JPH04184356A - Thermal fixing method - Google Patents

Abstract

PURPOSE:To efficiently perform excellent thermal fixing without causing an offset phenomenon by containing thermoplastic silicone resin whose glass transition point is a value in a specified range in toner for developing electrostatic charge image. CONSTITUTION:At least, binding resin, coloring material and the thermoplastic silicone resin whose glass transition point measured by a differential thermal analysis device, that is, Tg is 40-90 deg.C are contained in the toner. Tg of the silicone resin is controlled based on the kind and the number of the organic group of the silicone resin. When Tg is <40 deg.C, the compatibility of the toner with the binding resin is increased and a pressure member is easily contaminated. When Tg is >=90 deg.C, the dispersion of the toner and the binding resin is insufficient and offset resistance becomes poor. Crosslinked styrene copolymer or crosslinked polyester is desirable as the binding resin substance. Then, an endless film is used as the fixing film 5 of a fixing device, and silicone rubber is used as a pressure roller 8. A heating body 1 is a linear heating body of low heat capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for thermally fixing toner for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, and the like.

[Prior Art] Conventionally, as an electrophotographic method, US Pat.
A number of methods are known, such as those described in Japanese Patent Publication No. 43-24748, etc., but in general, a photoconductive container is used to form an electrical latent image on a photoreceptor by various means. Then, the latent image is developed using toner, which is a developer, and if necessary, the toner image is transferred to a transfer material such as paper, and then fixed by heat, pressure, heat pressure, solvent vapor, etc. Then, the toner remaining on the photoreceptor without being transferred is cleaned by various methods, and the above-described steps are repeated.

In recent years, such copying machines have begun to be used not only as office copy machines for copying original documents, but also for copying high-definition images such as digital printers or graphic designs as output from computers. Ta.

For this reason, higher reliability is being strictly pursued, and as a result, the required performance has become more advanced, and unless the performance of image forming methods, including toner, can be improved, better machines will not be possible. It's coming.

By the way, the most important performance required of toner in digital printers and copying of high-definition images is the ability to fix fine lines.

Regarding the fixing process, various methods and devices have been developed, but the most common method at present is a compression heating method using a heated roller.

The pressure heating method using a heated roller performs fixing by passing the toner image surface of the sheet to be fixed under pressure while contacting the surface of a heated roller whose surface is made of a material that has releasability for toner. . In this method, the surface of the heat roller and the toner image on the sheet to be fixed come into contact with each other under pressure, so the thermal efficiency when fusing the toner image onto the sheet to be fixed is extremely good, and the fixing can be performed quickly. It is very effective in high-speed electrophotographic copying machines. However, in the above method, since the heated roller surface and the toner image contact each other under pressure in a molten state, a part of the toner image adheres to the fixing roller surface, is tumbled, and is transferred again to the next sheet to be fixed. A so-called offset phenomenon may occur, and the sheet to be fixed may be stained. Preventing toner from adhering to the surface of the heat fixing roller is considered to be one of the essential conditions for the heat roller fixed fixing method.

In addition, recently, instead of a heat roller, a fixing device consisting of a pressure member that is in opposing pressure contact with a heating body and brings the recording material into close contact with the heating body through a film has been put into practical use, and has become advantageous in terms of thermal efficiency. However, since the toner surface is melted, the offset phenomenon is more likely to occur, making it even more necessary to prevent this phenomenon.

On the other hand, in the latent image portion of a minute image, lines of electric force are concentrated at the boundary between the exposed and non-exposed areas, and the surface potential of one photoreceptor appears to increase. In particular, in digital printers, the latent image is composed of binary basic pixels of 0N-OFF, so the electric lines of force are concentrated at the boundary between exposed and non-exposed areas, and the basic pixels are The amount of toner per unit area developed into the structured line latent image is greater than the amount of toner on a typical analog image.

Therefore, in fixing such images, there is a current demand for toners with better fixing properties and offset properties than ever before.

