JPS6357787B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developer for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, and the like. More specifically, the present invention relates to a two-component dry developer consisting of a carrier and a toner that is effectively used in so-called dry development methods such as the cascade method and the magnetic brush method.

Generally, in the dry development method, a two-component developer is used, which is a mixture of a fine powder called toner, which is made by dispersing a coloring agent such as carbon black in a natural or synthetic resin, and a carrier made of iron powder or glass beads. It is used. At this time, the toner is made to hold a positive or negative charge depending on the polarity of the electrostatic charge image to be developed. As a method for making the toner hold an electric charge, it is also possible to utilize the triboelectricity of the resin that is a component of the toner, but since the chargeability imparted to the toner is small in this method, the image obtained by development may be foggy. is likely to occur and the image becomes unclear. Therefore, in order to impart desired triboelectric charging properties, dyes such as nigrosine are incorporated into the toner as a charge control agent.

However, many conventional charge control agents have a problem in that they tend to impart excessive triboelectric charging properties to toner. Therefore, if a relatively small amount of toner is mixed into the carrier, the image obtained by development will have a low image density and will be unclear and prone to density unevenness. This is because the excessive triboelectricity imparted to the toner increases the electrostatic holding force that acts between the toner and the iron powder carrier, and as a result, during development, the toner is attracted to the electrostatic latent image on the photoreceptor. This is thought to be because it is less likely to be absorbed by the transfer paper during transfer.

Conventionally, therefore, a method has been adopted in which the triboelectric charging property imparted to the toner is reduced by increasing the mixing ratio of the toner to the carrier.
In other words, when the ratio of toner mixed into the carrier is increased, the frequency of contact between each toner and the carrier surface is reduced, and the triboelectric charge that should be applied to each toner is reduced, so that the amount of friction that acts between the toner and the carrier is reduced. The electrostatic holding force becomes weaker, and a proper image without a decrease in image density or density unevenness can be obtained.

However, in this method, there are problems such as adhesion of fine particles contained in the toner to the carrier, and furthermore, a phenomenon in which the toner is fused to the carrier due to frictional heat generated by mixing and stirring the developer in the developing device. As a result, the developing ability of the developer decreases, and it becomes difficult to maintain the developing ability of the developer stably over a long period of time.

As a method to solve this problem,
113739 focuses on the modification of charge control agents, and proposes that an aminotriphenylmethane dye represented by a specific general formula be made into a lake with phosphotungsten molybdic acid to make it water-insoluble and use it as a charge control agent. is suggesting.

The present inventors focused on a system in which the content of toner in the carrier was lower than before, and worked diligently to find a developer that has long-term stable development ability and that provides clear images without fogging or density unevenness. After considering the toner content for the carrier,
It is known that the desired purpose can be achieved by using a triaminotriphenylmethane dye containing 0.5 to 5% by weight and having a sulfonic acid group or a sulfonate group as a substituent as a charge control agent. This led to the completion of the present invention.

That is, the gist of the present invention is a triaminotriphenylmethane dye (hereinafter simply "triaminotriphenylmethane dye") having carbon black and a sulfonic acid group or a sulfonate group as substituents in (a) a carrier and (b) a resin. The present invention relates to a dry developer comprising a positively charged toner containing an enylmethane dye), the toner content being 0.5 to 5% by weight.

The present invention will be explained in detail below.

Examples of the carrier (a) used in the present invention include iron powder and glass beads. Iron powder is particularly preferred, usually with an average particle size of 15 to 500μ, preferably
50 to 200μ is used.

The toner (b) used in the present invention is prepared by incorporating carbon black and triaminotriphenylmethane dye into a resin.

Examples of resins include styrenes such as styrene and parachlorostyrene; vinylnaphthalene; vinyl halides such as vinyl chloride, vinyl bromide, and vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate, and vinyl butyrate; Methyl acrylate, ethyl acrylate, n-butyl acrylate,
α-Methylene such as isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, etc. Esters of aliphatic monocarboxylic acids; acrylonitrile; methacrylnitrile; acrylamide; vinyl ethers such as vinyl methyl ether, vinyl isobutyl ether, vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone; A homopolymer or copolymer obtained by polymerizing one or more compounds selected from -vinyl-substituted heterocyclic compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone. Examples include rosin-modified phenol-formalin resins, oil-modified epoxy resins, polyurethane resins, cellulose resins, polyether resins, or mixtures thereof. Among these resins, homopolymers of styrenes and copolymers of styrenes and esters of α-methylene aliphatic monocarboxylic acids are preferred. Such polymers usually have a glass transition temperature of 20°C or higher, with a glass transition temperature of 1000 to
It has a weight average molecular weight of 200,000.

Various known carbon blacks can be used. For example, Mitsubishi Carbon Black #30, #32, #33, #40, #44, #45, #50,
#52, #55, #600, MA-8, MA-11, MA-
100, MA-600, MCF-88 (trade names manufactured by Mitsubishi Chemical Industries, Ltd.), and the like.

The triaminotriphenylmethane dye used in the present invention has a sulfonic acid group or a sulfonate group as a substituent. Examples include those substituted with metal. Specifically, for example, those represented by the following formula may be mentioned.

In the above formulas, those represented by (), () and () are particularly preferred.

(b) The toner is prepared by kneading the above resin, carbon black, and triaminotriphenylmethane dye using a tabletop kneader or the like, cooling, pulverizing the mixture using a jet mill, or the like, and classifying the mixture.

