JP3230011B2 - Image forming method and image forming developer used therein - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method in electrophotography and an image forming developer used therein.

Conventionally, a corona discharger has been known as a charging means in an electrophotographic apparatus or the like. However, since the corona discharge device needs to apply a high voltage, it has problems such as generation of a large amount of ozone.

Therefore, recently, the use of contact charging means without using a corona discharger has been studied. Specifically, a voltage is applied to a conductive roller serving as a charging member, and the roller is brought into contact with a photosensitive member serving as a member to be charged, thereby charging the surface of the photosensitive member to a predetermined potential. If such a contact charging means is used, the voltage can be reduced as compared with a corona discharger, and the amount of ozone generated can be reduced.

[0004] However, when the above-mentioned contact charging means is used, there is a problem that poor charging occurs if sufficient contact with the member to be charged cannot be maintained. Also. In the abutting portion, if the residual developer is present on the surface of the photoconductor, the residual developer adheres to the charging member and the surface of the photoconductor because the charging member has a predetermined contact pressure, and the image is affected. There is also a problem that is.

On the other hand, in recent years, small and inexpensive personal use copying machines and laser printers have emerged. In these small machines, a photoconductor, a developing device, a cleaning device and the like are integrated from a maintenance-free standpoint. It is desirable to use a magnetic one-component developer because a cartridge system is used and the structure of the developing device can be simplified as the developer. In addition, these developers tend to be further finely divided in order to achieve high image quality.

In such a magnetic developer, since the developer itself has a strong polishing effect and strongly rubs the surface of the photoreceptor during image formation, the surface of the photoreceptor is often shaved or damaged. Therefore, there is a problem that the residual developer is fused. This problem becomes remarkable when a contact member such as the charging member is in contact with the surface of the photosensitive member with a predetermined contact pressure.

In the contact charging device according to the present invention, a DC voltage or a DC voltage obtained by superimposing an AC voltage is applied to the charging member and used. At this time, around the contact portion between the charging member and the photosensitive drum, Unusual charging of the residual developer and repetition of flying motion are repeated, which makes it easy for the residual developer to be electrostatically attracted and embedded on the charging member and the surface of the photosensitive drum. Is very different from the case where non-contact charging means is used.

Further, generally, as a method of fixing the developer onto the transfer paper, heating and melting are performed by a heat roller. The amount of heat and pressure at that time are improved in economical efficiency, downsizing of the fixing device, and the like.
In view of simplification of the structure, a smaller one is preferable. In recent years, particularly, space saving and reduction of power consumption of the entire apparatus have been regarded as important, and the tendency has been increasing. Accordingly, a binder resin having a low melting point and a low melt viscosity is desired as a binder resin for a developer.

However, when such a resin is used as a binder, problems tend to occur in the durability, storage stability, offset resistance and the like of the developer. Further, when the contact charging device is used, when the developer is not completely removed in the cleaning step and remains on the photoconductor, there is a very high possibility that the developer is fixed to the photoconductor and the charging member.

[0010] In an image forming method using such a charging device, it is difficult to achieve both of the opposite characteristics desired for a developer.

On the other hand, in an image forming apparatus including a step of electrostatically transferring a transferable toner image formed on the surface of a latent image carrier to a sheet-like transfer material mainly made of paper, a rotary cylindrical, endless Using an image carrier that runs endless, such as a belt, a transfer device to which a bias is applied is pressed against this, and a transfer material is passed between the two, and the toner image on the image carrier is transferred to the transfer material. An apparatus configured as described above, for example, as disclosed in Japanese Patent Application Laid-Open No. Sho 59-46664 has already been proposed.

Such an apparatus adjusts the pressing force of the transfer roller against the image bearing member by adjusting the pressing force of the transfer roller against the image bearing member as compared with a transfer means using corona discharge which has been widely used in the past. The transfer material can be positively supported at the transfer site. For this reason, there is little possibility that a transfer error due to a transfer failure due to a transfer failure due to a transfer material conveyance means or a loop or a curl existing in the transfer material, and the transfer material conveyance path is shortened due to the recent miniaturization of this type of image forming apparatus. It is easy to respond to requests such as reducing the diameter of the image carrier.

On the other hand, in an apparatus for performing transfer by contact, a transfer current is supplied from the contact portion, so that it is necessary to apply a certain pressure to the transfer device. When the contact pressure is applied, pressure is applied to the toner image on the latent image carrier, and aggregation occurs.

Further, when the surface of the latent image carrier is made of a resin, adhesion occurs between the toner aggregate and the latent image carrier, and as a result, the toner is transferred to the surface of the latent image carrier or transferred. The phenomenon of sticking to the surface of the contact member of the device may occur.

If such a phenomenon occurs, the latent image formation of the latent image carrier may be lost, or the transfer may be omitted.
The result is a defective image copy.

In general, the developer is fixed to the transfer material by hot-melt fixing using a heat roller or radiant heating, pressure fixing using a pressure roller, or the like. In view of the properties, the smaller is preferable, and accordingly, the binder resin of the developer tends to contain a so-called soft component having a low melt viscosity, a low melting point, and a small pressure yield point.

However, when such a resin is used as the binder resin, problems tend to occur in terms of the durability of the developer and the storage stability. Furthermore, when a transfer device using a contact member is used, the above-described problems are likely to be remarkable, and it is difficult to achieve both such a transfer device and fixing characteristics of the developer.

[0018]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been made in consideration of the above-mentioned problems. It is an object of the present invention to provide an image forming method having a charging step capable of sufficiently maintaining the contact between a member and a member to be charged and preventing charging failure and charging unevenness, and an image forming developer used for the method.

