JPH02158748A - Toner for developing electrostatic image - Google Patents

Abstract

PURPOSE:To obtain a durable toner for developing electrostatic images without impairing releasing effect by mixing two kinds of toner having different particle size to each other and having a same compsn. except either one among the kind, mol.wt., or mixing ratio of release agents. CONSTITUTION:Two kinds of toner having different average particle size to each other are mixed, wherein the toners contain respectively, a resin compo nent, a colorant component, and release agent components having a same compsn. except either one among the kind of the release agent, mol. wt., and mixing ratio of the release agent. Preferably, a toner having a small particle size and being difficultly puverizable is mixed with a toner having a large particle size and releasing effect. A content of the release agent for the toner having a small particle size is arranged to be less than the content of the release agent for the toner having a larger particle size or a resin consisting of a re lease agent having a larger mol. wt. is used. Thus, a toner to be used for devel opment of electrostatic image which is difficultly pulverizable even after it is used repeatedly for a long time, is obtd. by using a release agent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a toner for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, and the like.

[Prior Art] In the process of developing an electrostatic image, charged fine particles are attracted by electrostatic attraction and attached to the surface of an electrostatic image support.
This is the process of visualizing the electrostatic charge image.

The specific method for carrying out such a developing process is as follows:
A wet development method using a liquid developer in which pigments or dyes are finely dispersed in an insulating organic liquid, and a powder consisting of a toner in which a coloring agent such as carbon black is dispersed in a binder made of a natural or synthetic resin. There are dry developing methods such as a cascade method, a bristle brush method, a magnetic brush method, and a powder cloud method that use a body developer.

The image visualized in the developing step may be fixed on the support as it is, but usually it is transferred to another support such as transfer paper and then fixed.

In this way, toner is not only subjected to a developing process, but also to further processes, that is, a transfer process and a fixing process, so toner has not only good developability but also It is required to have good transfer and fixing properties. Among these, the conditions related to fixing properties are one of the most severe, and many studies and results have been published in the literature regarding improving the fixing properties of toners.

It is generally advantageous to fix the toner image formed in the developing process or the image transferred thereto by a heat fixing method. There are contact heating fixing methods such as

The contact heating fixing method is excellent in that it has high thermal efficiency, and in particular, it is capable of high-speed centering and is suitable for fixing high-speed copy paper. Furthermore, since a relatively low-temperature heat source can be used, this method requires less power consumption, making it possible to downsize the copying machine and save energy. Furthermore, there is no risk of fire even if paper remains in the fixing device, which is also preferable.

However, in this method, the surface of the fixing roller and the toner image come into pressure contact in a heated and molten state, so a part of the toner image adheres to the surface of the fixing roller and is transferred, and then transferred again onto the next sheet to be fixed, so-called This may cause an offset phenomenon and stain the sheet to be fixed.

Therefore, preventing toner from adhering to the roller surface is considered to be one of the essential requirements in the fixed heating roller deposition method.

Conventionally, in order to prevent toner from adhering to the surface of the fixing roller, for example, the roller surface was made of a material with excellent release properties against toner, such as fluorine-based resin, and an offset prevention liquid such as silicone oil was further applied to the surface. The roller surface is coated with a thin film of liquid.

Although this method is extremely effective in preventing toner offset, it generates an odor due to heating of the offset prevention liquid and requires a device to supply the offset prevention liquid. The mechanism of the copying device becomes complicated, and high accuracy is required in order to obtain an image with good negativity, resulting in a disadvantage that the copying device becomes expensive.

In order to improve these drawbacks, toners containing release agents such as polypropylene and paraffin wax that have a release effect (JP-A-49-85231, JP-A-5O) have been developed.
-2H40) has been proposed.

