JP2003098720A - Image forming method and toner used therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method of a heating roller fixing system constituted so that at least one roller may have an elastic layer by which the deterioration of the elastic layer of the roller is prevented to make the granularity of a toner image after fixing good and image quality excellent. SOLUTION: The heating roller fixing method in which the toner image is thermally fixed by making a supporting body carrying the toner image consisting of at least resin and wax as a toner component pass between two rollers is used as this image forming method. In the method, at least one roller has elasticity and toner whose volatile component on a condition of 100 to 150 deg.C is <=0.15 weight % is used. It is more desirable to set the volatile component to <=0.10 weight %. In order to control the volatile component to <=0.15 weight %, kneading temperature and kneading time or the like in a toner producing stage are property selected and adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method in electrophotography and a toner used therefor.

[0002]

2. Description of the Related Art Conventionally, various electrophotographic methods have been described in US Pat. No. 2,297,691, Japanese Patent Publication No. 49-23910, and Japanese Patent Publication No. 43-24748. Uses a photoconductive material,
An electrical latent image is formed on the photoconductor by various means, then the latent image is developed with dry toner, the toner image is transferred to paper, etc., and then fixed by heating, pressing, etc., and a copy is made. I will get it.

The methods for developing an electric latent image are roughly classified into
A liquid developing method using a developer in which various pigments and dyes are finely dispersed in an insulating organic liquid, and a colorant such as carbon black on a natural or synthetic resin such as a cascade method, a magnetic brush method and a powder cloud method. There is a dry developing method using a toner having dispersed therein, and the dry developing method includes a one-component developing method and a two-component developing method using a carrier.

Methods of heating and fixing a toner image on a transfer paper are roughly classified into a contact fixing method and a non-contact fixing method. The former is heating roller fixing, belt fixing, and the latter is flash fixing and oven (atmosphere) fixing. To be

The heating roller fixing method is a fixing method having extremely high thermal efficiency because the toner image and the heating roller are in direct contact with each other, and the apparatus can be downsized. Therefore, the heating roller fixing method is used among them. As an apparatus, at least one roller forms an elastic layer, so that the thermal efficiency is higher than that of other heat fixing methods, so that it is widely used at present. However, in a heating roller fixing method in which at least one roller forms an elastic layer, deterioration of the elastic layer of the roller occurs due to long-term use, unevenness and cracks occur on the roller surface, and the original thermal efficiency greatly decreases. Alternatively, the toner image formed on the transfer paper is crushed and becomes non-uniform, which has a drawback that the image quality is greatly affected.

As a technique for solving this problem, some proposals have been made in the past. For example, JP-A-11-13
No. 3776 discloses a fixing device which causes the elastic layer to be distorted and a toner wax used in an amount of 0.1% by weight.
Toners containing -40% by weight have been proposed. Further, in Japanese Patent Laid-Open No. 10-282822, the hardness of the heating / pressurizing roller and the molecular weight of the toner are specified, whereby the glossiness of the color image is improved. However, in these cases, a sufficient effect cannot be obtained in a usage situation in which a large amount of copying is continuously repeated in a monochrome high-speed copying machine, wear of the elastic layer occurs, and the image essence deteriorates. Further, Japanese Patent Publication No. 8-27552 and Japanese Patent Laid-Open No. 2000-
No. 2,845,39 discusses a toner that regulates the amount of styrene oligomer in the toner. These have effective effects on the deterioration of the photoconductor, but prevent the deterioration of the elastic layer on the roller in the fixing device. , The full effect cannot be obtained. Japanese Unexamined Patent Application Publication No. 2000-347450 discusses a toner that defines the total content of the bisphenol A-PO adduct and the bisphenol A-EO adduct of the toner, which is also the elastic layer on the roller in the fixing device. Sufficient effect cannot be obtained for preventing deterioration. Even if the elastic layer in the fixing device is in a preheated state, heating and pressure of about 100 to 150 ° C. are constantly applied, so that a more severe state is set.
000-284539, JP 2000-347450.
It is considered that sufficient effects cannot be obtained within the scope of the invention described in the publication. Further, Japanese Patent No. 3168380 provides a toner that specifies the volatile component amount of the toner and the DSC peak of the wax, which has an effect on the fixability and the dispersibility of the material. No good image quality with granularity of is obtained. That is, in the heating roller fixing method in which at least one roller has an elastic layer, the elastic layer of the roller does not deteriorate, the surface property of the toner image formed on the transfer paper does not deteriorate, and the image quality is not largely affected. Such a fixing method has not been obtained yet.

