JP2920720B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming an image using an electrophotographic process, and more particularly to an image forming apparatus suitable for forming an electrophotographic process using contact transfer.

[0002]

2. Description of the Related Art In recent years, in an image forming apparatus using an electrophotographic process, contact transfer, more specifically, bias roller transfer, has been studied instead of conventional corona transfer in order to reduce the amount of ozone generated.

In order to realize bias roller transfer, a method of detecting the resistance value of a roller by applying a constant current and setting a transfer bias based on the detected value is disclosed in Japanese Patent Application Laid-Open No. 2-123385. (Hereinafter, this method is called ATVC control.) Also, Ja
In p29 of pan HardCopy 91 Fall, it is stated that the resistance value of the transfer roller in the bias roller transfer system is at least 5.16 × 10 ⁸ Ω and the transfer voltage is at least 1200 V or more.

On the other hand, since the optimum voltage for transfer fluctuates due to fluctuations in the physical properties (resistance, dielectric constant, etc.) of the transfer target (mostly paper), a method of detecting the physical properties and setting the optimum bias is used. For example, Japanese Patent Application Laid-Open No.
8081.

Japanese Patent Application Laid-Open No. 1-195459 proposes to use a toner to which a fluidity-imparting agent is externally added in order to improve the cleaning property.

As described above, when the conventional technology is overviewed, in the case of the bias roller transfer, the transfer roller having a high resistance has been replaced by an A.
It has been used well by using complicated detection means such as TVC control.

[0007]

As described in the prior art, in the bias roller transfer system, it is necessary to set the transfer bias by detecting the roller resistance or by detecting the physical property value of the object to be transferred, for example, the resistance value. As a result, the configuration of the apparatus becomes complicated, which is disadvantageous in terms of reliability and cost of the apparatus. In addition, several k
There is a problem that a high voltage power supply of V is required and cost and safety are disadvantageous.

[0008]

A charging means for charging at least the latent image carrier, an exposure means for irradiating the charged latent image carrier with light to form an electrostatic latent image pattern, An image forming apparatus including a developing unit for applying a toner to make the image visible, a transfer unit for transferring the developed toner, and a cleaning unit for removing the toner remaining on the latent image carrier after the transfer, wherein the developing unit is The transfer member is a one-component press-contact developing system, and the transfer means has a transfer roller having a resistance of 5 × 10 ⁸ Ω or less in an environment of a temperature of 10 ° C. and a relative humidity of 15% RH. The toner is obtained by externally adding 0.4 to 1.4 wt% of an external additive whose surface is treated with silicone oil to the resin base particles. Further, an external additive surface-treated with hexamethyldisilane was used for the toner, and 0.4 to 1.2 with respect to the resin base particles.
wt% is externally added. Further, the toner is characterized in that an external additive whose surface is treated with dimethyldichlorosilane is externally added to the resin base particles by 0.4 to 1.0 wt%.

Further, a nip width between the latent image carrier and the transfer roller is 2.5 to 7.5 mm.

[0010]

[0011]

FIG. 2 shows the relationship between transfer bias and transfer efficiency in order to systematically grasp the prior art. It is generally known that the transfer efficiency is required to be about 80% or more in order to perform good transfer, and that the optimum bias of the transfer efficiency changes depending on the resistance value of the transfer object, the roller resistance, and the like. From FIG. 2, low temperature,
It can be seen that there is no transfer bias that simultaneously satisfies the 80% transfer efficiency line in a low-humidity environment (hereinafter referred to as an LL environment) and a high-temperature and high-humidity environment (hereinafter referred to as an HH environment), that is, constant voltage control is impossible. .

The present invention provides: As the amount of the external additive of the toner increases, the voltage at which the transfer efficiency falls in the HH environment (voltage at point A in FIG. 2)
Control at a constant voltage regardless of the environment.

2. By setting the transfer nip width to 2.5 mm or more, the voltage at which the transfer efficiency rises in the LL environment (the voltage at point B in FIG. 2) is reduced, and the range that can be controlled with a constant voltage is expanded.

3.1.2 is 5 in more detail than the low resistance roller.
It is possible with a transfer roller of × 10 ⁸ Ω or less.

4. Further, by setting the transfer nip width to 7.5 mm or less, it is possible to realize contact transfer without transfer defects such as a hollow portion.

