JP2000066441A - Electrophotographic toner, image forming method and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrophotographic toner that does not cause central blanking and gives a good copied image. SOLUTION: The electrophotographic toner has <=35 nN mean value of non-electrostatic adhesive force to an electrophotographic photoreceptor measured by a powder adhesive force measuring method by centrifugal separation. The toner is obtd. particularly by coating toner matrix particles with >=0.2 wt.% additive such as fine silica particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electrophotographic toner, and an image forming method and apparatus using the same.

[0002]

2. Description of the Related Art Generally, in image formation by electrophotography,
First, the surface of the photoconductor is charged, and the charged photoconductor is exposed to an image to form an electrostatic latent image. Next, the electrostatic latent image is developed using an electrophotographic toner to form a toner image on a photoconductor. Further, by transferring and fixing the toner image on the photosensitive member, an image is formed on the transfer member. The toner remaining on the photoconductor after the transfer of the toner image is cleaned by a blade or the like.

In the above-described image forming process, the transfer process of the toner image has a great influence on the image quality. In recent years, contact type roller transfer and belt transfer have been used in the transfer process for improving image quality. In these transfer methods, electric charges can be applied only to a portion necessary for transfer, so that the edge shape is not easily disturbed by toner scattering. However, this method has a problem that since the toner image on the photosensitive member is pressed against the transfer member, a phenomenon of dropout of the image in which the toner remains on the photosensitive member easily occurs.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image processing apparatus using roller transfer and belt transfer without image defects.
An object of the present invention is to provide an electrophotographic toner capable of obtaining a good image, and an image forming method and an image forming apparatus using the toner.

[0005]

Means for Solving the Problems To solve the above-mentioned problems, the present inventors have investigated the non-electrostatic adhesion between an electrophotographic toner and an electrophotographic photosensitive member, which has an important effect on transfer characteristics. Paying attention, the relationship with the image defect was examined. As a result, it was measured by the powder adhesion measuring method by centrifugation,
The average value of the non-electrostatic adhesion to the electrophotographic photosensitive member is 35 nN
It has been found that the above object can be achieved by using the following electrophotographic toner, and the present invention has been completed. The non-electrostatic adhesive force between the electrophotographic toner and the electrophotographic photoreceptor is an adhesive force other than an electrostatic adhesive force such as a mirror image force generated by toner charging, and is a van der Waals force, a liquid bridge. Power.

According to the present invention, firstly, the average value of the non-electrostatic adhesion to the electrophotographic photosensitive member measured by the powder adhesion measuring method by centrifugation is 35 nN or less. Is provided.

Second, the electrophotographic toner particles comprise toner base particles and an external additive, and the coverage of the toner base particles with the external additive is 5% or more. An electrophotographic toner according to one aspect is provided. Here, the toner base particles are toners to which no external additives are added.

Third, the electrophotographic toner particles are composed of toner base particles and an external additive, and the amount of the external additive added to the toner base particles is 0.2% by weight or more. The electrophotographic toner according to the first or second aspect is provided.

Fourthly, there is provided the electrophotographic toner according to any one of the second to third aspects, wherein the external additive is silica fine particles.

Fifth, the volume average particle diameter of the electrophotographic toner particles is 5 to 15 μm.
An electrophotographic toner according to any one of the fourth to eleventh aspects is provided.

Sixth, there is provided the electrophotographic toner according to any one of the first to fifth aspects, wherein the electrophotographic toner is a non-magnetic toner.

Seventh, a latent image forming step of forming an electrostatic latent image on the photosensitive member, a developing step of forming a toner image on the latent image on the photosensitive member, and a step of transferring the formed toner image on a transfer member In an image forming method having a transfer step of transferring, there is provided an image forming method using the electrophotographic toner according to any one of the above first to sixth aspects.

Eighth, a latent image forming step of forming an electrostatic latent image on the photoreceptor, a developing step of forming a toner image on the latent image on the photoreceptor, and a step of transferring the formed toner image onto a transfer member In an image forming method having a transfer step of transferring, there is provided an image forming method using the electrophotographic toner according to any one of the above first to sixth aspects.

