JP2003233223A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable image forming apparatus which reduces the sticking of toner to or the filming thereof on impression members thereby stably forming a high resolution image. <P>SOLUTION: The image forming apparatus has: an impression charging member 4 which performs contact charging of a latent image carrier 1; an exposure means 8 which forms an electrostatic latent image pattern by irradiating the latent image carrier with light; an impression developing member 11 which is disposed in pressure contact with the latent image carrier and performs impression development of the electrostatic latent image pattern; an impression transfer member 18 which performs impression transfer of the developed toner 10 to a recording material 20; and an impression cleaning member 23 which performs impression cleaning of the latent image carrier 1 at a linear pressure of 1 to 40 gf/mm after the transfer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for forming an image using an electrophotographic process, and more particularly,
The present invention relates to an image forming method suitable for constituting an electrophotographic process using pressure contact charging, pressure contact development, pressure contact transfer and pressure contact cleaning.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic process, corona charging or corona transfer has been used, but ozone is generated upon use thereof and adversely affects the environment. Therefore, in recent years, in order to reduce the amount of generated ozone, use of contact charging or contact transfer has been studied instead of conventional corona charging or corona transfer. Contact charging and contact transfer not only generate almost no harmful ozone, but also can be used at a lower voltage than corona charging and corona transfer, and are advantageous in terms of power supply.

For example, in Japanese Unexamined Patent Publication (Kokai) No. 3-293364, a releasable coating is provided on the contact charging member to prevent toner from filming on the contact charging member, while the polyester component is By using a toner that has been substituted with a functional group that contains a toner and externally added with a fluidity improver that has a low chargeability, toner charge-up can be prevented, toner cleaning performance can be improved, and toner charging to the contact charging member can be performed. To prevent mingling.

However, in the above-mentioned conventional example, since the volume average particle diameter of the toner is as small as 10 μm or less, when the external addition amount of the toner is made close to 2 wt% for the purpose of improving the fluidity, the pressure contact cleaning member such as the cleaning blade. Thus, only the external additive slips through and adheres to the contact charging member, and uneven charging occurs even if filming does not occur, and a desired electrostatic latent image pattern cannot be obtained.

Further, in JP-A-1-195459, a toner to which a fluidity-imparting agent such as hydrophobic silica is externally added is used to improve the cleaning property of a transfer roller used for contact transfer.

However, the toner contacting the pressure contact transfer member when the paper is not passed is not limited to one polarity, and the toner transferred to the transfer roller due to the cleaning bias is transferred to the backside of the paper as a stain on the back of the paper. . Such a phenomenon occurs not only in the charging polarity of the toner, but also in the case where the toner has a low resistance and is easily subjected to charge injection.

Further, in Japanese Patent Laid-Open No. 3-121462, 0.05 to 3 parts by weight of fine powder treated with silicone oil or silicone varnish is added to 100 parts by weight of the toner, and externally added toner is used. Suppresses voids in transfer.

However, when the amount of the fine powder is close to 2 parts by weight, only the external additive slips through the pressure contact cleaning member such as the cleaning blade and adheres to the contact charging member, and uneven charging occurs even if filming does not occur, which is desirable. The electrostatic latent image pattern cannot be obtained. Further, when the image is formed by using the pressure contact development, the development fog is generated under the high temperature and high humidity condition or when a large number of sheets are printed.

[0009]

In the above-mentioned prior art,
The charging member, the developing member, the transfer member, and the cleaning member, which are pressed against the latent image carrier due to the peeling of the external additive of the toner, the fluidity of the toner, etc., do not perform the sufficient functions, and the image quality is deteriorated, and It had reduced reliability.

The present invention is an improvement over such a prior art. The object of the present invention is to reduce the adhesion and filming of the toner to the pressure contact member, and reduce the uneven charging and the development fog to obtain a high resolution. It is to form a stable image. Still another object is to provide a small and highly reliable image forming method using a pressure contact member by the processes of charging, developing, transferring, and cleaning.

[0011]

In order to achieve the above object, the image forming method of the present invention comprises a pressure contact charging member which is in pressure contact with a latent image carrier to charge it to a predetermined potential, and the latent image carrier. Exposure means for irradiating light to form an electrostatic latent image pattern,
A pressure contact developing member which is arranged so as to be in pressure contact with the latent image carrier and applies toner to the electrostatic latent image pattern to make it visible, and a line of 1 to 40 gf / mm with respect to the latent image carrier. A pressure contact transfer member which is arranged so as to be in pressure contact with each other and transfers the developed toner onto a recording material, and is arranged so as to be in pressure contact with the latent image carrier, and remains on the latent image carrier after transfer. And a pressure contact cleaning member for removing the toner, and an image formed by the toner is formed on the recording material by the electrophotographic process. The toner has a primary particle average particle diameter of 10 n with respect to the resin mother particles.
The external additive of m or more is externally added in the range of 0.4 to 1.2 wt%. Further, the toner is characterized in that the release agent is internally added to the resin mother particles in the range of 1 to 5 wt%.

