JPH1010857A - Developing roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing roller with which toners are uniformly supplied without secure adhesion to the roll and adequate image densities and well copied images are obtainable for a long period of time. SOLUTION: This roll is used for one-component negative charge development system in which a semiconductive coating layer 12. formed by using materials for forming the semiconductive coating layer 12 contg. a synthetic resin, conductive material and dielectric powder particles 13 is a surface layer. In such a case, the compounding amt. of the component for forming the dielectric powder particles 13 to the material for forming the semiconductive coating layer 12 is set at 10 to 30vol.%. The dielectric powder particles 13 component particles are intermittently dispersed in The surface direction of the semiconductive coating layer 12. the thickness T of the semiconductive coating layer 12 of the parts not contg. the dielectric powder particles 13 is so set as to satisfy H/2<=T<H with respect to the average particle diameter H of the dielectric powder component and the surface roughness Ra of the semiconductive coating layer 12 is so set as to satisfy 1.5μm<Ra<2.5μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
The present invention relates to a developing roll in a one-component negative charging developing device used for a printer or the like.

[0002]

2. Description of the Related Art Generally, copying by an electrophotographic copying machine is performed as follows. That is, a document image is formed as an electrostatic latent image on a rotating photosensitive drum, a toner image is formed by attaching toner to the image, and copying is performed by transferring the toner image to copy paper. In this case, in order to form an electrostatic latent image on the surface of the photosensitive drum, the surface of the photosensitive drum is charged in advance, and a document image is projected on the charged portion through an optical system and irradiated with light. 2. Description of the Related Art An electrostatic latent image is formed by canceling the charge of a part. As a developing method for developing a latent image on a photosensitive drum to form a visible image, various methods have conventionally been proposed according to the type of developer used. As one example, a one-component developing system using only toner as a developer is known. Further, as such a one-component developing system, a developing system using a one-component magnetic developer and a developing system using a one-component non-magnetic developer are known.

For example, as shown in FIG. 2, in the one-component developing system using the one-component magnetic developer, a cylindrical pipe 9 is provided on a developer carrier and a semiconductive coating layer 10 is formed on an outer peripheral surface thereof. Is used. A magnet roll 2 is provided inside the developing roll 1.

In the one-component developing system using such a developing roll 1, a one-component magnetic developer (toner) 4 contained in a toner box 3 is supplied to the developing roll 1, and a magnet roll 2 is supplied. Is held on the surface of the developing roll 1 by the magnetic force. Next, the one-component magnetic developer 4 whose amount of developer is controlled by a contact blade or a doctor blade 5 which is a developer regulating member is deposited in a thin layer on the surface of the developing roll 1 and a necessary electric charge is obtained. Is to be granted.

On the other hand, a photosensitive drum 6 as an electrostatic latent image holding member is disposed so as to face the developing roll 1 provided at the opening of the toner box 3.
It is rotating in the opposite direction. The photosensitive drum 6 has a photoconductive layer on the electrode, and after uniformly charging the surface thereof, irradiates the original image light to form an electrostatic latent image corresponding to the original image. I can do it.

The thin layer of the one-component magnetic developer 4 formed on the surface of the developing roll 1 is moved to a developing area where the developing roll 1 and the photosensitive drum 6 are opposed by the rotation of the developing roll 1. Is sent. Next, a DC superimposed AC voltage is applied to the developing roll 1 from the high-voltage AC power supply 7 and the DC power supply 8, and an oscillating electric field is generated in a gap between the photosensitive drum 6 and the developing roll 1. The one-component magnetic developer 4 having the above electric charge flies onto the electrostatic latent image on the photosensitive drum 6, thereby performing the development.

As described above, the developing roll 1 used in such a one-component developing system generally has a cylindrical pipe 9 made of aluminum, stainless steel, or the like, and an insulating surface made of phenol resin or the like on the outer peripheral surface. And a semiconductive coating layer 10 having a predetermined thickness formed by coating a semiconductive composition containing a conductive polymer such as conductive carbon in an appropriate amount in a conductive polymer material. Further, the surface of the semiconductive coating layer 10 of the developing roll 1 is used in order to improve the quality of an initial image. It is known that the one-component developing system includes a one-component negative charging developing system and a one-component positive charging developing system.

