JPS6332382B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an image forming method used in electrophotography, electrostatic recording, magnetic recording, etc. 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, it is fixed using heat, pressure, or solvent vapor to obtain a copy. Further, when a step of transferring a toner image is included, a step for removing residual toner is usually provided. Examples of methods for visualizing electrical latent images using toner include 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 the US Pat. The powder cloud method described in U.S. Patent No.
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 system 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 types of toner, 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 fogging phenomenon. Among these undesirable phenomena, there are phenomena caused by the fragility of toner particles. If the toner is brittle, it will be 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 incomplete. This may cause undesirable phenomena such as fogging. 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. On the other hand, if the toner is too hard, it becomes impossible to mechanically crush it, making it difficult to actually manufacture the toner. Conventionally, for the above-mentioned reasons, relatively low molecular weight (several thousand) polystyrene or styrene-butyl methacrylate copolymer having appropriate hardness has been used as a binder resin for toner. However, recently there has been an extremely strong demand for improving the reliability of copying machines. Additionally, copying machine manufacturers are currently striving to develop and produce copying machines with longer lifespans from the viewpoint of maintenance-free use. Under these circumstances, when we reviewed the various properties of toners, we found that the relatively low molecular weight polystyrene or styrene-butyl methacrylate copolymer used as binder resins for toners was not sufficiently hard. It was found that a material with even higher hardness was needed. An object of the present invention is to provide an image forming method using a developing powder having excellent physical and chemical properties that overcome the above-described toner defects. Another object of the present invention is to provide an image forming method using a developer 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 an image forming method that uses developer powder that is less likely to adhere to the carrier, toner holding member, photoreceptor surface, cleaning blade, etc. and less likely to damage them, and that includes a cleaning blade step. It is something. A further object of the present invention is to provide an image forming method that allows stable, clear, and fog-free images to be obtained at all times. Specifically, the object of the present invention is to use a binder resin component that has a molecular weight of 10 ³ in a chromatogram measured by gel permeation chromatography.
A styrenic copolymer containing styrene as a main component or a styrenic copolymer containing styrene as a main component, having at least one maximum value in each molecular weight region of ~8×10 ⁴ and a molecular weight of 10 ⁵ to 2×10 ⁶ Contains a mixture of coalescence and 15 to 70% by weight of developer powder.
% by weight of magnetic fine particles and 0.5 to 0.5 to ethylene olefin monopolymer or ethylene olefin copolymer having a melt viscosity of 10 to 10 ⁶ CPS at 140°C.
A step of developing a latent image with an insulating magnetic developer powder containing 5% by weight, a step of transferring the generated developed image to a transfer member, and a blade cleaning method to remove the remaining developer powder on the latent image holder. An object of the present invention is to provide an image forming method characterized by comprising a step of removing the image using a method. What effectively contributes to achieving the above-mentioned object is a vinyl polymer having a maximum value of the GPC chromatogram in the molecular weight range of 10 ⁵ to 2×10 ⁶ . If the maximum value of the molecular weight is less than 10 ⁵ , the impact resistance and durability of the toner will decrease;
If it is ¹⁰⁶ or more, the toner fixing temperature will be high.
However, as the amount of polymers having a molecular weight in this range increases, an undesirable phenomenon occurs in that the fixing temperature becomes high for thermal fixing. Therefore, as will be described later, it is necessary to appropriately mix polymers whose maximum values are in the region of 10 ³ to 8×10 ⁴ in the GPC chromatogram. If the maximum value of the molecular weight is 10 ³ or less, the toner tends to aggregate and the fluidity of the toner also decreases. On the other hand, 8×10 ⁴
If the temperature is higher than that, the toner fixing temperature becomes high. still,
In the GPC chromatogram of the binder resin, if the maximum value of the molecular weight is only in the region of 10 ⁵ to 2×10 ⁶ , the fixing temperature of the toner will be high ^; If it is only in the 10 ⁴ range, the impact resistance and durability of the toner will decrease.
