JPH0350266B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry developing toner for heat fixing that has an excellent combination of offset resistance, heat resistance, blocking resistance, fluidity and fixing properties. In the field of electrophotography, the heat-pressing method using a roller is advantageous in terms of thermal efficiency, prevention of fire accidents, and fixing operation for thermally fixing toner particles onto copy paper, but it is difficult to fix the toner particles on the surface of the fixing roller and the toner particle image. Due to contact under heat and pressure, so-called offset development occurs in which some of the toner particles adhere to and transfer to the surface of the fixing roller, which then transfers onto the copy paper again and causes stains on the copy paper, which is a problem. becomes. Several methods have been used to prevent such defects, and one typical method is to make the surface of the fixing roller made of a releasable or stain-resistant material such as fluororesin. At the same time, a thin film of anti-offset liquid such as silicone oil is formed on the surface of the image, but this method complicates the mechanism of the fixing device and requires the anti-offset liquid during fixing. Another typical method involves pre-containing a substance to be used as a release agent in toner particles, and releasing the substance in liquid form onto the surface of the particles during fixing by a roller, thereby creating an offset effect. The purpose is to prevent development. However, in this latter method, the desired effect cannot be obtained unless a considerably large amount of release agent is contained in the toner particles, and along with this, there is a decrease in fluidity due to toner blocking and a decrease in heat resistance. , troubles such as spent toner (deterioration of carrier physical properties due to resin adhesion to the carrier) occur, and these troubles are exacerbated by the ease with which the release agent migrates to the surface of the donor particles (imigration). It becomes something that cannot be ignored. When considering offset development that occurs when a toner image is fixed by a heating roller, the causes can be roughly divided into the following two types. One is when the toner particles are completely melted, but the adhesion of the molten toner to the roller is greater than the cohesive force of the molten toner, resulting in transfer to the roller surface (hot offset). The other one is
The toner particles are melted on the heating roller side, but are not melted or softened on the copy paper side, resulting in transfer to the roller surface (cold offset). All offset prevention methods are aimed at preventing toner from sticking to the heating roller, and from the viewpoint of the cohesive force of toner particles in a molten state and fixing performance at relatively low temperatures, offset is Therefore, an object of the present invention is to provide a dry developing toner for heat fixing that has an excellent combination of offset resistance, heat resistance, blocking resistance, fluidity, and fixability. Another object of the present invention is to provide a dry development toner for heat fixing that prevents the above-mentioned hot offset and cold offset and has excellent fluidity even at relatively high temperatures. Still another object of the invention is to provide a one-component magnetic toner for heat fixing which has an excellent combination of the above properties.According to the invention, the composition of a thermoplastic resin medium and a pigment dispersed in the medium is In the dry development toner for heat fixing, the thermoplastic resin medium comprises (A) an aromatic vinyl having a weight average molecular weight of 50,000 or more and a glass transition temperature of 70°C or less, and an alkyl group having 6 or more carbon atoms; (B) has a weight average molecular weight of 50,000 or more and a glass transition temperature of 70
Aromatic vinyl in the range of 80℃ to 80℃ and carbon number 4
Provided is a toner comprising a blend containing a copolymer with an ethylenically unsaturated carboxylic acid alkyl ester having the following alkyl group in a weight ratio of A:B = 90:10 to 10:90. be done. In the present invention, a copolymer of aromatic vinyl and an ethylenically unsaturated carboxylic acid alkyl ester is used as the thermoplastic resin medium of a dry developing toner for heat fixing. A distinctive feature is the use of a combination of copolymers of acrylates with groups and copolymers of acrylates with short-chain alkyl groups. When toner is thermally fixed by a heating roller, if the area where offset development occurs is blotted based on both the roller temperature and the contact time with the roller, generally the high temperature side and long time side will be the hot offset area, and the low temperature side and short time side will be the cold offset area. A non-offset fixing region exists between these two regions, and the width of this non-offset fixing region varies depending on the type of resin. In the present invention,
