JPH07117768B2 - Developer for digital latent image development - Google Patents

Description

The present invention relates to a developer for developing an electrostatically charged image in electrophotography, electrostatic recording, electrostatic printing and the like. More specifically, it relates to a developer for a digital latent image which is uniformly and strongly negatively charged in an electrophotographic process and gives a high quality image with little environmental dependence.

[Conventional technology]

In recent years, electrophotographic printers are rapidly becoming widespread as computer output devices and as printers in office automation. However, these printers are required to have high printing quality.

The laser printer, which is the mainstream of electrophotographic printers, writes the blinking of the semiconductor laser according to the output information from the computer as a digital latent image on the photoconductor drum via a rotating polygon mirror, and records it on recording paper by an electrostatic photography process. It is an output device that prints on.

In an electrophotographic apparatus such as LBP in which a latent image is composed of basic pixels (hereinafter referred to as “dots”), the output light to the photoconductor is a digital latent image composed of binary ON-OFF values. During development, the development due to the peripheral effect becomes dominant.

The peripheral effect is development in which the electric potential lines concentrate at the boundary between the exposed portion and the non-exposed portion of the latent image, the surface potential of the apparent photoconductor rises, and the image density at the boundary increases. Conventionally, this development is not preferred because it causes non-uniformity of the solid image (increase in edge image density), and a prescription to avoid it has been considered.

On the other hand, in the image forming method in which the latent image is represented by 50 to 150 μm pixels, the area that receives the peripheral effect is larger than the general analog image, and the line reproducibility is good by positively incorporating it. Can realize a developer with high image density.

The peculiarity of the development of the edge area is that the gradient of the potential is large and if the triboelectric charge amount of the developer is not sufficiently high, the gradient of the electrification amount occurs according to the gradient of the potential, and it is used selectively from the toner with the large triboelectric charge amount. As a result, the developer having a low charge amount tends to stay in the developing device, and deterioration due to durability tends to occur.

This tendency becomes stronger because the output of the character image is mainly in the system used for the printer such as the laser printer and the liquid crystal printer among the digital latent image systems. When the developer conventionally used for the above-mentioned digital latent image system is diverted, due to the peculiarity of edge development, deterioration of image value due to endurance and line thinning under high humidity conditions may become a problem. Many.

Further, in the conventional electrophotographic toner, since the electrostatic latent image is less charged in the image portion and the background is more charged on the photoconductor in the reversal development performed by a laser printer or the like, If toner with a small amount of charge is present, it will get on the highly charged background on the photoconductor, so preventing this reversal fog has been one of the most important issues in this electrophotographic process. there were.

[Problems to be solved by the invention]

The object of the present invention is, as is clear from the above description of the prior art, in the development of a digital latent image, the developer that faithfully develops and transfers the latent image, that is, the adhesion of toner in the background area during development, that is, It is possible to provide a developer capable of obtaining high image density without causing fog or scattering of toner around the edge of a latent image.

Still another object is to provide a developer which maintains the initial characteristics even when the developer is continuously used for a long period of time and does not cause aggregation of toner or change in charging characteristics.

Still another object is to provide a developer that reproduces a stable image that is not affected by changes in temperature and humidity, especially a developer with high transfer efficiency that does not cause splattering or transfer omission during transfer at high humidity and low humidity. In offer.

Still another object is to provide a developer having excellent storage stability, which maintains the initial characteristics even after long-term storage.

[Means for Solving Problems] The present invention comprises 100 parts by weight of a binder resin, magnetic powder, and 0.1 to 10 parts by weight of a metal complex compound (A) of an aromatic hydroxycarboxylic acid having a lipophilic group. 0.1 to 10 parts by weight of the metal complex salt type monoazo dye (B) having a hydrophilic group is added to the metal complex compound (A) and the metal complex salt type monoazo dye (B) in a weight ratio.
Negatively chargeable magnetic toner for dry electrophotography containing 1:10 to 10: 1, and negatively chargeable silicic acid fine powder treated with hexamethyldisilazane and further treated with silicone oil And a developer for digital latent image development, which comprises: Only the combination of the specific carboxylic acid metal complex having a hydrophilic group and the specific monoazo dye having a hydrophilic group gives a remarkable effect of equalizing the triboelectric charge of the toner.

