JPH09218542A - Liquid developer and image forming method using the same - Google Patents

Abstract

(57) Abstract: To provide a developer that is stable against temperature and process. In a developer in which colored particles having an average particle size of at least 0.1 to 2.5 μm made of a resin and a coloring material are dispersed in an insulating liquid, the insulating liquid mainly contains a hydrocarbon solvent. The hydrocarbon solvent has a boiling point range of 200 ° C. or higher and 270 ° C. or lower, and a difference in kinematic viscosity between 10 ° C. and 50 ° C. is 3
A liquid developer having a kinematic viscosity at 20 ° C. of 1 cst or more and 4 cst or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid developer, and preferably to an image forming method in which a liquid toner is supplied to an electrostatic latent image on an electrostatic latent image carrier via a developing roller to develop the image. It is used, and more preferably, the electrostatic latent image on the electrostatic latent image carrier is supplied with a liquid toner through a developing roller to develop the image, and the image visualized by this development is transferred to an intermediate transfer member. Used in an image forming method in which a full-color image is formed on the intermediate transfer member by repeating the step of electrostatically transferring while being in contact with the substrate, and the full-color image on the intermediate transfer member is re-transferred onto a transfer material. And a liquid developer used in an image forming method used in a copying machine or a laser beam printer, for example.

[0002]

2. Description of the Related Art In conventional liquid developers, a relatively low boiling point solvent such as Isopar H has been used as an insulating liquid in which toner is dispersed. However, in a full-color printer, when an attempt is made to form a full-color image by using a developer composed of such a solvent having a low boiling point, there arise problems such as a difference in viscosity depending on colors and a variation in temperature conditions. Furthermore, in the image forming method for forming a full-color image on the intermediate transfer body, it was found that the viscosity of the developer greatly affects the transferability from the electrostatic latent image carrier to the intermediate transfer body. A stable developer has been desired.

[0003]

The requirements necessary for the developer used in the image forming method as described above include the following items.

(1) There is no difference in developability between colors (2) Difference in viscosity due to temperature is small.

The present invention has been conceived in view of the above-mentioned drawbacks, and an object of the present invention is to provide a liquid developer capable of obtaining stable printed matter in a full-color printer.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
A developer in which colored particles having an average particle size of at least 0.1 to 2.5 μm composed of a resin and a colorant are dispersed in an insulating liquid, the insulating liquid containing a hydrocarbon solvent as a main component. The boiling point range of the hydrocarbon solvent is 200 ° C. or higher and 270 ° C. or lower, and the difference between the kinematic viscosity values at 10 ° C. and 50 ° C. is 3 cst or less, and at 20 ° C. This is achieved by a liquid developer having a kinematic viscosity of 1 cst or more and 4 cst or less.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The liquid developer of the present invention is such that colored particles composed of at least a resin and a colorant are dispersed in an insulating liquid containing a hydrocarbon solvent as a main component by about 0.1 to 20 wt%.

The insulating liquid used in the present invention has a volume resistivity of 10 ¹⁴ or more. Volume resistivity is 10
^If it is less than ^{14, the} electrophoretic migration of the toner in the developer is not satisfactory and the latent image cannot be sufficiently developed.

In the present invention, the insulating liquid contains a hydrocarbon solvent as a main component, and the boiling point range of the hydrocarbon solvent is from 200 ° C. to 270 ° C., preferably 2
It is 15 ° C or higher and 260 ° C or lower. The difference between the kinematic viscosity value at 10 ° C. and the value at 50 ° C. is 3 cst or less, preferably 2 cst or less. And the kinematic viscosity at 20 ℃ is 1c
st or more and 4 cst or less, preferably 1.5 cst
The above is 3.5 cst or less.

Here, when the boiling point range is less than 200 ° C., the solvent volatilizes on the electrostatic latent image bearing member, the state of the developer at the time of transfer to the intermediate transfer member changes, and the transfer becomes unstable. become.
If the temperature exceeds 280 ° C., the energy required for transfer / fixing from the intermediate transfer body to the paper becomes large, which is not preferable in terms of the apparatus configuration.

Further, when the difference between the kinematic viscosity at 10 ° C. and the value at 50 ° C. exceeds 3 cst, in the case of the image forming method in which the liquid developer is supplied through the developing roller to develop. Developability depends on the mobility of toner particles in the developer,
As a result, since it depends on the viscosity of the solvent, the temperature dependence of the kinematic viscosity is linked to the temperature dependence of the development density, which causes a problem that the printing density of the printed matter changes depending on the temperature.

If the kinematic viscosity at 20 ° C. is less than 1 cst, the developer in the non-image area on the electrostatic latent image bearing member cannot be sufficiently removed, causing scumming. If it exceeds 4 cst, the time required for development becomes long and the printing speed of the printer is reduced.

As such a hydrocarbon solvent, a petroleum hydrocarbon insulating solvent is preferable.

The average particle size of the colored particles used in the present invention is 0.1 to 2.5 μm, preferably 0.5 to
2 μm.

In the image forming method using the intermediate transfer member, the latent image on the electrostatic latent image carrier is intermediately transferred to the electrostatic latent image carrier when the toner is transferred from the electrostatic latent image carrier to the intermediate transfer member. Due to the contact of the body, pressure is generated in the latent image. Therefore, when the average particle size is less than 0.1 μm, the amount of the solvent existing between the particles increases, and the strength of the latent image cannot withstand the pressure during transfer,
Dot tailing that draws a tail in the printing direction occurs.
Further, when the average particle diameter exceeds 2.5 μm, the particle diameter of the toner with respect to the pixel becomes large, and the image becomes rough on a fine line of the printed matter.

The colored particles are mainly composed of a coloring material composed of a pigment or a dye and a resin, but colored particles in which the pigment is dispersed in the resin are preferable. The proportion of the pigment in the particles is preferably from 5% by weight to 30% by weight.

Examples of the resin include alkyd resin, styrene resin, phenol resin, acrylic resin, styrene-acrylic resin, polyester resin, rosin-modified phenol resin, rosin-modified maleic acid resin, etc., but rosin-modified maleic acid resin is used. Preferably.

Common pigments and dyes are used. If they are black, carbon black (commercially available products such as Mitsubishi Kasei's # 30, # 40, # 50, MA-1
1. MONARCH 700, 900, R manufactured by Cabot
In addition to EGAL300, 400, 600R, etc.), it is also possible to mix alkali blue with carbon black.

If it is yellow, it is benzidine yellow, if it is red, it is brilliant carmine, fast red,
Quinacridone red, phthalocyanine blue for indigo, phthalocyanine green, oil violet, methyl orange, methyl violet, etc. are also used.

Although the colored particles are mainly composed of a coloring material and a resin, polyethylene glycol, polypropylene glycol or the like may be added for adjusting the softening point.

Further, a charge control agent, wax or the like may be added to the particles or on the surface of the particles in order to control the charge and improve the dispersibility.

To prepare the liquid developer of the present invention, the resin and the colorant are melt-kneaded by applying heat with a twin-screw extruder, a kneader, etc., coarsely crushed, and then a charge control agent, wax, etc. By using a ball mill, a vibration mill, an attritor, or the like in an oil-based hydrocarbon-based insulating solvent together with the additive to disperse the particles, it is possible to set the dispersion conditions for obtaining a predetermined particle size and particle distribution.

The method for measuring the average particle diameter of the present invention is as follows:
It can be measured using a Shimadzu centrifugal sedimentation type particle size distribution analyzer SA-CP3.

As a method of measuring the viscosity of the developer,
It can be measured using a B-type viscometer.

Next, the image forming method of the present invention will be described.

The liquid developer of the present invention is used in a method of forming an electrostatic latent image on an electrostatic latent image carrier and developing the latent image with liquid toner to form an image, but preferably it is static. Liquid toner is applied to the electrostatic latent image on the electrostatic latent image carrier via a developing roller.
It is used in an image forming method in which a liquid toner is supplied and developed, and more preferably, an electrostatic latent image on an electrostatic latent image bearing member is supplied with a liquid toner through a developing roller to develop the image, and the image is developed by this development. A full-color image is formed on the intermediate transfer member by repeating the process of electrostatically transferring the visualized image thus formed to the intermediate transfer member, and the full-color image on the intermediate transfer member is transferred onto the transfer material. It is preferably used for an image forming method of retransferring to

Here, the contact with the intermediate transfer member means that the intermediate transfer member and the electrostatic latent image carrier are in contact with each other at two or more points without developing the toner. In the process of actually developing and transferring the toner, it is considered that the intermediate transfer body and the electrostatic latent image carrier are in contact with each other via the toner image.

As the intermediate transfer member of the present invention, one having a silicone rubber layer on the surface of rubber having high heat resistance such as fluororubber via an adhesive layer is used.

The material to be transferred referred to in the present invention is as follows.
Any kind of paper, plastic film, metal, cloth, board, etc. can be used as long as it can be printed normally.

[0031]

EXAMPLES Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

(Example 1) 1540 g of rosin-modified fumaric acid resin (Unilet's 8112, acid value 115, softening point 130 ° C., manufactured by Union Camp), carbon black (M
OGUL-L) 400 g, polyethylene glycol (P
60 g of EG6000, manufactured by Sanyo Kasei Co., Ltd. was premixed with a mixer and then melt-kneaded using a twin-screw extruder (feed amount 2 kg / hr, temperature 100 ° C.). After cooling the obtained melt-kneaded material, a particle size of about 5 was obtained using a sample mill.
A coarse powder of 0 μm was obtained. 200 g of this coarse powder and 110 g of an acrylic polymer type charge control agent solution (US Pat.
0, 412, manufactured by the method described in Example XI, solid content 14%), carnauba wax 15 g, and petroleum hydrocarbon solvent, solvent A having the following characteristics: volume resistivity 10 ¹⁶ or more 20 Kinematic viscosity at ℃ 2.5cst boiling point range 225 ℃ to 242 ℃ 50 ℃ and 10 ℃ kinematic viscosity difference of 1.57cst 1250g are mixed and pulverized in a vibration mill for 5 hours,
A liquid toner having an average particle diameter of 1.5 μm was obtained. This stock solution was diluted with the solvent A so as to have a solid content concentration of 2% to obtain a developer.

At a room temperature of 20 ° C., a Se drum is used as a photoconductor, and the liquid developer thus obtained is developed with a developing roller at a linear velocity of the photoconductor of 120 mm / sec to form on the photoconductor. The transferred toner image is transferred onto an intermediate transfer member having a silicone rubber layer on the drum as the outermost layer, and the toner image on the intermediate transfer member is transferred onto an art paper at 20 k.
g linear pressure is applied, and the temperature of the pressure roller is 200 ° C.
When transferred at a linear velocity of 40 mm / sec,
An image having a print density of 1.4 with no white background stain was obtained. Further, when the temperature was raised to 30 ° C. and the printing was repeated and the temperature of the photosensitive member was 40 ° C., the same printing was carried out. As a result, an image having a printing density of 1.48 without white background stain was obtained. . Further, when the printed matter was enlarged and examined with a microscope, it was found that a good image without dot tailing and smooth fine lines of 30 μm without roughness was obtained. It turned out that there was no.

Further, 200 sheets were continuously printed, but the fluctuation of the printing density was suppressed within 0.15, and good printed matter could be obtained with good reproducibility.

Example 2 A liquid toner was prepared in the same manner as in Example 1 except that 400 g of benzidine yellow was used instead of carbon black, and a yellow toner having an average particle size of 1.2 μm was obtained.

When 400 g of brilliant carmine was used instead of carbon black to prepare a liquid toner in the same manner as in Example 1, a magenta toner having an average particle diameter of 1.4 μm was obtained.

When 400 g of phthalocyanine blue was used instead of carbon black to prepare a liquid toner in the same manner as in Example 1, a cyan toner having an average particle size of 0.9 μm was obtained.

At room temperature of 20 ° C., a Se drum was used as a photoconductor, and the four color liquid developers thus obtained were sequentially developed with a developing roller at a linear velocity of the photoconductor of 120 mm / sec. The yellow, magenta, cyan, and black toners are sequentially transferred for each color onto the intermediate transfer body having the silicone rubber stuck on the outermost layer, and a full-color image is formed on the intermediate transfer body. A linear pressure of 20 kg was applied to the art paper, the temperature of the pressure roller was 200 ° C., and transfer was performed at a linear velocity of 40 mm / sec. As a result, a high-density good image without white background stains such as yellow print density 1.4, magenta print density 1.2, cyan print density 1.4, and black print density 1.4 was obtained. Furthermore, as a result of continuously printing 500 sheets,
It was found that the fluctuation of the print density was suppressed within 0.2, and the overlapping color was reproduced well.

(Comparative Example 1) In the same manner as in Example 1, instead of the solvent A, Isopar H (manufactured by Exxon Co., boiling point range 1) was used.
When a liquid toner was prepared by using 76 ° C. to 192 ° C., a black toner having an average particle diameter of 2 μm was obtained.

