JPS6332180B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a developer powder for hot roller fixing used in electrophotography, electrostatic recording, magnetic recording, and the like. Conventionally, as an electrophotographic method, U.S. Patent No. 2297691
Specification of No. 42-23910 and Special Publication No. 1973
Although many methods are known, such as Publication No. -24748,
Generally, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then the latent image is developed using toner, and if necessary, a toner image is transferred to a transfer material such as paper. After the image is transferred, a copy is obtained which is fixed by heat, pressure or solvent vapor. Further, when a step of transferring a toner image is included, a step for removing residual toner is usually provided. Methods for visualizing electrical latent images using toner include, for example, the magnetic brush method described in US Pat. No. 2,874,063, the cascade development method described in US Pat. No. 2,618,552, and US Pat.
The powder cloud method described in U.S. Pat.
A method using conductive magnetic toner described in Japanese Patent No. 3909258 is known. As toners applied to these developing methods, fine powders in which dyes and pigments are dispersed in natural or synthetic resins have conventionally been used. For example, particles obtained by dispersing a colorant in a binder resin such as polystyrene and pulverizing the particles to about 1 to 30 μm are used as toner. As the magnetic toner, one containing magnetic particles such as magnetite is used. In the case of a method using a so-called two-component developer, the toner is usually mixed with carrier particles such as glass beads and iron powder. Although these toners are required to have various physical and chemical properties, many of the known toners have several deficiencies as shown below. That is, many toners that are easily melted by heating tend to cake or aggregate during storage or in a copying machine. Many toners have poor triboelectric and rheological properties due to environmental temperature changes. In addition, with many toners, the density of the resulting image decreases due to mutual deterioration of the toner, carrier particles, and photosensitive plate due to collisions between toner particles and carrier particles due to repeated development due to continuous use and contact between them and the photosensitive plate surface. or the background density increases, reducing the quality of the copy. Furthermore, with many toners, when an attempt is made to increase the density of a copied image by increasing the amount of toner adhering to the surface of a photosensitive plate having a latent image, the background density usually increases, resulting in a so-called fog phenomenon. Among these undesirable phenomena, there are phenomena caused by the fragility of toner particles. If the toner is brittle, it is easily crushed by mechanical force, which is preferable from the viewpoint of toner productivity. However, such toner is easily crushed into fine powder by the load applied to the toner in the developing device, contaminating the carrier particles and the developing sleeve, and the charge control of the toner particles themselves is poor. When the color becomes complete, undesirable phenomena such as fogging occur. As described above, the brittleness of toner is greatly related to the lifespan of the developer. In order to avoid such deterioration phenomena, it is possible to use polymers with high molecular weight, but when considering the thermal fixation of images that is usually performed in the final process of copying, the fixing temperature increases and more polymers are used during fixing. Since it requires a large amount of heat, it is not preferable in terms of energy conservation. Furthermore, it has been proposed to add a small amount of plasticizer to the toner in order to eliminate this phenomenon, but this has not always been successful as it has problems such as impairing the free flowing properties of the toner and contaminating the carrier etc. I haven't. In recent years, the most common fixing method in copying machines has been the heated roller fixing method, but the heated roller fixing devices of currently commercialized copying machines do not apply oil to the rollers. The ones who are there account for the majority. However, oil application causes undesirable problems such as vaporization of the oil and discomfort to the user, oil stains on the sheet, complication of the fixing device, which is likely to cause trouble, and increased costs. Therefore, there is a desire for a hot roller fixing device that does not apply oil or that applies only a small amount of oil, but this will not be possible without improvements in toner. The difficulty in using a hot roller fuser that does not apply oil is that since no oil is applied, the toner must maintain