JP3152838B2 - Image forming method - Google Patents

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 an electrostatic image used in electrophotography, electrostatic printing, and magnetic recording, and an image forming method using the toner.
The present invention relates to an image forming method using a system in which untransferred toner remaining on a latent image carrier after transfer is collected by a cleaning process and reused.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic method, US Pat.
As described in 2,297,691 specification, JP-B-42-23910 and JP-B-43-24748, a number of methods are known, but generally, a photoconductive substance is used.
An electric latent image is formed on a photoreceptor by various means, and then the latent image is developed using toner, and if necessary, a toner image is transferred to a transfer material such as paper. It is fixed by steam or the like to obtain a copy. In this step, even after transferring the toner image to the transfer material,
Untransferred toner remains on the photoreceptor in an amount of 10 to 20% by weight. Until now, the untransferred toner has been collected by a cleaning step, discharged out of the system as so-called waste toner, and cannot be reused. Was.

However, in recent years, the demand for printers has increased, and the demand for machines having a large copy volume, that is, high-speed machines has been increasing. In such a high-speed machine, a large amount of waste toner is generated, and when it is processed as waste (waste plastic), there is a possibility of causing environmental pollution. For this reason, recently, a study of reusing the waste toner, that is, a study of reuse of the toner has been widely performed. If the waste toner can be reused, the toner can be effectively used, the space in the apparatus can be simplified, and the machine can be downsized. However, when the waste toner is used again in the developing step, there have been adverse effects such as a decrease in the reflection image density, deterioration of the background fog and reverse fog, and occurrence of toner scattering.

[0004] The characteristics of the toner applied to such a toner reuse system include a developing property, a low-temperature fixing property, an anti-offset property, an anti-blocking property, an anti-filming property, and a pulverizing property, as well as a resistance to mechanical stress. It is also required to have characteristics such as excellent durability and excellent transportability of waste toner to a developing process. Various toners have been proposed to meet these requirements. For example, JP-A-1-214874 discloses a toner using a specific polyester resin containing a fatty acid diol as a binder resin, and JP-A-2-110572 discloses a metal-crosslinked styrene-acryl copolymer. A toner in which the coalescing is used as a binder resin and a large amount of a polyolefin is added has been proposed. However, in any of the inventions, the novelty of the toner composition itself is poor, and rather, a problem such as deterioration of blocking resistance is caused. Probability is high. As described above, the performance required for the toner is often reciprocal to each other, and even when the waste toner is reused,
In recent years, it has been increasingly desired to satisfy these requirements.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to use a toner which has solved the above-mentioned problems and to prevent the generation of waste toner by using a recovery device for recycling the toner.
It is an object of the present invention to provide an image forming method capable of stably supplying a high-quality copy image having an appropriate image density and no fog.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors analyzed conventional toners. As a result, the toner after use had significantly lower powder fluidity than the toner before use. When the fine particle component in the toner is increased, and when the surface of the toner is observed with a scanning electron microscope, the shape of the toner becomes spherical, and inorganic fine particles that can be observed in unused toner are not observed. Turned out to be. Further, when the inorganic element analysis of the toner surface was further performed, it was found that the toner after use had almost the same amount of inorganic oxide as the toner before use. based on the above results,
The inventor believes that the cause of image deterioration due to reuse of waste toner is
It has been found that the toner is crushed and that the inorganic fine particles present on the surface of the toner are embedded in the toner due to the stress applied from the recovery system, thereby deteriorating the fluidity of the toner. Based on these facts, as a result of intensive research, the use of a polyester resin having a specific composition with high toughness as a binder resin for the toner, and furthermore, the above-mentioned inorganic particles having a specific particle size range adhered to the surface of the toner. The inventors have found that the problem can be solved and completed the present invention.

That is, the present invention develops a latent image on a latent image carrier to form a toner image, transfers the formed toner image from the latent image carrier to a transfer material, and transfers the latent image carrier after transfer. Is cleaned to collect the toner on the latent image carrier, and the collected toner is supplied to the developing unit side to be used in the developing process. (A) the following general formula (I)

[0008]

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[In the formula, R ¹ is an alkylene group having 2 to 4 carbon atoms, x and y are positive integers, and the average value of the sum is 2 to 16. The diol represented by], all a polyol
A polyol component containing 80 to 100 mol% relative to the Le component, (ii) the following general formula (II) or (III)

[0010]

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[0011]

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Wherein R ² and R ³ each have 4 to 20 carbon atoms
Is a saturated or unsaturated hydrocarbon group. 1 to 50 mol% with respect to the polyol component (a), and trimellitic acid or the acid anhydride with 10 to 10 mol% with respect to the polyol component (a). A polyester resin obtained by subjecting a polycarboxylic acid component containing 30 mol% to condensation polymerization and having an average particle diameter of 30 nm or more on the surface of the toner.
It is an object of the present invention to provide an image forming method characterized in that inorganic fine particles of less than 00 nm are adhered.

