JP2502353B2 - Developer for reversal development - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a reversal developing agent for reversal developing an electrostatic charge image in electrophotography, electrostatic recording, electrostatic printing, etc.,
In particular, the present invention relates to a reversal developing agent containing an insulating one-component toner which is developed by utilizing triboelectric charging.

[Background technology]

Conventionally, as an electrophotographic method, U.S. Pat.No. 2,297,691, Japanese Patent Publication No. 42-23910 (US Pat. No. 3,666,363), Japanese Patent Publication No. 43-24748 (US Pat. No. 4,071,36)
A number of methods are known, but generally, a photoconductive substance is used to form an electric latent image on the photoconductor by various means, and then the latent image is developed into a powder. (Hereinafter, referred to as toner) is developed, and the toner image is transferred to a transfer material such as paper, if necessary, and then fixed by heating, pressure or solvent vapor to obtain a copy. When the method has a step of transferring a toner image, it usually has a step of removing the residual toner on the photoconductor.

A developing method for visualizing an electric latent image using toner is as follows.
For example, there are methods using a two-component developer such as a magnetic brush method described in U.S. Pat.No. 2,874,083 and a cascade developing method described in U.S. Pat. Gives a relatively stable and good image, but has the drawback of deteriorating the carrier and varying the mixing ratio of the toner and the carrier.

In order to avoid the problems of the above-mentioned two-component developing method, JP
There is known a developing method using an insulating magnetic toner as disclosed in JP-A-54-42141 or a non-magnetic one-component toner as disclosed in JP-A-58-143360. As a developing method using such an insulating single-component toner, a magnetic blade or a magnetic blade as disclosed in JP-B-59-8831 or a developing blade, which is a developer carrying member, can be used.
As disclosed in Japanese Patent No. 38, a pressing member in which the tip and abdomen of the developing sleeve are pressed against each other is used to form a thin layer of toner on the developing sleeve, and the toner on the developing sleeve is rubbed to generate a necessary charge. It is generally applied and developed. In particular, the latter method of forming a toner layer by pressing a pressing member exhibits excellent stability against environmental changes. Such a one-component developing method has excellent characteristics such as no change in toner concentration and a compact and inexpensive apparatus, but toner is high in order to form a visible toner image of good image quality. It must have fluidity and be uniformly charged. Therefore, conventionally, silica fine powder is added to and mixed with the toner powder. Such silica fine powder has been conventionally made hydrophobic in order to increase the charging stability in each humidity environment, and negatively charged silica fine powder is added to negatively chargeable toner. There is. However, when silica fine powder having a strong negative charging property is used, the toner is repeatedly charged by friction between the toner and the sleeve in the toner carrying portion of the developing device in which toner consumption such as solid white areas is not performed. It becomes too big, causing the so-called charge-up phenomenon,
A phenomenon such as a decrease in image density appears. Such a phenomenon is particularly remarkable in the developing system using the pressing member in which the toner is strongly rubbed on the sleeve.

This phenomenon can be solved by scraping off the toner adhering to the sleeve with a scraper and replacing the toner on the sleeve.However, since the scraper scrubs strongly on the sleeve, the toner on the sleeve does not melt. If the wearing or scraper accuracy is not improved, there is a disadvantage that defective scraping or the like may occur, which makes practical application difficult.

[Object of the Invention]

An object of the present invention is to provide a developer for reversal development in which toner charging is stable even in a portion such as solid white that is not accompanied by toner consumption and a stable image is always obtained.

Another object of the present invention is to provide a developer for reversal development, which has good fluidity, a thin toner layer is easily formed on a sleeve, and a stable high-quality image can be obtained for a long period of time. Still another object of the present invention is to provide a reversal development developer in which fog, which is caused when the development contrast is lowered, so-called reversal fog is extremely suppressed.

[Outline of the present invention]

The present invention relates to negatively charged toner particles; granulated particles formed from a mixture of an organic fatty acid metal salt and a metal oxide of the metal salt; and a surface-treated dry method having a nitrogen-containing organic group on at least the surface. Fine silica powder 0.1-based on toner particles
It relates to a developer for reversal development, which comprises at least 2% by weight.

