbon black, a developer was obtained.

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

Gray day

[Brief Description of the Drawings] Fig. 1 is a schematic diagram showing an example of the developing device used in the present invention, and Fig. 2 is a characteristic showing the relationship between the acid value of the binder resin and the amount of charge determined by the developer pull-off method. 3 are characteristic diagrams showing the relationship between the amount of charge obtained by the developer blow-off method and the amount of charge obtained by the development method shown in FIG. 1. 1 Developing roll 20 Elastic blade 3 Developer container 4 Developer 5, Photoreceptor drum 6
．． Rigid Gold Layer Piece 7 Side Wall Agent Patent Attorney Nori Chika Gusuke (and 1 other person) Figure 1, Figure 2 Figure 2 Laughter I Nishi

Claims (4)

[Claims] (1) A developing roll that carries a one-component developer on its surface and rotates to develop the latent image by supplying the developer to the electrostatic latent image, and the developer is uniformly distributed on the surface of the developing roll. A developing agent used in a method for non-contact developing an electrostatic latent image using a developing device basically consisting of an elastic blade disposed so as to come into pressure contact with the surface of the developing roll. A developer characterized in that 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 40. (2) The developer according to claim 1, wherein 0.05 to 2 parts by weight of colloidal silica is added to the developer. (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 a styrene/acrylic resin.