JPH08339094A - Electrophotographic toner - Google Patents

Abstract

PURPOSE: To obtain an electrophotographic toner having superior transferability and satisfactory ability of cleaning. CONSTITUTION: This electrophotographic toner is a mixture of an amoprhous toner with a spherical toner, the volume average particle diameter of the amorphous toner is larger than that of the spherical toner and the spherical toner is mixed by <=5wt.%. When the area of a circule having the absolute max. length of the toner particles of the spherical toner as the diameter is represented by Sc and the average practical projection area of the toner particles is represented by Sr, the value of Sc/Sr is in the range of 1.0-1.5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner used in a developing device such as an electrophotographic device or an electrostatic recording device.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic apparatus has mainly been a device using toner which is a dry developer, and has been put into practical use as many copying machines, laser printers, plain paper facsimiles, etc., and has made remarkable progress.

This type of electrophotographic apparatus is an apparatus to which electrophotographic process technology is applied, and visualizes an electrostatic latent image formed on an electrostatic latent image carrier with toner. Hereinafter, the configuration of the electrophotographic apparatus will be described in detail with reference to FIG.

As shown in FIG. 1, a metal drum made of aluminum or the like is used as a base material, and a thin film is formed on the outer peripheral surface thereof by a photosensitive receiving layer such as selenium (Se) or an organic photoconductor (hereinafter referred to as OPC). A charging device 2 is disposed in close proximity to the photoconductor 1 which is the electrostatic latent image carrier. The charger 2 is composed of a charging wire 2a such as a tungsten wire, a metal shield plate 2b, and a grid plate 2c. The charging line 2a causes corona discharge to uniformly charge the photoconductor 1 through the grid plate 2c. Then, an exposure light beam 4 from the exposure optical system 3 is formed on the charged photoreceptor 1.
To form an electrostatic latent image. In addition, this exposure light beam 4
Is obtained by light intensity modulation or pulse width modulation of the image signal by a laser drive circuit (not shown). The toner supply roller 6 is attached to the developing hopper 9 by a toner agitating member 11 which is rotatably supported at both ends and is bent in a rectangular shape.
The agitated and conveyed toner 10 is supplied to the surface of the developing roller 5 which is a toner carrier. The developing roller 5 and the toner supply roller 6 are made of metal such as stainless steel as a base material, and elastic members such as urethane and silicon are formed in layers on the outer peripheral surfaces thereof, and are rotatably supported at both ends of the developing hopper 9. The toner 10 supplied from the toner supply roller 6 is frictionally charged by the toner regulating blade 7,
A thin layer state is formed on the outer peripheral surface of the developing roller 5. Thereafter, the developing roller 5 is brought into contact with or close to the photoconductor 1, and the bias voltage applied from the developing bias power source 12 causes the toner 10 to be transferred and attached to a portion of the photoconductor 1 where the electrostatic latent image is formed. Visualize the electric latent image. The toner regulating blade 7 is composed of a metal spring plate member 7a and a toner regulating member 7b which comes into contact with the developing roller 5, and the toner regulating member 7b has urethane or silicone or the like at one end of the metal spring plate member 7a. The elastic member is integrally formed. The toner regulation blade 7 is attached by a blade holder 8 with screws. The toner stirring member 11 draws a circular locus along with the rotation of the toner supply roller 6, and is stirred to prevent the toner 10 contained in the developing hopper 9 from aggregating and conveys the toner 10 to the toner supply roller 6. .

A cleaning blade 14 for scraping off the residual toner on the photosensitive member 1 in the toner collecting vat 13.
And a static eliminator 15 is attached. The cleaning method for this electrophotographic apparatus is called a blade cleaning method. The sheets 17 stored in the sheet cassette 16 are sent out from the sheet cassette 16 one by one to the conveying roller 19 by the half-moon-shaped sheet feeding roller 18. The sheet 17 sent out is conveyed by the conveyance roller 1
It is conveyed in the direction indicated by arrow A by 9. And
The sheet 17 is temporarily stopped and waited on the photoconductor 1 by the register roller 20 which is in contact with the driven roller 21 so as to match the toner image formed on the photoconductor 1. The transfer device 22 includes a transfer line 22a made of a tungsten wire or the like and a shield plate 22b made of a metal plate. When a high voltage is applied to the transfer line 22a, corona discharge occurs, and the toner image on the photoconductor 1 is transferred onto the paper 17. The toner image transferred onto the sheet 17 is gripped and rotated by the heat roller 24 and the pressure roller 25, which have a heat source inside and are formed in the fixing device 23, and
It is fixed by pressure and heat.