5. By optimizing the amount of the external additive depending on the type of the external additive, the fog on the latent image carrier can be suppressed to a certain amount or less when the one-component pressure contact developing system is used.

It is based on the finding.

[0018]

FIG. 1 is a schematic sectional view of a contact transfer device and an image forming apparatus according to an embodiment of the present invention. In FIG. 1, a latent image carrier 1 has a photosensitive layer 3 having an organic or inorganic photoconductivity formed on a conductive support 2 and rotates at a process speed of 30 mm / sec at a diameter of 30 mm. A charging roller 4 suspended by an elastic body such as a spring or a charging member 4 such as a charging blade having elasticity is pressed against the latent image carrier 1 with a light load of about several gf / mm. A voltage is applied to the charging member 4 by the charging bias applying means 5 to charge the photosensitive layer 3 to a predetermined potential (-600 V). After the latent image carrier 1 is charged in this way, the light emitted from the light source 6 such as a laser or an LED is formed by a scanning optical system using a lens and a polygon scanner or a 1: 1 image forming optical system using a fiber array. Exposure means 8 for selectively irradiating the photosensitive layer 3 with light according to an image through the image optical system 7 obtains a potential contrast on the latent image carrier 1 to form an electrostatic latent image pattern. On the other hand, the developing device 9 is for transporting and developing the toner 10, and the developing member 11 for transporting the toner 10 is a device in which a conductive elastic body 13 is arranged concentrically around the outer periphery of a shaft 12. The toner 14 supplied to the vicinity of the developing member 11 by the member 14 is held on the developing member 11, and the thin layer is regulated to an appropriate amount by a plate-like regulating member 15 made of non-magnetic or magnetic metal or resin. The thin layer 10 is conveyed by rotating the roller 11 and supplied to the developing unit. The developing member 11 is pressed against the latent image carrier 1 with a predetermined pressure, and when the toner 10 is transported to a developing section where the latent image carrier 1 and the developing member 11 come into contact, the latent image carrier 1 Potential contrast and developing bias applying means 1
A so-called one-component pressure-contact development system is adopted, in which the toner 10 charged in accordance with the developing electric field by the developer 6 transfers to the latent image carrier 1 and the electrostatic latent image pattern is visualized. Note that a seal member 17 is provided at the opening of the developing device 9 and the seal member 1
7 by lightly contacting the developing member 11
The fall of the toner after the development and the scattering of the toner from the inside of the developing device 9 are prevented. Further, the toner 10 developed on the latent image carrier 1 is suspended against the latent image carrier 1 by an elastic body such as a spring and pressed against the light image with a light load of about several gf / mm so that the transfer nip is 2.5 mm. Transfer roller 1 with a diameter of 16 mm
8, a voltage is applied by a transfer bias applying unit 19 to transfer the image onto the transfer target 20. The toner transferred onto the transfer body 20 is fixed to the transfer body 20 by heat or pressure, and a desired image is obtained. After the transfer, the latent image carrier 1 rotates to reach the cleaning device 21 and the rake sheet 22
The transfer residual toner adhered to the latent image carrier 1 by a cleaning member 23 formed of a resin blade or the like and pressed against the latent image carrier 1 while lightly contacting the latent image carrier 1 to prevent the toner from scattering. After removing unnecessary charges on the latent image carrier 1 by the static eliminator 24, the latent image carrier 1 is charged again and the above process is repeated to continuously form an image.

Next, the transfer roller 18 will be described in more detail. The transfer roller 18 is an elastic foam roller provided with a conductive foam layer on a metal shaft, and has a linear pressure of gf /
The latent image carrier 1 is stably pressed against the latent image carrier 1 via the transfer-receiving member 20 at a speed of mm and rotated at substantially the same peripheral speed as the latent image carrier 1. Further, the transfer roller 18 does not easily adhere the toner, does not contaminate the latent image carrier 1, does not stick easily, does not easily wear, has a uniform and flexible surface, and is Has good contact properties. Roller resistance value was measured by the following method, from ^{10 4} Ω 10 10 Ω
Use up to rollers. Table 1 summarizes the roller physical property values used. The method of measuring the roller resistance in FIG. 3 will be described.
The roller 25 has a conductive plate 26 with a load of 500 gf on both shaft ends.
The resistance meter 27 is connected between the shaft of the roller 25 and the conductive plate 26 to measure the resistance of the roller 25. The applied voltage at the time of resistance measurement is 500V. Unless otherwise specified, the LL environment is 10 ° C. and 15% RH, and the HH environment is 35%.
° C 65% RH.

