JP2000250255A - Developer and image forming method using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the grade of solid black and to form a subdued image by using a developer containing a mixture of toners different from each other in particle diameter and having such characteristics as to ensure different fixabilities on a recording material in accordance with the particle diameter difference between the toners. SOLUTION: The developer contains a mixture of toners different from each other in particle diameter and has such characteristics as to ensure different fixabilities on a recording material in accordance with the particle diameter difference between the toners. The toners have plural peaks in the volume particle size distribution. Preferably the smaller particle diameter toner contains a binder having a lower molecular weight or a sharper molecular weight distribution. The developer may be a magnetic one-component developer, a nonmagnetic one-component developer or a nonmagnetic two-component developer. The developer 13 is housed in a developing means 5 in an electrophotographic device, different fixabilities of the toners are ensured and transfer is carried out twice using an interim transfer body 14, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer used in an electrophotographic apparatus such as a copying machine and a laser beam printer, and an image forming method using the developer.

[0002]

2. Description of the Related Art Conventionally, a toner (developer) used in an electrophotographic apparatus is a pulverized toner obtained by colliding a mass obtained by kneading a binder (binder resin), a colorant, and other components with a target and finely crushing the mass. Is commonly used.
The characteristics of such a toner are that the particle size distribution is generally wide, and that the toner composition is the same at any particle size. In recent years, with the development of pulverization and classification technology, toner particles having a fairly narrow distribution have been obtained.

[0003]

Generally, when a toner flies due to a developing electric field E, a force F applied to the toner is generated.
Is described by the following equation (1). Here, q is the charge amount of the toner. Accordingly, the equation of motion at this time can be expressed by the following equation (2), where m is the mass of the toner and a is the acceleration. Thus, the acceleration a when the toner flies is given by the following equation (3). It can be seen that when the developing electric field E is constant, toners having the same q / m have the same movement characteristics (acceleration a).

Here, when the charge amount q and the mass m are expressed by the charge density σ and the toner particle diameter d, the following expressions (4) and (5) are obtained, and the following expression (6) is obtained (where: A,
(B and C are constants). From the equation (6), it can be seen that the toner having a smaller particle diameter moves faster. In other words, when developing the electrostatic latent image, it can be seen that the toner having a small particle size adheres to the vicinity of the photosensitive drum within the same electric field intensity (constant E), and then the toner having a large particle size adheres.

[0005]

(Equation 1)

Accordingly, a large toner is developed on a toner having a small particle diameter when viewed from the photosensitive drum (FIG. 2).
a). Thereafter, when the toner is transferred to the recording material (usually paper) in the transfer step (FIGS. 2B and 2C), the toner having the small particle size is transferred onto the toner having the large particle size as viewed from the recording material. become. Thereafter, the toner is permanently fixed on the recording material in a fixing process.

[0007] By the way, as the final image after the recent fixing, the needs are diversifying from an image in which the toner is completely dissolved on the paper and a high gloss (high smoothness) to a moist image in which the gloss is suppressed. To meet such needs, the fixing speed has been changed, the toner particle diameter has been increased, or a toner that is difficult to melt has been used. However, studies have been made to use a toner with a small particle diameter for dot reproducibility, and a toner with a low molecular weight binder that has increased covering power for the purpose of speeding up. There is a problem that the image becomes embossed (FIG. 3c) in the fiber and the quality of solid black deteriorates.

Even when a toner having a plurality of toner particle size peaks is used, the image after fixing becomes an image with high gloss (high smoothness) because the molecular weight of the toner binder is the same. For this reason, the desired moist image (in the case of using a portable gloss meter PG-3D type (75 degrees incident) manufactured by Nippon Denshoku Industries Co., Ltd., gloss 6 to
(8% or less).