[0008]

However, in the one-component negatively charged developing system, when the developing roll 1 is used for a long period of time, the deteriorated and pulverized toner 4 and the external additive have extremely high electric charges (charge-up). )
Adhering to the surface of the developing roll 1
There arises a problem that a strong electric adhesive force (mirror image force) is generated on the upper surface. When the above-mentioned mirror image force is generated, the supplied toner 4 stays firmly on the developing roll 1, causing an image defect such as a ghost phenomenon and inhibiting normal charging of the toner 4. Causes a drop in

Since the charge-up phenomenon depends on the charging load characteristic of the surface of the developing roll 1 and the charge elimination characteristic of a small charge, the electric resistance is reduced and the surface roughness is formed by the conductive material at the initial stage of copying. Can be suppressed to some extent by improving the static elimination effect, but when about 3000 copies are made, the initial surface roughness is no longer maintained, and it is difficult to maintain image quality for a long period of time.

Therefore, on the contrary, it is conceivable that the charging property of the surface of the developing roll 1 is suppressed from the beginning so that a good copied image can be obtained after copying 50,000 sheets, assuming long-term use. In this case, however, there is a problem that a sufficient initial concentration (particularly at high temperature and high humidity) cannot be obtained.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a developing roll capable of uniformly supplying toner without firmly adhering thereto and maintaining a good image density for a long period of time. And

[0012]

In order to achieve the above object, a developing roll of the present invention comprises a semiconductive layer formed using a semiconductive coating layer forming material containing the following components (A) to (C). A developing roll for use in a one-component negatively charged developing system in which a conductive coating layer is a surface layer, wherein the blending amount of the component (C) with respect to the material for forming a semiconductive coating layer is set to 10 to 30% by volume. The component (C) particles are intermittently dispersed in the surface direction of the semiconductive coating layer, and the thickness (T) of the semiconductive coating layer in a portion not containing the component (C) particles Satisfies the following inequality (1) with respect to the average particle diameter (H) of the component particles (C), and the surface roughness (Ra) of the semiconductive coating layer satisfies the following inequality (2). The configuration is set. (A) Synthetic resin. (B) a conductive material. (C) negatively charged and having an average particle size of 8 to 15 μm
A dielectric powder particle.

[0013]

## EQU3 ## H / 2 ≦ T <H (1)

[0014]

1.5 μm <Ra <2.5 μm (2)

That is, in order to solve the above-mentioned problems, the present inventors disperse negatively charged dielectric powder particles in a surface layer of a developing roll in a one-component negatively charged developing system to form an electrostatic repulsive force. Has been proposed, and an application has been filed (Japanese Patent Application No. 8-22788, February 8, 1996).
Day). However, further studies have been made to further enhance the effects obtained by the above-described invention and to develop a developing roll capable of stably obtaining the effects over a long period of time. As a result, the addition amount of the dielectric powder particles [component (C)] to be contained in the semiconductive coating layer forming material is set to a specific range, and the thickness of the semiconductive coating layer is reduced to the dielectric powder particles [(C) Component), the surface roughness of the semiconductive coating layer can be adjusted to a specific range, thereby achieving the intended purpose. . In the present invention, “intermittent” means
In the semiconductive coating layer, the dielectric powder particles [(C) component] are not arranged in close contact with each other but in a part where the dielectric powder particles [(C) component] exist and a part where the dielectric powder particles [(C) component] do not exist. Is to coexist.

In the developing roll of the present invention, further improvement of the developing characteristics can be achieved by using silicon resin powder particles as the dielectric powder particles as the component (C).

Further, in the developing roll of the present invention, by using a mixture of polyvinyl butyral and a phenol resin as the synthetic resin as the component (A), the material for forming the semiconductive coating layer of the component (C) particles can be obtained. And the synergistic effects such as the relationship between the average particle diameter of the component (C) particles and the thickness of the semiconductive coating layer, etc., further improving the development characteristics.

[0018]

Next, an embodiment of the present invention will be described.