releasability to compensate for this, so it is necessary to maintain a low fusing point and maintain durability. The problem is that it is difficult to obtain a toner with good offset and sticking resistance, and it is even more difficult to obtain a toner that is excellent in both fixing properties and development properties. Conventional toners have either a binder resin that has a molecular weight distribution curve with one peak, multiple peaks in the low molecular weight range, or a mixture of completely different compounds with different molecular weight distributions. It was hot. The above toners could hardly be called excellent toners in terms of both fixing properties and developing properties. Conventionally, various methods have been proposed for improving toner fixing characteristics for heat roller fixing. Tokko Akira
Publication No. 51-23354 proposes a toner using a crosslinked polymer as a binder resin, and if that method is followed, the offset resistance and sticking resistance can be significantly improved, but simply crosslinking is not enough. However, since the fixing temperature is low, it is not possible to obtain sufficient fixing characteristics with good offset resistance and cling resistance. Also, crosslinked polymers have drawbacks such as difficulty in dispersing pigments and incompatibility with other polymers, so toners using crosslinked polymers as a binder resin have difficulties in obtaining good development characteristics. be. Furthermore, Japanese Patent Publication No. 52-3304 proposes a toner in which low molecular weight polypropylene is mixed with styrene resin, but in order to obtain a sufficient offset resistance effect, it is necessary to contain a large amount of low molecular weight polypropylene. However, this has the drawback that the toner cohesiveness increases and the development characteristics become poor. An object of the present invention is to provide a developing powder having excellent physical and chemical properties that overcome the above-mentioned toner defects. Another object of the present invention is to provide a developing powder that can be used with a hot roller fixing device that does not apply oil. A further object of the present invention is to provide a developing powder that allows stable, clear, and fog-free images to be obtained at all times. Another object of the present invention is to provide a developing powder that has excellent impact resistance, does not cause aggregation, has excellent fluidity, is durable, and has a low fixing temperature. A further object of the present invention is to provide a developing powder that is less likely to adhere to carriers, toner holding members, photoreceptor surfaces, cleaning blades, etc., and less likely to damage them. Specifically, the purpose of the present invention is to combine 50 to 90 parts by weight of styrene copolymer A (molecular weight M _A corresponding to the peak position in the GPC chromatogram, copolymerization ratio W A of styrene monomer W _A weight %) and styrene copolymer A 50 to 10 parts by weight of copolymer B (molecular weight M _B corresponding to the peak position in the GPC chromatogram, copolymerization ratio W _B of styrene monomers) and a binder resin (however, styrene copolymer A and styrene The total amount of copolymer B is 100 parts by weight),
The styrenic copolymer A and the styrenic copolymer B have an M _A of 10 ³ to 8×10 ⁴ and an M _B of 10 ⁵ to 2
×10 ⁶ , M _A < M _B , W _A > W _B , and W _A is
It is an object of the present invention to provide a developing powder for hot roller fixing, which satisfies the conditions that W _B is 70 to 98% by weight and W B is 50 to 90% by weight. Here, preferred copolymerization components of the styrenic copolymer are:
These include acrylic acid alkyl esters (the alkyl group has 1 to 15 carbon atoms), methacrylic acid alkyl esters (the alkyl group has 2 to 15 carbon atoms), and the like. The key points of the present invention are, first, that the binder resin is a mixture of styrene copolymers with different average molecular weights, and second, that the copolymerization ratio of styrene monomers in the copolymer with a high average molecular weight is lower than the average molecular weight. Thirdly, the copolymer is preferably a styrene-acrylic copolymer. This results in the following characteristics. The first characteristic is that a polymer with a high average molecular weight provides good offset resistance and anti-stick properties, and a polymer with a low average molecular weight provides a low fixing temperature. Such preferable characteristics cannot be obtained with a toner whose binder resin is a polymer having only one peak in its molecular weight distribution curve. The second feature makes the above trend more favorable. In other words, a polymer with a low average molecular weight can be made by increasing the content of styrenic monomer.
