JPH08220794A - Image forming method - Google Patents

Abstract

PURPOSE: To provide an image forming method having a high comprehensive transfer ratio in transferring a toner image by using an intermediate transfer body. CONSTITUTION: The toner image is formed on an electrostatic latent image holding body by toner particles whose shape factor SF-1 measured by a luzex is 111 to 116, whose shape factor SF-2 is 110 to 140 and SF-2/SF-1 is <1, and also, containing 5-40wt.% low softening point material, and the toner image on the electrostatic latent image holding body 1 is transferred to the intermediate transfer body 5, a transfer means is brought into contact with a transfer material 6, the toner image on the intermediate transfer body 5 is transferred to the transfer material 6, then, the toner image on the transfer material 6 is heated and fixed on the transfer material 6 by a heating means.

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 for forming a multicolor image using an intermediate transfer member utilizing electrophotography. Furthermore, the present invention is an image forming method in which a toner image is previously formed on an electrostatic latent image bearing member, the toner image is transferred onto an intermediate transfer member, and then transferred collectively onto a transfer material. The present invention relates to a full-color image forming method used for image forming such as fax and fax.

[0002]

2. Description of the Related Art Conventionally, in a full-color copying machine, 4
The electrostatic latent image formed on each photoconductor using two photoconductors and a belt-shaped transfer belt is developed using cyan, magenta, yellow, and black toners, and then the transfer material is conveyed between the photoconductor and the belt transfer body to be straight. After transferring between passes, a method of forming a full-color image, or winding the transfer material around the surface of the transfer body facing the photoconductor by an electrostatic force or a mechanical action such as a gripper, and performing the development-transfer process four times As a result, a method of obtaining a full-color image is generally used.

In recent years, ordinary paper or film for overhead projector (OH) has been used as a transfer material for full color.
In addition to P), there is an increasing need to develop various materials such as cardboard, cards, and small size paper such as postcards. In the method using the above-described four photoconductors, the transfer material is conveyed straight, so that the range of application to various transfer materials is wide, but it is necessary to accurately superpose a plurality of toner images on a predetermined transfer material position. However, there is a problem in that it is difficult to obtain a high-quality image with good reproducibility due to a slight difference in registration, which complicates the transfer material transport mechanism, leading to an increase in reliability and the number of parts. Also, when thick paper with a large basis weight is used in a method in which the transfer material is adsorbed on the surface of the transfer body and wound, the rear end of the transfer material causes poor adhesion due to the stiffness of the transfer material, resulting in an image based on the transfer. It causes defects and is not preferable. Image defects may also occur on small size paper.

A full-color image device using a drum-shaped intermediate transfer member is already known from US Pat. No. 5,187,526 and Japanese Patent Laid-Open No. 4-16426.
In US Pat. No. 5,187,526, the intermediate transfer roller having a surface layer made of polyurethane as a base material has a volume resistivity value of less than 10 ⁹ Ω · cm and is composed of the same surface layer. It is described that high image quality can be obtained when the volume resistivity of the transfer roller is 10 ¹⁰ Ω · cm or more. However, in such a system, a high output electric field is required in order to give a sufficient transfer charge amount to the toner at the time of transferring the toner to the transfer material. Therefore, it is composed of polyurethane in which the conductivity-imparting material is dispersed. The surface layer thus formed locally breaks down, and a noticeable image disturbance occurs in a halftone image with a small amount of toner, which is not preferable. Further, such high voltage application tends to cause transfer failure due to leakage of transfer current as the resistance of the transfer material decreases in an environment of high humidity where relative humidity exceeds 60% RH. Is 40
Even in a low humidity environment of less than or equal to% RH, it may cause transfer failure due to uneven resistance unevenness of the transfer material.

Japanese Patent Application Laid-Open No. 59-15739 and Japanese Patent Application Laid-Open No. 59-5046 describe the relationship between the structure using an intermediate transfer member and the toner. However, in this publication, an adhesive intermediate transfer member is used.
It is only mentioned that toner of 0 μm or less can be efficiently transferred. Usually, in a system using an intermediate transfer member, it is necessary to transfer the toner color image from the photosensitive member to the intermediate transfer member once, and then transfer it from the intermediate transfer member onto the transfer material again. In comparison, it is necessary to improve the toner transfer efficiency more than ever before. In particular, when a full-color copying machine that transfers a plurality of toner images after development is used, the amount of toner on the photoconductor increases compared to the case of a single color black toner used in a black-and-white copying machine, and the conventional toner is simply used. It is difficult to improve the transfer efficiency only by using it. Furthermore, when a normal toner is used, the surface of the photoconductor or the photoconductor or the intermediary transfer member may be damaged due to a sliding force or a rubbing force between the photoconductor or the intermediate transfer member and / or the photoconductor and the intermediate transfer member. Toner fusion or filming may occur on the surface of the intermediate transfer member to deteriorate the transfer efficiency. In full color, the toner images of four colors may not be transferred uniformly, which may cause problems in color unevenness and color balance. It was difficult to stably output a high-quality full-color image.

Further, as a toner to be mounted on an ordinary full-color copying machine, it is necessary that the color toners are sufficiently mixed in the fixing step, which is important for improving color reproducibility and transparency of an OHP image. Therefore, it is generally preferable to use a sharp-melting resin having a low molecular weight for the color toner as compared with the black toner. Further, a release agent having a relatively high crystallinity represented by polyethylene wax or polypropylene wax is used for ordinary black toner in order to improve the high humidity offset property at the time of fixing. However, in a full-color toner, the transparency of an OHP toner image is significantly impaired when it is output due to the crystallinity of the release agent. Therefore, the high-temperature offset property is consequently improved by uniformly applying silicone oil or the like to the heat fixing roller without adding a release agent as a color toner constituent. However, since the transfer material having the toner-fixed image thus obtained has extra silicone oil or the like attached to its surface,
It is not preferable because it causes discomfort when used by the user. As described above, there are many difficult problems at present in forming a full-color image using an intermediate transfer member having many contact portions. JP-A-59-15
Japanese Patent Laid-Open No. 739 and Japanese Patent Laid-Open No. 59-5046 do not propose any measures for the toner or the intermediate transfer member in this respect.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method which solves the above problems.

That is, an object of the present invention is to provide an image forming method in which toner fusion and filming do not occur on the photosensitive member and the intermediate transfer member.

Another object of the present invention is to provide an image forming method capable of favorably transferring to small size transfer materials such as cardboard, cards and postcards.

Another object of the present invention is to provide an image forming method excellent in transfer efficiency.

It is another object of the present invention to provide an image forming method having a low temperature fixing property in which a plurality of toners are sufficiently mixed.

Another object of the present invention is to provide an image forming method for obtaining a color OHP image having excellent transparency.

[0013]

According to the present invention, a shape factor SF measured by Luzex is formed on an electrostatic latent image carrier.
-1 is 111 to 160, and the shape factor SF-2 is 1
10 to 140, the value of SF-2 / SF-1 is 1 or less, and the toner image is formed by the toner particles containing the low softening point substance in an amount of 5 to 40% by weight. The toner image on the holding member is transferred to the intermediate transfer member, the transfer means is brought into contact with the transfer material, the toner image on the intermediate transfer material is transferred to the transfer material, and the toner image on the transfer material is heated. The present invention relates to an image forming method characterized by heat-fixing on the transfer material.

As the intermediate transfer body and the transfer means used in the present invention, general materials are used. In the present invention, the volume specific resistance value of the transfer means is set smaller than the volume specific resistance value of the intermediate transfer body. By doing so, the voltage applied to the transfer means can be reduced, a good toner image can be formed on the transfer material, and winding of the transfer material around the intermediate transfer body can be prevented. Particularly, it is particularly preferable that the volume specific resistance value of the intermediate transfer member is 10 times or more than the volume specific resistance value of the transfer means 1.