Further, the advantage of the silicone oil treatment in the present invention is that it is a surface coating type in comparison with hexamethyldisilazane fixed to the surface of fine silicic acid powder by a chemical bond, and that the lubricating property of silicone oil is For this reason, if you rub the surface of the photoreceptor strongly during blade cleaning,
It is difficult to scratch or scratch the surface of the photoconductor. Here, although there is a treatment only with silicone oil,
A large amount of silicone oil is required to completely cover the surface of the silicic acid fine powder only by the treatment with silicone oil, and there is a drawback that aggregates are easily formed and the photoreceptor is easily scratched.

In the silicic acid fine powder in the present invention, since the silicic acid fine powder is first treated with hexamethyldisilazane, it is possible to reduce the amount of silicone oil that causes the aggregates, and to overcome the above drawbacks, silicone oil It is possible to take advantage of the processing.

Furthermore, since the above-mentioned silicone oil generally has a strong negative chargeability except for those which are amio-modified, by adding the silica fine powder treated with this to the developer, the developer is uniformly and strongly charged. It is effective for digital development in which peripheral effects are dominant.

The silicic acid fine powder in the developer used in the present invention includes both so-called dry method produced by vapor phase oxidation of a silicon halogen compound or dry silica called fumed silica and so-called wet silica produced from water glass. However, dry silica having less silanol groups on the surface and inside the silicic acid fine powder and having no production residue such as Na ₂ O and SO ₃ ²⁻ is preferable.

Further, in the case of dry silica, it is also possible to obtain a composite fine powder of silica and another metal oxide by using another metal halogen compound such as aluminum chloride or titanium chloride together with a silicon halogen compound in the manufacturing process. They are also included.

The particle size is preferably in the range of 0.001 to 2 μ as an average primary particle size, and particularly preferably, silica fine powder in the range of 0.002 to 0.2 μ is used.

In the present invention, hexamethyldisilazane is used as a silane coupling agent.

The silane coupling agent treatment of the silicic acid fine powder is a dry treatment in which the vaporized silane coupling agent is reacted with the silicic acid fine powder made into a cloud by stirring or the like, or the silicic acid fine powder is dispersed in a solvent. The treatment can be carried out by a generally known method such as a wet method in which a silane coupling agent is reacted dropwise.

The silicone oil used in the present invention is generally represented by the following formula: R: C _{1 to} C ₃ alkyl group R ″: alkyl, halogen modified alkyl, phenyl, modified phenyl or other silicone oil modifying group R ″: C _{1 to} C ₃ alkyl group or alkooxy group, for example, dimethyl silicone oil, alkyl Modified silicone oil, α-methylstyrene modified silicone oil, chlorphenyl silicone oil, fluorine modified silicone oil, etc. are listed. The silicone oil preferably has a viscosity at 25 ° C. of about 50 to 1000 centistokes. Silicon oil whose molecular weight is too low may generate rare components due to heat treatment etc.
On the other hand, if the molecular weight is too high, the viscosity becomes too high and the treatment operation becomes difficult.

A known technique is used for the method of treating silicon oil. For example, silica fine powder and silicone oil may be directly mixed using a mixer such as a Henschel mixer, or a method of spraying silicone oil onto the base silica. Is also good. Alternatively, it may be prepared by dissolving or dispersing silicon oil in an appropriate solvent, mixing with silica fine powder of the base, and then removing the solvent.

As a feature of the present invention, it is necessary that the silicone oil is exposed on the surface. Therefore, an important point of the present invention is the order of treatment of fine silicic acid powder. The silicic acid fine powder of the present invention must first be treated with a silane coupling agent and then with silicone oil.

In addition, the amount of silicon oil to be treated can be a small amount because the fine powder of silicic acid was made hydrophobic in the previous stage. A / 25 ± A / 30 (A:
Specific surface area of fine silicic acid powder), more preferably A / 25 / ± A / 4
It is preferably in the range of 0. Here, the specific surface area of the silicic acid fine powder is a value obtained from N ₂ adsorption in the BET method. The reason for limiting the above treatment amount is that if the silicone oil treatment amount is too small, the same result as that of the silane coupling agent treatment is obtained, and defects such as fusion bonding occur during cleaning.

Further, if the amount of treated silicone oil is too large, the agglomerates of the fine powder of silicic acid are likely to be formed, and moreover, free silicone oil is likely to be produced, so that the fluidity is improved when applied to a developer. Defects such as not being possible are likely to occur.

The amount of the treated silica fine powder applied to the developer is 0.01 to 20 parts by weight, more preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the developer (toner).