Further, an object of the present invention is to provide an image forming method based on pressure transfer such as a contact transfer method, in which an image defect due to the developer adhering to the surface of the contact member or the surface of the latent image carrier is prevented. It is an object of the present invention to provide an image forming method for preventing the occurrence and an image forming developer used for the method.

[0020]

According to a first aspect of the present invention, a charging member having a release layer of a nylon resin as a surface layer is applied to an electrostatic latent image carrier at a linear pressure of 5 to 500 g / c.
m, a charging step of applying a negative voltage to the charging member from the outside to charge the electrostatic latent image carrier, and forming an electrostatic latent image on the charged electrostatic latent image carrier by exposure An exposing step, a developing step of developing the electrostatic latent image with a developer having toner to form a toner image on the electrostatic latent image carrier, and a transfer of transferring the toner image on the electrostatic latent image carrier to a transfer material And a cleaning step of removing toner remaining on the latent electrostatic image bearing member, wherein the developer comprises 100 parts by weight of a binder resin,
A negatively-chargeable magnetic one-component developer comprising 150 parts by weight and a negatively chargeable colloidal silica containing 0.1 to 3 parts by weight of a negative charge control agent, wherein the binder resin is at least trivalent. A crosslinked polyester obtained by condensing a monomer having a polyhydric alcohol and / or a trivalent or higher polycarboxylic acid as a main component, wherein the crosslinked polyester has a THF-insoluble content of 70% or less, Tg (glass transition point) is 40 to 70 ° C., and weight average molecular weight is 5
The present invention relates to an image forming method characterized by the number being from 2,000 to 2,000,000, and an image forming developer used for the method.

The second invention of the present application also includes a charging step of charging the electrostatic latent image carrier, an exposing step of forming an electrostatic latent image on the charged electrostatic latent image carrier by exposure, and a developing process having a toner. Developing the electrostatic latent image with the developer to form a toner image on the electrostatic latent image carrier, and applying a linear pressure to the transfer member having a conductive elastic layer of a transfer device on the electrostatic latent image carrier.
g / cm or more, a transfer step of applying a positive voltage to the transfer member to electrostatically transfer the toner image on the latent electrostatic image bearing member to a transfer material, and a latent electrostatic image bearing member An image forming method having a cleaning step of removing toner remaining on the toner, wherein the developer contains 100 parts by weight of a binder resin, 30 to 150 parts by weight of a magnetic substance, and 0.1 to 3 parts by weight of a negative charge control agent. A negatively chargeable magnetic one-component developer having a magnetic toner contained therein and hydrophobic colloidal silica, wherein the binder resin is at least a trihydric or higher polyhydric alcohol and / or
A crosslinked polyester obtained by condensing a monomer having a polyvalent carboxylic acid having a valency of at least 0.1 as a main component, wherein the crosslinked polyester has a THF insoluble content of 70% or less and a Tg
The present invention relates to an image forming method having a (glass transition point) of from 40 to 70 ° C. and a weight average molecular weight of from 5,000 to 2,000,000, and an image forming developer used therefor.

Next, the toner used in the present invention will be described.

The binder resin for toner used in the present invention improves the strength of the developer due to its cross-linking structure, and prevents sticking to the latent image carrier during contact charging. In order to achieve the best effect, the crosslinking component, Tg and weight average molecular weight of the resin are in the following ranges.

That is, the binder resin is a crosslinked polyester having a THF insoluble content of 70% or less, a Tg (glass transition point) of 40 to 70 ° C., and a weight average molecular weight of 5000 to 2,000,000.

When the Tg is less than 40 ° C., sticking to the device is likely to occur during contact charging, and the same tendency is exhibited when the weight average molecular weight is less than 5000. Also, T
g exceeds 70 ° C. or the weight average molecular weight is 200
If the number exceeds 10,000, the surface of the latent image carrier is easily damaged. When the THF-insoluble content exceeds 70%, the tendency is more remarkable. In the case of a wound, there is a possibility that fixation may further occur from the site.

Next, a method for measuring Tg, THF insoluble matter and molecular weight in the present invention will be described.

The Tg was measured by using a DS manufactured by Perkin Elmer Co.
Using C-7, heating rate 10 ° C / min Sample 10mg
And measured according to ASTM (D3418-82). As shown in FIG. 5, in the DSC curve at the time of the second temperature rise, the middle line between the baseline (1) and the baseline (2) after the endothermic peak,
The rising curve is defined as Tg.

The THF-insoluble content in the present invention indicates the weight ratio of the polymer component insoluble in the THF solvent in the resin composition in the toner, and indicates the degree of crosslinking of the resin composition containing the crosslinking component. As a guideline, even if the THF-insoluble content is 0%, it does not necessarily mean that crosslinking has not occurred. T
The HF insoluble content is defined by a value measured as follows.

That is, when the developer is a non-magnetic toner, the content of the pigment and the like are measured in advance by a known method when the developer is a magnetic toner. Next, a fixed amount of 0.5 to 1.0 g of the developer is weighed (W
₁ g), put in a cylindrical filter paper (No. 86R, manufactured by Toyo Roshi Kaisha), run through a Soxhlet extractor, and use chloroform 1 as a solvent.
Extraction is performed for 6 hours using 00 to 200 ml, and the soluble components extracted by the solvent are evaporated, and then dried in vacuum at 100 ° C. for several hours, and the amount of the THF soluble resin component is weighed (W ₂ g). Then, of the pigment and the magnetic substance contained in the fixed amount of the developer, the weight of the component soluble in THF is determined by W ₃
g, the weight of the component insoluble in THF is W ₄ g, and the THF-insoluble content in the resin composition is calculated according to the following equation.