The developing roll of the present invention is, for example, as shown in FIG.
As shown in (A) and (B), a configuration in which a semiconductive coating layer 12 is laminated on the outer peripheral surface of the cylindrical pipe 9 is adopted.
In the semiconductive coating layer 12, dielectric powder particles 13 are intermittently dispersed in the plane direction.

In the developing roll 11, the cylindrical pipe 9 is formed into a cylindrical shape using a conventionally known metal such as aluminum, nickel, and corrosion-resistant steel (stainless steel) or an alloy thereof. A material whose surface is treated by electrolysis, blasting, sanding or the like so as to have a predetermined roughness is generally used.

The semiconductive coating layer 12 laminated on the outer peripheral surface of the cylindrical pipe 9 comprises a synthetic resin [(A) component], a conductive material [(B) component], and dielectric powder particles 13 [ (C) component].

As the synthetic resin (component (A)) used in the present invention, a mixture of polyvinyl butyral and a phenol resin, an acrylic resin, an epoxy resin, a polyester resin, a polyamide resin and the like are used. Above all, a developing roll using a mixture of polyvinyl butyral and a phenol resin provides a high image density even under a high-temperature and high-humidity environment, and can effectively suppress or prevent a difference in charging characteristics from occurring. The occurrence of the ghost phenomenon can be effectively avoided without any difference in the developing characteristics between the consumed and unconsumed portions.

In the present invention, the mixture of polyvinyl butyral and phenol resin used as a material for forming a semiconductive coating layer includes polyvinyl butyral, which is known as one of vinyl-phenol resin structural adhesives. A mixture of a thermosetting resin and a polyvinyl butyral 1
It is preferable that the phenol resin is set so as to have a ratio of 10 to 200 parts with respect to 00 parts by weight (hereinafter abbreviated as "part"). In addition, as a phenol resin, generally,
A resol type is used.

The mixture of the polyvinyl butyral and the phenol resin can be obtained by gel permeation chromatography (Gel Perm) using polystyrene as a standard sample.
In eation Chromatography (GPC), it is preferable to use those containing 2% by weight or more of those having a molecular weight (in terms of polystyrene) of 1.64 × 10 ⁴ or more. That is, by using such a high-molecular weight material, a higher density image can be realized.

Next, as the conductive material (component (B)) used in the present invention, conventionally known materials are used. For example, in addition to metal powder, C-TiO ₂ , C-ZnO
Conductive compounds such as graphite, carbon black,
Conductive powder and conductive fiber such as carbon fiber;
Further, ZnO, SnO ₂ , TiO ₂ , In ₂ O ₃ , Mo
Metal oxides such as O are also used, and LiI, LiC
1, LiClO ₄ , NaI, NaSCN, KI, AgN
Inorganic ion salts such as O ₃ , and organic ion salts such as lithium stearylsulfonate, sodium octylsulfonate, lithium dodecylbenzenesulfonate, and sodium naphthalenesulfonate are also used. Note that the above "C-"
Means having conductivity.

The dielectric powder particles 13 (component (C)) used in the present invention include, for example, silicon resin powder particles, fluororesin powder particles, and polyacrylonitrile resin powder particles. Above all, the developing roll 11 using the silicon resin powder particles can effectively avoid the occurrence of a ghost phenomenon without forming a developer layer that has stagnated firmly on the developing roll 11, and can maintain high developing characteristics for a long time. Can be secured.

Further, the dielectric powder particles 13 need to have an average particle diameter of 8 to 15 μm. Among them, the average particle diameter is particularly preferably 12 to 15 μm. That is, in the present invention, as described later, the thickness of the semiconductive coating layer 12 is defined by the average particle diameter. Therefore, when the average particle diameter is less than 8 μm, the thickness of the semiconductive coating layer 12 is accordingly reduced. Is too thin to maintain the durability of the semiconductive coating layer 12, and therefore it is impossible to uniformly supply the toner for a long period of time. On the other hand, if the average particle diameter exceeds 15 μm, the dielectric powder particles 13 impair the developing characteristics and cause a decrease in concentration.

In the present invention, a known additive such as a charge controlling agent may be further added to the semiconductive coating layer forming material, if necessary.

