JPS6038699B2 - electrostatic image developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry developer for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, etc.

Various methods for forming electrostatic images and developing methods for the images are well known. The method of forming an electrostatic image is described in detail in, for example, US Pat. No. 2,297,691 by C.F. Carlson, and the developing method is described in detail by E.N. Cascade development method proposed by Wise, US Patent No. 2
A typical example is the magnetic brush development method described in specification No. 874063. Furthermore, U.S. Patent No. 28993
Many methods have been proposed, such as the liquid development method described in No. 35, the C-shell development method, the fur brush development method, the touchdown development method, the impression method, and the powder cloud method. In these developing methods, the electrical properties of the developer are a very important issue.

For example, the efficiency with which toner separates from the developer mixture and develops the static exposure latent image on the photoreceptor, ``the efficiency with which the toner is transferred to paper, etc.''
Emphasis is placed on charging stability sufficient to withstand repeated use, longevity, and stability against the environment, especially temperature and humidity. In general, a dry developer is formed from a carrier of metal such as iron, glass, or other inorganic compound particles, particles coated with an organic polymer, and colored fine particles called toner. Furthermore, in some cases, a third agent may be used in addition to these carriers and toners.
Components may also be added. Toner particles are typically
It uses natural or synthetic resin as a binder, and contains colorants, charge control agents, other additives, etc.

A highly insulating polymer is generally used as the secondary binder resin. Among them, vinyl-based polymers, mainly styrene-based copolymers, fully satisfy toner properties other than electrical properties, such as manufacturability, storage stability, and fixing properties, and can also withstand repeated use as a developer. It is most commonly used because it has sufficient mechanical strength and is less likely to contaminate the carrier surface. Furthermore, in order to adjust the charge polarity and charge amount of the toner, it is conventional to mix dyes, pigments, and surfactants into the binder resin, or to introduce electron-donating or electron-withdrawing functional groups into the resin itself. However, the binder as a whole maintains high insulation properties.
Toner made of such a high-edge supply binder exhibits good triboelectric charging properties due to its high insulation properties, but the efficiency of development, transfer, etc. is slightly inferior, and a larger amount of toner is required to obtain a specified image density. It has the disadvantage that

This is particularly noticeable when combined with a carrier having an inorganic compound surface such as iron oxide. Furthermore, this problem is more noticeable in developer systems in which additives such as fatty acid metal salts, silica, and other additives commonly known as lubricants and mold release agents are added as third components in addition to carriers and toners. In this case, the amount of toner consumed usually tends to increase each time development is repeated, which tends to eventually result in poor image quality such as staining of the device and fogging. This is a particularly serious drawback in the case of high-speed copying machines. The inventors of the present invention have discovered that this drawback of conventional developers is due to the toner having an unnecessarily high insulating property, and that this can be significantly improved by controlling this insulating property.

Therefore, an object of the present invention is to use a polymer with lower insulating properties as a binder than conventional binder polymers, thereby improving development efficiency without adversely affecting triboelectric charging properties.
An object of the present invention is to provide a developer with significantly improved transfer efficiency.

Another object of the invention is to provide an environmentally stable developer.

Still another object of the present invention is to provide a developer that consistently exhibits stable development and transfer properties even after repeated development.

Still another object of the present invention is to provide a long-life developer that does not deteriorate over a long period of time even when applied to high-speed copying machines.

Still another object of the present invention is to provide a developer composition with consistent quality and stable quality.

The above purpose is for volume resistivity (abbreviated as p) to be 1 and 60.
This can be achieved by using a low resistance insulating polymer below the skin level as a binder in the toner. Electrical properties such as conductivity of polymeric materials have not yet been theoretically fully elucidated, but generally polymer electrolytes and polymers having polar groups tend to exhibit low p.

