JP2000298373A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming device which is an image forming device using a transfer means of a contact transfer system, obviates drop-out regardless of the various thicknesses of transfer material and transfer material quality, does not give rise to a transfer blur and variation in image lengths and makes it possible to obtain a good image. SOLUTION: This image forming device has an image carrying member 10 for carrying the toner image and a transfer means 14 for transferring the toner image on the image carrying member 10 to the transfer material 22 by coming into contact with the rear surface of the transfer material 22 and imparting charges thereto. Toners consist of at least a binder resin and charge control agent and contain at least two kinds of fine inorganic powders having different average grain sizes. At least one kind of the fine inorganic powder of these two kinds of the fine inorganic powders is subjected to a surface treatment by a silicone oil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
The present invention relates to an image forming apparatus such as a facsimile.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus, a toner image on a photoreceptor is transferred onto a transfer material, and then the toner image on the transfer material is fixed on the transfer material by heating and pressing with a fixing device. . As a color image forming apparatus for forming a full-color image, while the transfer material is held on a transfer material holder such as a transfer drum, the developed yellow on the latent image carrier,
The magenta, cyan, and black toner images are sequentially superimposed and transferred onto the transfer material, and then the transfer material is peeled from the transfer material carrier, and the toner image on the transfer material is fixed to the transfer material by a fixing device. I have.

On the other hand, a toner image of each color on a latent image carrier is
Instead of transferring to the transfer material on the transfer material holding member, the image is temporarily superimposed and transferred on the intermediate transfer member, and the four-color superimposed toner image is collectively transferred to the transfer material. There is also a color image forming apparatus in which a superposed toner image is fixed on a transfer material by a fixing device. In this color image forming apparatus, there is no need to hold the transfer material on the transfer material holder, and therefore, there is an advantage that the transfer material transportability is high. For this reason, small-sized paper (for example, a government-made postcard) or a manuscript (for example, 200 g /
(cm ² paper), transfer materials such as envelopes and the like. As the intermediate transfer member, an endless belt-shaped intermediate transfer belt is known in addition to the intermediate transfer drum.

In a conventional image forming apparatus, a non-contact type corona charger has been used as a transfer means for transferring a toner image on an image carrier to a transfer material. However, this corona charger has a problem that a high voltage must be applied to generate corona discharge and ozone is generated. For this reason, in recent years, the use of a contact transfer type transfer unit that directly applies a bias voltage to the back surface of a transfer material has been increasing. The contact transfer type transfer means has an advantage that transfer can be performed at a lower voltage than a corona charger and generation of ozone is extremely small. As a transfer unit of the contact transfer system, a transfer roller, a transfer belt, a transfer brush, a transfer blade, and the like are known.

[0005]

In the transfer means of the contact transfer system described above, it is necessary to press the transfer means and the image carrier in pressure with a predetermined pressure from the back side of the transfer material toward the image carrier. At this time, if the pressing force of the transfer unit against the image carrier is low, the contact between the transfer unit and the transfer material becomes partially unstable, causing transfer unevenness and transfer blur due to a decrease in transfer material holding force. . For this reason, the pressing force of the transfer unit against the image carrier is set to a value obtained by adding a margin to the pressure at which the above-described transfer unevenness or transfer blur does not occur, as the lower limit value of the pressing force of the transfer unit against the image carrier. .

However, in recent years, the types of transfer materials have been diversified, and it has become necessary to perform stable transfer from thin to thick transfer materials. Therefore, the set value of the pressing force of the transfer unit to the image carrier needs to be set according to the transfer material having a small thickness. When a toner image is transferred to a material, the pressing force of the transfer means, the transfer material, and the image carrier at the transfer portion increases, causing the toner to aggregate, thereby causing a phenomenon called a so-called hollow character.

In order to cope with such a phenomenon of hollowing out, as a prior art, there is known a method in which the pressing force of the transfer means against the image carrier is reduced to a value which does not cause hollowing out in order to suppress the aggregation of toner. ing. However, reducing the pressing force of the transfer means against the image carrier has made it difficult to achieve both transfer unevenness and transfer blur for the reasons described above. In addition, when a transfer roller is used as a transfer unit, a method of suppressing aggregation of toner by reducing its hardness has been conventionally known, but this does not provide a sufficient effect. Transfer blur due to a reduction in transfer material holding force is caused by the lower hardness of the transfer roller.

As means for solving this problem, Japanese Patent Application Laid-Open No.
No. 18812 has been proposed. This is because the transfer material transport speed at the transfer portion is made 1% or more higher than the speed of the image carrier, so that a shear force is applied to the toner image to peel the toner image from the image carrier and prevent hollowing out. It was done. However, in such a device, the effect cannot be obtained unless the difference between the transfer material conveying speed and the image carrier speed is considerably made. It has been found that a problem of image length variation occurs in that the transport speed varies, so that the image length in the transfer material transport direction varies.

In the device disclosed in Japanese Patent Application Laid-Open No. 10-161434, the pressing force of the transfer roller against the image carrier is controlled by an output image, but the pressing force of the transfer roller against the image carrier is controlled. There are many parts to be added as pressure control means to control by the output image, the device becomes large,
Further, since high precision is required for controlling the pressing force of the transfer roller against the image carrier, it is not practical, for example, the cost of each component is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has no problem in image forming apparatus using a contact transfer type transfer means regardless of the thickness of the transfer material or the material of the transfer material. It is an object of the present invention to provide an image forming apparatus capable of obtaining a good image with no variation in image length.