Further, in recent years, the image quality has become higher and higher, and the toner particle size tends to become smaller. It is known that when the toner particle size is small, even if pressure is applied between the fixing rollers, it is difficult to apply pressure to the toner particles, and thus the fixing property is deteriorated. This tendency becomes remarkable especially in the case of a fixing device having a low surface pressure. Further, when thin paper is used as the transfer paper, the image quality is not particularly deteriorated due to the normal surface pressure. On the contrary, when thick paper is used, the toner is discharged in the same manner as when the surface pressure is increased. Are crushed and the volume and area of the toner image after fixing are changed to deteriorate the image quality. This phenomenon is particularly remarkable in the case of digital development, and the reproducibility of independent dots (this is called granularity) is greatly affected. Especially, the density of halftone should be uniform, but if microscopic density unevenness occurs, it gives a rough impression when viewed with the naked eye.

Here, as the physical evaluation value reflected in the roughness of the image quality, the granularity described below is generally used. The granularity has a high correlation with the subjective evaluation of the smoothness of the image. The smaller the granularity value, the smoother the image quality becomes, and conversely, the larger the granularity value, the rougher and poorer the image quality becomes. First, noise is the Wiener spectrum, which is the frequency characteristic of concentration fluctuations.
Can be measured by When the density fluctuation component having an average value of 0 is f (x) and the spatial frequency is u, the Wiener spectrum WS (u) is expressed by Expression 2. F (u) = ∫f (x) exp (−2πiux) dx Equation 1 WS (u) = F (u) ² Equation 2 Granularity (GS) is the frequency characteristic of WS and vision (Visual T
ransfer function (VTF) is a value obtained by integrating the product and is represented by the following equation. GS = exp (-1.8 <D>) ∫WS (u) ^1/2 VTF (u) du Formula 3 Exp (-1.8 <D>) corrects the difference between the density and the brightness perceived by humans. Is a coefficient for doing. <D> represents the average value of the density.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a heating roller fixing device for heating and fixing a toner image by passing between two rollers, at least one roller of which has elasticity, and the elasticity of the rollers. The present invention provides an image forming method capable of improving the granularity of a toner image after fixing by preventing the deterioration of the layer and having a good fixability of the toner image on a recording paper and excellent image quality.

[0010]

That is, the present invention is as follows.
(1) At least one roller in a heating roller fixing method for heating and fixing a toner image by passing a support carrying a toner image composed of at least a resin and a wax as a toner component between two rollers. An image forming method, characterized in that a toner having elasticity and having a volatile content at 100 to 150 ° C. of 0.15 wt% or less is used. (2) The volatile content is 0.10
The image forming method according to (1), wherein the content of the styrene oligomer is 80 wt% or less, and the styrene oligomer content of the toner is 80 ppm or less. 4. The method according to claim 4, wherein the total content of the bisphenol A-PO adduct and the bisphenol A-EO adduct contained in the toner is 500 ppm or less. (5) In the molecular weight distribution by gel permeation chromatography obtained for the THF-soluble content of the toner, the weight average molecular weight is from 500,000 to
The image forming method according to any one of claims 1 to 4, wherein 10 million components are 5 to 15% by weight, and 10 million or more components are 2 to 10% by weight.

According to another aspect of the present invention, (6)
The toner according to any one of (1) to (5) above,
(7) A toner container filled with the toner according to (6), and (8) an image forming apparatus equipped with the toner container according to (7). Is achieved.

