JPS62279349A - Positively electrifiable toner for developing electrostatic charge image and its production - Google Patents

Abstract

PURPOSE:To stabilize triboelectrification quantity and to maintain its distribution sharp and uniform by incorporating diorgano-tin borate to be produced at the time of melt kneading from diorgano-tin oxide and boric acid and a binder resin having an acid value of 0.01-50. CONSTITUTION:The binder resin to be used for the toner having an acid value of 0.01-50, preferably, 0.05-20, contains diorgano-tin borate produced from diorgano-tin oxide and boric acid, thus permitting triboelectrifiability to be remarkably enhanced, and variation of triboelectrification quantity due to circumstantial conditions to be greatly suppressed by using a combination of said resin and said borate. The toner is prepared by melt kneading at least said resin and diorgano-tin oxide and boric acid, pulverizing and classifying them.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention The present invention relates to a toner used as a developer for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, and the like. More specifically, in a direct or indirect electrophotographic development method, a high quality image is produced by uniformly and strongly positively charging a negative electrostatic charge image or by visualizing a positive electrostatic charge image by reversal development. The present invention relates to a chargeable toner and a method for producing the same.

Conventionally, as an electrophotographic method, U.S. Patent No. 2,297,69
Specification No. 1, Japanese Patent Publication No. 42-23910 (U.S. Patent No. 3,666.363), Japanese Patent Publication No. 43-247
Publication No. 48 (U.S. Patent No. 4,071,361)
Many methods are known, such as, but in general, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then the latent image is transferred to a developing powder (hereinafter referred to as a torch). ), and after transferring the toner image to a transfer material such as paper as necessary, it is fixed by heat, pressure, a pressurized heat constant roller, solvent vapor, etc. to obtain a copy. In addition, if there is a step of transferring a toner image, usually
A step is provided to remove residual toner on the photoreceptor.

Development methods for visualizing electrical latent images using toner include, for example, the magnetic brush method described in U.S. Pat. No. 2,874,063, and the magnetic brush method described in U.S. Pat. No. 2,618,552. Cascade development method and 2.221. ．．
The powder cloud method described in US Pat. No. 776, and the method using conductive magnetic toner described in US Pat. No. 3,909,258 are known.

As toners applied to these 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 containing magnetic particles such as magnetite is used. In the case of a system using a so-called two-component developer, the toner is usually mixed with carrier particles such as glass beads and iron powder.

Positive charge control agents used in such dry developing toners generally include, for example, quaternary ammonium compounds and organic dyes, particularly basic dyes and their salts, and nigrosine base and nigrosine are often used as positive charge control agents. It is used as. These are usually added to a thermoplastic resin, heated and melted and dispersed, and then finely ground to adjust the particle size to an appropriate particle size as necessary before use.

However, these charge control agents tend to deteriorate charge controllability due to mechanical shock, friction, changes in temperature and humidity conditions, and the like.

Therefore, when a toner containing these as a charge control agent is used for development in a copying machine, the toner may deteriorate during durability as the number of copies increases.

Furthermore, since it is extremely difficult to uniformly disperse these charge control agents in a thermoplastic resin, there is a problem in that there is a difference in the amount of frictional charge between toner particles obtained by crushing them. There is. For this reason, various methods have been used to achieve more uniform dispersion. For example, basic nigrosine base is used by forming salts with higher fatty acids in order to improve compatibility with thermoplastic resins, but unreacted fatty acids or salt dispersion products often remain on the toner surface. When exposed, it contaminates the carrier or toner carrier, causing a decrease in toner fluidity, fogging, and a decrease in image density. Alternatively, in order to improve the dispersion of these charge control agents into the resin, a method of mechanically pulverizing and mixing the charge control agent powder and resin powder in advance and then hot-melting and kneading has been adopted. In reality, poor dispersion cannot be avoided, and charge uniformity sufficient for practical use has not yet been obtained.