Hereinafter, the present invention will be described in detail. [Toner Binder Resin] As the binder resin of the toner according to the present invention, the above-mentioned polyester resin is used. The polyol component (a) of the polyester resin used in this case contains the diol represented by the general formula (I) as an essential component. Examples of the diol include polyoxypropylene (2.2 mol) -2 , 2-Bis (4-hydroxyphenyl) propane, polyoxyethylene (2 mol) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (6 mol) -2,2
And bisphenol A-based monomers such as -bis (4-hydroxyphenyl) propane and polyoxypropylene (16 mol) -2,2-bis (4-hydroxyphenyl) propane. Other polyol components (a) include ethylene glycol, propylene glycol,
Glycerin, pentaerythritol, trimethylolpropane, hydrogenated bisphenol A, sorbitol, or their etherified polyhydroxyl compounds, ie, polyoxyethylene (10 mol) sorbitol, polyoxyethylene (3 mol) glycerin, polyoxyethylene (4 mol ) Pentaerythritol and the like. The content of the diol represented by the general formula (I) in the polyol component (a) is preferably 80 to 100 mol%.

The polyvalent carboxylic acid component (b) of the polyester resin used in the present invention comprises a divalent carboxylic acid represented by the general formula (II) or (III) or an acid anhydride thereof, and trimellit. An acid or an acid anhydride thereof is contained as an essential component. The content of the divalent carboxylic acid represented by the general formula (II) or (III) or the acid anhydride thereof is 1 to 50% by mol based on the polyol component (a). If the content is outside this range, the image quality desired by the present invention cannot be obtained. The content of trimellitic acid or its acid anhydride is 10 to 30 with respect to the polyol component (a).
Mol%. If the content is outside this range, the image quality desired by the present invention cannot be obtained. Where the general formula (II) or (III)
Examples of the divalent carboxylic acid represented by are n-dodecenyl succinic acid, iso-dodecyl succinic acid, iso-octyl succinic acid, n-octyl succinic acid, n-butyl succinic acid and the like or an acid anhydride thereof.

The polyvalent carboxylic acid component (b) of the polyester resin of the present invention may be phthalic acid, isophthalic acid or terephthalic acid, in addition to the above-mentioned dihydric carboxylic acid or its acid anhydride and trimellitic acid or its acid anhydride. Production of polyester resins such as acids, divalent carboxylic acids such as fumaric acid and maleic acid, and tetravalent carboxylic acids such as pyromellitic acid, and acid anhydrides and lower alkyl (C1-5) esters of these acids. May be used.

The polyester resin used as a binder resin of the toner according to the present invention is usually prepared by mixing a polyol component (a) and a polyvalent carboxylic acid component (b) at 180 to 250 ° C. in an inert gas atmosphere. It can be produced by condensation polymerization at a temperature. At this time, in order to accelerate the reaction, a commonly used esterification catalyst such as zinc oxide, stannous oxide, dibutyltin oxide, dibutyltin dilaurate and the like can be used. The polyester resin used in the present invention preferably has a glass transition temperature of 70 ° C. or higher. In this case, the ground fogging is further suppressed. In the present invention, the glass transition temperature of the resin is D
It is determined according to a standard method using the SC method.

[Other Components in Toner Particles] In addition to the binder resin, a colorant and a charge control agent are blended in the toner particles according to the present invention. Binder resin in toner particles,
The mixing ratio of the colorant and the charge control agent is preferably 99 to 75% by weight of the binder resin, 0.5 to 20% by weight of the colorant, and 0.1 to 5% by weight of the charge control agent.