[Specific Description of the Invention]

In the present invention, the negatively chargeable toner particles are preferably negatively chargeable insulating toners, and the granulated particles preferably have an average particle diameter equal to that of the toner to 1/30. The surface-treated dry silica preferably has an average particle size of 5 μm or less (more preferably 1 μm or less).

In the present invention, a negatively charged toner powder in which a magnetic material, a charge control agent, a colorant, an anti-offset agent, other additives and the like are dispersed and contained in a binder resin as necessary has a particle size of substantially 5 μm or less. Which is a fine silica powder produced by the dry manufacturing method of 1., which is treated with an aminosilane coupling agent and / or an amino-modified silicone oil, and which has a surface having an amino group and is granulated into particles having almost the same particle size as the toner. It is a developer for developing an electrostatic image in which an oxide and an organic fatty acid salt of the metal are added and mixed.

Although the details of the above-mentioned charge diap phenomenon are not clear due to the positive silica fine powder having an amino group on the surface which is added to and mixed with the negatively chargeable toner, it tends to be suppressed because the negatively chargeable property of the toner is relaxed. It was found by the present inventor that the resulting image density is stable, but as it is, the fog increases as the development contrast potential is lowered contrary to the usual fog, so-called reverse fog development occurs. . This is because the negatively charged toner attracts positively charged silica around the toner particles due to its negatively charged property, and when the amount of silica attached to the surroundings increases and the amount of silica increases, the apparent silica including the silica attached to the surroundings becomes apparent. The charged state of the toner becomes positively charged. Therefore, the toner having the above-mentioned anti-polarity also adheres to the image white portion which should not be originally developed by the toner, and this lowers the development contrast, that is, the latent image surface and the developer carrier. The weakening of the electric field is the so-called reversal fog phenomenon in which toner adheres to the white areas of the image as the toner is set so as not to be originally developed by applying a bias so that the opposite electric field is applied. It is considered to be.

On the other hand, various experiments revealed that the organic fatty acid metal salt was found to have the effect of enhancing the cohesiveness with respect to the toner, and this was because the apparent amount of externally added silica worked as if it had been lowered. That is, it is considered that the organic fatty acid metal salt has an effect of attracting silica to the surroundings. Such an organic fatty acid metal salt itself has a very strong adhesive property, and it is considered that silica cannot be easily detached from its surroundings. According to the inventor's view, the addition of the organic fatty acid metal salt causes positively charged silica to gather around the silica and acts like a strong positively charged carrier material, and is integrated with the toner. It seems that the toner works negatively and is negatively charged. This tendency is particularly great if the organic fatty acid metal salt contains about 5% to 50% by weight of a metal oxide because it has a strong opposite polarity to silica. In particular, when it is dispersed in an organic fatty acid metal salt, the addition of an oxide of the same metal as the metal salt leads to the best results in order to improve the dispersion. That is, the charge of the mixed granules of the metal oxide and the organic fatty acid salt of the metal has a polarity opposite to that of the toner and is weaker than the charge state of the added silica. It is considered that the polarity of the silica becomes opposite and the behavior of the above-mentioned silica which makes the toner apparently opposite polarity is suppressed, and the effect of attracting the silica to the periphery of the mixed granulated particles is produced. As a result, it is considered that the mixed granulated particles holding silica around them act as micro-carriers having a polarity opposite to that of one toner, and as a result, so-called reversal fog is suppressed. Further, this microcarrier itself may cause adhesion to the white area of the image, but since the color tone is almost white or colorless, it does not result in fogging or other image contamination. In particular, the reversal fog phenomenon hardly occurs in normal regular development (developing a latent image having a reverse polarity of toner), and is remarkable in the reversal development having a voltage of the same polarity as that of the high toner in the white portion of the image. This is because the white area of the image remains charged at a high voltage, and the black area of the image is reduced by light with a laser beam or liquid crystal shutter.
This is because a large fog-eliminating bias voltage is applied to the developing device in order to maintain a stable white portion potential and to compensate for variations in the charging potential when forming a reverse latent image. In the case of normal regular development, for example, the bias for fog removal is about 100 to 150 V with respect to the white area potential of 100 V, and the difference is 0 to 50 V.
On the other hand, in the reversal development, a reverse bias of 400 to 500 V is applied to the white part potential of 700 V. That is, since the difference reaches 200 to 300 V, the fog caused by the reversal becomes a very serious problem.