[Problem to be solved by the invention]

However, polypropylene and paraffin wax have poor compatibility with binder resins, and when these mold release agents are used, they have the disadvantage that toner tends to be crushed when used repeatedly inside a machine. As the toner is pulverized inside the machine, it tends to fuse to the surface of the carrier, resulting in so-called spent toner, resulting in a decrease in the amount of charge of the two-component developer. - In the case of the component process, the toner is fused to the sleeve surface, and in this case, the amount of charge similarly decreases. If the amount of charge decreases, image fogging and toner scattering become more likely to occur, reducing the reliability of the copying system. Therefore, the present invention has developed a toner that is resistant to pulverization even when using a release agent or repeatedly used for a long period of time, is resistant to shattering on the carrier surface and the sleeve surface of a one-component process, and is resistant to image fogging and toner scattering. It provides:

[Means for Solving the Problems] The first invention of the present invention includes a resin component, a colorant component, and M
In a toner formed by mixing two types of toners containing a molding agent component, the two types have the same composition except for the type of mold release agent, molecular mouth, and blending ratio, and have different average particle sizes. This patented image developing toner is characterized in that it is a mixture of toners.

Further, the second invention is characterized in that when the same type of release agent is used in two types of toners, the large particle size toner contains more and the small particle size toner contains less.

Furthermore, in the third invention, when using the same type of release agent for two types of toners and changing their molecular weights, the small particle size toner contains one with a large molecular weight, and the large particle size toner contains one with a small molecular weight. It is characterized by the fact that

As a result of research, the present inventor investigated the particle size of the toner forming the above-mentioned spent toner, and found that toner with a particle size of 2 μm or less is particularly likely to be fused. This is attributable to the fact that toner with a small particle size has a small heat capacity and is more fused to the container than a toner with a large particle size.

When the developer is stirred inside the machine for a long time, the relatively small particle diameter of about 5 μm in the toner becomes finely powdered, and the toner becomes finely divided into particles of 2 μm.
It was found that these toners tend to form fine particles on the order of m, and these toners are most likely to be spent. Therefore, in order to prevent the generation of fine powder by stirring, it is necessary to design the product so that it does not cause pulverization. The pulverizability of toner is determined by the compatibility of the resins, and the better the compatibility, the more difficult it is to be pulverized.

The binder resin and low molecular weight polypropylene or paraffin wax have poor compatibility, and in order to improve the compatibility, the amount of polypropylene, wax, etc. can be reduced or the molecular weight can be increased.

However, although increasing the molecular weight of polypropylene and wax improves compatibility and makes the toner less likely to shatter, i! The type iI effect is reduced. In order to achieve both the M-type effect and the toner's resistance to crushing, it is sufficient to mix a toner with a small particle size that is difficult to crush and a toner with a large particle size that is releasable. Specifically, for small particle size toners, the number of release agents is reduced compared to large particle size toners, or a resin with a high molecular weight for the release agent is used. The particle size of small particle toner is 2~
The particle diameter is preferably 10 μm, and the particle size range of 8 to 25 μrn is preferable for large particle size toner. The mixing ratio of the releasing agent and the two types of toners having different molecular weights is preferably determined according to the number of copies per hour of the designed copying machine.

That is, in a machine that produces a large number of copies per hour, a large amount of heat is generated in the developing machine, and the toner is likely to be crushed, so it is desirable to use a large amount of small-particle-sized toner that is less likely to be crushed. Conventionally, when trying to use one type of toner to support copying machines that make a small number of copies to those that make a large number of copies, the toner tends to be crushed in machines with high copying speeds, making it difficult to extend the service life.

In the present invention, by mixing two types of toners with different types of release agents, molecular weights, and blending ratios, it can be used for copying machines with a small number of copies to those with a large number of copies.
This can be handled efficiently by changing only the mixing ratio.

The mold release agent used in the present invention includes the above-mentioned polypropylene,
In addition to paraffin wax, polyalkylene fatty acid metal salts, fatty acid esters, saponified fatty acid esters, higher fatty acids, higher alcohols, polyhydric alcohol esters, fatty acid amides, etc. may be used. The release agent used for the large particle size toner and the toner used for the small particle size may be the same release agent or different types of release agents. Also, when using the same type of release agent, add more to large particle size toner and less to small particle size toner. Furthermore, when changing the molecular weight of the release agent, one with a large molecular weight is used for small particle diameter toners and one with a small molecular weight is used for large particle diameter toners.

