JP2006330216A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which an image is prevented from being missing and scattered and a cleaning blade is prevented from being turned up as well, over a long period of time, even in any operational environment. <P>SOLUTION: The image forming apparatus has a first image carrier 1 and a second image carrier 2 to which a solid lubricant material is applied and transfers a toner image formed on the first image carrier to the second image carrier. In the image forming apparatus, the pure water contact angle θ1 of a first solid lubricant material applied to the first image carrier and the pure water contact angle θ2 of a second solid lubricant material applied to the second image carrier satisfy a relation of θ1>θ2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile using an electrophotographic system.

  Conventionally, from the viewpoint of improving transferability such as preventing line image and character image from being lost, a photoconductor with a high release layer coated on the surface is used, or solid zinc stearate is applied onto the photoconductor with a fur brush. Application has been made to improve the releasability of the surface of the photoreceptor. However, when a high release layer is provided on the surface of the former photoreceptor, for example, a resin layer in which fluorine fine particles are dispersed is coated. However, when the layer is thickened, the fluorine fine particles scatter image exposure, resulting in a result. When the layer is thinned due to image deterioration, the layer is quickly lost due to wear associated with durability, and as a result, there is a problem that a long life cannot be achieved. Therefore, the latter method of applying a solid lubricant to the surface of the photoreceptor with a fur brush is advantageous for achieving both high image quality and long life, and has been widely put into practical use.

  However, in the case of the image forming apparatus in which the solid lubricant is applied to the photosensitive member as described above, the amount of application greatly varies in the surrounding environment. For example, in a low-temperature and low-humidity environment, fur brush hairs become hard, so a larger amount of solid lubricant is scraped off and supplied excessively to the photoreceptor. In the case of an image forming apparatus using an intermediate transfer member, excessive supply to the photosensitive member results in a problem. That is, the lubricant saturated with the photosensitive member goes around from the photosensitive member to the intermediate transfer member, and the surface releasability of the intermediate transfer member is also improved. Secondary transfer onto paper is advantageous for a certain degree of releasability, but if the releasability is improved more than necessary, the releasability between the photoconductor and the intermediate transfer member becomes closer. As a result, there is a problem that the image cannot be transferred by the primary transfer from the photosensitive member to the intermediate transfer member.

  In order to solve the above problem, for example, the amount of application of the photoconductor may be larger than the amount of application of the intermediate transfer member (both zinc stearate) so that the surface tension of the photoconductor ≦ the surface tension of the intermediate transfer member. It has been proposed (Patent Document 1). However, under conditions in which a large amount of solid lubricant is applied to the photoreceptor, wraparound to the intermediate transfer member occurs, and as a result, the relationship between the surface tension of the photoreceptor and the surface tension of the intermediate transfer member cannot be maintained. . That is, the transferability decreased during long-term use, and voids occurred. Further, when the surface tension of the photosensitive member = the surface tension of the intermediate transfer member, sufficient transferability could not be secured from the beginning.

Further, for example, it has been proposed that the friction coefficient of the intermediate transfer member−the friction coefficient of the photosensitive member> −0.1 (Patent Document 2). However, it is known that the transfer performance is dominated by the surface energy (= release property) rather than the friction coefficient, and it is still insufficient for improving the transfer performance.
Japanese Unexamined Patent Publication No. 8-21755 JP 2000-19858 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that prevents an image from being lost for a long period of time under any use environment.

  It is another object of the present invention to provide an image forming apparatus that prevents not only image skipping but also image scattering over a long period of time under any use environment.

  It is another object of the present invention to provide an image forming apparatus that prevents an image from being lost or scattered over a long period of time under any use environment, and prevents a cleaning blade from being turned over.

  The present invention has a first image carrier and a second image carrier to which a solid lubricant is applied, and image formation in which a toner image formed on the first image carrier is transferred to the second image carrier. A pure water contact angle θ1 of the first solid lubricant applied to the first image carrier and a pure water contact angle θ2 of the second solid lubricant applied to the second image carrier. The present invention relates to an image forming apparatus characterized by satisfying a relationship of θ1> θ2.

