JP2001092183A - Developer and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developer having enough offset resistance and preservation property with which good picture quality is obtained. SOLUTION: The binder resin in the developer has 3 to 10 (g/10 min) melt index at 110 deg.C and 10 to 20 (g/10 min) melt index at 190 deg.C. The wax used has <=80 deg.C melting point and <=20 cSt dynamic viscosity at 100 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic apparatus and a developer used for the same, and more particularly, to an image forming apparatus using an oilless type fixing device without an oil supply mechanism. And a developer used therein.

[0002]

2. Description of the Related Art In heat roller fixing, toner passes between heated heat rollers to fuse toner and fix it on paper. At this time, if the roller surface temperature is too low, low-temperature offset occurs, and if it is too high, high-temperature offset occurs. The offset is the most unfavorable phenomenon in the heat roller method, and occurs when a part of the toner image is peeled off by the upper roller when passing between the heat rollers.

As a technique for preventing the offset, there is a method of applying silicone oil to a heat roller and a press roller of a fixing device.

First, the adverse effects of applying silicone oil to a heat roller and a press roller of a fixing device will be described. The following problems occur during the long-term use.

[0005] Silicon oil accumulates on the peeling claw of the paper, which comes into contact with the press roller or the heat roller, and transfers to the press roller or the heat roller when the limit is exceeded, which appears as dirt on the copy.

[0006] When the silicon oil supply member is constantly in contact with the heat roller and the press roller, the surface of the heat roller and the press roller is worn, and the life is shortened.

[0007] The cost of the copying machine increases because the supply member requires a complicated structure.

In some cases, offset is prevented by improving the toner without applying silicone oil.
The offset is suppressed mainly by adding a low melting point wax such as carnauba wax. However, it has not been possible to satisfy all the characteristics including deterioration of image quality due to long-term use and storage stability under high temperature.

[0009]

SUMMARY OF THE INVENTION An object of the present invention has been made in view of the above circumstances, and provides a developer which has sufficient offset resistance and storage stability and can provide an image having good image quality. Is to do.

Another object of the present invention is to provide an image forming apparatus capable of preventing occurrence of offset and obtaining an image having good image quality.

[0011]

According to the present invention, there is firstly provided a colorant and a melt index value at 110.degree.
(G / 10 minutes), a binder resin having a melt index value at 190 ° C. of 10 to 20 (g / 10 minutes),
Provided is a developer containing a wax having a melting point of 80 ° C. or less and a kinematic viscosity at 100 ° C. of 20 cSt or less.

Second, the present invention provides a method in which a colorant and a colorant are added to an electrostatic latent image formed by exposing a photoreceptor to light.
C. The melt index value at 3 ° C. is 3-10 (g / 10 min), and the melt index value at 190 ° C. is 10-20.
Means for forming a developer image by supplying a developer containing a binder resin (g / 10 minutes), a wax having a melting point of 80 ° C. or less, and a kinematic viscosity at 100 ° C. of 20 cSt or less; Provided is an image forming apparatus comprising: means for transferring an image onto a transfer material; and a fixing device for heating and fixing the transferred developer image.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The developer of the present invention contains a colorant, a binder resin, and a wax, and the binder resin has a melt index value at 110 ° C. of 3 to 10 (g / 10).
Min) and the melt index value at 190 ° C. is 1
0 to 20 (g / 10 minutes), and the wax has a melting point of 80 ° C. or less and a kinematic viscosity at 100 ° C. of 20 cSt or less.

An image forming apparatus according to the present invention is an apparatus using the above-described developer, and supplies the developer according to the present invention to an electrostatic latent image formed by exposing a photosensitive member. The image forming apparatus further includes means for forming a developer image, means for transferring the developer image onto a transfer material, and a fixing device for heating and fixing the transferred developer image.

In the above apparatus, the fixing temperature at the time of fixing is preferably 160 to 180 ° C.

According to the present invention, offset is prevented and good fixability is obtained by defining the melt index of the binder resin of the developer and using a wax having a low softening point and a low kinematic viscosity in combination. Further, this developer has good storage stability.

When the melt index value of the binder resin at 110 ° C. is less than 3 (g / 10 minutes), the viscosity does not decrease sufficiently at the time of fixing, causing a low-temperature offset, and exceeding 10 (g / 10 minutes). When the developer is stored at a high temperature, which can be considered when transporting the developer, a lump is formed. Also, 1
If the melt index value at 90 ° C. is less than 10 (g / 10 minutes), the viscosity does not decrease sufficiently at the time of fixing, so that a low-temperature offset occurs.
When the temperature of the fixing device rises, a high-temperature offset occurs because the viscosity of the developer becomes too low.

The melt index value at 110 ° C. is preferably 5 to 8 (g / 10 minutes), and the melt index value at 190 ° C. is preferably 12 to 18 (g / 1).
0 minutes).

On the other hand, if the melting point of the wax exceeds 80 ° C., the effect of lowering the friction of the image surface due to bleeding during fixing is lost, and the smearing performance is reduced. Further, when the kinematic viscosity at 100 ° C. exceeds 20 cSt, a sufficient releasing effect between the developer and the heat roller cannot be obtained, so that a high-temperature offset occurs.

