JPH04337744A - Electrophotographic image fixing method and electrophotographic device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image fixing method and an electrophotographic apparatus using the fixing method.

0002

[Prior Art] Conventionally, when fixing a toner image on a support in electrophotography, a hot pressure roll, for example, a roll coated with a resin with good release properties such as silicone elastomer or fluorine resin, has been used. .

On the other hand, a resin is blended into the toner as a binder to a transfer support such as paper. As the binder resin, resins obtained by polymerizing α,β-unsaturated ethylenic monomers, partially crosslinked resins, polyester resins, epoxy resins, etc. have been proposed (Japanese Patent Publication No. 55-6895, Japanese Patent Application Laid-Open No. 50-44).
No. 836, Japanese Patent Publication No. 12860/1983, Japanese Patent Application Publication No. 1973/1983
47325).

0004

[Problems to be Solved by the Invention] When forming an image using these conventional fixing methods and toner, if the fixing temperature is low, the toner will not be sufficiently melted, and the image surface will not be smooth and not sufficiently smooth. It is not possible to obtain a high level of gloss. Further, when the fixing temperature is high, the internal cohesive force of the toner is weak, hot offset occurs, and a good image cannot be obtained.

[0005] Furthermore, when an envelope, cardboard, etc. is used as a support,
There is a problem in that wrinkles and warpage occur due to pressure and heating during fixing.

[0006] A proposal was made regarding the relationship between the storage modulus, loss modulus, and loss tangent of toner or binder resin of toner, toner fixability, and image quality (Japanese Patent Laid-Open No. 63-25
No. 9575, JP-A-63-296065, JP-A-63
-300254, Japanese Patent Application Laid-Open No. 1-204066), these methods prevent the support from wrinkling and warping.
At the same time, it was not possible to obtain an image with high gloss.

An object of the present invention is to prevent the occurrence of wrinkles and warpage during fixing of supports such as envelopes and cardboard in electrophotography;
Another object of the present invention is to provide an image fixing method and an electrophotographic apparatus for obtaining a highly glossy image.

[0008]

[Means for Solving the Problems] The gist of the present invention for achieving the above object is as follows.

(1) An electrophotographic image fixing method in which a heating part is fixed by contact pressure on the toner adhering surface of a support, in which the value of loss tangent tan δ at the toner heating temperature is in the range of 5 to 50. An image fixing method for electrophotography, characterized in that the contact pressure between the heating section and the toner adhesion surface is lower than the pressure that does not deform the toner support.

(2) An electrophotographic image fixing method, characterized in that fixing is carried out at a contact pressure between the heating section and the toner adhesion surface of 0.3 to 1 kg/cm2.

(3) a photoreceptor made of a photoconductor; a charging means for charging the photoreceptor; a latent image forming means for forming an electrostatic latent image on the surface of the charged photoreceptor; In an electrophotographic apparatus, the toner is Loss tangent t at heating temperature during fixing
An electrophotographic apparatus characterized in that the value of and δ is 5 to 50, and the contact pressure between the heating section of the fixing means and the support to which the toner image is transferred is 0.3 to 1 kg/cm2. .

The present inventors have investigated and found that when an envelope, cardboard, etc. is used as a support for a toner image, the wrinkles of the support itself,
To prevent the occurrence of warping, the contact pressure of the toner adhesion surface of the heating section during fixing, for example, the heating roll, should be much lower than the contact pressure in conventional image fixing methods, for example 0.3~
It has been found that this can be achieved by setting the weight to 1 kg/cm2. Note that it is not preferable that the fixing pressure is lower than 0.3 kg/cm2 because the fixing force of the toner becomes weak.