  The image forming apparatus of the present invention can prevent the image from being lost for a long period of time even if the application amount (supply amount) of the solid lubricant becomes excessive due to a change in use environment or the like. That is, even if the first solid lubricant wraps around the second image carrier, it is possible to prevent the image from being lost for a long time. In addition, scattering of images can be prevented. Furthermore, the cleaning blade can be prevented from turning over.

  One embodiment of the image forming apparatus of the present invention is shown in FIG. The image forming apparatus shown in FIG. 1 has at least a first image carrier (photosensitive member) 1 and a second image carrier (intermediate transfer member) 2, and a toner image formed on the first image carrier 1 It is transferred to the second image carrier 2, and usually further includes a developing unit 3, a photosensitive member cleaning unit 4, a charging charger 5, an exposure means 6, an intermediate transfer member cleaning unit 7, a primary transfer roller 8, and A secondary transfer roller 9 is provided. In FIG. 1, a so-called tandem process is employed as the development process, but the development process is not limited to this. For example, a 4-cycle process may be employed, and a full-color or monochrome process may be employed. In addition, although an intermediate transfer belt having a belt shape is used as the second image carrier 2, other drum-shaped intermediate belts may be used.

  The operation of the image forming apparatus will be described with reference to FIGS. FIG. 2 is an enlarged configuration diagram of the imaging unit unit 20 including the first image carrier 1, the developing unit 3, the photoconductor cleaning unit 4, the charging charger 5, and the exposure unit 6, and FIG. FIG.

  First, in each imaging unit 20 of yellow (Y), magenta (M), cyan (C), and black (Bk), charging, exposure, development, transfer, and cleaning are performed. Specifically, the photosensitive member (first image carrier) 1 uniformly charged by the charging charger 5 is irradiated with writing light (image exposure) modulated based on image data by the exposure means 6. An electrostatic latent image is formed on the photosensitive member 1, and toner is supplied to the photosensitive member on which the electrostatic latent image is formed by the developing unit 3 to form and develop a toner image on the photosensitive member. The formed toner image is electrostatically transferred to the intermediate transfer member (second image carrier) 2 by the voltage applied to the roller by the primary transfer roller unit 8. Since van der Waals force acts between the photoconductor and the toner, toner that cannot be transferred electrostatically, so-called untransferred toner remains on the photoconductor. The transfer residual toner is collected by a method such as scraping by the cleaning blade 10 in the photosensitive member cleaning unit 4. The cleaning unit 4 is provided with a rotatable application brush 11 formed in a roll shape and a solid lubricant (first solid lubricant) 12. The solid lubricant 12 is applied by a pressing spring 13. The application brush 11 is pressed by the brush and is held in contact with the photoreceptor. The application brush 11 is driven to rotate as the photosensitive member rotates, and scrapes off the lubricant from the solid lubricant 12. The scraped lubricant is applied to the surface of the photoconductor and is coated on the surface of the photoconductor so as to be stretched by the cleaning blade 10.

  Next, the toner images on the photosensitive member (first image carrier) 1 formed by the imaging units 20 of the respective colors are sequentially transferred onto the intermediate transfer member (second image carrier) 2 to finally form a full color image. Form. The formed full-color image is transferred onto the recording paper by the secondary transfer roller 9, and then heated and pressurized by a fixing unit (not shown) to fix the toner on the recording paper and discharge it.

  The toner remaining on the surface of the intermediate transfer body 2 is collected by a method such as scraping with a cleaning blade 15 in the intermediate transfer body cleaning unit 7. Similarly to the cleaning unit 4 of the imaging unit 20, the intermediate transfer member cleaning unit 7 is provided with an application brush 16, a solid lubricant (second solid lubricant) 17, and a pressing spring 18. Is coated on the surface of the intermediate transfer member.