THF-insoluble content = (W ₁ −W ₂ −W ₄ ) / (W ₁ −W ₃ −W ₄ ) × 100 (%)

The solvent-soluble component obtained by the above-mentioned operation is evaporated to dryness, dissolved in THF (tetrahydrofuran), passed through a sample processing filter, and used as a GPC sample.

In the present invention, the molecular weight of a chromatograph by GPC (gel permeation chromatography) is measured under the following conditions.

That is, the column was stabilized in a heat chamber at 40 ° C., and THF (tetrahydrofuran) as a solvent was flowed through the column at this temperature at a flow rate of 1 ml per minute, and the sample concentration was 0.05 to 0.1% by weight. % Of the THF sample solution of the resin adjusted to 50% to 200 μl is measured. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value of a calibration curve prepared from several kinds of monodisperse polystyrene standard samples and the count number. As a standard polystyrene sample for preparing a calibration curve, for example, Pressure Chemical Co. (PressureC)
chemicalCo. ) Or Toyo Soda Kogyo Co., Ltd. having a molecular weight of 6 × 10 ² , 2.1 × 10 ³ , 4 × 10 ³ ,
1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1.1 × 10 ⁵ ,
3.9 × 10 ⁵ , 8.6 × 10 ⁵ , 2 × 10 ⁶ , 4.4
It is suitable to use 8 × 10 ⁶ and to use at least about 10 standard polystyrene samples. An RI (refractive index) detector is used as the detector.

In addition, as a column, 10 ³ -4 × 10 ⁶
In order to accurately measure the molecular weight region of the polystyrene gel column, a plurality of commercially available polystyrene gel columns may be used in combination. For example, μ-styra gel (st
(yragel) 500, 10 ³ , 10 ⁴ , 10 ⁵ , and Showdex (Shodex)
x) KF-80M, KF-802, 803, 804,
805 combination or TSKgel manufactured by Toyo Soda
G1000H, G2000H, G2500H, G300
0H, G4000H, G5000H, G6000H, G
A combination of 7000H and GMH is preferred.

The polyester resin according to the present invention is obtained by condensation of an alcohol and a carboxylic acid.

Examples of the alcohol used include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol and the like. Diols; dihydric alcohols such as 1,4-bis (hydroxymethylcyclohexane, and etherified bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, and polyoxypropylene bisphenol A); No.
Carboxylic acids include maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid, and these acids And divalent organic acids such as a dimer of a lower alkyl ester and oleic acid.

Further, the polyester resin according to the present invention contains a trihydric or higher polyhydric alcohol and / or a trivalent or higher polyhydric carboxylic acid as essential monomers.

Examples of trihydric or higher polyhydric alcohols include sorbitol, 1,2,3,6-hexanetetrol,
1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose,
1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,
3,5-trihydroxymethylbenzene and the like. Examples of the trivalent or higher polycarboxylic acid include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, and 2,5,7-naphthalene. Tricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,2
4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2
-Methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, empol trimer acid, and acid anhydrides thereof.

In the present invention, in addition to the above-mentioned binder resin component, the following compounds may be contained in a proportion smaller than the content of the binder resin component as long as the effects of the present invention are not adversely affected. .

For example, silicone resin, polyester,
Polyurethane, polyamide, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin such as low molecular weight polyethylene or low molecular weight polypropylene, aromatic petroleum resin, chlorinated paraffin, For example, paraffin wax.

As the colorant contained in the toner according to the present invention, generally known dyes and pigments can be used.
Examples of such dyes and pigments include, for example, carbon black, nigrosine dye, lamp black, Sudan black S
M, First Yellow G, Benzidine Yellow, Pigment Yellow, India First Orange, Irgazine Red, Paranitroaniline Red, Toluidine Red, Carmin FB, Permanent Bordeaux F
RR, Pigment Orange R, Risor Red 2
G, rake red C, rhodamine FB, rhodamine B
Lake, methyl violet B lake, phthalocyanine blue, pigment blue, brilliant green B, phthalocyanine green, oil yellow GG, Zapon First Yellow CGG, Kayaset Y963,
Kayaset YG, Sumiplast Yellow GG, Zapon Fast Orange RR, Oil Scarlet, Sumiplast Orange G, Orazol Brown B, Zapon First Scarlet CG, Aizen Spiron Red BEH, Oil Pink OP, etc. can be applied. These coloring agents are generally used to obtain a capsule toner for a two-component developer, and are used in an amount of 5 to 20 with respect to the core material binder.
% Is preferably added.

The effect of the present invention is remarkable also in a magnetic toner having a magnetic material. As the magnetic material combined with the binder resin of the present invention, ferrite, iron including magnetite, cobalt, a metal composed of a ferromagnetic element such as nickel, or an alloy or compound containing the same, or a strong magnetic element Although not included, alloys that become ferromagnetic by appropriate heat treatment or the like, for example, alloys of the type called Heusler alloys containing manganese and copper, such as manganese-copper-aluminum or manganese-copper-tin. Or chromium dioxide and others. The content ratio of the fine powder of the magnetic substance can be 30 to 150 parts by weight, preferably 40 to 100 parts by weight, based on 100 parts by weight of the binder resin. Also,
The magnetic fine particles can also be used as a black or brown pigment.