[0013] The present inventors have studied the mechanism by which images with high gloss can be obtained by the fixing method of the present invention, and have come up with the following idea. That is, the support on which the unfixed toner image has been formed comes into contact with a heating roll, and the binder resin in the toner changes from solid to glass to rubber state due to the heat, exhibiting behavior as a viscoelastic body, and at the same time the heating member Plastic deformation begins due to pressure. Then, when the pressure of the heating member is released, stress acts on the toner to restore it to its original state. Toner that is close to an elastic body has a strong stress to recover to its original state, resulting in a roughened surface, while toner that is close to a viscous body has a weak stress, resulting in a smooth surface. Also,
Among the viscoelastic properties, the loss tangent tanδ is the spring property (
The storage modulus G′ showing the elasticity) and the dashpot property (
It is generally considered that the larger tan δ is, the closer it is to a viscous body, and the smaller it is, the closer it is to an elastic body.

[0014] Therefore, it is considered that the larger the tan δ, the smoother the image surface and the better the glossiness. However, if tan δ is too large, the internal cohesive force of the molten toner will be weakened, hot offset will occur, the image surface will become rough, and the glossiness will decrease. Cold offset occurs when the adhesive force between the toner and the heating roll is greater. From this, in the fixing method that presses the heating member,
It has been found that by setting the value of the loss tangent tan δ of the toner at the heating temperature within an appropriate range, it is possible to enhance the glossiness of the image and prevent hot offset.

According to studies by the present inventors, if the value of the loss tangent tan δ of the toner is 5 to 50 at the heating temperature, hot offset does not occur and an image with high gloss can be obtained.

The loss tangent tan δ was measured using a rheometer (Rheopexy Analyzer Model RPX-705, manufactured by Iwamoto Seisakusho) for measuring such rheological properties. The measurement conditions were a frequency of 0.1 Hz and a strain angle of 3 degrees, and the temperature dependence characteristics were measured using a cone plate with a radius of 15 mm and an apex angle of 87 degrees.

The type of toner binder used in the present invention is not particularly limited as long as it is a toner resin commonly used in electrophotography. However, since the viscoelastic properties of the binder strongly affect the viscoelastic properties of the toner, the binder should be selected in consideration of its own viscoelasticity.

The binder may be, for example, a monopolymer of styrene or its substituted product such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, a styrene-p-chlorostyrene copolymer, a styrene-propylene copolymer,
Styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer Polymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-methyl chloromethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer Coalescence, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-
Styrenic copolymers such as indene copolymers, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, silicone resins, polyester resins, polyurethane resins, polyamide resins, epoxy resins, polyvinyl butyral, rosin modified resins, terpene resins, phenol resin, xylene resin, aliphatic or alicyclic hydrocarbon resin,
One or more of aromatic petroleum resins, chlorinated paraffins, and paraffin waxes are used.

Furthermore, as mentioned above, when an envelope, cardboard (thickness of a postcard or more), etc. is used as a toner support, the fixing pressure should be 0.3 to 0.3 to prevent wrinkles and warping of the support.
It is important to set the weight to 1 kg/cm2. Therefore, as a binder, a polyester resin having a low melting point and good wettability to paper etc. is particularly preferable.

Note that since the viscoelastic properties of the binder affect the viscoelastic properties of the toner, the loss tangent ta of the resin itself
It is also preferable to select a value of nδ of 5 to 50.

[0021] In order to prevent hot offset, it is preferable that the toner has elasticity even at high temperatures. For this purpose, the binder resin preferably contains 1 to 50% by weight of a crosslinking component.

The colorant of the toner of the present invention includes carbon black, nigrosine dye, benzidine yellow (for example, C
．． I. pigment yellow-12), nitrophenylamine sulfonamide (e.g. Color Index:
Disperse Yellow 33), monoazo dye (C.I.
: Solvent Yellow 16), Quinacridone (C.I.
: Pigment Red 122), anthraquinone dye, diazo dye (e.g. C.I.: Solvent Red 19),
Known dyes and pigments such as copper phthalocyanine (for example, C.I.: Pigment Blue 15) and indanthrene blue can be used. In this case, it is important to blend the toner so that the value of the loss tangent tan δ is within the range of 5 to 50.