Excellent development characteristics and anti-blocking characteristics, and T _g
However, since the molecular weight is low, there is almost no increase in the fixing temperature. Further, in the case of a polymer having a high average molecular weight, by reducing the content of styrene monomer, the fixing temperature can be lowered. The third feature is that the combination of monomers provides excellent properties in both development and fixing. This seems to be due to the fact that the styrene monomer contributes more to development and the acrylic monomer contributes more to fixing. From the above explanation, it is clear that there is a preferable range for the monomer amount, molecular weight, etc. of the polymer used in the present invention. 10 ³ to 8×10 ⁴ and 10 ⁵ in the chromatogram measured by GPC (hereinafter referred to as GPC)
Preference is given to polymer mixtures having at least one local maximum in each region of ˜2×10 ⁶ . Such polymer mixtures have molecular weights between 10 ³ and 8×10 ⁴ and 10 ⁵
The molecular weight may be adjusted at the synthesis stage so that each has at least one maximum value in the region of ~2×10 ⁶ , or the styrenic copolymer has a maximum value in the region of 10 ³ to 8× ¹⁰ Combined A and molecular weight
It may be prepared by mixing with styrenic copolymer B having a maximum value in the region of 10 ⁵ to 2×10 ⁶ . In the GPC chromatogram, if the maximum value of the molecular weight of styrene copolymer B is 10 ⁵ or less, the impact resistance and durability of the toner decrease, and the
When it is 10 ⁶ or more, the fixing temperature of the developing powder becomes high.
In addition, the maximum value of the molecular weight of styrenic copolymer A is
If it is less than ¹⁰³ , the toner tends to aggregate,
The fluidity of the developer powder decreases, and on the other hand, if it is 8×10 ⁴ or more, the fixing temperature of the developer powder increases. In the present invention, a known ordinary method may be used to measure the molecular weight at the peak position of the molecular weight distribution of the polymer. For example, an appropriate method for normal gel permeation chromatography may be used as described below. 1 Measurement conditions Temperature: 25℃ Solvent: Tetrahydrofuran Flow rate: 1ml/min Sample concentration: 8mg/ml tetrahydrofuran solution Sample injection amount: 0.5ml 2 Column To properly measure the molecular weight range of 10 ³ to 2 × 10 ⁶ The column used is a combination of multiple commercially available polystyrene gel columns. For example, μ-Styragel 500, 10 ³ , 10 ⁴ , 10 ⁵ manufactured by Waters
Combinations in which 2 to 4 wires are selected from among them, combinations in which 2 to 4 wires are selected from among Showa Denko's Shode×A-802, 803, 804, and 805 are suitable. 3 Inspection lines Inspection lines shall be created using standard polystyrene. Examples of standard polystyrene include
Pressure Chemical Co. or Toyo Soda Kogyo Co., Ltd. with a molecular weight of 6×10 ² , 2.1×10 ³ , 4×10 ³ ,
1.75×10 ⁴ , 5.1×10 ⁴ , 1.1×10 ⁵ , 3.9×10 ⁵ , 8.6×
10 ⁵ , 2×10 ⁶ , 4.48×10 ⁶ , and it is appropriate to use standard polystyrene with at least about 10 points. 4 Detector An R1 (refractive index) detector is used as the detector. In the latter case, the mixing ratio of A and B is B/A=2/
1 to 1/20 is good. In the range of B/A>2, the fixing temperature becomes high, which is not preferable. In the region of B/A<1/20, the effect of mixing A and B is hardly recognized. More preferably, B/A=1 to 1/10. Styrene monomers applicable to styrenic copolymers include styrene, α-methylstyrene,
There are styrene and its substituted products such as P-chlorostyrene. Preferred copolymerization components are acrylic acid alkyl esters (alkyl group has 1 to 15 carbon atoms),
It is a methacrylic acid alkyl ester (alkyl group has 2 to 15 carbon atoms). Other copolymerizable components include acrylonitrile, maleic acid, maleic ester, methyl methacrylate, methyl acrylate, vinyl chloride, vinyl acetate, vinyl benzoate, vinyl methyl ketone, vinyl hexyl ketone, vinyl methyl ether, vinyl ethyl ether, A vinyl monomer such as vinyl isobutyl ether may be contained in an amount of 30% by weight or less (preferably 20% by weight or less) based on the weight of the polymer. The copolymerization ratio of the styrene monomers is 70 to 98% by weight for the copolymer A and 50 to 90% by weight for the copolymer B. As mentioned above, styrenic copolymer A
When the copolymerization ratio of styrenic monomers in styrene-based copolymer B is 70% by weight or less, and when the copolymerization ratio of styrene-based monomers in styrene-based copolymer B is 50% by weight or less,
The development characteristics, blocking resistance, offset resistance, etc. of the developing powder deteriorate. On the other hand, styrene copolymer A
When the copolymerization ratio of the styrene monomers and B is larger than the range of the present invention, the fixing temperature becomes high. The styrenic copolymer used in the present invention is synthesized by known methods such as suspension polymerization, emulsion polymerization, solution polymerization, and bulk polymerization. In addition, in order to adjust the molecular weight, a known molecular weight regulator,
For example, mercaptans such as lauryl mercaptan, phenyl mercaptan, butyl mercaptan, and dodecyl mercaptan, and halogenated carbons such as carbon tetrachloride and carbon tetrabromide can be used. Furthermore, as the binder resin for the developing powder of the present invention, other known resins may be mixed in addition to the above-mentioned polymers.
