JP2001312093A - Developer, image forming device and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a developer which has good storage property at high temperature, can sufficiently be applied to a less-oil fixation and can form a good image. SOLUTION: The developer contains toner particles containing a coloring agent and a polyester resin having 50 to 70 deg.C or lower glass transition point, and a metal oxide having 30 to 1000 nm average particle size deposited on the toner particles. The developer shows <=25 J/g endothermic energy at <=100 deg.C measured by differential scanning calorimetric and the coating rate of the metal oxide to the toner particles satisfying 4<=(coating rate/endothermic energy 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 method such as an electrophotographic method and an electrostatic recording method and a developer used for the method, and more particularly to a full-color image forming technique for forming a color image.

[0002]

2. Description of the Related Art In an electrophotographic apparatus or an electrostatic recording apparatus, an electrostatic latent image formed on an image carrier from a photoreceptor or a derivative is visualized by developing it with a developer. After the transferred developer image is transferred to the transfer material, the image is formed by fixing.

Conventionally, there has been a problem that a developer, when exposed to a high temperature of about 50 ° C., tends to cause a so-called blocking phenomenon in which the toner solidifies.

In order to prevent the blocking phenomenon, it has been proposed to set a high glass transition point Tg or softening point Tm of, for example, a binder resin or wax.

[0005] Alternatively, for example, Japanese Patent Publication No. 8-1678.
No. 9 discloses that toner particles obtained by kneading a natural wax having a heat absorption range of 50 ° C. or more by DSC with a binder resin are used as a developer.

However, even if the above-mentioned natural wax is used, the occurrence of blocking over the life cannot be sufficiently prevented. Particularly, in the case of a full-color developer using a binder resin which can be melted at a low temperature, less oil is used. In order to realize fixing, it was necessary to add a large amount of wax that melts at about 50 to 100 ° C. For this reason, full-color developers have poor high-temperature preservability, and temperature control during distribution and storage is strict.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a first object of the present invention is to provide a good image which has good high-temperature storability and is sufficiently applicable to a less oil fixing. Is to provide a developer that can obtain the following.

A second object of the present invention is to provide an image forming method capable of obtaining a good image without fixing even at a high temperature and sufficiently applicable to oilless fixing.

[0009]

According to a first aspect of the present invention, toner particles containing a polyester resin and a colorant having a glass transition point of 70 ° C. or lower, and toner particles adhered to the toner particles; A metal oxide having an average particle diameter of 30 nm to 1000 nm, a heat absorption at 100 ° C. or less by a differential scanning calorimeter of 25 J / g or less, and a coverage of the metal oxide on the toner particles is represented by the following formula: There is provided a developer represented by the following formula: 4 ≦ coverage / endotherm of 100 ° C. or less.

According to a second aspect of the present invention, there is provided an electrostatic latent image forming step of forming an electrostatic latent image on an image carrier, and the step of forming the electrostatic latent image on a polyester having a glass transition point of 70 ° C. or less. It contains a toner particle containing a resin and a colorant, and a metal oxide having an average particle diameter of 30 nm or more, and has a heat absorption of 100 J or less by a differential scanning calorimeter of 25 J / g or less. A developing step of developing using a developer in which the coverage of the metal oxide is represented by the following formula: 4 ≦ coverage / 100 ° C. or less; transfer of transferring the developed developer image onto a transfer-receiving material And an image forming method including a fixing step of fixing the developer image transferred onto the transfer material to the transfer material.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The developer of the present invention contains toner particles containing a polyester resin having a glass transition point of 70 ° C. or lower and a colorant, and further contains 3
A metal oxide having an average particle size of 0 nm or more is mixed and adhered, and its heat absorption at 100 ° C. or less by differential scanning calorimetry is 25 J / g or less, and the coverage of the metal oxide on toner particles is Is represented by the following formula: 4 ≦ coverage / endotherm of 100 ° C. or less.

According to the present invention, a binder resin mainly composed of a polyester resin having a glass transition point of 70 ° C. or less is used in a toner particle, a developer exhibits a predetermined heat absorption amount, and a predetermined average heat absorption amount. Metal oxide having a particle size,
By being applied to the surface of the toner particles at a predetermined coverage, it is possible to prevent the occurrence of blocking which is often observed in a developer which can be melted at a low temperature, and it can be suitably used for a color developer, thereby achieving high image quality. And a full-color image free of roughness due to fixing with less oil can be obtained.