In the present invention, the first solid lubricant 12 applied to the photosensitive member (first image carrier) 1 and the second solid lubricant 17 applied to the intermediate transfer member (second image carrier) 2 are pure. Using different water contact angles (pure water contact angles), specifically, the pure water contact angle θ1 of the first solid lubricant and the pure water contact angle θ2 of the second solid lubricant are expressed by the following formula (I):
θ1> θ2 (I)
Preferably the following formula (II):
10 ° ≦ θ1-θ2 ≦ 30 ° (II)
Satisfy the relationship. By using the first and second solid lubricants that satisfy such a relationship, it is possible to prevent image voids over a long period of time. In other words, even if the coating supply amount increases due to fluctuations in the use environment and the first solid lubricant wraps around the second image carrier, the pure water contact angle is relatively small on the second image carrier. Since the second solid lubricant is applied, it is possible to effectively suppress the influence caused by the wraparound of the first solid lubricant. Therefore, it is possible to prevent the image from being lost for a long time. If θ1 is equal to or less than θ2, the hollowing out occurs relatively early.

  The pure water contact angle is a contact angle when a solid lubricant is applied to the surface of the photoreceptor and pure water is dropped on the formed film, and is a characteristic value specific to the substance. A detailed method for measuring the pure water contact angle is shown in FIG. FIG. 4 is a schematic view when a solid lubricant is applied to the surface of a cylindrical photoconductor (surface roughness Ra: about 0.5 μm), and pure water droplets are dropped on the formed film. Basically, it is the same as the measurement on a plane. FIG. 4A is a schematic diagram when the surface energy of the photoconductor is relatively large, and FIG. 4B is a schematic diagram when the surface energy of the photoconductor is relatively small. Θa in FIG. 4A and θb in FIG. 4B correspond to the pure water contact angle. The amount of droplets is suitably 2 to 5 μL, and it is necessary to measure within about 30 seconds after the droplets are formed on the photoreceptor surface. After forming the droplet, it was magnified and observed with a microscope from the side, and the angle (θ / 2) between the line connecting the contact point between the top of the droplet and the side and the ridge line of the photoconductor was measured and doubled. The value is the contact angle θ.

  In the present invention, by using the first solid lubricant and the second solid lubricant satisfying the above formula (II), it is possible to more effectively prevent voids and scatter. When the transferability is extremely improved, the toner easily moves even in a weak electric field, and the toner moves in a space before the contact between the photosensitive member and the intermediate transfer member, and is scattered in a portion other than the required image. In this way, the toner is transferred.

  As the first solid lubricant and the second solid lubricant, among the substances conventionally used as solid lubricants for photoreceptors and intermediate transfer members, the relationship of formula (I), preferably formula (II) is used. Select what you want to use. For example, fatty acids such as stearic acid, oleic acid and palmitic acid, and metal salts thereof can be used. Preferably, the first solid lubricant and the second solid lubricant are selected from fatty acid metal salts, particularly stearic acid metal salts.

Specific examples of the metal stearate include zinc stearate, magnesium stearate, aluminum stearate, barium stearate, lithium stearate, sodium stearate and the like (these pure water contact angles are shown in FIG. 5 described later). reference).
Specific examples of the metal oleate include zinc oleate, magnesium oleate, aluminum oleate, barium oleate, lithium oleate, sodium oleate and the like.
Specific examples of the palmitate metal salt include zinc palmitate, magnesium palmitate, aluminum palmitate, barium palmitate, lithium palmitate, sodium palmitate and the like.

A combination satisfying the formula (I) of the first solid lubricant and the second solid lubricant is exemplified below.
(First solid lubricant, second solid lubricant) =
(1) (zinc stearate, lithium stearate),
(2) (zinc stearate, magnesium stearate),
(3) (zinc stearate, barium stearate),
(4) (zinc stearate, stearic acid),
(5) (zinc stearate, sodium stearate),
(6) (aluminum stearate, magnesium stearate),
(7) (aluminum stearate, barium stearate),
(8) (aluminum stearate, lithium stearate),
(9) (Aluminum stearate, stearic acid)
(10) (aluminum stearate, sodium stearate),
(11) (magnesium stearate, barium stearate),
(12) (magnesium stearate, lithium stearate),
(13) (magnesium stearate, stearic acid),
(14) (magnesium stearate, sodium stearate),
(15) (barium stearate, lithium stearate),
(16) (barium stearate, stearic acid),
(17) (barium stearate, sodium stearate),
(18) (lithium stearate, stearic acid),
(19) (lithium stearate, sodium stearate),
(20) (Stearic acid, sodium stearate)

  Among the above combinations, for example, (1), (4), (8), (9), (12), (13), (15), (16), (18) ), (20) and the like.