Such a polymer may be adjusted at the synthesis stage so that the molecular weight in the GPC chromatogram has at least one maximum value in the regions of 10 ³ to 8×10 ⁴ and 10 ⁵ to 2×10 ⁶ . or a polymer having a maximum molecular weight between 10 ³ and 8×10 ⁴
It may also be created by mixing (A) with a polymer (B) having a maximum molecular weight of 10 ⁵ to 2×10 ⁶ . In the latter case, the mixing ratio of polymers A and B is B/A=2/1~
1/50 is good. In the range of B/A>2, it is not preferable to use a currently commonly used thermal fixing method because it requires a large amount of thermal energy. In the region of B/A<1/50, no effect of mixing A and B is observed. Further, A and B do not necessarily have to have the same composition, but it is preferable that the main components of the monomers are the same. In the present invention, a known conventional method can be used to measure the molecular weight at the peak position of the molecular weight distribution of the vinyl polymer or copolymer. For example, an appropriate method for normal gel vermi- ation chromatography may be used as described below. 1 Measurement conditions Temperature: 25°C Solvent: Tetrahydrofuran Flow rate: 1 ml/min Sample concentration: 8 mg/ml tetrahydrofuran solution Sample injection amount: 0.5 ml 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 manufactured by Waters,
A combination of 2 to 4 wires selected from 10 ³ , 10 ⁴ , and 10 ⁵ , or Shodex A-802 manufactured by Showa Denko Co., Ltd.
A combination of two to four of 803, 804, and 805 is suitable. 3 Calibration curve When creating a calibration curve, use standard polystyrene. Examples of standard polystyrene include those manufactured by 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
x10 ⁵ , 8.6 x 10 ⁵ , 2 x 10 ⁶ and 4.48 x 10 ⁶ , and it is appropriate to use standard polystyrene with at least about 10 points. 4 Detector An RI (refractive index) detector is used as the detector. Examples of vinyl monomers applicable to the present invention include styrene, α-methylstyrene, p-chlorostyrene and other substituted products thereof, acrylic acid, methyl acrylate, ethyl acrylate,
Butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate,
Monocarboxylic acids having double bonds such as butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, etc., or substituted products thereof, such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate, etc. dicarboxylic acids and substituted products thereof, such as vinyl esters such as vinyl chloride, vinyl acetate, vinyl benzoate, etc.; vinyl ketones, such as vinyl methyl ketone, vinyl exyl ketone, etc.; Vinyl monomers such as vinyl ethers such as ether, vinyl ethyl ether, vinyl isobutyl ether, etc. may be used alone or in combination of two or more. Among these, styrenic copolymers were preferred. A vinyl polymer having the above GPC chromatogram is used as a binder resin component in the total weight of developer powder.
It is contained in an amount of at least 50% by weight (more preferably at least 50% by weight). In addition to the binder resin component described above, the developing powder according to the present invention may contain the following compounds in a proportion smaller than the content of the binder resin component. For example, silicone resin, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax etc. When the developer powder used is magnetic developer powder, the magnetic fine particles contained in the magnetic developer powder may be any material that exhibits magnetism or can be magnetized, such as iron,
These include metals such as manganese, nickel, cobalt, and chromium, magnetite, hematite, various ferrites, manganese alloys, and other ferromagnetic alloys. can be used.
The amount of magnetic fine particles contained in the magnetic developer powder is 15 to 70% by weight (more preferably
25-45% by weight) is good. Further, various substances can be added to the developer powder, ie, the toner, used in the present invention for the purpose of coloring, controlling charge, etc. For example, carbon black,
These include iron black, graphite, nigrosine, metal complexes of monoazo dyes, ultramarine blue, phthalocyanine blue, Hansa yellow, benzine yellow, and various quinacridone lake pigments. Alternatively, 10 to 40% by weight of hydrophobic colloidal silica or the like may be contained in the developer powder as a fluidity improver. Of course, this fluidity improver may be used by being mixed outside the developing powder, and the amount added in that case is 0.5 to 5% by weight (based on the weight of the developing powder). The developer powder made from the above-mentioned binder resin, magnetic powder, colorant, charge control agent, etc. has strong resistance to the load applied in the developing device, and did not break and deteriorate in durability tests. . However, because the toner particles are hard, there is a risk that other materials used in the copying machine, such as the surface of the photoreceptor, the cleaning member, the surface of the developing sleeve, the carrier particles, etc., may become susceptible to wear or scratches. Therefore, the melt viscosity at around 140℃ is
Improvements were made by adding a small amount of ethylene olefin monopolymer or ethylene olefin copolymer at 10 to 10 ⁶ cps. When adding this additive, if it is added outside the developer powder, the weight ratio with the developer powder will change during repeated use and the development characteristics will change, so this additive should be included in the developer powder. It is better. When 0.5 to 5% by weight of an olefin polymer having a viscosity within the above range is contained in the developer powder, the dispersibility and compatibility of pigments and magnetic fine particles with the developer powder are improved.