The polyester resin used in the present invention comprises:
It has a glass transition point of 70 ° C. or less. The glass transition point is
Preferably 50 ° C to 70 ° C, more preferably 55 ° C.
C. to 65.degree. When the glass transition point is lower than 50 ° C., the storage resistance at high temperatures is significantly deteriorated, and it tends to be difficult to sufficiently improve the storage stability even when the present invention is used.

In the developer of the present invention, for example, a wax which starts absorbing heat at 70 ° C. or lower can be further added to the toner particles. The addition amount is preferably 2 to 20% by weight based on the total weight of the toner particles. By adding wax, the developer was measured by differential scanning calorimetry.
The endothermic amount of 0 ° C. or less can be adjusted. As such wax, rice wax, carnauba wax, candelilla wax, montan wax, paraffin wax, synthetic ester wax and the like can be used.

A differential scanning calorimeter (DSC) is a device that quantitatively and easily measures the flow of heat accompanying physical and chemical changes that occur when the temperature of a substance is continuously changed. DSCs include a calorific value compensation type and a heat flow rate type. The amount of heat absorbed in the present invention is based on a value measured by a heat flow type device. In this apparatus, for example, a horizontal metal plate is provided in an electric furnace having a uniform temperature, and a measurement sample and a reference sample are symmetrically arranged on the metal plate. If the temperature of the furnace is raised or processed at a constant rate, the two samples rise and fall at the same temperature, but if one causes an endothermic reaction, a temperature difference occurs between the two samples. This temperature difference is reduced by a heat flow flowing through a metal plate or the like on which the sample is placed. At this time, the amount of heat flowing into or out of the sample per unit time is proportional to the temperature difference between the sample and the surroundings, that is, the temperature difference between the sample and the reference substance. Therefore, by integrating ΔT from time when the temperature difference ΔT occurs to when the temperature difference ΔT becomes zero again with respect to time, it is possible to know the amount of heat flowing into and out of the sample. A differential thermocouple is welded to the position on the back surface of the metal plate where the two samples are placed, and ΔT is detected. The detected value is corrected in consideration of heat lost due to radiation and convection in addition to heat conducted to the metal plate, and the obtained value is measured and recorded as a calorific value signal. The heat lost by the radiation and convection changes depending on the temperature and the like.

The toner particles used in the present invention preferably have an average particle size of about 6 to 10 μm.

On the other hand, the metal oxide used in the present invention is:
It has an average particle size of 30 nm to 1000 nm.

The metal oxide used in the developer of the present invention adheres to the surface of the toner by being mixed with the toner particles. The amount of the metal oxide added to the toner particles is preferably 1 to 5% by weight based on the total weight of the toner particles.

Examples of the polyester resin used in the present invention include bisphenol derivatives represented by the following chemical formula (1).

[0020]

Embedded image

(Wherein R is an ethylene or propylene group, and the average value of x and y is 2 to 10) or a substituted product thereof as a diol component, a divalent or higher carboxylic acid or an acid anhydride thereof, Alternatively, a polyester resin which is at least co-condensed with a carboxylic acid component (for example, fumaric acid, maleic acid, maleic anhydride, phthalic acid, terephthalic acid, etc.) comprising the lower alkyl ester can be preferably used.

The colorant used in the present invention includes, for example, disazo yellow, insoluble azo,
Dyes include basic dyes and oil-soluble dyes.

Particularly preferably, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 97, C.I. I. Pigment Yellow 15, C.I. I. Pigment Yellow 1
3, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 18
0, C.I. I. Pigment Red 5, C.I. I. Pigment Red 3, C.I. I. Pigment Red 2, C.I. I. Pigment Red 6, C.I. I. Pigment Red 7, C.I.
I. Pigment Red 122, C.I. I. Pigment Red 184, C.I. I. Pigment Red 57: 1, C.I.
I. Pigment Blue 15: 3, C.I. I. Pigment Blue 16 and the like.

As the dye, C.I. I. Solvent Red 4
9, C.I. I. Solvent Red 52, C.I. I. Solvent Red 109, C.I. I. Basic Red 12, C.I.
I. Basic Red 1, C.I. I. Basic Red 3
B and the like.

In addition, the following pigments or dyes can be used as a coloring material suitably used in the present invention.

Examples of the dye include C.I. I. Direct Red, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Morant Tread 30, C.I. I. Direct Blue 1,
C. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5 and C.I. I.
Morant Blue 7 and the like.