For example, there are polyester resins, epoxy resins, silicone resins, polystyrene, polyamide resins, polyurethane resins, acrylic resins, etc.
The amount should not exceed 30 weight percent of the total binder resin. All known coloring materials can be used in the developing powder of the present invention, such as carbon black, iron black, nigrosine, benzidine yellow, quinacridone, rhodamine B, and phthalocyanine blue. Further, in order to use the developing powder of the present invention as a magnetic developing powder, magnetic powder may be contained. Such magnetic powders include substances that are magnetized when placed in a magnetic field, such as powders of ferromagnetic metals such as iron, cobalt, and nickel, and compounds such as magnetite, hematite, and ferrite. The content of this magnetic powder is 15 to 70% by weight based on the weight of the developing powder. Further, additives can be added to the developing powder of the present invention for various purposes. Such additives include metal complexes, charge control agents such as nigrosine, polytetrafluoroethylene, polyethylene, polypropylene, fatty acids or their metal salts, lubricating compounds such as bisamides,
These include plasticizers such as dicyclohexyl phthalate. In particular, for the developing powder of the present invention, the melt viscosity at 140°C is 10 to 10 ⁶ CPS, preferably 10 ² to
10 ⁵ A very small amount of CPS ethylene olefin polymer, such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ionomer having a polyethylene skeleton, etc., is developed. By containing the powder in an amount of 0.1 to 5% by weight, preferably 0.2 to 3% by weight based on the weight of the powder, fixing characteristics and developing characteristics are further improved. In addition, the content of ethylene-based olefin polymer is
When the amount is less than 0.1% by weight, the effect of addition is small, and when it is more than 5% by weight, the agglomeration of the developer powder increases and the fluidity of the developer powder decreases. Furthermore, the developing powder of the present invention is mixed with carrier particles such as iron powder, glass beads, nickel powder, ferride powder, etc., if necessary, and used as a developer for electrical latent images. It can also be used in combination with hydrophobic colloidal silica fine powder for the purpose of improving the free-flowing property of the powder, and abrasive fine particles such as cerium oxide for preventing toner sticking. As a method for fixing the developer powder of the present invention on a support, a known hot roll fixing method can be applied, but
After conducting various tests, it was found that a fixing device in which the surface material of the fixing roller is made of fluororesin is the most preferable. [Example 1] 70 parts by weight of styrene-butyl acrylate copolymer (monomer weight ratio 8:2) having a peak at molecular weight 12000 in GPC chromatogram, molecular weight
30 parts by weight of styrene-butyl acrylate copolymer having a peak at 210,000 (monomer weight ratio 6:4), 60 parts by weight of magnetic powder (Fe ₃ O ₄ with an average particle size of 0.3μ),
Two parts by weight of a metal-containing dye (trade name, Zapon First Black B, manufactured by BASF) were ground and mixed in a ball mill, and then melted and kneaded in a roll mill. After cooling, it was coarsely pulverized using a hammer mill, and then finely pulverized using a supersonic jet pulverizer. The obtained powder was classified using an air classifier, and particles of approximately 5 to 35 μm were collected and used as developing powder. 0.3 parts by weight of hydrophobic colloidal silica powder was added to 100 parts by weight of this developing powder and mixed to prepare a developer. Image formation was performed using this developer. The surface of the insulating layer of the photosensitive drum, which consists of three layers: an insulating layer made of polyester resin, a photosensitive layer made of CdS and acrylic resin, and a conductive substrate, is uniformly charged by +6 KV corona discharge at a linear surface speed of 168 mm/sec of the drum. and then at the same time as the original image irradiation.
