JPH0147788B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic developer. More specifically, the present invention relates to a heat-fixing type electrophotographic developer in which the phenomenon of adhesion to a fixing roller during heat-fixing is improved.

A developing material for electrophotography, so-called electrostatic toner, is an image forming material used in the next stage of charging and exposure in electrostatic electrophotography, and is a charged fine powder in which carbon black or pigment is dispersed in a resin. In general, electrostatic toners include dry two-component toners that are used with carriers such as iron powder or glass particles, wet toners that are dispersion systems that use organic solvents such as isoparaffinic toners, and furthermore, electrostatic toners that have fine magnetic powder dispersed within them. It is classified as a dry one-component toner.

An image developed on a photosensitive plate with electrostatic toner is transferred to paper, and an image developed directly on paper coated with a photosensitive layer is fixed as is with heat or solvent vapor. Among these, fixing using a heating roller is preferable because it is a contact fixing method, has high thermal efficiency, can reliably fix images using a relatively low-temperature heat source, and is also suitable for high-speed copying.

However, when an image is fixed by contacting a heating body such as a heating roller, there is a risk that a portion of the electrostatic toner adheres to the heating body and is transferred to a subsequent image portion, resulting in a so-called offset phenomenon. Particularly in high-speed copying, raising the temperature of the heating element to increase the fixing effect and fixing speed tends to cause the offset phenomenon more easily. Therefore, for example, when fixing an image formed using a one-component electrostatic toner using a heated roller, the offset phenomenon can be eliminated by impregnating the roller surface with silicone oil or supplying silicone oil to the roller surface. However, this results in problems such as staining of the rolls.

On the other hand, thermoplastic resins that are the main materials of electrostatic toner include low molecular weight polystyrene, ketone resin, maleic acid resin, coumaron resin, phenolic resin,
Examples include epoxy resin, terpene resin, styrene/acrylic copolymer, polyvinyl butyral, polybutyl methacrylate, etc. Among them, low molecular weight polystyrene has good charging properties, an appropriate softening point (around 100°C), and fixing properties. The photosensitive plate is easy to clean with little contamination, has low hygroscopicity, and has good miscibility with the coloring material carbon black.
It is the most commonly used because it has characteristics such as being easy to crush. However, as mentioned above, even low molecular weight polystyrene having such characteristics tends to cause the offset phenomenon in high-speed copying, so it is desired to develop an electrostatic toner that does not cause the offset phenomenon. The present invention was discovered as a result of studies on the development of an electrostatic toner that does not cause such a phenomenon, and by using a resin obtained by grafting a styrene monomer to polyethylene wax as the main material, an electrostatic toner that does not easily cause the offset phenomenon can be obtained. This led to the present invention.

That is, the present invention provides (A) an intrinsic viscosity of 0.06 to 2.0;
It is characterized by comprising a styrene-based grafted polyethylene wax obtained by grafting 1 to 90 parts by weight of a styrene monomer to 99 to 10 parts by weight of polyethylene wax of dl/g, and (B) a coloring agent. The present invention provides a heat-fixing electrophotographic developing material.

The thermoplastic resin that is the main material of the heat-fixable electrophotographic developing material (hereinafter referred to as electrostatic toner) of the present invention is (A) a resin whose main component is a resin obtained by grafting a specific amount of styrene monomer onto polyethylene wax. It is.

The polyethylene wax to which the styrene monomer is grafted has an intrinsic viscosity of 0.06 to 2.0.
dl/g, preferably 0.06 to 0.7 dl/g, particularly preferably 0.06 to 0.5 dl/g (decalin solvent, 135°C), by thermal decomposition of high-pressure polyethylene, or by radical polymerization of ethylene at high pressure. High-pressure polymerized polyethylene wax obtained by
It is obtained by medium/low pressure polymerization of α-olefins such as 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-decene using a transition metal compound catalyst. The styrene monomers include styrene, α-methylstyrene, p-methylstyrene, p-methoxystyrene, m-methylstyrene, and the like.

The intrinsic viscosity of polyethylene wax is 0.06 dl/g
If it is less than this, the melt viscosity becomes too low, which tends to cause toner aggregation and staining of the photoreceptor. Furthermore, if the intrinsic viscosity exceeds 2.0 dl/g, the melt viscosity is too high and a sufficient mold release effect is not exhibited, making it easy for the offset phenomenon to occur.