[0012]

FIG. 1 is a schematic cross-sectional view of an image forming apparatus in an embodiment of an image forming method of the present invention. In FIG. 1, the latent image carrier 1 is formed by forming a photosensitive layer 3 having organic or inorganic photoconductivity on a conductive support 2. A charging member 4 such as a charging roller suspended by an elastic body such as a spring or a charging blade having elasticity itself is pressed against the latent image carrier 1 with a light load of about several gf / mm, The charging member 4 is charged by the charging bias applying means 5.
A voltage is applied to the photosensitive layer 3 to charge it to a predetermined potential. After charging the latent image carrier 1 in this way, laser or LED
Light emitted from a light source 6 such as a light source is passed through an image forming optical system 7 such as a scanning optical system using a plurality of lenses and a polygon scanner or an equal-magnification image forming optical system using a fiber array according to an image. The exposure means 8 for selectively irradiating light 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 conveys and develops the toner 10, and the developing member 1 that conveys the toner 10.
The reference numeral 1 designates a conductive elastic body 13 concentrically arranged on the outer circumference of a shaft 12, and a developing member 1 is provided by a supply member 14.
The toner 10 supplied in the vicinity of 1 is held on the developing member 11, the thin layer is regulated to an appropriate amount by the plate-shaped regulating member 15 made of non-magnetic or magnetic metal or resin, and the developing member 11 is rotated. The thin layer toner 10 is conveyed 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 conveyed to the developing section where the latent image carrier 1 and the developing member 11 contact each other, the latent image carrier 1 Potential contrast and developing bias applying means 16
The toner 10 charged in accordance with the developing electric field is transferred to the latent image carrier 1 to visualize the electrostatic latent image pattern. The seal member 17 is provided in the opening of the developing device 9 and the seal member 17 is brought into light contact with the developing member 11 to drop the toner after development or scatter the toner from the inside of the developing device 9. Is being prevented.

Further, the toner 10 developed on the latent image carrier 1 is suspended from an elastic body such as a spring with respect to the latent image carrier 1 and is pressed against the latent image carrier 1 with a light load of about several gf / mm. A voltage is applied to the transfer member 18 such as a transfer belt by the transfer bias applying unit 19 to transfer the recording material 2
0 is transcribed. The toner transferred onto the recording material 20 is fixed on the recording material 20 by heat or pressure to obtain a desired image. After the transfer is completed, the latent image carrier 1 rotates to reach the cleaning device 21, and the scooping sheet 22 is brought into light contact with the latent image carrier 1 to prevent the toner from scattering, and the latent image carrier is formed by a resin blade or the like. The cleaning member 23 pressed against the body 1 removes the transfer residual toner and foreign matter adhering to the latent image carrier 1, and the static eliminator 24 removes unnecessary charges on the latent image carrier 1 and then recharges the latent image carrier 1. The above process is repeated to form images continuously. The toner collected by the cleaning device 21 may be sent to the developing device 9 again to recycle the toner.

Now, the charging member 4 will be described in more detail. The charging member 4 has a conductive rubber layer on a metal shaft, and a two-layer roller having a high resistance layer on the outer periphery of the conductive rubber layer is brought into pressure contact with the latent image carrier 1 at a linear pressure of several gf / mm. The latent image carrier 1 is charged to a predetermined potential by using discharge or charge injection. The charging bias is, for example, in the case of charging the latent image carrier 1 to -600V,
The discharge start voltage of -570V was added to this voltage -1170
When V is applied and an AC component is superimposed, an AC voltage of about ± 600 V is superimposed on the DC component described above. Further, the charging member 4 may be rotated at the same peripheral speed as the latent image carrier 1 or may be rotated or fixed at a different peripheral speed. Further, the charging member 4
Needless to say, the external additive of the toner does not easily adhere to the latent image bearing member 1, does not contaminate the latent image bearing member 1, does not easily stick to it, does not easily wear, and has a smooth surface and is in contact with the latent image bearing member 1. Is required, and other characteristics are required.

In addition to the above, a single-layer elastic conductive roller having a resistance distribution in which the resistance increases so as to approach the surface of the single-layer conductive rubber layer, and a seepage preventing layer other than the above resistance layer, An elastic conductive multi-layer roller provided with a resistance adjusting layer, a protective layer, etc., an elastic conductive roller using a foam having a small resistance change, a film-like elastic body having a resistive resin layer formed on a thin metal plate, By using an elastic conductive film formed of a resistive resin or an elastic conductive brush such as a fur brush, the latent image carrier 1 can be charged to a predetermined potential. In particular, when the resistance of the charging member 4 is 10 ⁶ to 10 ⁹ Ω according to the measurement method of FIG. 2, pinholes are formed on the latent image carrier 1 in each environment from high temperature and high humidity to low temperature and low humidity. Even if it occurs, an overcurrent does not flow in the pinhole, and a sufficient charging time can be secured from the time constant of charging, and charging with less uneven charging can be performed.

The roller resistance measuring method of FIG. 2 will be described. The roller 25 is pressed against the conductive plate 26 by a load of 500 gf on both shaft ends, and a 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. . However, the applied voltage during resistance measurement is 10 VDC.