[0020]

[Table 1]

Next, the transfer object 20 will be described. Paper is often used for the transfer receiving body 20. Therefore, paper having several levels of resistance was prepared by controlling the humidity in the LL environment and the HH environment. The resistance value of the paper was converted into a volume resistivity by connecting an electrometer manufactured by Advantest Corporation to a resistance chamber R12702A manufactured by Advantest Corporation and measuring the resistance value. The measurement was carried out while being sandwiched between electrodes, and the measurement load was 100 gf / cm ² . The applied voltage was 20V. As a result, the volume resistivity of the paper having the highest resistance in the LL environment was 10 ¹⁴ Ωcm. (Hereinafter referred to as high-resistance paper) The volume resistivity of the paper having the lowest resistance in the HH environment was 10 ⁸ Ωcm. Next, the toner 10 used in the present invention will be described in detail. As the toner used in the present invention, a magnetic or non-magnetic toner having a particle size of 5 to 20 μm produced by a general kneading and pulverizing method, a spray drying method, or a polymerization method can be used.

The specific toner composition is shown below.

(Toner A) Polyester resin 88 wt% Polypropylene wax 5 wt% Charge control agent 1 wt% Carbon black 6 wt% The raw materials having the above composition are kneaded by a screw extruder and roughly ground. Next, the mixture was finely pulverized with a jet pulverizer and classified to prepare toner base particles having a volume average particle size of 9 μm.

Next, using a Henschel mixer, the particle size is reduced to 0.
016 μm of external additive A was contained on the surface of the toner base particles in an amount of 0.2 to 1.6 wt% to prepare a toner. The external additive A was prepared by subjecting dimethylsilicone oil to surface treatment on dry process silica. The hydrophobicity of the external additive was 60% or more. Table 2 shows the physical properties of the prepared toner. The volume resistivity of the toner is obtained by pressing the toner into a pellet having a thickness of 0.5 mm, placing electrodes on the top and bottom, applying a load of 1 kgf / cm ² , applying a voltage of 250 V, and calculating the current value. did. The measurement was performed in a dry desiccator replaced with a nitrogen atmosphere. The charge amount was measured using a blow-off charge amount measuring device manufactured by Toshiba Chemical Corporation. The degree of aggregation was measured with a powder tester manufactured by Hosokawa Micron Corporation.

[0025]

[Table 2]

Further, the same toner was prepared except that the toner composition was as follows and the kind of the external additive was changed.

(Toner B) 89% by weight of polyester resin 5% by weight of polypropylene wax 1% by weight of charge control agent 5% by weight of carbon black The raw material having the above composition is kneaded by a screw extruder and roughly ground. Next, the mixture was finely pulverized with a jet pulverizer and classified to prepare toner base particles having a volume average particle diameter of 10 μm.

Next, the particle size was reduced to 0.1 using a Henschel mixer.
The following five toners were prepared by incorporating 012 μm of the external additive B on the surface of the toner base particles at 0.2 to 1.6 wt%. Toner B1 (external additive amount 0.2 wt%), toner B2
(0.4% by weight of external additive), toner B3 (0.4% by weight of external additive).
8 wt%), toner B4 (1.2 wt% of external additive), toner B5 (1.6 wt% of external additive), and external additive B obtained by surface-treating dimethyldichlorosilane on dry silica. Was. The hydrophobicity of the external additive was 40 to 50%. The physical properties of the prepared toners B1 to B5 are the same as those of the toners A1 to A5.
, Except that the volume resistivity was slightly higher.

Further, a similar toner was prepared except that the toner composition was as follows and the kind of the external additive was changed.

(Toner C) 89% by weight of polyester resin 5% by weight of polypropylene wax 1% by weight of charge control agent 5% by weight of carbon black The raw material having the above composition is kneaded with a screw extruder and roughly ground. Next, the mixture was finely pulverized with a jet pulverizer and classified to prepare toner base particles having a volume average particle diameter of 10 μm.