The toner of the present invention contains a binder resin, a metal complex compound (A) of an aromatic hydroxycarboxylic acid having a lipophilic group, and a metal complex salt type monoazo dye (B) having a hydrophilic group as essential components. Is.

Here, the lipophilic group refers to a nonpolar atomic group having a very low affinity for water and thus a high affinity for oil. Examples of the main lipophilic group include a complex hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group.

The lipophilic group contained in the structural formula of the metal complex compound (A) is preferably a chain hydrocarbon group (particularly an alkyl group) directly bonded to a cyclic (monocyclic or polycyclic) hydrocarbon.

In the metal complex (A) having such a lipophilic group,
The aromatic hydroxycarboxylic acid serving as a ligand preferably has a benzene nucleus or a naphthalene nucleus, and preferably has a carboxyl group and a hydroxyl group coordinated with a metal atom.

On the other hand, the hydrophilic group means a polar atomic group having a strong interaction with water. As the main hydrophilic group, -SO ₃ H, -SO ₃ M.
-COOM, -NR ₃ X, -COOH, -NH ₂ , -CN, -OH, -NHCONH ₂ ,-
X, -NO ₂ and the like (where R is an alkyl group, M is an alkali metal or -NH ₄ ). In the present invention, as the hydrophilic group, a halogen (-X), carboxyl (-COOH), hydroxyl (-OH), nitro (-NO _2), sulfone (-SO ₃ H), sulfonamino (-SO ₃ NH ₄ ) Groups are preferably used.

The monoazo dye (B) having such a hydrophilic group preferably has a benzene nucleus or a naphthalene nucleus in the ligand, and preferably has an O, O′-dioxyazo type structure.

The above-mentioned lipophilic group or hydrophilic group is a monocyclic or polycyclic hydrocarbon group in the structural formula (eg, benzene nucleus, naphthalene nucleus).
It is preferably bound directly to.

When these compounds A and B are individually added to the toner, they both exhibit the same effect as a charge control agent (for example, ordinary negative charging property), but in the present invention, By utilizing the interaction when these compounds A and B are combined, uniform triboelectric charge distribution between toner particles is realized.

Further, in the toner of the present invention, in order to further enhance the combined effect of both substances A and B, it is desirable to satisfy one or more of the following conditions.

It is preferable that the metal atoms in the metal complexes of both substances A and B used in combination are the same in order to make the compatibility of both substances substantially equal to the resin.

The metal atom in the metal complex is preferably Cr in order to enhance the chargeability of the toner.

The particle size of both substances A and B is preferably small in order to improve dispersibility in the resin, and specific numerical values are preferably a volume average particle size (v) of 9.0 μm or less and a number average particle size (n) of 5.0 μm or less. .

The electric resistances of both substances A and B are almost the same, specifically, the ratio of the volume resistivity of substance A / material B is 10 ^-3 to 10 ³ in order to make the triboelectric charge uniform. Is preferred.

As the compound A, specifically, a salicylic acid-based or naphthoic acid-based metal complex represented by the following general formula (I), (II) or (III) is preferably used.

In the general formulas (I) to (III), R ^{1 to} R ^{4 are the} same or different and represent hydrogen or a hydrocarbon group having ₁₀ or less C ₁₀ (such as an alkyl group or an alkenyl group).
However, in the general formula (I), at least ^one of R ^{1 to} R ⁴ represents the above hydrocarbon group.

a, b: There may be a C _{4 to} C ₉ hydrocarbon group (such as an alkyl group), a benzene ring, or a cyclohexene ring.

However, in the formula (II), the hydrocarbon group or the like is present in either a or b, and in the formula (III), a
The hydrocarbon group or the like is present in either one of b or b and either c or d.

X ⁺ (counterion): H ⁺ , K ⁺ , Na ⁺ , NH ₄ ⁺ , Li ⁺ etc.

Me: Cr, Ni, Co, Cu, Zn, etc.

In the salicylic acid or naphthoic acid type metal complex represented by the general formulas (I) to (III), R ¹ , R ² , R ³ and R ⁴
As the alkyl group, a group having 5 or less carbon atoms is easily introduced, and a tert-butyl group, a tert-amyl group or an alkyl group having a smaller number of carbon atoms is preferably used. In the present invention, 3,5 ditersia butyl-
A salicylic acid complex compound and a mono-tertiary butylsalicylic acid chromium complex compound are particularly preferably used.