The amount of styrene monomer grafted onto the polyethylene wax is 99%.
The amount is 1 to 90 parts by weight per 1 to 10 parts by weight, preferably 5 to 50 parts by weight per 95 to 50 parts by weight of polyethylene wax. If the grafting amount of the styrene monomer is less than 1 part by weight, the dispersibility of the colorant will be poor and the fixability to paper will be insufficient, which is undesirable. When used as an electric toner raw material, a phenomenon of adhesion to the heat fixing roller occurs.

Any known method can be used to graft the styrene monomer onto the polyethylene wax. For example, a method can be exemplified in which polyethylene wax is directly melted or dissolved in a solvent, and a styrene monomer is added with or without a radical initiator for grafting. As radical initiators, organic peroxides, organic peresters such as benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-
tert-butyl peroxide, 2,5-dimethyl-
2,5-di(peroxybenzoate)hexyne-3,1,4-bis(tert-butylperoxyisopropyl)benzene, lauroyl peroxide, tert-butyl peracetate, 2,5-dimethyl-2,5-di(tert- butylperoxy)hexane-3,2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl perbenzoate, tert-butyl perphenylacetate, tert-butyl perisobutyrate,
These include tert-butyl per-sec-octoate, tert-butyl perpivalate, cumyl perpivalate and tert-butyl perdiethyl acetate, as well as other azo compounds such as azobis-isobutylnitrile, dimethylazoisobutyrate. Among these, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-
di(tert-butylperoxy)hexyne-3,
Dialkyl peroxides such as 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and 1,4-bis(tert-butylperoxyisopropyl)benzene are preferred.

The thermoplastic resin, which is the main material of the electrostatic toner, does not necessarily have to be entirely the above-mentioned (A) styrene monomer-grafted polyethylene wax, but should account for 20% by weight or more, preferably 50% by weight of the thermoplastic resin. If so, an electrostatic toner with improved offset phenomenon can be obtained. Thermoplastic resins for electrostatic toners used in combination with styrene-based monomer-grafted polyethylene wax include low molecular weight polystyrene, styrene-butadiene copolymer, styrene-butadiene copolymer,
Acrylic acid copolymer, ketone resin, maleic acid resin, epoxy resin, phenol resin, polyvinyl butyral, coumaron indene resin, vinyl acetate, vinyl chloride, vinyl methyl ether, polyethylene, polypropylene, polybutadiene,
Examples include ethylene/vinyl acetate copolymer. Among these, ethylene vinyl acetate copolymer and low molecular weight polystyrene are preferred.

The colorants (B) used in the electrostatic toner of the present invention include carbon black, phthalocyanine blue, aniline blue, alcohol blue, chrome yellow,
Ultramarine blue, quinoline yellow, lamp black, rose bengal, diazo yellow,
It consists of one or more pigments or dyes such as rhodamine B lake, carmine 6B, and quinacridone derivatives. If necessary, azine-based nigrosine, indiulin, azo-based, anthraquinone-based, triphenylmethane-based,
Oil-soluble dyes such as xanthene and phthalocyanine may also be used together.

When the electrostatic toner of the present invention is used as a one-component electrostatic toner, the above-mentioned (A) styrene-based monomer-grafted polyethylene wax, (B) coloring agent, and, if necessary, the above-mentioned low molecular weight polystyrene etc. and a thermoplastic resin using a known method such as a ball mill or an attritor, and then kneaded using a heated twin roll, heated kneader, extruder, etc., cooled and solidified, coarsely crushed using a hammer mill, crusher, etc., and then jet milled. , finely pulverized with a vibrating mill or a ball mill, attritor, etc. with water added, and the average particle size is approximately 5.
~35μ is used as an electrostatic toner. When using a one-component electrostatic toner as a developing material, it is used in combination with a carrier. As the carrier, known carriers such as silica sand, glass beads, iron balls, or powdered magnetic materials such as iron, nickel, and cobalt with a diameter of 200 to 700 μm can be used. The amount of colorant (B) in the one-component electrostatic toner is usually 1 to 20 parts by weight, preferably 3 to 20 parts by weight, based on 100 parts by weight of the thermoplastic resin.
15 parts by weight is added.