Next, the particle size was reduced to 0.1 using a Henschel mixer.
016 μm of external additive C was contained on the surface of the toner base particles in an amount of 0.2 to 1.6 wt% to prepare the following five toners. Toner C1 (external additive amount 0.2 wt%), toner C2
(0.4% by weight of external additive), toner C3 (0.4% by weight of external additive).
8 wt%), toner C4 (external additive amount 1.2 wt%), toner C5 (external additive amount 1.6 wt%), and external additive C obtained by surface-treating hexamethyldisilane on dry silica. . The hydrophobicity of the external additive was 50 to 60%. The physical properties of the toners C1 to C5 were the same as those of the toners A1 to A5 except that the volume resistivity and the charge amount were slightly higher.

Using the transfer roller 18, transfer object 20, and toner 10 described above, the transfer efficiency was examined by the above-described apparatus (FIG. 1). Details are described below.

FIG. R3 b
No. shown in Table 2 using a A1 to A5 toner
Adjust transfer efficiency when printing on high-resistance paper in LL environment
It is a solid result. Transfer efficiency rises regardless of toner type
The rise was almost 550V. FIG. 4 (b) is shown in Table 1.
No. No. 3 shown in Table 2 using the R3 roller. A1
To A5 toner on low resistance paper in HH environment
This is the result of examining the transfer efficiency when the transfer was performed. Increased amount of external additives
The lower the voltage of the transfer efficiency, the higher the voltage. Also,
Image quality such as reproducibility of fine lines and isolated dots other than the shooting efficiency
It was found that the higher the amount of the external additive, the better. This effect is
It is not clear, but there is generally a fall in transfer efficiency
The reason is that the voltage applied to the toner layer
It is said to fall. Therefore, the amount of external additives is large.
The better the fluidity of the toner, the more fine voids between toners
And the voltage at which the discharge phenomenon occurs increases,
It is thought that it improved. H based on FIGS. 4A and 4B
The transfer of the LL environment from the falling voltage of the transfer efficiency in the H environment
The value obtained by subtracting the voltage at the start of the shooting efficiency (hereinafter the voltage overlap value
FIG. 5 shows the relationship between the external additives. this
The condition that becomes positive in the figure is the condition that enables constant voltage control.
Is equivalent to The same evaluation was performed for toners B and C.
FIG. 6 shows the relationship between the voltage overlap value and the amount of the external additive.
You. From the above results, depending on the toner composition and the type of external additive,
0.4% or less when using this roller (No. R3)
It turns out that constant voltage control is possible with the above external additive amount
did. Other rollers (No. R1 to R6) in Table 1
The transfer efficiency in LL and HH environments
FIG. 7 shows the relationship between the voltage overlap value and the amount of the external additive.
You. The toner used was toner A. Roller No. From R1
R4 gave exactly the same result, but roller No. About R5
Constant voltage control is possible with an external additive amount of 0.8 wt% or more
Was. In addition, the roller No. R6 has a constant voltage controllable area
Did not exist. From this result, the roller that can control the constant voltage
The resistance range of the roller No. R5 or less, that is, LogR is
9.5 or less (3 ×10 ⁹ Ω) More preferably roller N
o. 4 or less, that is, LogR is 8.7 (5 ×10
⁸ Ω). Also, the amount of external additives
In order to examine the more preferable range, the amount of the external additive of the toner A is reduced.
Image quality evaluation (fine line, isolated
Dot reproducibility). Roller No. Using 3
Was. Table 3 shows the results.

[0034]

[Table 3]

When judging finer image quality other than transfer efficiency, it was found from this image quality evaluation that high image quality can be obtained by adding an external additive in an amount exceeding 0.6 wt%. Therefore, the optimum range of the amount of the external additive is set at 0.1 from the transfer efficiency.
4 wt% or more, and a more preferred range is an amount exceeding 0.6 wt%.