The toner of the present invention can be used as a two-component developer mixed with a known carrier, or as a single-component developer. As the carrier for the two-component developer, for example, iron powder, magnetic powder such as ferrite, glass beads, and those whose surfaces are treated with resin are used.

[0024] The fixing device in the present invention can be a pressure-heating fixing device, and preferably has a surface coated with a fluororesin in order to improve the toner releasability. For example, there are heating rolls that have a 10-100 μm thick polytetrafluoroethylene resin layer on the outer circumferential surface of a metal roll made of aluminum, stainless steel, iron, copper, etc., and silicone rubber, fluorine rubber, etc. on the outer circumferential surface of a metal roll. , a pressure roll with a relatively thick layer of elastic material such as fluorosilicone rubber is stacked on top of the other, and a support such as paper on which a toner image has been formed is passed between the rolls to fix the toner image under pressure and heat. .

[0025] The heating method for the roll can be carried out by a known heating means that controls the temperature by providing a hollow part in the roll and arranging a sheathed heater and a temperature sensor therein. Further, if necessary, the pressure roll may be heated by providing a similar heating means.

Furthermore, in order to improve the releasing properties of the heating section of the fixing device, it is also effective to apply a releasing agent such as silicone oil to the toner contact surface.

The fixing device of the present invention is not limited to one using rolls. For example, the heating may be carried out using two plate-shaped fixing plates that can be pressurized and provided with heating means.

[0028]

[Function] In the electrophotographic image fixing method of the present invention, a highly glossy image can be obtained if the toner has a loss tangent tan δ value of 5 to 50 at the heating temperature. This is because by selecting such a material, the toner melts sufficiently during fixing, and the internal cohesive force of the toner layer is greater than the adhesive force between the heating member and the toner.

[0029]

EXAMPLES The present invention will be explained by examples. The amounts of each component described in the examples are all parts by weight.

<Example 1> Toner composition Resin: Polyester resin (softening point: 117.4)
………………………100 parts Colorant: Carbon black …………………………………
...10 parts of this were heated and kneaded in a roll mill, and after cooling,
The powder was coarsely pulverized with a cutting mill, further finely pulverized with a supersonic jet mill, and then classified with a zigzag classifier to obtain a toner having an average particle size of 11 μm.

Three parts of this toner and 100 parts of a ferrite carrier (F-150 manufactured by Nippon Tetsu Powder Co., Ltd., average particle size 80 μm) were mixed to obtain a developer.

A laser beam printer (SL-100, manufactured by Hitachi) was used to output an unfixed image using this developer. Parts of this printer are shown in FIG.

A fixing device having the following specifications and equipped with a heating roll and a pressure roll was used to fix the unfixed image.

[0034] A heating roll (diameter 32 mm) coated with tetrafluoroethylene resin to a thickness of about 10 μm on the outer circumferential surface of an aluminum hollow cylinder, and silicone rubber coated to a thickness of about 13 mm on the outer circumferential surface of the aluminum hollow cylinder. The formed pressure roll (
The heating roll had a diameter of 40 mm, and was configured so that silicone oil as a mold release aid could be thinly applied to the surface of the heating roll. The fixing conditions of the fixing device were a fixing temperature of 180°C, a fixing speed of 50 mm/sec, a nip width (width of the contact surface between the heating roll and the pressure roll) of 4 mm, and a pressure of 0.6 kg/c.
m2, 1kg/cm2, 1.5kg/cm2, 4.0k
g/cm2.

[0035] Furthermore, to measure the glossiness of the obtained image,
A Nippon Denshoku variable angle photometer model VG-1B was used.

Examples 2 and 3 and Comparative Examples 1 to 3 shown below
A toner sample was prepared under the same conditions as in Example 1 except for the toner composition, and evaluated under the same conditions.

