JPH04328757A - Toner for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To improve the moisture resistance and flowability of a toner while maintaining satisfactory electrostatic chargeability by fixing melamine resin on fine silica particles. CONSTITUTION:Fine silica particles are fixed near the surfaces of toner particles contg. at least a resin binder and a colorant and fine melamine resin particles are fixed on the silica particles. The pref. amt. of the silica particles added is 0.01-2.0wt.% basing on the amt. of the toner and that of the melamine resin particles is 0.01-2.0wt.% basing on the amt. of the toner. Since the silanol groups of the silica causing moisture absorption are covered with the melamine resin, the silica does not absorb moisture even in an environment at high humidity and the resulting toner for developing an electrostatic charge image can maintain stable electrostatic chargeability even in any environment.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing electrostatic images used in electrophotography, electrostatic printing, and magnetic recording.

0002

[Prior Art] Conventionally, as an electrophotographic method, US Pat.
, 297,691, Japanese Patent Publication No. 42-23910 (U.S. Patent No. 3,666,363), Japanese Patent Publication No. 43-24748 (U.S. Patent No. 4,071,3)
A number of methods are known, such as No. 61). Such electrophotography generally involves forming an electrical latent image on a photoreceptor by various means using a photoconductive substance, and then developing the latent image using developer powder (hereinafter referred to as toner). After the toner image is transferred to a transfer material such as paper as necessary, it is fixed by heating, pressure, solvent vapor, etc. to obtain a copy. Furthermore, when a process of transferring a toner image is included, a cleaning process is usually provided to remove residual toner on the photoreceptor. Among the above-mentioned developing methods for visualizing electrical latent images using toner, for example,
The magnetic brush method described in U.S. Pat. No. 2,874,063, the cascade development method described in U.S. Pat. No. 2,618,552, and U.S. Pat. No. 2,221,776.
There is a powder cloud method described in the specification of No. Further, as a method using magnetic toner, US Pat. No. 3,909
, 258, a method using dielectric polarization of toner particles, a method of charge transfer by toner disturbance, and JP-A-54-42141 and There is a method of developing a latent image by causing toner particles to fly against it, as disclosed in Japanese Patent Laid-Open No. 55-18656. As toners applied to these various developing methods, fine powders in which dyes and pigments are dispersed in natural or synthetic resins have conventionally been used. For example, particles obtained by dispersing a colorant in a binder resin such as polystyrene and pulverizing the particles to about 1 to 30 μm are used as toner. As the magnetic toner, one further containing magnetic particles such as magnetite is used. In addition, in the case of a system using a so-called two-component developer, these toners are usually mixed with carrier particles such as glass beads and iron powder.

In order to form a visible image of good quality in such a method using a dry developer, it is necessary that the developer has high fluidity, that the toners do not aggregate with each other, and that the toner is uniform. Since it is necessary to have a good chargeability, fine silica particles have conventionally been added and mixed into toner powder. However, since fine silica particles are hydrophilic in their original state, the developer to which they are added will cause aggregation due to moisture in the air, resulting in a decrease in fluidity or, in extreme cases, due to moisture absorption by the silica. There is a problem that charging performance is deteriorated. In contrast, the use of hydrophobically treated silica fine particles has been proposed in JP-A-46-5782, JP-A-48-47345, JP-A-48-47346, and the like. Specifically, hydrophobization treatment involves reacting silica particles with a silane coupling agent to replace the silanol groups on the surface of the silica particles with other organic groups to make them hydrophobic. For example, dimethyldichlorosilane, trimethylalkoxysilane, etc. are used.