Next, the developing member 11 will be described in more detail. The developing member 11 has elasticity at least on its surface and is pressed against the latent image carrier 1 with a linear pressure of 0.5 to 10 gf / mm. From the viewpoint of maintaining a constant pressure contact state with the latent image bearing member 1, a conductive roller is preferable.

As for the developing bias, for example, when the potential of the non-exposed portion of the latent image carrier 1 is -600V and the potential of the exposed portion is -100V, an intermediate voltage is applied, and when a non-magnetic toner is used, When a magnetic toner is used, a DC developing bias voltage of -250V to -450V is applied, and when an AC component is superimposed, an AC voltage of about 1kHz at about ± 500V is applied to the DC component. Superimpose. Further, it is desirable that the developing member 11 is rotated at a peripheral speed ratio with respect to the latent image carrier 1 to prevent fog on a non-image portion, and the saturated development amount be set to a predetermined value or less. Further, the developing member 11 reduces the adhesion of the external additive of the toner to stably charge the toner, is a triboelectric charging train that charges the toner to a predetermined polarity, and has stable toner transportability. , Does not contaminate the toner, does not contaminate the latent image carrier 1, does not easily stick, does not easily wear, has a smooth surface, and has good contact with the latent image carrier 1 through the toner, etc. The characteristics of are required.

As the developing member, in addition to a single-layer elastic conductive roller, a triboelectric charging layer, a magnetic field generating layer, an exudation preventing layer,
When using an elastic conductive multilayer roller provided with a resistance adjusting layer, a protective layer, or the like, or an elastic conductive brush such as a fur brush,
It is possible to maintain a stable contact state with the latent image carrier 1 and form a high resolution image. When a print history ghost appears due to the toner supply property, an elastic supply roller that supplies and separates the toner is brought into contact with the developing member 11 at a position after development, or the regulating member 15 or the supplying member 14 is used. Can be dealt with by applying a bias voltage that accelerates the supply and charging of the toner or by setting the same potential as that of the developing member 11. The toner supplied to the developing member 11 passes evenly under the regulating member 15 to uniformly form 1 to 2 layers (the volume average particle diameter of the toner is about several μm to 10 μm, so the thickness of the toner layer is about 10 μm). After being triboelectrically charged and thinned, it is conveyed to the developing section, and the electrostatic latent image pattern is visualized with a predetermined developing toner amount according to the developing bias voltage.

The resistance of the developing member 11 is set so that the developing bias voltage is normally applied, the developing delay does not occur, and high resolution printing is realized by the developing electrode effect.
Since the developing nip portion is about 1 mm and the developing time is short, the roller resistance measuring method of FIG. 2 requires a sufficiently small time constant to pass the developing current. In order to realize the printing speed up to about 20 PPM, It is desirable to have a resistance of 10 ⁹ Ω or less. However, even in a high-resistance or insulating toner carrier having a resistance higher than this, the resistance is not limited to this because printing can be continued by adding the charge removing mechanism of the toner carrier.

Next, the transfer member 18 will be described in more detail. As the transfer member 18, an elastic conductive roller in which a conductive foam layer is provided on a metal shaft is used.
/ Mm, the latent image carrier 1 is stably pressed against the recording material 20. Transfer bias is, for example, + 600V
Is applied to +2000 V, the transfer bias is turned off or a cleaning bias of, for example, about −800 V is applied when the transfer member 18 is in direct contact with the latent image carrier 1.
The transfer member 18 is rotated at substantially the same peripheral speed as the latent image carrier 1. Further, it goes without saying that the transfer member 18 does not easily attach toner, does not contaminate the latent image carrier 1, does not easily stick to it, does not easily wear, and has a uniform and flexible surface, and the latent image carrier 1 It is necessary to have characteristics such as good contact with.

In addition to the above, as the transfer member, a single-layer elastic conductive roller using a conductive foam with a skin, and a multilayer elastic conductive layer provided with a seepage preventing layer, a resistance adjusting layer, a protective layer, etc. When a multi-layer roller is used, the recording material 20 can be brought into close contact with the latent image carrier 1 to obtain a high-resolution transferred image without toner scattering or voids. In particular, for the resistance of the transfer member 18, in the resistance value by the measurement method of FIG. 2, 10 ⁵
When it is set to -10 ⁸ Ω, in each environment from high temperature and high humidity to low temperature and low humidity, sufficient transfer time can be secured from the transfer time constant and good transfer can be performed, and the transfer bias should be as low as possible. It is possible to reduce the occurrence of memory due to the electrostatic latent image pattern due to transfer. However, the method of applying the transfer bias is not limited to the method of applying the constant voltage described above, and may be the method of applying the constant current.

Next, the cleaning member 23 will be described in more detail. As the cleaning member 23, a blade made of urethane resin or the like is used for the latent image carrier 1 in an amount of 1 to 40 gf.
The foreign matter is mechanically removed by uniformly pressing the ridgeline with a linear pressure of / mm. In order to reduce the slippage of toner, external additives, etc. from the cleaning member 23, the ridge line accuracy, the contact angle, and the contact pressure of the cleaning member 23 are important, but the ridge line accuracy is about several μm. The contact angle is preferably 10 to 45 degrees with respect to the tangent line at the contact portion of the latent image carrier 1, and the contact pressure is preferably about 2 to 10 gf / mm.