The toner 10 used in the electrophotographic apparatus described above was produced by the pulverization method and had irregular toner particles, and had a number average particle diameter of about 7 μm.

[0007]

With the increase in resolution and image quality of electrophotographic apparatuses, there is a tendency that toner particles having a smaller particle size are used. This is because reducing the particle size of the toner is advantageous for scattering characters and reproducing fine dots.

However, the conventional toner has the following shape.
There are irregular toners and spherical toners having a true spherical shape, but toners having these two shapes have problems. For example, in the case of an irregular toner, there is a problem that the transfer efficiency is lowered due to excessive charging due to a reduction in particle size, and in the case of a spherical toner, the toner is reduced by the conventional blade cleaning method. There is a problem that cleaning failure occurs by passing under the blade.

The present invention solves the above problems, and an object of the present invention is to provide an electrophotographic toner having both excellent transferability and good cleaning property.

[0010]

The toner for electrophotography according to claim 1 is a toner for converting an electrostatic latent image on a latent electrostatic image bearing member into a visible image by being carried by a toner bearing member. It is characterized in that the regular toner and the spherical toner are mixed.

The toner for electrophotography according to claim 2 is the toner according to claim 1.
In the volume average particle diameter of the irregular toner D _1, when the volume average particle diameter of the spherical toner and D _2, characterized in that a relationship of D _1> D _2.

A third aspect of the present invention is the electrophotographic toner according to the first and second aspects, wherein the mixing ratio of the spherical toner is 15% or less by weight. The electrophotographic toner according to claim 4 is the spherical toner according to any one of claims 1, 2, and 3, wherein the area of a circle having the absolute maximum length of the toner particle as a diameter is Sc, and the substantial projected area of the toner particle is Sr is in the range of 1.0 ≦ Sc / Sr ≦ 1.5.

[0013]

According to this structure, by mixing the irregular toner and the spherical toner, excellent transferability and good cleaning property can be obtained.

[0014]

Embodiments of the present invention will be described below. (First Example) An amorphous toner is a styrene-based copolymer in which a charge control agent and a release agent are added and kneaded, and then pulverized and classified, and hydrophobic silica is externally added as a fluidizing agent. The particle size was 7 μm. The spherical toner was produced by a known technique, that is, a suspension polymerization method using a styrene monomer, and had a volume average particle diameter of 6 μm. In order to confirm the spherical degree of the spherical toner, the area of a circle whose diameter is the absolute maximum length of the toner particle is Sc, and the substantial projected area of the toner particle is S.
When r, the value of Sc / Sr was always within the range of 1.0 to 1.5. This Sc / Sr shows 1.0 in the case of a true sphere, and the larger the irregular and complicated shape, the larger the value. next,
95% by weight of irregular toner and 5% by weight of spherical toner were mixed in a mixer to obtain an electrophotographic toner.

(Second Embodiment) An amorphous toner and a spherical toner similar to those in the first embodiment are used in an amorphous toner 85 in a weight ratio.
%, And spherical toner 15% in a mixing machine to obtain an electrophotographic toner.

(Comparative Example 1) The same as the first embodiment except that the mixing ratio of the amorphous toner and the spherical toner is the same as that of the first embodiment except that the amorphous toner is 80% and the spherical toner is 20% by weight. Similarly, a toner for electrophotography for comparison was obtained.

Comparative Example 2 A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that spherical toner having a volume average particle size of 8 μm was used.

(Comparative Example 3) A comparative electrophotographic toner was obtained in the same manner as in the first example except that the toner was composed of the same amorphous toner as in the first example.

(Comparative Example 4) A comparative electrophotographic toner was obtained in the same manner as in the first example, except that only the same spherical toner as in the first example was used.

With respect to the electrophotographic toners of the first embodiment, the second embodiment and the comparative examples 1 to 4 formed as described above, the transferability and cleaning properties were tested.
The determination results are shown in Table 1 and described below.