By using the above-mentioned multiple types of copolymers in combination, the range of this non-offset fixing region can be significantly increased, and the heat resistance, blocking resistance, and fluidity can be improved without impairing the fixing properties of the toner. becomes possible. First, as the molecular weight of the resin used generally increases, the foot offset range shifts toward higher temperatures and longer times, but along with this, the cold offset range also shifts toward higher temperatures and longer times. There is a tendency for this area to expand. Furthermore, as the softening point of the resin used decreases, the cold offset region shifts to the lower temperature side and shorter time period, but the hot offset region also tends to shift to the lower temperature side and shorter time period accordingly. Copolymer of aromatic vinyl and ethylenically unsaturated carboxylic acid long-chain alkyl ester used in the present invention
Because of its low softening temperature, (A) has the effect of shifting the cold offset region to the low temperature side and short time side, and because the temperature dependence of melt viscosity is relatively small, it also shifts the hot offset region to a relatively high temperature side. It has the desirable effect of causing the offset to shift to the long side and to the long time side, and as a result, widening the non-offset area. However, the disadvantage of toner produced from this long-chain alkyl group-containing copolymer (A) is that it has poor heat resistance, and this toner easily aggregates in the developing mechanism of commercial copying machines, resulting in poor fluidity. This tends to cause deterioration in image quality and density due to toner supply failure, charging failure, etc. According to the present invention, a copolymer of aromatic vinyl and an ethylenically unsaturated carboxylic acid short chain alkyl ester is added to the above-mentioned base polymer (A) of an aromatic vinyl and an ethylenically unsaturated carboxylic acid long chain alkyl ester. Combine (B)
By using a blend of the above-mentioned copolymer (A), the heat resistance, blocking resistance, and fluidity of the toner can be improved while substantially maintaining the wide non-offset area and excellent fixing properties when using the copolymer (A) alone. can significantly improve performance. The aromatic vinyl monomer used in the copolymer of the present invention has the following formula: In the formula, R ₁ is a hydrogen atom, lower (having 4 or less carbon atoms)
It is an alkyl group or a halogen atom, R ₂ is a substituent such as a lower alkyl group or a halogen atom, and n is an integer of 2 or less including zero. Examples of monomers represented by the above include styrene, vinyltoluene, α-methylstyrene, α-chlorostyrene, vinylxylene, and vinylnaphthalene. Among these, styrene and vinyltoluene are preferred. As a long chain alkyl ester of ethylenically unsaturated carboxylic acid, In the formula, R ₃ is a hydrogen atom or a lower alkyl group, and R ₄ is an alkyl group having 6 or more carbon atoms. Monomers represented by, for example, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, decyl acrylate, decyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, etc. are used. The long chain alkyl group is 2
- Ethylhexyl group is preferable. The copolymer (A) should have a weight average molecular weight (MW) of 50,000 or more, especially 70,000 or more from the viewpoint of preventing hot offset, while from the viewpoint of preventing cold offset it should have a weight average molecular weight (MW) of 70°C or less, especially 68°C or less. should have a glass transition temperature (Tg) of The number of carbon atoms in the alkyl group in the aromatic vinyl and acrylate copolymer (A) is related to the width of the non-offset region, and it can be softened by setting the number of carbon atoms in the alkyl group to 6 or more, especially from 6 to 18. It is possible to reduce the stability dependence of the melt viscosity while keeping the melt viscosity low. From this perspective, aromatic vinyl and long-chain alkyl acrylate, etc. are 50:50.
It is desirable to copolymerize at a molar ratio of 90:10 to 90:10, particularly 60:40 to 80:20. As the aromatic vinyl of the other copolymer (B), those exemplified above are similarly used, and as the short chain alkyl ester of ethylenically unsaturated carboxylic acid, the following general formula In the formula, R ₃ is a hydrogen atom or a lower alkyl group, and R ₅ is an alkyl group having up to 4 carbon atoms. Monomers such as butyl acrylate, butyl methacrylate, ethyl acrylate, methyl methacrylate, propyl acrylate etc. are used. Preferably, the short chain alkyl group is a butyl group. From the standpoint of toner heat resistance and hot offset prevention, this copolymer has a molecular weight of 50,000 or more, especially 70,000.
It should have a weight average molecular weight of 70° C. or higher, and a glass transition temperature of 70° C. or higher. Further, from the viewpoint of preventing cold offset and fixing properties, the glass transition temperature should be 80°C or less. The number of carbon atoms in the alkyl group in the copolymer (B) should be 4 or less in terms of heat resistance of the toner,
Furthermore, the ratio of vinyl aromatic acid and short chain alkyl acrylate etc. is 50:50 to 90:10, especially 60:40 to 80:20.