In view of the above, the present invention provides a solid black image by changing the fixing property of the toner according to the difference in the particle diameter of the toner and further using two transfer steps, thereby providing a moist image. The purpose is to do.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has been made in consideration of the above-mentioned circumstances. The present invention provides a developer characterized in that the developer has different characteristics in fixing properties. Further, in the volume particle size distribution of the toner, has a plurality of peaks, in this case, the smaller the particle size of the toner, the lower the molecular weight of the binder, or the smaller the particle size of the toner,
It is preferable to sharpen the molecular weight distribution of the binder. Further, the developer is a magnetic one-component system, a non-magnetic one-component system,
Alternatively, a non-magnetic two-component developer can be used. In addition, the electrostatic latent image formed on the surface of the photosensitive drum is developed using the developer described in any of the above, and then the transfer process is performed twice using an intermediate transfer body, so that the recording material is formed. Provided is an image forming method characterized by transferring and permanently fixing.

As described above, in the present invention, since the smaller the particle size of the toner, the better the mobility, the small particle size toner adheres to the lowermost layer (near the photosensitive drum surface) of the developing toner layer, A toner having a larger diameter is more likely to adhere to the upper layer. After that, when the transfer step is performed twice, the toner is transferred onto the paper with the same toner layer configuration as the developed toner layer on the photoreceptor, and after fixing, the solid black can be reduced, and the fixing property is changed by the difference in particle diameter. Therefore, the toner having a small particle size in the lower layer is easily melted, and the adhesiveness between the paper and the toner is improved, and the toner having a large particle size in the upper layer is hardly melted, so that the gloss after fixing can be suppressed (FIG. 4). Become.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. First, the material and manufacturing method of the toner (developer) according to the present invention will be described.
Examples of the binder used in the toner of the present invention include a homopolymer of styrene such as polystyrene, poly p-chlorostyrene and polyvinyl toluene and a substituted product thereof; a styrene-p-chlorostyrene copolymer, and styrene-vinyl toluene. Copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-ethyl-2-ethylhexyl copolymer Polymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer , Styrene-acrylonitrile copolymer, styrene-bi Methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene- Styrene-based copolymers such as maleic acid copolymer and styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester,
Polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc. These binders may be used alone or as a mixture.

As the colorant used in the toner of the present invention, all known colorants can be used. For example, carbon black, iron black, graphite, nigrosine, metal complexes of monoazo dyes, ultramarine, copper phthalocyanine, methylene blue And dyes such as chrome yellow, quinoline yellow, Hansa yellow, benzidine yellow, Dupont oil red, quinacridone, and various lake pigments.

In the case of non-magnetic toner particles, the content of such a coloring agent is 2 to 3 parts per 100 parts by weight of the binder.
It is desirably about 0 parts by weight. When it is contained in the magnetic toner, it is desirable that the amount is about 0.5 to 15 parts by weight based on 100 parts by weight of the magnetic toner particles.

The charge control agent is added as needed to control the charge polarity and charge amount of the toner. In the present invention, a known appropriate charge control agent may be selected according to the polarity and charge amount of the target toner, and there is no particular limitation. For example, metal complex salt azo dyes, nigrosine dyes and the like can be mentioned, and these are selected according to required characteristics. The content of such a charge control agent is preferably about 0.2 to 10 parts by weight with respect to 100 parts by weight of the resin in the non-magnetic toner particles. When the toner is contained in the magnetic toner, the magnetic toner particles 10
It is desirable that the amount is about 0.2 to 10 parts by weight with respect to 0 parts by weight.

The wax is added as necessary as a release agent at the time of fixing an image to prevent offset. For example, various known waxes such as polyethylene wax, polypropylene wax, and silicone wax are used. These may be selected according to the required characteristics. The content of such a wax,
In the case of non-magnetic toner particles, the amount is preferably about 2 to 10 parts by weight based on 100 parts by weight of the binder. In the case of the magnetic toner, it is preferable that the amount is about 0.5 to 10 parts by weight based on 100 parts by weight of the resin.

