JP2002082504A - Multicolor image forming method and multicolor image forming apparatus - Google Patents

Abstract

(57) [Problem] To form a high-quality image by improving the reduction of the image density of a toner image due to the transfer on the upstream side and preventing the occurrence of fog and voids in the repetition of a plurality of transfer steps. To provide a multicolor image forming method and a multicolor image forming apparatus which enable the above. SOLUTION: An electrostatic latent image is formed on each surface, and a predetermined color toner corresponding to each image carrier is sequentially supplied onto a plurality of image carriers arranged in parallel, and the electrostatic latent image is formed. A multicolor image forming method in which a color toner image formed by development is sequentially superimposed and transferred onto a transfer material each time the color toner image is developed to form a multicolor image. Each color toner contains silicone oil, and the silicone oil content of the color toner that develops the electrostatic latent image of the image carrier arranged on the upstream side among the plurality of image carriers arranged in parallel is The color toner for developing the electrostatic latent image on the image carrier disposed on the downstream side is larger than the silicone oil content.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor image forming method and apparatus for recording an image on paper or a resin film by an electrophotographic method, such as a printer, a facsimile, a copying machine, and the like. The present invention relates to a multicolor image forming method and a multicolor image forming apparatus in which a reduction in image density of a toner image due to transfer on an upstream side in repetition of a transfer process is improved.

[0002]

2. Description of the Related Art Generally, image formation by an electrophotographic system is performed by developing an electrostatic latent image with toner to visualize the image, and transferring the toner image obtained by the development to a sheet. The toner used for such image formation is usually manufactured by pulverizing and classifying a composition containing a binder resin and a colorant.

As a binder resin used for a toner, a polyester resin having excellent transparency is used particularly for forming a multicolor image. However, since the polyester resin has a hydrophilic group,
The moisture resistance is low, and the chargeability of the toner is reduced. Therefore, when an image is formed using a toner containing a polyester resin as a binder resin, fogging occurs particularly under high temperature and high humidity, and a high quality image cannot be obtained.

On the other hand, fine silica powder has been added to the toner in order to impart fluidity and uniform chargeability to the toner. However, since the fine silica powder has a hydrophilic property, moisture in the air is reduced. As a result, the toner is aggregated and the chargeability is reduced.

In order to solve such a problem, it has been proposed to add hydrophobic fine silica powder to the toner. For example, Japanese Patent Publication No. 7-120068 describes that as an external additive of a toner, silica treated with hexamethyldisilazane (HMDS) and further subjected to a spraying treatment with dimethyl silicone oil is added. Have been.

Japanese Patent Publication No. Hei 7-113783 discloses a method in which a silica fine powder treated with a silane coupling agent and then treated with various silicone oils is used as an external additive of the toner. Have been.

However, even if the silica fine powder subjected to the hydrophobic treatment is used, its effect is insufficient.
In particular, under high-humidity conditions, it was impossible to prevent a decrease in the chargeability of the toner.

[0008] In recent years, small and inexpensive copiers and printers have been sold and used in ordinary homes. Under such circumstances, under normal temperature and normal humidity,
It is desired to obtain high quality images even under various environments such as high temperature and high humidity and low temperature and low humidity.

[0009]

As described above, conventionally, there has been proposed a toner to which silica which has been hydrophobized by various processing methods using various processing agents is externally added. However, even with such a toner, it is not enough to solve the deterioration of image quality under high temperature and high humidity. That is, even when a toner to which hydrophobic silica is externally added is used, such a toner has poor transferability. For example, when printing 6,000 sheets, voids (white background due to non-transfer of toner) occur in a solid portion, or high temperature Fog is generated under moisture.

In a tandem type color image forming apparatus in which a plurality of developing devices are arranged in parallel, the transfer process is repeated a plurality of times for each color. At this time, the toner once transferred in the first transfer process is There is a problem that the toner adheres to the developing roll in a subsequent transfer step, that is, the color due to the transfer on the upstream side becomes light.

[0011] The present invention has been made under such circumstances,
A multi-color image forming method and a multi-color image forming method capable of forming a high-quality image with a balanced image density in each color even when transfer is repeated a plurality of times while preventing generation of fog and voids It is an object to provide an image forming apparatus.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an electrostatic latent image formed on each surface, and a plurality of image bearing members arranged in parallel. A predetermined color toner is sequentially supplied, the electrostatic latent image is developed, and the color toner image formed by the development is sequentially superimposed and transferred onto a transfer material every time it is developed to form a multicolor image. A color image forming method, wherein each of the color toners contains a silicone oil, and develops an electrostatic latent image of an image carrier arranged on an upstream side among the plurality of image carriers arranged in parallel. A multicolor image forming method, wherein the silicone oil content of the color toner to be developed is greater than the silicone oil content of the color toner for developing the electrostatic latent image on the image carrier disposed downstream. .