The developing roll 11 of the present invention is manufactured, for example, as follows. That is, first, each of the above-mentioned components is dispersed in a predetermined solvent in a mixing ratio shown below to prepare a coating liquid to be a semiconductive coating layer forming material. In addition, the viscosity of this coating liquid is 100 to 200 cp.
s (measuring temperature: 23 ° C.). Particularly preferably, it is 120 to 170 cps. The mixing ratio of the synthetic resin [(A) component], the conductive material [(B) component] and the dielectric powder particles 13 [(C) component] is determined by the volume resistivity of the intended semiconductive coating layer 12. And the surface roughness (Ra) of the semiconductive coating layer 12 is determined appropriately so as to have a specific value. Generally, 100 parts of the synthetic resin [(A) component] [Component (B)] is 10 to 100 parts, and the dielectric powder particles 13
[(C) component] is set at a ratio of 30 to 50 parts. In addition, as a solvent of the coating liquid, methyl ethyl ketone (hereinafter abbreviated as “MEK”), isopropanol,
Methanol, toluene, acetone and the like are used, and these may be used alone or as a mixture of two or more.

Subsequently, a known method is used for coating the cylindrical pipe 9 with the coating liquid. For example, in the dipping method, the semiconductive coating layer 12 can be formed by immersing the cylindrical pipe 9 in the coating liquid, pulling it up, drying it, and then performing a heat treatment (crosslinking). The semiconductive coating layer 12 may be composed of only one layer or a laminated structure of two or more layers. Further, the surface of the semiconductive coating layer 12 is subjected to a polishing treatment, if necessary, so that the surface is roughened.

The thus obtained developing roll 11
Can uniformly supply the toner without firmly adhering it to the semiconductive coating layer 12, and can maintain good image density for a long period of time.

The compounding amount of the dielectric powder particles 13 (component (C)) with respect to the semiconductive coating layer forming material is 1
Must be in the range of 0 to 30% by volume. Among them, the content is particularly preferably 20 to 30% by volume. That is, if the content is less than 10% by volume, the required surface roughness of the semiconductive coating layer 12 cannot be obtained, and a good image density cannot be obtained. This is because the amount of the synthetic resin (component (A)), which is the main component of the forming material, is relatively reduced, and poor charging of the obtained developing roll occurs.

Further, the thickness (T) (see FIG. 1) of the semiconductive coating layer 12 in a portion not containing the dielectric powder particles 13 is as follows:
The following inequality (1) must be satisfied. That is, if the thickness is less than の of the average particle diameter (H) of the dielectric powder particles 13, the dielectric powder particles 13 may fall out of the semiconductive coating layer 12 (missing particles), or the dielectric powder This is because the particles 13 are worn out (contact with the toner) due to contact with the toner, and a problem is caused in the durability of the obtained developing roll, and the thickness is larger than the average particle diameter of the dielectric powder particles 13. In this case, the finely divided toner is charged up by the charge-up phenomenon, so that the semiconductive coating layer 1
This is because the toner adheres firmly to the surface of the developing roller 2 and the supplied toner stays firmly on the developing roll 11 due to the resulting image force. If the thickness (T) of the portion of the semiconductive coating layer 12 that does not include the dielectric powder particles 13 is less than 5 μm, the surface roughness of the semiconductive coating layer 12 must be within the appropriate range. It is not preferable because the thickness is small, and image quality disorders such as uneven density and leakage are likely to occur.

[0034]

## EQU5 ## H / 2 ≦ T <H (1)

The surface roughness (R) of the semiconductive coating layer 12
a) must satisfy the following inequality (2). That is, if the thickness is 1.5 μm or less, the toner conveyance force is weak, and the image density is reduced.
If the amount is more than the above, a sufficient amount of triboelectricity cannot be imparted to the toner, and the image density is reduced. In addition, the said surface roughness (Ra) is a center line average roughness (Ra) in the definition and display of the surface roughness of JIS B0601-1982. The measurement of the surface roughness (Ra) is performed using a stylus electric magnifying surface roughness measuring device (JIS B0).
651-1977).