As shown in the above general formula, in the metal complex compound A, the ligands bonded to the metal atom may not be the same. In this case, at least one of these ligands may be a ligand of an aromatic hydroxycarboxylic acid having a lipophilic group.

As the metal complex compound A, more specifically, a complex compound having the following structure is particularly preferably used.

On the other hand, as the metal complex salt type monoazo dye B having a hydrophilic group, a metal complex salt type monoazo dye known as a charge control agent for negative toner can be appropriately used.

As the monoazo dye, a metal complex salt type monoazo dye having a coupling product of a phenol or naphthol derivative as a ligand, which has the following structural formula (IV) or (V), is preferably used.

As the metal complex compound B, more specifically, a complex compound having the following structure is particularly preferably used.

The ratio of the amount of the above substances A and B added to the binder resin is A
Substance / B substance = 1/10 to 10.0 is preferable, substance A / B substance = 1 /
3 to 3.0 is more preferable.

Addition amount of substances A and B is 0 for each 100 parts of binder resin.
1 to 10.0 parts is preferable, and 0.5 to 4.0 parts is more preferable.

When the toner of the present invention is a magnetic toner, the magnetic powder to be contained in the toner is a metal such as Fe, Ni, Co, Mn,
Alternatively, a powder of a magnetizable material of an oxide or alloy of these metals, preferably having an average particle size of 1 μm or less, is used. The content of the magnetic material is 30 to 100 with respect to 100 parts of the binder resin.
However, 50 to 70 parts are preferred.

In the present invention, examples of the binder resin include homopolymers of styrene such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene, and substitution products thereof; styrene-p.
-Chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-
Vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer Polymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, Styrene-based copolymers such as styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, polychlorination Vinyl, polyvinyl acetate, polyethylene , Polypropylene, silicone resin, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, rosin, modified rosin,
Terpene resin, phenol resin, xylene resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc. may be used alone or in combination.

The toner of the present invention is generally manufactured as follows.

The binder resin and the charge control agents A and B (in some cases, magnetic material, dyes and pigments as colorants, etc.) are uniformly dispersed with a mixer such as a Henschel mixer.

The dispersion obtained above is melt-kneaded by a kneader, an extruder, a roll mill, or the like.

The kneaded product is roughly pulverized by a cutter mill, a hammer mill or the like, and then finely pulverized by a jet mill or the like.

The finely pulverized product is subjected to zigzag classification or the like to have a uniform particle size distribution and classified to obtain the toner of the present invention.

If necessary, in addition to the silicic acid fine powder, an external additive such as a fluorine resin fine powder or a metal oxide may be added to the classified product obtained above and dispersed with a Henschel mixer or the like.

In addition, as a method for producing the toner of the present invention, a polymerization method, a capsule method or the like can be used.

The basic configuration and features of the present invention have been described above. The method of the present invention will be specifically described below based on Examples. However, this does not limit the embodiments of the present invention in any way. The numbers of parts in the examples are parts by weight.

[Example 1] Styrene-acrylic resin 100 parts (trade name Hymer SBM700 manufactured by Sanyo Chemical Co., Ltd.) Magnetite fine powder 60 parts (trade name EPT-1000 manufactured by Toda Kogyo Co., Ltd.) Charge control agent A 2.0 parts (structural formula A-1, v = 6.0 μm, n = 3.2 μm,
Volume resistivity R = 10 ⁹ Ω · cm) Charge control agent B 1.0 part (structural formula B-2, v = 5.6 μm, n = 4.0 μm,
R = 10 ¹⁰ Ω · cm) (v: volume average diameter, n: number average diameter) The above materials are melt-kneaded in a roll mill, cooled, finely pulverized in a jet mill, and further classified to obtain a negative average particle diameter of 9 μm. A chargeable classified product was obtained.

Next, silane coupling was applied to 20 parts of hexamethylene disilazane (HMDS) on fine powder of silica, Aerosil # 200 (manufactured by Nippon Aerosil Co., Ltd.). About 190m ² / g),
Dimethyl silicone oil KF-96100cs is added to 100 parts of this processed product.
(Shin-Etsu Chemical Co., Ltd.) 10 parts diluted with a solvent was again treated, dried and heated at 250 ° C to obtain negatively charged silicic acid fine powder further treated with dimethyl silicone oil. External addition of 0.4 parts to 100 parts of the toner classified product gave a negatively chargeable magnetic toner (that is, a negatively chargeable developer). The hydrophobicity of this treated silicic acid fine powder was 98%. This magnetic toner was developed using a commercially available LBP-CX (manufactured by Canon) that uses an OPC photosensitive drum, and the drum charge amount is -700V, V _DC 500V, developing bias V _PP 1600V, frequency 18
When an image output test was carried out by the reversal development method with a drum-sleeve distance of 270 μ at 0 Hz, a good image was obtained. The image density is 1.31 at 500 sheets and 1.3 at 1000 sheets.
9, a high image density was obtained.