1 with such polar polymers. ≦p≦1 and 60 Contains a skin-indicating polymer material in an amount of 1% by weight or more based on the total amount of binder polymer, and 1 as the total binder polymer and as the final toner.
and 2≦p≦1 and 60, preferably 5×1 and 3≦p≦
When adjusted to be 5 × 1 and 50 arcs, the conventional p
>1 and 60・It was found that the developability, transferability, lifespan, and stability over time were significantly improved compared to toners made of highly insulating polymers without changing triboelectric charging properties. Taゞp<
Polymers exhibiting 1 pioQ·arc are too sensitive to humidity and are therefore undesirable. Similarly, if the polymer binder and toner have p<1 or 20 arc, triboelectric charging will not be stable and it will be susceptible to environmental conditions, which is not very practical. 1 and o≦p≦1 and 60・arc polymer (hereinafter referred to as low p
There is no problem when using the polymer (abbreviated as polymer) alone, but when using it in combination with other highly insulating polymers, it is desirable to contain the low p polymer at 3% by weight or more if possible. . Furthermore, the component polymers to be mixed must have good compatibility, for example, the difference in solubility parameters is 0.6 [cal' flow] or less, or they can be mixed by appropriate means. It is preferable to disperse and mix as uniformly as possible. If the low p polymer is poorly dispersed or has a low concentration, it is difficult to effectively lower the resistance, and furthermore, the charge tends to fluctuate greatly. If the charging is moderately varied and the toner has a moderately wide charge distribution, solid black image reproduction will be good, but control is difficult and impractical. by the way,
Generally, when a polymer having a polar group is used, the position of the toner on the triboelectric series changes, and the charging electrode of the developer and the amount of charge can be controlled.

In other words, when an electron-donating polar group is introduced into a structure, it moves to the (10) side of the charge chain compared to the structure before introduction, and when an electron-withdrawing polar group is introduced, it moves to the (1) side. It has been known. For example, Hakamako No. 44-17074 discloses that an oligomer into which a polar group consisting of one NH2, one OH, and one COO is introduced is used as a binder for a positive polarity toner.
It is stated that an oligomer into which a suitable group consisting of -N02 and halogen is introduced is used as a negative polarity toner. In this way, it has been done to change the position on the charging array and change the amount of charge on the developer without changing the high edge supply property of the toner, but the purpose and effect of the present invention are completely different from these known findings. to be different. The present invention is characterized in that development is performed using a toner with a lower p than conventional toners, and it is essential to lower the p of the binder polymer and toner to below 1 to 60.

Furthermore, the amount of charge should not be too large or too small. That is, it is often rather inconvenient that the position of the toner on the electrification series changes greatly. In general, many highly polar polymers are strongly affected by environmental conditions, especially humidity.

Therefore, it is necessary to carefully select the type and concentration of the gutter group. If a large amount of hydrophilic functional groups are introduced, problems will arise in the humidity stability of the developer. Examples of polar groups effective for lowering p include -NR2, S03R, -OR,
1COOR, 8, 1N02, 1CN, 1X (R is a hydrogen atom, an alkyl group which may have a substituent, an aryl group, etc., and X represents a halogen atom.

), but in the present invention, the main objective is to lower p to 1 to 60.0 cm or less, and is not limited to the polar groups exemplified above. Furthermore, since the purpose is not to change the position on the charge series, it is also effective to introduce both an electron-donating group and an electron-withdrawing group into the molecular chain. In addition, it is possible to introduce heteroatoms and polar groups into the main chain itself or into the side chains, but in order to satisfy toner fixing properties and other aspects, it is better to introduce them into the side chains. desirable. Polar groups can be introduced by polymerizing monomers having polar groups or by modifying polymers, but the former method is easier to control the sacrificial group concentration. In particular, in order to satisfy all of the mechanical properties, thermal properties, etc. required for a toner in addition to the electrical properties of the toner, which is the main focus of the present invention, it is preferable to use two or more types of monopolymers rather than using a homopolymer. It is most desirable to use copolymers consisting of mercury as low p polymers. Electrical properties of main polymers are described, for example, in Polymer Handbook, 2nd Edition (published by Wiley Interscience). As a method of lowering the p of the binder polymer, it is possible to mix a beam, a pigment, a surfactant, etc., which are usually used as a charge control agent, or a metal-based conductive powder, etc.