[0036]

1.5 μm <Ra <2.5 μm (2)

The surface roughness (Ra) is determined by measuring the thickness (T) of the portion of the semiconductive coating layer 12 not including the dielectric powder particles 13.
By adjusting the average particle diameter (H) of the dielectric powder particles 13 and the average particle diameter (H), a value substantially satisfying the above inequality (1) can be obtained. However, finally, the adjustment of the surface roughness can also be performed by a polishing treatment.

Further, it is preferable that the volume resistivity of the semiconductive coating layer 12 of the developing roll 11 is set in a range of 10 ³ to 10 ⁷ Ω · cm. That is, when the volume resistivity of the semiconductive coating layer 12 is less than 10 ³ Ω · cm,
A bias leak may occur between the photosensitive drum and the photosensitive drum, which may cause an image defect. If it exceeds 10 ⁷ Ω · cm, the electric field between the photosensitive drum and the photosensitive drum is weakened, the flying power of the toner is reduced, and the image density is reduced. This is because there is a possibility of becoming.

In the developing roll 11 of the present invention, the semiconductive coating layer 12 is laminated on the outer peripheral surface of the conventionally known cylindrical pipe 9 as described above. A conventionally known layer, for example, an adhesive layer, a conductive resin layer, or the like, may be laminated between the cover layer 12 to form a multilayer structure.

Next, examples will be described together with comparative examples.

[0041]

Examples 1 to 26, Comparative Examples 1 to 50 First, a mixture of polyvinyl butyral and phenol resin as a synthetic resin [the weight mixing ratio of polyvinyl butyral and phenol is 100: 100 and the molecular weight by GPC (in terms of polystyrene) ) Is 1.64 × 10 ⁴ or more 2% by weight
100 parts of carbon black are blended as a conductive material after dissolving or dispersing 100 parts in MEK, and as shown in Tables 1 to 12, dielectric powder particles having different average particle diameters (silicon resin). Powder particles). These were uniformly mixed and dispersed in a ball mill to obtain a coating liquid for forming a semiconductive coating layer adjusted to a viscosity of 150 cps (measuring temperature: 23 ° C.).

Then, diameter: 20 mm, thickness: 0.7 m
m, prepared by immersing it in the above-mentioned various coating solutions, pulling it up and drying,
By performing a heat treatment (crosslinking), a semiconductive coating layer was formed on the outer peripheral surface of the cylindrical body with a film thickness shown in Tables 1 to 12 below. At this time, the volume resistance of the semiconductive coating layer was a value shown in the same table. Thereafter, the surface of the formed semiconductive coating layer was finished by sliding contact with a polishing cloth, a sheet or the like. Thus, a developing roll was obtained.

[0043]

Example 27 In forming a semiconductive coating layer, negatively charged fluororesin powder particles (average particle diameter: 10 μm) were used as dielectric particles, and were mixed in the mixing ratio shown in Table 13.
Other than that was carried out similarly to Example 1, and produced the developing roll.

[0044]

Example 28 In forming the semiconductive coating layer, negatively charged polyacrylonitrile resin powder particles (average particle diameter: 12 μm) were used as the dielectric particles, and were mixed in the mixing ratio shown in Table 13. Other than that was carried out similarly to Example 1, and produced the developing roll.

[0045]

[Comparative Example 51] In forming a semiconductive coating layer, non-negatively charged urethane resin powder particles (average particle diameter: 10 μm) were used as the dielectric particles, and were mixed in the mixing ratio shown in Table 13. Other than that was carried out similarly to Example 1, and produced the developing roll.

[0046]

Comparative Example 52 In forming a semiconductive coating layer, non-negatively charged polyamide resin powder particles (average particle diameter: 12 μm) were used as dielectric particles, and were mixed in the mixing ratio shown in Table 13. Other than that was carried out similarly to Example 1, and produced the developing roll.

Then, the various developing rolls obtained in this manner are respectively used as a one-component magnetic developer (toner).
(A distance between the photosensitive drum and the developing roll was set to 300 μm) as follows.
Image quality evaluation of the surface roughness (Ra) of the developing roll in the initial stage and the image density under high temperature and high humidity, and the surface roughness (Ra) of the developing roll after copying 50,000 sheets (hereinafter abbreviated as "50K print") The image quality was evaluated for image density under low temperature and low humidity, and the results are shown in Tables 1 to 13 below.