The hardness of the intermediate transfer body and the transfer means is JIS
It is measured according to K-6301. The hardness of the intermediate transfer member used in the present invention is preferably an elastic layer belonging to the range of 10 to 40 degrees, while the hardness of the transfer means is 41 to 80 degrees, which is higher than the hardness of the intermediate transfer member. Those having a value are preferable for preventing the transfer material from being wrapped around the intermediate transfer member. If the hardness of the intermediate transfer body and the hardness of the transfer means are opposite, a recess is formed on the side of the intermediate transfer body, and winding of the transfer material around the intermediate transfer body occurs, which is not preferable.

In the present invention, SF-1 indicating the shape factor
Is, for example, Hitachi FE-SEM (S-800)
100 random toner images magnified at a magnification of 500 are randomly sampled, and the image information is, for example, an image analysis device (Luzex I manufactured by Nicore Co.) via an interface.
It is introduced into II) and analyzed, and the value calculated by the following formula is defined as shape factor SF-1.

[0017]

[Outside 1] [Wherein MXLNG represents the absolute maximum length of the toner particles,
AREA indicates the projected area of the toner particles. Further, the shape factor SF-2 refers to a value obtained by calculating from the following formula.

[0018]

[Outside 2] [In the formula, PERI indicates the circumference of the toner particles, and
A indicates the projected area of the toner particles. The shape factor SF-1 indicates the degree of roundness of toner particles,
The shape factor SF-2 indicates the degree of unevenness of the toner particles.

When the toner shape factor SF-1 is less than 111, cleaning failure generally tends to occur. However, as in the present invention, a substance having a low softening point of 5 to 4 is added to the toner.
The one containing 0% by weight shows a marked improvement in cleaning characteristics, but under severe conditions, some anxiety remains.

Further, in the case of copying a large number of sheets, the external additive is likely to be buried in the toner surface, resulting in the deterioration of image quality. On the other hand, when SF-1 exceeds 160, the toner is liable to be crushed in the developing device, the particle size distribution is varied, the toner tribo distribution is easily bloated, and the ground fog and the reverse fog are apt to occur. In addition, the transfer efficiency is lowered, which is not preferable.

When a full-color copying machine that transfers a plurality of toner images after development is used, the amount of toner on the photoconductor increases as compared with the case of one color black toner used in a black-and-white copying machine. It is difficult to improve the transfer efficiency only by using the regular toner. Further, in the case of using a usual irregular toner, between the photoconductor and the cleaning member, between the intermediate transfer member and the cleaning member, and /
Alternatively, due to the shearing force or the rubbing force between the photoconductor and the intermediate transfer body, toner fusion or filming occurs on the surface of the photoconductor or the intermediate transfer body, and the transfer efficiency is likely to deteriorate. In the generation of a full-color image, it is difficult to transfer toner images of four colors uniformly, and when an intermediate transfer member is used, problems such as color unevenness and color balance tend to occur, and a high-quality full-color image is stabilized. It is not easy to output.

Further, when the shape factor SF-1 of the toner particles exceeds 160, the toner particles are separated from the spherical shape and approach an irregular shape,
A decrease in the transfer efficiency of the toner image during transfer from the electrostatic image carrier to the intermediate transfer member was observed, and a decrease in the transfer efficiency of the toner image during transfer from the intermediate transfer member to the transfer material was also observed. To improve the transfer efficiency of the toner image,
The shape factor SF-2 of the toner particles is 110 to 140, and the value of SF-1 / SF-2 is preferably 1 or less.
Further, when the shape factor SF-2 of the toner particles exceeds 140 and the value of SF-1 / SF-2 exceeds 1, the surface of the toner particles is not smooth, and the toner particles have many irregularities, Transfer efficiency tends to decrease during transfer from the electrostatic image carrier to the intermediate transfer member and during transfer from the intermediate transfer member to the transfer material.

The transfer efficiency is measured as follows, for example.

The transfer rate of the toner image from the electrostatic image holding member to the intermediate transfer member is determined by collecting the toner image (image density of about 1.5) formed on the electrostatic image holding member with a transparent adhesive tape, The image density is measured by a Macbeth densitometer or a color reflection densitometer (for example, Color reflection densitometer).
ether X-RITE 404A manufact
ured by X-Rite Co. ).
Next, the toner image is formed again on the electrostatic image holding member, the toner image is transferred to the intermediate transfer member, and the toner image on the intermediate transfer member corresponding to the toner image collected on the electrostatic image holding member is made transparent. Collect with an adhesive tape and measure the image density in the same manner.

Transfer rate A from electrostatic image carrier to intermediate transfer medium
(%) Calculate as follows.

[0026]

[Outside 3]

Next, the transfer rate B from the intermediate transfer member to the transfer material
(%) Is similarly calculated as follows.

[0028]

[Outside 4]

The total transfer rate C is calculated as follows.

Totally transfer rate C = (transfer rate A) × (transfer rate B)

In the present invention, since the intermediate transfer member is provided in order to deal with various types of transfer materials, the transfer step is performed substantially twice, so that the transfer efficiency is remarkably lowered and the toner utilization efficiency is lowered. It becomes a problem. In digital full-color copying machines and printers, color image
(Blue) filter, G (green) filter, R
After color separation using a (red) filter, a dot latent image of 20 to 70 μm is formed on the photoconductor to form a Y (yellow) toner, an M (magenta) toner, a C (cyan) toner, and a B toner.
It is necessary to reproduce a multicolor image faithful to the original by using the subtractive color mixing action by using each color toner of (black) toner. At this time, since a large amount of Y toner, M toner, C toner, and B toner are placed on the photosensitive member or the intermediate transfer member in accordance with the color information of the original or CRT, each color used in the present invention. Toner requires extremely high transferability,
In order to realize this, it is preferable to use toner particles whose toner shape factors SF-1 and SF-2 satisfy the above conditions.

In order to faithfully develop minute latent image dots for higher image quality, the toner particles have a weight average diameter of 10
It is preferably less than or equal to μm (preferably 4 to 8 μm), and the coefficient of variation (A) in the number distribution is less than or equal to 35%. In the case of toner particles having a weight average particle diameter of less than 4 μm, a large amount of toner particles remain after transfer on the photoconductor or the intermediate transfer member due to a decrease in transfer efficiency, and moreover, it is likely to cause fog and uneven image uniformity due to transfer failure. It is not preferable as the toner used in the present invention. When the weight average particle diameter of the toner particles exceeds 10 μm, fusion to the surface of the photosensitive member, a member such as an intermediate transfer material is likely to occur, and when the variation coefficient in the number distribution of the toner particles exceeds 35%, the tendency is further increased. Get stronger.

The particle size distribution of toner particles can be measured by various methods. In the present invention, a Coulter counter is used.

For example, a Coulter Counter TA-II type (manufactured by Coulter) is used as a measuring device, and an interface (manufactured by Nikkaki) and a CX-1 personal computer (manufactured by Canon) for outputting number distribution and volume distribution are connected. As an electrolytic solution, an about 1% Nacl aqueous solution is prepared using first-grade sodium chloride. For example ISOTON
II (Made by Coulter Scientific Japan)
Can be used. As the measuring method, the above-mentioned electrolytic aqueous solution 100
0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) as a dispersant is added to 150 ml of water, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and the Coulter counter TA-II type is used to use a 10 μ aperture as an aperture to measure particles of 2 to 40 μ based on the number. The particle size distribution is measured and then the value according to the invention is determined.

Coefficient of variation A in the number distribution of toner particles
Is calculated from the following formula.

Coefficient of variation A = [S / D ₁ ] × 100 [wherein S represents a standard deviation value in the number distribution of toner particles, and D ₁ represents the number average particle diameter (μm) of the toner particles.
The low softening point substance used in the present invention has a softening point of 4
Those having 0 to 150 ° are preferable, and further, AST
A compound having a main component maximum peak value in the DSC curve measured according to MD3418-8 of 40 to 90 ° C. is preferable. If the maximum peak is less than 40 ° C., the self-aggregating force of the low softening point substance becomes weak, and as a result, the high temperature offset resistance becomes weak, which is not preferable. On the other hand, the maximum peak is 90
When the temperature exceeds ℃, the fixing temperature becomes high, and it becomes difficult to properly smooth the surface of the fixed image, which is not preferable from the viewpoint of deterioration of color mixture. Further, when a toner is obtained by a direct polymerization method, granulation and polymerization are carried out in an aqueous medium, so that if the temperature of the maximum peak value is high, a substance having a low softening point mainly precipitates during granulation, which is not preferable.