The amount of carbon black and triaminotriphenylmethane dye to be used is 3 to 20 parts by weight of carbon black and 1 to 20 parts by weight of triaminotriphenylmethane dye, preferably 2 to 10 parts by weight, per 100 parts by weight of resin. Selected from a range of departments.

The toner (b) used in the present invention has an average particle size of 5 to
A thickness of 20μ is suitable.

The developer of the present invention comprises a combination of the above (a) carrier and (b) toner. In the developer, the content of (b) toner is 0.5 to 5% by weight, preferably 0.5 to 3% by weight.
It is. If the toner content is less than the above range,
Image density is low, density unevenness tends to occur, and clear images cannot be obtained. On the other hand, if the toner content is higher than the above range, stable developing ability cannot be maintained over a long period of time.

The thus-obtained developer of the present invention has the economical advantage that only a small amount of toner is required, and since the toner content is small, there is little contamination of the carrier by toner, and the developing ability of the developer is reduced. This makes it possible to obtain stable images over a long period of time.

A homogeneous image with high resolution can be obtained without a decrease in image density, fogging, or density unevenness.

There is little toner scattering and the inside of the copying device is not contaminated.

The phenomenon of toner filming that occurs when using a photosensitive original plate that is repeatedly used by a transfer method does not occur.

There are advantages such as

The developer of the present invention can be advantageously used in various dry development methods such as the cascade method and the magnetic brush method. Further, the developer of the present invention has the so-called
It can also be advantageously used as a reversal developer.

The present invention will be further explained in detail by giving examples below. In the Examples, "part" means "part by weight".

Example 1 65 parts styrene and 35 parts methacrylic acid n-
Copolymer 100 with a softening point of approximately 120℃ (ball and ring softening point measurement method) obtained by copolymerizing butyl
10 parts of Mitsubishi Carbon Black #30 (trade name, manufactured by Mitsubishi Chemical Industries, Ltd.) as a coloring agent, and
Three parts of the triaminotriphenylmethane dye represented by the above formula () as a charge control agent was charged into a mold blender, premixed for about 1 hour, and then kneaded for 30 minutes at 150° C. using a tabletop kneader. The kneaded material was cooled, pre-pulverized, then crushed in a jet mill and classified to prepare a toner having an average particle size of 15 μm.

A developer was prepared by mixing 1 part of the obtained toner with 99 parts of iron powder carrier having an average particle size of 100μ, and a developer was prepared using a plain paper transfer type copying machine (U-Bix800 copying machine, manufactured by Konishirokusha).
Image formation was performed using

As a result, the obtained image was extremely clear without fogging or density unevenness, and had sufficiently high image density.

Furthermore, when images were repeatedly formed using this developer, there was almost no toner contamination on the iron powder carrier, and even after approximately 40,000 image formations, clear images were obtained. It was confirmed that the image quality was almost the same as that obtained by image formation. Further, no occurrence of toner filming was observed.

Example 2 A developer was prepared in exactly the same manner as in Example 1, except that 7 parts of the triaminotriphenylmethane dye represented by the formula () was used instead of 3 parts of the same dye, and Image formation was performed.

As a result, the images obtained were clear and free from fog and density unevenness. Furthermore, it was confirmed that there was no toner contamination even after approximately 40,000 image formations, and that the image was almost the same as the initial image. Furthermore, no contamination of the copying machine due to toner scattering was observed.

Example 3 In Example 1, the procedure was exactly the same as in Example 1 except that 3 parts of the dye represented by the above formula () was used instead of 3 parts of the triaminotriphenylmethane dye represented by the above formula (). A developer was prepared and an image was formed.

As a result, it was confirmed that even after approximately 40,000 image formations, there was no contamination of the toner and the image was almost the same as the initial one. A developer was prepared and an image was formed in exactly the same manner as in Example 1, except that 10 parts of toner and 90 parts of iron powder carrier were used instead of 10 parts of toner.

As a result, it was confirmed that toner contamination of the iron powder carrier occurred, resulting in an unclear image after approximately 15,000 image formations, making it unusable for practical use.

Comparative Examples 2 and 3 In Example 1, 1 part and 3 parts of Nigrosine Oil Black BS (trade name, manufactured by Orient Chemical Co., Ltd.) were used instead of 3 parts of the triaminotriphenylmethane dye represented by the above formula (). Other than that, the developer was prepared in the same manner as in Example 1,
Image formation was performed.

As a result, it was confirmed that all images had low image density, uneven density, and were unclear.

Comparative Example 4 In Comparative Example 3, a developer was prepared and an image was formed in exactly the same manner as in Comparative Example 3, except that 5 parts of the prepared toner was used instead of 1 part.

As a result, it was confirmed that although a clear image without density unevenness was obtained in the initial stage, the image obtained after approximately 15,000 image formations was unclear.

Comparative Example 5 A developer was prepared in the same manner as in Example 1, except that 0.5 parts of Nigrosine Oil Black BS was used instead of 3 parts of the triaminotriphenylmethane dye represented by the above formula (). Prepare,
Image formation was performed.

As a result, it was confirmed that the obtained image had severe fogging and was unclear with low resolution.

Claims (1)

[Scope of Claims] 1. A positively charged product comprising (a) a carrier and (b) a resin containing carbon black and a triaminotriphenylmethane dye having a sulfonic acid group or a sulfonate group as a substituent. A dry developer comprising a toner and having a toner content of 0.5 to 5% by weight.