The image density was measured in an environment of high temperature and high humidity (28 ° C. × 85% RH) and low temperature and low humidity (10 ° C.
An image was formed in an environment of (× 15% RH), a solid black copy was taken at the maximum density, and the density of the copy was measured with a reflection densitometer manufactured by Macbeth. The larger the measured value, the higher the concentration, indicating 1.4.
A case of 0 or more was regarded as a pass. Then, a pass was evaluated as ○, and a reject was evaluated as ×.

Regarding the surface roughness (Ra), JI
According to SB0601-1982, it measured using the stylus electric expansion type surface roughness measuring device (JISB0651-1976).

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

[0053]

[Table 4]

[0054]

[Table 5]

[0055]

[Table 6]

[0056]

[Table 7]

[0057]

[Table 8]

[0058]

[Table 9]

[0059]

[Table 10]

[0060]

[Table 11]

[0061]

[Table 12]

[0062]

[Table 13]

Further, the results of Tables 1, 2, 4, and 5, 7 to 9, 11 and 12 are summarized in the following manner. That is, the evaluation of the image density under high temperature and high humidity in the initial stage and the evaluation of the image density under low temperature and low humidity at 50K were performed for each of the example products and the comparative example products. Evaluation of)
/ (Evaluation of image density under low temperature and low humidity at 50K). The results are shown in Tables 14 to 17 below.

[0064]

[Table 14]

Table 14 shows that the silicon resin powder particles having an average particle diameter of 8 μm were used as the dielectric powder particles (component (C)), and the semiconductive coating layer forming material of the dielectric powder particles (component (C)) was used. The evaluation when the ratio (volume%) to the whole and the thickness (T) of the semiconductive coating layer in the portion not containing the dielectric powder particles (component (C)) are changed. According to Table 14, when the thickness of the semiconductive coating layer not including the silicon resin powder particles is 8 μm or more, it is impossible to form an appropriate surface roughness (Ra), and the toner is charged by the charge-up phenomenon. Since the toner stays on the developing roll, good image density cannot be obtained. Further, when the total ratio of the silicon resin powder particles is 36% by volume or more, the polyvinyl butyral-phenol resin serving as a base is relatively small, so that charging failure occurs,
Good image density cannot be obtained. Conversely, if the total ratio of the silicon resin powder particles is 22% by volume or less, an appropriate surface roughness (Ra) cannot be obtained, and a good image density cannot be obtained.

[0066]

[Table 15]

Table 15 shows that silicon resin powder particles having an average particle diameter of 12 μm were converted to dielectric powder particles (component (C)).
And summarized in the same manner as in Table 14 above. According to Table 15 above, when the thickness of the semiconductive coating layer not including the silicon resin powder particles is 12 μm or more, it is impossible to form an appropriate surface roughness (Ra), and the toner is charged due to a charge-up phenomenon. Since the toner stays on the developing roll, good image density cannot be obtained. When the thickness is 5 μm, particles are lost or particles are worn out, and the durability of the obtained developing roll cannot be obtained in long-term (50K printing) use. On the other hand, when the total ratio of the silicon resin powder particles is 36% by volume or more, the amount of the polyvinyl butyral-phenol resin serving as a base is relatively small, so that charging failure occurs and a good image density cannot be obtained. Conversely, if the total proportion of the silicon resin powder particles is 15% by volume or less, an appropriate surface roughness (Ra) cannot be obtained, and a good image density cannot be obtained.

[0068]

[Table 16]

Table 16 shows that silicone resin powder particles having an average particle diameter of 15 μm were converted into dielectric powder particles (component (C)).
And summarized in the same manner as in Table 14 above. According to Table 16, when the thickness of the semiconductive coating layer not including the silicon resin powder particles is 16 μm or more, an appropriate surface roughness (Ra) cannot be formed. Since the toner stays on the developing roll, good image density cannot be obtained. When the thickness is 5 μm, particles are lost or particles are worn, and the durability of the obtained developing roll is not obtained in long-term (50K printing) use. Further, when the total ratio of the silicon resin powder particles is 36% by volume or more, the polyvinyl butyral-phenol resin serving as a base is relatively small, so that charging failure occurs,
Good image density cannot be obtained. On the other hand, when the total ratio of the silicon resin powder particles is 8% by volume or less, an appropriate surface roughness (Ra) cannot be obtained, and a good image density cannot be obtained.