As described above, in the image forming method of the heating roller fixing system according to the present invention, at least one roller has elasticity, and the volatile content of the toner at 100 to 150 ° C. is 0.15% by weight or less. It is characterized by being.
In a heating roller fixing device using a roller having elasticity, due to the elasticity of the roller, the surface of the toner image and the contact point with the transfer paper are brought into closer contact with each other, and variations in fixing property and image density and uneven gloss are reduced. In addition, 10 of toner
It has been found that when the volatile content at 0 to 150 ° C. is 0.15% by weight or less, deterioration of the roller elastic layer (elastic layer) can be prevented over time, and an image with good granularity can be obtained. That is, a small amount of the volatile component of the toner remaining on the roller after fixing at 100 to 150 ° C. enters into the elastic layer in a molecular state and plasticizes the elastic layer, whereby the flexibility of the elastic layer is developed and deteriorates. cause. Even in a preheated state where a copy is not used in the actual machine, the roller is always heated to 100 to 150 ° C. Therefore, a small amount of the toner remaining on the roller is 100 to 150 ° C. It is conceivable that the volatile components in the slab gradually enter the elastic layer. At this time, the volatile components at 100 ° C. or lower volatilize instantly in the actual machine and do not remain, so that it is considered that they do not substantially contribute to the contamination of the elastic layer. In other words, 10 of toner
When the volatile component at 0 to 150 ° C. is 0.15 wt% or less, the elasticity of the roller does not deteriorate, and the elasticity of the roller allows the surface of the toner image and the contact point with the transfer paper to be more closely attached. It is possible to obtain an image having good image granularity by reducing variations in fixing property and image density and unevenness of gloss.

The volatile component of the toner at 100 to 150 ° C. is more preferably 0.10% by weight or less. Most preferably, it is 0.05% by weight or less. If it exceeds 0.15% by weight, the elastic layer is deteriorated as described above during long-term use or storage.

Here, the volatile components of the toner at 100 to 150 ° C. include low molecular weight by-products derived from unreacted monomers of the binder resin composition described below and low molecular weight components remaining in other materials. . Further, low molecular weight components that are decomposed and generated during toner production are included. Unreacted monomers of the binder resin, such as styrene monomer, will volatilize without remaining at 100 ° C or less,
It is considered that it is not substantially involved in the deterioration of the elastic layer.

In order to obtain a toner having a volatile content of 0.15% by weight or less at 100 to 150 ° C., the amount of volatile content can be adjusted by the kneading temperature, kneading time, etc. in the toner manufacturing process. The desired toner can be obtained by kneading within the range.

In the present invention, 100 to 15 in the toner
The method of quantifying the volatile matter at 0 ° C. is measured by thermogravimetric measurement by measuring the amount of weight loss during heating between 100 and 150 ° C. with a thermobalance. Specifically, TG
A-7, PE7700 (manufactured by Perkin Elmer Co., Ltd.) and the like are used, 3 to 8 mg of toner is precisely weighed, and the weight of the toner after heating at 30 ° C./min to 30 to 100 ° C. under nitrogen stream , Then 100 ℃ -150 ℃ continuously
Was heated at a temperature rising rate of 10 ° C./min and held at 150 ° C. for 10 minutes to obtain the weight. (−) ÷ × 100
The value calculated by is the volatile content (% by weight) in the toner at 100 to 150 ° C.

When the amount of styrene oligomer contained in the toner is 80 ppm or less, further deterioration of the elastic layer can be prevented. More preferably, the amount of styrene oligomer is 50 ppm or less, and most preferably 30 ppm or less. The styrene oligomer represents a dimer to a 20mer of styrene. The limitation of the amount of styrene oligomer in the toner is particularly effective because the styrene oligomer has the strongest electron-donating property because the carbon bond is every other double bond in the molecular structure. This is because it is considered that the double bond is opened and causes deterioration.

The content of the styrene oligomer of 80 ppm or less can be obtained not only by controlling the manufacturing process of the toner but also by controlling the polymerization reaction of the resin. It is preferable to take a long reaction time in the polymerization reaction and to carry out the reaction at a high temperature, but from the economical viewpoint, it is preferable to carry out the suspension polymerization at 70 to 100 ° C. for 5 to 20 hours.