[0011]

In order to achieve the above object, the present invention is directed to an image bearing member for carrying a toner image obtained by visualizing an electrostatic latent image and a back surface of a transfer material. Transfer means for transferring the toner image on the image carrier to the transfer material by applying a charge to the transfer material, wherein the toner comprises at least a binder resin, a charge control agent, and at least two types of Contains inorganic fine powder of different average particle size,
At least one of the at least two types of inorganic fine powders
The kinds of inorganic fine powders have been subjected to surface treatment with silicone oil.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the inorganic fine powder is silica having two types of different average particle diameters.
Silica not subjected to surface treatment with silicone oil is treated with silane coupling.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, among the two types of inorganic fine powders comprising silica, silica fine particles having a small particle diameter and silica particles having a large particle diameter are used. Is silica B, the average particle diameter Dt of the toner is
The average particle diameter Sa of the silica A and the average particle diameter Db of the silica B satisfy the relationship of Da ≦ Dt / 1000 Dt / 100 ≦ Db ≦ Dt / 10, respectively.

According to a fourth aspect of the present invention, in the image forming apparatus of the first, second or third aspect, the amount of the silica A having a small particle diameter in the inorganic fine powder comprising the two types of silica is less than the toner particles. And the addition amount of the silica B having a small particle diameter in the inorganic fine powder composed of the two types of silica is 0.5 to 3% by weight relative to the toner particles. 0.0% by weight.

The invention according to claim 5 is the invention according to claims 1, 2, and 3
Alternatively, in the image forming apparatus described in Item 4, the average particle diameter Dt of the toner is in a range of 5 ≦ Dt ≦ 10 μm.

The invention according to claim 6 is the invention according to claims 2, 3, and 4.
In the image forming apparatus described in Item 5, the silica B having a small particle diameter in the inorganic fine powder composed of the two types of silica is silica that has been surface-treated with silicone oil.

[0017] The invention according to claim 7 is the invention according to claims 1, 2,
7. The image forming apparatus according to 3, 4, 5 or 6, wherein the transfer unit is a transfer roller having a roller hardness of 70 degrees or less,
The contact pressure of the transfer roller against the image carrier is 500
It is in the range of 0 Pa or more and 25000 Pa or less.

The invention according to claim 8 is the invention according to claims 1, 2,
8. The image forming apparatus according to 3, 4, 5, 6, or 7, wherein a peripheral speed Vt of a transfer roller as the transfer unit is -0.5% ≦ Vt ≦ + 0.5% with respect to a peripheral speed of the image carrier. Is in the range.

The ninth aspect of the present invention is the first aspect of the present invention.
9. The image forming apparatus according to 3, 4, 5, 6, 7, or 8, wherein the image carrier is an intermediate transfer body that carries a plurality of color toners.

[0020]

FIG. 1 shows an embodiment of the present invention (hereinafter referred to as Embodiment 1). Embodiment 1 is an embodiment of a color image forming apparatus. In FIG. 1, reference numeral 1 denotes a photosensitive member as an image carrier which is rotated by a driving unit (not shown) and rotates in the direction of the arrow. Around the photoreceptor 1, a photoreceptor cleaning unit 2 for cleaning the photoreceptor 1, a charger 4 for uniformly charging the photoreceptor 1, and exposing the photoreceptor 1 to form an electrostatic latent image. Exposure means 5 for writing an image by means of yellow developing device 6, magenta developing device 7, cyan developing device 8, black developing device 9 as a plurality of developing means for developing an electrostatic latent image on photoreceptor 1, intermediate transfer Endless Intermediate Transfer Belt 10 as Body (Image Carrier)
And so on.

The photoconductor cleaning unit 2 has a blade 3. The intermediate transfer belt 10 includes a driving roller 13,
It is stretched around a belt transfer bias roller 11, a driven roller 12a, 12b, and a belt cleaning device facing roller 12c as a transfer unit, and is driven by a drive motor (not shown). Intermediate transfer belt 1
0 is to disperse a conductive material such as carbon black in PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), etc. 10 ⁸ ~
The structure is adjusted to a range of 10 ¹³ Ωcm.

A belt cleaning unit 19, which is a cleaning means capable of contacting and separating the intermediate transfer belt 10 and cleaning the intermediate transfer belt 10, includes a cleaning blade 18, and a contact unit for bringing the cleaning blade 18 into and away from the intermediate transfer belt 10. The second and third and fourth color images are transferred from the photoconductor 1 to the intermediate transfer belt 10 after the first yellow image is transferred from the photoconductor 1 to the intermediate transfer belt 10. During this time, the cleaning blade 18 is separated from the intermediate transfer belt 10 by the contact / separation mechanism 26. Intermediate transfer belt 1
A belt position detection mark 23 is provided at an end of the intermediate transfer belt 10, and by starting the image forming process of each color at the timing when the belt position detection mark 23 on the intermediate transfer belt 10 is detected by the mark sensor 24, Accurate color superposition of each color image becomes possible.

A secondary transfer unit 15 serving as a transfer unit for transferring an image from the intermediate transfer belt 10 to a transfer material includes a secondary transfer bias roller 14, which contacts and separates the secondary transfer bias roller 14 with respect to the intermediate transfer belt 10. It is constituted by a contact / separation mechanism 16 for making the contact. Secondary transfer bias roller 1
4 is a metal core made of SUS or the like, and 1 is made of a conductive material.
Is constructed by coating a 0 ⁶ 10 ¹⁰ elastic urethane rubber or the like which is adjusted to a resistance value of approximately [Omega] cm. A driving force is applied to the secondary transfer bias roller 14 by a driving gear, and its peripheral speed is adjusted to be substantially the same as the peripheral speed of the intermediate transfer belt 10.

Although the secondary transfer bias roller 14 is normally separated from the surface of the intermediate transfer belt 10, the four-color superposed image formed on the surface of the intermediate transfer belt 10 is transferred to the transfer material 2.
The transfer of the image from the intermediate transfer belt 10 to the transfer material 22 is performed by applying a predetermined transfer bias voltage by the high-voltage power supply 100 by being pressed by the contact / separation mechanism 16 at a time when the transfer is performed collectively to the transfer belt 2. Do.