0004

[Problem to be Solved by the Invention] However, although these silica particles have been treated to make them hydrophobic, it is difficult to say that the degree of hydrophobization is sufficient, and if they are left in a high humidity environment. However, there is a problem in that the charging ability of the toner decreases due to moisture absorption of the silica. Therefore, an object of the present invention is to provide a new toner that solves the above-mentioned problems. That is, an object of the present invention is to provide a toner for developing electrostatic images that is stable against environmental changes such as high temperature and high humidity, low temperature and low humidity, and can always exhibit good characteristics. In addition, another object of the present invention is to
An object of the present invention is to provide a toner with excellent durability that can provide stable images even when a large number of images are formed over a long period of time in electrophotography including processes such as development, fixing, and cleaning. Furthermore, another object of the present invention is to solve various problems of conventional chargeable toners at the same time, to enable the toner to be uniformly and strongly charged, to visualize the electrostatic charge image, and to prevent fogging and toner dispersion around edges. The objective is to provide toner that provides high quality images without scattering.

[0005]

[Means for Solving the Problems] The above objects are achieved by the present invention as described below. That is, the present invention is characterized in that, in a toner for developing an electrostatic image containing at least a binder resin and a colorant, fine particles made of melamine resin are fixed after fine particles of silica are fixed near the surface of the toner particles. This is a toner for developing electrostatic images.

[0006]

[Operation] In order to simultaneously achieve the above objectives, the present inventor has
As a result of using various additives and carefully examining their composition and performance from various angles, we found that it is an extremely effective method to first fix silica fine powder near the toner surface and then fix melamine resin. They discovered this and completed the present invention. That is, by coating the silica's silanol groups, which cause moisture absorption, with a melamine resin, the silica does not absorb moisture even in a high humidity environment, and the toner for developing electrostatic images of the present invention can be used under any environment. It also becomes possible to have stable charging ability. In addition, the melamine resin used for the coating has excellent moisture resistance, heat resistance, light resistance, abrasion resistance, and electrical properties, and is colorless and transparent, so it can be used in the toner for developing electrostatic images of the present invention. can be used not only for magnetic toners but also for color toners.

[0007]

[Preferred Embodiment] The silica fine powder used in the electrostatic image developing toner of the present invention has a specific surface area due to nitrogen adsorption measured by the BET method of 30 m2/g or more (particularly 50 m2/g or more).
400 m2/g) gives good results. Also, the amount of silica fine powder added to the toner is 10
It is used in an amount of 0.01 to 2.0% by weight, more preferably 0.1 to 1.5% by weight relative to 0% by weight. When the amount of silica fine powder added is less than 0.01% by weight,
The charging of the toner becomes non-uniform, causing so-called charging unevenness. On the other hand, if the amount is more than 2.0% by weight, fine silica powder that is not fully adhered to the toner and becomes free will be present, causing deterioration in fixing performance.

[0008] After the silica fine powder is fixed near the toner surface, the melamine resin to be coated has a primary particle size of 0.03 to 2 μm, preferably 0.05 to 1 μm. gives good results. Melamine resin 1
If the secondary particle size is less than 0.03 μm, the effect of preventing binding between toners cannot be expected. On the other hand, if the primary particle size exceeds 2 μm, the number of particles adhering to the toner decreases, and the effect of preventing the toner particles from bonding with each other decreases, which is not preferable. Further, the amount of the melamine resin added is 0.01 to 2.0% by weight, more preferably 0.1% by weight based on 100% by weight of the toner.
It is preferable to use it within the range of 1.5% by weight. If the amount of melamine resin is less than 0.01% by weight, the toner cannot be made sufficiently hydrophobic;
If the weight percentage is exceeded, excess fine particulate resin powder will be present, resulting in an adverse effect of deterioration of fixing performance. The silica fine particles and melamine resin described above may be fixed near the surface of the toner particles by dry mixing using a Henschel mixer or the like.

Binder resins that can be used in the present invention include, for example, styrenes such as polystyrene, poly-P-chlorostyrene, polyvinyltoluene, styrene-P-chlorostyrene copolymer, and styrene-vinyltoluene copolymer. Homopolymers and copolymers thereof; styrene and acrylic acid, such as styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, and styrene-n-butyl acrylate copolymer; Copolymers with esters; copolymers of styrene and methacrylic esters such as styrene-methyl methacrylate copolymers, styrene-ethyl methacrylate copolymers, styrene-n-butyl methacrylate copolymers; styrene and acrylic esters and methacrylic esters; other styrene-acrylonitrile copolymers, styrene-vinyl methyl ether copolymers, styrene-butadiene copolymers, styrene-vinyl methyl ketone copolymers, styrene- Styrenic copolymers of styrene and other vinyl monomers such as acrylonitrile-indene copolymers and styrene-maleic ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyesters, polyamides, epoxy resins , polyvinyl butyral, polyacrylic acid, phenol resin, aliphatic or alicyclic hydrocarbon resin, petroleum resin, chlorinated paraffin, etc. can be used alone or in combination.