In the image forming method described above, the developing member 9 of the developing device 9 is brought into pressure contact with the latent image carrier 1 by pressure contact development.
An image forming method 1 using non-contact development in which No. 1 is arranged in non-contact with the latent image carrier will be described.

FIG. 8 is a schematic sectional view of an image forming apparatus in a reference example relating to the image forming method of the present invention. Members having substantially the same functions and names as those in FIG. 1 are designated by the same reference numerals and the description thereof is omitted. The developing device 9 conveys and develops the toner 10, and the developing member 11 that conveys the toner 10 has a non-magnetic cylindrical sleeve 81 provided with a multi-pole permanent magnet (magnet roll 82) as a magnetic field generating means. Enclosed, latent image carrier 1
The magnetic toner 10 is held on the developing member 11, and the plate-like regulating member 15 made of non-magnetic or magnetic metal or resin is used. The thin layer is regulated to an appropriate amount, the developing member 11 is rotated, and the thin layer toner 10 is supplied to the developing section. The magnet roll may be rotated or fixed. By using such a developing device, fogging at the time of development can be reduced and contamination and deterioration of the latent image carrier 1 by the developing member 11 can be prevented.

Image formation is performed using the image forming apparatus described above, and the toner used at that time will be described in more detail. Reference Example 1 An image was formed using the image forming apparatus shown in FIG.

When the amount of the external additive of the toner is changed, the fluidity of the toner is greatly changed. FIG. 3 shows the relationship between the transfer bias and the transfer efficiency in the pressure transfer when the amount of the external additive is changed. By increasing the amount of the external additive, the voltage range in which high transfer efficiency is obtained can be widened and the toner scattering at the time of transfer can be reduced. However, by increasing the fluidity of the toner in the transfer process, high transfer efficiency can be ensured even if the transfer bias voltage changes, and variations in resistance of the transfer member can be absorbed. However, a toner having too high fluidity or a toner to which the external additive is easily separated easily slips through the cleaning member, and therefore foreign matter such as the external additive adheres to the contact charging member every time the number of printed sheets is increased, and the toner locally adheres. Some areas have high charging potential and some areas are not charged.

FIG. 4 shows the relationship between the number of printed sheets and the fog amount (on the latent image carrier) due to uneven charging when the amount of external additive is changed. As shown in FIG. 4, when the amount of the external additive exceeds 1.6 wt%, uneven electrification locally occurs even after printing several hundred sheets, and fog, which is expected to be the adhesion of the opposite polarity toner, occurs. The fog toner is not transferred, and the transfer efficiency is deteriorated. This fog was caused by the electrostatic attachment of a minute external additive that slipped through the cleaning member to the contact charging member, and it was found that the amount of the external additive has an upper limit. Further, when the amount of the external additive exceeds 1.6 wt%, electrostatic offset occurs during fixing, which causes ghost-like stains on the image. From the above, the amount of external additive is 0.4
It has been found that by setting the content to be 1.6 wt%, there is a margin in fluctuation of the transfer bias, and it is possible to perform image formation without causing uneven charging even when printing is repeated and electrostatic offset at the time of fixing.

Example 1 An image was formed by using the image forming apparatus shown in FIG. 1 while changing the amount of the external additive of the toner. The environment in which the image is formed is normal temperature and humidity (25 ° C, 50 ° C).
%), Low temperature and low humidity (10 ° C, 15%), high temperature and high humidity (35
C, 65%). FIG. 9 shows the relationship between the external additive amount of toner and the development fog amount. The higher the temperature and humidity, the more the amount of development fog increased, and it was the amount of external additive of 1.2 wt% or less that satisfied the fog allowable value in all the environments. From the above, when the contact charging, the pressure development, the pressure transfer and the pressure cleaning are used, the external additive amount is 0.4 to 1.2 wt%.
It has been found that by adopting the above method, there is a margin in fluctuation of the transfer bias, and it is possible to form an image without causing uneven charging or developing fog even when printing is repeated.

Example 2 An image was formed using the image forming apparatus shown in FIG. The types of external additives are A, B, C,
As D, the relationship between the external additive amount and the development fog amount is shown in FIG. The external additive A is a hydrophobic silica having an average primary particle diameter of about 10 nm, and the external additive B is a hydrophobic silica having the same primary particle average diameter as that of A and having an average primary particle diameter of about 16 nm. Is a hydrophobic silica having an average primary particle size of about 16 nm and having a particularly high hydrophobicity, and the external additive D is a hydrophobic silica having an average primary particle size of about 7 nm and having a low hydrophobicity. is there. By externally adding hydrophobic silica having an average primary particle diameter of 10 nm or more to the resin base particles for toner in the range of 1.2 wt% or less, it was possible to minimize the amount of development fog at the initial stage of printing.