Consideration will be given to the effect that the voltage overlap value differs depending on the roller resistance and the amount of the external additive as described above. FIG.
Is a diagram in which the bias roller transfer is modeled as an equivalent circuit.
r is the roller resistance value, Rp is the transfer object resistance value, Rt is the toner resistance value, Cp is the transfer object capacity, Ct is the toner capacity, C
pc is the capacity of the latent image carrier. Vt is a transfer bias. The partial pressure of the toner layer was calculated by replacing the capacitance component of the lumped constant circuit network of FIG. 8 with an equivalent resistance. The transfer bias at which the transfer efficiency rises in the LL environment was almost the same regardless of the amount of the toner external additive from the experiment (FIG. 4A). Therefore, when the transfer efficiency rises, the voltage applied to the toner layer is the same for all toners. 100V was assumed. Further, the transfer bias at which the transfer efficiency falls under the HH environment is different depending on the amount of the toner external additive from the experiment (FIG. 4B). Therefore, when the transfer efficiency falls, the voltage applied to the toner layer, that is, the discharge start voltage is reduced by the external additive. It was calculated under the following conditions, assuming that the amount increased as the amount increased. The following numerical values were used as calculation parameters.

The image portion surface potential: -100V Rr: 10 ⁴ from ¹⁰ 10 Ω Cpc: relative dielectric constant of 3, thickness 20 [mu] m Cp: specific dielectric constant of 3, thickness 80μm Rp: 10 ¹⁴ Ω cm (high-resistance paper) 10 ⁸ [Omega] cm (Low resistance paper) Ct: relative dielectric constant 3, thickness 20 μm Rt: 10 ¹⁷ Ωcm Process speed: 30 mm / s Width: 220 mm Nip: 2.5 mm Voltage required for the toner layer to increase transfer efficiency in LL environment: 100 V It is assumed that the voltage applied to the toner layer when the transfer efficiency falls in the HH environment: It is assumed that the voltage varies depending on the amount of the external additive as shown below. 0.2 wt%: 200 V 0.4 wt%: 300 V 0.8 wt%: 400 V 1 FIG. 9 shows the point at which the voltage applied to the toner layer becomes 100 V when printing on high-resistance paper in the LL environment (transfer efficiency is high). Up and assumed voltage) and in HH environment that voltage applied to the toner layer in a low-resistance paper printing becomes 600V (external additive amount 1.6 wt%
FIG. 5 is a diagram showing the transfer bias on the horizontal axis and the roller resistance on the vertical axis, assuming that the transfer efficiency falls when the toner is used. In FIG. The resistance values of R1 to R6 were plotted at the corresponding positions, and the voltage overlap value indicated by A in FIG. 9 was calculated. FIG. 10 shows the relationship between the amount of the roller and the external additive and the voltage overlap value obtained in the same manner for the other external additive amounts. This calculation result shows that a roller having a lower resistance and a larger amount of the external additive are more advantageous for constant voltage control, although they are not completely correlated with the experimental data shown in FIG.

FIG. 11 (a) shows the data of No. 1 shown in Table 1. R3 and the No. 3 roller shown in Table 2. This is a result of examining the transfer efficiency when printing on high-resistance paper in an LL environment using the B2 toner (the amount of the external additive is 0.4 wt%) using the transfer nip width as a parameter. The transfer nip width was changed in the range of 0.5 to 9.5 mm by changing the pressure of the transfer roller against the latent image carrier. From FIG. 11A, it was found that when the transfer nip width is narrow (2 mm or less), the voltage at which the transfer efficiency rises is largely different, and when the transfer nip width is 2.5 mm or more, the voltage rises at almost the same voltage. FIG.
R3 and the No. 3 roller shown in Table 2. This is a result of examining the transfer efficiency when printing on low-resistance paper in an HH environment using the B2 toner using the transfer nip width as a parameter. It was found that the voltage at which the transfer efficiency dropped was almost the same regardless of the transfer nip width. FIG. 11 (a), (b)
The relationship between the voltage overlap value of the toner B2 and the transfer nip width is shown based on FIG. 12, and the results of the same evaluation for the toners A2 and C2 are shown in FIG. From this figure, it was found that there was a region where constant voltage control was possible when the transfer nip width was 2.5 mm or more.

It has been found that the upper limit of the transfer nip width can be determined by the nip width at which image hollowing occurs. Details are described below. The hollow part of an image is one of transfer defects in which a character is printed in a bag character shape and a thin line is printed as a dotted line because toner at the center of an image portion is not transferred when printing a character, a thin line, or the like. Therefore, the hollow must not be included in configuring the transfer device. FIG. 13 is a diagram showing the results of evaluating the relationship between the transfer nip width and the hollow area in five steps. The allowable line is cleared when the nip is 8.5 mm or less under the LL environment and 7.5 mm or less under the HH environment. I understood. From this result, it was found that the optimum transfer nip width for obtaining an image without hollowing under all environments was 7.5 mm or less. From the above results, a preferable range of the transfer nip width is 2.5 mm to 7.5 mm.