As the charge control agent contained in the toner according to the present invention, a conventionally known charge control agent is selected. As specific examples of the positive charge control agent, generally, nigrosine, carbon number 2
Azine dyes containing up to 16 alkyl groups (Japanese Patent Publication No.
No. 1627), basic dyes (for example, CI Basic Yellow 2 (CI.41000), CI Basic Yellow 3, CI Basic Red 1 (C.I.
I. 45160), C.I. I. Basic Red 9 (C.I.
I. 42500), C.I. I. Basic Violet 1
(CI. 42535), C.I. I. Basic Violet 3 (C.I. 42555), C.I. I. Basic Violet 10 (C.I. 45170), C.I. I. Basic Violet 14 (CI. 42510), C.I.
I. Basic Blue 1 (CI. 42025), C.I.
I. Basic Blue 3 (CI. 50005), C.I.
I. Basic Blue 5 (C.I. 42140), C.I.
I. Basic Blue 7 (CI. 42595), C.I.
I. Basic Blue 9 (CI. 52015), C.I.
I. Basic Blue 24 (CI.52030),
C. I. Basic Blue 25 (CI.5202)
5), C.I. I. Basic Blue 26 (CI.440)
25), C.I. I. Basic Green 1 (CI.42
040), C.I. I. Basic Green 4 (CI.4
Lake pigments of these basic dyes (for example, phosphotungstic acid, phosphomolybdic acid, phosphomolybdic molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide, ferrocyanide, etc.) , C.I. I. Solvent Black 3 (CI.
26150), Hansa Yellow G (CI. 1168)
0), C.I. I. Maudrant Black 11, C.I. I. Pigment Black 1 etc.

Alternatively, polyamide resins such as quaternary ammonium salts such as benzolmethyl-hexadecyl ammonium chloride and decyl-trimethyl ammonium chloride, vinyl polymers containing amino groups, and condensation polymers containing amino groups, etc. Preferred are nigrosine, quaternary ammonium salts, triphenylmethane-based nitrogen-containing compounds, and polyamides.

Specific examples of the negative charge control agent include JP-B Nos. 41-20153, 42-27596 and 4
Metal complexes of monoazo dyes described in JP-A-4-6397 and JP-A-45-26478;
Nitroamine acids and salts thereof described in JP-A-33338; I. Dyes and pigments such as 14645;
No. 42755, No. 58-41508, No. 5
No. 8-7384, JP-B-59-7385 and the like, Z of salicylic acid, naphthoic acid and dicarboxylic acid.
Examples include metal complexes such as n, Al, Co, Cr, and Fe; sulfonated copper phthalocyanine pigments; styrene groups having nitro groups and halogens; and chlorinated paraffins. In particular, from the viewpoint of dispersibility, a metal complex salt of a monoazo dye, and a metal complex of salicylic acid, alkylsalicylic acid, naphthoic acid, and dicarboxylic acid are preferable. The addition amount of these charge control agents minimizes adverse effects such as a reduction in developing power and a decrease in environmental stability due to contamination of the developing sleeve surface by the charge control agents while maintaining good triboelectricity as described above. Therefore, the addition amount is preferably 0.1 to 3 parts by weight based on 100 parts by weight of the binder resin.

An ethylene-based olefin polymer may be used together with a binder resin as a fixing aid in the toner of the present invention.

Here, those applied as ethylene-based olefin homopolymer or ethylene-based olefin copolymer include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, and ethylene-ethyl acrylate copolymer. There is an ionomer having a polyethylene skeleton, or the like, and the above copolymer preferably contains 50 mol% or more (more preferably, 60 mol% or more) of an olefin monomer.

The toner of the present invention can provide good results when additives are mixed as necessary. As the additive, for example, a lubricant such as Teflon, zinc stearate, and polyvinylidene fluoride, among which polyvinylidene fluoride is preferable. Alternatively, abrasives such as cerium oxide, silicon carbide, and strontium titanate, among which strontium titanate is preferable. Alternatively, a fluidity-imparting agent such as colloidal silica and aluminum oxide, particularly hydrophobic colloidal silica is preferable. An anti-caking agent, a conductivity-imparting agent such as carbon black, zinc oxide, antimony oxide, and tin oxide; a fixing aid such as low-molecular-weight polyethylene, low-molecular-weight polypropylene, and various waxes; Further, a small amount of white fine particles and black fine particles of opposite polarity can be used as a developing property improver.

In the production of the toner of the present invention, the constituent materials are kneaded well by a heat kneader such as a hot roll kneader or an extruder and then obtained by mechanical pulverization or classification, or the material is added to a binder resin solution. Is obtained by dispersing and then spray-drying, or a polymerization method in which a predetermined material is mixed with a monomer to constitute a binder resin to form an emulsified suspension and then polymerized to obtain a toner. Each method can be applied.

The developer according to the present invention has the above-described structure, and therefore, even when the developer is not completely removed in the cleaning step and remains on the photoreceptor, it is extremely adhered to the surface of the charging member or the surface of the photoreceptor. Less likely.

The reason why the developer of the present invention exhibits the above effects is considered as follows.

The developer using a polyester resin as a binder has a low melting point even when the melting point is lowered in consideration of the fixability.
g can be kept relatively high. Furthermore, by introducing a crosslinked structure, a developer having a strength that can withstand a contact charging device can be obtained.

From the above, the developer according to the present invention is:
The matching with the charging step according to the present invention is very good, and it is possible to provide an image forming method that fully demonstrates the ability of the charging step according to the present invention and always performs good image formation.

Next, the contact charging step of the present invention applicable to the image forming method of the first invention of the present application will be specifically described.

FIG. 1 is a schematic configuration diagram of a contact charging device showing an example of the first invention of the present application. Reference numeral 1 denotes a photosensitive drum as an object to be charged, which is formed by forming an organic photoconductor (OPC) 1b as a photosensitive layer on an outer peripheral surface of a drum base 1a made of aluminum. Rotate.
In this embodiment, the photosensitive drum 1 has an outer diameter of 30 mmφ. Reference numeral 2 denotes a charging roller which is a charging member brought into contact with the photosensitive drum 1 at a predetermined pressure.
A conductive rubber layer 2b was provided on a, and a surface layer 2c as a release coating was further provided on the peripheral surface. The surface layer in this example of the apparatus is a release film, and it is preferable to provide the release film in view of matching with the developer and the image forming method according to the present invention.