Examples of the binder resin preferably used in the present invention include styrenes such as styrene and black styrene, monoolefins such as ethylene, propylene, butylene and isoprene, vinyl acetate, vinyl propionate, and the like.
Vinyl esters such as vinyl benzoate and vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate,
Dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate,
Α-methylene aliphatic monocarboxylic acid esters such as butyl methacrylate and dodecyl methacrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone; Homopolymers or copolymers can be exemplified, and particularly typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, Styrene-butadiene copolymer,
Styrene maleic anhydride copolymer, polyethylene, polypropylene and the like.

The wax preferably used in the present invention is:
Rice wax.

Colorants preferably used in the present invention include, for example, carbon black, nigrosine dye, aniline blue, calcoil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green Oxalate, lamp black, rose bengal, C.I. I. Pigment Red 4
8: 1, C.I. I. Pigment Red 122, C.I. I.
Pigment Red 57, C.I. I. Pigment Yellow 12, C.I. I. Pigment Blue 15: 1, and C.I. I. Pigment Blue 15: 3.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic diagram for explaining the image forming apparatus of the present invention.

As shown in FIG.
Is uniformly applied with a surface potential of −500 to 800 V by the charging device 2, an electrostatic latent image is formed by the exposure device 3, and the toner is negatively charged by the developing device 4. Thereby, the latent image is visualized. The developer used at this time has a colorant and a melt index value at 110 ° C. of 3 to 10 (g / 10 minutes) and a melt index value at 190 ° C. of 10 to 20 (g / 10 minutes). Certain binder resin, melting point below 80 ° C, and 100 ° C
And a wax having a kinematic viscosity of 20 cSt or less. In the transfer step, the belt 5 is pressed against the photoreceptor 1, a paper P, which is a transfer target, is interposed between the belt 5 and the photoreceptor 1, and a bias (+300) applied to the belt by the high-voltage power supply 9. To 5 kV), the toner image on the photoconductor 1 is transferred to the paper P. The belt unit has a configuration in which an elastic belt having a volume resistance of 10e8 to 1012 Ω · cm is supported by a plurality of rollers. By driving one of the rollers 7, the belt rotates at substantially the same surface moving speed as the photosensitive member. I do. The power supply member has a volume resistance of 10e2 to 10e8 Ωcm.
Power is supplied from the back surface of the belt in a region where the photoconductor 1 and the belt 5 are in contact with each other using the conductive elastic roller 8 described above. In normal printing, the belt 5 and the photoreceptor 1 are driven in a state where they are separated from each other, are brought into contact with each other after reaching approximately the same surface speed, and a transfer bias is applied to the power supply roller 8 and at the same time, the subject is photographed. The paper P is transported and reaches the transfer nip area.
The paper that has passed through the transfer nip between the photoreceptor 1 and the power supply roller 8 is electrostatically attracted onto the belt 5, but the curvature of the drive roller 7 of the belt 5 is large (usually φ12 to 40). At the most downstream side of the unit, the leading end of the paper P separates from the belt and is conveyed to the fixing device 11 through the guide member.

Downstream of the transfer nip, after the excess toner is removed by the cleaning unit 13, the charge is removed by the charge removing unit 14.

In the fixing device 11, fixing is performed at a fixing temperature of 160 to 190 ° C. by the heat roller 15 and the pressure roller 10. The fixing device 11 used here is an oilless type having no oil supply mechanism.

Examples 1 to 4 and Comparative Examples 1 to 7 Preparation of Binder Styrene and methyl acrylate were prepared as resin materials. For synthesis, a flask containing isopropanol as a reaction solvent was prepared. 75 ° C
Styrene, methacrylic acid, and azobisisobutyronitrile (AIB) as a polymerization initiator.
The mixture with N) was added dropwise over 4 hours, and polymerization was carried out with stirring. Immediately after the completion of the dropwise addition, the temperature was raised to 80 ° C., and the polymerization reaction was continued. After the completion of the polymerization, the reaction product is dried under reduced pressure, heated and dried to obtain a solid copolymer. The reaction time at this time was adjusted to obtain a plurality of samples having different melt indexes (hereinafter, MI) as shown in Table 2 below.

Further, each resin was combined with a wax as shown in Table 2 below by the following formulation, heated and kneaded, cooled, pulverized and classified to obtain toner particles.

Toner formulation Resin Resin 90% Carbon black MA-100 (manufactured by Mitsubishi Kasei) / 5% Wax 4% Charge control agent TRH (manufactured by Hodogaya Chemical Co.) / 1% The properties of the wax used are as follows: As shown in Table 1.

[0031]

[Table 1]

Thereafter, the obtained toner particles are mixed with 0.5% of hydrophobic silica R972 (manufactured by Nippon Aerosil Co., Ltd.),
A toner sample was obtained.