The transfer material 22 is subjected to secondary transfer between the intermediate transfer belt 10 and the secondary transfer bias roller 14 at the leading end of the four-color superimposed image on the intermediate transfer belt 10 by the feed roller 25 and the registration roller 21. The sheet is fed from the sheet feeding device at the timing of reaching the position, and the secondary transfer bias roller 14 contacts the back surface of the transfer material 22 to apply a charge, thereby transferring the four-color superimposed image on the intermediate transfer belt 10. Lumber 2
Transferred to 2. The transfer material 22 is discharged after the image transferred from the intermediate transfer belt 10 is fixed by the fixing unit 17.

At the time of forming a full-color image, first, the photosensitive member 1 is uniformly charged by the charger 4 and then exposed by the exposure means 5 to form an electrostatic latent image, thereby writing an image. The electrostatic latent image on the photoreceptor 1 is visualized by a yellow developing device 6 with a one-component developer composed of a yellow toner, and becomes a yellow image (yellow toner image).
The belt transfer bias roller 11 transfers a yellow image on the photoreceptor 1 to the intermediate transfer belt 10 by applying a transfer bias from a high-voltage power supply (not shown) to contact the back surface of the intermediate transfer belt 10 and apply a charge. The photoconductor 1 is cleaned by the photoconductor cleaning unit 2 after the transfer of the yellow image.

Next, the photosensitive member 1 is uniformly charged by the charger 4 and then exposed by the exposure means 5 to form an electrostatic latent image, thereby writing an image.
The upper electrostatic latent image is visualized by a magenta developing device 7 with a one-component developer composed of magenta toner to form a magenta image (magenta toner image). The magenta image on the photoconductor 1 is transferred onto the intermediate transfer belt 10 by the belt transfer bias roller 11 so as to overlap the yellow image, and the photoconductor 1 is cleaned by the photoconductor cleaning unit 2 after the transfer of the magenta image.

Next, the photosensitive member 1 is uniformly charged by the charger 4 and then exposed by the exposure means 5 to form an electrostatic latent image, thereby writing an image.
The upper electrostatic latent image is visualized by a one-component developer made of cyan toner by a cyan developing device 8 to become a cyan image (cyan toner image). The cyan image on the photoconductor 1 is transferred onto the intermediate transfer belt 10 by the belt transfer bias roller 11 so as to be superimposed on the yellow image and the magenta image, and the photoconductor 1 is cleaned by the photoconductor cleaning unit 2 after the transfer of the cyan image. .

Further, the photosensitive member 1 is uniformly charged by the charger 4 and then exposed by the exposure means 5 to form an electrostatic latent image, thereby writing an image. The electrostatic latent image is visualized by a black developing device 9 with a one-component developer composed of black toner to become a black image (black toner image). The black image on the photoconductor 1 is transferred onto the intermediate transfer belt 10 by the belt transfer bias roller 11 so as to be superimposed on a yellow image, a magenta image, and a cyan image, thereby forming a full-color image. After the transfer, the photoconductor is cleaned by the photoconductor cleaning unit 2.

The full-color image (four-color superimposed image) on the intermediate transfer belt 10 is transferred by a secondary transfer bias roller 14 to a transfer material 22 fed by a feed roller 25 and a registration roller 21 from a feeder. Transfer material 22
The image transferred from the intermediate transfer belt 10 is the fixing means 1
The sheet is discharged after fixing at step S7.

In the first embodiment, a single-color mode for forming an image of any one of yellow, magenta, cyan, and black, and a two-color image for forming an image of any two colors of yellow, magenta, cyan, and black are superposed. There are a color mode, a three-color mode for forming an image of any one of three colors of yellow, magenta, cyan, and black, and a full-color mode for forming a four-color superimposed image as described above. It is specified.

When one of the single-color mode, the two-color mode, and the three-color mode is designated, images of each color of yellow, magenta, cyan, and black are formed on the photosensitive member 1 in the above-described full-color mode. Intermediate transfer belt 1
0, an operation of forming a single-color image corresponding to the single-color mode on the photoconductor 1 and transferring the same to the intermediate transfer belt 10 or a two-color image corresponding to the two-color mode to the photoconductor 1 An operation of sequentially forming the three images on the intermediate transfer belt 10 and transferring the images over the intermediate transfer belt 10, or an operation of sequentially forming three-color images corresponding to the three-color mode on the photoconductor 1 and transferring the images over the intermediate transfer belt 10. After the single-color image, the two-color superimposed image, or the three-color superimposed image on the intermediate transfer belt 10 is transferred to the transfer material 22 by the secondary transfer bias roller 14 and fixed by the fixing unit 17, the transfer material 22 is discharged. Paper.

Here, when the image forming operation for forming the superimposed images of a plurality of colors on the transfer material 22 is continuously performed by the number of sheets set by the operation unit, the rear end of the transfer material 22 is driven by the secondary transfer bias roller 14. The transfer bias voltage from the high-voltage power supply 100 to the secondary transfer bias roller 14 is turned off at the timing of sufficient passage, so that the toner image of the next page on the intermediate transfer belt 10 is not adhered to the secondary transfer bias roller 14 after that. The secondary transfer bias roller 14 is separated from the intermediate transfer belt 10 by the contact / separation mechanism 16.