As the colorant for the toner used in the present invention, carbon black; CI acetoacetate arylamide monoazo yellow pigments such as CI Pigment Yellow 1, 3, 74, 97 and 98; CI Pigment Yellow・ Yellow 1
2,3,13,14,17 acetoacetate arylamide disazo yellow pigments; CI Solver Yellow 19,7
7, 79, yellow dyes such as CI Disperse Yellow 164; CI Pigment Red 48, 49: 1, 53: 1,
Red or red pigments such as 57, 57: 1, 81, 122, and 5; red dyes such as CI Solver Red 49, 52, 58, and 8; CI Pigment Blue 15: 3 Dyes and pigments of copper phthalocyanine and its derivatives, such as CI;
Green pigments such as CI Pigment Green 7 and 36 (Phthalocyanine Green) can be used. These dyes and pigments may be used alone or in combination of two or more.

Further, as the charge control agent for the toner used in the present invention, a chromium-azo complex dye, an iron-azo complex dye, a cobalt-azo complex dye, and chromium / zinc of salicylic acid or a derivative thereof are used for negative toner.・ Aluminum / boron complex or salt compound, chromium / zinc / aluminum / boron complex or salt compound of naphtholic acid or its derivative, chromium / zinc / aluminum / boron complex or salt compound of benzylic acid or its derivative, long chain Alkyl carboxylate, long chain alkyl
Surfactants such as sulfonates; and for positive toners, nigrosine dyes and derivatives thereof, triphenylmethane derivatives, quaternary ammonium salts, quaternary sulfonium salts, quaternary pyridinium salts, guanidine salts, amidine salts, etc. And the like.

The toner according to the present invention includes a magnetic substance such as ferrite, a conductivity modifier, a metal oxide such as tin oxide, silica, alumina, zirconia, titania, and zinc oxide, an extender, and a fibrous substance. And the like, a reinforcing filler, an antioxidant, a release agent and the like may be added as necessary. As the composition of the toner according to the present invention, conventionally known materials other than those described above can be used.

[Inorganic fine particles externally added to toner particles] In the present invention, the average particle size is
Inorganic fine particles of 30 nm or more and less than 100 nm are attached.
The particle size of the inorganic fine particles can be measured by a particle size distribution measuring device using dynamic light scattering, but since it is difficult to dissociate the secondary aggregation of the particles, the photograph is obtained from a photograph obtained by a scanning electron microscope. It is best to determine the particle size. As another index, the BET specific surface area of the inorganic fine particles is 20 to 80 m ^2.
/ G corresponds to the above particle diameter. In the present invention,
When the average particle diameter of the inorganic fine particles is smaller than 30 nm, the inorganic fine particles are easily embedded in the toner, so that satisfactory stability over time of the non-magnetic one-component toner cannot be obtained.
When a toner having a particle diameter of 100 nm or more is adhered to the toner, proper fluidity cannot be imparted to the toner, and satisfactory image density and image quality cannot be obtained. It is easy to damage the body and damage the charging blade. Particularly preferred average particle size of the inorganic fine particles is 70
nm or less.

As the composition of the inorganic fine particles used in the present invention, conventionally known ones such as silica, alumina, titania and zirconia can be used. It is preferable that the surface of these inorganic fine particles is made hydrophobic with a silane coupling agent, silicone oil, or the like from the viewpoint of charging stability of the toner. The addition amount of the inorganic fine particles in the toner according to the present invention is 0.01 to 10% by weight based on the toner particles containing the binder resin, the colorant and the charge control agent.
And more preferably 0.1 to 5% by weight. Considering the particle size of the inorganic fine particles,
Furthermore, it is necessary to carefully adjust the charging blade in consideration of the material of the charging blade, the pressing pressure thereof, the material of the developing roll, and the like.
In the present invention, as a method for attaching the inorganic fine particles to the surface of the toner particles, any conventionally known powder mixing method can be used.

[Optional components externally added to toner particles]
Further, on the surface of the toner according to the present invention, in addition to the inorganic fine particles having the above-mentioned specific particle size range specified in the present invention, it is possible to prevent toner filming on the photoreceptor or to remove residual toner on the photoreceptor. Other additives may be used in combination for improvement. As these additives, silica, alumina, titania, zirconia, tin oxide, zinc oxide, carbon black, fluorinated graphite, silicon carbide, inorganic fine particles such as boron nitride, and acrylates, methacrylates, Fine particles of a homopolymer or copolymer such as styrene, fine particles of a fluororesin, fine particles of a silicone resin, fine particles of a higher fatty acid such as stearic acid and organic fine particles of a metal salt thereof can be given. In this case, the inorganic fine particles having an average particle diameter of 1 nm or more and less than 30 nm or about 100 nm to 1 μm can be used. The organic fine particles have an average particle size of 1 nm.
の も の 2 μm can be used.

[Toner Production Method and Image Forming Method] The toner production method according to the present invention includes a kneading and pulverizing method,
Conventionally known production methods such as a spray drying method and a polymerization method can be used.

In the image forming method of the present invention, the toner obtained as described above is used to develop a latent image on a latent image carrier to form a toner image, and the formed toner image is used to carry the latent image. The latent image carrier is transferred from the body to the transfer material, the latent image carrier after the transfer is cleaned, the toner on the latent image carrier is collected, and the collected toner is supplied to the developing unit side to be reused in the developing process. In the image forming method of the present invention, a conventionally known method can be used as a method of cleaning the latent image carrier after transfer. For example, blade cleaning, brush cleaning and the like can be mentioned.

[0026]

[Function / Effect] Since the particle diameter of the inorganic fine particles used in the toner according to the present invention is defined in an appropriate range,
Appropriate powder fluidity can be imparted to the toner, and the toner is less likely to be embedded in the toner due to the pressure applied from the recovery system. Therefore, by using the toner to which the inorganic fine particles are added, it is possible to provide a printing system in which the image density and the image quality are less changed by continuous copying and waste toner is not generated.
Further, since the polyester resin used as a binder of the toner according to the present invention contains a bisphenol A-based monomer and an alkyl or alkenyl succinic acid monomer component, the polyester resin is also crushed or spheroidized by stress received from a toner recovery system. It is hard to do. Further, when the glass transition temperature of the polyester resin is 70 ° C. or higher, the effect of the present invention becomes more remarkable.

[0027]

EXAMPLES Examples of the present invention will be described below, but the present invention is of course not limited to these examples. In the examples, parts indicated by parts represent parts by weight unless otherwise specified.

Production Example of Polyester Resin 540 g of polyoxypropylene (2.2 mol) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2 mol) -2,2-bis (4-hydroxyphenyl)
Put 215 g of propane, 225 g of terephthalic acid, and 31.5 g of n-dodecenyl succinic anhydride in a glass 1 liter four-necked flask, and attach a thermometer, a stainless steel stir bar, a fluidized condenser and a nitrogen inlet tube, and place in an electric heating mantle. Two
The temperature was raised to 30 ° C., and the reaction was carried out while stirring under a nitrogen stream. When the water generated by the reaction stopped flowing out, the acid value was measured to be 1.5. Further trimellitic anhydride
Add 94g and let it react for about 8 hours.
The reaction was terminated when the temperature reached 130 ° C. The obtained resin is a pale yellow solid, having an acid value of 25 mgKOH / g and a hydroxyl value of 26 mgKOH.
/ G, glass transition temperature = 74 ° C, and weight average molecular weight = 180,000. This resin is referred to as a polyester resin (1).

Example 1 Polyester resin (1) 100 parts Carbon black 6 parts Chromium / azo complex 2 parts Low molecular weight polypropylene / wax 2 parts The above compositions were premixed, kneaded with a pressure kneader, crushed and classified, and weight averaged. Colored particles having a particle size of 10 μm were obtained. To 100 parts of the colored particles, 0.4 part of silica R809 (average particle size = 40 nm) manufactured by Nippon Aerosil Co., Ltd. was added and mixed with a Henschel mixer to obtain a toner. This toner is a modified CASIO Printer CP-500 U (This printer has a system that collects the toner on the latent image carrier with a cleaning blade and supplies the collected toner to the developing unit side.)
Was used to perform a continuous printing test of 4000 sheets. In addition to the measurement of print image quality, the toner density was measured before and after the test. Table 1 shows the results.

Example 2 Silica MOX-80 (particle size = 30 nm) manufactured by Nippon Aerosil Co., Ltd. was treated with hexamethyldisilazane to prepare hydrophobic silica A having a methanol hydrophobicity of 38%. Example 1
To 100 parts of the same colored particles as above, 0.3 part of hydrophobic silica A was similarly mixed to obtain a toner. A continuous printing test was performed on this toner in the same manner as in Example 1. Table 1 shows the results.