Thus, the amount of external additive is 0.4 to 1.2 w.
When an image was formed by pressure contact development with t% and the average primary particle diameter of the external additive being 10 nm or more, there was a margin in the transfer bias fluctuation, and it was possible to obtain printing without uneven charging and development fog. It was In addition, the adhered state of the external additive to the toner base particles was kept constant even after printing was repeated, and no embedding or the like of the external additive into the toner base particles was observed, and deterioration of the image due to repeated printing was also recognized. I couldn't do it. From the above, by setting the amount of the external additive to be 0.4 to 1.2 wt% and the average primary particle diameter of the external additive to be 10 nm or more, the transfer efficiency is high, and the printing without uneven charging or fog can be performed. It turned out that it can be continued.

(Example 3) Hydrophobic silica (trade name: R97)
2, R974, R202, R812: or more, manufactured by Nippon Aerosil Co., Ltd., product name TS720, TS530: or more CABO
An image was formed by an image forming apparatus shown in FIG. 1 under normal temperature and normal humidity (25 ° C., 50%) using a toner to which 0.4 to 1.2 wt% of T. Co. was externally added. Specification of hydrophobic silica and 3000
Table 1 shows the results of sheet printing. By using a toner in which 0.4 to 1.2 wt% of silica fine powder subjected to hydrophobic treatment is externally added, a clear image with less fog and high transfer efficiency was obtained in the initial stage of printing. However, after printing 3000 sheets,
R972, R974, R202, TS720, TS53
When 0 was used, a clear image with high transfer efficiency with less fog was obtained, but with respect to R812, a decrease in transfer efficiency was observed and a clear image could not be obtained. Three
Observation of the surface of the toner to which R812 was externally added after printing 000 sheets revealed that the external additive was buried. From this, as for the external additives that are typically used, such as hydrophobic silica, if the primary average particle diameter of the external additive is 10 nm or less, fog due to embedding of the external additive increases as the number of printed sheets increases. As a result, the transfer efficiency also decreases, so it was found that the average primary particle diameter of the external additive is preferably 10 nm or more.

[0034]

[Table 1] In the above table ○: Good, △: No problem in actual use, ×: Difficult to use.

(Example 4) Hydrophobic silica (trade name R97
2, R974, R202, R812: or more, manufactured by Nippon Aerosil Co., Ltd., product name TS720, TS530: or more CABO
T-manufactured by externally adding 0.4 to 1.2 wt% of toner, and low temperature and low humidity (10 ° C, 15%), high temperature and high humidity (35 ° C, 65%).
%), And image formation was performed by the image forming apparatus shown in FIG.
Under low temperature and low humidity, all toners satisfied the fogging allowance value, but under high temperature and high humidity, there was some difference depending on the type of hydrophobic silica, but external addition in the range of 0.4 to 1.2 wt% The above toner satisfied the permissible value of fog, but the toner externally added in an amount exceeding 1.2 wt% could not satisfy the permissible value of fog. On the other hand, R20
2. Regarding TS720, the toner externally added in the range of 0.4 to 1.2 wt% all satisfies the permissible value of fog,
The amount of fog was small as compared with other external additives.

Reference Example 2 An image was formed using the image forming apparatus shown in FIG. The resistance of the toner is important in that the toner is triboelectrically charged to a predetermined polarity and the electric charge of the toner does not leak, and in particular, the electric charge is injected into the toner by an electric field of 10 V / μm or more in the pressure developing portion and the pressure transferring portion. It is important that the polarity of the toner does not reverse. FIG. 6 shows the relationship between the volume resistance of toner, the amount of fog in development, and the transfer efficiency. From FIG. 6, it is possible to reduce the amount of development fog by setting the volume resistivity of the toner to 10 ¹⁷ Ωcm or more, and
The transfer efficiency could be as high as 95% or more. Further, the amount of toner remaining unnecessarily on the latent image carrier was reduced, and neither toner nor external additives were found to be attached to the member pressed against the latent image carrier. From the above, it was found that by setting the volume resistivity of the toner to 10 ¹⁷ Ωcm or more, the amount of fog in development can be reduced and the transfer efficiency can be made as high as 95% or more.

However, the volume resistivity of the toner is obtained by compacting the toner into pellets having a thickness of 0.5 mm, placing the electrodes on the top and bottom, and applying a load of 1 Kg / cm ² to a voltage of 250.
The current value at the time of saturation that does not include the charging current when V is applied is calculated and converted into a volume resistance value. The measurement was performed in a dry desiccator which was replaced with a nitrogen atmosphere.

Reference Example 3 Images were formed using the image forming apparatus shown in FIG. The charge control agent added to the toner will be described. By adding the charge control agent, the rise of charging of the toner is improved and the difference in image density between the leading edge and the trailing edge of one sheet of printing is reduced. However, since the metal-containing dye is often used as the charge control agent, the resistance of the toner is lowered.