At the time of an image forming operation for forming an image on only one transfer material or at the end of the image forming operation of the last page in a continuous image forming operation for continuously forming an image on a plurality of transfer materials, The secondary transfer bias roller 14 is not separated from the intermediate transfer belt 10, and the cleaning bias having the opposite polarity to the transfer bias voltage (−1 k in the first embodiment) is applied from the high voltage power supply 100 to the secondary transfer bias roller 14.
V) is applied for a fixed time (a time corresponding to four rotations of the secondary transfer bias roller 14 in the first embodiment), and then the high voltage power supply 100 applies the secondary transfer bias roller 14 with the same polarity as the transfer bias voltage. By applying a bias (1 kV in this embodiment 1) for a certain period of time (a time corresponding to two rotations of the secondary transfer bias roller 14 in this embodiment 1), the toner adhering to the surface of the secondary transfer bias roller 14 is applied. Is transferred to the intermediate transfer belt 10 to clean the secondary transfer bias roller 14, and then the contact / separation mechanism 1
6, the secondary transfer bias roller 14 is separated from the intermediate transfer belt 10.

The reason for applying a bias having the same polarity as the transfer bias voltage to the secondary transfer bias roller 14 is as follows.
This is to remove the toner having a small charge amount or the toner charged to the opposite polarity from the secondary transfer bias roller 14. The toner transferred from the secondary transfer bias roller 14 to the intermediate transfer belt 10 is collected from the surface of the intermediate transfer belt 10 by the belt cleaning unit 19.

After the above-described series of image forming operations is completed, the motor stops and the apparatus enters the image forming standby state.
The developer used in the developing units 6 to 9 is a non-magnetic one-component toner. In each of the developing devices 6 to 9, the toner is pressed against the surface of the developing roller 30 by the blade 33 as shown in FIG. 2 to form a thin toner layer on the surface of the developing roller 30. Gives a charge. The electrostatic latent image on the photoreceptor 1 is visualized when toner on the developing roller 30 adheres.

The toner supply sponge roller 31 scrapes off the residual toner on the developing roller 30 and supplies the toner to the surface of the developing roller 30 after the toner is scraped off. The toner supply member 32 is a toner supply sponge roller 3.
1 is supplied to the developing roller 30 and the pressing member 34 is
Is pressed against the blade 33. This pressing member 34 is
In Example 1, a SUS plate having a thickness of 0.8 mm was used.

In the first embodiment, the secondary transfer bias roller 14 is made of urethane foam, and has a hardness of ASK.
The ER-C hardness was adjusted to 60 °. The reason for setting the hardness of the secondary transfer bias roller 14 in this way is that bubbles on the surface of the secondary transfer bias roller 14 can be made small and high in density, and the contact area with the transfer material is increased. This is because it is possible to sufficiently increase the height. The hardness of the secondary transfer bias roller 14 is 7
If the angle exceeds 0 °, the transfer nip cannot be secured, and transfer failure occurs due to poor contact of the secondary transfer bias roller 14 with the transfer material. Therefore, the hardness of the secondary transfer bias roller 14 is preferably set to 70 ° or less.

The contact pressure of the secondary transfer bias roller 14 with respect to the intermediate transfer belt 10 is preferably 2000 Pa or more, more preferably 35,000 Pa or less, and still more preferably 5,000 Pa or more and 25,000 Pa.
It is to be set in the following range. This is because if the contact pressure of the secondary transfer bias roller 14 with respect to the intermediate transfer belt 10 is lower than 2000 Pa, the contact pressure of the secondary transfer bias roller 14 with respect to the intermediate transfer belt 10 becomes insufficient and transfer failure occurs. Because you do.

When the contact pressure of the secondary transfer bias roller 14 with respect to the intermediate transfer belt 10 is higher than 35000 Pa, the secondary transfer bias roller 14 In addition, the torque required for driving the intermediate transfer belt 10 increases, and the bearings of the rotating shafts used for driving the secondary transfer bias roller 14 and the intermediate transfer belt 10 are worn.

Hereinafter, the toner and the like used in the present invention will be described in detail, but the present invention is not limited thereto. All parts described below are based on weight. The toner used in Example 1 is composed of at least a binder resin and a charge control agent, and has two types of silica having different average particle sizes,
Of these two types of silica, silica having a large average particle size and surface-treated with silicone oil is used.

The volume average particle diameter of the toner is 5-1.
It is desirable to be in the range of 0 μm. In the case of a toner having a particle diameter smaller than this range, the toner may cause background contamination during development, the fluidity of the toner may be deteriorated, and the toner may be easily aggregated. Conversely, in the case of a toner having a particle diameter larger than the above range, a high-precision image cannot be obtained due to toner scattering or deterioration in resolution. As the binder resin used in the present invention, various materials selected from fixing properties, charging properties, and the like can be used. However, the binder resin used for the color toner as in the first embodiment is required for the color toner. Polyester resins and polyol resins are particularly preferred from the viewpoints of transparency, gloss, fixability, chargeability and the like.

It is preferable that the toner uses a charge control agent for the purpose of imparting charge and obtains a stable charge amount. In this case, as the charge control agent, it is preferable to add a transparent or white substance that does not impair the color tone of the color toner, and to stabilize the toner to a negative polarity or a positive polarity. Specifically, the charge control agent, as a positive polarity,
A quaternary ammonium salt, an imidazole metal complex, a salt, or the like is used. As a negative electrode, a salicylic acid metal complex, a salt, an organic boron, a calixarene-based compound, or the like is used.

Next, as a colorant for the toner used in the present invention, a dye or pigment capable of obtaining a toner of each color of yellow, magenta, cyan and black can be used. For example, the colorant may be carbon black, lamp black, ultramarine, aniline blue, phthalocyanine blue, phthalocyanine green, hansa yellow G, tardamine 6G, lake, calco oil blue, chrome yellow, quinacridone, benzidine yellow, rose bengal, triallyl. Any conventionally known dyes and pigments such as methane dyes and the like can be used alone or in combination. The amount of these colorants to be used is usually 1 to 30% by weight, preferably 1.5 to 20% by weight, based on the binder resin.