Examples of the pigment include naphthol yellow S, Hansa yellow G, permanent yellow NCG, permanent orange GTR, pyrazolone orange, benzidine orange G, permanent red 4R, mutting red calcium salt, brilliant carmine 3B, fast violet B, methyl Violet lake, phthalocyanine blue, fast sky blue, indanthrene blue BC and the like.

The amount of the coloring agent added to the binder resin is preferably 12 parts by weight or less, more preferably 0.1 part by weight, per 100 parts by weight of the binder resin for a yellow toner which is sensitive to the transparency of the OHP film. 5 to 7 parts by weight.

When the amount of the colorant added to the binder resin is 12 parts by weight or more, the reproducibility of the mixed color of yellow, green and red, and the image of human skin color tends to be poor.

For other magenta and cyan color toners, 1 to 100 parts by weight of the binder resin is used.
5 parts by weight or less, more preferably 0.1 to 9 parts by weight or less is desirable.

As the image bearing member in the present invention, an organic photosensitive member containing 5 to 40% by weight of a fluorine resin on the surface thereof is preferable.

An image forming apparatus according to the present invention is an apparatus to which the above-mentioned developer is applied, wherein the image forming apparatus is provided on an image carrier provided opposite to the image carrier. A developing device for developing the electrostatic latent image to form a developer image, a transfer device for transferring the developer image onto the transfer material, and a developer device for transferring the developer image onto the transfer material. A fixing device for fixing is provided, and in a developing device, toner particles containing a polyester resin and a colorant having a glass transition point of 70 ° C. or less, and an average particle size of 30 nm or more attached to the toner particles. And a metal oxide having 10% by differential scanning calorimetry.
A developer containing an endotherm at 0 ° C. or less of 25 J / g or less and a covering rate of the metal oxide to the toner particles represented by the following formula: 4 ≦ coverage / 100 ° C. or less is contained.

An image forming method according to the present invention is a method using the above-described apparatus, wherein an electrostatic latent image forming step of forming an electrostatic latent image on an image carrier and developing the electrostatic latent image are performed. Developing using a developer to form a developer image, a transfer step of transferring the developed developer image onto a transfer material, and a fixing step of fixing the transferred developer image to the transfer material And a toner particle containing a polyester resin and a colorant having a glass transition point of 70 ° C. or lower, and a metal oxide having an average particle diameter of 30 nm or more attached to the toner particles. And the heat absorption at 100 ° C. or less by a differential scanning calorimeter is 25 J / g or less, and the coverage of the metal oxide on the toner particles is represented by the following formula: 4 ≦ coverage / heat absorption at 100 ° C. or less. The developer is stored.

Next, an image forming apparatus according to this embodiment will be described with reference to the drawings. In the drawings used, the same reference numerals represent the same components.

FIG. 1 is a schematic view showing an example of the image forming apparatus of the present invention. This apparatus is also used in the image forming method according to the present invention.

In FIG. 1, a photosensitive drum 1a as an image carrier is a cylindrical laminated organic photosensitive member having a diameter of 40 mm and a length of 266 mm, and is provided so as to be rotatable in the direction of an arrow as shown in the figure.

The following components are provided around the photosensitive drum 1a along the rotation direction. A charging roller 5a composed of a conductive rubber roller for uniformly charging the photosensitive drum 1a is provided in contact with the surface of the photosensitive drum 1a. An exposure section 7a for exposing the charged photosensitive drum 1a to form an electrostatic latent image is provided downstream of the charging roller 5a. Further, downstream of the exposure unit 7a, toner particles containing a polyester resin having a glass transition point of 50 ° C. to 70 ° C. or less and a colorant, and 30 nm to 1000 nm attached to the toner particles.
a metal oxide having an average particle size of m, an endothermic amount of 100 J or less by differential scanning calorimetry of 25 J / g or less, and a coating ratio of the metal oxide to toner particles is represented by the following formula: A developing device 9a is provided which stores a developer represented by a rate of heat absorption of 100 ° C. or less and develops the electrostatic latent image formed by the exposure unit 7a with the developer.
Downstream of the developing device 9a, a transport unit for transporting a sheet P as a recording material to the photosensitive drum 1a is provided.
This transport means 11 will be described later.

Further, a blade cleaning device 17 is located downstream of the contact position of the photosensitive drum 1a with the sheet P.
a and a static elimination lamp 19a. The blade cleaning device 17a removes the developer remaining on the photosensitive drum 1a after the transfer of the developer image described later, to the blade 21.
To remove it. The charge removing lamp 19a is a tungsten lamp that removes light from the surface of the photosensitive drum 1a after transfer. This static elimination lamp 19
One cycle of image formation is completed by the static elimination by a. Next, when an image is formed, the uncharged photosensitive drum 1a is charged again by the charging roller 5a.