After performing a 7KV AC corona discharge, the entire surface is uniformly exposed to form an electrical latent image on the surface of the photoreceptor. This latent image was developed using the developing device shown in FIG.
In the figure, reference numeral 1 denotes a photosensitive drum which rotates at a constant speed in the direction of the arrow. The conductive substrate 1a is electrically grounded. 1b is a photosensitive layer covered with an insulating layer. 2 is a 50 mm cylindrical sleeve for carrying and transporting the developer. The cylindrical sleeve has a magnet roll 5 non-rotatingly held in the circular part, has a surface magnetic flux density of 700 Gauss, has the same circumferential speed as the photosensitive drum 1 (rotation direction is opposite), and has a surface between the photosensitive drum surface and the sleeve surface. Distance set at 0.15mm, 200Hz on sleeve surface
An AC bias of 600V is applied. Reference numeral 3 denotes a container containing an insulating magnetic developer 6, which is arranged so that the developer contained therein comes into contact with the surface of the cylinder 2. 4 is an iron blade placed at a distance of 0.1 mm from the cylinder 2. The blade 4 regulates the amount of developer moving on the cylinder 2 toward the developing section. After developing with the above developing device, + from the back of the transfer paper.
Transfer the powder image while irradiating with 7KV DC corona,
A duplicate image was obtained. The fuser is a commercially available copier (product name: NP-200J,
A fixing device manufactured by Canon was used. A clear image without fogging was obtained. The fixing properties were good, and no sticking to the fixing roller or offset phenomenon was observed. [Comparative Example 1] 100 parts by weight of styrene-butyl acrylate copolymer (monomer weight ratio 8:2) having a peak at a molecular weight of 12,000 in GPC chromatogram, magnetic powder
The same procedure as in Example 1 was carried out except that a developing powder was prepared from 60 parts by weight and 2 parts by weight of the metal-containing dye. A portion of the toner image was offset to the fuser roller, resulting in a poor image. [Comparative Example 2] 100 parts by weight of a styrene-butyl acrylate copolymer (monomer weight ratio 6:4) having a peak at a molecular weight of 210,000 in a GPC chromatogram, 30 parts by weight of magnetic powder, and 2 parts by weight of a metal-containing dye to a developing powder Example 1 was carried out in the same manner as in Example 1, except that .
Fixation was poor. [Comparative Example 3] A toner was prepared from 100 parts by weight of a styrene-butyl acrylate copolymer (monomer weight ratio 7:3) having a peak at a molecular weight of 100,000 in a GPC chromatogram, 60 parts by weight of magnetic powder, and 2 parts by weight of a metal-containing dye. The procedure was the same as in Example 1 except for the preparation.
The retention was unsatisfactory. [Comparative Example 4] Example 1 except that only 100 parts by weight of a styrene-butyl acrylate copolymer (monomer weight ratio 8:2) having a maximum molecular weight of 92,000 in the GPC chromatogram was used as the binder resin. A developing powder was prepared in the same manner as above. Further, when development, transfer and fixing were performed in the same manner as in Example 1, Example 1 was inferior in heat fixability compared to developer powder. [Example 2] Styrene-butyl acrylate copolymer (monomer weight ratio 7:3) having a peak at a molecular weight of 45,000 in the GPC chromatogram, 90 parts by weight, molecular weight
10 parts by weight of styrene-butyl acrylate copolymer having a peak at 800,000 (monomer weight ratio 5:5), 50 parts by weight of magnetic powder (ferrite with an average particle size of 0.2μ), 2 parts by weight of metal-containing dye, 5 parts by weight of carbon black. Example 1 except that developing powder was prepared from parts by weight.