For measuring the temperature of the maximum peak value of the low softening point substance, for example, Perkin Elmer DSC-7 is used. The melting point of indium and zinc is used to correct the temperature of the device detection unit, and the heat of fusion of indium is used to correct the amount of heat. For the sample, an aluminum pan was used and an empty pan was set as a control, and the temperature rising rate was 10 ° C./min. Measure with.

Paraffin wax as a low softening point substance,
Examples thereof include polyolefin waxes, Fischer-Tropish waxes, amide waxes, higher fatty acids, ester waxes and derivatives thereof (for example, graft compounds or block compounds thereof).

Further, as the toner to be mounted on the full-color copying machine, it is necessary that the color toners are sufficiently mixed in the fixing step, which improves the color reproducibility and OH.
The transparency of the P image is important, and it is generally preferable to use a sharp melt and low molecular weight resin for the color toner as compared with the black toner. For a normal black toner, a release agent having a relatively high crystallinity such as polyethylene wax or polypropylene wax is used in order to improve the high temperature offset property at the time of fixing. However, in a full-color toner, due to the crystallinity of this release agent, O
The transparency of the HP toner image is impaired when output.
Therefore, the high temperature offset resistance is eventually improved by uniformly applying silicone oil or the like to the heat fixing roller without adding a release agent as a color toner constituent. However, since the transfer material having the toner-fixed image thus obtained has extra silicone oil or the like adhered to the surface thereof, it causes unpleasant feeling when used by the user, which is not preferable.

Therefore, as the low softening point substance, OH
An ester wax having one or more (preferably two or more) long-chain alkyl groups having 10 or more (preferably 18 or more) carbon atoms, which does not impair the transparency of P and has high-temperature offset resistance, is preferable. In particular, an ester wax having at least one long-chain alkyl ester moiety having 10 or more carbon atoms represented by the following general structural formula is preferable in the present invention.
Structural formulas of typical compounds of specific ester waxes preferable in the present invention are shown below as general structural formulas, general structural formulas and general structural formulas.

<General Structural Formula of Ester Wax>

[0042]

[Outside 5] [In the formula, a and b represent an integer of 0 to 4, a + b is 4, R ₁ and R ₂ represent an organic group having 1 to 40 carbon atoms, and the number of carbon atoms of R ₁ and R ₂ is A group having a difference of 10 or more is shown, n and m are integers of 0 to 15, and n and m are not 0 at the same time. ]

<General Structural Formula of Ester Wax>

[0044]

[Outside 6] Wherein, a and b is an integer of 0 to 4, a + b is 4, R ₁ represents an organic group having a carbon number of 1 to 40, n and m represents an integer of 0 to 15, n And m cannot be 0 at the same time. ]

<General Structural Formula of Ester Wax>

[0046]

[Outside 7] [In the formula, a and b represent an integer of 0 to 3, a + b is 3, R ₁ and R ₂ represent an organic group having 1 to 40 carbon atoms, and the number of carbon atoms of R ₁ and R ₂ is R ₃ represents a group having a difference of 10 or more, R ₃ represents an organic group having a carbon number of 1 or more, and n and m
Represents an integer of 0 to 15, and n and m are never 0 at the same time. ]

<General Structural Formula of Ester Wax> R ₁ —COO—R ₂ [wherein R ₁ and R ₂ represent an organic group having 10 to 40 carbon atoms]. ]

The ester wax preferably used in the present invention preferably has a hardness of 0.5 to 5.0.
The hardness of the ester wax is 20 mmφ in diameter and 5 in thickness.
It is a value obtained by measuring the Vickers hardness using, for example, a dynamic ultra-micro hardness meter (DUH-200) manufactured by Shimadzu Corporation after manufacturing a sample having a cylindrical shape of mm. The measurement conditions are
Vickers hardness is obtained by displacing 10 μm under a condition of a load rate of 9.67 mm / sec with a load of 0.5 g and holding it for 15 seconds, measuring the obtained dent shape. A substance having a low softening point with a hardness of less than 0.5 increases pressure dependency and process speed dependency of the fixing device, and the high temperature offset effect is apt to be insufficiently expressed. Since the mold release agent itself has poor property and the self-cohesive force of the release agent itself is small, the high temperature offset is likely to be insufficient. Specific compounds include the following compounds.

[0049]

[Outside 8]

[0050]

[Outside 9]

In recent years, the need for full-color dual-screen images has also increased, and when forming a double-sided image, the transfer paper having the toner image formed on the front side first forms the image on the back side. Since the toner passes through the heating portion of the fixing device again, it is necessary to more fully consider the high temperature offset property of the toner. Therefore, in the present invention, it is important to add a low softening point substance. Specifically, the low softening point substance is preferably added to the toner in an amount of 5 to 30% by weight. If it is added in an amount of less than 5% by weight, the high temperature offset resistance is lowered, and further, the image on the back surface tends to show an offset phenomenon during the fixing of a double-sided image. If it exceeds 30% by weight, during the production of the toner, for example, the fusion of the toner is likely to occur in the apparatus during the production by the pulverization method, and the toner particles are likely to coalesce during the granulation during the production by the polymerization method. Those with a wide particle size distribution are easy to generate.

The method for producing the toner of the present invention includes:
Resin, mold release agent consisting of low softening point substance, colorant, charge control agent, etc. are evenly dispersed using a pressure kneader, extruder or media disperser, and then mechanically or in a jet stream to collide with a target. After finely pulverizing to a desired toner particle size (if necessary, a step of smoothing and spheroidizing the toner particles is added), a classification process is further performed to sharpen the particle size distribution to obtain a toner by a pulverizing method. In addition to the manufacturing method, a method described in JP-B-56-13945 and the like, in which a molten mixture is atomized into the air using a disk or a multi-fluid nozzle to obtain spherical toner, and JP-B-36-10
No. 231, JP-A-59-53856, and JP-A-59-61842, a method of directly producing a toner using the suspension polymerization method, and JP-A-62-1
No. 06473 and JP-A No. 63-186253, an interfacial coagulation method of aggregating at least one kind of fine particles to obtain particles having a desired particle size, soluble in a monomer A dispersion polymerization method in which the resulting polymer directly produces a toner using an insoluble aqueous organic solvent, or an emulsion polymerization method represented by a soap-free polymerization method in which a toner is produced by directly polymerizing in the presence of a water-soluble polar polymerization initiator. It is possible to produce a toner using it.

In the method of producing a toner using the pulverization method, it is difficult to set the shape factor SF-1 of the toner measured by Luzex within the range of 111 to 160. In the melt spray method, SF- Even if 1 value can be set within a predetermined range, the particle size distribution of the obtained toner tends to be wide. On the other hand, in the dispersion polymerization method, the obtained toner shows an extremely sharp particle size distribution, but the selection of materials to be used is narrow and the use of organic solvents is not suitable for production equipment from the viewpoint of waste solvent treatment and solvent flammability. It is complicated and easily complicated. The emulsion polymerization method typified by soap-free polymerization is effective because the particle size distribution of the toner is relatively uniform, but when the emulsifier or polymerization initiator end used is present on the surface of the toner particle, the environmental characteristics are likely to be deteriorated.

In the present invention, the toner shape factor SF-
The emulsion polymerization method or suspension polymerization method under normal pressure or under pressure can control the value of 1 to 111 to 160, and relatively easily obtains a fine particle toner having a sharp particle size distribution and a particle size of 4 to 8 μm. Using a preformed polymer with a medium, or by directly colliding the polymer with a pressure collision plate, or by freezing the obtained polymer in a water system, salt breakage or reverse PH particles with surface charge
A coagulation method of coalescing, aggregating and coalescing by taking into consideration such conditions as above is particularly preferable. Furthermore, a seed polymerization method in which a monomer is further adsorbed on the obtained polymer particles and then the resultant is polymerized using a polymerization initiator can also be suitably used in the present invention.