It is desirable to copolymerize at a molar ratio of . In the present invention, the long-chain alkyl group-containing copolymer (A) and the short-chain alkyl group-containing copolymer (B) are mixed in a ratio of A:B=90:10 to 10:90, particularly 70:30 to 30:70. The use of combinations in weight ratios is also of great importance with respect to the aforementioned objectives of the invention. That is, when the amount of the long-chain alkyl group-containing copolymer (A) is less than the above range, or when the short-chain alkyl group-containing copolymer
When the amount of (B) is greater than the above range, the fixing area is sandwiched between the non-offset areas, which increases the tendency to cause cold offset and hot offset, and also increases the tendency to reduce the fixability of the toner.
Furthermore, when the amount of the long-chain alkyl group-containing copolymer (A) is greater than the above range, or when the amount of the short-chain alkyl group-containing copolymer (B) is less than the above range, the heat resistance of the toner decreases. , troubles such as blocking of toner particles and decreased fluidity are likely to occur during development. Copolymers (A) and (B) used in the present invention have similar or common chemical structures, except for the difference in the chain length of the alkyl group, and therefore have good compatibility and uniformity. Another notable feature is that it can perform thorough kneading. In the present invention, the pigments include coloring pigments,
One or two of extender pigments, magnetic pigments, and conductive pigments
Combinations of more than one species can be used. Of course, these pigments may also be pigments that have two or more of the above-mentioned functions; for example, carbon black has the function of a conductive pigment as well as a black pigment, and triiron tetroxide has the function of a magnetic pigment. In addition, as is clear from the name, so-called iron black, it also functions as a black pigment. Suitable examples of colored pigments are: Black pigments: carbon black, acetylene black, lamp black, anili black. Yellow pigments Yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fluorite yellow, nickel titanium yellow, naples yellow, naphthol yellow S, Hanser yellow G, Hanser yellow
10G, Benzidine Yellow G, Benzidine Yellow
GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake. Orange pigments Red yellow lead, Molybdenum orange, Permanent orange GTR, Pyrazolone orange, Valka orange, Indanthrene brilliant orange
RK, Benzine Orange G, Indanthrene Brilliant Orange GK. Red pigment red pigment, red red, cadmium lead, mercury cadmium sulfide, permanent red 4R, resol red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake. , brilliant carmine
3B. Purple pigments Manganese purple, Fast Violet B, Methyl Violet Lake. Blue pigments: navy blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, first sky blue, indanthrene blue BC. Green pigments Chrome Green, Chromium Oxide, Pigment Green B, Mayakite Green Lake, Huanal Yellow Green G. White pigments: zinc white, titanium oxide, antimony white, zinc sulfide. Extender pigments barite powder, barium carbonate, cre, silica,
White carbon, talc, alumina white. Conventional examples of magnetic pigments include triiron tetroxide (Fe ₃ O ₄ ), iron sesquioxide (γ-Fe ₂ O ₃ ), zinc iron oxide (ZnFe ₂ O ₄ ), and yttrium iron oxide (Y ₃ Fe ₅ O ₁₂ ),
Iron cadmium oxide (CdFe ₂ O ₄ ), iron gadolinium oxide (Gd ₃ Fe ₅ O ₁₂ ), iron copper oxide (CuFe ₂ O ₄ ), iron lead oxide (PbFe ₁₂ O ₁₉ ), iron nickel oxide (NiFe ₂ O ₄ ),
Neodymium iron oxide (NdFeO ₃ ), barium iron oxide
BaFe ₁₂ O ₁₉ ), magnesium iron oxide (MgFe ₂ O ₄ ),
Iron manganese oxide (MnFe ₂ O ₄ ), lanthanum iron oxide (LaFeO ₃ ), iron powder (Fe), cobalt powder (Co), nickel powder (Ni), etc. are known, and the present invention also uses these known materials. Any fine powder of magnetic material can be used. A particularly suitable magnetic material pigment for the purposes of the present invention is triiron tetroxide. As the conductive pigment, in addition to the above-mentioned carbon black, any material such as an inorganic fine powder or various metal powders which have been subjected to conductive treatment and are non-conductive in themselves can be used. The amount of pigment to be blended can vary widely depending on the intended use of the toner, and generally ranges from 1 to 300% by weight based on the fixing agent. Within these ranges, for use as a two-component developer, i.e., a toner used in combination with a magnetic carrier, 1 per fixer may be used.
Preferably, from 15% to 15% by weight, especially from 2% to 10%, of colored pigments are used, while for applications as one-component magnetic toners, from 50% to 300%, especially by weight, per fixer.