Further, when used as a printer, the amount of copies to be made is 3 to 5 times that of a copying machine of the same level, and at the same time, high durability of development and high image stability are also required.

On the other hand, as a technique for improving the binder resin of a toner, for example, Japanese Patent Publication No. 51-23354 proposes a toner using a crosslinked polymer as a binder resin. If this method is followed, it will be effective in improving offset resistance and clinging resistance, but on the other hand, if the degree of crosslinking is increased, the fixing point will rise, and the fixing temperature will be sufficiently low, resulting in good offset resistance and clinging resistance. However, in order to improve the fixation properties for boat fishing, it is necessary to
The binder resin must be lowered in molecular weight to lower its softening point, which is contradictory to measures to improve anti-offset properties, and lowering the softening point inevitably lowers the glass transition point of the resin, making storage difficult. The undesirable phenomenon of blocking of the toner inside also occurs.

Furthermore, JP-A-63-223662 discloses that offset resistance can be achieved by using a binder resin containing 10 to 60 parts by weight of THF-insoluble matter and having two peaks in molecular weight distribution. It was still insufficient to satisfy all of the low-temperature fixing properties, anti-blocking properties, and anti-offset properties from high-speed machines to low-speed machines.

Conventionally, in order to prevent toner from adhering to the surface of the fixing roller, for example, the roller surface is made of a material that has excellent release properties against toner, such as fluorine-based resin, and the surface is coated with an anti-offset material such as silicone oil. It is practiced to supply a liquid to coat the roller surface with a thin film of liquid. Although this method is extremely effective in preventing toner offset, it generates an odor due to heating of the offset prevention liquid and requires a device to supply the offset prevention liquid. This method has disadvantages in that the mechanism of the copying device becomes complicated and high precision is required to obtain stable results, making the copying device expensive.

Special Publication No. 5B-58664, Special Publication No. 57-5257
Publication No. 4, etc., discloses a method of constant adhesion of toner or heating roller using low molecular weight polyalkylene that is effective in preventing toner adhesion to the heating roller due to offset, but as a result of studies by the present inventors. This method cannot prevent the fuser lower roller (hereinafter referred to as the pressure roller) from becoming dirty.
In addition, the heating roller fixing device has a small diameter of 40 cm or less and/or the heating roller fixing device has a slow line speed of 150 m.
If it is less than m/sec, the effect is small and it is still necessary to supply offset prevention liquid.

[The problem that the invention tries to solve! ! ! ] An object of the present invention is to prevent the offset phenomenon even when no offset prevention liquid is supplied to the surface of the heating member of the fixing device, and also in a small electrophotographic device having a thermal fixing device with a slow linear speed using a fixing roller with a small diameter. An object of the present invention is to provide a heat fixing method that can efficiently perform good heat fixing without causing any problems.

[Means and effects for solving the problems] The present invention provides a heat fixing method in which a heating member is brought into contact with a support having a toner image and the toner image is thermally melted and fixed to the support. The toner contains at least a binder resin, a colorant, and a glass transition temperature (as measured by a differential thermal analyzer).
This heat fixing method is characterized in that it is a toner for developing an electrostatic image containing a thermoplastic silicone resin having a Tg) of 40 to 90°C.

When using the fixing method of the present invention, an anti-offset liquid is not supplied to the contact surface of the heating member to the latent image support, and/or a device for cleaning the contact surface of the heating member to the latent image support is provided. Even if it is not used, an offset phenomenon will not occur (and the pressure member will not be contaminated).

Furthermore, the same effect can be achieved in small-sized fixing devices and low-speed fixing devices with a slow linear speed, and has the advantage that, for example, the design of small-sized copying machines and laser beam printers can be made extremely easy.

The glass transition point (Tg) of the thermoplastic silicone resin contained in the toner constituting the toner image in the present invention is 4.
It is necessary that the temperature is 0 to 90°C. Tg can be controlled by the type and number of organic groups that the silicone resin has, but silicone resins that contain at least one type selected from phenyl groups and modified phenyl groups, and at least one type selected from alkyl groups, modified alkyl groups, aryl groups, and modified aryl groups. It is preferable that you do so.

When Tg is less than 40° C., the compatibility of the toner with the binder resin increases and the pressure member is likely to be contaminated. Further, if the Tg is 90° C. or higher, the toner is insufficiently dispersed with the binder resin, resulting in poor offset resistance.

Further, the softening point of the silicone resin according to the present invention as determined by microscopic observation on a hot plate is preferably 70° C. to 150° C. from the viewpoint of offset prevention effect and pressure member contamination prevention effect. That is, the silicone resin according to the present invention has a low T
g. Preferably, it has a low softening point so that it melts during heat fixing and behaves like an anti-offset oil, thereby facilitating heat fixing without causing any harmful effects to others.

Examples of the binder resin used in the toner of the present invention include monopolymers of styrene and its substituted products such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymers, and styrene-p-chlorostyrene copolymers; -vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer,
Styrene-methacrylic acid ester copolymer, styrene-
α-Methyl chlormethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinylethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer Styrenic copolymers such as , styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenolic resin, naturally modified phenolic resin, natural resin-modified maleic acid resin, acrylic resin, methacrylic resin, poly Examples include vinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumaron indene resin, and petroleum resin.

Preferred binding materials include crosslinked styrenic copolymers or crosslinked polyesters.

Examples of comonomers for the styrene monomer of the styrenic copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, and methacrylate. Acid, monocarboxylic acid having a double bond such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, etc., or substitutes thereof; e.g., maleic acid, butyl maleate , methyl maleate, dimethyl maleate, etc., and their substituted substances; vinyl esters, such as vinyl chloride, vinyl acetate, vinyl benzoate, etc.; e.g., ethylene, propylene, butylene, etc. Vinyl monomers such as ethylene olefins; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether; Two or more are used.

As the crosslinking agent, compounds having two or more polymerizable double bonds are mainly used, such as aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate,
Carboxylic acid esters having two double bonds such as ethylene glycol dimethacrylate and 1,3-butanediol dimethacrylate; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide, and divinyl sulfone; and three or more vinyl Compounds having groups can be used alone or as a mixture.

As the coloring agent, conventionally known dyes and pigments can be used, and usually 0.00 parts by weight per 100 parts by weight of the binder resin.
5 to 20 parts by weight may be used.

Furthermore, in order to control the amount of charge in the toner of the present invention, it is preferable to use a charge control agent blended with the toner particles (internally added) or mixed with the toner particles (externally added). The charge control agent makes it possible to optimally control the amount of charge depending on the developing system, and in particular, in the present invention, it is possible to further stabilize the balance between particle size distribution and charge.

Known negative charge control agents can be used in the present invention, such as carboxylic acid derivatives, metal salts thereof, alkoxylates, organic gold Rtfi forms, chelate compounds, etc. alone or in combination of two or more. . Among these, acetylacetone gold Rm form, salicylic acid metal complex, naphthoic acid metal complex, and monoazo metal complex are particularly preferably used.

The charge control agent described above is preferably used in the form of fine particles. In this case, the number average particle size of this charge control agent is
Specifically, the thickness is preferably 4 μm or less (more preferably 3 μm or less).

When internally added to the toner, such a charge control agent is added in an amount of 0.1 to 20 parts by weight (or even 0.1 to 20 parts by weight) per 100 parts by weight of the binder resin.
．． 2 to 10 parts by weight) is preferably used.

Various additives may be added internally or externally to the toner according to the present invention, if necessary. Examples include lubricants such as zinc stearate; abrasives such as cerium oxide and silicon carbide; and conductivity imparting agents such as carbon black and tin oxide.

In addition, for the purpose of improving mold releasability during heat fixing, low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, Sasol wax,
It is also a preferred embodiment of the present invention to add a waxy substance such as paraffin wax to the magnetic toner in an amount of about 0.5 to 5 wt % based on the binder resin.