There is little adverse effect on the surface of the photoreceptor, the cleaning member, etc., and the photoreceptor can be cleaned well with the cleaning blade. Examples of the ethylene olefin monopolymer or ethylene olefin copolymer used here include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer,
Examples include ethylene-ethyl acrylate copolymers and ionomers having a polyethylene skeleton. Among the above copolymers, those containing olefin monomers in an amount of 50 mol% or more (more preferably 60 mol% or more) are preferred. The Brookfield method was used to measure the melt viscosity, and here a B-type viscometer equipped with a small sample adapter was used. Next, an electrophotographic method using the developing powder according to the present invention will be explained. The step of developing the electrical latent image using toner includes the aforementioned magnetic brush method, cascade development method, powder cloud method, method using conductive magnetic toner described in U.S. Pat. No. 3,909,258, Tokukai Akira
There is a method using a high-resistance magnetic toner described in Japanese Patent No. 53-31136. The developing powder according to the present invention is also suitable for a developing method using a so-called one-component developer containing magnetic fine particles. In the process of transferring the developed image used in the present invention to a transfer target member, a corona transfer method, a bias transfer method, an electrostatic transfer method such as a method using a conductive roller, a method of transferring using a magnetic field, etc. are used. . Further, in the present invention, a blade cleaning method is applied to the step of removing residual toner on the photosensitive layer or the insulating layer. Note that the cleaning blade is preferably made of polyurethane. In addition, the powder image on the transferred member needs to be fixed on the member, and methods for this purpose include heat fixing method, heat pressure fixing method, solvent fixing method, flash fixing method, laminate fixing method, etc. Can be used. Example 1 80 parts by weight of a styrene-butyl acrylate copolymer (monomer weight ratio 65:35) with an average molecular weight of 9,000 and 20 parts by weight of a styrene-butyl acrylate copolymer (65:35) with an average molecular weight of 205,000 were mixed. 100 parts by weight of a polymer mixture having maximum values of 10,500 and 220,000 in the molecular weight distribution curve determined by GPC, 60 parts by weight of magnetic powder (Fe ₃ O ₄ with an average particle size of 0.3μ), metal-containing dye (trade name, Pomelo First) Black B, BASF
) 2 parts by weight, melt viscosity at 140℃ is 4300 cps
2 parts by weight of polyethylene were pulverized and mixed in a ball mill, and then melt-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 cylindrical sleeve with a diameter of 50 mm for carrying and transporting the developer. The cylindrical sleeve has a magnet roll 5 non-rotatably held in the circular part and has a surface magnetic flux density of 700.
Gauss, has the same circumferential speed as photosensitive drum 1 (rotation direction is opposite), the distance between the photosensitive drum surface and the sleeve surface is set to 0.15 mm, and the sleeve surface has a
AC bias of Hz600V is applied. Reference numeral 3 denotes a container containing insulating magnetic developer powder 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 applied as it moves 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 remaining developer on the photosensitive drum was removed with a polyurethane blade, and fixing was performed using a commercially available plain paper copying machine (trade name: NP-5000, manufactured by Canon). A good image without fogging was obtained. Even after a running test of 100,000 sheets, good images with high image density were obtained. In addition, almost no scratches or toner adhesion were observed on the photosensitive drum, cleaning blade, developing sleeve, etc. Comparative Example 1 The same procedure as in Example 1 was carried out except that 100 parts by weight of the styrene-butyl acrylate copolymer with an average molecular weight of 9,000 was used and the styrene-butyl acrylate copolymer with an average molecular weight of 205,000 was not used. . Although the initial image was good, fog increased during the running test and the copy quality was poor. The image data of Example 1 and Comparative Example 1 are shown in the following table.