[0014]

In the transfer, the toner is moved from the photoreceptor to the transfer member by electrostatic force caused by an electric field. Since the transfer characteristics are determined by the relationship between the electrostatic and non-static adhesion of the toner and the electrostatic force due to the electric field, the control of the adhesion of the toner is an important factor in the transfer design. When roller transfer or belt transfer is used, the toner image on the photoreceptor is pressed against the transfer member, so that the adhesion between the toner and the photoreceptor and the adhesion between toner particles / toner particles are increased, and the toner is transferred to the transfer member. It is likely to remain on the photoreceptor without being transferred. This phenomenon is particularly likely to occur at the center of a thin line portion where pressure is easily applied, and image dropout occurs. For this reason, in order to improve image dropout, it is necessary to reduce the adhesive force between the toner and the photoconductor and the adhesive force between toner particles / toner particles or the pressure applied between the photoconductor and the transfer member.

Among the adhesive forces between the toner and the photosensitive member, the electrostatic adhesive force depends on the charge amount of the toner, and can be reduced by reducing the charge amount. However, if the charge amount of the toner is too small, the toner cannot be transferred by electrostatic force due to an electric field. For this reason, the present inventors have examined the relationship between image defects and the non-electrostatic adhesion force among the adhesion forces between the toner and the photoconductor. As a result, by using a toner having a non-electrostatic adhesive force between the toner and the photoreceptor measured by the powder adhesive force measuring method by centrifugal separation of 35 nN or less, it is possible to improve image dropout. I found what I could do.

First, an apparatus for measuring the powder adhesion by centrifugation will be briefly described. FIG.
FIG. 3 is an explanatory view of a measuring cell of the powder adhesion measuring device. In FIG. 1, reference numeral 1 denotes a measuring cell. The measuring cell 1 has a sample substrate 2 having a sample surface 2a on which powder is adhered, and a receiving substrate 3 having an adhering surface 3a on which powder separated from the sample substrate 2 is adhered. 3 and a spacer 4 provided between the sample surface 2 a of the sample substrate 2 and the attachment surface 3 a of the receiving substrate 3.

FIG. 2 is a partial sectional view of a centrifugal separator of the powder adhesion measuring device. In FIG. 2, reference numeral 5 denotes a centrifugal separator, and the centrifugal separator 5 includes a rotor 6 for rotating the measurement cell 1 and a holding member 7. The rotor 6 has a hole shape in a cross section perpendicular to its own rotation center axis 9, and has a sample setting section 8 on which the holding member 7 is set. The holding member 7 includes a rod-shaped portion 7a, a cell holding portion 7b provided on the rod-shaped portion 7a for holding the measurement cell 1, a hole 7c for pushing the measurement cell 1 out of the cell holding portion 7b, and a rod-shaped portion 7a. 8 is provided. When the measurement cell 1 is installed, the cell holding unit 7b
Is perpendicular to the rotation center axis 9 of the rotor. Further, the sample substrate 2, the receiving substrate 3, the spacer 4, and the holding member 7 have strength enough to withstand a large centrifugal force, and when installed on the rotor 6, the weight is equal to or less than the weight capable of rotating up to the maximum rotation speed of the centrifugal separator. It is necessary to use a lightweight material such that