From the above-mentioned colorants, charge control agents, waxes, magnetic powders, other additives, etc., necessary ones are selected, and a predetermined amount thereof and a binder are melted and kneaded, and after cooling, Coarsely pulverized with a hammer mill, cutter mill, or the like. Next, after further finely pulverizing with a jet mill, an ong mill or the like, the particles are classified into a preferable volume average or number average particle size range.

If necessary, the toner which has been subjected to the classifying step may be used as an external additive such as a fluidity improver, a lubricant, an abrasive, a conductivity-imparting agent, a fixing aid, etc. An internal additive is added. For example, silica, titanium oxide,
As the toner binder, the above resin powder, polytetrafluoroethylene powder, polyvinyl fluoride powder, molybdenum disulfide, tungsten disulfide, boron nitride,
Metal salts of higher resin acids such as lead oxide, antimony oxide, strontium sulfate, aluminum sulfate, calcium carbonate, strontium titanate, cerium oxide, strotium oxide, zinc stearate, graphite, barium fluoride, calcium fluoride, carbon fluoride There are known fine particles such as carbon black, conductive tin oxide, and the like, and some of these fine particles simultaneously have two or more kinds of functions as the above functional agent.

The toner of the present invention may contain, if necessary, iron powder,
It can be used as a two-component developer by being mixed with carrier particles such as glass beads, nickel powder, and ferrite powder. When the toner is used as a one-component magnetic developer, examples of the magnetic powder include ferromagnetic elements and alloys and compounds containing the same, such as iron, cobalt, nickel, and manganese such as magnetite, hematite, and ferrite. Alloys and compounds, other ferromagnetic alloys,
A known magnetic material may be contained. These magnetic powders have an average particle size of 0.03 to 5 μm, preferably 0.1 to 1 μm.
And added at a ratio of 1 to 80% by weight, preferably 20 to 60% by weight of the toner weight.

In particular, in the embodiment of the present invention, in order to change the fixing property of the toner, the molecular weight of the toner binder is appropriately changed within a certain range. Note that the toner fixing property has a correlation with the temperature, and the fixing temperature is operated between a minimum temperature at which the toner is fixed on the recording material and a high-temperature offset temperature at which the toner does not adhere to the fixing roller. From this viewpoint, the number average molecular weight (Mn) of the ordinary toner binder is about 2,000 to
10,000, weight average molecular weight (Mw) of about 4000-3
0000, and the molecular weight distribution (Mw / Mn) is 1.4 to
Five of them are used. In the present embodiment, this Mn,
By changing Mw and Mw / Mn, the fixability of the toner is changed.

In the present invention, in the production of the toner as described above, two kinds of toners having different particle diameters are prepared, and these are mixed to obtain the toner of the present invention. At this time, a toner having a small particle size is prepared such that a toner having a smaller particle size has a property of being more easily fixed on a recording material. In order to achieve the object of the present invention, it is preferable that the smaller the particle size of the toner, the lower the molecular weight of the binder and the sharper the molecular weight distribution of the binder. Further, among the two types of toners having different particle diameters, it is preferable that the small particle size toner has a particle size of 4 to 8 μm, and the large particle size toner has a particle size of 6 to 10 μm.

It is preferable that the mixing ratio (number) of the two kinds of toners having different particle diameters is in the range of large / small = 3 to 1/2. If the amount of the small particle toner is too small in the mixing ratio of the two, the image quality is deteriorated, which is not preferable. The toner of the present invention thus obtained has a plurality of peaks, preferably two peaks in the volume particle size distribution.

Next, the image forming method of the present invention will be described with reference to the accompanying drawings. As an example of an apparatus such as a copying machine or a printer for carrying out the image forming method of the present invention, there is an electrophotographic apparatus shown in FIG. 1, and a developing means 5 contains a developer 13 of the present invention. The toner of the developer 13 is a magnetic toner or a non-magnetic toner. In an image forming apparatus other than the apparatus shown in FIG. 1, a developing unit using a two-component developer having a toner and a carrier may be used.