[0021]

[Table 1] (Experimental Example 1) Using each of the electrophotographic toners obtained in the above Examples and Comparative Examples, the transfer efficiency was measured to confirm the transferability. Hereinafter, detailed conditions will be described with reference to FIG.

Further, since the electrophotographic apparatus shown in FIG. 1 is the same apparatus as the conventional electrophotographic apparatus, the same reference numerals will be used for the elements common to the constituent elements. The photoconductor 1, the developing roller 5, and the toner supply roller 6 rotate in the directions of the arrows shown in FIG. 1, and the respective contact portions are in frictional contact. Toner supply roller 6
Is an insulating foam formed around a metal shaft. The toner supply roller 6 has a function of supplying the toner 10 to the developing roller 5 and also scraping off the toner 10 remaining on the developing roller 5 without being developed.

The developing roller 5 has a single-layer structure in which a metal shaft is used as a base material and silicon rubber which is a conductive elastic member having a resistance value of 10 ⁶ Ωcm is formed on the outer peripheral surface thereof. The rubber hardness of the developing roller 5 is preferably in the range of 30 to 60 degrees, and the surface roughness is preferably 7 μmRz or less because the higher the surface smoothness is, the more uniform the toner thin layer can be formed. In this experimental example, the developing roller 5 had a rubber hardness of 40 degrees and a surface roughness of 3 μmRz.

The toner regulating blade 7 is a stainless steel plate,
An elastic metal spring plate member 7a such as a phosphor bronze plate is integrally formed with urethane rubber having a rubber hardness of 60 degrees, which is an elastic member, as a toner regulating member 7b at one end thereof, and is screwed to the blade holder 8 at three positions. Has been done. The toner regulating member 7b presses the developing roller 5 with a linear pressure of 80 g / cm to form a toner layer of 0.5 mg / cm ^{2 on} the surface of the developing roller 5. In the non-magnetic-component contact developing system as in the present experimental example, the toner layer on the developing roller is 0.3 to
The range of 0.6 mg / cm ² is preferred.

The electrophotographic process conditions for printing are as follows: the process speed is 76 mm / sec, the photosensitive member 1 is a negative charging type OPC, and the developing roller 5 has a peripheral speed of 152 mm / s.
In ec, the peripheral speed ratio with respect to the photoconductor 1 is double, and the peripheral speed of the toner supply roller 6 is 105 mm / sec. Photoconductor 1
Is uniformly charged to -700V, the developing bias applied to the developing roller 5 is -300V, and the voltage applied to the transfer line 22a is 4kV.

In the above structure, the transfer efficiency is measured by determining the image signal input to the exposure optical system 3 so that the image density after fixing is a solid image of 1.6, and transferring under the exposure conditions. The amount of toner adhered on the photoconductor 1 before and the amount of toner adhered on the paper 17 after transfer were measured.

Table 1 shows the transfer efficiency and the judgment results of the electrophotographic toners shown in the examples and the electrophotographic toners of the comparative examples. Generally, a transfer efficiency of about 90% is required. Therefore, if the transfer efficiency is 90% or more, the judgment is ◯, 90%.
Those less than are indicated by x.

From the results shown in Table 1, it is understood that the transfer efficiency is 90% or more except for Comparative Example 3, which is composed of only the irregular toner, and is at a practical level. It is considered that this is because, in consideration of the determination results, the spherical toners having excellent transferability are included except for Comparative Example 3. From the above,
Regarding transferability, it was found that excellent transferability can be obtained by mixing spherical toner regardless of the mixing ratio and toner particle size.

(Experimental Example 2) Next, using each of the electrophotographic toners obtained in Examples and Comparative Examples, the cleaning property was confirmed. Hereinafter, an experimental example and the determination result thereof will be described with reference to FIG.

The cleaning property is measured by image density of 1.0.
The solid image was formed on the photosensitive member 1, cleaning was performed without transferring the paper, the residual toner 10 after the cleaning was peeled off with an adhesive tape, and the cleaning property (whiteness) of the toner 10 was measured. The larger the value of this cleaning property (whiteness), the more difficult the cleaning is.

Table 1 shows the cleaning properties (whiteness) and the judgment results of the examples and comparative examples. The judgments are indicated by ◯ for those of 2.0 or less, Δ for those of 2.0 to 5.0, and x for those of 5.0 or more.