The conveying means 11 has a width substantially equal to the drum width of the photosensitive drum 1a. This transport means 11
1 is in the form of an annular belt, for example, as shown in FIG. 1, and a tension roller 13 and a driving roller 15 are provided on the upstream and downstream annular portions of the conveying means 11, respectively.
Is provided. In this annular portion, the conveying means 11 moves along the outer circumferences of the tension roller 13 and the driving roller
Is in contact with The distance from the tension roller 13 to the drive roller 15 is about 300 mm. As shown in FIG. 1, the tension roller 13 and the drive roller 15 are provided so as to be rotatable in directions of arrows i and j.
With the rotation of the drive roller 15, the conveying means 11 is sent in a ring shape in the direction of arrow e. The transport speed is
The rotation speed is controlled to be equal to the rotation speed of the photoconductor.

Here, the belt used as the conveying means is:
Two functions, that is, the conveyance of the recording material and the transfer of the developer, are required, but here, it is simply referred to as a transfer belt. This transfer belt is composed of 25 parts by weight of conductive carbon particles and 75 parts by weight of thermosetting polyimide mixed with the conductive carbon particles, and after being injected into a mold, is seamless by imidization reaction. It is formed into an annular shape having a width of 270 mm and a diameter of 80 mm. The thickness is 100 μm.

As shown in FIG. 1, a paper feed cassette 25 for accommodating paper P is provided in the vicinity of the transport means 11. The paper feed cassette 25 is provided with a pick-up roller 27 for picking up the sheets P one by one, as shown in the drawing, so as to be rotatable in the direction of arrow f. A registration roller pair 29 composed of an upper roller and a lower roller is rotatably provided on the front side of the transport unit 11 in the transport direction of the sheet P taken out by the pickup roller 27. The registration roller pair 29 transfers the sheet P to be conveyed,
The leading end of the developer image formed on the photosensitive drum 1a is
At the end of the transport means 11
Send to

The fed sheet P is conveyed to a suction roller 24 which is in contact with the conveying means and is grounded at a position facing the tension roller 13 with the conveying means 11 interposed therebetween. The suction roller is in contact with a SUS metal roller having a diameter of 6 mm. This may be a conductive rubber roller such as carbon-dispersed urethane rubber. Further, a conductive brush or a corona charger may be used.

The supply of the voltage to the suction roller 24 is performed by the power supply 4.
Perform by 1. The applied voltage was -1.5 kV. The higher the applied voltage for adsorption, the higher the amount of charge applied to the belt and the higher the attraction force, but it is at most about 3 kV in consideration of the limit of the withstand voltage of the belt material.

The suction roller 24 is a belt or paper P
It rotates following the conveyance direction of. At the same time as the paper P is conveyed to the suction roller section, a suction bias is applied. Thus, the surface of the sheet P is negatively charged, and the opposite side of the belt (the tension roller 13 side) is positively charged. The sheet P can be attracted by the electrostatic force generated by the charge.

As described above, the first photosensitive drum 1a, the charging roller 5a, the exposure unit 7a, the developing unit 9a, the blade cleaning device 17a, and the discharging lamp 19a are used for the first operation.
A process unit 100a is configured.

The tension roller 1 is placed on the conveying means 11.
3 between the drive roller 15 and the drive roller 15 along the transport direction.
In addition to the process unit 100a, a second process unit 100b, a third process unit 100c, and a fourth process unit 100d (hereinafter, process unit 100d)
a, process unit 100b, process unit 10
0c and the process unit 100d are collectively referred to as a process unit 100). The process unit 100b, the process unit 100c, and the process unit 100d
It has the same configuration as a. That is, the photosensitive drum 1
b, photoconductor drum 1c and photoconductor drum 1d (hereinafter, photoconductor drum 1a, photoconductor drum 1b, photoconductor drum 1c
And the photosensitive drum 1d are collectively referred to as the photosensitive drum 1). Around the photosensitive drum 1, a charging roller 5b, a charging roller 5c, and a charging roller 5d (hereinafter, charging roller 5a, charging roller 5b, charging roller 5c, and charging roller 5d are collectively referred to as charging roller 5) are provided. Have been.