A more preferable toner used in the present invention is the toner shape factor SF-1 measured by Luzex.
Is 100 to 150 (more preferably 100 to 125,
More preferably, it is 100 to 110), contains 5 to 30% by weight of a low softening point substance, and further, the low softening point substance is an outer shell by a method for measuring a tomographic plane of toner particles using a transmission electron microscope (TEM). It has a core-shell structure encapsulated with a resin layer. Such toners can be produced directly by the suspension polymerization method.

From the viewpoint of fixability, it is necessary to include a large amount of the low softening point substance in the toner, so that it is necessary to encapsulate the low softening point substance in the outer shell resin. The toner that cannot be encapsulated cannot be sufficiently pulverized unless special freeze pulverization is used in the pulverization process, and as a result, only a wide particle size distribution can be obtained, and toner fusion to the device also occurs. Not preferable. In freeze-grinding, the device becomes complicated due to measures for preventing dew condensation on the device, and if the toner absorbs moisture, the workability of the toner is deteriorated, and it is necessary to add a drying step, which is a problem. As a specific method for encapsulating the low softening point substance, the polarity of the material in the aqueous medium is set to be smaller for the low softening point substance than the main monomer, and a small amount of a resin or monomer having a large polarity is used. By adding the above, it is possible to obtain a toner having a core-shell structure in which a substance having a low softening point is coated with an outer shell resin. Toner particle size distribution control and particle size control are carried out by changing the type and amount of the sparingly water-soluble inorganic salt or dispersant that acts as a protective colloid, and mechanical device conditions (for example, rotor peripheral speed, pass circuit, stirring). A predetermined toner can be obtained by controlling the stirring conditions such as the blade shape and the container shape) or the solid content concentration in the aqueous solution.

As a specific method for measuring the tomographic plane of the toner in the present invention, the toner particles are sufficiently dispersed in an epoxy resin which is curable at room temperature, and then 2
After curing the cured product obtained by curing for a day with ruthenium tetroxide and optionally osmium tetroxide in combination,
A flaky sample is cut out using a microtome equipped with diamond teeth, and the tomographic morphology of the toner is measured using a transmission electron microscope (TEM). In the present invention, it is preferable to use the ruthenium tetroxide dyeing method in order to make a contrast between materials by utilizing a slight difference in crystallinity between the low softening point substance used and the resin constituting the outer shell. A typical example is shown in FIGS. 2-1 and 2-2. It was observed that in the toner particles obtained in the examples described later, the low softening point substance was encapsulated by the outer shell resin.

As the binder resin used in the present invention, generally used styrene- (meth) acrylic copolymers, polyester resins, epoxy resins and styrene-butadiene copolymers can be used. In the method of directly obtaining toner particles by a polymerization method, those monomers are preferably used. Specifically, styrene; o
Styrene-based monomers such as (m-, p-)-methylstyrene and m (p-)-ethylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, (meth ) Butyl acrylate, octyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth)
(Meth) acrylic acid ester type monomers such as dimethylaminoethyl acrylate and diethylaminoethyl (meth) acrylate; vinyl type monomers such as butadiene, isoprene, cyclohexene, (meth) acrylonitrile and acrylic acid amide are preferably used. To be These may be used alone or generally in the publication Polymer Handbook Second Edition III-P 139-192 (John Wiley & S.
ons company) has a theoretical glass temperature (Tg) of 40
The monomers are appropriately mixed and used so that the temperature is up to 75 ° C.
When the theoretical glass transition temperature is lower than 40 ° C., the storage stability of the toner and the durability stability of the toner are liable to be lowered, while when the theoretical glass transition temperature is higher than 75 ° C., the fixing point of the toner is increased, and particularly in the case of full-color image formation. In this case, the color mixing of the toners of the respective colors is likely to be insufficient, the color reproducibility is poor, and the transparency of the OHP image is easily deteriorated, which is not preferable.

The molecular weight of the binder resin is measured by gel permeation chromatography (GPC). In the case of toner having a core-shell structure, specific GPC
The toner can be extracted by using a Soxhlet extractor with a toluene solvent for 20 hours in advance, and then the toluene is distilled off with a rotary evaporator to obtain an extract. The low softening point substance is dissolved but the outer shell is dissolved. An organic solvent that does not dissolve the resin (for example, chloroform) is added to the extract, and the extract is thoroughly washed.
A sample (THF solution) obtained by filtering the solution dissolved in HF) with a solvent-resistant membrane filter having a pore size of 0.3 μm was used at 150 ° C. manufactured by Waters, and the column configuration was A-801, 802, 803 manufactured by Showa Denko. 804, 80
5,806,807 can be connected and a molecular weight distribution can be measured using the calibration curve of a standard polystyrene resin. The number average molecular weight (Mn) of the obtained resin component is 5000 to 1,000,0.
An outer shell resin having a weight average molecular weight (Mw) and a number average molecular weight (Mn) (Mw / Mn) of 2 to 100 is preferred for the present invention.

In the present invention, it is particularly preferable to further add a polar resin in order to encapsulate the low softening point substance in the outer shell. As the polar resin used in the present invention, a copolymer of styrene and (meth) acrylic acid, a maleic acid copolymer, an unsaturated polyester resin, a saturated polyester resin or an epoxy resin is preferably used. It is particularly preferable that the polar resin does not contain an unsaturated group capable of reacting with the shell resin or the vinyl monomer in the molecule. In the case of containing a polar resin having an unsaturated group, a cross-linking reaction occurs with the vinyl-based monomer forming the outer shell resin layer, resulting in an extremely high molecular weight for a full-color toner, which is not suitable for mixing four color toners. It is disadvantageous and not preferable.

The colorants used in the present invention include the following yellow colorants, magenta colorants and cyan colorants. Black colorants include carbon black, magnetic substances or the following yellow / magenta / cyan colorants. The one toned in black is used.

As the yellow colorant, condensed azo compounds, isoindolinone compounds, anthraquinone compounds,
A compound represented by an azo metal complex, a methine compound and an allylamide compound is used. Specifically, C.I. I. Pigment Yellow 12, 13, 14, 15, 17, 6
2, 74, 83, 93, 94, 95, 109, 110,
111, 128, 129, 147, 168 and 180 are preferably used.

As the magenta colorant, a condensed azo compound, a diketopyrrolopyrrole compound, an anthraquinone, a quinacridone compound, a basic dye lake compound, a naphthol compound, a benzimidazolone compound, a thioindigo compound and a perylene compound are used. Specifically, C.I.
I. Pigment Red 2, 3, 5, 6, 7, 23, 4
8; 2, 48; 3, 48, 4, 57; 1, 81; 1,
144, 146, 166, 169, 177, 184, 1
85, 202, 206, 220, 221, 254 are particularly preferred.

As the cyan colorant, a copper phthalocyanine compound and its derivative, an anthraquinone compound, a basic dye lake compound and the like can be used. Specifically, C.I. I.
Pigment Blue 1, 7, 15, 15: 1, 15: 2,
15: 3, 15: 4, 60, 62, 66 can be used particularly preferably.

These colorants can be used alone or in the form of a mixture, or in the state of a solid solution. The colorant is a hue,
It is appropriately selected in terms of saturation, brightness, weather resistance, OHP transparency, and dispersibility in the toner. The amount of the colorant added is preferably 1 to 20 parts by weight based on 100 parts by weight of the resin.

When a magnetic substance is used as the black colorant, unlike other colorants, it is preferably used by adding 40 to 150 parts by weight to 100 parts by weight of the resin.