As a method for quantifying the amount of styrene oligomer in the present invention, it is quantified by gas chromatograph mass spectrometry. The measurement conditions are as follows. Ion source: E
I70Ev, detector: Cylindrical quadrupole off-axis secondary electron multiplier with brid rod, mass range: M / Z 29-70
0, column: DB-5, L = 30M, I.V. D = 0.25
mm, Film = 0.25μ, column temperature: 50 ° C. (h
old: 1 minute) to 300 ° C., 10 ° C./minute temperature increase, vaporization chamber temperature: 350 ° C., column pressure: He 100 (hold =
1 minute) to 150, 2 kPa / minute pressure increase.

Furthermore, when the total content of the bisphenol A-PO adduct and the bisphenol A-EO adduct of the toner is 500 ppm or less, deterioration of the elastic layer can be further prevented. Therefore, there is no deterioration of the roller having elasticity even in use or storage under high temperature for a long period of time,
Due to the elasticity of this roller, the surface of the toner image and the contact point with the transfer paper are brought into closer contact with each other, variation in fixability and image density and unevenness in gloss are reduced, and an image with good image granularity can be obtained. .

Further, GPC (gel permeation chromatography) determined by the THF-soluble content of the toner
In the molecular weight distribution according to
By containing 10 million components in an amount of 5 to 15% by weight and containing 10 million or more components in an amount of 2 to 10% by weight, an image with even better granularity can be obtained. This is explained by the stress on the toner during fixing, the rheological properties of the toner, and the molecular weight for obtaining this rheological property. Generally, the toner temperature during fixing is 10
0 ~ 200 ℃, the surface pressure of the roller at this time is 1.2 ~
It corresponds to 5.0 kg / cm2 and a nip width of 1.5 to 6.9 mm. This is 100-200 ℃, frequency 0.01-1
It was found that the toner storage elastic modulus G ′ at this time substantially corresponds to the stress of 00 rad / s, and greatly affects the granularity of the image after fixing.

To improve the granularity of the image after fixing
The storage elastic modulus G ′ is 100 to 200 ° C. and the frequency is 0.01.
5.0 × 10 at ~ 100 rad / s^Fourdyne /
cm ^TwoLess than or 1.0 x 10⁶dyne / cm^TwoSince
Above. That is, 100 to 200 ° C, frequency 0.01 to
G'is 5.0 × 10 at 100 rad / s.^Four~ 1.
0x10⁶dyne / cm^TwoIngredients in the range of
Has been found to be a factor that deteriorates the granularity of the image.
It was 100 to 200 ° C, frequency 0.01 to 100 rad
G'at 5.0 / s is 5.0 × 10^Fourdyne / cm^TwoNot yet
If it is full, the toner at the time of fixing will melt instantly and
Fixes unfixed toner image on transfer paper without deformation
Therefore, the granularity of the image after fixing is at a good level. on the other hand
100 to 200 ° C, frequency 0.01 to 100 rad / s
G'is 1.0 × 10⁶dyne / cm^TwoThat
For example, since it has many elastic components, it does not melt instantly, but during fixing
Since the image is fixed without being deformed by the stress of
The granularity becomes a good level. 100-200 ℃, frequency
G'is 5.0 × at the number of 0.01 to 100 rad / s.
10^Four~ 1.0 x 10⁶dyne / cm^TwoRange of ingredients
Does not melt instantly during fixing, and due to stress during fixing,
Image becomes uneven and the granularity deteriorates.
Image quality deteriorates.

On the other hand, 100 to 200 ° C., frequency 0.01
G'is 5.0 × 10 ⁴ dy at -100 rad / s
In order to obtain a rheological property of less than ne / cm ^2, the GP determined by the THF soluble content of the toner as described above.
In the molecular weight distribution by C, it is sufficient that the component having a weight average molecular weight of 500,000 to 10,000,000 is contained in an amount of 15% by weight or less. When it exceeds 15% by weight, G'is 5.0 × 10 ^4.
~1.0 × ¹⁰ 6 dyne / cm granularity of an image for the range of ² deteriorates. On the other hand, in order to improve the fixability and hot offset while improving the image quality, it is necessary to contain 2 to 10% by weight of a component having a weight average molecular weight of 10,000,000 or more. This component has a G ′ of 1.0 at 100 to 200 ° C. and a frequency of 0.01 to 100 rad / s.
The image quality does not deteriorate because it is more than × 10 ⁶ dyne / cm ² . On the other hand, if the content of the component having a weight average molecular weight of 10,000,000 or more is less than 2% by weight, the hot offset property deteriorates. If it exceeds 10% by weight, the fixability is deteriorated.