On the downstream side of the charging roller 5, an exposure unit 7b, an exposure unit 7c, and an exposure unit 7d (hereinafter, an exposure unit 7a, an exposure unit 7
b, exposure unit 7c and exposure unit 7d are collectively referred to as exposure unit 7); developing unit 9b, developing unit 9c and developing unit 9d (hereinafter collectively referred to as developing unit 9a, developing unit 9b, developing unit 9c and developing unit 9d) To a developing device 9); blade cleaning device 1
7b, a blade cleaning device 17c and a blade cleaning device 17d (hereinafter referred to as a blade cleaning device 17a, a blade cleaning device 17b, a blade cleaning device 17c, and a blade cleaning device 1).
7d is collectively referred to as a blade cleaning device 17); a discharging lamp 19b, a discharging lamp 19c, and a discharging lamp 19d (hereinafter, a discharging lamp 19a and a discharging lamp 19).
b, the discharging lamp 19c and the discharging lamp 19d are collectively referred to as a discharging lamp 19). The configuration in which the developing unit 9a, 9b, 9
The developers provided in c and 9d are different from each other. The developing unit 9a of the process unit 100a has a yellow first color.
And the developing unit 9b of the process unit 100b has a second magenta developer and the process unit 100c.
The third developing device 9c accommodates a cyan third developer, and the developing device 9d of the process unit 100d accommodates a fourth developer of a black color.

At the time of outputting a color image, the sheet P conveyed by the conveying means 11 comes into contact with each of the photosensitive drums 1 sequentially. At a contact position between the sheet P and each of the photosensitive drums 1, a power supply roller 23 a as a transfer unit, a power supply roller 23
b, power supply roller 23c and power supply roller 23d (hereinafter, power supply roller 23a, power supply roller 23b, power supply roller 23c and power supply roller 23d are collectively referred to as power supply roller 23)
Are provided for each of the photosensitive drums 1 in a one-to-one correspondence. The power supply roller 23 is provided at a contact position between the corresponding photosensitive drum 1 and the transporting unit 11 so as to be in back contact with the transporting unit 11, and is provided via the transporting unit 11.
It is designed to face.

Here, an image forming process of the image forming apparatus thus configured will be described. First, the rotating photosensitive drum 1 of each of the four process units is contacted with a contact charging roller 5 to which an AC superimposed DC bias is applied.
To about -500V.

The photosensitive drum 1, which is uniformly charged by the charging roller, is irradiated with light from an exposure section 7 comprising a solid-state scanning head for performing exposure with a fluorescent material, and an electrostatic latent image is formed. The electrostatic latent image is developed by a developing device 9 with each developer sufficiently charged in advance for each color.

On the other hand, the paper P is taken out of the paper feed cassette 25 by the pickup roller 27 and sent to the registration roller pair 29. The pair of registration rollers 29
Photosensitive drum 1 so that the tip of the developer image comes to the tip of
After the rotation of the paper P and the timing, the paper P
Send it up.

When the paper P is transported to the transfer position of the first transfer station, a bias voltage is applied to the transport means 11 from the power supply roller 23. By applying a bias voltage, the photosensitive drum 1
And a transfer electric field is formed between them. Therefore, first, the first developer image on the photosensitive drum 1a is transferred onto the sheet P,
The sheet P carrying the first developer image is conveyed and reaches the photosensitive drum 1b. The second developer image formed on the photosensitive drum 1b is transferred so as to be superimposed on the previously transferred first developer image. The sheet P is further conveyed, and the third and fourth developer images are similarly transferred to the photosensitive drums 1c and 1d.

As described above, the sheet P carrying the image formed by the multiple transfer is sent from the conveying means 11 to the fixing device 33. The fixing device 33 is an oilless fixing device having a heating roller 35 and a pressure roller 37 each coated with a fluorine-containing resin and not supplying a release agent such as silicone oil. The paper P is passed between the heating roller and the pressure roller in a state where the image is in contact with the heating roller,
The image is fixed on the sheet P.

After the sheet P is separated from the transport means, the surface of the belt is cleaned by the blade cleaning 16.

FIG. 2 is a schematic diagram showing another example of the image forming apparatus according to the present invention.

In FIG. 2, a photosensitive drum 101 as an image bearing member is a cylindrical laminated organic photosensitive member having a diameter of 40 mm and a length of 266 mm, and is provided so as to be rotatable in the direction of an arrow as shown in the figure.

The following components are arranged around the photosensitive drum 101 along the rotation direction.