Next, a method for measuring the non-electrostatic adhesion of toner using the above-described apparatus will be described. First, a film-shaped photoconductor is manufactured, processed according to the shape of the sample substrate 2, and attached to the sample substrate 2 with an adhesive. Next, the uncharged toner is naturally dropped and adhered onto the photoreceptor (sample surface 2a) attached to the sample substrate 2. Next, as shown in FIG. 1, the measurement cell 1 is configured by using the sample substrate 2, the receiving substrate 3, and the spacer 4. The cell holding of the holding member 7 is performed such that the sample substrate 2 is located between the receiving substrate 3 and the rotation center axis 9 of the rotor 6 when the holding member 7 is set on the sample setting portion 8 of the rotor 6. Installed in the section 7b. The holding member 7 is set on the sample setting section 8 of the rotor 6 such that the vertical direction of the measurement cell 1 is perpendicular to the rotation center axis 9 of the rotor. The centrifugal separator 5 is operated to rotate the rotor 6 at a constant speed. The toner adhered to the sample substrate 2 receives a centrifugal force according to the number of rotations. If the centrifugal force received by the toner is larger than the adhesive force between the toner and the sample surface 2a, the toner separates from the sample surface 2a and Attaches to 3a.

The centrifugal force F received by the toner is obtained from equation (1) using the weight m of the toner, the number of rotations f (rpm) of the rotor, and the distance r from the center axis of the rotor to the toner adhering surface of the sample substrate. Can be The gravity m of the toner is obtained from Expression (2) using the true specific gravity ρ of the toner and the equivalent circle diameter d. m = (π / 6) × ρ × d ³ (2) From the equations (1) and (2), the centrifugal force F received by the toner is:
It is obtained from equation (3). ^{F = (π 3/5400)} × ρ × d 3 × r × f 2 (3)

After the centrifugation, the holding member 7 is taken out of the sample setting section 8 of the rotor 6, and the cell holding section 7 of the holding member 7 is removed.
Take out the measuring cell 1 from b. The receiving substrate 3 is replaced, the measuring cell 1 is set on the holding member 7, and the holding member 7 is
And the rotor 6 is rotated at a higher rotational speed than the previous time. The centrifugal force received by the toner becomes larger than the previous time, and the toner having a large adhesive force separates from the sample surface 2a and adheres to the adhesive surface 3a. By performing the same operation by changing the set rotation speed of the centrifugal separator from a low rotation speed to a high rotation speed, the toner on the sample surface 2a is changed according to the magnitude relationship between the centrifugal force and the adhesion force received at each rotation speed. Moves on the attachment surface 3a.

After the centrifugal separation is performed for all the set rotation speeds, the particle diameter of the toner adhered to the adhesion surface 3a of the receiving substrate 3 at each rotation speed is measured. You can determine the strength. Since the adhesion of each toner is measured, by performing statistical processing,
The distribution and average value of the adhesive force of the toner adhered to the sample surface 2a can be obtained. The particle diameter and the number of the toner were measured by observing the toner on the adhesion surface 3a with an optical microscope, and capturing the image into a computer through a CCD camera.
This can be done using image processing software.

Non-electrostatic adhesion between toner and photoreceptor is 35n
In order to obtain a toner of N or less, it is necessary to control the coverage of the toner additive with the external additive. The coverage of the external additive is defined by the area of the external additive fine particles occupying the surface area of the toner matrix, and can be measured by image analysis of an electron micrograph of the toner. FIG.
The relationship between the external additive coverage and the non-electrostatic adhesion when using silica fine particles as the external additive is shown below. As shown in FIG. 3, the non-electrostatic adhesive force tends to decrease and saturate as the external additive coverage increases. From FIG. 3, in order to obtain a toner in which the non-electrostatic adhesion between the toner and the photoreceptor is 35 nN or less, it is necessary to set the external additive coverage to 5% or more.

FIG. 4 shows the relationship between the amount of the external additive added to the toner base and the external additive coverage. As shown in FIG.
The external additive coverage tends to increase with the amount of the external additive added and saturate. From FIG. 4, it is necessary to make the additive amount of the external additive 0.2% by weight or more in order to make the external additive coverage rate 5% or more. The upper limit of the amount of the external additive is not particularly limited in the present invention. However, even if the external additive is added in an amount of 3% by weight or more, the external additive coverage does not increase as shown in FIG. The amount of the external additive which is released from the toner matrix and adheres to the photoreceptor or the carrier increases without adhering to the toner. Therefore, the amount of the external additive is preferably 3% by weight or less.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As the electrophotographic toner of the present invention, conventionally known toners having various constitutions can be used. As an example of a preferable toner, additives such as a colorant, a charge control agent, and a release agent (anti-offset) are blended into a fixing resin, granulated to an appropriate particle size, and an external additive is added thereto. Is added.