The present invention also provides a plurality of image carriers each having an electrostatic latent image formed on a surface thereof, and a plurality of image carriers each forming a predetermined color toner image on the plurality of image carriers. A developing unit, a conveying unit that circulates to transfer the transfer material to each of the plurality of image carriers, and a color toner image on the image carrier on the transfer material conveyed to the image carrier by the conveyance unit. A tandem-type multicolor image forming apparatus comprising: a plurality of transfer units for sequentially superimposing and transferring; and a fixing unit for thermally fixing a toner image transferred onto the transfer material, wherein each color used for the plurality of developing units is provided. The toner contains silicone oil, and is a color toner silicone oil used for developing means for developing an electrostatic latent image of the image carrier arranged upstream from the plurality of image carriers arranged in parallel. Content is located downstream Providing a multicolor image forming apparatus characterized by more than the silicone oil content of the color toner used in the developing means for developing the electrostatic latent image on the image bearing member.

In the multicolor image forming method and the multicolor image forming apparatus of the present invention configured as described above, the silicone oil contained in each color toner is dimethyl silicone oil, alkyl-modified silicone oil, α-methylstyrene-modified silicone. Desirably, it is selected from the group consisting of oil, chlorophenyl-modified silicone oil and fluorine-modified silicone oil.

Preferably, the plurality of transfer means respectively corresponding to the plurality of image carriers arranged in parallel are contact-type transfer means arranged so as to press the transfer material against the corresponding image carriers. .

In the toner used in the multicolor image forming method and the multicolor image forming apparatus of the present invention, the binder resin is
It is preferable to use a polyester resin.

In the present invention, the silicone oil contained in the toner is selected from the group consisting of dimethyl silicone oil, alkyl-modified silicone oil, α-methylstyrene-modified silicone oil, chlorophenyl-modified silicone oil, and fluorine-modified silicone oil. Can be used. Desirably, the silicone oil has a viscosity of 0.1 to 3 Pa · s.

The content of silicone oil in the toner is as follows:
The highest content of the toner used for the upstream development is 0.2 to 0.5 parts by weight with respect to 100 parts by weight of the toner, and the lowest content of the toner used for the downstream development is 0.2.
It is preferably from 02 to 0.14 parts by weight. In addition,
The content of silicone oil in the toner does not have to always decrease stepwise from the upstream side to the downstream side, but if it does not increase, the silicone oil content of the toner used for adjacent development and transfer May be the same.

For example, in a configuration in which four image carriers are arranged in parallel, the toner used in the most upstream development and transfer has the highest silicone oil content, and the toner used in the most downstream development and transfer has the silicone oil content. Lowest but middle 2
The silicone oil content of the toner used in one development and transfer may be a value between the two and may be the same.

A known charge control agent may be added to the toner according to the present invention, if necessary. Examples of the charge control agent include, for example, a quaternary ammonium salt or a salt forming compound thereof to obtain a positively chargeable toner, and a metal complex or a metal complex salt of salicylic acid or an alkylsalicylic acid to obtain a negatively charged toner. Boron-containing potassium salt compounds are preferred. The amount of these charge control agents is
The range of 0.01 to 20 parts by weight relative to 0 parts by weight is preferred.

Further, various waxes may be added to the toner according to the present invention as a release agent for improving thermal characteristics. Further, the toner of the present invention may contain inorganic oxide fine particles such as silica, titania, and alumina as a fluidity improver in a range of 0.01 to 5 parts by weight based on 100 parts by weight of the toner.

The toner according to the present invention can be manufactured by various manufacturing methods. Generally, it can be manufactured by the following manufacturing method. First, a resin, a colorant, and if necessary, a charge control agent, a wax, a fluidity improver, and the like are uniformly mixed by a Henschel mixer or the like. Next, the mixture is melt-kneaded using a kneader, an extruder, a roll mill or the like.

Next, the kneaded material is roughly pulverized using a hammer mill, a cutter mill, or the like, and then finely pulverized using a jet mill, a single-type mill, or the like. Thereafter, the finely pulverized material is classified by a DS (dispersion classifier), a zigzag classifier or the like. The average particle size of the toner obtained by classification is preferably 3 to 18 μm.

Thereafter, a silicone oil is added to the classified toner particles to produce a toner. In some cases, silica may be further added to the toner using a Henschel Kimiser. The silica may be one whose surface has been subjected to a hydrophobic treatment using silicone oil or the like.

As described above, according to the present invention, the silicone oil content of the color toner for developing the electrostatic latent image of the image carrier arranged upstream is selected from the plurality of image carriers arranged side by side. Since the silicone oil content of the color toner for developing the electrostatic latent image on the image carrier disposed on the downstream side is larger than the silicone oil content, the transfer is performed in the first transfer step when the transfer step is repeated a plurality of times. In addition, it is possible to obtain a multicolor image which is less likely to generate a void, prevents a decrease in the image density of the toner image, and is faithful and clear to a document and has good color reproducibility.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, and the present invention will be described more specifically. FIG. 1 schematically shows an internal configuration of a color image forming apparatus according to an embodiment of the present invention. First, the overall configuration of the color image forming apparatus will be described with reference to FIG.