As described above, the present invention is to suppress this reversal fog. However, as described above, the charge state of the granulated mixture of the metal oxide and the organic fatty acid salt of the metal has a polarity opposite to that of the toner, and It is necessary to select a charge state that is weaker than that of the added silica, that is, a polarity opposite to that of silica in terms of only the relationship with silica. As mentioned above, the organic fatty acid metal salt is mixed with an oxide of the same metal in an amount of 5-10
It can be achieved by adding wt% and making its size substantially the same particle size as the toner. That is, 1 to 30
The granulation mixture of 1 to 30 μm may be added to the toner of μ. In this case, as is clear from the above description,
Since it seems that the externally added silica is attracted to its surroundings to behave, it is important that the amount of silica externally added be equal to or more than the externally added amount of this granulation mixture.

As the silica fine powder used in the present invention, dry silica, which is so-called dry or fumed silica, produced by vapor phase oxidation of a silicon halogen compound can be used. It is considered that this is because the charging ability is stronger than that of so-called wet silica produced from water glass, and the effect of the present invention is sufficiently brought about. Examples of the amino group-containing treating agent used in the present invention include aminosilane coupling agents and amino-modified silicone oils.

Aminosilane is a so-called amino-functional silane and is represented by the following general formula.

XmSiYn (X is an alkoxy group, m is an integer of 1 to 3, Y is primary to 3
A hydrogen group having a nitrogen-containing group such as a primary amino group, n is 3 to
It is an integer of 1. ) Specific examples of the aminosilane represented by the general formula include the following.

[Exemplified aminosilane]

2) H ₂ N-CONH-CH ₂ CH ₂ CH ₂ -Si- (OC ₂ H ₅ ) ₃ 3) H ₂ N-CH ₂ CH ₂ CH ₂ -Si- (OC ₂ H ₅ ) ₃ 4) H _{2 N-CH 2 CH 2 NHCH 2} CH 2 CH 2 -Si- (OCH 3) 3 5) H 2 N-CH 2 CH 2 CH 2 Si- (OCH 3) 3 6) H 2 N-CH 2 CH 2 NHCH _{2 CH 2 NHCH 2 CH 2 CH} 2 -Si- (OCH 3) 3 7) H 5 C 2 OCOCH 2 CH 2 NHCH 2 CH 2 CH 2 -Si- (OCH 3) 3 8) H 5 C 2 OCOCH 2 CH _{2 NHCH 2 CH 2 NHCH 2 CH} 2 CH 2 -Si- (OCH 3) 3 9) H 5 C 2 OCOCH 2 CH 2 NHCH 2 CH 2 NHCH 2 CH 2 NHCH 2 CH 2 NHCH 2 CH 2 C
_{H 2 -Si- (OCH 3) 3} 10) NH 2 C 6 H 4 -Si- (OCH 3) 3 11) C 6 H 5 NHCH 2 CH 2 CH 2 -Si- (OCH 3) 3 12) poly aminoalkyl Trialkoxysilane These aminosilanes are used alone or in combination of two or more.

As a treatment method, a method of spraying or vaporizing and spraying aminosilane or a solution thereof onto a dry silica fine powder while stirring, a method of dropping an aminosilane or a solution thereof onto a slurry silica fine powder while stirring , Other methods are used. Then, by such a treatment, amino-modified silica is obtained.

As the silicone oil having an amine in the side chain, a silicone oil represented by the formula (I) and containing a structural unit can be generally used.