Further, the toner used in the present invention may contain titanium oxide and further alumina for the purpose of improving the fluidity of the toner in combination with the silica used in the present invention as an external additive. In the toner used in the present invention, a fatty acid metal salt (zinc stearate,
(E.g., aluminum stearate) and polyvinylidene fluoride.

Regarding the particle size of each silica, when the small particle size is silica A and the large particle size is silica B, the average particle size Da of silica A and the average particle size Da of silica B with respect to the average particle size Dt of the toner. It is preferable that the average particle diameter Db has a relationship of Da ≦ Dt ≦ / 1000 Dt / 100 ≦ Db ≦ Dt / 10.

In Example 1, the average particle diameter Dt of the toner was 8 μm. Therefore, the average particle diameters Da and Db of silica A and silica B were respectively Da ≦ 0.008 μm 0.08 μm ≦ Db ≦ 0. Preferably, the relationship is 8 μm.

If the particle diameter Da of the silica A is smaller than the value of this relationship, the toner deteriorates in fluidity and, at the same time, silica is easily buried in the surface of the base toner.
The fluidity is further deteriorated by running. When the particle size Db of the silica B is smaller than the above-mentioned relationship, the fluidity of the toner is deteriorated. When the particle size Db of the silica B is larger than the above-mentioned relationship, the silica B becomes difficult to adhere to the toner. Effect is not sufficient.

In Example 1, silica B was used after surface treatment with silicone oil. Further, the silicone oil treatment amount of silica B is suitably 0.5 to 90 parts by weight based on 100 parts by weight of the silica B fine powder. If the silicone oil treatment amount of silica B is less than this range,
The effect of the present invention is not sufficient, and hollowing occurs. Also,
Since the coating on the surface of the silica B is too small, the hydrophobicity of the silica B does not increase. In a high-humidity environment, the insufficient amount of toner charge occurs due to the moisture absorption of the silica B, thereby causing background contamination and the like.
Conversely, if the amount of the silica B treated with the silicone oil is larger than the above range, the flowability of the toner may be deteriorated.

Here, the silica surface-treated with silicone oil refers to the following. First, the silica used in the present invention is generally produced by a wet method or a dry method, and is particularly called a fumed silica produced by a dry method (vapor phase oxidation of a silicon halide compound). Are preferred from the viewpoint of toner fluidity. This is manufactured by a conventionally known technique. For example, it utilizes a thermal decomposition oxidation reaction of silicon tetrachloride gas in an oxyhydrogen flame, and a standard reaction formula is as follows.

SiCl ₄ + 2H ₂ + O ₂ → SiO ○ + 4H
Cl Also, in this production step, it is possible to obtain a composite fine powder of silica and another metal oxide by using a metal halide compound such as aluminum chloride or titanium chloride together with a silicon halide compound, and is used in the present invention. Silica includes them.

Commercially available silica fine powder produced by vapor phase oxidation of a silicon halide compound preferably used in the present invention includes, for example, those commercially available under the following trade names. AEROSIL (Nippon Aerosil) 130 AEROSIL (Nippon Aerosil) 200 AEROSIL (Nippon Aerosil) 300 AEROSIL (Nippon Aerosil) 380 AEROSIL (Nippon Aerosil) TT 600 AEROSIL (Nippon Aerosil) MOX 80 AEROSIL (Japan) MOX170 AEROSIL (Nippon Aerosil Co., Ltd.) COK 84 Ca-O-SiL (CABOT Co.) M-5 Ca-O-SiL (CABOT Co.) MS-7 Ca-O-SiL (CABOT Co.) MS-75 Ca- O-SiL (CABOT Co.) HS-5 Ca-O-SiL (CABOT Co.) EH-5 Wacker HDK N20 (WACKER-CHFMIEGMBH) V1S Wacker HDK N20 (WACKER-CHFMIEGMBH) N20E Wacker HDK N20 (WACKER-CHFMIEGMBH) T30 Wacker HDK N20 (WACKER-CHFMIEGMBH) T40 The silicone oil used in the present invention is not particularly limited, and the silicone oil used in the present invention is not particularly limited. A dimethylpolysiloxane type represented by (1), a methylhydrogenpolysiloxane type represented by the following general formula (2), a methylphenylpolysiloxane type represented by the following general formula (3), and the like can be used. .

[0053]

Embedded image

The silicone oil used in the present invention may be subjected to alkyl modification, amino modification, epoxy modification, epoxy / polyether modification, carboxyl modification, mercapto modification, alcohol modification, fluorine modification, etc., if necessary. . Further, as a method of hydrophobizing silica fine powder with silicone oil, a method of dissolving silicone oil in a solvent, dispersing the silica fine powder in the solvent, and then air-drying or filtering and drying the silica fine powder, silicone oil is used. A method of bringing silicone oil vapor into contact with the vapor and adsorbing the silicone oil vapor to the fine silica powder, a method of directly mixing the fine silica powder and silicone oil, and the like can be used.

Further, in the first embodiment, it is preferable that silica A is subjected to a surface treatment with a silane coupling agent. Examples of the silane coupling agent include a compound represented by the general formula RmSiYn wherein R represents an alkoxy group or a chlorine atom, and m represents 1
Y represents an alkyl group, a vinyl group, a glycidoxy group or a hydrocarbon containing a methacryl group, and n represents an integer of 3-1. ].

For example, typical silane coupling agents include dimethyldichlorosilane, trimethylchlorosilane, allyldimethylchlorosilane, hexamethyldisilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, vinyltriethoxysilane, Examples thereof include γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, divinylchlorosilane, and dimethylvinylchlorosilane.

The surface treatment of the silica A with the silane coupling agent may be performed by a dry treatment in which the vaporized silane coupling agent is reacted with a cloud of silica fine powder by stirring or the like, or by dispersing the silica fine powder in a solvent. The reaction can be performed by a generally known method such as a wet method of reacting a silane coupling agent.