However, if the resistance is too high, the photosensitive drum 1 is not charged, and if the resistance is too low, a large voltage is applied to the photosensitive drum 1 so that damage to the drum may occur.
Since pinholes occur, a suitable resistance, that is, a volume resistivity of 10 ⁹ to 10 ¹⁴ Ωm is good, and the thickness of the release film at this time is preferably within 3.0 μm. Further, the lower limit of the thickness of the film is considered to be about 5 μm if the film is free of peeling and burrs.

In this embodiment, the outer diameter of the charging roller 2 is 12
mmφ, conductive rubber layer 2b is EPDM, surface layer 2c
A nylon resin having a thickness of 10 μm was used. The hardness of the charging roller 2 was 54.5 ° (ASKER-C).
E denotes a power supply unit that applies a voltage to the charging roller 2 and supplies a predetermined voltage to the metal core 2 a of the charging roller 2. In FIG. 1, E indicates a DC voltage, but may be obtained by superimposing an AC voltage on a DC voltage.

FIG. 2 is a schematic structural view of a contact charging member showing another example of the apparatus. The same members as those of the apparatus of FIG. 1 are denoted by the same reference numerals, and the description thereof will not be repeated.

The contact charging member 2 'of this embodiment is a blade-like member which is brought into contact with the photosensitive drum 1 in a forward direction at a predetermined pressure, and the blade 2' is a metal supporting member 2 'to which a voltage is supplied. The conductive rubber 2'b is supported by a, and a surface layer 2'c serving as a releasable film is provided at a contact portion with the photosensitive drum 1. Thickness 1 as surface layer 2'c
0 μm nylon was used. According to this apparatus example, the same operation and effect as those of the above-described apparatus example can be obtained without any trouble such as adhesion between the blade and the photosensitive drum.

The mechanical or electric pressure applied between the charging member and the photosensitive member is an element according to the gist of the present invention, and the contact pressure of the charging member with the photosensitive member is 5 to 500 g.
/ Cm, the DC voltage applied to the charging member has an absolute value of 20
When an AC voltage is applied to 0 to 900 V, the peak-peak voltage is 500 to 5000 V, and the frequency is 50 to 3,000.
Hz.

In the above-described example of the apparatus, a roller-shaped or blade-shaped charging member is used. However, the present invention is not limited to this, and the present invention can be applied to other shapes.

In the present example, the charging member is formed of a conductive rubber layer and a releasable coating. However, the present invention is not limited to this. For preventing leakage to the photoreceptor between the conductive rubber layer and the surface of the releasable coating. For this purpose, it is preferable to form a high-resistance layer, for example, a hydrin rubber layer with small environmental fluctuation.

Further, instead of nylon resin, PVDF (polyvinylidene fluoride), PVDC
(Polyvinylidene chloride) may be used. As the photoconductor, amorphous silicon, selenium, ZnO or the like can be used. In particular, when amorphous silicon is used for the photoconductor, compared to the case where other materials are used, even if the softening agent of the conductive rubber layer adheres to the photoconductor even to a small extent, the image flow becomes severe, so The effect of the insulating coating is great.

In the cleaning process according to the present invention, the photosensitive drum after the transfer of the toner image is generally wiped off by a cleaning member such as a blade or a roller of a cleaner to remove the transfer residual toner and other contaminants. It is cleaned and repeatedly subjected to image formation.

Further, such a cleaning step can be performed simultaneously in a charging step, a developing step, or a transfer step related to the electrophotographic method.

The present invention is particularly effective for an image forming apparatus in which the surface of a latent image carrier is an organic compound. When the organic compound forms a surface layer, it has good adhesion to the binder resin contained in the toner, and especially when using the same material, a chemical bond occurs at the contact point and transferability is reduced. To do that.

The surface material of the latent image carrier used in the present invention includes, but is not limited to, silicone resin, vinylidene chloride, ethylene-vinyl chloride, styrene-acrylonitrile, styrene-methyl methacrylate, styrene, polyethylene terephthalate, polycarbonate and the like. However, other monomers or copolymerization or blending between the exemplified resins can also be used.

The present invention is particularly effective for an image forming apparatus in which the diameter of the latent image carrier is 50 mm or less. This is because, in the case of a small-diameter drum, even if the linear pressure is the same, the curvature is large, so that the pressure tends to concentrate at the contact portion.

It is considered that the same phenomenon occurs in the belt photosensitive member, and the present invention is also effective for an image forming apparatus having a radius of curvature of 25 mm or less at the transfer portion.

Next, an image forming method according to the second aspect of the present invention will be described.

The contact pressure used in the present invention is set to a linear pressure of 3 g / cm or more.

The linear pressure is calculated by the following equation.

Linear pressure (g / cm) = total pressure (g) applied to the transfer member / length in contact (cm)

If the contact pressure is less than 3 g / cm, transfer failure of the transfer member and insufficient transfer due to insufficient transfer current undesirably occur.

The transfer device used in the present invention includes a transfer roller as shown in FIG. 3 or a transfer belt as shown in FIG.

FIG. 3 is a schematic side view of a main part of a typical image forming apparatus of this type. The illustrated apparatus has a cylindrical image carrier that extends in a direction perpendicular to the paper and rotates in the direction of arrow A. A body (hereinafter, referred to as a photoconductor) 31 and a conductive transfer roller 32 in contact with the body 31 are provided.