<Example 2> Resin: Polyester resin (softening point: 119.1)...
………………………100 parts Colorant: Carbon black …………………………………
...10 parts <Example 3> Resin: Polyester resin (softening point: 119.8)...
………………………100 parts Colorant: Carbon black …………………………………
...10 parts <Comparative Example 1> Resin: Polyester resin (softening point: 130.5)...
………………………100 parts Colorant: Carbon black …………………………………
...10 parts <Comparative Example 2> Resin: Styrene-acrylic resin (softening point: 139.
4)……………………100 parts Colorant: Carbon black …………………………………
...10 parts <Comparative Example 3> Resin: Polyester resin (softening point: 105.4)...
………………………100 parts Colorant: Carbon black …………………………………
... 10 parts or more Regarding Examples 1 to 3 and Comparative Examples 1 to 3, the glossiness, offset occurrence situation, and loss tangent tan at 180 ° C. of the toner used in those examples
δ and fixing pressure 0.6kg/cm2, 1kg/c
Wrinkling and warping of envelopes and cardboard (postcards) were visually evaluated in the cases of m2, 1.5 kg/cm2, and 4.0 kg/cm2. These results are shown in Table 1.

[0038]

[Table 1]

As can be seen from the above results, in any of the examples, when the fixing pressure exceeds 1 kg/cm2, wrinkles and warpage occur in the envelope and cardboard, and the value of the loss tangent tan δ of the toner at 180° C. If it is 50 or more, hot offset will occur, and if it is 5 or less, the gloss level will be 30%.
As a result, a good image could not be obtained.

[0040]

According to the present invention, in the electrophotographic fixing method of the present invention in which the toner adhering surface is fixed by pressure heating, the value of the loss tangent tan δ of the toner used is 5 to 5 within the heating temperature range during fixing. By selecting one with a value of 50, the glossiness of the obtained image is high, toner offset is prevented, and the image can be fixed with a fixing pressure of 1 kg/cm 2 or less.

Furthermore, since the fixing pressure is as low as 1 kg/cm 2 or less, wrinkles and warpage of the toner support can be prevented.

[Brief explanation of drawings]

FIG. 1 is a partial explanatory diagram of a laser beam printer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Photoconductor, 2... Developer, 3... Toner, 4... Developer,
5... Laser light, 6... Charger, 7... Brush, 8... Transfer device,
9...Support, 10...Fixing device, 11...Heating roll, 12...
Pressure roll.

Claims (7)

[Claims] [Claim 1] An electrophotographic image fixing method in which a heating part is fixed by contact pressure bonding to a toner adhesion surface of a support, wherein the toner has a loss tangent value in the range of 5 to 50 at the heating temperature. . An image fixing method for electrophotography, characterized in that fixing is carried out at a contact pressure between the heating section and the toner adhesion surface that is less than a pressure that does not deform the toner support. 2. An electrophotographic image fixing method in which a heating unit is fixed by contact pressure bonding to a toner adhering surface of a support, wherein the toner has a loss tangent value in the range of 5 to 50 at the heating temperature. . An electrophotographic image fixing method, wherein fixing is performed at a contact pressure between the heating section and the toner adhesion surface of 0.3 to 1 kg/cm<2>. 3. The electrophotographic image fixing method according to claim 1, wherein the surface of the heating section comprises a fluororesin layer. 4. The electrophotographic image fixing method according to claim 1, wherein the heating section comprises a heating roll and a pressure roll. 5. An electrophotographic image fixing method according to claim 1, using a toner in which the main component of the toner binder is a polyester resin. 6. An electrophotographic image fixing method according to claim 1, wherein the toner binder is a polyester resin containing 1 to 50% by weight of a crosslinking component. 7. A photoreceptor made of a photoconductor, a charging means for charging the photoreceptor, a latent image forming means for forming an electrostatic latent image on the surface of the charged photoreceptor, and a toner for forming the electrostatic latent image. In an electrophotographic apparatus comprising a developing means for developing, a transfer means for transferring the toner image onto a support, and a fixing means for pressurizing and heating the support to which the toner image is transferred, the toner is fixed. The value of loss tangent at the heating temperature of 5
~50, and the contact pressure between the heating section of the fixing means and the support to which the toner image is transferred is 0.3 to 1 kg.
/cm2.