FIG. 10 shows the relationship between the amount of charge control agent, the rising property of charge and the volume resistivity. Here, as an index showing the rising property of charging, the development amount Ms at the front end and the development amount M at the rear end when developing to obtain a solid black image on A4 paper are performed.
The ratio of e (Me / Ms) was used. That is, the closer Me / Ms is to 1, the better the rise of charging, and conversely Me / Ms.
Indicates that the charge state of the toner on the toner end holding body at the leading end portion and the trailing end portion is different as the value is away from 1, and it can be said that the rise of charging is poor. In order to obtain a state in which the image difference between the front end and the rear end is not discriminated, it is necessary that Me / Ms be 0.8 or more, preferably 0.9 or more. As described above, in order to obtain low development fog and high transfer efficiency, the volume resistivity of the toner needs to be 10 ¹⁷ Ωcm or more, and it is desirable to internally add the charge control agent in the range of 5 wt% or less. . Further, in order to obtain a state in which the difference in image density between the leading edge and the trailing edge during printing of one sheet is not recognized, it is necessary to internally add 1 wt% or more of the charge control agent. From the above, when the amount of the charge control agent was set to 1 to 5 wt%, the image density difference between the leading edge and the trailing edge was not discriminated, and image formation could be performed with low development fog and high transfer efficiency. As described above, by setting the charge control agent amount to 1 to 5 wt%, 10 ¹⁷ Ωc
It has been found that the volume resistivity of the toner of m or more can be secured, the image density can be uniform, the development fog can be reduced, and the image formation with less transfer residue can be performed.

Reference Example 4 Charge control agent (trade name: Bont
ron S-34: manufactured by Orient Chemical Co., Ltd., trade name AIZE
N spiron black, T-95, T-77: or above, manufactured by Hodogaya Chemical, Kayage N-3, T-2:
An image was formed by using the image forming apparatus shown in FIG. 1 with a toner obtained by adding 1 to 5% by weight of resin mother particles (made by Nippon Kayaku Co., Ltd.). With any of the toners, there was no difference in image density between the leading edge and the trailing edge in printing one sheet, fogging was small, and clear images with high transfer efficiency could be obtained. An image was formed by using the image forming apparatus shown in FIG. 1 with the toner obtained by adding 7 wt% of the charge control agent to the resin mother particles. At this time, the volume resistivity of the toner was reduced to around 10 ¹⁵ to 10 ¹⁶ Ωcm, and there was no difference in image density between the leading edge and the trailing edge in printing one sheet with any toner, but fog or transfer failure occurred. Occurred, and a clear image could not be obtained.

Reference Example 5 An image was formed using the image forming apparatus shown in FIG. The colorant added to the toner will be described. Carbon black or the like is often used as a colorant for imparting colorability to the toner, which lowers the resistance of the toner. FIG. 11 shows the relationship among the amount of colorant, volume resistivity of toner, and image density. The amount of the colorant is 0.5 wt% or more with respect to the resin mother particles to obtain an image density of 1.2 or more, and 1 to obtain an image density of 1.4 or more.
It was found that it is necessary to add more than wt%. Also,
In order to set the volume resistivity of the toner to 10 ¹⁷ Ωcm or more, it is desirable to internally add the coloring agent in the range of 10 wt% or less. From the above, the amount of coloring agent is 0.5 to 10 wt.
%, An image density of 1.2 was obtained, and images could be formed with low development fog and high transfer efficiency. Also,
When the colorant amount is set to 1 to 10 wt%, the image density is 1.
4 was obtained, and images could be formed with low development fog and high transfer efficiency. From the above, it was found that the amount of the colorant in the resin mother particles of the toner is preferably 1 to 10 wt% in order to reduce the development fog and improve the transfer efficiency.

Reference Example 6 Carbon black as a colorant (trade name PRINTEX: manufactured by Degussa, MOGUL:
An image was formed using a toner obtained by adding 0.5 wt% of resin mother particles (made by CABOT) to the image forming apparatus shown in FIG. The image density was 1.
At about 2, it was possible to obtain a clear image without fog and with high transfer efficiency. Image formation was also performed by the image forming apparatus shown in FIG. 1 with a toner obtained by adding 1 wt% of PRINTEX and MOGUL to resin mother particles. When any of the toners was used, the image density was 1.4 or more, there was no fog, and a clear image with high transfer efficiency could be obtained. In addition, PRINTEX and MOGUL are added to the resin base particles at 1
An image was similarly formed by the image forming apparatus shown in FIG. 1 with the toner added with 0 wt%. When any of the toners was used, the image density was 1.4 or more, there was no fog, and a clear image with high transfer efficiency could be obtained. However, PRINTE
Image formation was also performed by the image forming apparatus shown in FIG. 1 with a toner in which 12 wt% of X and MOGUL was added to the resin mother particles, and an image density of 1.4 or more was obtained with any of the toners. However, the volume resistivity of the toner is 1
It decreased to around 0 ¹⁶ Ωcm, and fog and transfer failure occurred, and a clear image could not be obtained.

Example 5 An image was formed using the image forming apparatus shown in FIG. The release agent added to the toner will be described. The release agent contained in the toner is important for improving the offset property at the time of fixing the toner, but if the toner is kept under pressure contact in the developing section, the transfer section and the cleaning section, the release agent oozes out. Occurs, and the film adheres to the latent image carrier or the developing member to cause filming. In particular, in the case of polyester type toner, the release agent is often incompatible, and when the external addition amount is lowered, the probability that the toner mother particles directly contact the latent image carrier is high. Filming is likely to occur. However, the same phenomenon is confirmed in the case of other toner resins.