Here, the component having a weight average molecular weight of 10 million or more means the amount of the component soluble in THF up to the upper limit of the detection limit of GPC, and the molecular weight of the component soluble in THF but higher than the upper limit of the detection limit of GPC. Therefore, the amount of the component not measured by GPC and the THF-insoluble component, so-called gel content are included. The amount of components up to the upper limit of GPC detection,
The ratio of the amounts of the components that are soluble in THF but are not measured on GPC because they have a molecular weight that exceeds the upper limit of GPC detection depends on the measuring instrument and column used. Although this quantification method will be described later, this total amount with respect to the molecular weight of the entire toner is constant, and the total amount and the THF insoluble component, so-called gel content, are the components having a weight average molecular weight of 10,000,000 or more. .

On the other hand, in order to improve the dispersibility with each material while improving the image quality, fixing property and hot offset property, 5% by weight of a component having a weight average molecular weight of 500,000 to 10,000,000 is used.
It is necessary to contain the above. If it is less than 5% by weight, a component having a molecular weight of less than 500,000 and a component having a molecular weight of 10 million or more undergo phase separation, and the dispersibility of the material is deteriorated. That is, in order to improve the dispersibility with each material while improving the image quality, fixing property, and hot offset property, 5 to 15% by weight of the above component having a weight average molecular weight of 500,000 to 10,000,000 is contained. ,
This is achieved by containing 2 to 10% by weight of the component amount of 10 million or more.

The method for measuring the molecular weight distribution by GPC in the present invention is shown below. The column is stabilized in a heat chamber at 40 ° C., and THF (tetrahydrofuran) as a solvent is flown through the column at this temperature at a flow rate of 1 ml / min, and about 100 ml of a THF sample solution is injected for measurement. In measuring the molecular weight of a sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value and the count number of a calibration curve prepared from several kinds of monodisperse polystyrene standard samples. As a standard polystyrene sample for preparing a calibration curve, for example, Pressure Chemical Co. Manufactured by Toyo Soda Co., Ltd., Showa Denko Co., molecular weight 100-8
It is suitable to use a standard polystyrene sample of at least 10 points by using one having about 10 million. A refractive index detector is used as the detector. It is preferable to combine a plurality of commercially available polystyrene gel columns, for example, Shodex GPC KF-801, 802 manufactured by Showa Denko KK,
Examples include a combination of 803, 804, 805, 806, 800p.

The amount of components up to the upper limit of detection of GPC in the present invention can be quantified within the range of the upper limit of detection of columns combined in the above GPC measurement. THF
A method for measuring a molecular weight and a THF-insoluble matter which are soluble in the above but exceed the upper limit of the detection limit of GPC is measured as follows. About 1 g of toner is precisely weighed, about 100 g of THF is added to this, and it is sufficiently dissolved. Then, a poor solvent is added, and GPC of molecular weight is added.
After precipitating up to the upper limit of detection, it is separated by centrifugation and filtered at room temperature with JIS standard (P3801) 5C quantitative filter paper. This is the total amount of the molecular weight of the filter paper residue that is soluble in THF but exceeds the upper limit of the detection limit of GPC and the THF insoluble component, and this total amount is represented by the ratio (% by weight) of the toner to the filter paper residue. In addition, since solid substances such as pigments are present in the filter paper residue, this is separately determined by thermal analysis, and the amount is subtracted from the filter paper residue.