[0070]

[Table 17]

Table 17 shows that silicon resin powder particles having an average particle diameter of 20 μm were converted to dielectric powder particles (component (C)).
And summarized in the same manner as in Table 14 above. According to Table 17, when the thickness of the semiconductive coating layer not including the silicon resin powder particles is 21 μm or more, an appropriate surface roughness (Ra) cannot be formed, and further, the toner is not charged due to the charge-up phenomenon. Since the toner stays on the developing roll, good image density cannot be obtained. In any case where silicon resin powder particles having an average particle diameter of 20 μm are used, long-term (50K print)
In use, image defects have been caused by missing and worn particles. On the other hand, when the total proportion of the silicon resin powder particles is 27% by volume or more, the amount of the polyvinyl butyral-phenol resin serving as a base is relatively small, so that charging failure occurs and a good image density cannot be obtained.

As is clear from the results shown in Tables 1 to 17, Examples 1 to 28 were able to obtain good image densities over the initial period and over a long period (50K printing). On the other hand, the comparative examples 1 to 52 had poor initial image densities under high temperature and high humidity, or poor image densities under long-term (50K printing) low temperature and low humidity.

[0073]

As described above, the developing roll of the present invention
The component (C) is used as the semiconductive coating layer forming material, the compounding amount of the component (C) with respect to the semiconductive coating layer forming material is set in a specific range, and the component (C) component particles are used. Is set in a specific range with respect to the average particle diameter (H) of the component (C), so that the surface roughness of the semiconductive coating layer is not included. (Ra) falls within a specific range, and the toner stays firmly on the surface of the developing roll for a long period of time due to a synergistic effect of these and the action of repelling the negatively charged developer and the component (C). Can be prevented from occurring. Therefore, an appropriate image density and a good copied image can be stably obtained over a long period of time.

Further, in the developing roll of the present invention, by using silicon resin powder particles as the dielectric powder particles as the component (C), a more appropriate image density and a good copied image can be stably obtained for a long period of time. Obtainable.

Further, in the developing roll of the present invention, by using a mixture of polyvinyl butyral and a phenol resin as the synthetic resin as the component (A),
Particularly, even in a high-temperature and high-humidity environment, an appropriate image density and a good copied image can be stably obtained over a long period of time.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional view of a developing roll of the present invention, and FIG. 1B is a sectional view taken along line XX.

FIG. 2 is an explanatory diagram illustrating an example of a configuration of a developing device.

[Explanation of symbols]

 Reference Signs List 11 developing roll 12 semiconductive coating layer 13 dielectric powder particles

Claims (3)

[Claims] 1. A one-component negatively charged developing system in which a semiconductive coating layer formed using a semiconductive coating layer forming material containing the following components (A) to (C) becomes a surface layer. A developing roll, wherein the compounding amount of the component (C) with respect to the semiconductive coating layer forming material is set to 10 to 30% by volume, and the (C) is added in a plane direction of the semiconductive coating layer. The component particles are intermittently dispersed, and the thickness (T) of the semiconductive coating layer in the portion not containing the component particles (C) is the following inequality with respect to the average particle diameter (H) of the component particles (C). A developing roll characterized in that (1) is satisfied and the surface roughness (Ra) of the semiconductive coating layer is set so as to satisfy the following inequality (2). (A) Synthetic resin. (B) a conductive material. (C) negatively charged and having an average particle size of 8 to 15 μm
A dielectric powder particle. [Equation 1] H / 2 ≦ T <H (1) [Equation 2] 1.5 μm <Ra <2.5 μm (2) 2. The developing roll according to claim 1, wherein the dielectric powder particles as the component (C) are silicon resin powder particles. 3. The developing roll according to claim 1, wherein the synthetic resin as the component (A) is a mixture of polyvinyl butyral and a phenol resin.