First, 5
Differential scanning comprising toner particles containing a polyester resin and a colorant having a glass transition point of 0 ° C. to 70 ° C. or less, and a metal oxide attached to the toner particles and having an average particle size of 30 nm to 1000 nm. An endothermic amount of 100 ° C. or less by a calorimeter of 25 J / g or less;
A developer in which the coverage of the metal oxide with respect to the toner particles is represented by the following formula: 4 ≦ coverage / 100 ° C. or less is stored.
Developing device 109 for developing the electrostatic latent image formed by
Is provided. Downstream of the developing device 109, for example, a roller-shaped transfer unit 111 that conveys and transfers a sheet as a recording material to the photosensitive drum 101 is a photosensitive drum 1.
It is provided so as to be rotatable in synchronization with 01. A blade cleaning device 117 and a static elimination lamp 119 are provided downstream of the photosensitive drum 101.
The blade cleaning device 117 removes the developer remaining on the photosensitive drum 101 after the transfer of the developer image by scraping off the developer using a blade (not shown). After the transfer, the charge removing lamp 119 is moved to the photosensitive drum 101.
This is a tungsten lamp that removes electricity from the surface of the substrate. One cycle of image formation is completed by the neutralization by the neutralization lamp 119. Next, when an image is formed, the uncharged photosensitive drum 101 is charged again.

In the vicinity of the transfer means 111, a paper cassette (not shown) for storing paper is provided. Sheets are conveyed from the sheet cassette in the direction of the arrow, and sent between the photosensitive drum 101 and the transfer unit 111.

As shown, the developing device 109 is divided into four sections, and each section includes a first developing section 109a and a second developing section 109a.
, A third developing unit 109c, and a fourth developing unit 109d. The developing unit 109 is rotatably provided so that the developing unit 109a, the developing unit 109b, the developing unit 109c, and the developing unit 109d can sequentially face the photosensitive drum 101. Each developing unit contains a first developer, a second developer, a third developer, and a fourth developer similar to those in the apparatus shown in FIG.

In the image forming apparatus having such a configuration, an image is formed as follows.

First, a bias voltage is applied to the photosensitive drum 101 by charging means (not shown),
01 is uniformly charged. Next, the photosensitive drum 1
A first electrostatic latent image is formed on the light emitting element 01 by light irradiation 107. A first developer image is formed by arranging the developing unit 109a to face the first electrostatic latent image and supplying the first developer.

When the sheet is conveyed to the transfer position, a bias voltage is applied to the transfer unit 111 from the power supply unit 137. By applying a bias voltage, a transfer electric field is formed between the photosensitive drum 101 and the transfer unit 111. First, the first developer image on the photosensitive drum 1 is transferred onto a sheet.

Thereafter, the first developer and the electric charge remaining on the photosensitive drum 101 are removed by the cleaning device 117 and the charge removing means 119, respectively.

A second electrostatic latent image is formed by light irradiation 107 on the photosensitive drum 101 from which the first developer and the charge have been removed. The developing device is rotated by ４, and the developing unit 109 b is opposed to the photosensitive drum 101.

In such a state, the second electrostatic latent image is
Is supplied to form a second developer image. Thereafter, a bias voltage is again applied to the transfer unit 111 from the power supply unit 137, and a transfer electric field is formed between the photosensitive drum 101 and the transfer unit 111 by applying the bias voltage. As a result, the second developer image on the photosensitive drum 101 is further transferred onto the sheet on which the first developer image has been transferred.

By repeating the same steps for the third developer and the fourth developer, the first to fourth developer images are laminated.

As described above, the sheet P carrying the image formed by the multiple transfer is conveyed in the direction of arrow 106 and
The toner is fed to an oilless fixing device having a heating roller 135 and a pressure roller 137 each coated with a fluorine-containing resin.
The sheet P is fixed on the sheet P by passing the image between the heating roller 135 and the pressure roller 137 in a state where the image is in contact with the heating roller 135.

A good image can be obtained by using any of the image forming apparatuses, and it can be seen that the developer of the present invention is sufficiently applicable to full-color image formation using an oilless fixing device.

[0070]

EXAMPLES Next, examples of the developer of the present invention will be shown, and the present invention will be described more specifically.

First, the following toner particle samples 1 to 6 were prepared.

Toner Particle Sample 1 First, 5% by weight of rice wax having a melting point Tm of 80 ° C., which begins to absorb heat at 70 ° C. or less, 4% by weight of an azo pigment, and a linear polyester resin having a glass transition point Tg of 60 ° C. After adding 1% by weight of a charge controlling agent CCA, which is a metal complex, and melt-kneading the resulting mixture, the obtained kneaded material is dried, coarsely pulverized, finely pulverized and classified to obtain an average of 8 μm. Toner particles 1 having a particle size were obtained.