In the low-resistance roller, when the amount of the external additive is increased, the voltage value at which the transfer efficiency falls in the HH environment increases, and when the transfer nip width is set to 2.5 mm to 7.5 mm, the center dropout occurs. It has been described that there is an area where there is no transfer failure, such as transfer failure, and that constant voltage control can be performed.However, in the present image forming apparatus using the one-component pressure contact developing method, the latent image carrier is increased by increasing the amount of the external additive. It was found that the phenomenon that the toner adheres to the surface of No. 1 during solid white printing (hereinafter referred to as fogging) becomes remarkable. Fogging is unfavorable for processes such as the cause of paper back stains and the increase in waste toner, and must be suppressed to a certain amount or less. In addition, it was found that it occurs more in the HH environment than in the LL environment. FIG. 14 is a diagram showing the relationship between the amount of fogging and the amount of the external additive in the HH environment.
The fog was measured by transferring the tape on the latent image carrier 1 and measuring the toner amount. When the amount of the external additive exceeds 1.0%, it rapidly increases, and at 1.6%, fogging exceeding the allowable value (0.03 mg / cm ² ) occurs in all toners (toners A, B, and C). . From this result, it was found that the upper limit of the amount of the external additive in the image forming apparatus using the one-component pressure welding development can be determined by the fog amount in the HH environment. Further, it was found that the upper limit value differs depending on the type of the external additive as follows. Toner A using an external additive surface-treated with dimethyl silicone oil is 1.4 wt% or less, toner B using an external additive with dimethyl dichlorosilane surface treated is 1.0 wt% or less,
It became clear that the toner F using the external additive obtained by surface-treating hexamethyldisilane clears the fogging tolerance at 1.2 wt% or less.

The toner composition used in the contact transfer device and the image forming device in the present invention is not particularly limited, and a general one can be used. For example, as the binding resin, polystyrene and copolymers such as hydrogenated styrene resin, styrene / isobutylene copolymer, ABS resin, ASA resin, AS resin, AAS resin, ACS resin, AES resin, styrene
P-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene cross-linked polymer, styrene
Butadiene / chlorinated paraffin copolymer, styrene / allyl / alcohol copolymer, styrene / butadiene rubber emulsion, styrene / maleic acid ester copolymer, styrene / isobutylene copolymer, styrene / maleic anhydride copolymer, acrylate Resin or methacrylate resin and its copolymer, styrene / acrylic resin and its copolymer, for example, styrene / acrylic copolymer, styrene / diethylamino / ethyl methacrylate copolymer, styrene / butadiene / acrylic acid Ester copolymer, styrene / methyl methacrylate copolymer, styrene / n-butyl methacrylate copolymer, styrene / diethylamino / ethyl methacrylate copolymer, styrene / methyl methacrylate / n-butyl acrylate Over preparative copolymer, styrene-methyl methacrylate-butyl arylate-N-(ethoxymethyl) acrylamide copolymer, styrene-glycidyl methacrylate copolymer, a styrene-butadiene-
Dimethyl / aminoethyl methacrylate copolymer, styrene / acrylate / maleate copolymer, styrene / methyl methacrylate / acrylic acid 2
-Ethylhexyl copolymer, styrene / n-butylarylate / ethyl glycol methacrylate copolymer,
Styrene / n-butyl methacrylate / acrylic acid copolymer, styrene / n-butyl methacrylate / maleic anhydride copolymer, styrene / butyl acrylate /
Isobutylmaleic acid half ester / divinylbenzene copolymer, polyester and its copolymer, polyethylene and its copolymer, epoxy resin, silicone resin, polypropylene and its copolymer, fluorine resin, polyamide resin, polyvinyl alcohol resin, One type of polyurethane resin, polyvinyl butyral resin, or the like, or a mixture of two or more types can be used.