When the electrostatic toner of the present invention is used as a two-component electrostatic toner, the above-mentioned (A) styrene-based monomer-grafted polyethylene wax, (B) colorant, and if necessary, the above-mentioned low molecular weight polystyrene etc. Other thermoplastic resins and magnetic material powders can be prepared in the same manner as the one-component electrostatic toner. As the magnetic material powder added to two-component electrostatic toner, fine magnetite powder of 1μ or less is usually used, but powders of metals such as cobalt, iron, and nickel, their alloys, oxides, ferrite, and mixtures thereof are used. can also be used. The amount of each component in the two-component electrostatic toner is usually such that the total amount of the thermoplastic resin and the magnetic material is 100 parts by weight, and the magnetic material is blended at a ratio of 40 to 70 parts by weight. If the amount of magnetic material is too large, the electrical resistance of the electrostatic toner decreases, the charge retention of the electrostatic toner deteriorates, and images may blur. Furthermore, the softening point of the electrostatic toner may become high, making it difficult to properly fix the toner. On the other hand, if the amount of magnetic material is too small, the toner will lose its function as an electrostatic toner, and the required charging ability will not be obtained, and it will be more likely to scatter. Further, a known charge control agent may be added to the one-component electrostatic toner or the two-component electrostatic toner, if necessary.

The heat-fixing type electrophotographic developer of the present invention has excellent releasability from heating rolls, etc., not only at conventional temperatures but also at high temperatures, so even if the heating roll, etc. is heated to a high temperature and the fixing speed is increased, the offset phenomenon does not occur. This makes it ideal for high-speed copying.

The effects of the present invention will be explained in more detail with reference to Examples below.

Example 1 [Manufacture of styrene monomer grafted polyethylene wax] 1000 g of high-density polyethylene wax with an intrinsic viscosity of 0.15 dl/g (trade name: Mitsui Hiwax #200P: Mitsui Petrochemical Industries KK) was charged into a glass reactor (No. 2). , melted at 140°C. Next, 429 g of styrene monomer and 36 g of di-tert-butyl peroxide (hereinafter abbreviated as DTBPO) were added, heated and reacted for 6 hours, and then degassed in a vacuum of 5 mmHg for 1 hour in the solvent state to remove volatile components. It was then cooled. The amount of styrene grafted in the obtained styrene grafted polyethylene wax (hereinafter referred to as SGW-) was 30 g in 100 g of SGW-.

[Two-component electrostatic toner]

SWG-: 100 parts by weight, carbon black (product name: Diamond Black SH, Mitsubishi Chemical Industries KK
): 5 parts by weight were mixed in a ball mill for 24 hours, then kneaded with a hot roll, cooled, and then crushed and classified to give 13~
A 15μ electrostatic toner was prepared. Then the average particle size is 50
Carrier 100 with ~80μ iron content as carrier
The electrostatic toner was mixed at a ratio of 2 parts by weight to 2 parts by weight, developed on a selenium photoreceptor by a known electrophotographic method, transferred onto transfer paper, and fixed by heating with a heating roll. As a result, even after copying 2000 times, a copy image was obtained that was as clear as the initial image and free from offset phenomena and contamination, and no contamination of the hot roll was observed.

Example 2 SWG obtained in Example 1: 50 parts by weight, low molecular weight polystyrene (trade name: Hymer ST-95, Sanyo Chemical Industries KK): 50 parts by weight, and carbon black used in Example 1: 5 parts by weight. were kneaded and ground in the same manner as in Example 1 to obtain an electrostatic toner. Next, copying was carried out 10,000 times in the same manner as in Example 1, and as a result, a copy image was obtained that was as clear as the initial one and free of offset phenomena, stains, etc., and no staining of the hot roll was observed.

Comparative Example 1 An electrostatic toner was obtained in the same manner as in Example 1 except that low molecular weight polystyrene (trade name: Hymer ST-95, Sanyo Chemical Industries, Ltd. KK) was used instead of SWG- used in Example 1. Subsequently, copying was carried out 1000 times in the same manner as in Example 1. As a result, the peelability from the hot roll was poor, and an offset phenomenon and staining of the copy paper were observed.

Comparative Example 2 The same procedure as in Example 2 was performed except that non-grafted high-density polyethylene wax (trade name: Mitsui Hiwax #200P) was used instead of SWG- used in Example 2. As a result, the results were as follows: Since then, the offset phenomenon has become more severe.

Comparative Example 3 Instead of the low molecular weight polystyrene used in Example 2, styrene-butadiene copolymer (trade name:
The procedure was carried out in the same manner as in Example 2, except that Briolite (manufactured by Goodyear Co., Ltd.) was used and non-grafted high-density polyethylene wax (trade name: Mitsui Hiwax #200P) was used instead of SWG-, and the same results were obtained. The offset phenomenon became severe after the 1000th copy.