I did the same thing. A clear image without fogging was obtained. The fixing properties were also good. [Example 3] Styrene-butyl acrylate-butyl maleate copolymer (monomer weight ratio 7.5:
2:0.5) 80 parts by weight, styrene-butyl acrylate-butyl maleate copolymer having a peak at a molecular weight of 450,000 (monomer weight ratio 6.5:3:0.5) 20
parts by weight, 2 parts by weight of metal-containing dye, magnetic powder (average particle size
Good results were obtained when the same procedure as in Example 1 was conducted except that a developing powder was prepared from 70 parts by weight of 0.3 μm Fe ₃ O ₄ ). [Example 4] 50 parts by weight of styrene-butyl methacrylate copolymer (monomer weight ratio 8:2) having a peak at molecular weight 12000 in GPC chromatogram, molecular weight
A developing powder was prepared from 50 parts by weight of styrene-butyl methacrylate copolymer (monomer weight ratio 7:3) having a peak at 183,000, 6 parts by weight of carbon black, 2 parts by weight of metal-containing dye, and 2 parts by weight of ultramarine. 12 parts by weight of developing powder and carrier iron powder (product name,
EFV250/400, manufactured by Nippon Tetsuko Co., Ltd.) was mixed with 88 parts by weight, and an image was printed using a commercially available copying machine (trade name, NP-5000, manufactured by Canon). A clear image without fogging was obtained. Furthermore, the fixing properties were also good. [Example 5] In GPC chromatogram, 80 parts by weight of styrene-butyl methacrylate copolymer (monomer weight ratio 9:1) having a peak at a molecular weight of 16,000, styrene-butyl methacrylate-methacrylic acid having a peak at a molecular weight of 380,000 A developing powder was prepared in the same manner as in Example 1, except that a developing powder was prepared from 20 parts by weight of lauryl (monomer weight ratio 7:2:1), 50 parts by weight of magnetic powder, and 2 parts by weight of metal-containing dye. The results were obtained. [Example 6] 75 parts by weight of styrene-butyl acrylate copolymer (monomer weight ratio 8:2) having a peak at a molecular weight of 12,000 in the GPC chromatogram, molecular weight
25 parts by weight of styrene-butyl acrylate copolymer having a peak at 210,000 (monomer weight ratio 6:4), 2 parts by weight of polyethylene with a melt viscosity of 4300 CPS at 140°C, 60 parts by weight of magnetic powder, 2 parts by weight of metal-containing dye. Example 1 was carried out in the same manner as in Example 1 except that a toner was prepared from the toner.A good image without fogging was obtained, and the fixability was also very good. The fixing temperature, offset resistance, and fog density of Examples and Comparative Examples are shown below.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a developing device using a magnetic developer. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... Cylindrical sleeve, 4... Blade, 5... Magnet roll, 6... Magnetic developer.

Claims (1)

[Scope of Claims] 1 50 to 90 parts by weight of styrenic copolymer A (molecular weight M _A corresponding to the peak position in the GPC chromatogram, copolymerization ratio W A of styrene monomers W _A weight %) and styrenic copolymer B50 ~10 parts by weight (GPC
The molecular weight M _B corresponding to the peak position in the chromatogram, the copolymerization ratio W _B of the styrene monomer (weight%) and the binder resin (however, the styrene copolymer A
and styrenic copolymer B is 100 parts by weight), and the styrenic copolymer A and the styrenic copolymer B have an M _A of 10 ³ to 8×10 ⁴ , M _B is 10 ⁵ ~
2×10 ⁶ , M _A < M _B , W _A > W _B , and W _A
70 to 98% by weight and W _B is 50 to 90% by weight. 2. The developer powder for hot roller fixing according to claim 1, wherein the copolymerization component of the styrenic copolymer is an acrylic acid alkyl ester. 3. Claim 1, wherein the copolymerization component of the styrenic copolymer is an alkyl methacrylate ester.
Developing powder for heat roller fixing as described in . 4. The developer powder for heat roller fixing according to claim 1, wherein the magnetic powder is contained in an amount of 15 to 70% by weight based on the weight of the developer powder. 5 An ethylene olefin polymer with a melt viscosity of 10 to 10 ⁶ CPS at 140°C is
The developer powder for hot roller fixing according to claim 1, which contains 0.1 to 5% by weight.