GB2104841A - Method of fixing toner image and apparatus therefor - Google Patents

Abstract

A heating roller fixing method and apparatus in which recording paper (14) bearing a toner image (13) thereon is conveyed by a heating roller (1) and a pressure roller (5) in pressure contact with said heating roller (1) to heat-fix said toner image, and a cleaning member (8) having a fiber material containing a high viscosity mold releasing agent on the surface thereof is brought into pressure contact with said heating roller (1). In an alternative embodiment, the clearing member may be a web urged against the fixing roller by a roller. The high viscosity agent may have a viscosity of 1,500-300,000 centistokes at 25 DEG C (preferably 2,000-60,000 cs), and be a silicone oil. The method and apparatus are of particular use in fixing a toner which includes a styrene homopolymer or copolymer with molecular weight at least 100,000 and a polyester containing at least 5% by wt. of a chloroform-insoluble component. <IMAGE>

Description

SPECIFICATION Method of fixing toner image and apparatus therefor This invention relates to a method of fixing a toner image, specifically to a fixing method of a toner image having improved durability and reliability and to a fixing apparatus equipped with a cleaning roller that does not need a mold releasing agent to be continuously fed from outside.

In electrostatic recording apparatuses in general such as an electrophotographic reproducing machine, various fixing apparatuses for fixing the toner image on the recording paper have been proposed in the past. In particular, a contact heating type fixing apparatus consisting, for example, of a rotatable heating roller with a built-in heat source and a pressure roller rotating in the same direction with the heating roller while in pressure contact with it has gained a wide application because the apparatus has high heat efficiency and yet no risk of fire.

In spite of these advantages, the contact heating fixing system has the following drawbacks. In this system, the toner image and the heating roller for fixing come into contact and in the course of extended periods of reproducing operation time, toner is deposited on the heating roller, attaches to a recording medium supporting a subsequent toner image thereon and stains the image to be fixed. The recording paper is likely to wind firmly to the heating roller because the resin component of the toner is fused on the surface of the heating roller. Accordingly, the toner deposited on the heating roller must be removed. Cleaning members such as a cleaning web, a cleaning blade, a cleaning roller have conventionally been employed for this purpose.However, the toner that has been cleaned should be also removed from these cleaning members and another cleaning member or device must be employed to remove this toner, or the cleaning roller should be replaced frequently.

A fixing system which prevents toner from being deposited on the heating roller for fixing has been also investigated and has been put into practical application in some reproducing apparatuses. For example, in one system of this kind, a mold releasing agent consisting of low viscosity silicone oil of about 30 to about 1000 centistokes is constantly supplied to the heating roller in order to prevent the toner from being deposited. This method provides the advantage that since the toner deposition on the heating roller is reduced, reproduction can be made without using the cleaning roller. However, this method invites new problems in that a feeder for the silicone oil must be additionally prepared, leaking oil would stain the apparatus, it is difficult to supply the oil uniformly, and the toner is deposited on portions where the oil is non-uniform and stains the image to be fixed.

With the background described above, the present invention is directed to provide a fixing method which can fix an excellent toner image without calling for a complicated procedure of constantly supplying the mold releasing agent from outside and also a fixing method which has high heat efficiency, is suitable for high speed reproduction and can provide a fixed image of high quality without stains.

In a method of fixing a toner image supported on a recording medium by heat-fixing the toner image with a heating roller in pressure contact with a cleaning member containing a high viscosity mold releasing agent, these objects of the present invention can be accomplished by a method of fixing a toner image, in which method the high viscosity mold releasing agent has a viscosity of 1,500 to 300,000 centistokes at 250C and preferably from 2,000 to 60,000 centistokes at 250C, and the toner image is formed by a toner using, as a binder resin, at least one member selected from the group consisting of homopolymer or copolymer of a styrenes (hereafter refer to styrenes type resin) containing at least 10 wt% of a high molecular weight component having a molecular weight of 100,000 and a polyester resin containing at least 5 wt% of a chloroform-insoluble component.

The fixing method in accordance with the present invention is a contact heat-fixing method using a heating roller and has the characteristic features that it has a high heat efficiency, is suitable for high speed reproduction, and fixing of a toner image with high quality can be continuously carried out for extended periods of time due to the synergy effect that the cleaning member contains a high viscosity mold releasing agent and the toner itself for forming the toner image contains a mold releasing agent.

It is another object of the present invention to provide a fixing apparatus which can fix an excellent toner image without calling for the complicated procedure of constantly supplying a mold releasing agent from outside.

It is still another object of the present invention to provide a fixing apparatus which has excellent heat efficiency, is suitable for high speed reproduction, and can fix the toner image without causing toner stains.

In a fixing apparatus including a heating roller which press and coveys recording paper supporting a toner image thereon in cooperation with a pressure roller and heat-fixes the toner image, these objects of the present invention can be accomplished by a fixing apparatus in which a cleaning member having on its cleaning surface a fiber material containing a high viscosity mold releasing agent having a viscosity of 1,500 to 300,000 centistokes and preferably, 2,000 to 60,000 centistokes, is brought into pressure contact with the heating roller, The fixing apparatus in accordance with the present invention includes, as its constituent elements, a heating roller having a heat-resistant, mold-releasing coating layer such as of Teflon (polytetrafluoroethylene, Trade Mark by Du Pont) on the surface of a metal core with a built-in resistance heater or a radiation heater, a pressure roller disposed to press, convey, and fix recording paper supporting a toner image thereon in cooperation with the heating roller and having a mold releasing coating layer of, for example, silicone rubber, on the surface of a metal core, and a cleaning member having on its cleaning surface a fiber material impregnated with silicone oil, liquid paraffin or the like having a viscosity of 1,500 to 300,000 centistokes at 25"C, preferably 2,000 to 60,000 centistokes at 250 C, in the coating layer of the fiber material.

As the mold releasing agent to be used in the present invention, a high viscosity silicone oil having a viscosity of 1,500 to 300,000 centistokes at 250C is preferably used. Examples of such a high viscosity silicone oil include "Shinetsu silicone KF96H" (produced by Shinetsu Chemicals Co., Ltd.), "Toray silicone SH--200" (produced by Toray Silicone Co., Ltd.), "Toshiba silicone TSF 451" (produced by Toshiba Silicone Co., Ltd.), and the like.

Examples of the cleaning member include a cleaning web formed by bonding a fiber material to a paper, cloth (preferably heat-resistant cloth) or plastic film, and a cleaning member formed by coating a metal core with a heat-resistant fiber or a porous flexible plastic material. The latter can be produced, for example, by first disposing a porous and preferably heat-resistant flexible layer such as silicone foam, and further disposing on the silicone foam a heat-resistant fiber material such as a fiber material finished in a felt form of Tetron (polyester, Trade Mark) on Nylon (polyamide, Trade Mark), or a fiber material made of an ordinary synthetic fiber or natural fiber that has been finished heat-resistant.

The flexible layer and/or the fiber material layer is impregnated in advance with the high viscosity mold releasing agent, and the reyion that cornes into contact with the heating roller is softened upon heating so that an extremely thin layer of the agent is applied to the heating roller. Thus, only the required quantity of the agent is uniformly applied to the heating roller as a whole. Deposition of toner from the toner image to the heating roller is remarkably reduced, and even if it does attach it is easily caught by the cleaning member which is wetted with the high viscosity mold releasing agent to be cleaned off, thereby improving the cleaning effect and extending the effective service life of the cleaning member.Among others, contact with the heating roller can be improved, cleaning can be effected uniformly and the cleaning member has a simple construction and an extended life.

The amount of the mold releasing agent to be charged in advance into the cleaning roller is up to 0.5 g per unit volume of the member impregnated with the mold releasing agent (such as the fiber material and/or a sponge flexible layer), and preferably at least 0.02 g. Generally, from 5 g to 50 g of the mold releasing agent is packed into a 30 cm/long cleaning roller.

The amount of mold releasing agent that is transferred from the cleaning roller and applied to the heating roller varies depending upon the temperature of the heating roller, the linear velocity of each of the heating roller and cleaning roller, their direction of rotation, and the kind and viscosity of the mold releasing agent. However, it is generally preferred that the amount is within the range of from 1 > c x 10-7 g/cm2 to 1 x 10-4 g/cm2.

Accordingly, once the mold releasing agent is sufficiently packed, copy work can be repeated as many as about hundreds of thousands of times without replacing the cleaning roller, and the cleaning roller need be replaced only after the mold releasing agent is fully consumed. The cleaning roller can be used again after it is cleaned and repacked with the mold releasing agent.

In the cleaning member in accordance with the present invention, the surface layer is coated with the fiber material through which the mold releasing agent is supplied, and the individual fibers form the feed passages for the mold releasing agent by the capillary action, for example, so that the mold releasing agent can be supplied extremely smoothly. Moreover, since the fiber material comes into gentle contact with the heating roller, the surface of the heating roller is not damaged.

These and other objects, features and advantages of the present invention will become more apparent from the following description in conjunction with the accompanying drawings.

Figures 1 and 2 are sectional views showing the fixing apparatus in accordance with the present invention.

In the present invention, when the cleaning member incorporating the high viscosity mold releasing agent therein is brought into pressure contact with the heating roller, the mold releasing agent is softened by the heat and is uniformly applied in a thin layer on the rotating surface of the heating roller, thereby forming a surface to which the toner can hardly attach. The mold releasing agent used herein is highly viscous, i.e.. from 1 5,000 to 300.000 centistokes, preferably from 2,000 to F0,000 centistoices. For tunis reason, it can stably be held inside tne cleaning member, and neither leaks to waste nor stains the apparatus and associated instruments. Since the mold releasing agent is highly viscous, the amount applied to the heating roller is small and the agent can be applied extremely thinly. This results in the advantage that a limited quantity of mold releasing agent held by the cleaning member can be effectively used for an extended period.

If the viscosity of the mold releasing agent is below 1,500 centistokes, the agent would leak from the cleaning member and the cleaning effect would be lost early. If the viscosity exceeds 300,000 centistokes, on the other hand, packing of the mold releasing agent to the cleaning member becomes difficult and the amount of the agent applied to the heating roller becomes so small that toner contamination on the heating roller would increase and the service life of the cleaning member would be reduced.

Because the mold releasing agent is highly viscous, toner that has been caught on the heating roller is easily collected by the high viscosity layer of the mold releasing agent on the cleaning member, exhibiting improved cleaning effects. On the other hand, since the layer of the mold releasing agent to be applied to the heating roller is extremely thin, the toner would be deposited on the heating roller.

However, this problem can be solved by furnishing the toner itself with the mold releasing property.

In the present invention, the high viscosity mold releasing agent is packed into the cleaning member such as a cleaning blade, cleaning web, cleaning roller, or the like. Among them, the cleaning roller is especially preferred because it has high rigidity and stability and is easy to use. A cleaning blade consists af a thin plate of metal, plastic, rubber or cloth which is impregnated or coated with a high viscosity mold releasing agent such as silicone oil, liquid paraffin or wax, preferably silicone oil. The cleaning web consists of paper, cloth or the like, preferably a heat-resistant fibrous sheet, which is impregnated with the above-mentioned mold releasing agent.

In the case of a cleaning roller, the member to be impregnated with the high viscosity mold releasing agent such as a flexible member of silicone foam is applied around the outer circumference oi a metal core and a heat-resistant fiber material layer such as Nylon or Teflon is further applied thereon.

These flexible member layer and fiber material layer are then impregnated with the high viscosity mold releasing agent. Generally, up to 0.5 g/cm3, preferably at least 0.02 g/cm3, of the mold releasing agent is packed into the member to be impregnated. The mold releasing agent to be coated on the heating roller is applied in a thin layer so as to cope with the changes caused by the temperature of the heating roller, the linear velocity of each of the heating roller and cleaning roller, their directions of rotation and the kind and viscosity of the mold releasing agent. In the case of an ordinary reproducing machine, the copy work can be repeated about hundreds of thousands of times without replacing the cleaning roller and without any problem if the maximum amount of high viscosity silicone oil is packed into the impregnation member.

When the mold releasing agent is fully consumed, the roller may be replaced. The heating roller can be used again after it is cleaned and repacked with the mold releasing agent.

The toner image in the present invention can be formed in the following manner. An electrostatic charge image is first formed on an electrostatic recording layer consisting of a dielectric and a photoconductive photosensitive layer such as a photosensitive layer containing an inorganic semiconductor, e.g., zinc oxide, lead oxide, mercury sulfide, cadmium sulfide, etc. dispersed in a binder resin, a selenium-deposited photosensitive layer, an organic photosensitive layer consisting of a charge generation layer containing perylene, Chlor Diane Blue or the like and a charge transfer layer containing oxazole, diarylalkane or the like, by charging and image-exposure or by signal charge application.The electrostatic charge image is then developed by a developer consisting of a carrier and a toner or a developer consisting principally of a magnetic toner in accordance with the various developing processes, such as a magentic brush developing process, to thereby form the toner image. In particular, the toner image in the present invention is characterized in that toner having the mold releasing property is employed.

The toner to be used for forming the toner image in accordance with the present invention uses a styrenes type resin containing a high molecular weight component and/or a polyester resin containing a chloroform-insoluble component as the binder and contains a pigment, and if necessary, a charge controlling agent as weli as a property improving agent.

The high molecular weight component and chloroform-insoluble component in the abovementioned binder resin are a high polymer and/or a cross-linked polymer and are mixed extremely uniformly with the rest of components. Preferably, these components are mixed in the form of fine latex particles or molecules. It is preferred that a resin containing both high and low molecular weight components be obtained in the synthesizing process.

The abovementioned styrene type resin containing the high molecular weight component contains at least 10 wt%, and preferably up to 60 wt%, of a high molecular weight component having a molecular weight of at least 100,000. If the content of the high molecular weight component is below 10 wt%, aggregation when the toner is fused is insufficient and the toner is likely to attach to the heating roller during fixing. If it exceeds 60 wt%, on the other hand, the milling characteristics as well as fixability during the toner production drop.

Incidentally, the molecular weight in the present specification is determined by Gel Permeation Chromatography under the following conditions. Measurement was carried out using a "Waters 200 Type GPC tester" (produced by Waters Co.) while 4 mg of a 0.2 g/dl concentration tetrahydrofuran sample solution (calculated as a sample), was charged into a column and while a solvent (tetrahydrofuran) was made to flow down at a rate of 1 ml/min at a temperature of 25"C. The combination of 1 106,1 06, -10 and -104 iS used as the columns to be used.

The monodisperse polystyrene standard samples for setting the working curve are polystyrene produced by Pressure Chemical Co. and have molecular weights of 1,800,000, 860,000, 41 1,000, 160,000, 98,200, 51,000, 19,800, 10,000 and 4,000. The tetrahydrofuran-insoluble component at the time of measurement has a molecular weight of at least 500,000 and is the high molecular weight component having a molecular weight of at least 100,000 in the present invention.

The styrene type resin to be used in the present invention includes a styrene homopolymer resin, a styrene-butadiene copolymer resin and a styrene-a-methylene aliphatic monocarboxylic acid esters copolymer resin and the like.

The abovementioned styrene type resin can be obtained by homopolymerizing the styrenes by selecting suitable polymerization conditions or by using a cross-linking agent, by copolymerizing the styrenes and butadiene or copolymerizing the styrenes and an a-methylene aliphatic monocarboxylic acid derivative such as an acrylic acid derivative and a methacrylic acid derivative.

The styrenes to be used for the abovementioned polymerization methods include styrene, o- methylstyrene, m-methylstyrene, p-methylstyrene, ci-methylstyrene, p-ethylstyrene, 2,4dimethylstyrene, p-n-butylstyrene, p-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, pchlorostyrene and the like, and preferable a styrene.

The styrenes-butadiene copolymer to be used in the present invention contains 70 to 98 wt%, preferably 85 to 98 wt%, of the styrenes component and the styrenes-butadiene copolymer is preferable. If a styrenes-butadiene copolymer whose styrenes content is below 70 wt% is used, the glass transition point of the binder drops and the resulting toner has the aggregating property such that it changes into mass during storage or inside the developing apparatus. On the other hand, if the styrenes-butadiene copolymer whose styrenes component exceeds 98 wt% is used, the softening point of the binder becomes higher and the fixing temperature range becomes narrower.

Examples of the acrylic or methacrylic acid derivative as the monomer component of the styrenesa-methylene aliphatic monocarboxylic acid esters copolymer to be used in the present invention include cr-methylene aliphatic monocarboxyiic acid esters such as an acrylates, e.g. methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate, 2-ethyihexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl a- chloroacrylate, and a methacrylates e.g. methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate; acrylic and methacrylic acid derivatives such as acrylontrile, methacrylonitrile, acryiamide, methacrylamide; and so forth.

Next, the method of synthesizing the styrene type resin binder in accordance with the present invention will be described with reference to the following Examples of Synthesis. First, the method of synthesizing the styrenes-butadiene copolymer resin will be described.

SYNTHESIS EXAMPLE 1 Dispersion medium water 180 parts by weight Monomers butadiene 10 parts by weight styrenes 90 parts by weight divinylbenzene 0.16 parts by weight Emulsifier potassium salt of aliphatic acia 2.2 parts by weight potassium salt of disproportionated resin acid 2.2 parts by weight potassium phosphate 0.4 parts by weight Polymerization initiation system ferrous sulfate 0.005 parts by weight p-methane hydroperoxide 0.02 parts by weight t-dodecylmercaptan 0.5 parts by weight The composition having the abovementioned recipe was placed in a 20-l autoclave purged with nitrogen gas, and the polymerization reaction was carried out at 50C. When the conversion ratio reached 70%, 0.2 parts by weight of N,N'-diethylhydroxylamine as a polymerization terminater was added to terminate the reaction.After 1 part by weight of a stabilizer was added to the resulting latex, calcium chloride as a coagulant was added to coagulate the polymer. The polymer was then dehydrated and dried to provide the styrene-butadiene resin. The resin contained 41 wt% of the high molecular weight component having a molecular weight of at least 100,000 and had a softening point of 141 OC by the ball and ring method.

SYNTHESIS EXAMPLE 2 The latex A of a low molecular weight resin was obtained in the same way as in Example of Synthesis 1 except that the amount of divinylbenzene and that of t-dodecylmercaptan in the recipe of Example 1 were changed to 0.16 parts by weight and to 1.3 parts by weight, respectively.

On the other hand, the latex B of a high molecular weight resin was obtained in the same way as ir Synthesis Example 1 except that the amounts of divinylbenzene and of t-dodecylmercaptan in the recipe of Example 1 were chanqed 0.16 parts by weight and to 0.4 parts by weight, respectively.

The latex A and B were mixed so that the solid ratio became 2:1. The mixed latex was treated in the same way as in Synthesis Example 1 to produce the styrene-butadiene resin. The resulting resin contained 28 wt% of the high molecular weight component having a molecular weight of at least 100,000 and had a softening point of 1 320C by the ball and ring method.

COMPARATIVE SYNTHESIS EXAMPLE 1 A styrene-butadiene resin was produced in the same way as in Synthesis Example 1 except that the amounts of divinylbenzene and of t-dodecylmercaptan in the recipe of Synthesis Example 1 were changed to 0.08 parts by weight and to 1.3 parts by weight, respectively. The resulting resin contained 8 wt% of the high molecular weight component having a molecular weight of at least 100,000, and had a softening point of 1 250C by the ball and ring method.

The method of synthesizing the styrene-acryl copolymer resin will now be described.

SYNTHESIS EXAMPLE 3 0.1 g of "Gosenol GH-1 7", a partially saponified polyvinyl alcohol (produced by Nippon Synthetic Chemicals Co., Ltd.) was dissolved in 100 ml of distilled water in a 11 separable flask and a monomer mixture having the following composition was dispersed and suspended in the solution. After the gaseous phase was purged with nitrogen, the temperature of the reaction system was raised to 800C and held at that temperature for 1 5 hours to carry out the polymerization and obtain a styreneacryl resin.

Composition of monomer mixture styrene 70 g butyl methacrylate 30 g benzoyl peroxide 0.4 g The resulting styrene-acryl resin contained 30 wt% of the high molecular weight component having a molecular weight of at least 100,000 and had a softening point of 1 390C by the ball and ring method.

SYNTHESIS EXAMPLE 4 0.1 g of "Gosenol GH-1 7" was dissolved in 100 ml of distilled water in a 11 separable flask and a monomer mixture having the following composition (a) was dispersed and suspended in the solution.

After the gaseous phase was purged with nitrogen, the temperature of the reaction system was raised to 800C for 1 5 hours to carry out polymerization. Thereafter, the temperature was reduced to 400C and monomer mixture (b) of the following composition was added. The mixture was stirred at 400C for 2 hours and a separately prepared solution containing 0.4 g of a partially saponified polyvinyl alcohol "Gosenol GH-1 7" dissolved in 100 ml of distilled water was added.The temperature was again raised to 800C and kept at this temperature for 8 hours, to carry out polymerization and produce a styreneacryl resin.

Monomer mixture Composition (a) , (b) styrenes 20 g 50 g methyl methacrylate 8 20 butyl methacrylate 12 30 benzoyl peroxide 0.08 2 a-methylstyrene (dimer) - 3

Incidentally, the abovementioned a-methylstyrene (dimer) was a mixture of 2,4-diphenyl-4 methyl-i -pentene and 2,4-diphenyl-4-methyl-2-pentene prepared in accordance with the disclosure of U.S. Patent Specification No. 2,429,719, and a fraction having a refractive index of 1.569 was used.

The styrene-acryl resin thus synthesized contained 33 wt% of a high molecular weight component having a molecular weight of at least 100,000 and a softening point of 1 40cm by the ball and ring method.

COMPARATIVE SYNTHESIS EXAMPLE 2 0.1 g of "Gosenol GH-1 7" was dissolved in 100 ml of distilled water in a 11 separable flask. A monomer mixture having the following composition was added to the solution and was dispersed and suspended. After the gaseous phase was purged with nitrogen, the temperature of the reaction system was raised to 800C and kept at that temperature for 1 5 hours, to thereby carry out polymerization and produce a styrene-acryl resin.

Composition of monomer mixture styrene 50 g methyl methacrylate 20 g butyl methacrylate 30 g benzoyl peroxide 2g n-methylstyrene (dimer) 3 9 The resulting styrene-acryl resin contained 3 wt% of a high molecular weight component having a molecular weight of at least 100,000 and had a softening point of 1 200C by the ball and ring method.

In the present invention, it is possible to use a polyester resin containing at least 5 wt% chloroform-insoluble component as a binder either in combination with the styrene type resin synthesized as above or alone.