Example 3 Styrene monomer 250 was prepared in the same manner as in Example 1.
A styrene-grafted polyethylene wax (hereinafter referred to as SGW-) with a styrene graft amount of 20% by weight was obtained by adding 58 g of DTBPO and 58 g of DTBPO. then
SGW-: 40 parts by weight, magnetic powder (product name: Mapico Black BL-500, Titanium Kogyo KK): 50 parts by weight,
Ethylene/vinyl acetate copolymer (trade name: Evaflex 460, Mitsui Polychemicals KK): 10 parts by weight and carbon black (trade name: MA-100: Mitsubishi Chemical Industries KK): 2 parts by weight were mixed in a ball mill for 24 hours. The mixture was kneaded for 1 hour using heated rolls, then finely pulverized using a jet mill, heat-treated using a spray dryer, and then processed using a zigzag classifier to obtain a magnetic toner having an average particle size of 15 μm. Using the magnetic toner, it was developed on a selenium photoreceptor by a conventionally known electrophotographic method, transferred onto transfer paper, and heated roll temperature was set at 200°C.
Durability test of 5000 copies was conducted. As a result, a good copy image was obtained without staining the heating roll.

Example 4 Same as Example 3 except that instead of 40 parts by weight of SGW- used in Example 3, a mixture consisting of 16 parts by weight of SGW-: and 24 parts by weight of low molecular weight polystyrene used in Example 2 was used. I went to As a result, even after 2000 copies, a good copy image was obtained without any contamination of the heating roll.

Comparative Example 4 The same procedure as in Example 3 was carried out except that 40 parts by weight of the low molecular weight polystyrene used in Comparative Example 1 was used instead of 40 parts by weight of SGW- in Example 3. As a result, after 1000 copies, the heating roll became contaminated and the copied image became unclear.

Example 5 In the same manner as in Example 1, 250 g of vinyl toluene monomer and 21 g of DTBPO were added to obtain a vinyl toluene grafted polyethylene wax (hereinafter referred to as VGW-) with a vinyl toluene grafting amount of 20% by weight. Next, 40 parts by weight of VGW was used in place of 40 parts by weight of SGW in Example 3, and copying was performed 5000 times in the same manner as in Example 3. As a result, even after copying, there was no contamination of the heating roll and a good copy image was obtained.

Example 6 Instead of the polyethylene wax with an intrinsic viscosity of 0.15 dl/g used in Example 1, a polyethylene wax with an intrinsic viscosity of 0.5 dl/g (a homopolymer polymerized with a Ziegler type catalyst) was used, and the reaction temperature was 160 dl/g. A styrene-grafted polyethylene wax (SGW-) was obtained in the same manner as in Example 1, except that the styrene monomer amount was changed to 52 g and the DTBPO was changed to 3.8 g.

Next, instead of SGW− in Example 3, SGW
A toner was prepared in the same manner as in Example 3, except that - was used, and a copying durability experiment was conducted.

As a result, even after 3000 copies, there was no contamination of the heating roll, and a good copy image was obtained.

Example 7 Same as Example 1 except that polyethylene wax with an intrinsic viscosity of 0.07 dl/g (a homopolymer polymerized with a Ziegler type catalyst) was used instead of the polyethylene wax with an intrinsic viscosity of 0.15 dl/g used in Example 1. Similarly,
A styrene grafted polyethylene wax (SGW-) with a styrene graft amount of 30% by weight was obtained.
Next, instead of SGW- in Example 3, SGW-
A toner was prepared in the same manner as in Example 3, except that a toner was used, and a copying durability experiment was conducted.

As a result, even after 2000 copies, the heating roll remained clean and a good copy image was obtained.

From the above results, the intrinsic viscosity is 0.06 to 2.0dl/
By using a polyethylene wax obtained by grafting 1 to 90 parts by weight of styrene monomer to 99 to 10 parts by weight of polyethylene wax, the heating roll is free from stains, clear, and free from offset phenomena, contamination, etc. It can be seen that it is possible to obtain a copy image that does not

Claims (1)

[Claims] 1 (A) Styrenic grafted polyethylene wax obtained by grafting 1 to 90 parts by weight of a styrene monomer to 99 to 10 parts by weight of polyethylene wax with an intrinsic viscosity of 0.06 to 2.0 dl/g, and (B) Coloring. A heat-fixing type electrophotographic developer comprising: