JPH0535082A - Image forming method - Google Patents

Abstract

PURPOSE:To obtain an excellent image over a long period by making the electrifying quantity of toner large, and electrifying speed fast, and improving environmental dependency, in this image forming method for using positively electrifiable toner, as a one-component developer. CONSTITUTION:The layer of the developer 7 is formed on a developer carrier 12 by a layer forming member 2 attached to a spring member and composed of a soft elastic member, the layer forming member 2 satisfies LN>=LR when the width of the soft elastic member is defined as LR, and virtual nip width with respect to the developer carrier 12 is defined as LN. Then, in the image forming method for developing an electrostatic charge image on an electrostatic latent image carrier 6 on the next developing region, inorganic fine powder processed through the use of a positively electrifiable processing agent such as quaternary ammonium salt is added to the toner, is used as the developer.

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 for developing an electrostatic latent image using a one-component developer.

[0002]

2. Description of the Related Art In electrophotography and the like, developers used for developing an electrostatic image are roughly classified into those used in a two-component developing system and those used in a one-component developing system. In the two-component developing method, toner particles adhere to the surface of the carrier to deteriorate the developer, and
Since only the toner is consumed, it is necessary to keep the concentration ratio of the toner in the developer constant, which causes a drawback that the developing device becomes large. On the other hand, the one-component developing method is becoming the mainstream of the developing method because it does not have the above-mentioned drawbacks and has advantages such as downsizing of the apparatus. Various so-called one-component developers used in the one-component developing system have been proposed so far.

By the way, as a method of giving an appropriate triboelectric charge amount to a one-component magnetic toner, various companies have been
(I) A method of charging between the trimmer bar and the developing sleeve, (ii) A method of charging between the rubber blade and the developing sleeve, (iii) A method of charging with carrier particles of appropriate size (not developed) However, the above-mentioned method has the following drawbacks, particularly for the purpose of speeding up one-component development and improving image quality. (I) In particular, in order to improve the image quality, a wide charge amount distribution becomes a problem. (Ii) For speeding up, the toner is solidified by the heat generated by the pressure contact of the rubber blade. (Iii) It is difficult to precisely control the ratio of carrier to toner.

In order to solve these problems, the applicant of the present invention has previously proposed the following one-component developing device (Japanese Patent Application No. 2-248803). In this one-component developing device, a virtual nip width that varies depending on the hardness and thickness of the soft elastic body or the nip pressure to the developing roll, etc. is defined, and the soft elastic body is formed so that the virtual nip width is not more than this virtual nip width. I try to determine the width. When this one-component developing device is used, the unevenness of layer formation due to the change in the nip width over time, which is seen in the conventional method, is improved, and since the blade can be set to a small pressure contact force to the sleeve, There is an advantage that the plastic and thermal damage to the toner can be extremely reduced.

[0005]

However, when the compatibility of various toners was confirmed by making a copy using this one-component developing device, it was found that the positively charged toner usable in the conventional method was It was found that the performance (chargeability and developability) was not fully exhibited. The reason for this is not clear, but it is considered that the method using this one-component developing device has an extremely weak pressure contact force with the sleeve as compared with the conventional method, and thus the charge imparting ability to the toner is inferior. The present invention has been made in view of the above circumstances. That is, an object of the present invention is to provide an image forming method using a positively chargeable one-component developer, in which a toner has a high charge amount, a charging speed is fast, environmental dependence is improved, and a good image is obtained for a long time. To provide.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, by using a toner to which an inorganic fine powder treated with a positively chargeable treating agent is added, The inventors have found that the object is achieved and completed the present invention.

In the image forming method of the present invention, a layer forming member made of a soft elastic member attached to a spring member forms a layer of a developer on a developer carrying member, and the layer forming member has a width of the soft elastic member. Where L N is the virtual nip width with respect to the developer carrying member and L N is L N, and L N ≧ LR is satisfied. Then, in an image forming method for developing an electrostatic charge image on the electrostatic latent image carrying member in the developing area. , As the developer,
It is characterized in that an inorganic fine powder treated with a positively chargeable treating agent is added to a toner. In the present invention, the inorganic fine powder is preferably silica, particularly hydrophobic silica, and the positively chargeable treating agent is preferably one having a quaternary ammonium group as a functional group.
Here, the virtual nip width means the nip width LN that initially occurs when only a part of the soft elastic member 22 having a sufficiently large forming width LR is nipped into the sleeve 12 of the developer carrying member, as shown in FIG. That is.

The one-component developing device used in the present invention is arranged so as to face the electrostatic latent image carrier and conveys the developer contained in the hopper to the developing area, and one end of the spring plate member. And a developer regulating member for nipping a layer forming soft elastic member to the developer carrying member to form a thin layer of the developer, wherein the layer forming soft elastic member is LN ≥ The relationship is such that LR is satisfied.

FIG. 1 is a schematic configuration diagram of an example of a one-component developing device for carrying out the present invention, and FIG. 2 is an enlarged view of the main part thereof. This one-component developing device is composed of a developing roll 1 arranged to face the electrostatic latent image carrier 6 and a developer regulating member 2 arranged so that its tip portion is in pressure contact with the developing roll. It is disposed in the hopper 3 that contains the developer 7. The developing roll 1 includes a magnet roll 11 and a cylindrical sleeve 12 that rotates around the magnet roll. The developer T is adsorbed, conveyed, and released from the sleeve 12 as the sleeve 12 rotates. Is performed according to the magnetic pattern of the magnet roll 11. The developer regulating member includes a spring plate member 21, a soft elastic member 22 adhered to the tip thereof, and a support member 23 that supports the rear end of the soft elastic member. The support member 23 is fixed to the holder 4, and the holder is biased by the coil spring 5 so that the soft elastic member 22 always nips the sleeve 12 with a constant linear pressure.

When the present invention is carried out by using the above-described one-component developing device, the developer is contained in the hopper 3, and the developer regulating member 2 forms a thin layer of the developer on the sleeve 12 of the rotating developing roll 1. To form. The thin layer of the developer on the sleeve 12 is conveyed to the developing area by the rotating sleeve and visualizes the electrostatic latent image on the electrostatic latent image carrier 6 facing the sleeve. In the case of the present invention, the developer regulating member is formed so that the width LR of the soft elastic member 22 bonded to the tip of the spring plate member 21 is equal to or smaller than the virtual nip width LN. There is. For example, when the virtual nip width is 3.3 mm, the width of the soft elastic member is set to 1.2 mm. As the soft elastic member, a rubber agent such as silicone rubber, EPDM rubber, urethane rubber, fluorine rubber, butadiene rubber, acrylic rubber, or a thermoplastic elastomer can be used. However, they have a surface energy of 30.
It is preferably dyne / cm or less and the hardness is 30 to 70 °.

On the other hand, as the developer in the present invention, a toner containing an inorganic fine powder treated with a positively chargeable treating agent is used. As the toner, any one can be used as long as it can be used as a one-component developer, and a known binder resin such as a styrene resin, a polyester resin, a polyamide resin, or an epoxy resin can be used. Use, depending on the desired color tone, carbon black, magnetic powder, pigments, dyes, etc. are added, if necessary, a salicylic acid metal salt, a charge control agent such as nigrosine or a quaternary ammonium salt, low molecular weight propylene, a low molecular weight polyethylene,
It is possible to use those to which other known components such as an offset preventing agent such as wax are added. In particular, magnetic toner can be preferably used.

The surface of the inorganic fine powder added to the toner is treated with a positively chargeable treating agent. In order to obtain the positively chargeable inorganic fine powder, the untreated inorganic fine powder is mixed with the side surface. A method of treating with a silicone compound having an organic group having at least one nitrogen atom in the chain, a method of treating with a silicone compound such as a silicon varnish, a silicone resin, or a method of treating with a nitrogen-containing silane coupling agent, and treating with a quaternary ammonium salt. A method, a method of treating with a plurality of these, or the like is adopted. As the inorganic fine powder, silica, titania, alumina, magnesium oxide, tin oxide or the like can be used. In particular, silica is preferably used. Further, as a cleaning aid or a transfer aid, an organic fine powder such as polymethylmethacrylate fine particles may be added and used in combination.

As the silicone compound used for the surface treatment of the inorganic fine powder, silicone oil having at least a partial structure represented by the following formula can be preferably used.

[0014]

[Chemical 2]

(Wherein R ₁ is a hydrogen atom, an alkyl group,
An aryl group or an alkoxy group, R ₂ represents an alkylene group or a phenylene group, and R ₃ and R ₄ represent
Each represents a hydrogen atom, an alkyl group, or an aryl group, and R ₅ represents a nitrogen-containing heterocyclic group. ) The alkyl group, aryl group, alkylene group, and phenylene group may have an organo group having a nitrogen atom, or may have a substituent such as halogen within a range not impairing the charging property. .

As the nitrogen-containing silane coupling agent, one having a structure represented by the following formula (I) is generally mentioned. (R ₆ ) _m Si (Y) _n (I) (In the formula, R represents an alkoxy group or a halogen atom, Y represents an amino group or an organic group having at least one nitrogen atom, and m and n Are 1 to 3 respectively
Of m + n = 4. )

Examples of the above-mentioned organic group having at least one nitrogen atom include an amino group having an organic group as a substituent, a nitrogen-containing heterocyclic group or a group having a nitrogen-containing heterocyclic group. As the nitrogen-containing heterocyclic group, there are an unsaturated heterocyclic group and a saturated heterocyclic group, and known ones can be applied. Examples of the unsaturated heterocyclic group include the following.

[0018]

[Chemical 3]

Examples of the saturated heterocyclic group are shown below.

[Chemical 4]

In the present invention, the above heterocyclic group is
In consideration of stability, a 5-membered ring or a 6-membered ring is preferable. Examples of the treating agent represented by the general formula (I) include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutyl. Aminopropyltrimethoxysilane, monobutylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-r-propylphenylamine , Trimethoxysilyl-r-propylbenzylamine and the like, and examples of the case of further containing a nitrogen-containing heterocycle include trimethoxysilyl- - propyl Hipe lysine, trimethoxysilylpropyl -γ- propyl morpholine, trimethoxysilylpropyl -r- propyl imidazole, and the like.

In the present invention, a quaternary ammonium salt can be used as a treating agent. As the quaternary ammonium salt, the quaternary ammonium salt of the treating agent represented by the above general formula (I) can be mentioned, and in particular, the one represented by the following general formula (II) can be preferably used.

[0022]

[Chemical 5] (In the formula, R, R ′ and R ″ are respectively CH ₃ or C ₂
Indicates H _5, X represents Cl or Br, n is an integer of 2 to 5, m is an integer of 10-20. )

As a method for treating the surface of the inorganic fine particles with the above compound, a method of dissolving the compound in a solvent, coating the surface of the inorganic fine powder, and then drying the solvent is generally used. Specifically, a kneader is used. Equipment such as a coater, a spray dryer, a thermal processor, and a fluidized bed is used. Also,
If necessary, pulverization and classification may be performed after drying. As an example, for a double-arm type kneader, for hydrophobic silica,
Add 10% of the above compound in solid content and add about 1 in toluene.
Disperse for 0 minutes. Then, 120 ° in a hot air dryer
C, heating is performed for 2 hours to perform a curing treatment. Furthermore, Pulv
Mill with an erizer AD-S type hammer mill.

In the present invention, the silica fine particles to be treated have a primary particle diameter of 40 nm or less, more preferably 20 n.
It is preferably m or less. In addition, the silica fine powder,
The surface is preferably hydrophobized. Hydrophobization is
The treatment is performed before the treatment with the compound that imparts a positive charge with a hydrophobizing agent such as a silane coupling agent, but may be performed simultaneously with the treatment with the compound that imparts a positive charge.

The amount of silica fine powder added to the toner is 0.
The range of 05% to 20% is suitable, and more desirably,
It is set in the range of 0.1% to 5%.

In the present invention, for example, the above general formula (I) is used.
The mechanism of action when the compound represented by is used as a treating agent is estimated as follows. The treating agent is CH _{3 at} the end.
O-, and a quaternary ammonium salt structure having a C ₂ H ₅ O-, these groups termini, for example, it reacts with the silanol groups of the hydrophobic silica surface, every other dealcoholation, the silica surface treating agent Is fixed. Next, when the treated hydrophobic silica is externally added to the toner, the quaternary ammonium group on the surface of the silica effectively acts and the positive chargeability is enhanced. At the same time, the treatment also improves the hygroscopicity of the silica itself, thus improving the environmental stability. Furthermore, the coupling reaction ensures the adhesion between silica and the treatment agent, and does not cause problems such as desorption before treatment due to aging.

[0027]

EXAMPLES The present invention will be described below with reference to examples. Examples 1 to 4 and Comparative Example <Preparation of Toner> Styrene-butyl acrylate 100 parts (82/18 monomer weight ratio, Mw: about 200,000) Magnetite 100 parts (particle size: 0.22 to 0.26 μm, (σs : About 80 emu / g) Low molecular weight polypropylene 3 parts Quaternary ammonium salt (Bontron P-51, 1 part manufactured by Orient Chemical Co., Ltd.) After pre-mixing the above materials with a Henschel mixer, 160
The toner was kneaded with an extruder heated to ° C, cooled, coarsely pulverized with a crusher, mechanically pulverized, and air-classified to obtain a toner having an average particle diameter of 9 µm.

To each of the toners, 0.8% of fine silica powder treated with the following four kinds of treating agents was added to prepare a developer. The treating agent used is a compound in which R, X, n and m in the above structural formula (I) are shown in Table 1 below.

[0029]

[Table 1]

An image was formed using the above-mentioned developer and the one-component developing apparatus shown in FIG. In this developing device, the thickness of the developer regulating member 2 is 0.05 mm.
Spring plate member 21 (made of SUS304 CSP3 / 4H;
A tensile strength of 95 kgf / mm ² ) and a soft elastic member 22 (made of silicone rubber: rubber hardness 50 °, thickness 1 m) adhered to the tip of this spring plate member and having a molding width LR = 1.0 mm.
m) and a supporting member 23 (made of non-magnetic stainless steel SUS304: tensile strength 53 kgf / mm ² ) having a thickness of 1 mm for supporting the rear end of the soft elastic member. The spring plate member was fixed to the support member 23 so that the protruding length was 6 mm, and the soft elastic member was always nipped in the sleeve 12 at a linear pressure of 8 g / cm. The contact position of the developer regulating member 2 with respect to the sleeve 12 was set at a position of 175 ° from the position where the developing roll 1 and the photosensitive drum D faced each other in the direction opposite to the rotating direction of the sleeve. In the above case, the virtual nip width LN is
It was 2.7 mm, which satisfied the relationship of LN ≥LR.
As the electrostatic latent image carrier 6, a photoconductor drum having photoconductivity is used, and the gap width between the developing roll 1 and the photoconductor drum is set to 200 μm, while the sleeve 12 of the developing roll 1 is subjected to an alternating current. A frequency of 2.4 KHz and a peak to peak voltage of 2400 depending on the power supply and the DC power supply.
A DC superimposed AC voltage of V and a DC component of -200V was applied.

For comparison, a developer was prepared using hydrophobic silica that was not treated with the above-mentioned treating agent, and an image was formed under the same conditions as above. The results are shown in Table 2.

[0032]

[Table 2]

The evaluation criteria for environmental stability and temporal stability are as follows. Environmental stability: 〇… The solid concentration difference between high temperature and high humidity and low temperature and low quality is 0.1
Below, Δ ... 0.1 to 0.3, × ... same as 0.3 or more. Stability over time: ◯ ... Change in solid density between 1 million sheets is 0.1 or less,
Δ: 0.1 to 0.2, ×: 0.2 or more. From the results in Table 2 above, it is understood that in the cases of Examples 1 to 4, all of them showed higher charge amount than the comparative example, and both environmental stability and temporal stability were good.

[0034]

As described above, according to the developing method of the present invention, an image of good quality can be obtained for a long period of time by using a specific developing device and a developer. That is, the developing device reduces the impaction of the developer,
Even when copying a large number of sheets, it is possible to prevent toner from adhering to the sleeve and deterioration of the toner, and by using positively charged silica, the developer has a sufficient charge amount and charge amount distribution. A narrow image can be obtained, and a good image can be obtained over many copies.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an example of a one-component developing device used in the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is an explanatory diagram showing a virtual nip width of a soft elastic member.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Developing roll, 11 ... Magnet roll, 12 ... Sleeve, 2 ... Developer regulating member, 21 ... Spring plate member, 22 ...
Soft elastic member, 23 ... Support member, 3 ... Hopper, 4 ... Holder, 5 ... Coil spring, 6 ... Electrostatic latent image carrier, 7 ... Developer.

Claims (4)

[Claims] 1. A layer forming member made of a soft elastic member attached to a spring member forms a layer of a developer on a developer carrying member, the layer forming member having a width LR of the soft elastic member, and a developer carrying member. When the virtual nip width for the body is LN, L
In the image forming method of satisfying N ≧ LR, and then developing an electrostatic image on the electrostatic latent image bearing member in the developing region, an inorganic material treated with a positively chargeable processing agent as the developing agent. An image forming method characterized in that a fine powder added to a toner is used. 2. The image forming method according to claim 1, wherein the inorganic fine powder is silica. 3. The image forming method according to claim 1, wherein the positively chargeable treating agent has a quaternary ammonium group as a functional group. 4. The image forming method according to claim 1, wherein the positively chargeable treating agent is a compound represented by the following general formula. [Chemical 1] (In the formula, R, R ′ and R ″ are respectively CH ₃ or C ₂
Indicates H _5, X represents Cl or Br, n is an integer of 2 to 5, m is an integer of 10-20. )