As shown in FIG. 1, the color image forming apparatus (main body apparatus) 30 has an opening / closing tray 31 on its rear surface (left side in the figure) and a lower part from the front side (right side in the figure) of the main body apparatus. A removable paper cassette 32 is provided. A large number of sheets are placed and stored in the sheet cassette 32.

The main unit 30 has an upper lid 33 on its upper surface. Although not shown in the drawing, a power switch, a liquid crystal display device, a plurality of input keys, and the like are provided on the front side of the upper lid 33. The upper lid 33 has a
A paper discharge tray 34 is formed together with the upper surface of the rear part 0.

Inside the main unit 30, a flat loop-shaped paper transport belt (hereinafter, simply referred to as a belt) 35 is disposed substantially in the center and extends back and forth. It is held by a driving roller 36 and a driven roller 37. The belt 35 is driven by a driving roller 36 and circulates in a counterclockwise direction indicated by an arrow R in the figure. Along the upper circulation portion of the belt 35, four photosensitive drums 38 (38a, 38b, 38c, 38d)
They are arranged in a multi-stage manner in the paper transport direction (from right to left in the figure).

These photosensitive drums 38 (38a, 38)
b, 38c, 38d) (representatively, only the peripheral devices around the photoreceptor drum 38d are denoted by reference numerals) so as to surround the cleaner 41, the initialization charging roller 42, the writing head 43, and A developing device 44 (44d) is provided. Further, the contact type sheet transfer device 39 is
The transfer portion is formed by being pressed against the photosensitive drum 38 via the belt 35. The photosensitive drums 38a, 38b,
The developing devices 44a, 44b, 4
4c is arranged.

Developing device (developing hopper) 44 (44d)
Is provided with a developing roller 45 rotatably supported in the lower opening thereof. The developing roller 45 contacts the peripheral surface of the photosensitive drum 38 to form a developing unit. The write head 43 is disposed on the back surface of the upper lid 33 via a support member 46, moves up and down in an arc as the upper lid 33 opens and closes, descends when the upper lid 33 is closed, and initializes. It is positioned between the roller 42 and the developing roller 45 to form a recording unit.

At the upstream end of the upper circulation portion of the belt 35,
The suction roller 47 is driven by the driven roller 37 via the belt 35.
To form a paper carry-in section. The suction roller 47 presses the belt 35 while applying a suction bias to the sheet carried into the sheet carrying unit, and the belt 35
Paper is electrostatically attracted to the paper.

The uppermost photosensitive drum 3 in the paper transport direction
Each developing device from the developing device 44a for 8a to the developing device 44d corresponding to the photosensitive drum 38d has three primary colors of M (magenta), C (cyan), Y (yellow), and Bk (black), which are the subtractive primary colors. Each color toner is stored. Each of these color toners contains silicone oil, and the silicone oil content of the toner contained in the upstream developing device is greater than the silicone oil content of the toner contained in the downstream developing device. Has been adjusted to be higher.

On the upstream side (right side in the drawing) of the belt 35 in the transport direction, a standby roll pair 48 and a paper feed guide path 49 are disposed below the standby roll pair 48. A roll pair 51 is provided. The paper feed end of the paper cassette 32 described above is located upstream (below) of the feed roll pair 51. A paper feed roller 52 is provided above the paper feed end of the paper cassette 32. The feed roller 52 is rotated every rotation.
The uppermost sheet contained in the sheet cassette 32 is taken out and fed to the feed roll pair 51.

On the other hand, a fixing device 53, a pair of paper discharge rolls 54, and a switching lever 55 are provided downstream of the belt 35 in the paper transport direction (left side in the drawing). The fixing device 53 includes a pressure contact roller, a fixing roller, a heating roller, a paper separating claw, a peripheral surface cleaner, an oil application member,
It is composed of a thermistor or the like, and heat-fixes the toner image transferred onto the paper to the paper surface.

When the switching lever 55 is at the lower position as shown in the figure, the switching lever 55 guides the sheet to the discharge tray 34 via the upper discharge path 56 and the discharge roll pair 57. On the other hand, when rotating upward, the sheet is guided to the opening / closing tray 31 opened on the rear surface of the main unit.

Between the belt 35 and the paper cassette 32,
An electrical unit 58 on which a circuit board can be mounted is provided, and a control device including a plurality of electronic components is mounted on the circuit board.

The control unit comprises a controller unit and an engine unit. The controller unit is a CPU (central processing unit), ROM (read only memory), EEPROM (rewritable read memory), frame memory, image data transfer. It has a circuit and the like, analyzes print data input from a host computer or the like, creates print data, and transfers it to the engine unit.