It is preferable to use 60 to 250% by weight of the magnetic material pigment, optionally in combination with a coloring agent pigment and a conductive agent pigment. Other compounding agents known per se can be added to the toner of the present invention according to known formulations.
For example, for use as an electrostatic toner, charge control agents known per se, such as oil-soluble dyes such as nigrosine base (CI5045), oil black (CI26150), and spirone black, naphthenic acid metal salts, fatty acid metal A soap, a resin acid soap, a metal-containing azo dye, etc. may be blended in an amount of 0.1 to 5% by weight based on the fixing agent. Also, silicone oil,
Low molecular weight olefin resins, various waxes, etc. may be used for the purpose of assisting mold release. A toner is obtained by kneading the above-described copolymer blend and pigment, cooling the kneaded composition, pulverizing it, and, if necessary, sieving it. Of course, in order to cut the corners of irregularly shaped particles,
There is no particular problem even if rapid mechanical stirring is performed. The particle size of the toner particles is related to resolution, etc., but is generally desirably in the range of 5 to 35 microns. In the electrostatographic reproduction method using the toner of the invention, the formation of the electrostatic latent image can be carried out in any manner known per se, for example by uniformly charging a photoconductive layer on a conductive substrate. Thereafter, an electrostatic latent image can be formed by imagewise exposure. Development of the electrostatic image is facilitated by contacting the substrate with a magnetic brush, either as is in the case of a one-component magnetic toner or by mixing it with a magnetic carrier in the case of a two-component toner. The toner image formed by development is transferred onto copy paper, and fixed by bringing this toner image into contact with a heating roll. As mentioned above, the dry toner of the present invention has a wide non-offset fixing range, so even if the hot roll fixing conditions vary within a wide range, it can achieve good fixing performance without causing offset development. It also has the advantage of good heat resistance and fluidity. This advantage is particularly remarkable in the case of a toner having a small amount of resin per total amount of toner, such as a one-component magnetic toner. The invention is illustrated by the following example. Example 1 220 parts by weight of magnetite (hereinafter referred to as parts), styrene-2-ethylhexyl acrylate copolymer (glass transition point Tg 64°C, weight average molecular weight Mω approximately 8
120 parts, styrene-butyl methacrylate copolymer (glass transition point Tg 72℃, weight average molecular weight
Mω approx. 100,000) 52 parts, low molecular weight polypropylene 8 parts Negative charge control agent (Bontron® manufactured by Orient Chemical Co., Ltd.)
04) Melt and knead 2.7 parts using a two-roll mill, let it cool, and then coarsely crush it with a cutting mill to give 0.5~
Make it 2.0mm in size. Next, the powder was finely ground using a jet mill and classified using a zigzag classifier.
Obtain ~25μ magnetic toner. The following copying test was conducted using this magnetic toner. In a copying machine that uses a selenium drum (outer diameter 150 mm) as a photoreceptor, the magnetic field strength on the developing sleeve (outer diameter 33 mm) containing a built-in magnet is set to approximately 900 Gauss via a non-magnetic member, and the magnet and sleeve are separated. The magnetic toner described above was deposited on a so-called double-rotation type developing roller that could be rotated individually at the same time, with a spacing of 0.3 mm between the cutting plate and the sleeve, and the magnetic toner was arranged so that it could be supplied from the hopper to the developing roller section. In addition, the distance between the photoreceptor surface and the developing roller was set to 0.5 mm. Charging (+6.7KV), exposure, development, transfer (+
6.3KV), heater roller fixing (roller surface temperature 150°C to 200°C), and fur brush cleaning. High-quality paper with a thickness of 80 μm was used as the transfer paper. The fixing properties were good and no sticking to the fixing roller or offset development was observed. In addition, in order to examine the fluidity of magnetic toner in a high-temperature environment, we conducted a high-temperature environment test where it was placed in an oven set at 60℃ for 4 hours, and no blocking occurred and the toner remained as free-flowing as it was at room temperature. Ta. Furthermore, no change was observed in the degree of agglomeration using a powder tester made by Hosokawa compared to that at room temperature. Comparative Example 1 220 parts by weight of magnet (hereinafter referred to as parts), styrene-2-ethylhexyl acrylate copolymer (glass transition point Tg 64°C, weight average molecular weight Mω approximately 80,000)
Example 1 except that a magnetic control toner was prepared from 172 parts of low molecular weight polypropylene, 8 parts of low molecular weight polypropylene, and 2.7 parts of a negative charge control agent (Bontron R-04 manufactured by Orient Chemical Co., Ltd.)