(Here, R ₁ represents hydrogen, an alkyl group, an aryl group, or an alkoxy group, R ₂ represents an alkylene group, a phenylene group, and R ₃ and R ₄ represent hydrogen, an alkyl group, or an aryl group. The above alkyl group, aryl group, alkylene group and phenylene group may contain an amine, and may have a substituent such as halogen within a range not impairing the charging property.) A commercially available side chain The amine-containing silicone oil is preferably an amino-modified silicone oil represented by the following structural formula. that is (Here, R ₁ and R ₅ represent the same or different groups, represent an alkyl group or an aryl group, R ₂ represents an alkylene group, a phenylene group or an argyl group containing an amine, and R ₃ represents hydrogen, an alkyl group or Represents an aryl group, m is zero or a positive integer, and n is an integer of 1 or more.) Specifically, the following silicone oils are preferable, and these are 1 type or 2 types. It may be used in the above mixed system.

The amine equivalent in the present invention is the equivalent per amine (g / eqiv) and is the value obtained by dividing the molecular weight by the number of amines per molecule.

The treating amount of the silicone oil having an amine in the side chain in the present invention is 2 to 30 parts by weight of the silicone oil having an amine in the side chain with respect to 100 parts by weight of the fine silica powder. It is more preferably 5 to 20 parts by weight. The reason is that if the amount of the silicone oil having an amine in the side chain is too small, the fine silica powder does not become positive, and if it is too large, silica lumps are likely to be formed during the treatment.

On the other hand, 25 ° C of silicone oil having amine in the side chain
The viscosity is preferably 5000 cps or less, and particularly preferably 3000 cps or less. When the viscosity is 5000 cps or more, the silicone oil having an amine in the side chain is insufficiently dispersed in the silicic acid fine powder, which easily causes a defective image such as fog.

The above-mentioned treatment of the dry silica fine powder with the silicone oil having an amine in the side chain can be carried out, for example, as follows. The dry silica powder is violently agitated while being heated if necessary, and the silicone oil having the amine on the side chain or a solution thereof is sprayed or vaporized and sprayed on the dry silica powder, or the dry silica fine powder is slurried. It can be easily treated by adding a silicone oil having an amine to the side chain or a solution thereof while stirring.

Further, as described above, one kind or a mixture of two or more kinds of silicone oil having amine in the side chain may be used.

The volume average diameter of the silica fine powder having amino groups on the surface thus obtained is more preferably in the range of 0.05 to 5μ.
It is in the range of 0.05 to 2μ.

If the particle size is too large, it becomes difficult to obtain sufficient fluidity as a one-component toner, and if the particle size is too small, silica fine powder having an amino group on the surface covers the toner surface. As a result, the toner tends to be positively charged, which causes problems such as fog and a decrease in density.

In order to measure the particle size of the silica fine powder according to the present invention, various conventionally known particle size distribution measuring devices can be used. Most preferred is a device for dispersing particles in a conductive liquid and measuring the number and volume of particles by amplifying the electrical resistance change of the liquid that occurs when the particles pass through pores. This is a commercially available device. The particles are decomposed into about 0.1% saline and measured using a 30 μm aperture.

Further, the amount of the silica fine powder having an amino group on the surface of the negatively charged toner is 0.05 to 0.05 based on the weight of the toner.
It is 2.0% by weight, more preferably 0.1 to 1.0% by weight. This is because if the addition amount is too small, the required fluidity cannot be obtained, and if the addition amount is too large, the toner becomes positive, which causes adverse effects such as fog and reduction in density.

Further, the metal used in the mixture of the metal oxide used in the present invention and the organic fatty acid salt of the metal is a metal such as aluminum, magnesium, zinc, etc., and the organic fatty acid such as lauric acid, stearic acid, palmitic acid, etc. It produces salt.