A primary charger for uniformly charging the surface of the photoreceptor 31, a laser beam image-modulated on the charged surface, and a light image such as a reflected light from an original are projected on the charged surface. And an exposure section for attenuating the potential of the portion to form an electrostatic latent image, a developing device, a cleaner for removing residual toner remaining on the surface of the photoreceptor even after transfer, and other members required for image formation. Needless to say, they are all omitted.

The transfer roller 32 comprises a core bar 32a and a conductive elastic layer 32b. The conductive elastic layer 32b has a volume resistance of about 10 ⁶ to 10 ¹⁰ Ωcm such as urethane or EPDM in which a conductive material such as carbon is dispersed. Made of elastic material. A bias is applied to the metal core 32a by a constant voltage power supply 38.

FIG. 3 shows the present invention applied to a transfer belt. The transfer belt 39 is supported and driven by the conductive roller 40. The pressurization of the transfer device is usually performed by pressurizing the end bearing of the core of the core 32a or 40.

The present invention is particularly effective for an image forming apparatus in which the surface of a latent image carrier is an organic compound. When the organic compound forms a surface layer, it has good adhesion to the binder resin contained in the toner, and especially when using the same material, a chemical bond occurs at the contact point and transferability is reduced. To do that.

The surface material of the latent image carrier used in the present invention includes, but is not limited to, silicone resin, vinylidene chloride, ethylene-vinyl chloride, styrene-acrylonitrile, styrene-methyl methacrylate, styrene, polyethylene terephthalate, polycarbonate and the like. However, other monomers or copolymerization or blending between the exemplified resins can also be used.

In the present invention, the diameter of the latent image carrier 31 is 50 mm.
This is particularly effective for the following image forming apparatuses. This is because, in the case of a small-diameter drum, even if the linear pressure is the same, the curvature is large, so that the pressure tends to concentrate at the contact portion.

It is considered that the same phenomenon occurs in the belt photoreceptor, and the present invention is also effective for an image forming apparatus having a radius of curvature of 25 mm or less at the transfer portion.

[0084]

The present invention will be described in detail with reference to the following examples.

<Example 1> Propylene oxide derivative of bisphenol A 40 mol parts Ethylene glycol 90 mol parts Pentaerythritol 5 mol parts Isophthalic acid 40 mol parts Terephthalic acid 60 mol parts A crosslinked polyester resin was synthesized by adding 04% of zinc acetate and 0.05% of dibutyltin oxide. The resin had a THF-insoluble content of 5%, a weight average molecular weight of 18,500 and a Tg of 61 ° C.

100 parts by weight of this resin, 100 parts by weight of magnetic powder having an average particle diameter of 0.3 μm 0.6 parts by weight of a negatively chargeable monoazo dye 4 parts by weight of low molecular weight polypropylene After mixing the above materials, kneading was carried out according to a conventional method. , Crush, classify,
Magnetic powder-containing resin particles having an average particle size of 6.6 μm were obtained. 0.9% of negatively chargeable colloidal silica was mixed with 100 parts by weight of the magnetic powder-containing resin particles to obtain a developer.

Next, this magnetic developer was applied to the contact charging device shown in FIG. 2 by applying a contact pressure of 70 g / cm to the photosensitive member, applying a current of -400 V DC to the charging member, and 1200 V AC.
Using an image forming apparatus (LBP-SX modified machine manufactured by Canon Inc.) with a pp of 150 Hz and a printing speed of 4 sheets (A4) / min. (25 ° C, 60% R
H), high temperature and high humidity (30 ° C., 90% RH) and low temperature and low humidity (15 ° C., 10% RH), the printout image was evaluated, and at the same time, the state of the charging member and the surface of the photoreceptor were observed.

As a result, no residual developer was fixed on the charging member and the surface of the photosensitive member in any of the environments.
The obtained image was excellent in reproducibility of fine lines.

<Example 2> In the same manner as in Example 1 except that the contact charging member was changed to a blade type using the developer of Example 1, 5000 in each environment.
A print test was performed on one sheet.

As a result, no residual developer was fixed on the charging member and the photosensitive member in each environment, and the obtained image was clear.

<Example 3> Propylene oxide derivative of bisphenol A 60 mol parts Ethylene glycol 90 mol parts Trimellitic anhydride 10 mol parts Terephthalic acid 50 mol parts Isophthalic acid 50 mol parts A crosslinked polyester resin was synthesized by adding 0.05% of antimony trioxide. This resin had a THF-insoluble content of substantially 0%, a weight average molecular weight of 128,000 and a Tg of 58 ° C.

A developer having a weight average particle size of 6.5 μm was produced in the same manner as in Example 1 except that this resin was used.

Using this developer, a printing test of 5,000 sheets was performed under the same environment as in Example 1.

As a result, no residual developer was fixed on the charging member and the photosensitive member in each environment, and the obtained image was clear.

<Comparative Example 1> Propylene oxide derivative of bisphenol A 50 mol parts Ethylene glycol 80 mol parts Terephthalic acid 50 mol parts Isophthalic acid 50 mol parts Antimony was added to synthesize a polyester resin having no crosslinking component. The THF insoluble content is 0%, and the weight average molecular weight is 55.
00 and Tg were 38 ° C.

A developer having a weight average particle size of 6.5 μm was produced in the same manner as in Example 1 except that this resin was used.

Using this developer, a print test was performed in each environment in the same manner as in Example 1.

As a result, under the condition of high temperature and high humidity, sticking matter starts to be generated on the photosensitive member surface and the charging member surface from around 1500 sheets.
Correspondingly, white spots occurred on the image.

<Comparative Example 2> A print test was performed in each environment using the same developer and method as in Comparative Example 1 except that the contact charging member was a blade type.