Depending on the mixing ratio of the small particle size toner and the large particle size toner, a resin that does not use a release agent may be used for the small particle size toner.

The toner used in the present invention is produced by a conventional toner production method. That is, a colorant, a binder resin, and a mold release agent are kneaded using a two-roll roller or the like, and then pulverized using a jet pulverizer or the like. The finely pulverized product thus obtained is made into a desired particle size in a classification step, and then blended with a similarly prepared toner having a different release agent and a different particle size using a mixer such as a Henschel mixer.

In addition to the coloring agent, binder resin, and mold release agent, a commonly used antistatic agent may be added to control charging during crosstalk. The main antistatic agents include nigrosine dyes, quaternary ammonium salts, metal complex salts, triphenylmethane dyes, etc.
More than one type may be mixed.

In addition, due to the flowability of toner -L, when mixing two types of toner, silica, titanium dioxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, etc. Fine silica powder, silicate, silicon carbide, silicon nitride and their use as silane coupling agents, titanium coupling agents,
Fine powder made hydrophobic with silicone oil or the like may be added.

Styrene resins are mainly used as the binder resin according to the present invention, and the styrene resins include styrene homopolymers and copolymers of styrene and other vinyl monomers. Other vinyl monomers include ethylenically unsaturated monoolefins such as ethylene, propylene, and imbutylene; vinyl halides such as vinyl chloride, vinyl bromide, and vinyl fluoride; vinyl esters such as vinyl acetate; acrylic acid Acrylic acid esters such as methyl, ethyl acrylate, and phenyl acrylate; Vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; Vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone; N-vinylpyrrole, N-vinylpyrrolidone, etc. One or more of the following N-vinyl compounds; acrylonitrile; methacrylonitrile; acrylamide; and methacrylonitrile are used.

Further, as resins other than styrene resins, polyester resins, rosin-modified phenol-formalin resins, epoxy resins, and mixtures thereof are used.

As the toner coloring agent according to the present invention, carbon black, nigrosine dye (C,l No.

50415B), Aniline Blue (C, INo, 5
0405), Calco Oil Blue (C, lNo, azo
ac Blue 3) s Chrome Yellow (C, INo
, 14090), ultramarine blue (C, lNo,
77103), DuPont Oil Red (C, INo, 2
B105), quinoline Ie o-(e, lNo.

47005), methylene blue chloride (C, INO
.

52015), phthalocyanine blue (C, lNo., 7
4180), malachite green off-sale (C, I
No.

42000), lamp black (C, INo, 7726)
6), Rose Bengal (C, INo. 45435), mixtures thereof, and others. It is necessary that this colorant is contained in a sufficient proportion so that a sufficient visible image is formed by development, and it is usually preferably contained in a proportion of 1 to 20 parts by weight per 100 parts by weight of the binder resin.

Further, the toner of the present invention can be used in both a dry type developer and a two-component developer.
Alloys containing ferromagnetic elements such as cobalt and nickel, or alloys that do not contain compounds or ferromagnetic elements but become ferromagnetic through appropriate heat treatment.
For example, manganese-copper-aluminum or manganese-
Examples include alloys called Heusler alloys containing manganese and copper, such as copper-tin, and chromium dioxide.

The magnetic material is uniformly dispersed in the binder resin in the form of fine powder with an average particle size of 0.3 to 30 microns. Content of magnetic particles:
L is preferably 20 to 70 parts by weight, preferably 40 to 70 parts by weight, per 100 parts by weight of toner.

The toner compositions of the present invention are made by any known toner mixing and grinding method. For example, all components are blended in predetermined amounts, mixed and pulverized to thoroughly mix all components, and then the resulting mixture is pulverized.

Another known method of forming toner powders involves ball milling the colorant, resin, and solvent and spray drying the toner formulation mixture.

In order to use the toner composition according to the present invention by a magnetic brush development method, etc., the composition preferably has a carrier weight percentage of 0.5 to 7%.