The amount of silica A and silica B subjected to the surface treatment described above is 0.2 to 1.5% by weight based on the weight of the toner particles.
Is 0.5 to 3.0 in weight ratio to the toner particles.
It is preferred to be in the range of weight%. If the amount of silica A is less than the above range, the fluidity of the toner is deteriorated. If the amount of silica A is more than the above range, the effect of the present invention is not sufficient. When the amount of silica B is less than the above range, the effect of the present invention is not sufficient, and when the amount of silica B is more than the above range, the fluidity of the toner is deteriorated.

The toner used in the first embodiment is prepared as follows based on the above conditions.・ Binder resin Polyester resin (softening point 92 ° C) 75 parts Polyester resin (softening point 70 ° C) 25 parts ・ Charge control agent salicylic acid derivative metal salt 4 parts ・ Colorant yellow toner pigment 5 parts (Disazo yellow pigment: C Pigment Yellow 17) Pigment for magenta toner 5 parts (diquinacridone magenta pigment: CI Pigment Red 122) Pigment for cyan toner 2.5 parts (copper phthalocyanine cyan pigment: CI Pigment Red 15) Black toner Pigment for 7 parts (carbon black) The above materials were mixed for each color with a Henschel mixer, and were melt-kneaded with two rolls heated to 100 to 110 ° C. After allowing this kneaded material to cool naturally, coarsely pulverized with a cutter mill, pulverized with a fine pulverizer using a jet stream,
Base colored particles of each color were obtained using an air classifier. In addition, the volume average particle diameter of the base colored particles of each color was as follows. (The volume average particle size was measured using a Coal Counter Model TA-11 manufactured by Coulter Electronics Co., Ltd.) Yellow toner: 8.0 μm Magenta toner: 8.2 μm Cyan toner: 7.9 μm Black toner: 8.3 μm The following external additives were added to 100 parts by weight of each of the base colored particles of each color with a Henschel mixer to obtain Toner 1. Silica A-1 (100 parts of fine silica powder synthesized by a dry method treated with hexamethyldisilazane) Silica B-1 (100 parts of fine silica powder synthesized by a dry method is treated with dimethyl silicone oil (KF-96) , 100 cs (manufactured by Shin-Etsu Chemical Co., Ltd.) and 25 parts thereof diluted with a solvent, treated with hexamethyldisilazane, dried, and then heat-treated at 26 ° C.) The average particle size of silica A-1 Was 0.005 μm, and the average particle size of silica B-1 was 0.2 μm. An image was formed using the toner 1 in the color image forming apparatus of Example 1, and the evaluation was performed. The intermediate transfer belt 10
Is ETFE (ethylene-tetrafluoroethylene copolymer)
The conductive material was prepared by dispersing carbon black as a conductive material and adjusting its volume resistivity to a range of 10 ¹¹ Ωcm. Here, the measurement of volume low efficiency is performed by contacting an HRS probe (inner electrode diameter: 5.9 mm, ring electrode inner diameter: 11 mm) with a high resistivity meter (manufactured by Mitsubishi Chemical Corporation: Hiresta IP). The value was shown after 10 seconds from the application of a voltage of 100 V.

Further, the secondary transfer bias roller 14 is an SU
Approximately 10 ^{8 is} added to the metal core of S301 by a conductive material.
One coated with urethane foam adjusted to a resistance value of Ω was used. The hardness of the secondary transfer bias roller 14 was adjusted to about 60 ° (ASKER-C). Here, the resistance value of the secondary transfer bias roller 14 is 4.9 N on one side (a total of 9.8 N on both sides) at both ends of the core metal when the secondary transfer bias roller 14 is installed on a conductive metal plate. It was calculated from the value of the current flowing when a voltage of 100 V was applied between the metal core and the metal plate under a load.

Further, the secondary transfer bias roller 14 adjusts the contact pressure against the intermediate transfer belt 10 to be 18000 PA, and the peripheral speed of the secondary transfer bias roller 14 is higher than the peripheral speed of the intermediate transfer belt 10. It was adjusted to be + 0.05%. Embodiment 1 and another embodiment 2 of the present invention described later.
7 and Comparative Examples 1 to 5 were evaluated as follows, and FIG. 3 shows the evaluation results. (1) Omission During Transfer The Omission at the transfer was evaluated based on the image formation results of characters and vertical and horizontal lines (both single color, two-color overlapping, and three-color overlapping patterns) using an OHP sheet and cardboard. In this case, the worst value of the transfer omission was evaluated based on the following criteria. Double circle: No omission occurs during transfer. ：: Omission during transfer slightly occurs, but cannot be discerned by the naked eye. Δ: Omission during transfer occurs, but no problem. C: Missing during transfer is severely generated. (2) Transfer Blur Using a thick paper as the transfer material, the transfer blur was evaluated from the image formation results for the entire halftone image and the entire solid image. In this case, the worst value of the transfer blur was evaluated based on the following criteria. Double circle: no transfer blur occurs. ：: Transfer blurring slightly occurred, but hardly noticed. Δ: Transfer blur occurs, but practical. X: Transfer blur is severely generated and is not practical. (3) Image length variation in the feed direction Image length in the feed direction from a pattern in which a thin image or a thick paper is used as a transfer material and a line image is drawn at a position 5 mm inward from each side, and an image formation result for the entire solid image The variation was evaluated. In this case, the image length variation in the feed direction was evaluated by comparing the image lengths of the respective paper types and evaluating the worst value based on the following criteria. Double circle: Difference in image length is less than 0.5 mm. ：: Difference in image length is less than 1 mm. C: Difference in image length is less than 2 mm. X: The difference in image length is 2 mm or more. (4) Defective thin layer on the developing roller (white streak) The thin layer formed on the developing roller was visually observed, and the evaluation was performed based on the following criteria. Double circle: no white stripes. ：: White streaks are slightly generated, but have nothing to do with the image. Δ: White streaks are generated, but practical. ×: Not practical.