Furthermore, in recent years, as the demand for improved image quality has increased for devices such as electrophotographic printers in which image signals are digital signals, it has become necessary to uniformly impart a sufficient amount of charge to each toner particle.

That is, when the image signal is a digital signal, the latent image is formed by a collection of dots with a constant potential, and solid areas, halftone areas, and light areas are each expressed by changing the density of the dots. Therefore, if any part is binary, it will basically be formed from an electrostatic latent image of approximately the same potential.

Furthermore, recently there has been a growing demand for improved image quality, and it has become necessary to improve gradation reproducibility by using a three-value or four-value multi-value dither method instead of the black-and-white binary dither method described above. This multi-level dithering method is useful when removing false contours that tend to occur in highlight areas, or when simultaneously reproducing an image containing a mixture of halftones and line images. This technology is also essential when reducing the size and improving resolution.

The concept of dither matrix in multilevel dither method is explained first.
This will be explained with reference to FIGS. (a) and (b). Figure 1 (
a) is a 2×2 ternary dither matrix, which includes areas Sl, S2 . S3 represents three density levels of white, gray, and black, respectively. Also, Figure 1(b) is 2×2
It is a four-valued dither matrix with areas Sl, S2 .
S3. S4 represents four density levels of white, light gray, dark gray, and black, respectively. The dot size is, for example, 16 dots/mm.

° Figure 2 (a), (b) and Figure 3 (a), (b)
The exposure intensity distributions shown in Figure 2 (a) and Figure 3 (a) when performing ternary recording in an optical scanning type electrophotographic printer are as follows.
and the potential distribution of the electrostatic latent image corresponding to it (Fig. 2(b)),
This is a representation of FIG. 3(b). The broken lines in FIGS. 2(a) and 3(a) represent the signal output that outputs the optical beam for forming a multivalued latent image.
a) is achieved by brightness modulation controlling the laser output as shown in Figure 1 (
In this method, a gray level corresponding to 82 (hereinafter referred to as M level) and a black level corresponding to 83 (hereinafter referred to as H level) are obtained. For example, the M level can be obtained with a laser output that is 1/2 that of the H level. Figure 3(a)
This method obtains the M level and H level by pulse width modulation that controls the laser output time.

This can be obtained, for example, by setting the pulse width of the M level to 1/2 that of the H level. Figure 2 (a) and Figure 3 (
The potential distribution of a latent image created by a light beam having the exposure intensity distribution shown in a) is as shown in FIGS. 2(b) and 3(b). The latent image contrast of the level tends to be smaller than that of the H level due to a decrease in the MTF of the latent image. Therefore, the image density of this M level becomes almost the same gray as the image density after development of the M level shown in FIG. 2(b) by brightness modulation.

Figure 4 shows the development characteristics (Vs-
2(b) and 3(b).
) To reproduce the M level and H level latent images (respective potential contrasts are represented by Vs-Dp characteristic (slope) is large (
(indicated by the solid line ■ in the figure) is required. However, when conventional toners or developers for developing analog latent images are used, they often tend to exhibit development characteristics as shown by the solid line (3), which causes various problems. Further, when developing a latent image expressed by the density of digital dots, more precise control of this Vs-Dp convex curve is required than in the case of a conventional analog latent image. One is that in order to develop a digital latent image, it is necessary to make the slope (gamma) of the Vs-Dp convex curve larger than before, and it is also necessary to control this slope so that it does not fluctuate. The non-uniformity of charge generated in toners using conventional charge control agents becomes an obstacle to increasing the slope of the Vs-Dp convex curve, and tends to cause fluctuations. If the slope of the Vs-Dp convex curve is small, H level dots will not be reproduced at a sufficiently high density. Also, the density difference between the H level and the M level cannot be reproduced sufficiently, or the potential at the edge of the dot is lower than that at the center, as shown in Figure 21 and Figure 3. Problems such as poor image sharpness may occur, resulting in a defective image with low image density, lack of sharpness, and low resolution.In addition, this non-uniformity of charge can cause problems such as poor image sharpness. Alternatively, fluctuations in the usage environment may cause fluctuations in the Vs-Dp convex curve, resulting in the above-mentioned problems.