Coated and uncoated carriers, such as those used in magnetic brush development, are well known, but the carrier particles are in close contact with the toner powder so that the toner powder adheres to and surrounds the carrier particles. The carrier particles may be formed of any suitable material so long as the toner powder acquires a charge of opposite polarity to that of the carrier particles when applied. Accordingly, toner compositions of the present invention can be used with any suitable electrostatic/electrostatic surface including conventional photoconductive surfaces.
14 is used in admixture with conventional carriers to develop electrostatic latent images on imaged surfaces.

[Example] The present invention will be described below with reference to Examples and Comparative Examples. Note that parts are parts by weight.

Example 1 Carbon black 10 parts Picolastic D-125 (Styrenic resin manufactured by Esso Ishiura Chemical Co., Ltd.) 100 parts Nigrosine Base EX (manufactured by Orient Chemical Co., Ltd.) 5 parts Polypropylene (BfiOp manufactured by Sanyo Chemical Co., Ltd.) 5 parts using a hot roll Knead, cool and grind to an average diameter of about 15
A toner having a white μ (number content of particles having a particle size distribution of 8 μ or less: 0%) was prepared and used as a large particle toner.

Separately, a toner having an average particle size of 5 μm (number content of 15 μm or more in particle size distribution: 0%) was prepared in exactly the same manner as described above, except that the opening of polypropylene was changed to 2 parts, and a small particle toner was prepared. The large particle toner and the small particle toner were blended in a Henschel mixer at a ratio of 3 to 1 to form a toner of Example 1.

The toner is made using the same manufacturing method as the toner formulation described above,
At the time of classification, a toner with an i72 uniform diameter μ was obtained and used as a comparative toner. (This toner is not a mixture of small particle size and large particle size.) 4 parts of these toners are mixed with 9B part of iron powder carrier each having an average particle size of 50 to 60 microns to form two types of toner. After preparing a developer and developing an electrostatic image formed by ordinary electrophotography using these developers, the toner image is transferred and the surface is coated with FEP (tetrafluoroethylene and hexafluoroethylene manufactured by Du Bonn). 19 using a fixing roller made of a copolymer with propylene)
Pressure contact is carried out at 0 to 200°C to fuse the toner image,
It took hold.

Next, in order to investigate whether the fused toner image is transferred to the surface of the fixing roller and offset development occurs, after each fixing operation, transfer paper without toner image is fixed under the same conditions as above. The transfer paper was brought into pressure contact with a roller, and stains caused by toner offset were observed on the transfer paper.

As a result, both the Example toner and the Comparative Example toner had good offset. Apply this toner to the copying machine FT41!2 (
When 10,000 copies were made using + (manufactured by Ricoh), in this example there was no decrease in band ff1ffi and there was no toner scattering, but in the comparative example, the charge amount decreased significantly and there was a lot of toner scattering. . When comparing the particle sizes, the particle size of the comparative example was smaller, and when the carrier surface was observed with an electron microscope, more suventor was observed in the comparative example than in the inventive one. .

Similarly to Example 1, Examples 2 and below were tested and the results were tabulated as follows.

[Effects of the Invention] The present invention provides a toner for developing electrostatic images containing a resin, a colorant, and an M-type agent, in which the fine powder component is composed of a toner that is difficult to crush, and the coarse powder component is a toner that has a releasing effect. As a result, a durable toner can be obtained without impairing the release effect.

Claims (3)

[Claims] (1) A toner made by mixing two types of toner each containing a resin component, a colorant component, and a release agent component, which have the same composition except for the type, molecular weight, and blending ratio of the release agent. A toner for developing an electrostatic image, characterized in that the toner is a mixture of two types of toner having different average particle diameters. (2) In a toner made by mixing two types of toner each containing a resin component, a colorant component, and a release agent component, when using the same type of release agent for both toners, use the release agent in large particles. A toner for developing an electrostatic image, characterized in that it is contained in a large amount in a toner with a small particle size and a small amount in a toner with a small particle size. (3) In a toner made by mixing two types of toner each containing a resin component, a colorant component, and a release agent component, when using the same type of release agent for both toners and changing the molecular weight, the particle size is small. 1. A toner for developing an electrostatic image, characterized in that a toner with a large particle size contains a toner with a large molecular weight, and a toner with a large particle size contains a toner with a small molecular weight.