From the results shown in Table 1, it can be seen that if the mixing ratio of the spherical toner is large and the volume average particle diameter of the spherical toner is larger than the volume average particle diameter of the irregular toner, the cleaning property tends to deteriorate. Considering from the measurement results, this is because when the mixing ratio of the spherical toner increases, the ratio of the spherical toner particles that are not integrated with the irregular toner particles increases and that the volume average particle system of the irregular toner It is considered that this is because when the volume average particle diameter of the spherical toner becomes large, the characteristics of the spherical toner passing through the cleaning blade become remarkable. Therefore, in order to realize good cleaning property, it is necessary to make the volume average particle diameter of the spherical toner larger than the volume average particle diameter of the irregular toner when the mixing ratio of the spherical toner is 15% or less.

As described above, in the measurement results of Experimental Examples 1 and 2, it was confirmed that when the irregular toner and the spherical toner are mixed, the transfer efficiency is excellent and the cleaning property is good.

When the volume average particle diameter of the irregular toner is D ₁ and the volume average particle diameter of the spherical toner is D ₂ , at least D ₁ > D ₂ and the mixing ratio of the spherical toner is 15%.
In the following, the spherical toner has a Sc / Sr value in the range of 1.0 to 1.5, where Sc is the area of a circle whose diameter is the absolute maximum length of the toner particles and Sr is the substantial projected area of the toner particles. It can be seen that the formed electrophotographic toner has excellent transfer efficiency and good cleaning property. this is,
It is considered that when the irregular toner and the spherical toner are mixed under the above conditions, the irregular toner particles and the spherical toner particles are integrated by the electrostatic adhesive force. Therefore, the characteristics of the spherical toner during transfer and the characteristics of the irregular toner during cleaning become remarkable.

The spherical toner used here was prepared by a suspension polymerization method using a styrene-based monomer, but particles obtained by emulsion polymerization method or pulverization were spherically processed by a method such as heating. But it's okay. In the present invention, the non-magnetic one-component developing system is used, but the same effect can be obtained by applying it to the magnetic one-component developing system, the two-component developing system and the like.

Furthermore, the present invention is an electrophotographic toner particularly suitable for a toner recycling system, which improves the fluidity of the residual toner on the photoconductor 1 after transfer, and collects it again in the toner hopper by this effect. The change in the fluidity of the generated toner is small, and the print quality is stabilized.

[0037]

According to the constitution of the present invention, since the amorphous toner and the spherical toner are mixed, it is possible to provide an electrophotographic toner having excellent transferability and good cleaning property.

Further, the volume average particle diameter D _{1 of} the irregular toner,
The volume average particle diameter D ₂ of the spherical toner has a relationship of D ₁ > D ₂ , and the mixing ratio of the spherical toner is 15% or less. Further, the spherical toner has a circle whose diameter is the absolute maximum length of the toner particle. Is Sc and the actual projected area of the toner particles is Sr, the value of Sc / Sr is 1.0 ≦ Sc / Sr ≦ 1.5.
When the electrophotographic toner is formed within the range, it is possible to provide the toner having excellent transfer efficiency and good cleaning property.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an electrophotographic apparatus to which an electrophotographic toner is applied.

[Explanation of symbols]

 1 Photoreceptor 3 Exposure Optical System 5 Developing Roller 6 Toner Supply Roller 10 Toner

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuhiro Tsuru, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Hideki Yasuda, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A toner for electrophotography in which an amorphous toner and a spherical toner are mixed in a toner which makes an electrostatic latent image on a latent electrostatic image bearing member visible by being conveyed by a toner bearing member. 2. A volume average particle diameter D ₁ of the irregular toner, the volume average particle diameter of the spherical toner and D _2, electrons according to claim 1, characterized in that a relationship of D _1> D ₂ Photographic toner. 3. The mixing ratio of spherical toner is 15% by weight.
The toner for electrophotography according to claim 1 or 2, wherein: 4. The spherical toner has a range of 1.0 ≦ Sc / Sr ≦ 1.5, where Sc is the area of a circle whose diameter is the absolute maximum length of toner particles and Sr is the substantial projected area of the toner particles. Claim 1, claim 2, claim 3 characterized in that there is
The described electrophotographic toner.