In addition, oPC photoreceptors have recently been made more durable, and positively chargeable toners are being applied to machines that are faster than conventional ones. In this case, a positively chargeable toner or a developer containing the same is required, which has high durability and can withstand a larger number of copies than conventional ones, not only for developing digital latent images but also for developing analog latent images. Ru.

Image quality such as ground blur, reverse fog, and roughness tends to deteriorate in direct proportion to an increase in process speed, and this is particularly noticeable in reverse fog. This development is thought to be due to the fact that as the process speed increases, the opportunities for rubbing between the toner and the toner carrier become smaller and shorter, making it impossible for the toner to obtain sufficient and uniform charging. .

Furthermore, in high-end machines, a method that utilizes static electricity is often used in the step of separating the drum and paper after transferring the image formed on the photoreceptor drum onto transfer paper. In this case, a new process (post charging) is added in which the toner is uniformly charged with the same sign as the developer before the toner is transferred from the photosensitive drum onto the paper. In such an image forming process, if toner is present as fog on the drum,
In the conventional image forming process, things that were not transferred onto the paper are transferred onto the paper due to the addition of a new charging process, which appears as fog in the final image. It is necessary to control the amount of frictional charge more sharply than with conventional toners, and it is currently extremely difficult to use conventional toners as they are in copying machines that have a post-charging process.

The object of the present invention is to stabilize the amount of triboelectric charge between toner particles, between toner and carrier, or between toner and a toner carrier such as a sleeve in the case of -component development, and to have a sharp triboelectricity distribution. An object of the present invention is to provide a developer containing a positively charged toner which is uniform and whose charge amount can be controlled to suit the developing system used.

Another objective is to create a toner that allows for development that is faithful to the digital latent image, that is, a toner that has a thick slope of the Vs-Dp curve during development (it is possible to increase the density difference between dots, An object of the present invention is to provide a developer containing a toner that reproduces sharp edges.

Still another object is to provide a developer containing a toner that maintains its initial characteristics even when the toner is used continuously over a long period of time, and does not exhibit fluctuations in the Vs-Dp curve.

Still another object is to provide a developer containing toner that causes less fog and reversal fog even in an image forming process including post-charging.

Still another object is to provide a developer containing a toner that reproduces stable images that are not affected by changes in temperature or tautotropy.

Still another object is to provide a developer containing a toner with excellent storage stability that maintains its initial characteristics even during long-term storage.

Yet another object is to provide a developer containing bright colored toners.

That is, the feature of the present invention is that the acid value is 0.01.
to 50, preferably 0.05 to 20, in which the toner contains diorganotin borate produced from diorganotin oxide and boric acid in a binder resin.

The present inventors have found that when a resin with an acid value of 0.01 to 50 is used in combination with diorganotin oxide and boric acid, triboelectric charging ability is significantly improved, and fluctuations in triboelectric charging I due to environmental changes are significantly reduced. The present invention was achieved by discovering the following.

Although the combination of diorganotin oxide and boric acid has a sufficient effect as a charge control agent, in the present invention, the effect of combining it with an acid resin having an acid value of 0.01 to 50 is as follows.
Furthermore, the aim is to control the amount of triboelectric charge with high precision. If the acid value of the resin used in the present invention is less than 0.01, there will be no effect, and if it is more than 50, the reaction between the diorganotin oxide and the acid in the resin will occur violently during melt-kneading, resulting in a loss of charge controllability. Therefore, the acid value of the resin is 0.01~
50 is preferable, and 0.05-20 is more preferable.

The special effect of the combination of the present invention is that diorganotin porate is formed by the reaction of diorganotin oxide and boric acid, and some of the acid groups in the resin and diorganotin oxide undergo a crosslinking reaction. It is assumed that. Therefore,
One of the effects of the present invention is that the combination of the present invention has significantly superior toner fixing properties and offset properties.