Furthermore, when a durability test was performed under low temperature and low humidity and high temperature and high humidity, there were no image defects such as filming, toner fusion, drum scratches, image deletion, and white spots, even after 5000 sheets were durable.

When the surface of the photosensitive drum was observed, no image fog was found.

[Example 2] Styrene resin 100 parts (Brand name Pikora Stick D-125 manufactured by Hercules Co., Ltd.) Magnetite fine powder 60 parts (same as Example 1) Charge control agent A 1.0 part (Structural formula A-2, v = 6.0) μm, n = 3.4 μm, R
= 10 ⁹ Ω · cm) Charge control agent B 3.0 parts (structural formula B-1, v = 6.5 μm, n = 4.0 μm, R
= ¹⁰ 10 Ω · cm) was melt-kneaded with the material in a roll mill, milling was performed the steps of classifying to obtain a classified product having an average particle diameter of 9 .mu.m.

In the same manner as in Example 1, 100 parts of this classified product was subjected to silane coupling treatment as an external additive, and 0.4 part of silicic acid fine powder treated with silicone oil was externally added to obtain a magnetic toner. When this magnetic toner was subjected to an image forming test in the same manner as in Example 1, no image defect was observed and good results were obtained. The image density was 1.29 at 500 sheets and 1.31 at 1000 sheets, which was a high image density.

When the surface of the photosensitive drum was observed, no image fog was found.

Comparative Example 1 In the same manner as in Example 1, except that only 3.0 parts of the charge control agent A (structural formula A-1) was added instead of the charge control agents A and B (combined use) of Example 1, A magnetic toner was created.
When this toner was evaluated in the same manner as in Example 1, no image defects such as image deletion were observed, but the image density was 1.04 at 500 sheets and 1.10 at 1000 sheets, and the developer of Example 1 was used. It was about 0.3 lower than that in the case where it was present. Also, image fogging on the photosensitive drum increased under low temperature and low humidity conditions.

Comparative Example 2 In the same manner as in Example 2 except that only 4.0 parts of the charge control agent B (structural formula B-2) was used in place of the charge control agents A and B (combination) of Example 2, A magnetic toner was created.

When this toner was used and evaluated in the same manner as in Example 1, no image defects were observed, but the image density was 1.06 at 500 sheets and 1.10 at 1000 sheets. In addition, image fog also increased.

Furthermore, according to the progress of the durability test under high temperature and high humidity,
The image line was thin.

[Comparative Example 3] The same test as in Example 1 was carried out by using 100 parts of the classified product used in Example 1 and externally adding 0.4 part of silicic acid fine particles only similarly subjected to the silane coupling treatment. When I went, the image deletion occurred at about 2500 sheets under high temperature and high humidity,
Also, under low temperature and low humidity, toner fusion occurred from about 3,500 sheets to the drum surface.

〔The invention's effect〕

As described above, according to the present invention, the same developer contains two types of charge control agents that behave differently with respect to triboelectric charge, and after the silane coupling, a silicone oil treatment is applied to the fine silica powder. By dispersing the additive, a developer exhibiting strong and uniform triboelectrification is provided.

The property of obtaining a strong negative charge is effective when the peripheral effect becomes dominant during development, such as digital development, and is particularly effective for the magnetic one-component toner in which the toner charge tends to be unstable.

Claims (1)

[Claims] 1. A metal complex salt type monoazo dye having a hydrophilic group and 100 parts by weight of a binder resin, magnetic powder, 0.1 to 10 parts by weight of a metal complex compound (A) of an aromatic hydroxycarboxylic acid having a lipophilic group, and a hydrophilic group. (B) 0.1 to 10 parts by weight of the metal complex compound (A) and the metal complex salt type monoazo dye (B) in a weight ratio of 1:10 to 10: 1. A developer for developing a digital latent image, comprising: a magnetic toner for electrophotography; and a negatively chargeable silicic acid fine powder which has been treated with hexamethyldisilazane and then treated with silicone oil.