As the resin used in the toner of the present invention, all conventionally known resins can be used. For example, styrene, poly-α-stillstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene. -Maleic acid copolymer, styrene-n-butyl acrylate copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl acrylate copolymer, styrene-acrylonitrile A styrene resin such as an acrylic ester copolymer (a homopolymer or a copolymer containing styrene or a styrene substitute), a polyester resin, an epoxy resin, a vinyl chloride resin, a rosin-modified maleic acid resin, a phenol resin,
Examples thereof include polyethylene resin, polypropylene resin, petroleum resin, polyurethane resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, polyvinyl butyrate resin, and the like, and polyester resin is particularly preferable.

The polyester resin is obtained by polycondensation of alcohol and carboxylic acid. Examples of the alcohol used include glycols such as ethylene glycol, diene glycol, triethylene glycol, and propylene glycol, 1,4-bis (hydroxymeth) cyclohexane, and etherified bisphenols such as bisphenol A, and other divalent glycols. Examples thereof include alcohol monomers and trihydric or higher polyhydric alcohol monomers. Examples of the carboxylic acid include divalent organic acid monomers such as maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid and malonic acid, 1,2,4-benzenetricarboxylic acid, 1 2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid,
1,2,4-naphthalenetricarboxylic acid 1,2,5-
Hexanetricarboxylic acid, 1,3-dicarboxyl-2
Examples include trivalent or higher polyvalent carboxylic acid monomers such as methylenecarboxypropane, 1,2,7,8-octanetetracarboxylic acid. The Tg of the polyester resin is preferably 58 to 75 ° C.

The above resins can be used alone or in combination of two or more kinds. The method for producing these resins is not particularly limited, and any of bulk polymerization, solution polymerization, emulsion polymerization and suspension polymerization can be used.

In the present invention, a wax component may be used in order to improve releasability at the time of fixing the toner image. For example,
Polyolefin wax such as polypropylene wax and polyethylene wax, and natural wax such as candelilla wax, rice wax and carnauba wax can be used. The amount of wax component added is 0.5
-10 parts by weight is preferable.

In the toner used in the image forming method of the present invention, polarity control can be added to control the polarity. Examples of the polarity control agent in this case include nigrosine dyes, quaternary ammonium salts, amino group-containing polymers, metal-containing azo dyes, salicylic acid complex compounds, and phenol compounds.

As the colorant used in the present invention, all of the pigments and dyes conventionally used as colorants for toner can be applied. Specifically, carbon black, lamp black, iron black, ultramarine blue, nigrosine dye, aniline blue, chalco oil blue, oil black, azo oil black and the like are not particularly limited. The amount of colorant used is 1
10 to 10 parts by weight, preferably 3 to 7 parts by weight.

The method for producing the toner used in the present invention may be a conventionally known method, such as a binder resin, a colorant, a wax component,
In other cases, the charge control agent and the like are mixed using a mixer or the like, and the mixture is kneaded using a kneading machine such as a heat roll and an extruder, then cooled and solidified, and this is pulverized by a pulverizer such as a jet mill, After that, it can be classified.

Other additives may be added to the toner as required. Examples of the additive include silica, aluminum oxides, and titanium oxides. When the main purpose is to impart high fluidity, hydrophobically treated silica or rutile-type fine particle titanium oxide having an average primary particle size of 0.001 to 1 μm, preferably 0.005 to 0.1 μm is appropriately selected. You can choose
In particular, organic silane surface-treated silica or titania is preferable, and it is usually used in a proportion of 0.1 to 5% by weight, preferably 0.2 to 2% by weight.