The particle diameter of the electrophotographic toner of the present invention is suitably from 5 to 15 μm in volume average particle diameter, and about 5 to 10 μm in the case of small particle diameter toner. Further, the toner for electrophotography of the present invention can be used alone as a magnetic toner.
Although it can be used as a magnetic toner used as a component toner, it is preferably used alone as a non-magnetic one-component developer or used as a non-magnetic toner that constitutes a magnetic two-component developer with a magnetic carrier. .

The resins used in the present invention include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene and isobutylene;
Vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate, methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, dodecyl acrylate, phenyl acrylate, methyl methacrylate, and ethyl methacrylate Esters of α-methylene aliphatic monocarboxylic acids such as butyl methacrylate, dodecyl methacrylate, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, etc. Homopolymers and copolymers of vinyl ketones and the like can be exemplified. Particularly typical resin resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, and polystyrene. Len - acrylonitrile copolymer, styrene - butadiene copolymer, styrene - can be exemplified maleic anhydride copolymer, polyethylene, polypropylene or the like. Further, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax and the like can be mentioned.

Examples of the coloring agent include carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, copper phthalocyanine, malachite green oxalate, lamp black, rose bengal, Titanium oxide, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 122, C.I.
I. Pigment Red 57: 1, C.I. I. Pigment Yellow 97, C.I. I. Pigment Yellow 12,
C. I. Pigment Yellow 17, C.I. I. Pigment Blue 15: 1, C.I. I. Pigment Blue 1
5: 3 and the like. The colorant is used in an amount of 1 to 30 parts by weight based on 100 parts by weight of the fixing resin.

There are two types of charge control agents for controlling positive charge and for controlling negative charge, depending on the charge polarity of the toner. Examples of the charge control agent for controlling the positive charge include oil-soluble dyes such as nigrosine base (CI5045) and organic compounds having a basic nitrogen atom, for example, basic dyes, aminopyrine,
Examples include pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, and fillers surface-treated with the above compounds. As the charge control agent for negative charge control,
Oil-soluble dyes such as oil black (CI26150), Bontron S and Spiron Black; charge controlling resins such as styrene-styrene sulfonic acid copolymer; compounds containing a carboxy group (for example, metal chelates of alkyl salicylic acid), metal complex salts Dyes, fatty acid metal soaps, resin acid soaps, metal naphthenates and the like. The charge control agent is used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the fixing resin.

Examples of the release agent include aliphatic hydrocarbons, aliphatic metal salts, higher fatty acids, fatty acid esters or partially saponified products thereof, silicone oil, various waxes and the like. The release agent is used in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the fixing resin.

The toner is kneaded with a mixture obtained by homogeneously pre-kneading the above components by a dry blender, a Henschel mixer, a ball mill or the like, for example, a kneading device such as a Banbury mixer, a roll, a single-screw or twin-screw extrusion kneader. After melt-kneading uniformly using, the obtained kneaded material is cooled, pulverized, and classified if necessary. In addition, it can also be produced by a known production method such as a polymerization method such as a suspension polymerization method, a microcapsule polymerization method, or a spray drying method.

As the external additive used in the present invention, organic fine particles can be used.
In particular, silica fine particles are preferably used. The average particle diameter of the external additive fine particles is in the range of about 3 nm to 1 μm, preferably in the range of 5 nm to 200 nm.

Next, an image forming method and an image forming apparatus of the present invention will be described. An image forming method according to the present invention includes a latent image forming step of forming an electrostatic latent image on a photoreceptor, a developing step of forming a toner image on the latent image on the photoreceptor, and forming the formed toner image on a transfer body. And a transfer step of transferring onto a transfer member. An image forming apparatus according to the present invention includes: a latent image forming unit that forms an electrostatic latent image on a photoreceptor; a developing unit that forms a toner image on the latent image on the photoreceptor; And a transfer means for transferring the image onto a transfer member.