6 parts by weight of the toner thus prepared and a volume average diameter of 80 (μm) made of silicon-coated iron powder.
m) stirring the carrier for 1 hour using a ball mill,
A developer sample was obtained. The MI was measured using a melt indexer. When the temperature is 110 ° C., the load is 21600 g, and the unit is g / 10 minutes. When the temperature is 190 ° C., the load is 2160 g, and the unit is g.
/ 10 minutes.

The following tests were performed on the obtained developer samples and evaluated.

Test Methods Evaluation Method of Offset Evaluation of fixability was performed using Toshiba copier Leo Dry 6550. When the power was turned on and copying was possible, 200 copies of an A3-size original including halftones and characters were copied.
The 200th copy image was visually observed, and it was determined as x when the character portion was offset, Δ when the halftone portion was offset, and ○ when the offset was not observed. This was evaluated as low-temperature offset.

The evaluation of the high-temperature offset was performed in this manner. First, 200 copies of the A4 portrait document were copied.
An A4-size original document with a 20 mm solid portion at the leading end is copied. Immediately after the A4 length, the temperature of the fixing unit is higher than the initial set value in the portion where the A4 length paper does not pass (both ends in the A4 width). Observation was made on the passing state, and "x" indicates that the paper wrapped around the fixing device at the solid portion, "x" indicates that the paper did not wrap but was observed on the paper as an offset, and "o" indicates that an image was obtained without any problem.

Evaluation Method for Smear (Stain on Back Side of Original When Using Automatic Document Feeder) The smear was evaluated using a Toshiba copier Leo Dry 6550. When the power is turned on and copying is enabled, 50 A4 horizontal character originals are copied. Thereafter, the obtained copy is set on an automatic document feeder. Then, the back side of the original after passing through the white moving original feeder was observed, and when the position of the automatic original feeder was soiled by the width of the paper, x was given, when only the end was dirty, Δ was given, and when it was not dirty at all, ○ was given.

Evaluation Method of Deterioration of Developer Deterioration of the developer was carried out using a Toshiba copier Leo Dry 6550. 200,000 copies were made using a chart of A4 size and the area of the character portion occupying 6% of the whole area, and a sheet in which toner scattering caused by deterioration of the developer did not affect the copied image was passed.

Evaluation Method of Storage Property The storage property was evaluated by packing 20 g of the toner in 100 cc of a polybin, leaving it in a water tank at 50 ° C. for 8 hours, observing the state of the toner, and determining that the toner was not solidified at all. What was solidified by heat was evaluated as x.

Table 1 summarizes the evaluation results.

[0041]

[Table 2]

As can be seen from Table 2, when the melt index was out of the range of the present invention as in Comparative Examples 1 to 4, offset occurred and the preservability of the developer was poor. Comparative Example 5
Even if the wax is outside the scope of the present invention as in
Fixing performance was poor. Further, when no wax was added as in Comparative Example 7, the fixing performance was considerably deteriorated.

On the other hand, the developers of Examples 1 to 4 had good fixing performance, storage stability and image quality.

[0044]

According to the present invention, it is possible to obtain a developer having sufficient offset resistance and preservability and capable of obtaining an image having good image quality.

According to the present invention, the occurrence of offset is prevented, and an image having good image quality can be obtained.

Further, according to the present invention, even if an oilless type having no oil supply mechanism is employed as a fixing device, a high-quality image having good offset resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photoreceptor 2 ... Charging device 3 ... Exposure device 4 ... Developing device 5 ... Belt 7 ... Roller 8 ... Conductive elastic roller 10 ... Pressure roller 11 ... Fixing device 13 ... Cleaning means 14 ... Static elimination means 15 ... Heat roller

Claims (6)

[Claims] 1. A colorant and a binder resin having a melt index value at 110 ° C. of 3 to 10 (g / 10 minutes) and a melt index value at 190 ° C. of 10 to 20 (g / 10 minutes). A developer containing a wax having a melting point of not higher than 100 ° C and a kinematic viscosity at 100 ° C of not higher than 20 cSt. 2. The melt index value at 110 ° C. is 5 to 8 (g / 10 minutes), and the melt index value at 190 ° C. is 12 to 18 (g / 10 minutes). Item 7. The developer according to Item 1. 3. An electrostatic latent image formed by exposing a photoreceptor to a colorant, a melt index value at 110 ° C. of 3 to 10 (g / 10 min), and a melt index at 190 ° C. A developer image is formed by supplying a developer containing a binder resin having an index value of 10 to 20 (g / 10 minutes), a melting point of 80 ° C. or less, and a kinematic viscosity at 100 ° C. of 20 cSt or less. An image forming apparatus comprising: means for transferring the developer image onto a material to be transferred; and a fixing device for heating and fixing the transferred developer image. 4. The melt index value at 110 ° C. is 5 to 8 (g / 10 minutes), and the melt index value at 190 ° C. is 12 to 18 (g / 10 minutes). Item 4. The image forming apparatus according to Item 3. 5. An oilless type wherein the fixing device has a heating roller surface-treated with a fluorine-based material and has no oil supply mechanism.
An image forming apparatus according to claim 1. 6. The image forming apparatus according to claim 3, wherein the heating temperature of the fixing device is set to 160 to 180 ° C.