Toner Particle Sample 2 Toner particles 2 were prepared in the same manner as in Sample 1 except that a polyethylene wax having a Tm of 110 ° C. which starts absorbing heat at 70 ° C. or higher was used instead of the rice wax.

Toner Particle Sample 3 A toner particle sample 3 was obtained in the same manner as in Sample 2, except that a linear polyester resin having a Tg of 75 ° C. was used as the polyester resin.

Toner Particle Sample 4 A toner particle sample 4 was obtained in the same manner as in Sample 2, except that the amount of rice wax added was 10% by weight.

Toner Particle Sample 5 A toner particle sample 5 was obtained in the same manner as in Sample 2, except that the amount of rice wax added was 20% by weight.

Toner Particle Sample 6 A toner particle sample 6 was obtained in the same manner as in Sample 1, except that the rice wax was not added.

Example 1 Toner particle sample 1 was mixed with 1.5% by weight of silica having an average particle size of 30 nm, and thoroughly mixed using a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) to obtain a toner. .

The obtained toner was measured for heat absorption at 100 ° C. or less using a differential scanning calorimeter.
It was 2 J / g.

FIG. 3 is a graph showing the results of measurement of the amount of heat absorbed by a differential scanning calorimeter.

Further, assuming that the coverage of the toner particles with the metal oxide is a true sphere having a particle diameter equal to the volume average particle diameter, the metal oxide is assumed to be a true sphere having a particle diameter equal to the primary particle diameter. It was determined by assuming.

Further, the obtained toner was calculated by applying the above results to the following equation (1).

Coverage% / (DSC endothermic amount at 100 ° C. or less [J / g]) (1) Further, the storage stability of the obtained toner was examined.

Toshiba Digital Copier Premage 241
Was modified, and an image of the obtained toner was output using an apparatus having a fixing device comprising a pair of elastic rollers coated with a fluorine-containing resin, and the transparency and the offset property were evaluated.

The offset property is determined by adjusting the temperature of the fixing device from 140 ° C.
The temperature was changed to 170 ° C. and confirmed visually. The case where no image defect due to offset was confirmed over the entire temperature range was evaluated as ○, and the case where it was confirmed was evaluated as x.

[0086] For the transparency, an image is output on an OHP sheet.
The transmittance of the solid portion at a transmission image density of 0.5 was measured with a spectrometer. A transmittance of 70% or more was evaluated as O, and a transmittance of less than 70% was evaluated as X. The transmittance of the non-image portion of the OHP sheet is 100
%.

As the storage stability, 20 g of the toner was put in a bottle, and the toner left for 1 hour in an environment of 60 ° C. was sieved with a mesh, and the remaining amount of the toner on the mesh was measured. Remaining 5
g and less than 5 g were evaluated as x.

The results obtained are shown in Table 1 below.

Examples 2 to 7, Comparative Examples 1 to 8 Toner particles were prepared by mixing toner particle samples and metal oxides shown in Table 1 below in the same manner as in Example 1. The obtained toner was measured and evaluated for heat absorption, coverage, storage stability, transparency and offset in the same manner as in Example 1. The results are shown in Table 1 below.

[0090]

[Table 1]

From Table 1 above, it can be seen from Comparative Examples 1, 2, 3 to 1
As shown in 0, it was found that when a developer outside the range of the present invention was used, the storage stability under high temperature and high humidity was poor.

Further, in Comparative Example 2, since the melting point of the wax used was high, the releasability was poor in the fixing step, and offset occurred.

In Comparative Example 3, the resin was not easily melted, so that high-temperature offset was hardly generated, and the storage stability was good. However, since the binder resin of the toner particles was not sufficiently melted, transparency was obtained. Did not.

Comparative Examples 1, 4, and 5 were excellent in both transparency and offset property, but were insufficient in storability because of the use of a resin and wax which are easy to melt. From Example 1, when the particle diameter of the metal oxide is 30 nm or more and the result of the expression 1 exceeds 4, the storage stability is improved.

According to Comparative Example 7, the particle size of the metal oxide was 30 n.
It was found that, even if m or more, when the result of Equation 1 was less than 4, sufficient storage stability improvement could not be obtained.

From Comparative Examples 1 and 6, it was found that even if the result of Formula 1 exceeds 4, if the particle size of the metal oxide is less than 30 nm, sufficient improvement in storage stability cannot be obtained.