A charging means (for example, a charging roller, a charging brush, a charging blade or the like as a contact charging means) 2 to which a voltage is applied by a bias applying means 3 is used for a photosensitive drum (for example, an OPC photosensitive drum) as an electrostatic image carrier. The surface of a drum, amorphous silicone or polycrystalline photosensitive drum 1 is charged, and an electrostatic image is formed on the photosensitive drum 1 by exposure (eg, laser light or light from a halogen lamp) 4. Toner coating blade (eg, elastic blade, magnetic blade, etc.) 6 and magnetic field generating means (eg, magnet)
A developer 13 containing magnetic toner contained in a developing means 5 having a developing sleeve 7 containing
Develop the electrostatic image.

For development, a regular development system or a reversal development system is used. In the developing section, an alternating bias, a pulse bias and / or a DC bias are applied to the developing sleeve 7 by the bias applying means 8 as necessary. Next, the toner image on the photosensitive drum 1 is transferred to an intermediate transfer body (for example, an intermediate transfer drum, an intermediate transfer belt, etc.) 14 by a transfer unit (for example, a voltage is applied by a bias applying unit 12).
The developed image is electrostatically transferred by being charged from the back surface (the side opposite to the photosensitive drum 1 side) of the intermediate transfer body 14 by a transfer roller, a transfer blade or the like 15.

Next, when the recording material P is conveyed and reaches the secondary transfer section, a transfer means (for example, a transfer roller, a transfer belt, or the like) to which a voltage is applied by the bias applying means 10.
9, the toner image on the surface of the intermediate transfer member 14 is electrostatically transferred onto the recording material P by charging while being pressed from the back surface (the side opposite to the intermediate transfer member 11) of the recording material P. Thereafter, the recording material P separated from the intermediate transfer member 14 is subjected to a heat fixing process by the heat fixing device 16 to fix the toner image on the recording material P.

On the other hand, the toner remaining on the intermediate transfer body 14 after the transfer process is developed on the photosensitive drum 1 by a potential difference from the photosensitive drum 1 and, if necessary, cleaning means (for example, a cleaning blade, a cleaning roller, a cleaning roller, Brush or the like 17.
After the cleaning of the photosensitive drum 1, the process starting from the charging step by the charging means 2 is repeated again. Image formation is performed by repeating the above steps.

[0028]

Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited thereto.
For example, there are four developing machines, each containing a color toner (usually yellow, magenta, cyan, black),
Needless to say, the present invention can also be applied to a full-color image forming apparatus or the like in which multiple transfer is performed on the intermediate transfer body 14 and then collectively transferred to the recording material P.

Example 1 The toner used was a mixture of a magnetic one-component toner having an average particle diameter of 6 μm (toner A) and an average particle diameter of 8 μm (toner B) in a number ratio of 1: 1. Was. Here, the average particle size is a volume particle size. FIG. 5 shows the particle size distribution at this time. In particular, the binder of toner A has a number average molecular weight (Mn) of about 3000 and a weight average molecular weight (Mw) of about 1
2000, a molecular weight distribution (Mw / Mn) of 4, and a number average molecular weight (Mn) of the binder of the toner B is about 5000;
A toner having a weight average molecular weight (Mw) of about 15,000 and a molecular weight distribution (Mw / Mn) of 3 was used. At this time, each external additive was adjusted so that the surface charge density of the toner was substantially constant. Table 1 shows the results of images formed using this toner. As a result, gloss could be reduced at the same fixing temperature.