  In a more preferred embodiment of the present invention, the first solid lubricant and the second solid lubricant not only satisfy the formula (I), preferably the formula (II) but also have a low frictional force. By using such a solid lubricant in combination, it is possible to prevent the photosensitive member cleaning blade and the intermediate transfer member cleaning blade from turning up, as well as the hollowing out and scattering.

For example, FIG. 5 shows the relationship between the frictional force of the stearic acid metal salt and the pure water contact angle. Various powdered metal stearates were applied to a cloth and sufficiently coated evenly on the photoreceptor. The frictional force is measured using a torque converter (TP-20KCE, manufactured by Kyowa Denki Co., Ltd.) mounted on the shaft of the photosensitive member. The cleaning blade is contacted with a pressure of 20 N / m and the toner is not attached at all. It is calculated from the torque when the body is driven.
It is preferable to use a frictional force of 10 N or less, particularly 8 N or less.

  Among the combinations satisfying the above-described formula (II), preferable examples from the viewpoint of frictional force include combinations such as (1), (12), and (15).

  In FIG. 1, the first solid lubricant and the second solid lubricant are applied via an application brush, but in addition to this, the first solid lubricant and the second solid lubricant may be applied by a foam rubber or solid rubber roller, or the solid lubricant. The material may be applied in direct contact with the photosensitive member or intermediate transfer member.

In the present invention, the coating amounts of the first solid lubricant and the second solid lubricant are such that their films are formed on the surfaces of the first image carrier (photoreceptor) and the second image carrier (intermediate transfer member), respectively. There is no particular limitation. In the present invention, in particular, the application amount of the first solid lubricant may be set large. This is because even if the first solid lubricant wraps around the second image carrier, it is possible to effectively prevent the image from being lost. The amount of the first solid lubricant applied is usually such that it is continuously present on the surface within the range of 0.15 to 0.7 mg / m ² . Moreover, the application amount of the second solid lubricant is usually such that it continuously exists on the surface within the range of 0.05 to 0.3 mg / m ² . The application amount can be controlled by adjusting a pressing spring or the like.

  The first image carrier to which the first solid lubricant is applied is not particularly limited, and usually a pure water contact angle of 70 to 90 ° and a friction coefficient of 0.2 to 0.6 are suitable on the surface before application.

  The second image carrier to which the second solid lubricant is applied is not particularly limited, and usually a pure water contact angle of 70 to 90 ° and a friction coefficient of 0.2 to 0.6 are preferable on the surface before application.

Example 1
In the color MFP (manufactured by Konica Minolta) having the structure shown in FIG. 1, an image forming apparatus using zinc stearate as the first solid lubricant and lithium stearate as the second solid lubricant was used. The application amount of the first solid lubricant was set such that 0.5 mg / m ² of lubricant was present on the surface of the photoreceptor by adjusting a pressing spring or the like. The amount of the first solid lubricant applied is a relatively excessive amount. The application amount of the second solid lubricant was controlled such that 0.2 mg / m ² of lubricant was present on the surface of the intermediate transfer member by adjusting a pressing spring or the like. The printing speed is 31 sheets / min with continuous A4 paper. The toner used was a polymerization toner having a volume average particle diameter of 6.5 μm, and 1000 lines of blue line images (two layers of cyan and magenta) having an adhesion amount of 10 g / m ² were continuously printed.

Each time a predetermined number of prints were completed, the pure water contact angle θ3 on the surface of the photosensitive member and the pure water contact angle θ4 on the surface of the intermediate transfer member were measured, and the image voids and scattering and the blade turn-up were evaluated.
θ3 and θ4 were measured according to the method shown in FIG.

Ranking was given to the evaluation results of the hollows.
5; no hollows were observed even with a loupe (20x magnification);
4; Slight hollows could be observed with a loupe, but they could not be visually observed, and there was no problem in practical use;
3; Slight hollowness was visually observed, but there was no practical problem;
2; The hollows could be visually observed, and there was a problem in practical use;
1; A considerable amount of voids could be observed.