The engine unit includes a CPU, a ROM, and the like.
On the input side, data and command signals from the controller unit, the output of the temperature sensor, the output of the paper detection sensor, etc. are input.On the output side, a motor driver that drives a motor (not shown) A clutch driver for switching the drive system to be transmitted, a print driver for driving the write head 43 based on the print data, an initialization charging roller 42, a developing roller 45, a transfer device, a suction roller 47,
A bias power supply driver or the like that supplies a predetermined bias voltage to a toner supply roller, a doctor blade, a developing unit scooping sheet, and the like, which will be described later, is connected. The engine unit controls the driving of each unit based on data and command signals from the controller unit, the output of the temperature sensor, the output of the sheet detection sensor, and the like.

Next, the color image forming apparatus 3 described above
The basic operation of 0 will be described. First, when the power is turned on and the paper quality, the number of sheets to be used, the print mode, and other designations are input as a key input or a signal from a host device to be connected, the paper feed roller 52 rotates one turn by a drive mechanism (not shown). Then, the paper stored in the paper cassette 32 is fed to the standby roll pair 48 via the feed roll pair 51. The standby roll pair 48 suspends the rotation, and waits for the transport timing in a state in which the leading end of the sheet abuts on a holding portion formed by a pair of rollers.

Subsequently, the driving roller 36 rotates counterclockwise, and the driven roller 37 is driven to rotate similarly in the counterclockwise direction. As a result, the belt 35 has four photosensitive drums 38a, 38b, 38c,
In contact with d, the whole circulates in the counterclockwise direction.

At the same time, the developing units 44a, 44b, 4
4c, 44d and photosensitive drums 38a, 38b, 38
c and 38d are sequentially driven in accordance with the printing timing. The photoconductor drum 38 rotates clockwise, the initialization charging roller 42 applies a uniform high negative charge to the peripheral surface of the photoconductor drum 38, and the writing head 42 applies Exposure is performed according to an image signal to form a low potential portion. As a result, an electrostatic latent image composed of a high negative potential portion due to the initialization and a low negative potential portion due to exposure is formed. The developing roller 45 of the developing device 44 transfers the toner to a low potential portion of the electrostatic latent image to form a toner image on the peripheral surface of the photosensitive drum 38 (reversal development).

At the timing when the leading end of the toner image on the peripheral surface of the most upstream photosensitive drum 38a is rotated and conveyed to the point facing the belt 35, the printing start position of the paper coincides with the point. Then, the standby roll pair 48 starts rotating and feeds the paper to the paper carry-in section.

The driven roller 37 and the suction roller 47 hold and transport the fed sheet together with the belt 35. The sheet is attracted to the belt 35 and transported to the first transfer section formed by the photosensitive drum 38a and the transfer device.

The transfer unit applies a transfer current output from a transfer bias power supply to a sheet via a belt 35. The transfer current applied from the transfer device causes the photosensitive drum 3
The M (magenta) toner image on 8a is transferred to the sheet. Subsequently, at the second transfer portion from the upstream formed by the photosensitive drum 38b and the transfer device, C (cyan)
Is transferred, and further the toner image of the third transfer portion Y (yellow) from the upstream formed by the photosensitive drum 38c and the transfer device is transferred. Then, a Bk (black) toner image is sequentially transferred at the most downstream transfer portion formed by the photosensitive drum 38d and the transfer device.

In this case, the silicone oil content of the toner contained in the upstream developing device is adjusted to be higher than the silicone oil content of the toner contained in the downstream developing device. A reduction in image density of the toner transferred on the upstream side due to the repetition of the transfer process a plurality of times is offset, and a desired image density is obtained.

The paper on which the four color toner images have been transferred in this manner is separated from the belt 35 and carried into the fixing device 53. The fixing device 53 thermally fixes the toner image on the sheet. After the image is fixed, the paper is discharged by the discharge roll pair 54 with the toner image upward on the opening / closing tray 31 on the rear surface or the toner image downward on the upper discharge tray 34.

FIG. 2 is a side sectional view schematically showing a main part of the developing unit 44. The developing device 44 shown in FIG. 1 is detachable from the color image forming apparatus 30 and is a developing unit that forms one image forming unit together with the drum unit. The developing device 44 includes a housing 61 also serving as a toner hopper, and rotatably holds a developing roller 45 made of a conductive rubber roller at a lower opening of the housing 61.
Inside the housing 61, there is provided a toner stirring member 63 which accommodates the toner 62 and is disposed so as to be buried in the toner 62.

At the lowermost part of the developing device 44, a supply roller 64 made of a sponge body is disposed in pressure contact with the developing roller 45. The developing roller 45 is pressed against the obliquely upper right peripheral surface thereof by a metallic leaf spring-shaped doctor blade 65.
The developing unit scooping sheet (conductive regulation sheet) 66 is arranged in contact with the lower peripheral surface. The developing unit scooping sheet 66 is provided with a later-described conductive regulating sheet bias unit including a bias power supply 71. On both sides of the doctor blade 65, sealing members 67 for separating the inside and the outside of the opening of the housing 61 and preventing leakage of the toner 62 are provided.