As a result, under high temperature and high humidity, the adhered matter starts to be formed on the photosensitive member surface and the charging member surface from around 1500 sheets.
Correspondingly, white spots occurred on the image.

<Example 4> Propylene oxide derivative of bisphenol A 50 mol part Ethylene glycol 60 mol part Pentaerythritol 10 mol part Terephthalic acid 100 mol part 0.04% zinc acetate based on terephthalic acid And 0.05% of dibutyltin oxide were added to synthesize a crosslinked polyester resin. This resin had a THF-insoluble content of 8%, a weight average molecular weight of 1,530,000 and a Tg of 62 ° C.

100 parts by weight of this resin, 100 parts by weight of magnetic powder having an average particle diameter of 0.3 μm 0.6 parts by weight of a negatively chargeable monoazo dye 4 parts by weight of low molecular weight polypropylene After mixing the above materials, the mixture was heated to 150 ° C. The mixture was kneaded with a heated two-roll mill for 20 minutes. After cooling, the kneaded material was coarsely pulverized, pulverized using a fine pulverizer using a jet stream, and further classified using an air classifier to obtain a black fine powder having a weight average particle size of 6.6 μm. Further, 0.9 part by weight of hydrophobic colloidal silica fine powder was dry-mixed with 100 parts by weight of the obtained black fine powder (magnetic toner) to obtain a silica externally added toner (developer).

The obtained developer was charged into a commercially available copying machine FC-5 (manufactured by Canon Inc .; OPC laminated negatively charged photoreceptor, drum diameter φ30) modified so as to be capable of reversal development. A transfer device such as No. 3 was incorporated. The conditions of the transfer roller were a surface rubber hardness of 27 ° of the transfer roller, a transfer current of 1 μA, and a contact pressure of 30 (g / cm).

An electrostatic latent image is formed by setting the primary charge to -600 V, a gap (300 μm) is set without contact between the photosensitive drum and the developer layer on the developing drum (magnet inclusion), and an AC bias (f = 1, When a print test by reversal development was performed while applying 800 Hz, V _PP = 1,200 V) and a DC bias (V _DC = -390 V) to the developing drum, the transfer roller was obtained even when 5,000 images were formed. Neither fixation nor flaw of the toner was observed on the surface or the OPC photoreceptor surface, and a good image continued.

Example 5 A print test was performed on 5,000 sheets under the same method and environment as in Example 4 except that the transfer device was changed to the structure shown in FIG.
As a result, in each environment, the toner was not fixed, and the obtained image was clear.

<Example 6> Propylene oxide derivative of bisphenol A 60 mol parts Ethylene glycol 80 mol parts Trimellitic anhydride 10 mol parts Terephthalic acid 50 mol parts Isophthalic acid 40 mol parts A crosslinked polyester resin was synthesized by adding 0.05% of antimony trioxide. This resin had a THF-insoluble content of substantially 0%, a weight average molecular weight of 155,000 and a Tg of 58 ° C.

A developer having a weight average particle size of 6.7 μm was produced in the same manner as in Example 4 except that this resin was used.

Using this developer, a print test of 5,000 sheets was performed under the same environment as in Example 4.

As a result, no residual developer was fixed on the transfer roller and the photosensitive member in each environment, and the obtained image was clear.

<Comparative Example 3> Propylene oxide derivative of bisphenol A 90 mol parts Ethylene glycol 20 mol parts Terephthalic acid 50 mol parts Isophthalic acid 50 mol parts Antimony was added to synthesize a polyester resin having no crosslinking component. This resin had a THF-insoluble content of 0%, a weight average molecular weight of 4,900 and a Tg of 36 ° C.

A toner having a weight average particle size of 6.5 μm was produced in the same manner as in Example 4 except that this resin was used.

Using this toner, a print test was performed in each environment in the same manner as in Example 4.

As a result, at about 1500 sheets under high temperature and high humidity, sticking matters began to be formed on the surface of the photosensitive member and the transfer roller.
Further printing resulted in white spots on the image corresponding to the fixed portions.

<Comparative Example 4> A print test was performed in each environment using the same developer and method as in Comparative Example 3 except that the transfer device was changed to the structure shown in FIG.

As a result, under high temperature and high humidity, fixed matters started to be formed on the photosensitive member surface and the transfer belt surface from around 1500 sheets, and as a result of continuous printing, white spots were also formed on the image corresponding to the fixed portions. It has happened.

[0116]

As described above, according to the present invention,
There is no environmental fluctuation, and it is possible to provide a clear image over a long period with excellent fine line reproducibility.

[Brief description of the drawings]

FIG. 1 is a schematic view of a charging roller according to the first invention of the present application.

FIG. 2 is a schematic view of a blade according to the first invention of the present application.

FIG. 3 is a schematic side view of a main part of an image forming apparatus according to a second invention of the present application.

FIG. 4 is a schematic side view of a main part of an image forming apparatus according to a second invention of the present application.