Further, the toner according to the present invention may also serve as a colorant, and may also contain a magnetic material. Magnetic materials contained in the magnetic toner of the present invention include magnetite, γ-
Iron oxides such as iron oxide, ferrite, iron-rich ferrite;
Metals such as iron, cobalt, nickel, or these metals and aluminum, cobalt, copper, lead, magnesium,
Examples include alloys with metals such as tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, and vanadium, and mixtures thereof.

These ferromagnetic materials have an average particle size of 0.1 to 1 μm, preferably 0.1 to 0.5 μm, more preferably 0.1 to 0.3 μm.
It is desirable that the magnetic toner has a particle size of approximately μm, and the amount to be contained in the magnetic toner is 50 to 200 parts by weight per 100 parts by weight of the resin component, preferably 60 to 1 part by weight per 100 parts by weight of the resin component.
It is 50 parts by weight.

To prepare the toner for developing electrostatic images according to the present invention, magnetic powder, vinyl-based or non-vinyl-based thermoplastic resin, pigment or dye as a coloring agent, charge control agent, other additives, etc. are used as necessary. are thoroughly mixed using a mixer such as a ball mill, and then melted, kneaded, or kneaded using a heat kneader such as a heated roll, kneader, or extruder to make the resins compatible with each other. The toner according to the present invention can be obtained by dispersing or dissolving the toner, cooling and solidifying, and then pulverizing and strictly classifying.

Further, the toner according to the present invention may be mixed with externally added fine oxide powder (the following oxides are preferably used as these oxides).

5ift, Als Os, Tilt, GeO*
.

These include B, O, P, O, and composite compounds thereof, and these may be used alone or in combination.

In addition, the oxide fine powder used in the present invention may optionally contain silicone oil, silicone oil, organosilicon compounds, or these substances having functional groups for purposes such as silane coupling agents, hydrophobization, and charge stabilization. The silica powder may be treated with a treatment agent that reacts with or physically adsorbs the silica fine powder.

A specific example of a device that can be used to carry out the thermal fixing method of the present invention is a heating roller fixing device! There is. The fixing roller may have a smooth surface made of fluorine-based resin such as polytetrafluoroethylene (PTFE) or perfluoroacrylate (PFA) or relatively hard silicone rubber, or may have a metal surface in some cases. What we have is put to good use.

Also, without using a fixing roller, a heating element and polyimide, pps
A device for melting and fixing the toner surface with a heat-resistant resin film such as (FIG. 1) is also preferably used in the present invention. It is preferable that the surface of this film is also coated with a fluorine-based resin such as PTFE or PFA.

Although silicone rubber, fluororubber, etc. are usually used for the pressure brazing material, it is also one of the preferred embodiments of the present invention that the material is coated with a fluorine-based resin.

The linear velocity and surface temperature during fixing are not particularly limited, but are 5 mm/sec to 100 mm/sec, 100 mm/sec, respectively.
It is preferable to set it as ℃~200℃.

[Examples] The present invention will be specifically explained below using Examples, but these are not intended to limit the present invention in any way.

Note that all parts in the following formulations are parts by weight.

Example 1 The above materials were thoroughly mixed in a blender and then kneaded in a twin-screw kneading extruder set at 130°C. After cooling the obtained mixed material and coarsely pulverizing it to 1 mm or less with a cutter mill,
6kg/cm” using a pulverizer using a jet stream
The resulting finely pulverized powder was classified using a fixed wall air classifier to produce classified powder. Furthermore, the obtained classified powder is simultaneously classified and removed to remove ultrafine powder and coarse powder using a multi-division classifier that utilizes the Coanda effect (Elbowjet classifier manufactured by 5 Iron Mining Co., Ltd.) to create a magnetic toner with a weight average particle size of 6.6 μm. I got an A.