Examples of the binder resin of the toner used in the present invention include homopolymers of styrene and its substitution products such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, styrene-p-chlorostyrene copolymer, and styrene-vinyltoluene copolymer. Copolymers thereof; styrene-methyl acrylate copolymers, styrene-ethyl acrylate copolymers, styrene-acrylic acid ester copolymers such as styrene-n-butyl acrylate copolymers; styrene-methacryl Copolymers of styrene with methacrylic acid esters such as methyl acid acid copolymers, styrene-ethyl methacrylate copolymers, styrene-n-butyl methacrylate copolymers; multi-components of styrene with acrylic acid esters and methacrylic acid esters Copolymer; Other styrene-acrylonitrile copolymer, styrene -Styrene and other vinyl-based monomers such as vinyl methyl ether copolymer, styrene-butadiene copolymer, styrene-vinyl methyl ketone copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid ester copolymer Styrene-based copolymer with; polymethylmethacrylate, polybutylmethacrylate, polyvinyl acetate, polyester, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid, phenol resin, aliphatic or alicyclic hydrocarbon resin, petroleum Resins, chlorinated paraffins, etc. can be used alone or in combination.

In particular, as a binder resin for a toner to be subjected to a pressure fixing method, low molecular weight polyethylene, low molecular weight polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, higher fatty acid, polyamide resin,
Polyester resins and the like can be used alone or in combination.

When the polymer, copolymer, or polymer blend used contains a vinyl aromatic or acrylic monomer represented by styrene in an amount of 40 wt% or more, more preferable results are obtained.

Any suitable pigment or dye can be used as a colorant in the toner. For example, there are known dyes and pigments such as carbon black, iron black, phthalocyanine blue, ultramarine blue, quinacridone, and benzidine yellow.

When the toner is magnetic toner, iron, cobalt,
Ferromagnetic elements such as nickel, magnetite,
It is sufficient to contain iron, such as hematite and ferrite, alloys and compounds such as cobalt, nickel and manganese, and magnetic materials such as other ferromagnetic alloys. Magnetic material is a binder resin
It is preferable to use 10 to 150 parts by weight based on 100 parts by weight.

You may mix an additive with a toner as needed. Examples of such additives include lubricants such as Teflon and zinc stearate, fixing agents (such as low molecular weight polyethylene), and metal oxides such as tin oxide as a conductivity-imparting agent.

Although any charge control agent can be used in the toner, in view of the gist of the present invention, a negatively chargeable one such as a metal-containing azo dye, a salicylic acid-containing metal compound, an alkylsalicylic acid-containing metal compound, or a dialkylsalicylic acid-containing metal compound. Is preferred. The particle size of the toner having the above-mentioned constitution can be used within a normal range, but if possible, it is preferable that the amount of ultrafine powder is small.
It is preferably 8% or less (Coulter counter measurement, number distribution).

The developer of the present invention having such a constitution does not cause so-called charge diap even when a white background such as solid white continues in a one-component developing method using a developing device having a pressing member, and provides a stable image. Is obtained.

The basic structure and features of the present invention have been described above, but the method of the present invention will be specifically described below based on Examples. However, this does not limit the embodiment of the present invention at all. The numbers of parts in the examples are parts by weight.

[Example 1] The above mixture was kneaded with a roll mill at 150 ° C to 160 ° C,
After cooling, the product was ground with a jet mill and classified by air force to obtain a negatively chargeable insulating magnetic toner classified product having 5% of fine particles having a volume average diameter of 11 μm to 4 μm.

Next, 100 parts of dry silica fine powder having a particle size of 0.05μ was spray-treated with 5 parts of γ-aminopropyltriexisilane diluted with a solvent, and dried to obtain surface-treated dry silica fine powder having an amino group on the surface. Obtained. Granulated particles (volume average particle size 4 μm) of 0.4 part of this treated silica fine powder and a mixture of 14% by weight of zinc oxide and 86% by weight of zinc stearate.
0.1 part was externally added to 100 parts of the toner to obtain a developer.

When this developer was used and development was carried out using a developing device of a commercially available copier Selexx 60AZ (see FIG. 1 attached), a good image having an image density of 1.3 to 1.4 and free of fog was obtained. After that, when 100 solid white images were copied and the images were printed out immediately afterward, the image density was 1.3 to 1.4, which was good. Further, 1,000 sheets of paper were run using this developer and apparatus, but the image density was stable at 1.3 to 1.4 from the beginning to the end, and there were no other adverse effects such as fog. Further, an inversion bias was applied by an external power supply so that the inversion bias would be 400 V with respect to the white electrode, but no inversion fog occurred.