  FIG. 6A shows the relationship between the pure water contact angle θ (θ3 and θ4) and the number of durable sheets, and FIG. 6B shows the relationship between “θ3−θ4” and the number of durable sheets, the evaluation result of the void and the durability. The relationship with the number is shown. No scattering occurred at all until the end of continuous printing. Further, the turning of the cleaning blade for the photosensitive member and the cleaning blade for the intermediate transfer member did not occur at all until the end of continuous printing.

(Comparative Example 1)
Zinc stearate was used as the first solid lubricant, the second solid lubricant was not used, and the application amount of the first solid lubricant was adjusted to 0.5 mg / m on the surface of the photoreceptor by adjusting a pressing spring or the like. Continuous printing and evaluation were performed in the same manner as in Example 1 except that the lubricant of ² was set to be present.

  FIG. 7A shows the relationship between the pure water contact angle θ (θ3 and θ4) and the number of durable sheets, and FIG. 7B shows the relationship between “θ3−θ4” and the number of durable sheets, the evaluation result of the void and the durability. The relationship with the number is shown.

(Example 2)
Aluminum stearate is used as the first solid lubricant, sodium stearate is used as the second solid lubricant, and the coating amounts of the first solid lubricant and the second solid lubricant are 0.5 mg / m ² and 0.2 mg / respectively. Continuous printing and evaluation were performed in the same manner as in Example 1 except that the m ² lubricant was set to be present on the surface.
FIG. 8A shows the relationship between the pure water contact angle θ (θ3 and θ4) and the number of durable sheets, and FIG. 8B shows the relationship between “θ3−θ4” and the number of durable sheets, the evaluation result of the void and the durability. The relationship with the number is shown. The void was ranked 5 with 200 sheets immediately after endurance, and was good with rank 5 thereafter. Scattering was rank 3 at the time of 200 sheets, which was practically no problem, but was ranked 1 at the time of 300 sheets and became NG. Further, when 700 sheets were printed, the photoconductor blade was turned over.

(Comparative Example 2)
First using zinc stearate in the solid lubricant and the both second solid lubricant, the first solid lubricant and the second lubricant application amount of the solid lubricant respectively 0.2 mg / m ² and 0.1 mg / m ² Was continuously printed and evaluated in the same manner as in Example 1 except that the surface was set to exist on the surface.
FIG. 9A shows the relationship between the pure water contact angle θ (θ3 and θ4) and the number of durable sheets, and FIG. 9B shows the relationship between “θ3−θ4” and the number of durable sheets, the evaluation result of the void and the durability. The relationship with the number is shown. Since both the first solid lubricant and the second solid lubricant are coated with zinc stearate and the respective coating amounts are set to normal amounts, the pure water contact angle is higher than that of Example 1 and Comparative Example 1. The number of durable sheets until saturation is increased. Further, since the application amount of the second solid lubricant is set to half of the application amount of the first solid lubricant, the saturated pure water contact angle θ4 is about 6 ° lower than θ3. The difference in pure water contact angle (θ3-θ4) was 11 ° at the maximum, and it became 6 ° at the time of 5000 sheets and was saturated. As a result, the void was the best and was ranked 3, and finally it was ranked 2 and was NG. In addition, there was no occurrence of blade turning through endurance.

(Example 3)
Magnesium stearate is used as the first solid lubricant, lithium stearate is used as the second solid lubricant, and the coating amounts of the first solid lubricant and the second solid lubricant are 0.5 mg / m ² and 0.2 mg / m respectively. Continuous printing and evaluation were performed in the same manner as in Example 1 except that the m ² lubricant was set to be present on the surface.
FIG. 10A shows the relationship between the pure water contact angle θ (θ3 and θ4) and the number of durable sheets, and FIG. 10B shows the relationship between “θ3−θ4” and the number of durable sheets, the evaluation result of the void and the durability. The relationship with the number is shown. Magnesium stearate is inferior to zinc stearate in coating properties, and although the pure water contact angle is slow to saturate, it can generally maintain rank 3 or higher.