When the toner of the present invention is used as a two-component dry toner, the carrier used as a mixture is, for example, a particle containing glass, iron, ferrite, nickel, zircon, silica or the like as a main component. Diameter 30-1000
a powder of about μm, or styrene containing the powder as a core material
Acrylic resin, silicone resin, polyamide resin,
It can be appropriately selected and used from those coated with polyvinylidene fluoride resin or the like.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of the present invention will be described with reference to the drawings. The digital copying machine shown in FIG. 1 is provided with a drum-shaped photoreceptor 1 inside by using a well-known electrophotographic method. A charger 2, an exposure unit 3, a developing unit 4, a transfer unit 5, a cleaning unit 6, and a fixing unit 10 for performing an electrophotographic copying process are arranged around the photoconductor 1 along a rotation direction indicated by an arrow A. ing. The exposure unit 3 reads the document placed on the document table 7 on the upper surface of the copying machine.
An electrostatic latent image is formed on the photoconductor 1 based on the image signal read by. The electrostatic latent image formed on the photoconductor 1 is
A toner image is formed by the developing unit 4, and the toner image is electrostatically transferred to the transfer sheet fed from the sheet feeding device 9 by the transfer unit 5. The transfer paper on which the toner image is placed is conveyed and fixed to the fixing unit 10, and then discharged to the outside of the machine. On the other hand, the untransferred portion and the photoconductor 1 with dirt are cleaned by the cleaning means 6 and the next image forming step is started.

Next, the fixing device will be described in detail.
FIG. 2 shows an example of a heat roller type fixing device, which has a heating means 24 such as a halogen lamp as a basic configuration.
The fixing roller 21 having (hereinafter referred to as “heater”)
And a pressure roller 25 that has an elastic layer 27 such as foamed silicone rubber on the core metal 26 and is pressed against the fixing roller 21.
It has and. A release layer 28 made of a PFA tube or the like is provided on the elastic layer 27 of the pressure roller 25. The fixing roller 21 is provided with an elastic layer 22 made of silicone rubber or the like on a cored bar 30, and a resin surface layer 23 made of fluorine resin or the like having a good releasability is formed for the purpose of preventing adhesion due to toner viscosity. . The thickness of the elastic layer 22 is usually 100 to 500 in consideration of image quality and heat transfer efficiency at the time of fixing.
A thickness of about μm is preferable. The resin surface layer 23 is made of a PFA tube or the like like the pressure roller 25, and its thickness is preferably about 10 to 50 μm in consideration of mechanical deterioration. Temperature detecting means 29 is provided on the outer peripheral surface of the fixing roller 21, and detects the surface temperature of the fixing roller 21 to control the heater 24 so as to keep the temperature substantially constant.

In the fixing device having such a structure, the fixing roller 21 and the pressure roller 25 are pressed against each other with a predetermined pressure to form the fixing nip portion N, and are driven by the driving means (not shown). By rotating in the directions of arrow R21 and arrow R25 respectively, the transfer material P is nipped and conveyed in the fixing nip portion N. At this time, the fixing roller 1 is controlled to a predetermined temperature by the heater 24, and when the toner image T on the transfer material P passes between the both rollers, the toner image T is thermally melted while receiving the pressure and exits the roller pair. The image is cooled and fixed on the transfer material P as a permanent image. The pressure roller has an outer diameter of 30 mm and a wall thickness of 6 m.
At m, the surface is covered with a conductive PFA tube and the rubber hardness on the shaft is 42 HS (Asuka C).
The fixing roller is made of an aluminum cored bar and has a wall thickness of 0.4 mm. In this structure, a pressure of 88 N on one side is applied to both ends of the roller to obtain the nip N, and the surface pressure at that time is 9.3 N / cm ² .

The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Examples 1 to 10 and Comparative Examples 1 to 3 (Toner formulation) Styrene-n-butyl acrylate copolymer 15 parts by weight Polyester resin 70 parts by weight Carbon black (Mitsubishi Kasei # 44) 10 parts by weight Charge control agent ( (Spiron Black TR-H: Hodogaya Chemical Co., Ltd.) 2 parts by weight Carnauba wax 3 parts by weight or more of the formulation was kneaded using a twin-screw extruder, pulverized and classified to obtain particles as a base. Then, using a Henschel mixer, silica fine powder (R-972: manufactured by Client Japan) is used as toner 10 in the particles serving as the base material.
The toners of Examples 1 to 10 and Comparative Examples 1 to 3 having the physical properties shown in Table 1 below were obtained by mixing 0.5 parts with 0 part. Further, with each toner and a carrier in which spherical ferrite particles having an average particle size of 50 μm are coated with silicone resin,
A developer having a toner concentration of 4.5% was prepared.