The polyester resin to be used as the binder can be obtained by the polycondensation of a polyois and a polycarboxylic acids. Examples of the polyols include diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1 ,4-butanediol, neopentyi glycol, 1 ,4-butenediol, and the like; etherified bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A, and the like; and other dihydric alcohol monomers, Examples of the polycarboxylic acids include maleic acid, Dhthalic acid. mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid, anhydrides of these acids, dimers of lower alkyl esters and linolenic acid and monomers of other dicarboxylic organio acids.

The polyester resin to be used in the present invention may be not only a polymer consisting of the abovementioned difunctional monomers alone but also a polymer containing tri- or polyfunctional monomers. Examples of polyhydric alcohols as the polyfunctional monomer include sorbitol, 1,2,3,6 hexanetetrol, 1,4-sorbitan, pentaeythritol, dipentaerythritol, tripentaerythritol, cane sugar, 1,2,4butanetriol, 1 ,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2methyl1 ,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1 ,3,5-trihydroxymethylbenzene, and so forth.

Examples of tri- or polycarboxylic acid monomers include 1 ,2,4-benzenetricarboxylic acid, 1,2,5benzenetricarboxylic acid, 1 ,2,4-cyclohexanetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1 ,2,4-naphthalenetricarboxylic acid, 1 ,2,4-butanetricarboxylic acid, 1 ,2,5-hexanetricarboxylic acid, 1 3dicarboxyl-2-methyl-2-methylenecarboxypropane, tetra(methylenecarboxyl)methane, 1 2,7,8octanetetracarboxylic acid, Empol trimer acid, their acid anhydrides, and so forth.

It is preferred that the abovementioned tri- or polyfunctional monomer component be contained in a proportion of 30 to 80 mol% in each of the alcohol component and acid component as the structural units of the polymer.

The polyester resin to be used in the present invention contains at least 5 wt% of chloroforminsoluble component. The term "chloroform-insoluble component" means a component that does not pass through filter paper when the sample is dissolved in chloroform, and can be determined in the following way.

The sample is finely milled and 5.00 g of the sample powder passing a 40 mesh sieve is collected, and is placed in a container of a 1 50 ml capacity together with 5.00 g of a filter acid, "Radiolite (#700)". 100 g of chloroform is charged into this container and the sample is then sufficiently dissolved in chloroform by placing the container on a ball mill table and rotating it for at least 5 hours. On the other hand, a 7 cm diameter filter paper (No. 2 type) is placed in a pressure filter and 5.00 g of Radiolite is uniformly pre-coated onto the filter. After a small amount of chloroform is added to bring the filter paper into intimate contact with the filter, the contents of the abovementioned container put into the filter.Further, the container is sufficiently washed with 100 ml of chloroform, which is put into the filter so that no component is left attached to the wall of the container. Thereafter, the upper lid of the filter is closed and filtration is carried out. Filtration is conducted at a pressure of up to 4 kg/cm2 and after the chloroform stops flowing out 100 ml more chloroform is added. The residual matter on the filter paper is washed and pressure filtration is again carried out.

After these procedures are completed, the filter paper and the residue and Radiolite on the filter paper are placed on an aluminum foil, which is placed in a vacuum drier and dried at 80 to 1 000C at 100 mmHg for 10 hours. The total weight a (g) of the dry solid thus obtained is measured and the chloroform-insoluble component (wt%) is determined in accordance with the following equation: x (wt%) = [a(g) -- weight of filter paper (g) - weight of Radiolite (10.00 g)] x 100/sampling weight (5.00g) In the polyester resin, the chloroform-insoluble component determined in this manner is a high molecular weight polymer component or a cross-linked polymer component.

The chloroform-insoluble component can be formed to a certain controlled extent by selecting suitable conditions in the polymerization reaction of the aforementioned alcohol and carboxylic acid or by adding a suitable cross-linking agent to the reaction system.

In the present invention, the polyester resin whose chloroform-insoluble content is at least 5 wt% and preferably, 5 to 25 wt%, is used as the binder. If the polyester resin having less than 5 wt% of the chloroform-insoluble component is used, however, aggregation (viscoelasticity) of the resulting toner at the time of fusing would drop so that the toner is likely to adhere to the heating roller. If the chloroforminsoluble component in the polyester resin exceeds 25 wt%, the softening point of the polyester would rise so that milling property and fixability would drop during toner production.

Next, the method of synthesizing the abovementioned polyester resin will be described.

SYNTHESIS EXAMPLE 5 299 g of terephthalic acid, 211 g of polyoxypropyiene (2.2)-2,2-bis(4-hydroxyphenyl)propane and 82 g of pentaerythritol were placed in a round bottom flask equipped with a thermometer, a stainless steel stirrer, a glass tube for introducing nitrogen gas, and a flowdown condenser, and the flask was set to a mantle heater. While nitrogen gas was introduced into the flask through the introduction tube so as to maintain an inert atmosphere inside the flask, the flask was heated, and 0.05 g of dibutyltin oxide was added. The reaction was carried out at 2000C while tracing the reaction at the softening point Thus, a polyester resin A having 1 7 wt% of the chloroform-insoluble component was produced.The softening point of this polyester resin was 1 31 OC by the ball and ring method (in accordance with JIS K 1351-1 960; the same hereinafter).

SYNTHESIS EXAMPLE 6 The reaction was carried out in the same way as in Synthesis Example 5 at 2000C using 828 g of polyoxypropylene (3.3)-2,2-bis(4-hydroxyphenyl)propane, 166 g of terephthalic acid and 127 g of benzene-1 ,2,4-tricarboxylic anhydride, thereby producing a polyester resin containing 12 wt% of the chloroform-insoluble component and having a softening point of 1 250C by the ball and ring method.

COMPARATIVE SYNTHESIS EXAMPLE 3 180 g of 1 4-butanediol, 307 g of terephthalic acid and 38 g of benzene-1 ,2,4-tricarboxylic acid were reacted in the same way as in Synthesis Example 1, thereby producing a polyester resin containing 2 wt% of the chloroform-insoluble component and having a softening point of 1 240C by the ball and ring method.

In the present invention, the styrene type resin having at least 10 wt% of the high molecular weight component having a molecular weight of at least 100,000 and the polyester resin having at least 5 wt% of the chloroform-insoluble component can be used as the binder either alone or as a mixture. When they are used as a mixture, the mixing ratio is arbitrary. since the polyester resin has a higher negative charging property than the styrene type resin, it provides the advantage that when they are used as a mixture it is not necessary to add a charge controlling agent.

In the present invention, it is further possible to add various effective ingredients to the above mentioned binder. For example, at least one of the following agents for providing the mold releasing property can be added.

(a) Olefinic polymer having a low softening point An olefinic polymer or copolymer containing only olefin as the monomer component or an olefinic copolymer containing monomers other than olefin as the monomer component. The low softening point olefinic polymer has a softening point of 80 to 1 800C, preferably 100 to 1 600C, measured by the ball and ring method stipulated in JIS K 2531-1960. The polymer having a higher softening point is not suitable for the present invention because it has low compatibility and dispersibility with the binder resin.

(b) High melting point paraffin wax It is preferred that the wax have as high a compatibility with the binder resin as possible. A paraffin wax having a relatively high melting point, i.e., about 70 to 1 600C, can be effectively used in the present invention.

(c) Fluid paraffin A saturated or unsaturated paraffin which is liquid at normal temperature.

(d) Silicone varnish Examples are methylsilicone varnish, phenylsilicone varnish, and so forth.

(e) Aliphatic fluorocarbon compounds Examples are low polymer compounds such as tetrafluoroethylene, hexafluoropropylene, and so forth.

(f) Fatty acid esters Their partially saponified products, fatty acid esters having a melting point of about 30 to 1 300C and partially saponified products thereof.

(g) Alkylenebis(fatty acid amides) Alkylenebis(fatty acid amides) having a melting point of about 100 to about 180"C.

(h) Higher fatty acids Examples are lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linolic acid, ricinoleic acid, arachidic acid, behenic acid, lignoceric acid, selacholeic acid, and their mixtures.

(i) Metal salts of fatty acids (j) Higher alcohols Either monohydric alcohols or polyhydric alcohols.

(k) Fluorine-containing surfactants Fluorine-containing surfactants such as disclosed in Japanese Patent Laid-Open No.

124428/1980.

These agents for providing the mold releasing property may be used either alone or in combinations of two or more. The amount of these mold releasing agents in the toner is from 1 to 25 wt% and preferably, from 2 to 10 wt%.

The toner composition in accordance with the present invention contains, in the aforementioned binder, a pigment and the abovementioned mold release imparting agent, and if necessary an agent for improving the characteristics. When a magnetic toner is to be produced. a magnetic substance is added together with, or in place of, the pigment.

Examples of the pigment include carbon black, Niglosine dyes (C.l. No. 5041 5B), Aniline Blue (C.I.

No. 50405), Chalcoyl Blue (C.l. No. azoec Blue 3), Chrome Yellow (C.l. No. 14090), Ultramarine Blue (C.l. No. 77103), Du Pont Oil Red (C.l. No. 26105), Quinoline Yellow (C.l. No. 47005), Methylene Blue Chloride (C.I. No.52015), Phthalocyanine Blue (C.l. No. 74160), Malachite Green Oxalate (C.l. No.

42000), Lampblack (C.l. No. 77266), Rose Bengal (C.I. No. 45435), mixtures of them, and others. It is necessary that these pigments be contained in an amount sufficient to form a visible image having a sufficient density. Generally, the proportion is 1 to 20 parts by weight per 100 parts by weight of binder.

Examples of magnetic substances include ferromagnetic metals such as nickel, cobalt, and iron such as ferrite, and magnetite to name a few, their alloys or compounds containing these elements.

Furthermore, alloys which do not contain the ferromagnetic elements but come to exhibit strong magnetism upon heat-treatment can be used. Examples of such alloys include the so-called Whistler alloys containing manganese and copper, such as Mg-Cu-AI and Ma-Cu-Sn alloys, and chromium dioxide can also be used. These magnetic substances are uniformly dispersed in the binder in the form of a fine powder having an average particle diameter of 0.3 to 1 micron. The contents of the magnetic substance are 20 to 70 parts by weight and preferably, 40 to 70 parts by weight, per 100 parts by weight of the toner.

The toner to be used in the present invention is mixed with the binder resin, the pigment, the charge controlling agent, and an agent for improving the characteristics, the latter two being arbitrary agents to be added when necessary, and they are fuse-kneaded, cooled, milled and classified into toner particles having an average particle size of 5 to 30 y. Alternatively, the toner particles can be obtained by the steps of adding the pigment and the polymerization initiator to the monomer for the binder resin, dispersing them in the form of fine powder in a dispersion medium in the presence of a dispersant and polymerizing the mixture to obtain the toner particles.

Hereinafter, the fixing apparatus in accordance with an embodiment of the present invention will be described with reference to the accompanying drawings. It is understood that the invention is not limited thereto.

Figure 1 is a sectional view of the fixing apparatus using a cleaning roller to be used for practising the fixing method of the present invention. Reference numeral 1 represents the heating roller that can rotate in the direction indicated by an arrow; 2 is a hollow iron core; and 3 is a 60 y-thick Teflon coating layer disposed around the outer circumference of the hollow iron core 2. Reference numeral 4 represents a heating source which is equipped with a built-in 800 W halogen lamp, for example.

Reference numeral 5 represents the pressure roller that can rotate in the direction idnciated by an arrow; 6 is a hollow iron core; and 7 is a 4 mm-thick silicone rubber layer disposed around the outer circumference of the hollow iron core 6. The pressure roller 5 has an outer diameter of 40 mm which is the same as that of the heating roller 1. Reference numeral 8 represents the cleaning roller that comes into pressure contact with the heating roller 1 and can rotate in the opposite direction to the heating roller. Reference numeral 10 represents an aluminum core material of the cleaning roller and 11 is a 4.5 mm-thick silicone foam elastic layer covering the outer circumference of the aluminum core material 10.

Reference numeral 1 2 represents a 0.5 mm-thick heat-resistant nylon felt layer ("Nomex", a product of Du Pont) further covering the elastic layer 11. The roller has an outer diameter of 26 mm. The elastic layer 11 and the felt layer 12 are impregnated with 0.3 g/cm3 of "Toray Silicone SH-20" having a viscosity of 100,000 centistokes.

In the fixing apparatus having the above construction, the heating roller 1 and the pressure roller 5 are rotated in the same direction at a high linear speed of 220 mm/sec in pressure contact with each other and press and convey the recording paper 1 4 supporting the toner image 1 3 thereon. The heating roller has a surface temperature of 180 to 200"C and heat-fixes the toner image 13. The cleaning roller 8 rotates at a linear speed of 300 mm/sec in the opposite direction to the heating roller. Its contact surface is heated by the heating roller and the high viscosity mold releasing agent incorporated therein is softened.Upon coming into contact with the heating roller, the cleaning roller coats a thin layer of the mold releasing layer on the surface of the heating roller and cleans the toner stains on the heating roller.

Figure 2 is a sectional view of a fixing apparatus in which a cleaning web 21 is used in place of the cleaning roller 8 used in the fixirig apparatus shown in Figure 1. In the drawing, reference numeral 1 5 represents a push roller for bringing the cleaning web 21 into pressure contact with the heating roller 1.

This roller 15 is formed by covering a 12 mm diameter aluminum core 16 with a 3.5 mm-thick silicone foam layer 1 7 and a 0.5 mm-thick heat-resistant nylon felt layer 1 8. These layers 1 7 and 1 8 are impregnated with 0.3 g/cm3 of "Shinetsu Silicone KF96" (having a viscosity of 2,000 centistokes).

Reference numeral 1 9 represents a 12 mm diameter stock roller on which about 10 m-long cleaning sheet 21 in the initial reproduction width is wound. This cleaning sheet 21 preferably consists of synthetic paper or heat-resistant fiber cloth made of a heat-resistant fiber such as nylon, Tetron, polyimide, polyamide or the like. The cleaning sheet 21 wound on the stock roller 1 9 is extended to a take-up roll 20 via the push roller 1 5.

The abovementioned method of impregnating the push roller 1 8 with the mold releasing agent is merely illustrative and an impregnation member disposed on the stock roller 1 9 may be impregnated with the mold releasing agent. A cleaning sheet 21 impregnated with the mold releasing agent may also be used or a feed roller for supplying the mold releasing agent may be disposed in the cleaning sheet transfer process. In the fixing apparatus having such a construction, the cleaning sheet 21 is transferred at a speed of 0.5 mm/sec in the direction opposite the heating roller 1 and its contact surface is heated by the heating roller 1 so that the high viscosity mold releasing agent contained in the sheet is softened, permeates into the cleaning sheet 21 and is thinly applied to the heating roller 1.At the same time, it collects the toner stains on the heating roller 1 to clean it.

Continuous reproduction tests were carried out at 200C and RH 60% using 9 kinds of developers Nos. 1-9 prepared in the following manner, a "U---Bix V3R" reproducing machine (produced by Konishiroku Photo Industry Co., Ltd.) and the four kinds of fixing apparatuses, i.e., the fixing apparatuses shown in Figures 1 and 2, the fixing apparatus of Figure 1 in which the cleaning roller is not impregnated with the high viscosity mold releasing agent and the fixing apparatus of Figure 2 in which the cleaning web is not impregnated with the mold releasing agent.

In the tests, the number of times of reproduction which provides the fixed image having high quality and free of stains was examined, and the results are shown in Table 1.

[Preparation of Developers] The nine kinds of resins obtained in Synthesis Examples 1 through 6 and Comparative Synthesis Examples 1 through 3 were used as the binders, respectively. Samples Nos. 1, 3, and 4 toners for developer are prepared in accordance with the following recipe (a), Samples Nos. 2, 5 and 6 toners for developer, in accordance with recipe (b), Sample No. 7 toner in accordance with recipe (c), and Samples Nos. 8 and 9 toners for developer, in accordance with recipe (d).

Recipe (a) binder resin 100 parts carbon black 8 parts negative charge controller 3 parts ("Varifast 3804", produced by Orient Kagaku Kogyo Co.) Recipe (b) binder resin 100 parts carbon black 8 parts negative charge controller 3 parts ("Varifast 3804") low softening point polypropylene ("Viscol 550P", produced by Sanyo Chemical Industry Co., Ltd.) 5 parts Recipe (c) binder resin 100 parts carbon black 8 parts Recipe (d) binder resin 100 parts carbon black 8 parts low softening point polypropylene, "Viscol 550P" 5 parts 100 parts of an iron powder carrier (produced by Nippon Teppun Co.) was added to 5 parts of each of the resulting nine kinds of toners to obtain nine kinds of developers.