I went in the same way. The fixing properties were good, and no sticking to the fixing roller or offset development was observed. Furthermore, in high-temperature environment tests, it was almost completely blocked, and even when subjected to impact, it only broke into 2cm-sized chunks. Furthermore, the degree of aggregation increased by approximately three times compared to the temperature at low temperatures. Comparative Example 2 220 parts by weight of magnetite (hereinafter referred to as parts), styrene-butyl methacrylate copolymer (glass transition point Tg 72°C, weight average molecular weight Mω approximately 100,000) 172
The same procedure as in Example 1 was carried out except that a magnetic toner was prepared from 2.7 parts of a negative charge control agent (Pontron R-04 manufactured by Orient Chemical Co., Ltd.), 8 parts of low molecular weight polypropylene, and 2.7 parts of a negative charge control agent (Pontron R-04 manufactured by Orient Chemical Co., Ltd.). Fixability was somewhat poor and hot offset development was observed. As a result of the high-temperature environment test, no blocking occurred and the product remained as free-flowing as it was at room temperature. No change in the degree of aggregation was observed compared to that at room temperature. Example 2 220 parts by weight of magnetite (hereinafter referred to as parts), styrene-2-ethylhexyl methacrylate copolymer (glass transition point Tg 68°C, weight average molecular weight Mω
90,000), 52 parts of styrene-butyl methacrylate copolymer (glass transition point Tg 70℃, weight average molecular weight Mω approximately 70,000), 120 parts, low molecular weight polypropylene 8 parts, negative charge control agent (Orient Chemical)
The same procedure as in Example was carried out except that a magnetic control toner was prepared from 2.7 parts of Bontron R-04). The fixing properties were good, and no sticking to the fixing roller or hot offset development was observed. As a result of the high-temperature environment test, no blocking occurred and the product remained free-flowing at room temperature. No change in the degree of aggregation was observed compared to that at room temperature. Comparative Example 3 220 parts by weight of magnetite (hereinafter referred to as parts), styrene-2-ethylhexyl methacrylate copolymer (glass transition point Tg 68°C, weight average molecular weight Mω
Approximately 90,000 parts) 172 parts, low molecular weight polypropylene 8 parts,
Negative charge control agent (BontronR- manufactured by Orient Chemical Co., Ltd.
04) The same procedure as in Example was carried out except that magnetic toner was prepared from 2.7 parts. The fixing properties were good, and no sticking to the fixing roller or offset development was observed. As a result of the high-temperature environment test, there was considerable agglomeration, and many clumps several millimeters in size were generated. The degree of aggregation was approximately twice as high as that at room temperature. Comparative Example 4 220 parts by weight of magnetite (hereinafter referred to as parts), styrene-butyl methacrylate copolymer (glass transition point Tg 70°C, weight average molecular weight Mω approximately 70,000) 172
The same procedure as in Example was carried out, except that a magnetic toner was prepared from 1 part, 8 parts of low molecular weight polypropylene, and 2.7 parts of a negative charge control agent (Bontron R-04, manufactured by Orient Chemical Co., Ltd.). The retention system was somewhat poor and a hot offset phenomenon was observed. As a result of the high-temperature environment test, no blocking occurred and the product remained as free-flowing as it was at room temperature. No change in the degree of aggregation was observed compared to that at room temperature. The above results are summarized in the table below. 【table】

Claims (1)

[Scope of Claims] 1. A dry developing toner for heat fixing comprising a composition of a thermoplastic resin medium and a pigment dispersed in the medium, wherein the thermoplastic resin medium (A) has a weight average molecular weight of 50,000 or more. and (B) a copolymer of an aromatic vinyl having a glass transition temperature of 70°C or less and an ethylenically unsaturated carboxylic acid alkyl ester having an alkyl group having 6 or more carbon atoms, and (B) a weight average molecular weight of 50,000.
A copolymer of an aromatic vinyl having the above and a glass transition temperature in the range of 70 to 80°C and an ethylenically unsaturated carboxylic acid alkyl ester having an alkyl group having 4 or less carbon atoms, A:B=90: A toner comprising a blend containing a blend in a weight ratio of 10 to 10:90.