0.6 parts of colloidal silica was externally added to 100 parts of this magnetic toner A, and an electrostatic image formed by electrophotography using laser light was developed by a reversal development method, and then the toner image was transferred onto transfer paper, and the surface 1 using a fixing roller covered with a PFA (perfluoroacrylate) film.
The toner image was melted and fixed by pressure contact at a temperature of 80° C. and a line speed of 50 mm/see. Silicone rubber was used for the pressure roller. Next, in order to investigate whether the fused toner image is transferred to the surface of the fixing roller and an offset phenomenon occurs, after performing each fixing operation, the transfer paper without toner image was pressed against the fixing roller under the same conditions as above. The transfer paper was brought into contact with the transfer paper, and stains caused by toner offset were observed.

Furthermore, 10,000 sheets of transfer paper bearing a toner image were continuously passed through the fixing roller, and stains on the surface of the pressure roller were observed.

As a result, no stains were generated on the transfer paper, and the
Even after 00 repetitions, no staining occurred on the pressure roller.

Example 2 The same procedure as in Example 1 was carried out except that 7 g of silicone resin (2) at 80° C. was used. As a result, no offset phenomenon or staining of the pressure roller occurred at all.

Example 3 The same procedure as in Example 1 was performed except that a metal roller whose surface was treated with hard chrome was used as the fixing roller and the surface temperature was set at 150° C. As a result, neither offset phenomenon nor pressure roller stain occurred at all. .

Example 4 A toner was prepared in the same manner as in Example 1 using the above materials.

Using this toner, an external fixing device as shown in FIG. 1 was used as the fixing device, which consisted of a pressure member that was in opposing pressure contact with the heating body and brought the recording material into close contact with the heating body through a film. . As the material of the fixing film 5, an endless film based on a polyimide film coated with a release layer of 10 μm in which a conductive material was added to a fluororesin was used. Silicone rubber was used as the pressure roller 8, and the nip width was 3.5 mm and the linear speed was 60 mm/sec. The film is driven by the drive roller 6 and the driven roller 7, and by the tension, moves in the direction of the arrow without wrinkles. Further, the heating element 1 is a linear heating element with a low heat capacity, and obtains pulsed energy to regulate the temperature.

Except for the above, evaluation was performed in the same manner as in Example 1, and no offset phenomenon or staining of the pressure roller occurred at all.

Comparative Examples 1 and 2.3 Example 1.3 except that silicone resin ■ was not used. As a result of carrying out the same procedures as in 4 and 4, a significant offset phenomenon occurred and the pressure roller was also noticeably stained.

Comparative Example 4 The same procedure as in Example 1 was carried out except that silicone resin DI (Tg=30°C) was used. As a result, stains were noticeable on the pressure roller.

Comparative Example 5 The same procedure as in Example 1 was carried out except that silicone resin IV (Tg=100° C.) was used. As a result, a significant offset phenomenon occurred and the pressure roller was also noticeably stained.

[Effects of the Invention] As described above, according to the heat fixing method of the present invention, a high-quality image can be obtained without causing an offset phenomenon. Further, even without the offset prevention liquid, the offset phenomenon does not occur, the fixing device can be made smaller, and the pressure roller is less likely to get dirty, so the life of the fixing device can be significantly extended.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a fixing device used in an embodiment of the present invention. l... Heating body 2... Alumina substrate 3.
... Resistance material 4 ... Temperature measuring element 5 ... Fixing film 6 ... Drive roller 7 ... Followed roller 8 ... Pressure roller 9 ... Recording material
10...Unfixed toner 11...Entrance guide Figure 1

Claims (1)

[Claims] A heat fixing method in which a heating member is brought into contact with a support having a toner image and the toner image is thermally melted and fixed to the support,
The toner constituting the toner image contains at least a binder resin,
A heat fixing method characterized in that the toner is a toner for developing an electrostatic image containing a colorant and a thermoplastic silicone resin having a glass transition point (Tg) of 40 to 90° C. as measured by a differential thermal analyzer.