The toners produced as described above or images obtained by using the toners were evaluated as follows. The evaluation results are shown in Table 1 below. ◎ Method of evaluating fixability Fixing device having the structure shown in FIG. 1 (contact pressure: 0.7 × 10 ⁵ P
a) s) is attached to imagioMF6550 (manufactured by Ricoh Co., Ltd.), and the temperature of the heater is shaken to perform copying to obtain a fixed image. Mending tape (3M
(Made by the company), apply a certain amount of pressure, and then peel it off slowly. The image density before and after that is measured by a Macbeth densitometer, and the fixing ratio is calculated by the following formula. The temperature of the fixing roller is lowered stepwise, and the temperature at which the fixing ratio shown by the following formula becomes 80% or less is the fixing temperature. Fixing rate (%) = image density on tape / image density × 100

Evaluation Method of Hot Offset Occurrence Temperature Black solid 2c using the same fixing device as the above fixing method
It is the temperature at which hot offset occurs when an image original of m × 2 cm is shaken and the heater temperature is shaken to obtain a fixed image.

◎ Material Dispersibility Evaluation Method The toner flakes were colored with osmium and then evaluated with a transmission microscope TEM image.

Granularity Measurement Method First, the fixing device portion of imagio MF6550 (manufactured by Ricoh) was modified to obtain a fixing device having an elastic layer. With this evaluation machine, 10000 samples of Ricoh standard printer test chart are continuously printed. Then wait for 1 hour with the power on, then continue for 10 more
After copying 000 sheets, sample images were obtained. Next, the grayscale (halftone part) made up of dots in the printed image is used for the GenaScan500 by Dainippon Screen.
Image data was obtained by reading with a 0 scanner at 1000 dpi. From the obtained image data, the data was converted into a density distribution, and the granularity was evaluated by the above expression 3.

[0046]

[Table 1]

[0047]

According to the image forming method of the present invention, the heating roller provided with the elastic layer is not deteriorated, and the deterioration of the image quality of the toner transfer image due to the deterioration of the elastic layer can be prevented. further,
By preventing deterioration of the elastic layer, a high-quality image with good granularity can be obtained. Also, hot offset properties and material dispersibility can be improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of an image forming apparatus to which an image forming method of the present invention is applied.

FIG. 2 is a schematic cross-sectional view of a fixing device portion included in the image forming apparatus shown in FIG.

[Explanation of symbols]

1 photoconductor 2 charger 3 exposure means 4 developing means 5 Transfer means 6 Cleaning means 7 Document placing table 8 reading means 9 Paper feeder 10 Fixing means 21 fixing roller 22, 27 Elastic layer 23 resin surface 24 Heating means 25 pressure roller 26, 30 core 28 Release layer 29 Temperature detection means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshiaki Higaya             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Yutaka Takahashi             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Yasushi Furuichi             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Tadashi Kasai             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F term (reference) 2H005 AA06 CA14 EA06 EA07 FB02

Claims (8)

[Claims] 1. A heating roller fixing method for heating and fixing a toner image by passing a support carrying a toner image composed of at least a resin and a wax as a toner component between two rollers.
An image forming method, characterized in that a toner whose roller is elastic and whose volatile content at 100 to 150 ° C. is 0.15% by weight or less is used. 2. The image forming method according to claim 1, wherein the volatile content is 0.10% by weight or less. 3. The image forming method according to claim 1, wherein the styrene oligomer contained in the toner is 80 ppm or less. 4. Bisphenol A contained in the toner
The image forming method according to claim 1, wherein the total content of the —PO adduct and the bisphenol A-EO adduct is 500 ppm or less. 5. In the molecular weight distribution by gel permeation chromatography obtained for the THF-soluble content of the toner, 5 to 15% by weight of a component having a weight average molecular weight of 500,000 to 10,000,000, and a component amount of 10,000,000 or more. Is from 2 to 10% by weight.
The image forming method according to any one of 1. 6. The toner according to any one of claims 1 to 5. 7. A toner container filled with the toner according to claim 6. 8. An image forming apparatus equipped with the toner container according to claim 7.