On the other hand, as shown in Examples 1 to 10, it was found that when the developers of the present invention were used, all of them exhibited good storage stability.

From Example 10, it was found that the offset properties tended to be somewhat inferior unless a wax which started to absorb heat at 70 ° C. or lower was not used.

From Example 5, good results were obtained even with titanium oxide as the type of metal oxide. This is equivalent to a particle size of 30n
By adding 1% by weight or more of a metal oxide having a particle size of at least m, it is possible to reduce the chance of the resin portions of the toner coming into contact with each other and to prevent the toner from solidifying even when left at a high temperature. The same effect can be obtained regardless of the type of object. Therefore, in addition to silica and titanium oxide, any material such as alumina and zinc oxide can be used.

In Example 6, the amount of wax was increased and 1
When the heat absorption below 00 ° C. is increased to 22 J / g,
It was found that when the particle size of the metal oxide was 30 nm or more and the result of Expression 1 exceeded 4, the storage stability was improved.

In Comparative Example 9, when the amount of wax was increased and the heat absorption at 100 ° C. or less exceeded 25 J / g, the particle size of the metal oxide was 30 nm or more, and the result of the formula 1 was 4%. However, no improvement in storage stability was obtained even when the ratio exceeded the limit. When the heat absorption exceeds 25 J / g, it was found that the toner was greatly softened by leaving it at a high temperature, and it was difficult to improve with an external additive.

Table 2 below shows the coverage of toner particles with a metal compound and the fixing temperature.

[0103]

[Table 2]

From Table 2, it can be seen that it is necessary to increase the temperature of the fixing unit as the coverage increases due to the metal oxide. This is because the surface of the toner is covered with a metal oxide having a low thermal conductivity, and the amount of energy required for fixing increases as the coverage increases. When the coverage exceeds 90%, the phenomenon becomes remarkable. Therefore, the coverage is desirably 90% or less. However, even if it exceeds 90%, fixing is possible and does not deviate from the present invention.

[0105]

According to the present invention, it is possible to obtain a developer which has good high-temperature preservability and is applicable to oilless fixing. Further, when this developer is used, a high-quality image, in particular, an excellent full-color image can be formed.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram illustrating another example of the image forming apparatus of the present invention.

FIG. 3 is a graph showing a measurement result of an endothermic amount by a differential scanning calorimeter.

[Explanation of symbols]

1a, 1b, 1c, 1d, 101: photosensitive drums 5a, 5b, 5c, 5d: charging rollers 7a, 7b, 7c, 7d, 107: exposure units 9a, 9b, 9c, 9d, 109: developing units 17a, 17b , 17c, 17d ... blade cleaning devices 19a, 19b, 19c, 19d ... static elimination lamps 23a, 23b, 23c, 23d, 137 ... power supply means 33 ... fixing devices 35, 135 ... heating rollers 37, 137 ... pressure rollers 100a, 100b , 100c, 100d ... Process unit

Claims (5)

[Claims] 1. A toner particle containing a polyester resin having a glass transition point of 70 ° C. or lower and a colorant, and 30 nm to 1000 nm attached to the toner particle.
And a metal oxide having an average particle diameter of not more than 25 J / g by differential scanning calorimetry at 100 ° C. or less, and a coating ratio of the metal oxide to the toner particles is represented by the following formula: 4 ≦ coating Developer expressed as a ratio / heat absorption of 100 ° C. or less. 2. The developer according to claim 1, further comprising a wax which starts absorbing heat at 70 ° C. or lower. 3. The developer according to claim 2, wherein the wax is added in an amount of 2 to 20% by weight based on the total weight of the toner particles. 4. An electrostatic latent image forming step of forming an electrostatic latent image on an image carrier, wherein said electrostatic latent image is formed by toner particles containing a polyester resin having a glass transition point of 70 ° C. or lower and a colorant. And 30
a metal oxide having an average particle diameter of at least 100 nm, a heat absorption at 100 ° C. or less measured by a differential scanning calorimeter of 25 J / g or less, and a covering ratio of the metal oxide to the toner particles is represented by the following formula: ≦ Covering rate / Developing step of developing using a developer represented by an endothermic quantity of 100 ° C. or less, a transferring step of transferring the developed developer image onto a transfer-receiving material,
And a fixing step of fixing the developer image transferred onto the transfer material to the transfer material. 5. The method according to claim 4, wherein said fixing step is performed using an oilless fixing device.