It is true that these are mixed into the binder polymer and p≦1 and 6.
Although it is possible to obtain a zero arc, these materials generally lack dispersion stability and are unstable over time and the environment, and the excellent results obtained using the low p polymer in the present invention are difficult to achieve. I can't really get it. As binder polymers, particularly for toners for high-speed copying machines, pinyl-based polymers, especially styrene-based polymers, which are advantageous for heat and pressure fixing, are generally used.

Polystyrene is an extremely highly insulating polymer (some literature states that p>1 and 70), and the present invention is very effective for styrene toners. When the styrene-based toner is made p≦1 and 60/skin using the above-mentioned method, it is possible to improve development, transferability, lifespan, stability over time, etc. without impairing fixability, manufacturability, storage, environmental stability, triboelectric chargeability, etc. greatly improve. In this case, toner fixability, manufacturability, storage stability,
In order to sufficiently guarantee the service life, etc., the styrene content must be 20%.
As mentioned above, preferably 40% or more of the styrene copolymer is desirable. The low-resistance insulating toner of the present invention also effectively improves the developability of carrier particles whose surfaces are coated with an organic polymer or the like. However, when silk is combined with a carrier having an inorganic surface with a high dielectric constant, such as iron powder or iron oxide powder, development, transferability, lifespan, etc. are greatly improved.
Furthermore, it has been found that the low resistance insulating polymer according to the present invention is most effective for systems in which a third component is added in addition to the carrier and toner.

In this case, the third component generally improves the fluidity, charging, developability, and transferability of the developer, prevents deterioration of the developer, improves storage stability, improves the cleanability of the photoreceptor, and in some cases, improves the fixing property. It is an organic or inorganic substance added to the developer in addition to the usual carrier and toner particles in order to improve the toner particles. These substances are appropriately selected according to the various purposes mentioned above, but commonly used are long chain fatty acids such as stearic acid, their esters, amides, metal salts with copper, zinc, etc., and characteristic powders such as paraffin. , molybdenum disulfide, graphite, graphite fluoride,
These include boron nitride, fluorine-based resin fine powder, other crosslinked or non-crosslinked resin powder, hydrophobic silica powder, extender pigments, etc., and although their physical properties cannot necessarily be limited, they usually have a critical surface tension of 3.
They are solid fine particles smaller than toner particles that have a low surface energy equal to or less than the surface of a toner, or have a smooth surface with a coefficient of friction of 0.1 or less. Conventionally, when one or more of these third components are added to a developer, the developer naturally exhibits complicated charging behavior and affects its electrical properties. There is also a problem that there is a difference between the initial developability and the developability after long-term use, resulting in variations in the developability. However, when used in combination with the low resistance insulating toner of the present invention,
Such problems have been resolved. It is presumed that these results are due to the fact that the charging time constant changes due to the lower p of the toner, and a balance between power generation and charge decay is achieved, so that excess charge is not accumulated more than necessary.

The amount of these third components added is 0.0 based on the weight of the toner.
1 to 10% by weight, preferably 0.05 to 5% by weight, and preferred third components are hydrophobic powdered silica and long chain fatty acid metal salts such as stearic acid, zinc, cadmium stearate, barium stearate, stearic acid. Lead, iron stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, calcium stearate, cadmium stearate,
Magnesium stearate, zinc oleate, magnesium oleate, iron oleate, cobalt oleate,
Copper oleate, lead oleate, magnesium oleate, zinc palmitate, cobalt palmitate, copper palmitate, magnesium palmitate, aluminum palmitate, calcium palmitate, lead caprylate, lead caproate, zinc linoleate, linoleic acid Cobalt, calcium linoleate, zinc ricinoleate, cadmium ricinoleate and mixtures thereof.

These hydrophobic powdered silica and long-chain fatty acid metal salts are used for the above-mentioned purposes, in particular, to prevent deterioration of the developer (toner), to favorably control the coefficient of friction on the surface of the sensitive material, and to improve the surface of the sensitive material. This has effects such as being able to prevent toner filming, and is particularly preferred in the present invention. Furthermore, in the present invention, the binder polymer has a glass transition temperature or melting point of 30 to 10 degrees, preferably 4 degrees, in order to satisfy fixing properties, storage stability, etc.
The temperature is 0° C. to 70° C., and particularly when heat-pressure fixing is performed, the weight average molecular weight is preferably 3000 or more, and the molecular weight is preferably high enough to have a fixing temperature range of 0 or more per coat.

The constituent components of the binder material are not particularly limited, and other well-known additives may be added in order to further improve developability, fixability, manufacturability, storage stability, and the like.

It is also possible to mix magnetic powder or the like into the binder. To produce the toner of the present invention, the binder polymer, colorant, and other additives are melted and kneaded using a Banbury mixer or the like.
After cooling, it may be pulverized by jet pulverization or the like to form a fine powder.

The particle size is preferably about 1 to 30 F. Or,
Further, it may be manufactured by a spray drying method, a direct polymerization method in which fine powder toner particles are directly polymerized from a suspension containing a monomer, a colorant, etc., or a dispersion granulation method. In particular, when the toner composition is turned into particles after going through a solution state, it is also possible to take advantage of the phase separation of the toner composition to selectively provide a low p polymer layer on the surface of the toner particles to form microcapsules. be. In this case, block copolymers, graft copolymers, polyblend compositions, etc. may be used. In this way, only the toner particle surface layer has p≦1 and 6.
○・Even in the case of skin, the entire toner particle has p≦1 and 60・
It is possible to obtain almost the same effect as when using an arc. The present invention is characterized by the use of a low-p polymer in which p≦1 and 60.ga, and an outline of its measurement method will be described below.

First, a pressure of 400 k9' was applied to the polymer powder or toner powder to prepare a disk-shaped sample with a thickness of 2 layers and a diameter of 5 ribs.

(In some cases, hot press molding or solvent cast molding may also be used.) The sample is sandwiched between the electrodes, and
A DC voltage of 500 V was applied and the resistance value was read after 1 minute and converted to volume resistivity p. Measurement environment is temperature 25±
Measurements were repeated several times and the average value was taken at 1°C and relative humidity of 55% soil. For details regarding measurements, please refer to ASTMD-
257, and the present inventor also follows that method. Volume resistivity can be easily measured, so
The inventor chose this p as a defined parameter in the present invention.

However, in general, volume resistivity, surface resistivity, dielectric constant,
It is thought that there is a correlation between dielectric loss, and it is also possible to make similar regulations using these other parameters. Examples and comparative examples of the present invention are shown below, but the present invention is of course not limited to these examples.

Comparative Example 1 60 parts by weight of styrene monomer (hereinafter simply referred to as "parts"), 9 parts of a copolymer consisting of 4 parts of butyl methacrylate, and carbon black (product name: Mitsubishi MA600) as a coloring agent.
) was added thereto, melted and kneaded for 10 minutes, cooled and crushed to obtain a negative polarity toner having an average particle size of 12 to 17 microns.

A developer was prepared using this toner and iron oxide powder with an average particle size of 100 microns as a carrier, and Xerox 4000 and 3
When copies were made with a 10-group summer photographic machine, the toner concentration was 1.5 to 2.0% by weight (hereinafter simply abbreviated as %) for up to several hundred copies.

) to obtain the specified image density. However, after 1,000 copies, a toner density of 2.0% or more is required to obtain the same image density, and after 10,000 copies, a toner density of 2.0% or more is required to reproduce the specified image density. A toner concentration of 2.5% was required. Dirt inside the developing machine and fogging in non-image areas on copies became noticeable after 10,000 copies were made. When the p of the toner was measured using the method described above, it was 5×1.
and 60. showed an enemy. Comparative Example 2 In addition to 10 parts of the toner of Comparative Example 1, 0.3 parts of zinc stearate and 0 parts of silica powder (manufactured by Nippon Aerosil) were added.
．． A developer was prepared using iron oxide powder with an average particle size of 100 microns as a carrier.

This developer was used in cascade development and magnetic brush development in the same manner as in Comparative Example 1 to obtain copies using Xerox 4000 and 3103 summer printers. In both cases, the toner density was approximately 2.0% until the first few hundred copies, and the standard image density was obtained.
After 1,000 copies were exceeded, more toner was required to reproduce the same image density, and after 10,000 copies, a toner density of 3.5 to 4.0% was required. The stains inside the machine and on the copied images were more noticeable than when hundreds of copies were made. Example 1 Styrene 6 base, 1 $ part of acrylic acid dimethylaminomethyl ester, chlorine.

20 parts of ethyl vinyl ether and 4 parts of butyl methacrylate were added with benzene using azobisisobutyronitrile as an initiator, and polymerization was carried out by heating at about 80°C for 2 hours in a glass parable flask. After drying the obtained copolymer in a vacuum dryer, one layer of carbon black was added to the copolymer 9, and the mixture was melt-kneaded and pulverized to prepare a negative polarity toner having an average particle size of 15 microns. This toner 1
0.00 parts, additionally 0.00 parts of zinc stearate. Xerox 31
I tested it with a 0-degree camera. When this developer was used, the toner density required to obtain the specified image density from the first copy to the 100,000th copy was constant at approximately 1.2 to 1.8%, and there was always fog in non-image areas. A very clear copy image was obtained.

When the p value of the toner was measured, it showed 2×1 and 50×skin. It is thought that development, transfer efficiency, and lifespan were significantly improved because the resistance of the toner was lower than in the comparative example. Example 2 3 parts of a copolymer consisting of 6 parts of styrene, 4 parts of butyl methacrylate, and 5 parts of a copolymer of 3 parts of styrene, 2 parts of glycidyl methacrylate, and 2 parts of butyl methacrylate 'Ko, Carbon Black (Product name: Fupen 5
250) Add 1 anchor part, knead the molten mud, and then crush to obtain an average particle size of 1
A 5 micron toner was obtained.

Zinc stearate and silica powder were added to this in the same manner as in Example 1, and copies were made using a Xerox 400 summer copying machine using iron oxide powder with an average particle size of 100 microns as a carrier. Even after 100,000 copies, the toner density was 0. 7~
A clear specified image density was obtained at 1.1%. Also, at this point, almost no deterioration of the developer was observed. toner p
When measured, it showed 9 x 1 and 40. Furthermore, when the p of the styrene glycidyl methacrylate/butyl methacrylate copolymer was measured, it was found to be 4 x 1 and 40. Example 3 4 parts of a copolymer consisting of 4 parts of styrene, 1 part of 2-hydroxyethyl methacrylate, 2 parts of 2-ethylhexyl methacrylate, and 5 parts of polyester (manufactured by Toyobo, trade name: Vylon GV-200) and 1 part of carbon black (trade name: Raven 5250) were added, thoroughly melted and kneaded, and then ground to obtain a toner with an average particle size of 15 microns.

Claims (1)

[Scope of Claims] 1. In an electrostatic image developer that is composed of a mixture of a carrier and a toner and imparts a charge of a predetermined polarity to the toner through mutual friction between the carrier and the toner, the volume specific resistance value (hereinafter referred to as ) is 10^1^0≦
ρ≦10^1^6 Ω・cm, and the ρ of the toner containing this binder polymer component is 10^1^2≦ρ≦10
An electrostatic image developer comprising the use of a low resistance insulating toner having a resistance of ^1^6 Ω·cm. 2. The electrostatic image developer according to claim 1, which contains a carrier having an inorganic surface and a third component in an amount of 0.01 to 10% by weight based on the weight of the toner. 3 As the third component, 0.05 to 5% based on the toner weight
An electrostatic image developer according to claim 2, characterized in that it contains a hydrophobic silica powder and a long chain fatty acid metal salt in an amount of % by weight.