As a coloring agent, a black dye / pigment such as carbon black, spirit black or nigrosine is used. For color, phthalocyanine, rhodamine B
Dyes such as lake, Solar Pure Yellow 8G, quinacridone, polytungstophosphoric acid, indasulene blue, and sulfonamide derivatives can be used. Furthermore,
As a dispersant, metal soap, polyethylene glycol and the like, and as a charge control agent, an electron-accepting organic complex, chlorinated polyester, nitrophenic acid, a quaternary ammonium salt, a pyridinyl salt, and the like can be added. As the magnetic agent, fine particles that are chemically stable when dispersed in the binder resin and have a particle size of 5 μm or less are preferable. For example,
Fe, Co, Ni, Cr, Mn metal powder, Fe3 O4, F
Metal oxides such as e2O3, Cr2O3, and ferrite, alloys that exhibit ferromagnetism by heat treatment, such as alloys containing manganese and copper, and the like, may be preliminarily treated with a coupling agent or the like. In addition, polypropylene wax, polyethylene wax and the like can be added as a release agent. Further, as other additives, zinc stearate, zinc oxide, cerium oxide and the like can be used.

As the external additive in the contact transfer device and the image forming device of the present invention, various types can be used. For example, inorganic fine particles such as metal oxides such as silica, alumina and titanium oxide, and composite oxides thereof. Further, organic fine particles such as acrylic fine particles can be used.

As the surface treatment agent for the external additive in the contact transfer device of the present invention, a silane coupling agent, a titanate coupling agent, a fluorine-containing silane coupling agent, a silicone oil, or the like can be used. The hydrophobicity of the external additive treated with the above treating agent is preferably 40% or more as measured by a conventional methanol method. If it is less than this, the triboelectric charge is undesirably reduced due to the adsorption of moisture under high temperature and high humidity. The particle size of the external additive is preferably from 0.001 to 1 μm.

As the transfer roller used in the present invention, in addition to the elastic foam roller described in the embodiment, a single-layer elastic conductive roller using a conductive foam with a skin, a bleeding prevention layer, a resistance adjusting layer, It was confirmed that the same effect was obtained even when a multilayer elastic conductive roller provided with a protective layer and the like was used. Further, when a transfer roller having little environmental dependence (less than one digit in the LL environment and the HH environment) is used, even if the resistance value exceeds 5 × 10 ⁸ Ω, the amount of the external additive 0.4 W which is equivalent to that of the present invention is 0.4 W.
It has been found that a good contact transfer device can be constructed with a constant voltage by using toner of t% or more.

It is needless to say that the use of the contact transfer device or the image forming apparatus of the present invention together with the conventional roller resistance detection means and paper resistance detection means expands the control range of the transfer conditions.

[0047]

As described above, according to the present invention, since the amount of the external additive and the nip width are optimized by using the low-resistance roller, the range in which the transfer can be performed well is expanded, and the control of the transfer condition can be performed with a constant voltage. This method can be performed at a low voltage, and eliminates the need for roller resistance detection means, paper resistance detection means, a high voltage power supply of several kV, etc., which are conventionally required, and is advantageous in reducing the size of the apparatus and reducing the manufacturing cost, and has high reliability. A transfer device can be provided. Also,
Since a low-resistance roller whose production cost is relatively low can be used as the transfer roller, it is advantageous in that the apparatus cost can be further reduced. In addition, since the material for surface treatment of the external additive and the amount of the external additive have been optimized, a highly reliable image forming apparatus with reduced fog and no paper back stain can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a contact transfer device and an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an operation using a conventional example.

FIG. 3 is a diagram showing a method for measuring the resistance of a roller.

FIG. 4A is a diagram showing the relationship between the transfer efficiency and the amount of an external additive when printing on high-resistance paper in an LL environment. FIG. 6B is a diagram illustrating a relationship between transfer efficiency and the amount of an external additive when printing on low-resistance paper in an HH environment.

FIG. 5 is a view showing the relationship between the amount of the external additive and the voltage overlap value based on FIGS. 4 (a) and 4 (b).

FIG. 6 is a diagram illustrating a relationship between a type of a toner, an amount of an external additive, and a voltage overlap value.

FIG. 7 is a diagram illustrating a relationship between a roller type (roller resistance value), an amount of an external additive, and a voltage overlap value.

FIG. 8 is a diagram in which bias roller transfer is modeled as an equivalent circuit.