Incidentally, in order to scrape off the non-developed portion of the toner 62 remaining on the peripheral surface of the developing roller 45 after the development on the photosensitive drum 38 is completed, the toner 62 is scraped off in the housing 61 to eliminate the developing memory. The required rubbing force of the supply roller 64 depends on the adhesion of the toner 62 to the developing roller 45. That is, a strong rubbing force is required for a toner having a strong adhesive force, but a weak rubbing force is sufficient for a toner having a weak adhesive force. The developing roller 45 of the toner 62
It can be said that the adhesive force to the toner is substantially determined by the charging ability of the toner 62. That is, the smaller the amount of triboelectric charge, the weaker the adhesive force, and thus the easier it is to scrape off the developing roller 45.

However, the amount of frictional charge of the toner 62 has a close relationship with the adhesion development (hereinafter referred to as photoreceptor fogging) on a non-image portion which occurs during development and causes a problem. The more the photoreceptor is fogged, the more likely it is. Therefore, in order to prevent such photoconductor fog from occurring, it is necessary to increase the triboelectric charge amount of the toner 62. When the frictional charge amount of the toner 62 is increased, the adhesive force to the developing roller 45 is increased.
4 needs to be given a strong rubbing force.

It is not preferable to repeat the rotation for a long period of time with such a strong rubbing force, because it causes deterioration of the toner characteristics such as a decrease in toner charging ability and a decrease in fluidity. For example, when the charge amount is reduced, the above-described photoreceptor fogging is generated, and when the fluidity is reduced, the lack of development in halftone printing occurs.

In the developing device 44 having such a problem, in one embodiment of the present invention, first, the developing roller 45 is made of a metal core and a cylindrical semiconductive (10 ⁶ Ωcm) surrounding the metal core. ), And a developing bias of “−250 V” is applied to the core metal from a bias power supply 68. As described above, a predetermined amount of silicone oil is applied to the surface of the developing roller 45.

The supply roller 64 is composed of a cored bar and a cylindrical semiconductive (10 ⁶ Ωcm) urethane sponge surrounding the cored bar, and a supply bias of “−500 V” is applied to the cored bar. Applied from power supply 69.

Further, the doctor blade 65 is formed of an elastic metal plate, and a doctor bias of "-500 V" is applied to the doctor blade 65 from the bias power source 69. Then, the developing unit scooping sheet 66 located on the upstream side of the supply roller 64 is formed of a conductive member (10 ³ Ωcm), and a sheet in a range from 0 V (0 volt) to the developing bias voltage of the developing roller 45 is provided. A bias voltage is applied by a bias power supply 71.

As described above, the developing unit scooping sheet 66 is formed of a conductive member, and the sheet bias voltage in the range from 0 V to the developing bias voltage of the developing roller 45 is applied thereto. This is to reduce the charge of the toner 62 attached. Thereby, the supply roller 6
4, the developing roller 45 can be easily rubbed by the weak rubbing force.
The non-developed portion of the toner that has adhered and returned has been scraped off.

Incidentally, in the developing device 44 shown in FIG.
For convenience, application of a developing bias voltage to the developing roller 45 is performed by a bias power supply 68, and application of a sheet bias voltage to the developing unit scooping sheet 66 is performed by a bias power supply 7.
Although described in the example in which the power supply is performed individually according to 1, the power supply does not need to be provided separately in this way. That is, in the actual developing unit configuration of the present invention, for example, a voltage dividing circuit including a resistance element is provided in the unit, and the bias voltage divided into each of the developing roller 45 and the developing unit scooping sheet 66 by the common bias power supply of the apparatus main body. A voltage is applied.

By the color image forming apparatus and the image forming process having the above-described apparatus configuration, the reduction of the density balance due to the repetition of the transfer process is improved, the generation of voids is small, the color is faithful to the original, and the color reproducibility is improved. It is possible to obtain a good multicolor image.

[0059]

The present invention will be described more specifically with reference to the following examples. First, a production example of a binder resin for a toner used in each embodiment will be described.

Production Example 1 (Resin A) Polyoxypropoxypropylene (2,2) -2.2-bis (4-hydroxyphenyl) propane 1050 g Polyoxypropoxyethylene (2,2) -2.2-bis (4 -Hydroxyphenyl) propane 325 g Terephthalic acid 330 g Fumaric acid 240 g Hydroquinone 0.5 g Each of the above compounds was placed in a four-liter glass flask having a capacity of 2 liters. A nitrogen inlet tube was attached. Then, while flowing nitrogen in the electric heating mantle heater,
While stirring at 180 ° C. in the first half and 200 ° C. in the second half under reduced pressure, the reaction was carried out while tracking the acid value to produce a polyester. The acid value of the obtained polyester was 27.0 (mgK
OH / g).