FIG. 7 shows the relationship between the amount of the release agent internally added to the toner resin mother particles and the number of durable prints until filming of the latent image carrier and the developing member occurs. By setting the internal addition amount of the release agent to the resin mother particles to 5 wt% or less,
The filming of the toner on the developing member and the latent image carrier can be prevented, the life of the apparatus can be extended, and the reliability of the apparatus can be improved. Further, by setting the internal addition amount of the release agent to the resin mother particles to 3 wt% or less, the pressure contact developing member, the latent image carrier, and the pressure contact cleaning member can be brought close to the life of the device, and the reliability of the conventional device can be improved. It was not necessary to dispose of the disposable members in order to prevent the deterioration. In addition, the relationship between the amount of the release agent and the void in the transferred image transferred to the recording material was confirmed.

The hollow portion of the transferred image means that the toner and the latent image carrier are in close contact with each other and the transfer to the recording material is hindered. Is a phenomenon of loss. The voids are likely to occur when the pressure applied during transfer is large, that is, the pressure applied to the latent image carrier by the transfer material is larger than necessary, or when thick paper is used as the recording material. Therefore, the cohesive force between the toners is increased by increasing the amount of the release agent added to the toner,
It is possible to overcome the adhesive force between the toner and the latent image carrier and reduce the void. Table 2 shows the relationship between the amount of the release agent and the void. In order to reduce the voids in the transferred image, it is necessary to internally add a release agent to the toner resin mother particles in an amount of 1 wt% or more, preferably 2 wt% or more. From the above, the release agent amount is 1
-5 wt%, preferably 2-5 wt%,
It has been found that it is possible to prevent filming of toner and omission of the transferred image.

[0046]

[Table 2] In the above table, A ... low molecular weight polypropylene, B ... low molecular weight polyethylene, C ... carnauba wax ◯ ... no void, Δ ... some void (no problem in actual use), × ... void.

Reference Example 7 An image was formed using the image forming apparatus shown in FIG. The form factor of the toner will be described. The volume average particle diameter of the toner has been reduced with the increase in resolution of the image forming apparatus. However, in order to obtain the area gradation by the concentrated gray scale equivalent to 300 DPI, the volume average particle diameter of the toner is reduced. The toner of about 12 μm requires a minute toner having a volume average particle diameter of 10 μm or less in order to obtain the area gradation with the concentrated gray scale equivalent to 600 DPI. Even in an image forming apparatus having a contact charging member, a pressure contact developing member, a pressure contact transfer member, and a pressure contact cleaning member, in order to form an image equivalent to 600 DPI, not only high resolution by contact in each process but also toner It is necessary to reduce the volume average particle diameter to 6 to 10 μm. However, when the toner has a smaller particle size, the toner particle size distribution becomes wider, resulting in fogging, toner scattering, and streaks due to slipping due to minute toner, poor charging of minute toner, clogging of coarse toner, and the like. .

Table 3 shows the relationship between the volume average particle size and particle size distribution of the toner and the gradation, fog and filming. As a result of studying the particle size distribution of the toner, toner particles of 5 μm or less are not more than 15% by number, and toner particles of 12.7 μm or more are not more than 5% by number. It has been found that the toner clogging and filming can be prevented, the development fog due to the poorly charged toner can be reduced, the transfer efficiency can be improved, and a high-resolution image can be stably formed. In order to obtain a toner having such a particle size distribution, it is necessary to severely classify the toner and cut the particle size in the upper and lower parts. By using, crushing and classifying, increase in toner cost could be suppressed to a low level.

[0049]

[Table 3] In the above table ○: Good, △: No problem in actual use, ×: Difficult to use.

The composition of the toner used in the present invention is composed mainly of the following (non-magnetic toner), and in the case of a magnetic toner, the composition contains. Further, the method for producing the toner may be a pulverization method or a polymerization method.

Binder resin (resin) Saturated resins such as polystyrene, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid ester copolymer, styrene-butadiene copolymer, etc. Polyester resin, unsaturated polyester resin, epoxy resin, phenol resin, maleic acid resin, coumaronic acid resin, chlorinated paraffin, xylene resin, vinyl chloride resin, polypropylene, polyethylene, and a mixture of two or more thereof as appropriate.

Colorant Carbon black, lamp black, iron black, ultramarine, nigrosine dye, monoazo dye / pigment, disazo dye / pigment,
Trisazo dyes and pigments, oil black, azo oil black, and a mixture of two or more of these as appropriate.

Fluidizing Agent (External Additive) Surface-hydrophobized inorganic oxides such as SiO ₂ , TiO ₂ and Al ₂ O ₃ , inorganic fine particles such as SiC, metallic soaps such as zinc stearate, and these 2 A mixture of at least one species.

Release agent Synthetic waxes such as low molecular weight polyethylene and polypropylene, candelilla wax, carnauba wax,
Plant wax such as rice wax, wood wax, jojoba oil, animal wax such as beeswax, lanolin, whale wax, mineral wax such as montan wax, ozokerite, hardened castor oil, hydroxystearic acid, fat Fats and oils-based waxes such as group amides, phenol fatty acid esters, and the like, in which two or more of these are appropriately mixed.