Example 3 Alumina manufactured by Daimei Chemical Co., Ltd. (particle size = 60 nm) was subjected to hydrophobic treatment with hexamethyldisilazane to prepare hydrophobic alumina B having a methanol hydrophobicity of 21%. The same colored particles as in Example 1
0.8 part of hydrophobic alumina B was similarly mixed with 100 parts to obtain a toner. A continuous printing test was performed on this toner in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 1 Styrene-acrylic copolymer 100 parts (Sanyo Kasei Kogyo Hymer UN1-3000) (weight average molecular weight = 150,000, glass transition temperature = 59 ° C.) Carbon black 6 parts Chromium azo complex 2 parts Low Two parts of a molecular weight polypropylene wax were kneaded and pulverized and classified in the same manner as in Example 1 to obtain colored particles having a weight average particle diameter of 10 μm. To 100 parts of the colored particles, 0.4 part of silica R809 (average particle size = 40 nm) manufactured by Nippon Aerosil Co., Ltd. was added and mixed with a Henschel mixer to obtain a toner.
A continuous printing test was performed on this toner in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2 To 100 parts of the same colored particles as in Example 1, 0.2 parts of hydrophobic silica R972 (particle size = 16 nm) manufactured by Nippon Aerosil Co., Ltd. was added and mixed in the same manner to obtain a toner. A continuous printing test was performed on this toner in the same manner as in Example 1. Table 1 shows the results.

COMPARATIVE EXAMPLE 3 Alumina manufactured by Daimei Chemical Co., Ltd. (particle size = 100 nm) was hydrophobized with hexamethyldisilazane to prepare hydrophobic alumina C having a methanol hydrophobicity of 33%. The same colored particles as in Example 1
To 100 parts, 1.5 parts of hydrophobic alumina C was added and mixed in the same manner to obtain a toner. A continuous printing test was performed on this toner in the same manner as in Example 1. Table 1 shows the results.

[0035]

[Table 1]

Note) * 1: Measured with a powder tester manufactured by Hosokawa Micron Co., Ltd. * 2: Reflection densitometer R manufactured by Machbeth Process Measurements
Measured with D-914 * 3: Copy the image on the photoreceptor to mending tape,
The Y value was measured with a color difference meter CR-221 (manufactured by Minolta Camera Co., Ltd.), and indicated by the difference from the Y value of the original tape. A larger negative value means a larger fog.

As shown in Table 1, when the toner according to the present invention was used, the apparent loose density of the toner did not decrease even after continuous printing of 4,000 sheets, and a good image was stably provided. When the toner containing the styrene-acrylic copolymer of Example 1 was used, fine powder increased, fog increased, and white streaks occurred in the image. In the case of Comparative Example 2 using a toner to which silica having a small particle diameter was added, the loose apparent density of the toner was reduced, the image density was reduced, and the uniformity of solid black was deteriorated. Further, in the case of Comparative Example 3 using a toner to which inorganic fine particles having a large particle diameter were added, it was found that scratches occurred on the photoreceptor, and the inorganic fine particles were accumulated in the scratches. When the surface of the toner of Example 1 and the surface of the toner of Comparative Example 2 after printing 4,000 sheets were observed with a scanning electron microscope, it was confirmed that silica was present on the surface of the toner of Example 1; No silica could be confirmed on the toner surface of No. 2.

Claims (3)

(57) [Claims] 1. A method for developing a latent image on a latent image carrier to form a toner image, transferring the formed toner image from the latent image carrier to a transfer material, and cleaning the transferred latent image carrier. In an image forming method in which the toner on the latent image carrier is collected and the collected toner is supplied to the developing unit side and used in the developing step, the binder resin of the electrostatic image developing toner used is: The following general formula (I): [In the formula, R ¹ is an alkylene group having 2 to 4 carbon atoms, x and y are positive integers, and the average of the sum is 2 to 16. The diol represented by], versus the total polyol component
And (b) a polyol component containing 80 to 100 mol% of the following general formula (II) or (III): Embedded image Wherein R ² and R ³ are each a saturated or unsaturated hydrocarbon group having 4 to 20 carbon atoms. 1 to 50 mol% with respect to the polyol component (a), and trimellitic acid or the acid anhydride with 10 to 10 mol% with respect to the polyol component (a). A polyester resin obtained by condensation polymerization of a polycarboxylic acid component containing 30 mol%, and inorganic fine particles having an average particle diameter of 30 nm or more and less than 100 nm are adhered to the surface of the toner. Image forming method. 2. The image forming method according to claim 1, wherein the glass transition temperature of the binder resin is 70 ° C. or higher. 3. The image forming method according to claim 1, wherein the surface of the inorganic fine particles is subjected to a hydrophobic treatment.