TABLE 1 Kind of toner binder Number of resin (Synthesis times of Sample No. Example No.) Cleaning method reproduction This Invention 1 Synthesis Example 1 Cleaning roller 85,000 containing mold releasing agent " 2 2 " 100,000 Comparison 3 Comp. Synthesis " 20,000 Example 1 This Invention 4 Synthesis Example 3 ,, 80,000 Comparison 5 " 4 Cleaning roller 12,000 not containing mold releasing agent " 6 Comp. Synthesis Cleaning roller 35,000 Example 2 containing mold releasing agent This Invention 7 Synthesis Example 5 Cleaning web 50,000 containing mold releasing agent Comparison 8 ,, 6 Cleaning web not 10,000 containing mold releasing agent 9 Comp.Synthesis Cleaning web 30,000 Example 3 containing mold releasing agent In the abovementioned reproduction tests, Sample No. 7 finished with 50,000 reproductions when the fixing apparatus used web cleaning. This was because the amount of the mold releasing agent contained is smaller than the cleaning roller since the push roller is small, and because the viscosity of the mold releasing agent is low. Accordingly, the number of reproductions can of course be increased if the capacity of the push roller is increased.

From Table 1, it can be understood that a greater number of high quality fixed images can be obtained in accordance with the fixing method of the present invention than with the.comparative fixing methods.

The fixing apparatus having the abovementioned construction was fitted to a reproducing machine, "U-Bix V3R" (produced by Konishiroku Photo Industry Co., Ltd.) and the heating roller 1 and the pressure roller 5 were rotated in the same direction at a linear speed of 220 mm/sec while kept in pressure contact with each other so as to convey the recording paper 1 4 supporting the toner image 1 3 thereon and to heat-fix the toner image at 1 80 to 2000C. The cleaning roller 8 was rotated in the opposite direction at a linear speed of 300 mm/sec while kept in contact with the outer circumference of the heating roller 1, thereby cleaning it. In this manner, reproduction was continuously effected 100,000 times but the toner image on the recording paper was reproduced providing a high quality fixed image without any stains.

On the other hand, the reproduction operation was carried out with the same copying machine, "U-Bix V3R" using the same fixing apparatus as that of the present invention except that the mold release agent was not used. Stains started to appear after about 10,000 times and stains that prohibited reproduction were observed on the reproduced picture after around 20,000 times.

It can be appreciated from the results of the aforementioned embodiments that the fixing apparatus of the present invention makes it possible to stably carry out the reproducing operation by disposing an extremely simple cleaning roller without calling for a feeder for the mold releasing agent.

Claims (23)

1. In a heating roller fixing method in which recording paper bearing a toner image thereon is conveyed by a heating roller and a pressure roller in pressure contact with said heating roller to heat-fix said toner image, the improvement wherein a cleaning member having a fiber material containing a high viscosity mold releasing agent on the surface thereof is brought into pressure contact with said heating roller.

2. The fixing method as defined in claim 1 wherein said mold releasing agent has a viscosity of 1,500 to 300,000 centistokes at 250C.

3. The fixing method as defined in claim 2 wherein said mold releasing agent has a viscosity of 2,000 to 60,000 centistokes at 250C.

4. The fixing method as defined in claim 1 or 2 wherein said mold releasing agent is a silicone oil.

5. The fixing method as defined in claim 1 wherein said cleaning member is a cleaning roller.

6. The fixing method as defined in claim 5 wherein said cleaning roller is rotating.

7. The fixing method as defined in claim 6 wherein the direction of rotation of said cleaning roller is opposite to that of said heating roller.

8. The fixing method as defined in claim 5, 6 or 7 wherein said cleaning roller consists of a core material, a flexible material layer containing said mold releasing agent and covering the outer circumferential surface of said core material and a fiber material covering said flexible material layer.

9. The fixing method as defined in claim 6 wherein said flexible material is impregnated with said mold releasing agent.

10. The fixing method as defined in claim 1 wherein said toner image is formed by a toner comprising a resin selected from the group consisting of a homopolymer of a styrenes containing at least 10 wt% of a high molecular weight component having a molecular weight of at least 100,000, a copolymer of a styrenes containing at least 10 wt% of a high molecular weight component having a molecular weight of at least 100,000, and a polyester resin containing at least 5 wt% of a chloroforminsoluble component.

11. The fixing method as defined in claim 10 wherein said homopolymer of a styrenes is a polystyrene.

12. The fixing method as defined in claim 10 wherein said copolymer of styrenes is a copolymer of styrenes and butadiene.

13. The fixing method as defined in claim 12 wherein said copolymer of styrenes and butadiene is a copolymer of styrene and butadiene.

1 4. The fixing method as defined in claim 10 wherein said styrene type resin is a copolymer of styrene and s1-methylene aliphatic monocarboxylic acid esters.

1 5. The fixing method as defined in claim 14 wherein said e-methylene aliphatic monocarboxylic acid esters is an acrylates or a methacrylates.

1 6. The fixing method as defined in claim 10 wherein said chloroform-insoluble component of said polyester type resin is from 5 to 25 wt%.

1 7. The fixing method as defined in claim 1 wherein said toner further comprises a polyolefin having a softening point of 80 to 1 600 C.

1 8. The fixing method as defined in claim 1 wherein said fiber material is a cleaning web.

1 9. The fixing method as defined in claim 1 8 wherein said mold releasing agent is contained in a stock roller of said cleaning web and said mold releasing agent is supplied to said cleaning web when said cleaning web wound on a stock roller is fed out from said stock roller.

20. In a fixing apparatus including a heating roller for pressing and conveying recording paper supporting a toner image thereon in cooperation with a pressure roller and for heat-fixing said toner image. the improvement wherein a cleaning member having a fiber material containing a high viscosity mold releasing agent on the cleaning surface thereof is adapted to come into pressure contact with said heating roller.

21. The fixing apparatus as defined in claim 20 wherein said mold releasing agent has a viscosity of 1,500 to 300,000 centistokes at 250C.

22. The fixing apparatus as defined in claim 20 or 21 wherein said fiber material is a cleaning web spread between a stock roller and a take-up roller and brought into pressure contact with said heating roller by a push roller.

23. Method of fixing toner image and apparatus therefor, substantially as hereinbefore described with reference to the accompanying drawings.