When the toner of the charge control agent is positively charged, an electron donating substance is used, and a nigrosine dye, a fatty acid metal salt, a quaternary ammonium salt, a benzothiazole derivative, a guanamine derivative, a dibutyltin oxide, a nitrogen-containing compound is used. Etc. can be used. When the toner is negatively charged, an electron-accepting substance is used, and an azo-based metal-containing dye, chlorinated paraffin, chlorinated polyester, alkylsalicylic acid metal complex, dicarboxylic acid metal complex, polycyclic salicylic acid metal salt. Etc. can be used.

Magnetic powder A magnetic material containing at least one element of Fe, Ni, Co, Cr and Mn, such as γ-Fe ₂ O ₃ ,
_{BaO-6Fe 2 O 3, Ni} -Co, Co-Cr, Mn-
Al etc.

[0057]

As described above, according to the present invention, it is possible to provide a small-sized and highly reliable image forming method by means of each process of charging, developing, transferring and cleaning using a pressure contact member. Image density is uniform, development fog can be reduced, and transfer efficiency can be improved.

Further, the external additive having a primary particle average particle diameter of 10 nm or more is added to the toner in an amount of 0.4 to 1.
Since it is externally added within the range of 6 wt%, there is a margin in fluctuation of the transfer bias, and it is possible to form an image without causing uneven charging or developing fog even when printing is repeated. Further, the amount of development fog at the initial stage of printing can be suppressed to a minimum. Further, it is possible to reduce the adhesion of the external additive to the pressure developing member, prevent the generation of the opposite polarity toner, and reduce the fog and the back stain on the transfer.

Further, by setting the amount of the releasing agent to be a predetermined amount or less, the filming of the toner due to the pressure contact portion is prevented, the hollow defect which occurs in the transfer process is suppressed, and a high resolution image is formed. It can be stably formed.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus in an embodiment of an image forming method of the present invention.

FIG. 2 is a diagram showing a roller resistance measuring method.

FIG. 3 is a diagram showing a relationship between a transfer bias and a transfer efficiency in pressure contact transfer when an external additive amount is changed in a reference example of the present invention.

FIG. 4 is a diagram showing the relationship between the number of printed sheets and the amount of fog (on the latent image carrier) due to uneven charging when the amount of external additive is changed in the reference example of the present invention.

FIG. 5 is a diagram showing a relationship between an external additive amount and a development fog amount in an example of the present invention.

FIG. 6 is a diagram showing a relationship between a volume resistance of toner, a development fog amount, and a transfer efficiency in a reference example of the present invention.

FIG. 7 is a diagram showing the relationship between the amount of a release agent internally added to toner resin mother particles and the number of durable prints until filming of a latent image carrier and a developing member occurs in an example of the present invention.

FIG. 8 is a schematic cross-sectional view of an image forming apparatus in a reference example according to the image forming method of the present invention.

FIG. 9 is a graph showing the relationship between the amount of external additive and the amount of fog in the example of the present invention.

FIG. 10 is a diagram showing the relationship between the amount of charge control agent, the rising property of charge, and the volume resistivity in the reference example of the present invention.

FIG. 11 is a diagram showing the relationship between the amount of colorant, image density, and volume resistivity in the reference example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Latent image carrier, 4 ... Charging member, 8 ... Exposure means, 10 ...
Toner, 11 ... Developing member 18 ... Transfer member, 20 ... Recording material, 23 ... Cleaning member

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/10 G03G 21/00 318 F term (reference) 2H005 AA06 AA08 CA13 CA14 CB13 EA05 EA07 2H134 GA01 GB02 HD01 KG01 KG02 KG03 KG04 KG07 KG08 KH01 2H171 FA09 FA11 FA12 FA13 FA14 FA15 FA17 FA24 GA01 JA02 JA04 JA05 JA06 JA08 JA10 QA02 QA08 QB03 QB15 QB32 QB41 QB54 QC03 QC22 TA07 2H200 FA08 GA23 GA34 GA28 HBAB HAB HAB HAB HAB HAB HAB HAB GAB

Claims (3)

[Claims] 1. A pressure-contact charging member that is pressed against a latent image carrier to charge it to a predetermined potential, exposure means for irradiating the latent image carrier with light to form an electrostatic latent image pattern, and the latent image carrier. A pressure contact developing member which is disposed so as to be in pressure contact with the body and applies toner to the electrostatic latent image pattern to make it visible, and a developed toner which is disposed so as to be in pressure contact with the latent image carrier and recorded. 1 for the pressure contact transfer member for transferring to the material and the latent image carrier
A pressure contact cleaning member which is arranged so as to be in pressure contact with a linear pressure of -40 gf / mm, and which removes the toner remaining on the latent image bearing member after transfer. An image forming method comprising: forming an image by the toner on the image forming apparatus. 2. The toner contains 0.4 to 1.2 of an external additive having a primary particle average particle diameter of 10 nm or more with respect to resin mother particles.
The image forming method according to claim 1, wherein the external addition is performed in a range of wt%. 3. The image forming method according to claim 1, wherein the toner has a release agent internally added to the resin mother particles in a range of 1 to 5 wt%.