Diorganotin oxides that can be used in the present invention include:
Although there are no particular restrictions, any organo group can be used as long as it does not significantly reduce the charge density of tin. Examples of preferred diorganotin oxides include the following.

Dialkyltin oxides such as dibutyltin oxide, dioctyltin oxide, didodecyltin oxide, dicycloalkyltin oxides such as dicyclohexyltin oxide, dicyclopentyltin oxide, di(p-
diaryltin oxide such as butylphenyltin oxide, di(p-dimethylaminophenyl)tin oxide, di(p-methoxyphenyl)tin oxide, dialkyl such as dibenzyltin oxide, diaryltin oxide, p-methylbenzyltin oxide, etc. Examples include tin oxide.

Further, the resin used in the present invention is produced by synthesizing a polymer from monomers having carboxyl groups by polymerization or copolymerization, or by introducing the carboxyl group into the polymer by reaction.

Examples of the above-mentioned monomers having a carboxyl group include acrylic acid and its derivatives such as acrylic acid, methacrylic acid, α-ethyl acrylic acid, crotonic acid, and isocrotonic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid. unsaturated dicarboxylic acids and their derivatives, and styrene derivatives such as carboxystyrene, which can be used by copolymerizing with other known monomers. Among these, derivatives of unsaturated dicarboxylic acids such as maleic acid hafester are preferred.

As for the proportion of the monomer having a carboxyl group contained in the polymer, a range of 0.01 to 30% by weight gives good results, and a range of 0.05 to 20% by weight is particularly preferred.

Examples of comonomers copolymerizable with the above monomers include styrene, α-methylstyrene, vinylnaphthalene, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, Substituted monocarboxylic acids having double bonds such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylamide, etc.; for example, butyl maleate,
Diester derivatives of dicarboxylic acids having double bonds such as dimethyl maleate; vinyl esters such as vinyl acetate, vinyl benzoate, etc.;
Ethylene-based olefins such as ethylene, propylene, butylene, etc.; Vinyl ketones, such as vinyl methyl ketone, vinyl hexyl ketone, etc.; Vinyl ethers, such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, etc.; , divinylbenzene, divinylnaphthalene, etc.; carboxylic acid esters having two double bonds, such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, etc.; Divinyl compounds such as divinyl ether, divinyl sulfide, and divinyl sulfone and compounds having three or more vinyl groups can be used alone or as a mixture.

Note that the resin having an acid value may be crosslinked.

Furthermore, resins having the above-mentioned functional groups in the main chain or at the end thereof can also be used in the present invention, such as polyester resins.

Note that it is also possible to use a resin with an acid value mixed with a resin without an acid value, and the mixing ratio varies depending on the acid value value and molecular weight, etc., but is generally 1:1 to 1:10. Preferably, they are used in proportions.

Examples of resins having no acid value include monopolymers of styrene and its substituted products such as polystyrene and polyvinyltoluene, such as styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers, Styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-methacrylate ethyl acid copolymer, styrene-butyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, Styrenic copolymers such as styrene-isoprene copolymers, silicone resins, and the like can be used alone or in combination. The above-mentioned resin having no acid value may be crosslinked.

Colorants used in the present invention include carbon black, lamp black, iron black, ultramarine blue, aniline blue, phthalocyanine blue, phthalocyanine green, and Hansa Yellow 610-Damine 6G.

Any conventionally known dyes and pigments such as lake, calco oil blue, chrome yellow, quinacridone, pendizine yellow, rose bengal, triallylmethane dyes, monoazo dyes, disazo dyes and pigments can be used alone or in combination.

Further, in order to further improve fixing properties, the following can be used in combination.