As the electrophotographic photoreceptor, those having a charge generation layer and a charge transport layer formed on a conductive support, and those having a protective layer formed on the charge transport layer and the like are used. As the conductive support and the charge generation layer, any known materials can be used.

The formation of the electrostatic latent image on the photosensitive member may be performed by a known latent image forming process. The formed electrostatic latent image is visualized by developing any one of the first to sixth electrophotographic toners in a known developing step. In the transfer step, the toner image formed on the photoconductor is transferred onto the transfer body by a known method, and a copied image is formed by fixing. In the transfer process of the present invention, an electric charge can be applied only to a portion necessary for the transfer, and an adhesive roller transfer method and a belt transfer method that are less likely to disturb the edge shape due to toner scattering are used.

[0035]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Parts here are by weight.

Example 1 Polyester resin (weight average molecular weight 250,000) 80 parts Styrene-methyl methacrylate copolymer 20 parts Rice wax 5 parts Carbon black (manufactured by Mitsubishi Kasei Kogyo Co., Ltd., # 44) 8 parts Metal-containing monoazo dye 3 Part After sufficiently mixing the mixture having the above composition in a Henschel mixer, the mixture is rolled at a temperature of 130 to 140 ° C. for about 3 hours.
After heating and melting for 0 minutes and cooling to room temperature, the obtained kneaded product was pulverized and classified by a jet mill to obtain toner base particles having a particle size of 5 to 20 μm and a volume average particle size of 9 μm. The toner base particles and the silica fine particles were blended so that the addition amount of the silica fine particles was 0.2% by weight of the toner amount, and the mixture was stirred and mixed by a Henschel mixer to prepare an electrophotographic toner.

Example 2 The toner base particles and the silica fine particles of Example 1 were blended so that the added amount of the silica fine particles was 0.5% by weight of the toner amount, and the mixture was stirred and mixed with a Henschel mixer to perform electrophotography. A toner was prepared.

Example 3 The toner base particles and the silica fine particles of Example 1 were blended so that the added amount of the silica fine particles was 1.0% by weight of the toner amount, and the mixture was stirred and mixed with a Henschel mixer to perform electrophotography. A toner was prepared.

Example 4 The toner base particles and the silica fine particles of Example 1 were blended so that the added amount of the silica fine particles was 2.0% by weight of the toner amount, and the mixture was stirred and mixed with a Henschel mixer to perform electrophotography. A toner was prepared.

Example 5 The toner base particles and the silica fine particles of Example 1 were blended so that the added amount of the silica fine particles was 3.0% by weight of the toner amount, and the mixture was stirred and mixed with a Henschel mixer to perform electrophotography. A toner was prepared.

Comparative Example 1 The toner base particles of Example 1 were used as an electrophotographic toner.

Comparative Example 2 The toner base particles and silica fine particles of Example 1 were blended so that the added amount of the silica fine particles was 0.1% by weight of the toner amount, and the mixture was stirred and mixed with a Henschel mixer to perform electrophotography. A toner was prepared.

(Measurement of Adhesion) Examples 1 to 5 and Comparative Examples 1 and 2 were obtained by the particle adhesion measurement method by centrifugation described above.
The average value of the non-electrostatic adhesion of the toner for electrophotography was measured. The photoreceptor used for the measurement was an electrophotographic copying machine (Imagi, manufactured by Ricoh Co., Ltd.) on a polymer film on which Al was deposited.
o MF200) was used.
Table 1 shows the measurement results. The equipment used for the measurement is as follows. Centrifugal separator: Hitachi Koki CP100α (Maximum speed:
100,000 rpm, Maximum acceleration: 800,000 × g, Angle rotor P1
00AT) Image processing device: Hyper700 manufactured by Interquest

(Measurement of external additive coverage) The surface of the toner treated with the silica fine particles was photographed using an electron microscope, the image was taken into a personal computer, and image analysis software (image) was used.
ProPlus), and the external additive coverage was measured. Table 1 shows the measurement results.