Production Example 2 (Resin B) Polyoxypropoxypropylene (2,2) -2.2-bis (4-hydroxyphenyl) propane 840 g Polyoxypropoxyethylene (2,2) -2.2-bis (4 -Hydroxyphenyl) propane 195 g Terephthalic acid 249 g Fumaric acid 132 g 1,2,5-Pentenetricarboxylic acid 29 g Dibutyltin oxide 2 g Hydroquinone 0.5 g Using the same apparatus as in Production Example 1, the above compounds were formulated in the same manner. The reaction was performed while tracking the acid value. The acid value of the obtained polyester was 19.0 (mgKOH / g)
Met.

Production Example 3 (Resin C) Polyoxypropoxypropylene (2,2) -2.2-bis (4-hydroxyphenyl) propane 578 g Polyoxypropoxyethylene (2,2) -2.2-bis (4 -Hydroxyphenyl) propane 176 g Trimethylolpropane 72 g Isophthalic acid 472 g The above compounds were reacted in the same apparatus as in Production Example 1 and in the same formulation, while tracking the acid value. The acid value of the obtained polyester was 16.0 (mgKOH / g).
Met.

Production Example 4 (Resin D) Polyoxypropoxypropylene (2,2) -2.2-bis (4-hydroxyphenyl) propane 770 g Polyoxypropoxyethylene (2,2) -2.2-bis (4 -Hydroxyphenyl) propane 720 g Terephthalic acid 690 g 1,2,4 Tri-n-ethylhexyl 1,2,4 benzenetricarboxylate 120 g Using the same apparatus as in Production Example 1, using the same formulation, and tracking the acid value, The reaction proceeded. The acid value of the obtained polyester was 2.1 (mgKOH / g).

Embodiment 1 In the color image forming apparatus shown in FIG. 1, the silicone oil content of the toner of each color used for the developing means on the upstream side in the transfer material transport direction corresponding to the four image carriers is shifted downstream. The following Example 1 was used so that the silicone oil content of the toner used for the developing means arranged was larger than that of the toner.
-A, each color toner adjusted as in Example 1-B, Example 1-C, and Example 1-D was prepared by the following method.

Example 1-A Polyester resin (resin A: acid value: 27.0 mg KOH
/ G) 100 parts by weight, a charge control agent (LR-147 manufactured by Nippon Carlit Co., Ltd.) 1.5 parts by weight, a polypropylene resin 2.0 parts by weight, and a coloring pigment (red pigment: Pig.R)
ed57: 1) 3.0 parts by weight were mixed in a Henschel mixer, melt-kneaded in a hot roll mill, cooled, coarsely ground using a hammer mill, then finely ground by an air jet method, and dispersed classification. Machine, the particle size is 5
A 20 μm fraction was obtained.

100 parts by weight of this classified product and dimethyl silicone oil (KF96-50 manufactured by Shin-Etsu Chemical Co., Ltd.)
0cs) (kinematic viscosity 5 cm ² / s) 0.20 parts by weight was mixed with a Henschel mixer to obtain a toner powder treated with silicone oil.

1.5 parts by weight of silicon oxide fine powder (RX-50, manufactured by Nippon Aerosil Co., Ltd.) was added to 100 parts by weight of this toner powder.
The parts by weight were further mixed with a Henschel mixer to obtain a red toner.

Example 1-B Polyester resin (resin A: acid value: 27.0 mg KOH
/ G) 100 parts by weight, a charge control agent (LR-147 manufactured by Nippon Carlit Co., Ltd.) 1.5 parts by weight, a polypropylene resin 2.0 parts by weight, and a coloring pigment (copper b phthalocyanine:
Pig. Blue 15: 3) 3.0 parts by weight were mixed with a Henschel mixer, melt-kneaded with a hot roll mill, cooled, coarsely crushed using a hammer mill, finely crushed by an air jet method, and dispersed classification. The particles were dispersed by a machine to obtain a classified product having a particle size of 5 to 20 μm.

100 parts by weight of this classified product and dimethyl silicone oil (KF96-50 manufactured by Shin-Etsu Chemical Co., Ltd.)
0cs) (kinematic viscosity: 5 cm ² / s) 0.18 parts by weight was mixed with a Henschel mixer to obtain a toner powder treated with silicone oil.

To 100 parts by weight of the toner powder, 1.5 parts of silicon oxide fine powder (RX-50, manufactured by Nippon Aerosil Co., Ltd.) was added.
The parts by weight were further mixed with a Henschel mixer to obtain a blue toner.

Example 1-C Polyester resin (resin A: acid value: 27.0 mg KOH
/ G) 100 parts by weight, 1.5 parts by weight of a charge control agent (LR-147 manufactured by Nippon Carlit Co., Ltd.), 2.0 parts by weight of a polypropylene resin, and a coloring pigment (yellow pigment, disazo yellow: Pig. Y-17) 3 Was mixed with a Henschel mixer, melt-kneaded with a hot roll mill, cooled, coarsely ground using a hammer mill, then finely ground by an air jet method, and dispersed by a dispersion classifier. A classified product having a particle size of 5 to 20 μm was obtained.