Polyolefins (low molecular weight polyethylene, low molecular weight polypropylene, oxidized polyethylene, etc.), epoxy resins,
Polyester resin, styrene-butadiene copolymer (monomer ratio 5-3095-70), olefin copolymer (
Ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer,
Ethylene-methacrylic acid ester copolymer, ethylene-
(vinyl acetate copolymer, ionomer resin), polyvinylpyrrolidone, methyl vinyl ether-maleic anhydride copolymer, maleic acid-modified phenol resin, phenol-modified terpene resin, paraffin wax, microcrystalline wax, etc.

Further, when the toner of the present invention is used as a two-component developer, it is used in combination with a carrier powder.

All known carriers can be used in the present invention, such as magnetic powders such as iron powder, ferrite powder, and nickel powder, glass beads, etc., and carriers whose surfaces have been treated with resin, etc. Things can be given.

Furthermore, the toner of the present invention can further contain a magnetic material and be used as a magnetic toner. In this case, the magnetic material also serves as a coloring agent. The magnetic materials contained in the magnetic toner of the present invention include iron oxides such as magnetite, hematite, and ferrite; metals such as iron, cobalt, and nickel; and aluminum, cobalt, copper, lead, magnesium, tin, and other metals such as iron, cobalt, and nickel. Zinc, antimony, beryllium,
Examples include alloys of metals such as bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium, and mixtures thereof.

These ferromagnetic materials preferably have an average particle size of about 0.1 to 2 μm, and are contained in the toner in an amount of about 20 to 200 parts by weight per 100 parts of the resin component, particularly preferably in an amount of about 20 to 200 parts by weight per 100 parts of the resin component. The amount is 40 to 150 parts by weight.

Further, it can be used in combination with conventionally known charge control agents as long as it does not adversely affect the developer of the present invention.

Further, better results can be obtained with the developer of the present invention when additives are mixed therein as required. Examples of additives include lubricants such as Teflon and zinc stearate, abrasives such as cerium oxide and silicon carbide, flow agents such as colloidal silica and aluminum oxide, anti-caking agents, and carbon black and tin oxide. There are also conductivity imparting agents such as, fixing aids such as low molecular weight polyethylene, and anti-offset agents. Further, a small amount of white fine particles of opposite polarity can be used as a developability improver.

To prepare the toner for developing an electrostatic image according to the present invention, the charge control agent according to the present invention is added to a vinyl or non-vinyl thermoplastic resin, a pigment or dye as a coloring agent, and a magnetic material as necessary. The ingredients are thoroughly mixed using a ball mill or other mixer, and then kneaded using a heat kneader such as a heated roll, niegu, or extruder at a temperature of 80 to 20°C, preferably 100 to 180°C, for 5 minutes to 4 hours, preferably. 1
Pigments or dyes are dispersed or dissolved in the resin by melting, kneading, and kneading for 0 minutes to 2 hours to make the resins compatible with each other, and after cooling and solidifying, the particles are crushed and classified to produce toner with an average particle size of 5 to 20μ. can be obtained.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but these are not intended to limit the present invention in any way. All parts in the following formulations are parts by weight.

Example 1 The above materials were mixed in a blender (after mixing, kneaded for about 30 minutes with two rolls heated to 150°C. The kneaded material was left to cool naturally, coarsely pulverized with a cutter mill, and then mixed with a jet stream. It was pulverized using a pulverizer and further classified using an air classifier to obtain a black fine powder (to be used as a toner) with a number average particle size of 10 μm.The obtained toner was analyzed and found to be dibutyltin phorate. was confirmed to be generated.

Next, 0.5 part of positively charged hydrophobic solica was mixed with the fine powder using a sample mill to prepare a -component magnetic toner.

Images of this toner were obtained using an electrophotographic printer using an amorphous silicon photoreceptor and evaluated.

FIG. 5 shows an embodiment of a printer to which the developer of the present invention can be applied. The electrical signal input to the laser modulation unit l is output as a modulated laser beam, and is sent to the scanner.
The longitudinal direction of the photosensitive drum 4 is scanned by the mirror 2 and the f/θ lens 3. The photosensitive drum 4 rotates in the direction of the arrow, making it possible to scan the laser beam two-dimensionally.