The charge control agent used in the present invention includes
Known ones can be used. A charge control agent that is colorless and has a high charging speed of the toner and can stably maintain a constant charge amount is preferable. Further, when a direct polymerization method is used as a method for producing a toner, a charge control agent having no polymerization inhibitory property and having no solubilized product in an aqueous medium is particularly preferable. As specific compounds, salicylic acid as a negative charge control agent, alkylsalicylic acid, dialkylsalicylic acid, naphthoic acid, metal compounds of dicarboxylic acid, sulfonic acid, a polymeric compound having a carboxylic acid side chain, a boron compound,
Examples thereof include urea compounds, silicon compounds and currys arenes. Further, examples of the positive charge control agent include a quaternary ammonium salt, a polymer type compound having the quaternary ammonium salt in its side chain, a guanidine compound, an imidazole compound, and the like. The charge control agent is preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the resin. However, the addition of the charge control agent is not essential in the present invention, and when the two-component developing method is used, triboelectric charging with the carrier is used, or when the non-magnetic one-component blade coating developing method is used. By positively utilizing the triboelectrification with the blade member or the sleeve member, it is not always necessary to include the charge control agent in the toner.

When the direct polymerization method is used as the method for producing the toner particles, the polymerization initiator is, for example, 2,
2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,
Azo- or azo-azo polymerization initiators such as 1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile; benzoyl Peroxide-based polymerization initiators such as peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide are used. The amount of the polymerization initiator added varies depending on the intended degree of polymerization, but is generally 0.5 to 20% by weight with respect to the monomer.
It is added and used. Although the type of the polymerization initiator varies slightly depending on the polymerization method, it may be used alone or in combination with reference to the 10-hour half-life temperature.

To control the degree of polymerization, known crosslinking agents, chain transfer agents, polymerization inhibitors and the like may be further added and used.

When a suspension polymerization method using a dispersion stabilizer is used as a method for producing toner particles, the dispersion stabilizer used is an inorganic compound such as tricalcium phosphate, magnesium phosphate, aluminum phosphate or zinc phosphate. , Calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, silica, alumina and the like. As an organic dispersion stabilizer, polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose,
Examples thereof include sodium salts of ethyl cellulose, carboxymethyl cellulose, polyacrylic acid and its salts, starch and the like. These can be used by dispersing them in the aqueous phase. It is preferable to use 0.2 to 20 parts by weight of these dispersion stabilizers per 100 parts by weight of the polymerizable monomer.

When an inorganic compound is used as the dispersion stabilizer, a commercially available one may be used as it is, but fine particles of the inorganic compound may be generated in a dispersion medium in order to obtain fine particles. For example, in the case of tricalcium phosphate,
It is advisable to mix the aqueous sodium phosphate solution and the aqueous calcium chloride solution under high stirring.

For fine dispersion of these dispersion stabilizers,
0.001-0.1 parts by weight of surfactant may be used. This is for promoting the intended action of the above dispersion stabilizer, and for example, sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, potassium stearate. ,
Examples thereof include calcium oleate.

When the direct polymerization method is used as the method for producing the toner used in the present invention, the following production methods are possible.

A releasing agent, a colorant, a charge control agent, a polymerization initiator and other additives consisting of a low softening point substance are added to the polymerizable monomer and uniformly dissolved or homogenized by a homogenizer, an ultrasonic disperser or the like. The dispersed polymerizable monomer composition is dispersed in an aqueous phase containing a dispersion stabilizer by a usual stirrer, homomixer, homogenizer or the like. Preferably, the stirring speed and stirring time are adjusted so that the droplets of the polymer monomer composition have a desired toner particle size, and granulation is performed. After that, stirring may be performed to the extent that the particle state is maintained and the particles are prevented from settling due to the action of the dispersion stabilizer. Polymerization temperature is 40 ° C or higher, generally 50 to 90 ° C
It is better to carry out the polymerization by setting the temperature to. The temperature may be raised in the latter half of the polymerization reaction, and further, in order to remove unreacted polymerizable monomers, by-products, etc. that cause odor during toner fixing, in the latter half of the reaction or after the reaction is partially completed. The aqueous medium may be distilled off. After the reaction is completed, the produced toner particles are collected by washing and filtration and dried. In the suspension polymerization method, 300 to 3 parts by weight of water is usually added to 100 parts by weight of the polymerizable monomer composition.
It is preferred to use 000 parts by weight as the dispersion medium.

The image forming method of the present invention will be described more specifically with reference to FIG.

In the apparatus system shown in FIG. 1, the developing devices 4-1, 4-2, 4-3, and 4-4 each have a developer having a cyan toner, a developer having a magenta toner, and
A developer having a yellow toner and a developer having a black toner are introduced, and the electrostatic charge image formed on the photoconductor 1 is developed by a magnetic brush development system or a non-magnetic one-component development system, and each color toner image is developed. 1 is formed on.
Photoreceptor 1 includes a-Se, CdS, ZnO ₂ , OPC, a-
A photosensitive drum or photosensitive belt having a photoconductive insulating material layer such as Si. The photoconductor 1 is rotated in the arrow direction by a driving device (not shown).

As the photosensitive member 1, a photosensitive member having an amorphous silicon photosensitive layer or an organic photosensitive layer is preferably used.

As the organic photosensitive layer, the photosensitive layer contains a charge-generating substance and a substance having a charge-transporting property in the same layer.
It may be a single layer type or a functionally separated type photosensitive layer having a charge transport layer and a charge generation layer as components. A laminated photosensitive layer having a structure in which a charge generation layer and then a charge transport layer are laminated in this order on a conductive substrate is one of preferred examples.

Polycarbonate resin, polyester resin, and acrylic resin are particularly preferable as the binder resin of the organic photosensitive layer because of good transferability and cleaning property, poor cleaning, fusing of toner to the photoreceptor, and filming of external additives. Hard to happen.

In the present invention, in the charging step, there are a method in which the corona charger is not in contact with the photosensitive member 1 and a contact type method in which a roller or the like is used. A contact type as shown in FIG. 1 is preferably used for efficient uniform charging, simplification and low ozone generation.

The charging roller 2 has a core metal bar 2b at the center and a conductive elastic layer 2a forming the outer periphery thereof as a basic structure. The charging roller 2 is pressed against the surface of the photoconductor 1 with a pressing force, and is driven to rotate as the photoconductor 1 rotates.

A preferable process condition when the charging roller is used is that the contact pressure of the roller is 5 to 500 g / c.
In m, when a DC voltage superimposed with an AC voltage is used, AC voltage = 0.5 to 5 kVpp, AC frequency = 50
Hz to 5 kHz, DC voltage = ± 0.2 to ± 1.5 kV, and when DC voltage is used, DC voltage = ± 0.2 to
± 5 kV.

As other charging means, there are a method using a charging blade and a method using a conductive brush. These contact charging means are effective in that high voltage becomes unnecessary and ozone generation is reduced.

As the material of the charging roller and the charging blade as the contact charging means, conductive rubber is preferable, and a releasing film may be provided on the surface thereof. As the releasable coating, nylon resin, PVDF (polyvinylidene fluoride), PVDC (polyvinylidene chloride), etc. can be applied.

The toner image on the photosensitive member has a voltage (for example, ±
It is transferred to the intermediate transfer member 5 to which 0.1 to ± 5 kV) is applied.

The intermediate transfer member 5 is a pipe-shaped conductive core metal 5.
b and an elastic layer 5a having a medium resistance formed on the outer peripheral surface thereof. The core metal 5b may be a plastic pipe coated with conductive plating.

The elastic layer 5a of medium resistance is made of silicone rubber,
Teflon rubber, chloroprene rubber, urethane rubber, EP
An electrical resistance value (volume resistivity) of 10 is obtained by mixing and dispersing an electroconductive material such as carbon black, zinc oxide, tin oxide, or silicon carbide in an elastic material such as DM (a terpolymer of ethylene propylene diene). ^A solid or foamed layer with a medium resistance of ⁵ to 10 ¹¹ Ω · cm.

The intermediate transfer member 5 is disposed in parallel with the photosensitive member 1 so as to be in contact with the lower surface of the photosensitive member 1, and rotates in the counterclockwise direction indicated by an arrow at the same peripheral speed as the photosensitive member 1. To do.

While the toner image of the first color formed and carried on the surface of the photoconductor 1 passes through the transfer nip portion where the photoconductor 1 and the intermediate transfer member 5 are in contact with each other, the transfer nip is applied by the transfer bias applied to the intermediate transfer member 5. Intermediate transfer is sequentially performed to the outer surface of the intermediate transfer member 5 by the electric field formed in the area.

If necessary, the removable cleaning means 10 cleans the surface of the intermediate transfer member 5 after the toner image is transferred onto the transfer material. When there is a toner image on the intermediate transfer body, the cleaning unit 10 is separated from the surface of the intermediate transfer body so as not to disturb the toner image.

A transfer means is arranged in parallel with the intermediate transfer body 5 so as to be in contact with the lower surface of the intermediate transfer body 5, and the transfer means is, for example, the transfer roller 7, and has the same circumference as the intermediate transfer body 5. Rotate clockwise at the speed indicated by the arrow. The transfer roller 7 may be arranged so as to be in direct contact with the intermediate transfer body 5, and a belt or the like may be provided so that the intermediate transfer body 5 and the transfer roller 7 are connected.
It may be arranged so as to come into contact with.

The transfer roller 7 has a basic core metal 7b and a conductive elastic layer 7a formed on the outer periphery thereof.

For the intermediate transfer member and the transfer roller used in the present invention, general materials can be used. In the present invention, the voltage applied to the transfer roller can be reduced by setting the volume specific resistance value of the elastic layer of the transfer roller to be smaller than the volume specific resistance value of the elastic layer of the intermediate transfer member, so that it is possible to reduce the voltage on the transfer material. It is possible to form a toner image and prevent winding of the transfer material around the intermediate transfer member.
Particularly, it is particularly preferable that the volume resistivity of the elastic layer of the intermediate transfer body is 10 times or more than the volume resistivity of the elastic layer of the transfer roller.

The hardness of the intermediate transfer member and the transfer roller is JI.
It is measured according to SK-6301. The intermediate transfer member used in the present invention is preferably composed of an elastic layer belonging to the range of 10 to 40 degrees, while the hardness of the elastic layer of the transfer roller is higher than that of the elastic layer of the intermediate transfer member.
Those having a value of -80 degrees are preferable in order to prevent the transfer material from winding around the intermediate transfer member. When the hardness of the intermediate transfer body and that of the transfer roller are opposite, a recess is formed on the transfer roller side, and the transfer material is likely to be wound around the intermediate transfer body.

The transfer roller 7 is rotated at a constant speed or a peripheral speed different from that of the intermediate transfer member 5. The transfer material 6 is conveyed between the intermediate transfer body 5 and the transfer roller 7, and at the same time, a bias having a polarity opposite to the frictional charge of the toner is applied to the transfer roller 7 from the transfer bias means. Toner image is transferred to the surface side of the transfer material 6.

The same material as the charging roller can be used as the material of the transfer rotator, and the contact pressure of the roller is 5 to 500 g as a preferable transfer process condition.
/ Cm, the DC voltage is ± 0.2 to ± 10 kV.

For example, the conductive elastic layer 7b of the transfer roller 7
Is a polyurethane in which a conductive material such as carbon is dispersed, an ethylene-propylene-diene terpolymer (EPDM)
It is made of an elastic body having a volume resistance of about 10 ⁶ to 10 ¹⁰ Ωcm. A bias is applied to the cored bar 7a by a constant voltage power source. Bias conditions are ± 0.2 to ±
10 kV is preferred.

Next, the transfer material 6 is conveyed to a fixing device 11 which is basically composed of a heating roller containing a heating element such as a halogen heater and an elastic pressure roller pressed against the heating roller by a pressing force, and heated. The toner image is heated and pressed and fixed on the transfer material by passing between the roller and the pressure roller.
Alternatively, a method of fixing with a heater through a film may be used.

[0099]

EXAMPLES The present invention will be described more specifically by showing examples below.

Example 1 FIG. 1 is a sectional view of an image forming apparatus used in Example 1. The photoconductor 1 has a photoconductive layer 1b having an organic photo-semiconductor on a substrate 1a, and is rotated by a charging roller 2 (conductive elastic layer 2a, core metal 2b) that rotates in the direction of an arrow and rotates in opposition to and in contact with the photoconductor. 1 is charged to a surface potential of about -600V.
The exposure 3 is turned on and off according to digital image information on the photoconductor by the polygon mirror, so that the potential of the exposure portion is-.
An electrostatic charge image having a potential of 100 V and a dark area potential of −600 V is formed. A yellow toner, a magenta toner, a cyan toner, or a black toner was used on the photoconductor 1 using a plurality of developing devices 4-1, 4-2, 4-3, and 4-4 to obtain a toner image by the reversal development method. The toner image is formed on the intermediate transfer member 5 for each color.
A color-superimposed color image of four colors is formed on the intermediate transfer body 5 by being transferred onto the (elastic layer 5a and the core metal 5b as a support). The transfer material toner on the photoconductor 1 is collected in the residual toner container 9 by the cleaner member 8.

SF-1 is 111 to 160, and SF-1
-2 is 110 to 140, and the toner having a shape of SF-2 / SF-1 value of 1 or less has a high transfer efficiency by the ordinary irregular toner, and therefore, in a system without a simple bias roller or cleaner member. Is less likely to cause problems. The intermediate transfer member 5 includes a pipe-shaped core metal 5b on which a carbon black conductivity-imparting member is formed by a nitrile-butadiene rubber (NB).
R) was coated with an elastic layer 5b sufficiently dispersed therein. The hardness of the coat layer 5b is 30 degrees according to JIS K-6301, and the volume resistivity is 10 ⁹ Ω · cm.
Met. The transfer current required for transfer from the photoconductor 1 to the intermediate transfer member 5 is about 5 μA, which is +500 V from the power supply.
Was obtained on the core metal 5b. Intermediate transfer member 5
After transferring the toner from the transfer material 6 to the transfer material 6, the intermediate transfer surface may be cleaned by the cleaner member 10. Diameter 20mm
The transfer roller 7 is produced by coating a core metal 7b having a diameter of 10 mm with a carbon conductivity imparting member sufficiently dispersed in a foam of ethylene-propylene-diene terpolymer (EPDM). The elastic layer 7a has a volume resistivity value of 10 ⁶ Ω · cm.
The JIS K-6301 standard hardness used was 35 degrees. Apply a voltage to the transfer roller 15
A μA transcription Tenryu was washed away. As for the contaminated toner on the transfer roller 7 when the toner is collectively transferred from the intermediate transfer member 5 to the transfer material 6, a fur brush cleaner or a cleaning member-less system is generally used as a cleaning member. Form factor SF-1 of 111-
160, SF-2 110-140, SF-1
By setting the value of / SF-2 to 1 or less, a cleaning member-less system could be adopted because of high transfer efficiency.

The cyan toner used in this example was prepared as follows. Into a 2-liter four-necked flask equipped with a high-speed stirring device TK-Homomixer, ion-exchanged water 71
0 parts by weight and 450 parts by weight of 0.1 mol / liter-Na ₃ PO ₄ aqueous solution were added to adjust the rotation speed to 12000 rpm, and the mixture was heated to 65 ° C. 68 parts by weight of 1.0 mol / liter-CaCl ₂ aqueous solution was gradually added to prepare an aqueous dispersion medium containing a minute sparingly water-soluble dispersion stabilizer Ca ₃ (PO ₄ ) ₂ . On the other hand, the dispersoid system includes: styrene monomer 165 parts by weight n-butyl acrylate monomer 35 parts by weight cyan colorant (CI Pigment Blue 15: 3)
14 parts by weight Polar resin [Saturated polyester (terephthalic acid-propylene oxide modified bisphenol A, acid value 15, peak molecular weight 6000)] 10 parts by weight Negative charge control agent (dialkyl salicylate metal compound)
2 parts by weight Low softening point substance [ester wax compound (1)] 60
Parts by weight (peak temperature in DSC 59.4 ° C, Vickers hardness 1.5)

The above mixture was dispersed in an attritor for 3 hours, and then 10 parts by weight of 2,2'-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator was added to the polymerizable monomer composition. Was put into an aqueous dispersion medium, and granulation was carried out for 15 minutes while maintaining the rotation speed at 12000 rpm.
After that, the stirrer was changed from the high speed stirrer to the propeller stirrer, the internal temperature was raised to 80 ° C., and the polymerization was continued at 50 rpm for 10 hours. The suspension obtained immediately after the polymerization was heated to 65 ° C.
The temperature of the suspension was controlled, and the suspension was subjected to pressure collision indetermination three times at a discharge pressure of 720 kg / cm ² by using a piston type high pressure homogenizer to indeterminate the toner particles. Then, diluted hydrochloric acid was added to remove the dispersion stabilizer. Further washed and dried to obtain an electrically insulating cyan toner having a weight average diameter of 6.5 μm, a coefficient of variation in number distribution of 29%, SF-1 of 142, and SF-2 of 136. It was Fig. 2 shows a schematic diagram of the tomographic photograph of the obtained cyan toner.
It is shown in FIG. The structure showed that the ester wax compound (1), which is a low softening point substance, was covered with the outer shell resin (Mw 70,000, Mn 20,000). 2 wt% of hydrophobic titanium oxide fine particles were externally added to the obtained cyan toner to obtain a cyan toner having excellent fluidity. A two-component developer was prepared by mixing 6 parts by weight of the obtained cyan toner with 94 parts by weight of a resin-coated magnetic ferrite carrier having an average particle size of 50 μm. Further, a colorant is C.I. I. Pigment Yellow 17, C.I. I. Pigment Red 202 and graft carbon black were used to obtain an electrically insulating yellow toner, an electrically insulating magenta toner and an electrically insulating black toner by the same method. The physical properties of each color toner are shown in the table below.

[0104]

[Table 1]

2 wt% of the obtained yellow toner, magenta toner and black toner and hydrophobic titanium oxide fine particles
Were mixed with each other, and the resin-coated magnetic ferrite carrier was further mixed to prepare a two-component developer.

The prepared two-component type developer of each color was applied to the developing units 4-1, 4-2, 4-3 and 4-4 shown in FIG. 1, respectively.
And a toner image of each color toner was formed under the above-mentioned image forming conditions by the magnetic brush development method. The toner of each color toner image had a triboelectric charge amount of −15 to −18 μc / g. The toner images of the respective colors are sequentially transferred from the photosensitive member 1 to the intermediate transfer member 5, and the four color toner images on the intermediate transfer member 5 are transferred to a transfer material (plain paper) having a basis weight of 199 g / m ² , and then transferred onto the transfer material. The four-color toner images of No. 3 were heat-fixed by the heat-pressure fixing unit 11.

After the toner image was transferred from the intermediate transfer member 5 to the transfer material, the intermediate transfer member 5 was cleaned by the sequential cleaning means 10.

At this time, the transfer efficiency of each color toner from the photoconductor 1 to the intermediate transfer member 5 is 94% to 98%, and the transfer efficiency from the intermediate transfer 5 to the transfer material 6 is 99%. The transfer efficiency was as high as% -97%.

A high-quality image having excellent color mixture and no voids was obtained. Further, double-sided images were formed, but no offset was observed on both the front and back surfaces of the transfer material. An endurance test of 50,000 sheets was also conducted, but there was no change in the image density between the initial stage and the end stage, and no toner fusion to each member was observed.

Example 2 Using the image forming apparatus of Example 1, each color toner was prepared as follows.

Styrene n-butyl acrylate copolymer 200 parts by weight Cyan colorant (CI Pigment Blue 15: 3)
14 parts by weight Polar resin [polyester (terephthalic acid-propylene oxide-modified bisphenol A, acid value 15, peak molecular weight 60000)] 10 parts by weight Negative charge control agent (dialkyl salicylate metal compound)
2 parts by weight Low softening point substance (polyester wax compound (1))
15 parts by weight

After sufficiently melting and kneading the above composition using an extruder, the cooled kneaded material is mechanically coarsely pulverized, and the coarsely pulverized product jet stream is used to collide with a collision plate to finely pulverize the composition.
Further, the finely pulverized product was classified by an air flow classifier using the Counder effect, and the weight average diameter was 8.2 μm, and the number variation coefficient was 3
A 0% amorphous cyan toner was obtained. After mixing this irregular-shaped cyan toner and commercially available calcium phosphate fine powder with a Henschel mixer, the obtained mixed powder is put into a container containing water and further dispersed in water using a homomixer to gradually raise the water temperature. The mixture was warmed and heat-treated at a temperature of 60 ° C. for 2 hours. Then, dilute hydrochloric acid was added to the container to sufficiently dissolve the calcium phosphate on the surface of the cyan toner particles. The cyan toner was separated by filtration, washed, dried, and then passed through a 400-mesh sieve to remove aggregates to obtain a cyan toner. The obtained cyan toner has a shape factor SF-1 as observed by an electron microscope.
Is 134, SF-2 is 128, and the weight average diameter of the electrically insulating cyan toner is 7.9.
The number variation coefficient was 29% in μm. Using the colorant of Example 1, SF-1 gives 131 to 14 in the same manner as above.
1, and the ratio of SF-1 / SF-2 is 0.80 to 0.9.
The electrically insulating yellow toner, the electrically insulating magenta toner, and the electrically insulating black toner which are No. 6 were obtained. In the toner tomographic observation, the ester wax compound (1) was not encapsulated as shown in FIG. Table 2 shows the physical properties of the obtained color toners.

[0113]

[Table 2]

When the obtained toners of respective colors were subjected to image formation by the image forming apparatus described in Example 1, a high quality image having excellent color mixture and no voids was obtained. The initial image showed 1.6 in the 50,000-sheet durability test, but the image density after the durability test was
Although the density was slightly decreased to 1.5, it was at a practically acceptable level. At this time, the photoconductor 1 to the intermediate transfer body 5
The transfer efficiency from the intermediate transfer member 5 to the transfer material 6 is 97%, and the total transfer efficiency is 91% to 96%.
The transfer efficiency was as high as% -93%.

Example 3 Styrene monomer 165 parts by weight n-butyl acrylate monomer 35 parts by weight CI Pigment Blue 15: 3 14 parts by weight Saturated polyester (terephthalic acid-propion oxide modified bisphenol A, acid value 15, peak molecular weight) 6
000) 10 parts by weight Dialkyl salicylate metal compound 2 parts by weight Compound (5) 60 parts by weight

The above mixture was dispersed for 3 hours using an attritor, and then the dispersion prepared by adding 10 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was added to 1200 parts by weight of water polyacrylic acid. Pour into an aqueous solution mixed with 15 parts by weight of sodium, and use a TK homomixer for 12
The mixture was stirred at 000 rpm and granulated for 25 minutes. After that, the stirrer was changed from the high speed stirrer to the propeller stirrer, the internal temperature was raised to 75 ° C., and the polymerization was continued at 80 rpm for 10 hours. After the completion of the weighting, the weight average diameter of the suspended particles measured with a Coulter counter was 1 μm. The pH of this suspension was adjusted to 4.5 while maintaining stirring, the temperature was adjusted to 85 ° C., and this temperature was maintained for 8 hours for association. Then, it was cooled, washed with water, and dried to obtain a cyan toner of the interface association method. The weight average diameter of the obtained toner is 7.3 μm, the number variation coefficient is 28%, SF-1 is 144, SF-2 is 115, and SF-2 / SF-1 is 0. A cyan toner of 80 was prepared. When the cross section of the toner particles was observed, it had a form as shown in FIG.
Similarly, SF-1 is 138 to 153, and SF-
2 is 110 to 132, and SF-2 / SF-1 is 0.
A yellow toner, a magenta toner and a black toner having a weight ratio of 80 to 0.86 were prepared.

An image drawing test was conducted in the same manner as in Example 1, and good results were obtained.

Comparative Example 1 The image forming apparatus used in Example 1 was used to form an image using the following toner.

Styrene-n-butyl acrylate copolymer (Mw 70,000, Mn 20,000) 200 parts by weight Cyan colorant (CI Pigment Blue 15: 3)
14 parts by weight Polar resin [Saturated polyester (terephthalic acid-propylene oxide-modified bisphenol A, acid value 15, peak molecular weight 60000)] 10 parts by weight Negative charge control agent (dialkyl salicylate metal compound)
2 parts by weight Low softening point substance [ester wax compound (1)] 15
Parts by weight

After sufficiently melting and kneading the above composition using an extruder, the cooled kneaded product is mechanically coarsely pulverized, and the coarsely pulverized product is collided with a collision plate using a jet flow to finely pulverize, and further the Counder effect. Airflow classifier using pulverized material was classified to have a weight average of 7.8 μm and a coefficient of number variation of 3
8%, SF-1 is 172, SF-2 is 17
An amorphous cyan toner of No. 5 was obtained. Similarly, C.I. I. Pigment Yellow 17, C.I. I. Pigment Red 202 or graft carbon black,
Yellow toner, magenta toner, and black toner were obtained. Table 3 shows the physical properties of the obtained toners of the respective colors.

[0121]

[Table 3]

When images were printed in the same manner as in Example 1, the transfer rate from the photosensitive member 1 to the intermediate transfer member 5 was 82% to 8%.
7%, the transfer rate from the intermediate transfer body 5 to the transfer material 6 is 81%.
Therefore, the total transfer efficiency was 66.4 to 70%, and the toner utilization efficiency was considerably low. Further, in the double-sided fixed image, offset occurred in the back side image. Even in the 50,000-sheet durability test, the initial image density was only 1.06, and the image density after the durability test was 0.85, showing a decrease in density.

Comparative Example 2 Commercially available full-color copying machine (CLC without using intermediate transfer member)
-500), an image forming test was conducted using the four color toners used in Example 1. In the case of a transfer paper having a basis weight of 105 g / m ^2, the transfer paper is adsorbed on the surface of the transfer drum by using an auxiliary means such as a gripper, toner is sequentially transferred onto the transfer paper four times, and the four-color toner image on the transfer paper is heated. When fixing with a pressure roller, a high-quality full-color image could be obtained.

However, in the case of a transfer paper having a basis weight of 199 g / m ² , partial non-uniform transfer failure is caused due to unevenness of the transfer paper and the transfer paper is not adsorbed to the transfer drum. The trailing edge of the paper caused improper adsorption to the transfer drum, resulting in improper transfer.

Comparative Example 3 Amorphous toners of various colors were produced by the pulverization method in the same manner as in Comparative Example 1 except that the addition amount of the ester wax compound (1) was changed to 4% by weight. The shape factor (SF-1) of the obtained toner is 162 to 165, and the weight average diameter is 8
.About.9 .mu.m. When images were printed in the same manner as in Example 1, the transfer efficiency from the photoconductor 1 to the intermediate transfer body 5 was 80 to 83%, and the transfer efficiency from the intermediate transfer body 5 to the transfer material 6 was 75. %, And the toner utilization efficiency was low at 60 to 62.3% overall.

Further, offset occurred during fixing.

Comparative Example 4 Amorphous toners of various colors were produced by the pulverization method in the same manner as in Comparative Example 1 except that the addition amount of the ester wax compound (1) was changed to 45% by weight. The shape factor (SF-1) of the obtained toner was 171 to 173, and the weight average diameter was 8.2 to 8.5 μm. When images were printed out in the same manner as in Example 1, toner fusion to the photosensitive member 1 and the intermediate transfer member 5 occurred during the endurance of a large number of sheets, and the transfer efficiency was about 45% overall, and the image was transferred. Only the one with much unevenness was obtained.

[0128]

According to the present invention, the toner particles can be transferred from the photoconductor and the intermediate photoconductor at a high transfer rate, toner fusion and filming are less likely to occur, and it is suitable for thick paper and small size transfer materials. It is possible to transfer images, has sufficient low temperature fixability, and a clear full-color image can be obtained. It is also suitable for obtaining a color OHP image having excellent transparency.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an image forming apparatus suitable for the present invention.

FIG. 2 is a schematic diagram illustrating a toner layer of Example 1.

FIG. 3 is a schematic view showing a toner layer of Example 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor (electrostatic latent image holder) 2 Charging roller 3 Exposure 4 4 color developing device (4-1, 4-2, 4-3, 4-4) 5 Intermediate transfer body 6 Transfer material 7 Transfer roller

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[Procedure amendment]

[Submission date] February 28, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0051

[Correction method] Change

[Correction content]

In recent years, the need for full-color double-sided images has been increasing, and when forming a double-sided image, the transfer paper having the toner image formed on the front side is first fixed even when the image is formed on the back side. Since the toner passes through the heating portion of the container again, it is necessary to more fully consider the high temperature offset property of the toner. Therefore, in the present invention, it is important to add a low softening point substance. Specifically, the low softening point substance is preferably added to the toner in an amount of 5 to 40% by weight. If it is added in an amount of less than 5% by weight, the high temperature offset resistance is lowered, and further, the image on the back surface tends to show an offset phenomenon during the fixing of a double-sided image. If it exceeds 40% by weight, during the production of the toner, for example, fusion of the toner is likely to occur in the apparatus in the production by the pulverization method, and even in the production by the polymerization method, coalescence of the toner particles is likely to occur during granulation, Those with a wide particle size distribution are easy to generate.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0055

[Correction method] Change

[Correction content]

A more preferable toner used in the present invention is the toner shape factor SF-1 measured by Luzex.
Is 100 to 150 (more preferably 100 to 125,
More preferably, it is 100 to 110), contains 5 to 40% by weight of a low softening point substance, and further, the low softening point substance is a shell by a tomographic surface measurement method of toner particles using a transmission electron microscope (TEM). It has a core-shell structure encapsulated with a resin layer. Such toners can be produced directly by the suspension polymerization method.

Claims (6)

[Claims] 1. A shape factor SF-1 measured by Luzex is 111 to 160, a shape factor SF-2 is 110 to 140, and SF-2 /
The value of SF-1 is 1 or less, and the low softening point substance is 5 to
A toner image is formed with 40% by weight of toner particles, the toner image on the electrostatic latent image holding member is transferred to an intermediate transfer member, the transfer means is brought into contact with the transfer material, and the toner image on the intermediate transfer member is transferred. An image forming method comprising: transferring a toner image to the transfer material; and heating and fixing the toner image on the transfer material to the transfer material by heating means. 2. The surface of the intermediate transfer body and the transfer means is composed of an elastic layer, the volume specific resistance value of the intermediate transfer body is lower than the volume specific resistance value of the transfer means, and the surface of the intermediate transfer body. Hardness is 10 according to JIS K-6301
The hardness of the transfer means is larger than that of the intermediate transfer body, and the transfer means is pressed against the intermediate transfer body to form a concave nip on the side of the intermediate transfer body. The image forming method according to claim 1, wherein the toner image is transferred onto the transfer material by applying. 3. The toner particles are formed by a transmission electron microscope (TE).
The low softening point substance is encapsulated in an outer shell resin layer by a method of measuring a tomographic plane of toner particles using M), and has a sea-island structure having at least one or more islands, and is manufactured by a direct polymerization method. The image forming method according to claim 1, wherein the toner particles are toner particles. 4. The image forming method according to claim 1, wherein the intermediate transfer member is an elastic roller having a medium resistance. 5. The image forming method according to claim 1, wherein the low softening point substance is an ester wax having at least one long chain ester moiety having 10 or more carbon atoms. 6. The image forming method according to claim 1, wherein the intermediate transfer member has a roller shape.