FIG. 5 is a diagram showing a method for measuring a glass transition point.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum 2, 2 ′ charging member 31 latent image carrier 32 contact transfer roller 34 transfer material transfer guide 37 transfer material transfer guide 38 transfer bias power supply 39 contact transfer belt 40 conductive roller

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Kiyoko Tsuchiya 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-3-188468 (JP, A) JP-A-62 -21170 (JP, A) JP-A-60-8850 (JP, A) JP-A-61-153663 (JP, A) JP-A-63-121059 (JP, A) JP-A-62-226161 (JP, A) JP-A-1-105957 (JP, A) JP-A-1-307767 (JP, A) JP-A-63-193155 (JP, A) JP-A-3-293364 (JP, A) JP-A-4- 40469 (JP, A) JP-A-59-220749 (JP, A) JP-A-3-50562 (JP, A) JP-A-3-59568 (JP, A) JP-A-3-121462 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (8)

(57) [Claims] 1. A release layer of a nylon resin is used as a surface layer.
The charging member having a linear pressure of 5 to 5
A charging step of applying a negative voltage to the charging member from outside to charge the latent electrostatic image bearing member;
An exposure step of forming an electrostatic latent image on the charged electrostatic latent image carrier by exposure, and developing the electrostatic latent image with a developer having toner to form a toner image on the electrostatic latent image carrier An image forming method comprising: a step of transferring a toner image on the latent electrostatic image bearing member to a transfer material; and a cleaning step of removing toner remaining on the latent electrostatic image bearing member. , 100 parts by weight of binder resin , magnetic material 30 to 15
0 parts by weight and 0.1 to 3 parts by weight of the negative charge control agent
Negative for chromatic and magnetic toner, a negatively chargeable colloidal silica
Chargeable magnetic one-component developer der is, obtained by condensation as a main component monomer binder resin has at least trihydric or higher polyhydric alcohol and / or trivalent or more carboxylic acid The crosslinked polyester has a THF insoluble content of 70% or less, a Tg (glass transition point) of 40 to 70 ° C, and a weight average molecular weight of 50%.
An image forming method, wherein the number is from 2000 to 2,000,000. 2. The image forming method according to claim 1, wherein the crosslinked polyester has a THF insoluble content of 5% or less. A charging step of charging the electrostatic latent image carrier;
An exposure step of forming an electrostatic latent image on the charged electrostatic latent image carrier by exposure, and developing the electrostatic latent image with a developer having toner to form a toner image on the electrostatic latent image carrier Process, the conductive charge of the transfer device to the latent electrostatic image bearing member
A transfer member having a conductive layer is contacted with a linear pressure of 3 g / cm or more, and a positive voltage is applied to the transfer member to electrostatically transfer the toner image on the latent electrostatic image bearing member to a transfer material. Process,
And a cleaning step of removing toner remaining on the electrostatic latent image carrier, wherein the developer comprises 100 parts by weight of a binder resin , and 30 to 15 magnetic substances.
0 parts by weight and 0.1 to 3 parts by weight of the negative charge control agent
Negative band to be closed with magnetic toner and a hydrophobic colloidal silica
Ri conductive magnetic one-component developer der, obtained by condensation as a main component monomer binder resin has at least trihydric or higher polyhydric alcohol and / or trivalent or more carboxylic acid A crosslinked polyester, wherein the crosslinked polyester is
The THF insoluble content is 70% or less, the Tg (glass transition point) is 40 to 70 ° C., and the weight average molecular weight is 500
An image forming method, wherein the number is from 0 to 2,000,000. 4. The image forming method according to claim 3 , wherein the crosslinked polyester has a THF-insoluble content of 8% or less. 5. A method according to claim 1, wherein the release layer of nylon resin is used as a surface layer.
The charging member having a linear pressure of 5 to 5
A charging step of applying an external voltage to the charging member to charge the electrostatic latent image carrier, and forming an electrostatic latent image on the charged electrostatic latent image carrier by exposure Exposure step, a developing step of developing an electrostatic latent image with a developer having toner to form a toner image on the electrostatic latent image carrier, and transferring the toner image on the electrostatic latent image carrier to a transfer material An image forming developer for use in an image forming method including a transfer step and a cleaning step of removing toner remaining on the latent electrostatic image bearing member, the developer comprising: 100 parts by weight of a binder resin ; 30-15
0 parts by weight and 0.1 to 3 parts by weight of the negative charge control agent
Negative for chromatic and magnetic toner, a negatively chargeable colloidal silica
Chargeable magnetic one-component developer der is, obtained by condensation as a main component monomer binder resin has at least trihydric or higher polyhydric alcohol and / or trivalent or more carboxylic acid The crosslinked polyester has a THF insoluble content of 70% or less, a Tg (glass transition point) of 40 to 70 ° C, and a weight average molecular weight of 50%.
The developer for image formation, wherein the amount of the developer is from 2000 to 2,000,000. 6. The image forming developer according to claim 5 , wherein the crosslinked polyester has a THF-insoluble content of 5% or less. 7. A charging step for charging an electrostatic latent image carrier,
An exposure step of forming an electrostatic latent image on the charged electrostatic latent image carrier by exposure, and developing the electrostatic latent image with a developer having toner to form a toner image on the electrostatic latent image carrier Process, the conductive charge of the transfer device to the latent electrostatic image bearing member
Transferring a transfer member having a conductive layer at a linear pressure of 3 g / cm or more, applying a voltage to the transfer member, and electrostatically transferring the toner image on the latent electrostatic image bearing member to a transfer material; and In an image forming developer for use in an image forming method having a cleaning step of removing a toner remaining on an electrostatic latent image carrier, the developer comprises: 100 parts by weight of a binder resin ;
0 parts by weight and 0.1 to 3 parts by weight of the negative charge control agent
Negative band to be closed with magnetic toner and a hydrophobic colloidal silica
Ri conductive magnetic one-component developer der, obtained by condensation as a main component monomer binder resin has at least trihydric or higher polyhydric alcohol and / or trivalent or more carboxylic acid A crosslinked polyester, wherein the crosslinked polyester is
The THF insoluble content is 70% or less, the Tg (glass transition point) is 40 to 70 ° C., and the weight average molecular weight is 500
A developer for image formation, wherein the amount is from 0 to 2,000,000. 8. The image forming developer according to claim 7 , wherein the crosslinked polyester has a THF insoluble content of 8% or less.