In the toner for developing electrostatic images of the present invention, in order to maintain the chargeability of the toner, if necessary,
A charge control agent can also be used, and conventionally known negative or positive charge control agents can be used. For example, charge control agents known in the art include the following: As the charge control agent for controlling the negative chargeability of the toner, for example, organic metal complexes and chelate compounds are suitable, and monoazo metal complexes, acetylacetone metal complexes, aromatic hydroxycarboxylic acids, and aromatic dicarboxylic acid-based metal complexes are suitable. There is. Other examples include aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids, their metal salts, anhydrides, esters, and phenol derivatives such as bisphenol.

Further, as the charge control agent for controlling the toner to be positively charged, for example, modified products of nigrosine and fatty acid metal salts, tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium, Examples include quaternary ammonium salts such as tetrafluoroborate, onium salts such as phosphonium salts which are analogs thereof, and lake pigments thereof, triphenylmethane dyes and lake pigments thereof. (still,
As lake forming agents, phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid,
Lauric acid, gallic acid, ferricyanide, ferrocyanide, etc. can be used. ) In addition, there are metal salts of higher fatty acids, acetylacetone metal complexes, diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide, and diorganotinborate such as dibutyltinborate, dioctyltinborate, dicyclohexyltinborate, etc. These can be used alone or in combination of two or more. Among these, charge control agents such as nigrosine and quaternary ammonium salts are particularly preferably used.

In addition, in order to improve the mold releasability during fixing with a hot roll, a waxy substance such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, Sasol wax, paraffin wax, etc. is added to the binder resin. 0.0% to 100% by weight.
Adding about 5 to 10% by weight is also one of the preferred embodiments of the present invention.

Furthermore, when the toner for developing electrostatic images of the present invention is used in a two-component developer, it is used in combination with a carrier powder. In this case, the mixing ratio of toner and carrier powder is 0.1 to 50% by weight, preferably 0.5 to 10% by weight, more preferably 3 to 5% by weight as toner concentration.
is within the range of All known carriers can be used at this time, such as magnetic powders such as iron powder, ferrite powder, and nickel powder, glass beads, etc., and fluorine resin on the surface of these. , those treated with vinyl resin, silicone resin, or the like.

Furthermore, the toner for developing electrostatic images of the present invention may contain a magnetic material to form a magnetic toner. In this case, the magnetic material contained also serves as a coloring agent. Magnetic materials included in the toner include magnetite,
Iron oxides such as hematite and ferrite; metals such as iron, cobalt, and nickel, or these metals and aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, and selenium. , alloys with metals such as titanium, tungsten, and vanadium, and mixtures thereof. In addition, these ferromagnetic materials have an average particle size of 0.1 to 2 μm,
Preferably, one with a diameter of about 0.1 to 0.5 μm is used,
The amount to be contained in the toner is about 20 to 200 parts by weight per 100 parts by weight of the resin component, particularly preferably about 40 to 150 parts by weight per 100 parts by weight of the resin component. These ferromagnetic materials have magnetic properties with a coercive force of 20 to 150 Oe, saturation magnetization of 50 to 200 emu/g, and residual magnetization of 2 to 20 e when 10 K Oe is applied.
mu/g is desirable.