Example 2 100 parts of dry silica fine powder having an average particle size of 3 μm was treated with 10 parts of silicone oil having an amine in the side chain (KF-857 manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.6 part of silica fine powder having amino groups on the surface was treated. A developer was obtained in the same manner as in Example 1 except that external addition was performed, and the same test as in Example 1 was performed. As a result, 100 solid images were taken before and after the image density was 1.3 to 1.4, and there was no fog. An image was obtained. Also, there was no problem even with the durability of 10,000 sheets. Further, the same reversal fog test as in Example 1 was conducted, but there was no problem.

[Comparative Example 1] A similar test was conducted except that the dry silica fine powder of Example 1 was changed to 0.3 part of commercially available negatively charged hydrophobic dry silica fine powder R-972 (manufactured by Nippon Aerosil Co., Ltd.). The image density was 1.3 to 1.4 before the image was taken, but it decreased to 1.0 after 100 solid white images.

Comparative Example 2 Silica having an amino group on the surface used in Example 2
When the same test as in Example 2 was carried out except that 2.2 parts were added externally, the image density before and after solid white did not change, but the image density was about 1.2, and fog appeared on the copy paper.

[Example 3] 100 parts of dry silica fine powder having an average diameter of 2.5μ was treated with 15 parts of silicone oil KF-865 (manufactured by Shin-Etsu Chemical Co., Ltd.) having an amino group in a side chain. When the same test as in Example 1] was performed, the image density was 1.4 even before and after 100 solid white images. Also, there was no problem in the durability test of 10,000 sheets. Further, a reversal fog test was conducted in the same manner as in Example 1, but extremely good results were obtained.

Example 4 Granulated particles of a mixture of 90% by weight aluminum laurate and 10% by weight aluminum oxide particle size (average particle size 6
The same results as in Example 1 were obtained by conducting the same tests as in Example 1 except that 0.3 part of (μm) was externally added.

[Example 5] 0.4 parts of granulated particles (average particle size 10µ) of a mixture of 0.6 parts of the treated silica used in Example 3, 90% by weight of magnesium stearate and 10% by weight of magnesium oxide were added. When the same test as in Example 1 was performed, the same result as in Example 1 was obtained. [Comparative Example 3] The same operation as in Example 1 was carried out except that wet silica having an average particle size of 4 µ was used, but the image density was 0.4 to 0.5.

[Comparative Example 4] Except that no granulated particles were added and 100 parts by weight of dry silica fine powder having an average particle size of 5.5 was treated with 5 parts of γ-aminopropyltriethoxysilane and 1.0 part was externally added. A developer was prepared in the same manner as in [1] and tested in the same manner as in Example 1. As a result, the image density around 100 solid white sheets did not change at about 1.3, but at the durability of 4,000 sheets, due to poor fluidity. The band-like unevenness that seems to have appeared.

[Brief description of drawings]

The accompanying drawings show a schematic cross-sectional view of a developing device used in a developing test of a developer. 1 ... Developer 2 ... Development sleeve 3 ... Magnet 4 ... Iron blade 5 ... Iron blade holding member 6 ... Developer hopper outer wall 7 ... Photoconductor

Claims (2)

(57) [Claims] 1. Negatively charged toner particles, granulated particles formed from a mixture of an organic fatty acid metal salt and a metal oxide of the metal salt, and surface-treated dry silica having a nitrogen-containing organic group on at least the surface thereof. A developer for reversal development comprising at least 0.1 to 2% by weight of fine powder based on toner particles. 2. The surface-treated dry silica fine powder comprises a dry silica and a silane coupling agent having a nitrogen-containing organic group, and / or
The developer for reversal development according to claim 1, which has been treated with a silicone oil having a nitrogen-containing organic group.