Next, other Examples 2 to 7 and Comparative Examples 1 to 5 of the present invention will be described. The second embodiment is different from the first embodiment in that the intermediate transfer belt 1 of the secondary transfer bias roller 14 is used.
The contact pressure to 0 was changed to 5000 Pa, and the rest was the same as the first embodiment. Example 3 corresponds to Example 1
In this embodiment, the contact pressure of the secondary transfer bias roller 14 against the intermediate transfer belt 10 is changed to 23000 Pa, and the rest is the same as the first embodiment.

Example 4 differs from Example 1 in that silica A
0.3 parts by weight of silica A-2, 2.8 parts by weight of silica B-2 as silica B, and the hardness of the secondary transfer bias roller 14 was set to 45 °. Increase the peripheral speed ratio to the intermediate transfer belt 10 by +
The difference was changed to 0.5%, and the rest was the same as in Example 1.

Example 5 differs from Example 1 in that silica A
1.3 parts by weight of silica A-1 and 0.7 parts by weight of silica B-1 as silica B, and the hardness of the secondary transfer bias roller 14 was changed to 70 °.
Other than that is the same as the first embodiment. In Example 6, 2.8 parts by weight of silica B-
2, the contact pressure of the secondary transfer bias roller 14 with respect to the intermediate transfer belt 10 was changed to 5000 Pa, and the rest was the same as the first embodiment.

The seventh embodiment is different from the first embodiment in that the silica A
1.3 parts by weight of silica A-2, 0.7 parts by weight of silica B-1 as silica B, and a contact pressure of the secondary transfer bias roller 14 against the intermediate transfer belt 10 of 25.
000 Pa, and the others were the same as in Example 1.
Is the same as Comparative Example 1 is the same as Example 1 except that silica B-1 was changed to 0.2 parts by weight in Example 1.

Comparative Example 2 differs from Example 1 in that silica A
The second embodiment is the same as the first embodiment except that 0.5 parts by weight of silica A-3 is used and the hardness of the secondary transfer bias roller 14 is changed to 45 °. Comparative Example 3 is the same as Example 1 except that 1.4 parts by weight of silica B-4 was used as silica B in Example 1.

Comparative Example 4 differs from Example 1 in that the hardness of the secondary transfer bias roller 14 was changed to 25 ° and the contact pressure of the secondary transfer bias roller 14 with the intermediate transfer belt 10 was changed to 3000 Pa. The rest is the same as in the first embodiment. In Comparative Example 5, in Example 1, 0.3 parts by weight of silica A-3 was used as silica A, 1.4 parts by weight of silica B-4 was used as silica B, and the hardness of the secondary transfer bias roller 14 was changed. Is changed to 80 °, and the rest is the same as the first embodiment.

FIG. 3 shows each of the silicas A-1 to A-3 described above.
The processing oils of B-1 to B-4, the oil processing amount, the average particle diameter, and the coupling processing are shown. FIG. 4 shows the results of the evaluations for Examples 1 to 7 and Comparative Examples 1 to 4 described above.
The evaluation results of the transfer blur, the image length variation in the feed direction, and the white stripe are double circles or circles. In Examples 3 and 5, the transfer blur, the image length variation in the feed direction, and the evaluation result of the white stripe are double circles. Or it became ○.

However, Comparative Examples 1 and 2 were not practical because there was a dropout during transfer and there was a problem in forming a thin layer on the developing roller. In Comparative Example 3, a dropout occurred during transfer.
In Comparative Example 4, it was impossible to achieve both the transfer blur and the image length variation in the feed direction. In Comparative Example 5, a dropout occurred during transfer.

As described above, in the above embodiment, the charge is applied by contacting the intermediate transfer belt 10 as the image carrier for carrying the toner image obtained by visualizing the electrostatic latent image and the back surface of the transfer material 22. And a secondary transfer bias roller 14 as transfer means for transferring the toner image on the image carrier 10 to the transfer material 22. The toner comprises at least a binder resin and a charge control agent, and Since it contains at least two kinds of inorganic fine powders having different average particle diameters and at least one of the at least two kinds of inorganic fine powders has been subjected to surface treatment with silicone oil, An image forming apparatus using a transfer unit of a transfer method, without any hollowness regardless of the thickness of the transfer material or the material of the transfer material, and achieving both the hollowness, the transfer blur, and the prevention of image length variation. Can, it is possible to obtain a good image.

The inorganic fine powder is silica having two kinds of different average particle diameters. Of these two kinds of silica, silica not subjected to surface treatment with silicone oil is subjected to silane coupling treatment. By doing so, it is possible to achieve both hollowing, transfer blurring, and prevention of image length variation, and a good image can be obtained.

Further, among the inorganic fine powders composed of the two types of silica, when the small particle size is silica A and the large particle size is silica B, when the silica A has an average particle size Dt of the toner. Average particle size Sa and average particle size Db of silica B
Satisfying the relationship of Da ≦ Dt / 1000 Dt / 100 ≦ Db ≦ Dt / 10 respectively, it is possible to prevent hollowing out and obtain a toner having good fluidity.

Further, the addition amount of the silica A having a small particle diameter in the inorganic fine powder composed of the two kinds of silica is 0.2 to 1.5% by weight with respect to the toner particles. When the addition amount of the silica B having a small particle diameter in the inorganic fine powder made of silica is 0.5 to 3.0% by weight based on the weight of the toner particles, hollow toner can be prevented and the toner having good fluidity can be prevented. Can be obtained.