(Copy Test) The toner for electrophotography of each of Examples 1 to 5 and Comparative Examples 1 and 2 was combined with a carrier for an electrophotographic copying machine (Imagio MF200, manufactured by Ricoh Co., Ltd.)
A two-component developer was prepared by blending so that the toner concentration was 5.0% by weight. The image quality of each developer was evaluated using the above-mentioned copying machine. Table 1 shows the test results. In Table 1, the signs in the copy test column indicate the following states, respectively. : No void ×: With void

From the results in Table 1, it can be seen that the toner of Comparative Example 1 to which no external additive was added and the toner of Comparative Example 2 to which the external additive addition amount was 0.1% by weight and the external additive coverage was 10% or less. In each of the samples, the non-electrostatic adhesion was 35 nN or more, and hollowing occurred. In contrast, Examples 1 to 5 in which the additive amount of the external additive was 0.2% by weight or more, the external additive coverage was 5% or more, and the non-electrostatic adhesion was 35 nN or less were all medium. A good copy image could be formed without dropout.

[0047]

[Table 1]

[0048]

According to the use of the electrophotographic toner of the present invention, it is difficult to cause image dropout during transfer. According to the image forming method using this toner, the transfer roll is used in the transfer step. Even when a belt-like intermediate transfer member is used, it is possible to obtain an image with no image defects and with good image quality without image quality deterioration due to poor transfer.

[Brief description of the drawings]

FIG. 1 is an explanatory view of one embodiment of a measuring cell of a powder adhesion measuring device according to the present invention.

FIG. 2 is a partial cross-sectional side view of a centrifugal separator of the powder adhesion measuring device according to the present invention.

FIG. 3 is a diagram illustrating a relationship between a non-electrostatic adhesion between a toner and a photoconductor and an external additive coverage.

FIG. 4 is a graph showing the relationship between the external additive coverage and the amount of external additive added.

[Explanation of symbols]

 Reference Signs List 1 measurement cell 2 sample substrate 2a sample surface 3 receiving substrate 3a attachment surface 4 spacer 5 centrifugal separator 6 rotor 7 holding member 7a rod-shaped portion 7b cell holding portion 7c hole 7d installation fixing portion 8 sample installation portion 9 rotation center axis

Claims (8)

[Claims] 1. An electrophotographic toner, wherein an average value of non-electrostatic adhesion to an electrophotographic photosensitive member measured by a method for measuring powder adhesion by centrifugation is 35 nN or less. 2. The toner according to claim 1, wherein the toner particles for electrophotography comprise toner base particles and an external additive, and the coverage of the toner base particles with the external additive is 5% or more. Electrophotographic toner. 3. The toner particles for electrophotography comprise toner base particles and an external additive, and the amount of the external additive added to the toner base particles is 0.2% by weight or more. 3. The electrophotographic toner according to 1 or 2. 4. The electrophotographic toner according to claim 2, wherein the external additive is silica fine particles. 5. The electrophotographic toner according to claim 1, wherein the volume average particle diameter of the electrophotographic toner particles is 5 to 15 μm. 6. The electrophotographic toner according to claim 1, wherein the electrophotographic toner is a non-magnetic toner. 7. A latent image forming step of forming an electrostatic latent image on a photosensitive member, a developing step of forming a toner image on the latent image on the photosensitive member, and transferring the formed toner image onto a transfer member. 7. An image forming method having a transfer step, wherein the electrophotographic toner according to claim 1 is used. 8. A latent image forming means for forming an electrostatic latent image on a photosensitive member, a developing means for forming a toner image on the latent image on the photosensitive member, and transferring the formed toner image onto a transfer member. An image forming apparatus having a transfer unit, wherein the electrophotographic toner according to claim 1 is used.