[0015] The colorant that can be used in the toner for developing electrostatic images of the present invention includes any suitable pigment or dye. Toner colorants are well known and include, for example, pigments such as carbon black, alinine black, acetylene black, naphthol yellow, Hansa yellow, rhodamine lake, alizarin lake, red iron, phthalocyanine blue, and indanthrene blue. These pigments are used in amounts necessary and sufficient to maintain the optical density of the fixed image. For example, resin 10
0.1 to 20 parts by weight, preferably 2 to 1 parts by weight
Add about 0 parts by weight. Further, dyes are also used for the same purpose. Examples include azo dyes, anthraquinone dyes, xanthene dyes, methine dyes, etc., and the amount added is 0.1 to 20 parts by weight, preferably 0.3 to 3 parts by weight, per 100 parts by weight of the resin. good.

Furthermore, the toner for developing an electrostatic image of the present invention includes:
Additives other than the silica fine particles and melamine resin described above can also be used as necessary. Examples of other additives include lubricants such as Teflon, zinc stearate, and polyvinylidene fluoride, with polyvinylidene fluoride being preferred. Alternatively, abrasives such as cerium oxide, silicon carbide, and strontium titanate are preferred, with strontium titanate being preferred. Alternatively, for example, fluidity imparting agents such as titanium oxide and aluminum oxide, among which hydrophobic ones are particularly preferred. In addition, small amounts of anti-caking agents, such as conductivity imparting agents such as carbon black, zinc oxide, antimony oxide, and tin oxide, or white fine particles and black fine particles of opposite polarity, can also be used as developability improvers. Incidentally, these additives may be fixed near the surface of the toner particles by dry mixing together with the silica fine particles.

To prepare the toner for developing electrostatic images of the present invention, first, a binder resin, a pigment or dye as a coloring agent, a charge control agent, a magnetic substance and other additives as required, etc. are mixed in a Henschel mixer, Pigments and dyes are mixed thoroughly using a mixer such as a ball mill, then melted, kneaded, and kneaded using a heat kneader such as a heated roll, kneader, or extruder to make the resins compatible with each other. , a magnetic material or the like is dispersed or melted, cooled and solidified, and then pulverized and classified to obtain a toner. Next, fine silica particles, melamine resin, and other additives are thoroughly mixed with the toner thus formed using a mixer such as a Henschel mixer to obtain the toner for developing electrostatic images according to the present invention. I can do it.

[0018]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples in any way. Example 1 Styrene-n-butyl methacrylate copolymer 100% by weight magnetite
Chromium complex of 85% by weight acetylacetone
2
Weight% low molecular weight polypropylene

3% by weight of the above materials were premixed using a Henschel mixer, and then melt-kneaded at 130°C using a twin-screw kneading extruder. Next, after cooling this kneaded material, it was roughly pulverized using a cutter mill, then pulverized using a pulverizer using a jet stream, and further classified using an air classifier to obtain a volume average particle size of 8. A black fine powder (toner) of .5 μm was obtained. To 100% by weight of the magnetic toner thus obtained, 0.4% by weight of silica fine particles was dry mixed using a Henschel mixer, and then 0.5% by weight of melamine resin with a primary particle size of 0.3 μm was added. % and dry mixed to obtain the toner for developing electrostatic images of the present invention. This toner is
Canon Co., Ltd. copier NP665 using a Si photoreceptor
As shown in Table 1, the results were evaluated using 0.
5℃, 10%), high temperature and high humidity environment (32℃, 85%)
Maintains high reflective image density from beginning to end under any environment, no fogging, and no toner scattering around the image.
Moreover, good images with high resolution were obtained. Furthermore, the fixing properties were at a level with no problems at all. Regarding fixing properties, under a low temperature and low humidity environment (15°C, 10%),
After leaving the above evaluation machine overnight to allow the evaluation machine and its internal fixing device to become completely accustomed to the low-temperature, low-humidity environment, 200 copies were made in succession, and the 200th copy was made. It was used to evaluate fixability. In other words, to evaluate the fixability, the image on the 200th sheet was moved back and forth 10 times with Silbon paper, about 10 times.
Rubbing with a load of 0g, the peeling of the image is measured by the rate of decrease in reflection density (
%) and shown in Table 1.