Example 4
Barium stearate is used as the first solid lubricant, lithium stearate is used as the second solid lubricant, and the coating amounts of the first solid lubricant and the second solid lubricant are 0.5 mg / m ² and 0.2 mg / m respectively. Continuous printing and evaluation were performed in the same manner as in Example 1 except that the m ² lubricant was set to be present on the surface.
FIG. 11A shows the relationship between the pure water contact angle θ (θ3 and θ4) and the number of durable sheets, and FIG. 11B shows the relationship between “θ3−θ4” and the number of durable sheets, the evaluation result of the void and the durability. The relationship with the number is shown.

The rank of splattering is as follows.
5: No splattering was visually observed;
3: Slight scattering was observed visually, but there was no practical problem;
1: Scattering was visually observable, and there was a problem in practical use.

1 shows a schematic configuration diagram of an embodiment of an image forming apparatus of the present invention. FIG. FIG. 2 is a schematic enlarged view of an imaging unit unit of the image forming apparatus illustrated in FIG. 1. FIG. 2 is a schematic enlarged view of an intermediate transfer member cleaning unit of the image forming apparatus shown in FIG. 1. The schematic diagram for demonstrating the measuring method of a pure water contact angle is shown. The graph showing the relationship between the frictional force of a stearic acid metal salt and a pure water contact angle is shown. Regarding the image forming apparatus of Example 1, (A) is a graph showing the relationship between the pure water contact angle θ (θ3 and θ4) and the durable number, and (B) is the relationship between “θ3-θ4” and the durable number. And the graph showing the relationship between the evaluation result of a hollow and a durable number is shown. Regarding the image forming apparatus of Comparative Example 1, (A) shows a graph showing the relationship between the pure water contact angle θ (θ3 and θ4) and the durable number, and (B) shows the relationship between “θ3-θ4” and the durable number. And the graph showing the relationship between the evaluation result of a hollow and a durable number is shown. Regarding the image forming apparatus of Example 2, (A) is a graph showing the relationship between the pure water contact angle θ (θ3 and θ4) and the durable number, and (B) is the relationship between “θ3-θ4” and the durable number. And the graph showing the relationship between the evaluation result of a hollow and a durable number is shown. Regarding the image forming apparatus of Comparative Example 2, (A) shows a graph showing the relationship between the pure water contact angle θ (θ3 and θ4) and the number of durable sheets, and (B) shows the relationship between “θ3-θ4” and the number of durable sheets. And the graph showing the relationship between the evaluation result of a hollow and a durable number is shown. Regarding the image forming apparatus of Example 3, (A) is a graph showing the relationship between the pure water contact angle θ (θ3 and θ4) and the durable number, and (B) is the relationship between “θ3-θ4” and the durable number. And the graph showing the relationship between the evaluation result of a hollow and a durable number is shown. Regarding the image forming apparatus of Example 4, (A) shows a graph showing the relationship between the pure water contact angle θ (θ3 and θ4) and the durable number, and (B) shows the relationship between “θ3-θ4” and the durable number. And the graph showing the relationship between the evaluation result of a hollow and a durable number is shown.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1; 1st image carrier (photoreceptor), 2; 2nd image carrier (intermediate transfer body), 3; Development part, 4; Cleaning part, 5: Charger, 6: Exposure means, 7: Cleaning part, 8; primary transfer roller, 9; secondary transfer roller, 10; cleaning blade, 11; application brush, 12; first solid lubricant, 13; pressure spring, 15; cleaning blade, 16; application brush, 17; 2 solid lubricant, 18; pressing spring.

Claims (3)

  An image forming apparatus having a first image carrier and a second image carrier to which a solid lubricant is applied, wherein a toner image formed on the first image carrier is transferred to the second image carrier. The pure water contact angle θ1 of the first solid lubricant applied to the first image carrier and the pure water contact angle θ2 of the second solid lubricant applied to the second image carrier satisfy θ1> θ2. An image forming apparatus characterized by satisfying the relationship.   The pure water contact angle θ1 of the first solid lubricant and the pure water contact angle θ2 of the second solid lubricant satisfy a relationship of 10 ° ≦ θ1−θ2 ≦ 30 °. Image forming apparatus. The image forming apparatus according to claim 1, wherein the first solid lubricant and the second solid lubricant are fatty acid metal salts.

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