9 assumes a voltage applied to the toner layer when the transfer efficiency rises in the LL environment based on the equivalent circuit of FIG. 8, calculates a point at which the same voltage is obtained, and concludes the toner when the transfer efficiency falls in the HH environment. The figure which calculated and connected the point which becomes the same voltage assuming the voltage applied to a layer.

FIG. 10 is a diagram illustrating a relationship between a roller type (roller resistance value), an amount of an external additive, and a voltage overlap value calculated by calculating a voltage applied to a toner layer based on the equivalent circuit of FIG. 8;

FIG. 11A is a diagram illustrating a relationship between transfer efficiency and a transfer nip width when printing on high-resistance paper in an LL environment. (B) HH
FIG. 6 is a diagram illustrating a relationship between transfer efficiency and transfer nip width when printing on low-resistance paper under an environment.

FIG. 12 is a diagram showing a relationship between a transfer nip width and a voltage overlap value based on FIGS. 11A and 11B.

FIG. 13 is a diagram showing a relationship between a transfer nip width and an image missing phenomenon.

FIG. 14 is a graph showing the relationship between the amount of external additives and the amount of developed fog.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Latent image carrier 5 Charging member 8 Exposure means 10 Toner 11 Developing member 18 Transfer roller 20 Transfer object 23 Cleaning member

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor ▲ Hama ▼ Takashi 3-35-5 Yamato, Suwa-shi, Nagano Inside Seiko Epson Corporation (72) Inventor Masataka Isuzu 3-3-5 Yamato, Suwa-city, Nagano Prefecture No. Seiko Epson Co., Ltd. (72) Kinro Koga Inventor Seiko Epson Co., Ltd., 3-3-5, Yamato, Suwa-shi, Nagano Prefecture (56) References JP-A 1-195459 (JP, A) Hei 6-51554 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/16 G03G 9/08 G03G 15/08

Claims (4)

(57) [Claims] 1. A charging unit for charging at least a latent image carrier, an exposing unit for irradiating the charged latent image carrier with light to form an electrostatic latent image pattern, and applying toner to the electrostatic latent image pattern. An image forming apparatus comprising: a developing unit for developing a visible image; a transfer unit for transferring the developed toner; and a cleaning unit for removing toner remaining on the latent image carrier after the transfer. And the transfer means has a temperature of 10 ° C. and a relative humidity of 15% R
A transfer method in which a transfer roller having a resistance of 5 × 10 ⁸ Ω or less in an environment of H is brought into contact with the latent image carrier via a transfer object, wherein the toner is surface-treated with silicone oil. Is 0.4 to 1.4 w with respect to the resin base particles.
An image forming apparatus, wherein t% is externally added. 2. A charging unit for charging at least the latent image carrier, an exposure unit for irradiating the charged latent image carrier with light to form an electrostatic latent image pattern, and applying toner to the electrostatic latent image pattern. An image forming apparatus comprising: a developing unit for developing a visible image; a transfer unit for transferring the developed toner; and a cleaning unit for removing toner remaining on the latent image carrier after the transfer. And the transfer means has a temperature of 10 ° C. and a relative humidity of 15% R
A transfer method in which a transfer roller having a resistance of 5 × 10 ⁸ Ω or less in an environment of H is brought into contact with the latent image carrier via a transfer-receiving member, wherein the toner is surface-treated with hexamethyldisilane. 0.4-1.
An image forming apparatus wherein 2 wt% is externally added. 3. A charging unit for charging at least the latent image carrier, an exposure unit for irradiating the charged latent image carrier with light to form an electrostatic latent image pattern, and applying toner to the electrostatic latent image pattern. An image forming apparatus comprising: a developing unit for developing a visible image; a transfer unit for transferring the developed toner; and a cleaning unit for removing toner remaining on the latent image carrier after the transfer. And the transfer means has a temperature of 10 ° C. and a relative humidity of 15% R
H is a transfer method in which a transfer roller having a resistance of 5 × 10 ⁸ Ω or less in an environment of H is brought into contact with the latent image carrier via a transfer object, and the toner is surface-treated with dimethyldichlorosilane. Additives to resin base particles from 0.4 to
An image forming apparatus wherein 1.0 wt% is externally added. 4. The image forming apparatus of claim 1, 2, 3, characterized in that the nip width between the transfer roller and the latent image bearing member is 7.5mm from 2.5.