Example 2 Next, the toner used in Example 2 was a magnetic one-component toner having an average particle diameter of 6 μm (toner A) and an average particle diameter of 8 μm.
(Toner B) was used in a number ratio of 1: 1. Here, the number average molecular weight (Mn) of the binder of the toner A is about 6000, and the weight average molecular weight (Mw).
Is about 12000, molecular weight distribution (Mw / Mn) 2,
The number average molecular weight (Mn) of the binder of the toner B is about 50
A toner having a weight average molecular weight (Mw) of about 15,000 and a molecular weight distribution (Mw / Mn) of 3 was used. At this time, each external additive was adjusted so that the surface charge density of the toner was substantially constant. Table 1 shows the result of forming an image using this toner. As a result, gloss could be further reduced at the same fixing temperature.

Example 3 The toner used in Example 3 was a magnetic one-component toner having an average particle diameter of 6 μm (toner A) and an average particle diameter of 8 μm.
m (toner B) and a number ratio of 1: 1 are used. In particular, the binder of toner A has a number average molecular weight (Mn) of about 4000 and a weight average molecular weight (Mw) of about 1
0000, a molecular weight distribution (Mw / Mn) of 2.5, and a number average molecular weight (Mn) of the binder of the toner B is about 500.
A toner having a weight average molecular weight (Mw) of about 15,000 and a molecular weight distribution (Mw / Mn) of 3 was used. At this time, each external additive was adjusted so that the surface charge density of the toner was substantially constant. Table 1 shows the result of forming an image using this toner. As a result, gloss can be reduced at the same fixing temperature, and a moist image can be obtained more than ever.

[0032]

Table 1: Effect of the present embodiment (the same fixing temperature 1)
(Measured at 50 ° C) Note) Default: Use only the average particle size of 8 μm (Toner B)

[0033]

As described above, according to the present invention,
Using a toner having multiple peaks of toner particle diameter, the toner fixing property is changed due to the difference in toner particle diameter, and the transfer is performed twice using an intermediate transfer member or the like, thereby deteriorating the quality of solid black after fixing. Instead, the gloss can be easily reduced, and a moist image can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment.

FIG. 2 is a diagram illustrating a toner layer when transferred from a photosensitive drum.

FIG. 3 is a view for explaining a warpage after fixing due to unevenness of paper.

FIG. 4 is a diagram illustrating a state after fixing in the embodiment.

FIG. 5 is a diagram illustrating a particle size distribution of a toner having two peaks.

[Explanation of symbols]

 1: photosensitive drum 5: developing device 13: toner (developer) 14: intermediate transfer member P: recording material

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Fujita 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Kazushige Nishiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Non-corp.

Claims (12)

[Claims] 1. A developer comprising a mixture of toners having different particle diameters, wherein the developer has a characteristic that a fixing property on a recording material is different due to a difference in particle diameter of the toner. 2. The developer according to claim 1, wherein the smaller the particle size of the toner, the better the fixability on the recording material. 3. The developer according to claim 1, wherein the smaller the particle size of the toner, the lower the molecular weight of the binder. 4. The developer according to claim 1, which has a plurality of peaks in a volume particle size distribution. 5. The developer according to claim 1, wherein the smaller the particle size of the toner, the sharper the molecular weight distribution of the binder. 6. The toner according to claim 1, wherein the particle size distribution of the toner has two peaks, the small particle size toner has a peak at a particle size of 4 to 8 μm, and the large particle size toner has a peak at a particle size of 6 to 10 μm. The developer according to claim 1. 7. The developer according to claim 1, which is a magnetic one-component developer. 8. The developer according to claim 1, which is a non-magnetic one-component developer. 9. The developer according to claim 1, which is a non-magnetic two-component developer. 10. The method according to claim 1, wherein:
An image forming method, comprising developing the electrostatic latent image formed on the surface of the photosensitive drum using the developer described in the above section. 11. The image forming method according to claim 10, wherein the electrostatic latent image formed on the surface of the photosensitive drum is developed by a laser optical system. 12. The image forming method according to claim 10, wherein an image formed on the surface of the photosensitive drum is transferred to a recording material in two transfer steps.