As a photoreceptor, amorphous silicon, selenium, CdS
, an organic photoreceptor, etc. are used, and are sensitized to have sensitivity to the wavelength (780 nm to 800 nm) of a semiconductor laser, for example. In this embodiment, an amorphous silicon photoreceptor is used as such a photoreceptor, and after leveling the potential on the surface of the photoreceptor with an AC static eliminator 5, it is charged to 380V with a charger 6. Thereafter, laser beam exposure is performed to form a dot latent image on the photoreceptor by an image scanning method using a ternary dither method. The three M levels are formed by pulse width modulation of laser light as shown in FIG. 3(a). The latent image potential was 250V at H level and 120V at M level.

Such a dot latent image was reversely developed by a one-component insulating magnetic toner developer 9 (or 11) containing a developer containing the above-mentioned toner.

At this time, a developing bias of 280 V was applied as a DC component.

The thus developed image was then transferred onto the transfer paper 12 by the transfer charger 11 and fixed onto the transfer paper 12 by the fixing device 13. Further, toner remaining on the photosensitive drum 4 without being transferred is collected by a cleaner 14. The image thus formed on the transfer paper is H level 145, M
It showed a level of 0.65, the image density in solid areas was sufficiently high, the dots were sharp, and the photographic image, which serves as a guide for reproducing halftones, was also clearly reproduced. Also, after copying 100,000 sheets repeatedly, the H level fluctuation was ±0.0.
7 or less, the variation of M level is within ±0.15, and Vs
- No significant change was required in the Dp characteristics. moreover,
When the environmental conditions were set to 35° C., 185%, and 15° C., 10%, good images were obtained in both cases, similar to those at room temperature, and no major changes were required even after repeated use of 100,000 sheets.

This developer was stored for half a year, but its initial characteristics did not change significantly.

Further, fog, reverse fog, and offset did not pose any problems throughout the durability test.

Example 2 Black fine powder was obtained from the above materials in the same manner as in Example 1,
Next, 0.4 part of silica was mixed with the fine powder using a sample mill to prepare a -component magnetic toner.

Images were obtained and evaluated in the same manner as in Example 1, and as in Example 1, good results were obtained.

Example 3 A sepia colored fine powder was obtained from the above materials in the same manner as in Example 1. Next, 0.5 part of silica was mixed with the fine powder using a sample mill to prepare a -component magnetic toner.

Images were obtained and evaluated in the same manner as in Example 1. The resulting sepia image showed 1.38 at the H level and 0.62 at the M level, and the image density in the solid area was sufficiently high and the dots were sharp, making it a photographic image that can be used as a guide for halftone reproduction. was also beautifully reproduced. Although 100,000 copies were repeatedly made, the variation in the H level was within ±0.07, the variation in the M level was within ±0.15, and no practical change was observed in the vS-Dp characteristics. Furthermore, the environmental conditions were changed to 35°C18
5% and 15°C and 110%, good sepia images were obtained in both cases at room temperature and humidity, and no change was observed in practical use even after 100,000 sheets were used (repeated use). No increase in reverse fog was observed throughout.

Example 4 The above materials were thoroughly mixed in a blender and then kneaded with two rolls heated to 150°C. After the kneaded material was left to cool naturally, it was roughly pulverized with a cutter mill, then pulverized with a pulverizer using a jet stream, and further classified using an air classifier to obtain a fine powder with a particle size of 5 to 20 μm ( 0.4 wt % of the positively chargeable silica fine powder used in Example 1 was externally added to this fine powder.

A developer was prepared by mixing 5 parts of the externally added fine powder with 100 parts of iron powder carrier having an average particle size of 50 to 80 microns.