The average particle diameter Dt of the toner is 5 ≦ D
When t ≦ 10 μm, hollow holes and toner scattering can be prevented, and a high-definition image can be obtained. In addition, the silica B having a small particle diameter in the inorganic fine powder composed of the two types of silica is silica that has been surface-treated with silicone oil, so that it is possible to prevent hollowing out.

The transfer means 14 has a roller hardness of 7
The transfer pressure of the transfer roller 14 is not more than 5000 Pa and not more than 25 Pa.
When the pressure is in the range of 000 Pa or less, it is possible to achieve both the prevention of voids and the prevention of transfer blur and variation in image length. Further, a transfer roller 14 as the transfer unit
Is -0.5 with respect to the peripheral speed of the image carrier 10.
By being in the range of% ≦ Vt ≦ + 0.5%, it is possible to prevent transfer blur and image length variation. In addition, since the image carrier 10 is an intermediate transfer body that carries a plurality of color toners, it is possible to obtain a good full-color image without a hollow portion.

The above-described embodiment is for the purpose of facilitating the understanding of the present invention, and does not limit the present invention. For example, the above embodiment is a color image forming apparatus using an intermediate transfer belt as an image carrier, but the present invention is not limited to this, and a photosensitive drum, a photosensitive belt,
The present invention can be applied to an image forming apparatus using all image carriers such as an intermediate transfer drum.

[0077]

As described above, according to the first aspect of the present invention, the image forming apparatus using the transfer unit of the contact transfer system can eliminate the hollow portion regardless of the thickness of the transfer material or the material of the transfer material. In addition, it is possible to achieve both the hollowing, the transfer blur, and the prevention of the variation in the image length, so that a good image can be obtained. According to the second aspect of the present invention, with the above-described configuration, it is possible to achieve both the hollowing, the transfer blur, and the prevention of the image length variation, and a good image can be obtained.

According to the third aspect of the present invention, with the above-described configuration, it is possible to prevent hollowing out and obtain a toner having good fluidity. According to the fourth aspect of the present invention, with the above-described configuration, it is possible to prevent hollowing out and obtain a toner having good fluidity. According to the fifth aspect of the present invention, with the above-described configuration, it is possible to prevent hollowing out and toner scattering, and to obtain a high-definition image.

According to the sixth aspect of the present invention, the above-described configuration can prevent the occurrence of a hollow. According to the invention according to claim 7, with the above configuration, it is possible to achieve both the prevention of the center defect and the prevention of the transfer blur and the variation in the image length. According to the eighth aspect of the present invention, the above configuration can prevent transfer blur and image length variation.
According to the ninth aspect of the present invention, it is possible to obtain a good full-color image without a hollow portion by the above configuration.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of the present invention.

FIG. 2 is an enlarged view showing the vicinity of a developing roller of the embodiment.

FIG. 3 is a diagram showing evaluation results of each of Examples and Comparative Examples of the present invention.

FIG. 4 is a view showing a treated oil of silica, an oil treatment amount, an average particle diameter, and a coupling treatment used in each embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 4 Charger 5 Exposure means 6 Yellow developing device 7 Magenta developing device 8 Cyan developing device 9 Black developing device 10 Intermediate transfer belt 11 Belt transfer bias roller 14 Secondary transfer bias roller 15 Secondary transfer unit 16 Contact / separation mechanism 22 Transfer material.

Claims (9)

[Claims] An image bearing member for carrying a toner image obtained by visualizing an electrostatic latent image; and a toner image on the image bearing member being transferred by contacting a back surface of the transfer material to apply a charge. The toner comprises at least a binder resin and a charge controlling agent, and contains at least two kinds of inorganic fine powders having different average particle diameters. An image forming apparatus, wherein at least one kind of inorganic fine powder is subjected to a surface treatment with silicone oil. 2. An image forming apparatus according to claim 1, wherein said inorganic fine powder is silica having two kinds of different average particle diameters, and of said two kinds of silica, a surface treatment is performed with silicone oil. An image forming apparatus, wherein the silica that has not been treated has been subjected to a silane coupling treatment. 3. The image forming apparatus according to claim 1, wherein, among the inorganic fine powders composed of the two types of silica, those having a small particle size are silica A and those having a large particle size are silica B. The average particle diameter Sa of the silica A and the average particle diameter Db of the silica B with respect to the average particle diameter Dt of the toner satisfy the relationship of Da ≦ Dt / 1000 Dt / 100 ≦ Db ≦ Dt / 10, respectively. Image forming device. 4. The image forming apparatus according to claim 1, wherein the amount of the silica A having a small particle diameter in the inorganic fine powder composed of the two kinds of silica is 0. 2 to 1.5% by weight, and the addition amount of the silica B having a small particle diameter in the inorganic fine powder composed of the two kinds of silica is 0.5 to 3.0% by weight with respect to the toner particles. An image forming apparatus comprising: 5. The image forming apparatus according to claim 1, wherein said toner has an average particle diameter Dt of 5 ≦ Dt ≦ 1.
An image forming apparatus characterized by being in a range of 0 μm. 6. The image forming apparatus according to claim 2, wherein the silica B having a small particle diameter in the inorganic fine powder comprising the two kinds of silica is silica surface-treated with silicone oil. An image forming apparatus, comprising: 7. An image forming apparatus according to claim 1, wherein said transfer means has a roller hardness of 70.
And a contact pressure of the transfer roller with respect to the image carrier is 5000 Pa or more and 25000 Pa or less.
An image forming apparatus having the following range. 8. The image forming apparatus according to claim 1, wherein a peripheral speed Vt of a transfer roller as said transfer means is smaller than a peripheral speed of said image carrier. 0.5
% ≦ Vt ≦ + 0.5%. 9. The method of claim 1, 2, 3, 4, 5, 6, 7, or 8.
3. The image forming apparatus according to claim 1, wherein the image carrier is an intermediate transfer body carrying a plurality of color toners.