Example 2 Polyester resin

100% magnetite

85% by weight monoazo iron complex

2% by weight low molecular weight polypropylene
A toner was prepared in the same manner as in Example 1 using 3% by weight or more of the material to obtain an electrostatic image developing toner of the present invention. Image evaluation of the obtained toner was performed in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 An electrostatic image developing toner of the present invention was obtained in the same manner as in Example 1, except that 5% by weight of carbon black was added instead of magnetite. For 8% by weight of this toner, the particle size of particles coated with fluororesin is approximately 80%.
A two-component developer was prepared by mixing 100% by weight of a μm ferrite carrier. Further, only toner was used as a replenisher. Image evaluation of the obtained toner was performed in the same manner as in Example 1, and the results are shown in Table 1.

Example 4 In Example 1, 5% by weight of nigrosine was added instead of the chromium complex of acetylacetone, 0.6% by weight of silica particles, and 0.7% by weight of melamine resin (based on toner). Example 1 except that
In the same manner as above, an electrostatic image developing toner of the present invention was obtained. For image evaluation, use the above-mentioned Canon Co., Ltd. copier N.
When P6650 was modified and evaluated using a machine equipped with a reversal development mechanism, good images could be obtained. The detailed evaluation results are shown in Table 1.

Example 5 The same procedure as in Example 1 was carried out, except that the binder resin was changed to styrene-n-butyl acrylate copolymer, and 2% by weight of nigrosine was used instead of the chromium complex of acetylacetone. An electrostatic image developing toner of the present invention was obtained by the method. For image evaluation,
Performed using a copier NP3825 manufactured by Canon Co., Ltd.
Good results were obtained. The detailed results are shown in Table 1.

Comparative Example 1 A comparative toner was obtained in the same manner as in Example 1 except that fine silica particles were not added. When this toner was evaluated using the same method as in Example 1, as shown in Table 1, the image quality was poor in all environments, and the image density was also low, and uneven charging was observed, especially in low temperature and low humidity environments. done.

Comparative Example 2 A comparative toner was obtained in the same manner as in Example 1 except that 2.5% by weight of silica fine particles were added. The obtained toner contained a large amount of free silica. In addition, the results of image evaluation are shown in Table 1.
As shown in , the image density was low, and in particular, the density reduction rate was 55% in the fixability evaluation.

Comparative Example 3 A comparative toner was obtained in the same manner as in Example 1 except that the melamine resin was not added. In addition, the image evaluation was performed in the same manner as in Example 1, and the results were as shown in Table 1.
In particular, the image density was noticeably low under high temperature and high humidity conditions.

Comparative Example 4 A comparative toner was obtained in the same manner as in Example 1 except that the amount of melamine resin added was 2.5% by weight. Further, when the image was evaluated in the same manner, it was found that a large amount of free fine resin powder was present in the obtained toner, which resulted in poor fixing performance.

[Table 1]
Table 1 Toner evaluation results

[Table 1]
Continuation of Table 1

[0027]

Effects of the Invention As described above, the electrostatic image developing toner of the present invention has significantly improved the problems associated with conventional toners. This is extremely effective in solving the problem of decrease in That is, by fixing a melamine resin having excellent moisture resistance on the silica fine particles, it is possible to improve the moisture resistance and fluidity of the toner while maintaining good chargeability. In other words, the toner for developing an electrostatic image of the present invention achieves uniform chargeability of the toner by adding silica,
On the other hand, the melamine resin improves the fluidity of the toner and further prevents the charging ability from becoming unstable due to environmental changes caused by moisture absorption of the added silica. By achieving such functional separation, the electrostatic image developing toner of the present invention allows stable and high-quality copied images to be obtained under any environment.

Claims (3)

[Claims] 1. A toner for developing an electrostatic image containing at least a binder resin and a colorant, characterized in that silica particles are fixed near the surface of the toner particles, and then fine particles made of a melamine resin are fixed. Toner for developing electrostatic images. Claim 2: The amount of silica fine particles added is 0.01 to 2.
．． The toner for developing an electrostatic image according to claim 1, wherein the content is 0% by weight (based on the toner). 3. The toner for developing electrostatic images according to claim 1, wherein the amount of the fine particles made of melamine resin is 0.01 to 2.0% by weight (based on the toner).