[Table] Comparative Example 2 A developing powder was prepared in the same manner as in Comparative Example 1 except that it did not contain 2 parts by weight of polyethylene having a melt viscosity of 4300 cps at 140°C. The obtained developer powder had worse development characteristics than the developer powder of Comparative Example 1. Example 2 Styrene-butyl acrylate-butyl maleate copolymer with an average molecular weight of 50,000 (monomer weight ratio
70:20:10) 92 parts by weight and styrene-butyl acrylate copolymer (65:35) with an average molecular weight of about 800,000 8
100 parts by weight of a polymer mixture having maximum values between 61,000 and about 1,000,000 in the molecular weight distribution curve determined by GPC, 50 parts by weight of magnetic powder (ferrite with an average particle size of 0.2μ), 2 parts by weight of a metal-containing dye, 140 parts by weight Good results were obtained in the same manner as in Example 1, except that a toner was prepared from 3 parts by weight of polyethylene having a melt viscosity of about 30,000 cps at °C and 5 parts by weight of carbon black. Example 3 GPC consisting of 65 parts by weight of a styrene-butyl methacrylate copolymer (monomer weight ratio 7:3) with an average molecular weight of 21,000 and 35 parts by weight of a styrene-butyl methacrylate copolymer (7:3) with an average molecular weight of 260,000.
100 parts by weight of a polymer mixture having maximum values between 22,000 and 275,000 in the chromatogram, 50 parts by weight of magnetic powder (Fe ₃ O ₄ with an average particle size of 0.3μ), 2 parts by weight of a metal-containing dye, and the melt viscosity at 140°C. Good results were obtained in the same manner as in Example 1 except that the toner was prepared using 3 parts by weight of polyethylene of about 4300 cps. Example 4 40 parts by weight of styrene-butyl acrylate copolymer with an average molecular weight of 14,000 (monomer weight ratio 65:35),
In a GPC chromatogram consisting of 60 parts by weight of styrene-butyl acrylate-acrylonitrile copolymer (65:30:5) with an average molecular weight of 170,000.
Polymer mixture with maxima at 14000 and 180000
100 parts by weight, magnetic powder (Fe ₃ O ₄ with average particle size 0.3μ) 40
Good results were obtained when the toner was prepared in substantially the same manner as in Example 1, except that a toner was prepared using 1 part by weight, 2 parts by weight of a metal-containing dye, and 2 parts by weight of polypropylene having a melt viscosity of 280 cps at 140°C. It was done. Example 5 80 parts by weight of styrene-butyl acrylate copolymer (65:35) with an average molecular weight of 9000 and an average molecular weight of 205000
20 parts by weight of a styrene-butyl acrylate (65:35) copolymer, 100 parts by weight of a polymer mixture with maximum values of 10,500 and 220,000 in the GPC chromatogram, magnetic powder (average particle size 0.35μ, axial Acicular magnetite (ratio 8/1) 70 parts by weight, metal-containing dye 2 parts by weight, melt viscosity at 140°C approximately 3×
Example 1 was carried out in substantially the same manner as in Example 1, except that a toner was prepared using 4 parts by weight of 10 ⁴ cps polyethylene, and good results were obtained. Comparative example 2 In GPC chromatogram, molecular weight is 220000
A developing powder was prepared in the same manner as in Example 1, except that only 100 parts by weight of a styrene-butyl acrylate copolymer (monomer weight ratio 65:35) having a maximum value of . Furthermore, when development, transfer and fixing were performed in the same manner as in Example 1, the heat fixability was inferior to that of the developer powder of Example 1. Comparative Example 3 Same as Example 1 except that only 100 parts by weight of a styrene-butyl methacrylate copolymer (monomer weight ratio 7:3) having a maximum molecular weight of 95,000 in the GPC chromatogram was used as the binder resin. A developing powder was prepared. Furthermore, when development, transfer and fixing were performed in the same manner as in Example 1, the heat fixability was inferior to that of the developer powder of Example 1.

[Brief explanation of drawings]

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 developing powder.

Claims (1)

[Claims] 1 As a binder resin component, the chromatogram measured by gel permeation chromatography shows a molecular weight of 10 ³ to 8 × 10 ⁴ and a molecular weight of 10 ⁵ to 2
A developer powder containing a styrene-based copolymer containing styrene as a main component or a mixture of styrene-based copolymers containing styrene as a main component, each having at least one maximum value in each molecular weight region of ×10 ⁶ 15 to 70% by weight of magnetic fine particles and 140
Developing a latent image with an insulating magnetic developer powder containing 0.5 to 5% by weight of an ethylene olefin monopolymer or ethylene olefin copolymer having a melt viscosity of 10 to ¹⁰⁶ CPS at °C; An image forming method comprising the steps of: transferring the developed image onto a transfer member; and removing residual developer powder on the latent image carrier using a blade cleaning method.