100 parts by weight of the classified product and dimethyl silicone oil (KF96-50 manufactured by Shin-Etsu Chemical Co., Ltd.)
0cs) (kinematic viscosity 5 cm ² / s) 0.16 parts by weight was mixed with a Henschel mixer to obtain a toner powder treated with silicone oil.

To 100 parts by weight of the toner powder, 1.5 parts of silicon oxide fine powder (RX-50, manufactured by Nippon Aerosil Co., Ltd.) was added.
The parts by weight were further mixed with a Henschel mixer to obtain a yellow toner.

Example 1-D Polyester resin (resin A: acid value: 27.0 mg KOH
/ G) 100 parts by weight, charge control agent (Hodogaya Chemical Co., Ltd.)
T-77) 1.5 parts by weight, 2.0 parts by weight of a polypropylene resin, and a black pigment (carbon black: Monarch 8)
80) 4.0 parts by weight were mixed in a Henschel mixer, melt-kneaded in a continuous extruder, cooled, coarsely crushed using a hammer mill, then finely crushed by an air jet method, and dispersed classification. Dispersed by a machine, particle size is 5-20μm
Was obtained.

100 parts by weight of this classified product and dimethyl silicone oil (KF96-50 manufactured by Shin-Etsu Chemical Co., Ltd.)
0cs) (kinematic viscosity 5 cm ² / s) 0.14 parts by weight was mixed with a Henschel mixer to obtain a toner powder treated with silicone oil.

To 100 parts by weight of the toner powder, 1.5 parts of silicon oxide fine powder (RX-50, manufactured by Nippon Aerosil Co., Ltd.) was added.
The parts by weight were further mixed with a Henschel mixer to obtain a black toner.

Using the above-described red toner, blue toner, yellow toner, and black toner, a color printer (Color Page Press N4-612: manufactured by Casio) printed 6,000 sheets, and the toner image transferred on the upstream side was printed. There was no decrease in density, no voids were generated, and an image output faithful and clear to the original and having good color reproducibility was obtained.

When printing was performed in a high-temperature, high-humidity environment of 32.5 ° C. and 80 RH%, a good image was obtained. Further, when printing was performed in an environment of 10.5 ° C. and 20 RH%, a good image was obtained.

Example 2 As a polyester resin, resin B was used instead of resin A.
(Acid value: 19.0 mgKOH / g) A red toner, a blue toner, a yellow toner, and a black toner were produced in the same manner as in Example 1 except that the toner was changed to 19.0 mgKOH / g.

When these toners were printed on a color printer (Color Page Presto N4-612: manufactured by Casio) for 6,000 sheets, there was no decrease in the image density of the toner transferred on the upstream side and no voids were generated. An image output faithful to the manuscript and having good color reproducibility was obtained.

When printing was performed in a high-temperature, high-humidity environment of 32.5 ° C. and 80 RH%, a good image was obtained. Further, when printing was performed in an environment of 10.5 ° C. and 20 RH%, a good image was obtained.

Example 3 As a polyester resin, resin C was used instead of resin A.
(Acid value: 16.0 mgKOH / g) A red toner, a blue toner, a yellow toner, and a black toner were produced in the same manner as in Example 1, except that the toner was changed to 16.0 mgKOH / g.

When these toners were printed on a color printer (Color Page Presto N4-612: manufactured by Casio) for 6,000 sheets, there was no decrease in the image density of the toner transferred on the upstream side and no voids were generated. An image output faithful to the manuscript and having good color reproducibility was obtained.

When printing was performed in a high-temperature, high-humidity environment of 32.5 ° C. and 80 RH%, a good image was obtained. Further, when printing was performed in an environment of 10.5 ° C. and 20 RH%, a good image was obtained.

Example 4 Resin D was used instead of resin A as a polyester resin.
A red toner, a blue toner, a yellow toner, and a black toner were produced in the same manner as in Example 1 except that (acid value: 2.1 mgKOH / g) was used.

When these toners were printed on a color printer (Color Page Presto N4-612: manufactured by Casio) for 6,000 sheets, there was no decrease in the image density of the toner transferred on the upstream side, and no voids were generated. An image output faithful to the manuscript and having good color reproducibility was obtained.

When printing was performed in a high temperature and high humidity environment of 32.5 ° C. and 80 RH%, a good image was obtained. Further, when printing was performed in an environment of 10.5 ° C. and 20 RH%, a good image was obtained.

Example 5 The amounts of silicone oil added were 0.16 parts by weight for the red toner, 0.14 parts by weight for the blue toner, and 0.1 parts by weight for the yellow toner.
A red toner, a blue toner, a yellow toner, and a black toner were produced in the same manner as in Example 1, except that the amount of the black toner was adjusted to 12 parts by weight and the amount of the black toner was adjusted to 0.12 parts by weight.