When printing was performed using this toner in the same manner as in Example 1, the print density of the first printed sheet was 1.6, whereas the print density of the 200th printed sheet was 1.2. I knew there was a problem.

Comparative Example 2 In the same manner as in Example 1, instead of the solvent A, IP solvent 2835 (manufactured by Idemitsu Petroleum Co., Ltd.,
When a liquid toner was prepared using a boiling point range of 275 ° C. to 350 ° C., a black toner having an average particle size of 1 μm was obtained.

Printing was carried out using this toner in the same manner as in Example 1, but fixing was not possible at a linear velocity of the pressure roller of 40 mm / sec, and a linear velocity of 10 m was required for sufficient fixing.
It was necessary to set m / sec, and the printing speed decreased.

Comparative Example 3 In the same manner as in Example 1, instead of the solvent A, Cristol 52 (manufactured by Esso Oil Co., Ltd. at 50 ° C.) was used.
And a difference in kinematic viscosity at 10.degree. C. of 3.90 cst) were used to prepare a liquid toner, a black toner having an average particle diameter of 1.3 .mu.m was obtained.

Using this toner, printing was performed in the same manner as in Example 1 except that the linear velocity of the pressure roller was 10 mm / sec. An image with a print density of 0.9 was obtained at room temperature of 20 ° C., and printing was repeated. When printing was performed in the same manner with the temperature of the photoconductor at 40 ° C., the printing density was 1.3.
Image was obtained, and it was found that the print density greatly depends on the temperature.

(Comparative Example 4) In the same manner as in Example 1, instead of the solvent A, light red white (manufactured by Witco, 2
When a liquid toner was prepared using a kinematic viscosity at 0 ° C. of 5 cst), a black toner having an average particle size of 1.1 μm was obtained.

Printing was carried out in the same manner as in Example 1 using this toner, but the printing density was 1.0 at room temperature of 20 ° C., which is lower than that in Example 1. ,
It was necessary to reduce the linear velocity of the photoconductor to 80 mm / sec, and the printing speed decreased.

(Comparative Example 5) A liquid toner was prepared in the same manner as in Example 1 except that Nisseki Isozol 200 (manufactured by Nippon Petrochemical Co., Ltd., kinematic viscosity of 0.7 cst at 20 ° C) was used instead of the solvent A. A black toner having an average particle diameter of 2.1 μm was obtained.

Printing was carried out in the same manner as in Example 1 using this toner, but a white background stain was generated and a good printed matter could not be obtained.

[0049]

As described above, by using the developer of the present invention, a good printed matter having a high print density can be obtained
It can be obtained stably for the process.

Claims (5)

[Claims] 1. A developer in which colored particles comprising at least a resin and a coloring material and having an average particle size of 0.1 to 2.5 μm are dispersed in an insulating liquid, wherein the insulating liquid is a hydrocarbon solvent. The main component is a hydrocarbon solvent having a boiling point range of 200 ° C. or higher and 270 ° C. or lower, and a difference in kinematic viscosity between 10 ° C. and 50 ° C. is 3
A liquid developer having a kinematic viscosity at 20 ° C. of 1 cst or more and 4 cst or less. 2. The liquid developer according to claim 1, which is used in an image forming method in which a liquid toner is supplied to an electrostatic latent image on an electrostatic latent image carrier through a developing roller to develop the image. 3. An electrostatic latent image on an electrostatic latent image carrier is supplied with a liquid toner through a developing roller to develop the image, and the image visualized by this development is statically contacted with an intermediate transfer member. 3. The image forming method according to claim 2, wherein a full-color image is formed on the intermediate transfer member by repeating the step of electrically transferring, and the full-color image on the intermediate transfer member is re-transferred onto the transfer material. Liquid developer. 4. An image forming method for supplying an electrostatic latent image on an electrostatic latent image bearing member with a liquid toner through a developing roller to develop the electrostatic latent image, wherein the liquid developer according to claim 1 is used. Image forming method. 5. An image forming method, in which an electrostatic latent image on an electrostatic latent image carrier is supplied with a liquid toner through a developing roller to develop the image, and the image visualized by this development is intermediately transferred. By repeating the process of electrostatic transfer while contacting the body,
The image forming method according to claim 4, wherein the image forming method is a method of forming a full-color image on the intermediate transfer member and re-transferring the full-color image on the intermediate transfer member onto a transfer material.