Next, by a conventionally known electrophotographic method,
A negative electrostatic image was formed, and this was powder-developed using the above-mentioned developer using a magnetic brush method to create a toner image, which was transferred to plain paper and heat-fixed. The resulting transferred image has a density of 1.3
2, which was sufficiently high, and there was no fogging at all, and a good image with high resolution was obtained without toner scattering around the image.

Also, during durability, the above-mentioned filming phenomenon related to toner on the photoreceptor was not observed at all, and no problems were found in the cleaning process.Also, at this time, there were no troubles in the heat roller fixing process. At the end of the durability test of 1,000 sheets, the fixing device was observed, and there were no scratches or damage to the rollers, and there was almost no staining due to offset toner, so there was no practical problem at all.

In addition, when the environmental condition was set to 356C/85%, the image density was 1,19 room temperature, a value with almost no change,
A clear image was obtained without fogging or scattering.

Next, a transferred image was obtained at a low temperature and low humidity of 15° C. and 110%. The image density was as high as 1.24, solid black was developed and transferred extremely smoothly, and the image was excellent with no splatters or hollow spots.

Example 5 A toner was obtained in the same manner as in Example 4, except that a styrene/butyl methacrylate/n-butyl maleate hafester copolymer with an acid value of 0.5 was used, and 3 parts of dibutyltin oxide was used, and an image was formed. I put it out.

A good fixed image with a slightly higher image density than that of Example 4 was obtained.

Comparative Example 1 Dibutyltin oxide [(C4H
A developer was obtained in the same manner as in Example 4, except that 3 parts of 2S n Ol were used and no boric acid was added. Using this toner, an image was formed and evaluated in the same manner as in Example 4. At the initial stage of development, an image with a density of 1.28 was obtained, but
After 10,000 copies were repeated, the image density had already decreased to 0.61, and fog was also noticeable.

Example 6 The above materials were thoroughly mixed in a blender and then kneaded with two rolls heated to 150°C. After the kneaded material was left to cool naturally, 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 fine powder with a particle size of 5 to 20μ. Ta.

Next, 0.5 part of silica was mixed with the fine powder using a sample mill to prepare a toner.

Next, 50 g of magnetic particles having a particle size of 50 to 80 μm were mixed with 100 parts of the fine powder to prepare a developer.

This toner was applied to a commercially available copying machine (trade name: PC-22 manufactured by Canon ■) to produce an image.

A bright blue image with an image density of 1.35 was obtained, there was no fogging, and the sharpness of the image was sufficiently satisfactory.

Also, I made 2000 copies repeatedly, but the image quality was 1,
31, there was almost no change, and no decrease in image sharpness was observed. Furthermore, although the copying environment was set to 35° C., 185% and 15° C., 10%, good images were obtained in both cases, as in normal temperature and normal humidity.

[Brief explanation of the drawing]

Figures 1(a) and (b) are diagrams showing the concept of a multivalued dither matrix, and Figures 2(a) and (b) and Figure 3(a) are diagrams showing the concept of a multilevel dither matrix.
) and (b) are characteristic graphs showing the exposure intensity distribution and potential distribution of an electrostatic latent image when performing three-value recording, and FIG. 4 is a graph showing the development characteristics of a multi-valued latent image. FIG. 5 is a diagram schematically showing an example of an electrophotographic printer to which the toner of the present invention is applied. l...... Laser modulation unit, 2...
.....Scanner mirror, 4.....Photosensitive drum, 5.....AC static eliminator, 6..Charger, 9 ......Developer, 11...Transfer charger.

Claims (2)

[Claims] (1) Diorganotin borate generated from diorganotin oxide and boric acid during melt-kneading, and acid value 0.01
A positively chargeable toner for developing an electrostatic image, comprising a binder resin having a molecular weight of 50 to 50. (2) A method for producing a positively chargeable toner for developing an electrostatic image, which comprises melting and kneading at least a binder resin having an acid value of 0.01 to 50, diorganotin oxide, and boric acid, and pulverizing and classifying the same. .