When these toners were printed on a color printer (Color Page Press N4-612: manufactured by Casio) for 6,000 sheets, there was no decrease in the image density of the toner transferred on the upstream side and no voids were generated. An image output faithful to the manuscript and having good color reproducibility was obtained.

When printing was performed in a high-temperature, high-humidity environment of 32.5 ° C. and 80 RH%, a good image was obtained. Further, when printing was performed in an environment of 10.5 ° C. and 20 RH%, a good image was obtained.

Comparative Example 1 The amounts of silicone oil added were 0.12 parts by weight for the red toner, 0.14 parts by weight for the blue toner, and 0.1% for the yellow toner.
A red toner, a blue toner, a yellow toner, and a black toner were produced in the same manner as in Example 1 except that the amount of the black toner was adjusted to 14 parts by weight and the amount of the black toner was adjusted to 0.16 parts by weight.

When these toners were printed on a color printer (Color Page Presto N4-612: manufactured by Casio) for 6,000 sheets, voids were generated and image output with poor color reproducibility was obtained. Further, among the four colors, the image density of the toner transferred on the upstream side, particularly the red toner, decreased.

Further, when printing was performed in a high-temperature, high-humidity environment of 32.5 ° C. and 80 RH%, the number of voids increased and an image output having extremely poor color reproducibility was obtained.

[0094]

As described above in detail, according to the present invention, a color toner for developing an electrostatic latent image of an image carrier arranged upstream from a plurality of image carriers arranged in parallel. Is larger than the silicone oil content of the color toner that develops the electrostatic latent image on the image carrier disposed on the downstream side, so that the upstream side in the repetition of a plurality of transfer steps. It is possible to obtain a multicolor image which is improved in reduction of the image density of a toner image due to transfer, has less voids, is faithful to a document, is clear, and has good color reproducibility.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an internal configuration of a color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a side sectional view schematically showing a main part of a developing device of the color image forming apparatus of FIG.

[Explanation of symbols]

 Reference Signs List 30 color image forming apparatus 31 opening / closing tray 32 paper cassette 33 top cover 34 paper discharge tray 35 paper transport belt 36 driving roller 37 driven roller 38, 38a, 38b, 38c, 38d photosensitive drum 39 Sheet transfer unit 41 Cleaner 42 Initializing charging roller 43 Writing head 44a, 44b, 44c, 44d Developing unit.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Tadahiro Tsubaki, 4084 Miyadera, Iruma-shi, Saitama, Japan Casio Electronics Co., Ltd. (72) Yasuo Kamoshita 4084 Miyadera, Iruma-shi, Saitama, Japan Terms (reference) 2H005 AA08 AA21 CA12 EA07 2H030 AB02 AD01 AD04 AD05 BB23 BB34 BB38 BB44 BB46 2H032 AA05 AA15 BA01 BA05 BA18

Claims (4)

[Claims] An electrostatic latent image is formed on a surface of each of the plurality of image carriers, and a predetermined color toner corresponding to each of the image carriers is sequentially supplied to the plurality of image carriers. And a multi-color image forming method of forming a multi-color image by sequentially superimposing and transferring a color toner image formed by the development onto a transfer material each time the toner is developed, wherein each of the color toners is a silicone oil. The silicone oil content of the color toner that develops the electrostatic latent image of the image carrier arranged on the upstream side among the plurality of image carriers arranged side by side is arranged on the downstream side. A multicolor image forming method, wherein the content of the silicone oil in the color toner for developing the electrostatic latent image of the image carrier is increased. 2. The silicone oil contained in each color toner is selected from the group consisting of dimethyl silicone oil, alkyl-modified silicone oil, α-methylstyrene-modified silicone oil, chlorophenyl-modified silicone oil and fluorine-modified silicone oil. Item 1
2. The method for forming a multicolor image according to item 1. 3. A plurality of image carriers each having a surface on which an electrostatic latent image is formed, and a plurality of developing means for forming a predetermined color toner image on the plurality of image carriers, respectively. Transport means for circulating and transferring the transfer material to each of the plurality of image carriers; and sequentially transferring the color toner images on the image carriers onto the transfer material transported to the image carriers by the transport means. A tandem-type multicolor image forming apparatus including a plurality of transfer units and a fixing unit that thermally fixes the toner image transferred onto the transfer material, wherein each color toner used in the plurality of development units is silicone. The oil-containing silicone oil content of the color toner used for the developing unit that develops the electrostatic latent image of the image carrier disposed on the upstream side among the plurality of image carriers arranged side by side, Of the image carrier arranged downstream Multi-color image forming apparatus, characterized in that more than the silicone oil content of the color toner used in the developing means for developing the latent image. 4. A plurality of transfer means respectively corresponding to the plurality of image carriers arranged in parallel are contact-type transfer means arranged so as to press the transfer material against the corresponding image carriers. The multicolor image forming apparatus according to claim 3, wherein: