JPH07333887A - Electrophotographic toner and its production - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic toner not causing blocking and having a long service life as a toner using a bonding resin having a low softening point and fixable at a low temp. by forming cured coating films of a mixture of a curable resin with fine particles of a specified average particle diameter on the surfaces of toner particles. CONSTITUTION:Cured coating films of a mixture of a curable resin such as silicone resin with inorg. or org. fine particles having <=1mum average particle diameter are formed on the surfaces of toner particles contg. at least a bonding resin and a colorant. In the case of 1mum average particle diameter, image quality is deteriorated because the fine particles bulk at the time of coating the surface of the toner in combination with the silicone resin and the particle diameter of the toner is increased. In the case of an excessively small average particle diameter, the effect of the fine particles as a filler is not satisfactory and the objective blocking resistance is not ensured. The most pref. average particle diameter is 0.2-0.6mum. Even when the resultant toner is put in an environment heated to the glass transition temp. of the bonding resin or above, blocking is not caused.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to toners used in electrophotography.

[0002]

2. Description of the Related Art Conventionally, as a developing method used in electrophotography, insulating fine powder containing a binder resin as a main component,
That is, a two-component system in which toner and the toner are charged by friction with a magnetic carrier and an electrostatic latent image formed on a photoconductor is developed by a magnetic brush, a magnetic one-component magnetic brush development system in which only a magnetic toner is developed, A so-called non-magnetic one-component developing method is known in which magnetic toner is formed in a thin layer on a developing sleeve and is developed in contact or non-contact with a photoconductor.

The toner developed by these methods is fixed on a transfer paper by a fixing process. Thermal fixing and pressure fixing methods are known as fixing methods. In the case of a thermal fixing method using a heat roll, oven, flash, etc., the softening point of the toner is an important factor for maintaining its fixing performance, and in order to reduce the heat energy when fixing at a higher speed and low temperature. It is preferable that the melting start temperature of the toner is low. However, if the melting start temperature of the toner is lowered, there is a problem that the blocking property deteriorates as the temperature lowers. That is, blocking between toner particles due to storage of the toner at a high temperature, blocking of toner onto the carrier due to friction with the carrier in the developing device, and blocking between collected toner particles in the cleaning process occurred. . Further, since toner used in the non-magnetic one-component system is charged and layered by rubbing the toner on the sleeve with a blade for forming a toner layer, the toner is subjected to heat or pressure. Therefore, when the melting start temperature of the toner is low, heat resistance and pressure resistance are lowered, resulting in blocking of the toner on the sleeve or blade, resulting in a problem that the developability is greatly impaired.

In the conventional toner, a binder resin such as polystyrene or polyester is mixed with a coloring agent such as carbon black and magnetic powder, a dye, etc. at an appropriate ratio, and after hot melt kneading, finely ground to 1 to 25 μm. Is used,
In order to prevent the above-mentioned blocking, the glass transition temperature (Tg) of the toner is designed to be high, and the blocking and fusion are very good, but the fixing performance is poor and the fixing at a lower temperature is difficult. It was difficult.

As a method of improving the blocking property, there is known a surface modification method in which a fluidizing agent is externally added to the surface of the toner, or an organic material or an inorganic material is mechanically attached to the surface of the toner. However, with these methods, it is difficult to completely coat the surface of the toner particles, which is necessary for preventing blocking, and a chemical treatment that requires a large-scale manufacturing process is required to form a complete capsule structure. I had one.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a long-life electrophotographic toner which does not cause blocking and is a toner using a binder resin having a low softening point that can be fixed at a low temperature.

[0007]

The present invention has been made in order to achieve the above-mentioned object, and its outline is that the surface of the toner particles containing at least a binder resin and a colorant has a curability such as a silicone resin. A toner for electrophotography, comprising a cured coating of a mixture of a resin and inorganic or organic fine particles having an average particle diameter of 1 μm or less, and a method for producing the same.

The curable resin used in the present invention may be an epoxy resin, a phenol resin, a polyester resin, a silicone resin, a modified acrylic resin, or the like, and is a resin that cures on the toner surface when used together with a curing agent. If available, it can be used. Above all, a silicone resin that can be cured at a low temperature and has good electric characteristics and moisture resistance is preferable. In addition to the narrowly defined silicone resin, a modified silicone resin modified with various resins can be used as the silicone resin. Examples of the room temperature curable silicone resin include trade names SR2410 and SR2420 manufactured by Toray Dow Corning.
SR2405, PRX305, SE5060, SE50
70, SE5004, SH237, SE9140, SE
1980, and the like. Further, as the curing catalyst, SH3170K manufactured by the same company can be exemplified.

The electrophotographic toner of the present invention uses a coating in which the curable resin and fine particles having an average particle size of 1 μm or less are mixed on the surface of the toner particles. When a cured coating is provided on the surface of toner particles that have poor storage stability with only curable resin, it is necessary to completely cover the toner surface in order to achieve sufficient storage stability. To this end, a large amount of curable resin must be added. Will be required. When a large amount of curable resin is used, agglomeration of toner particles may occur when the curable resin is cured, and it takes a long time to cure the curable resin film, which is a problem.
By mixing the fine particles with the curable resin, it is possible to minimize the amount of resin required to completely cover the surface of the toner, shorten the curing time, and form a uniform cured film. As the fine particles used in the present invention, inorganic fine particles such as silica, titanium oxide, alumina, magnetite and other ceramics or organic fine particles such as styrene resin, acrylic resin, silicon resin and fluorine resin are used. An average particle size of 1 μm or less is used. 1μ
If it is larger than m, the toner surface becomes bulky when coated with the silicone resin, and the toner particle size becomes large, so that the image quality deteriorates. On the other hand, if the average particle size is too small, the effect as a filler is not sufficient, and the desired blocking resistance cannot be obtained, which is not preferable. In this case, the average particle size is most preferably 0.2 μm or more and 0.6 μm or less. The average particle size in the present invention means the number average particle size of the primary particle size of the particles calculated from the projected area by image processing with an SEM photograph.

The toner particles constituting the toner for electrophotography of the present invention are composed mainly of a binder resin as in the case of the conventional toner. Therefore, the binder resin to be used depends on which binder resin is used. The starting temperature, that is, the fixing property is greatly affected. The binder resin used in the toner particles of the electrophotographic toner of the present invention, polystyrene, which has been conventionally used, styrene acrylate copolymer,
Polyester, epoxy resin and the like can be used, but the Tg of the toner particles is preferably 60 ° C. or lower in order to lower the fixing temperature of the toner particles. Further, it is preferable to use a resin having a small molecular weight as the binder resin. A resin having a small molecular weight has a low melting start temperature as compared with a resin having a large molecular weight, and is therefore preferably used.

Examples of such a resin include a styrene acrylate copolymer having a number average molecular weight of 9000 or less and a Tg of 60 ° C. or less. Tg of styrene acrylate copolymer is 60
As a method of lowering the temperature to not more than 0 ° C., for example, the content of butyl acrylate, which is a monomer having a low Tg, may be set to 20 parts or more out of 100 parts of all the monomer components constituting the resin. The melting start temperature of the binder resin made of such a copolymer is 100 ° C. or lower.

Thus, by selecting the binder resin to be used, the melting start temperature of the toner particles is lower than the conventional melting start temperature of 110 ° C., specifically 100 ° C.
The following can be controlled. However, if the melting start temperature of the binder resin is lowered more than necessary, for example, below the room temperature, the toner will always be in a molten state, which is not preferable for storage stability. Therefore, the melting start temperature is preferably higher than room temperature, for example, 60 ° C. or higher. Therefore, the melting start temperature of the binder resin used for the electrophotographic toner particles of the present invention is set to a temperature which is preferable for the toner to be fixed on the paper at low temperature and for storage stability, that is, 60 ° C. or higher and 100 ° C. or lower. Is preferred.

The toner particles constituting the present invention are prepared by mixing a binder resin, a colorant, a charge control agent, waxes and other additives as required in a predetermined composition, melt-kneading, cooling and solidifying. It is obtained by post-pulverization classification. Further, a so-called polymerization method toner prepared by mixing the above materials at the time of resin polymerization may be used. Examples of colorants include carbon black, monoazo red pigments, disazo yellow pigments, quinacridone magenta pigments, anthraquinone dyes, and the like, and charge control agents include nigrosine dyes, quaternary ammonium salts, and monoazo dyes. Examples of the metal salt dye include Other additives added as necessary include
Examples of the conventional materials include polyolefins such as polypropylene, hydrophobic silica, colloidal silica, and fluidizing agents such as resin fine particles.

To manufacture the electrophotographic toner of the present invention, first, toner particles are formed in the same manner as in the prior art, and the surface thereof is coated with a mixture of resin and fine particles. That is, the binder resin, the colorant, the charge control agent and, if necessary, other additives are mixed in a desired mixing ratio and melt-kneaded. Then, by cooling, the solidified product is pulverized and classified to obtain toner particles. Further, a polymerized toner formed by mixing the above materials at the time of polymerizing the binder resin may be used as the toner particles. Then, the surface of the obtained toner particles is coated and solidified with a mixture of a curable resin and fine particles to obtain the electrophotographic toner of the present invention.

As a method for forming a coating film of a mixture of a curable resin and fine particles on the surface of toner particles, a mixture of a curable resin such as a silicone resin and fine particles is previously added while stirring the toner in a high-speed stirrer. , After the addition,
A cured film of the resin is formed by blowing hot air into the stirrer while stirring or by raising the jacket temperature of the stirrer. Alternatively, an effect of forming a cured film in a short time can be obtained by treating the mixture with a hybridizer, an Ong mill, a turbo mill, a kryptron or the like which is used as a surface modifier, and simultaneously curing the mixture.

At this time, in order to prevent the toner from blocking, the curable resin used is preferably a low temperature curable resin. Further, the curable resin may be dissolved in an organic solvent and added, or may be added as an emulsion.
In this case, a solvent removal or dehydration process is required after the addition. As a method other than the above, a method in which toner particles and fine particles are mixed in advance, both are stirred with a high-speed stirrer and well dispersed, and then a curable resin is added to form a cured film is uniform in formation of a hard film. This is preferable because the effect of being able to achieve is obtained.

The Tg referred to in the present invention is measured by a differential scanning calorimeter (hereinafter referred to as DSC). As a measuring device, for example, a differential scanning calorimeter SS manufactured by Seiko Instruments Inc.
C-5200 is mentioned. As measurement conditions, about 10 mg of resin is weighed, placed in an aluminum cell, placed on a DSC, and 50 ml of N ₂ gas is blown therein for one minute.
And between 20 ℃ and 150 ℃, 10 ℃ per minute
The process of raising the temperature at a rate of, and then rapidly cooling from 150 ° C. to 20 ° C. is repeated twice and the amount of absorbed heat at that time is measured.
Here, Tg indicates the temperature at the intersection of the baseline at the second measurement and the tangent line showing the maximum slope from the endothermic start to the end point.

[0018]

The electrophotographic toner of the present invention is an electrophotographic toner containing at least a binder resin and a colorant, wherein the surface of the toner particles is coated with a mixture of a curable resin and fine particles having an average particle size of 1 μm or less. The toner for electrophotography, characterized in that, even if the binder resin, which occupies most of the toner weight, is placed in an environment where the temperature rises above the glass transition temperature due to heat, blocking does not occur.

The electrophotographic toner of the present invention is an electrophotographic toner containing at least a binder resin and a colorant, and the surface of the toner particles is coated with a mixture of a curable resin and fine particles having an average particle size of 1 μm or less. The toner for electrophotography is characterized in that the fixing temperature of the toner is considerably lower than that of the conventional toner.

[0020]

The present invention will be described in more detail based on the following examples. In the examples, "part" means "part by weight". In this example, first, toner particles A were prepared with the following composition.

The raw materials having the above composition are mixed with a super mixer, melt-kneaded, and then pulverized and classified to have an average particle diameter of 11
Toner particles A having a negative chargeability of μm were obtained. The melting temperature of the obtained toner particles was 89 ° C., and the Tg was 55 ° C.

Next, a cured coating film comprising a curable resin and fine particles was formed on the surface of the obtained toner particles A. The mode is as described in the following examples.

Example 1 Particle size distribution 0.3 to 0.7 with respect to 100 parts of toner particles A
μm silicone powder (Toray Dow Corning
Trade name: Trefill R-925) 0.4 part was stirred in a super mixer to deposit silicone powder on the surface of the toner particles. Furthermore, room temperature curing type silicone resin (trade name: SR2410 manufactured by Toray Dow Corning Co., Ltd.) 0.01
Part and curing catalyst (trade name: SH manufactured by Toray Dow Corning Co., Ltd.
3170K) was added in a minute amount and stirred to adhere the silicone resin to the surface of the toner particles. Then, the jacket temperature of the mixer was raised to 40 ° C., the mixture was stirred for 30 minutes, and left at room temperature for 1 week. Then, 100 parts of the surface-coated toner particles and 0.4 part of hydrophobic silica (Cabot Co., Ltd .: Kyabosil TS-530) are stirred for 1 minute in a Henschel mixer, and the surface of the particles is hydrophobic silica. Was adhered to obtain an electrophotographic toner of the present invention.

Example 2 Particle size distribution 0.3 to 0.7 with respect to 100 parts of toner particles A
0.3 parts of μ silicone powder (Toray Dow Corning product name: Trefill R-925), silicone resin (Toray Dow Corning product name: SR241)
0) The same operation as in Example 1 was performed except that 0.05 part was simultaneously added to the super mixer.

Example 3 Particle size distribution 0.3 to 0.7 with respect to 100 parts of toner particles A
0.2 parts of μ silicone powder (Toray Dow Corning product name: Trefil R-925), silicone resin (Toray Dow Corning product name: SR241)
0) The same operation as in Example 1 was performed except that 0.1 part was simultaneously added to the super mixer.

Example 4 50 parts of silicone powder (trade name: Trefil R-925, manufactured by Toray Dow Corning Co., Ltd.) having a particle size distribution of 0.3 to 0.7 μm in a beaker in advance, and silicone resin (product of Toray Dow Corning Co., Ltd.) Name: SR2410) 100
Part, curing catalyst (trade name: SH manufactured by Toray Dow Corning Co., Ltd.
3170K) was added in a trace amount and sufficiently stirred to prepare a mixture of silicone powder and silicone resin. 0.3 part was added to 100 parts of the obtained toner particles A, and the mixture was stirred in a super mixer to deposit a mixture of silicone powder and silicone resin on the surface of the toner particles. Then, the jacket temperature of the mixer was raised to 40 ° C., the mixture was stirred for 30 minutes, and allowed to stand at room temperature for 1 week to obtain toner particles having a coated surface. Then, 100 parts of the particles and hydrophobic silica (trade name: Cabosil TS-5 manufactured by Cabot Corporation)
30) 0.4 part was stirred in a Henschel mixer for 1 minute to adhere hydrophobic silica to the surface of the toner particles coated with the surface to obtain an electrophotographic toner of the present invention.

Example 5 In a beaker, 20 parts of a silicone powder having a particle size distribution of 0.3 to 0.7 μm (made by Toray Dow Corning, trade name: Trefil R-925) and a silicone resin (made by Toray Dow Corning) were used. Product name: SR2410) 100
Part, curing catalyst (trade name SH3 manufactured by Toray Dow Corning Co., Ltd.
170 K) was added in a trace amount and sufficiently stirred to prepare a mixture of silicone powder and silicone resin. The same operation as in Example 4 was performed except that 0.6 part of this mixture was added to 100 parts of toner particles A.

Comparative Example 1 To 100 parts of the toner particles A used in Example 1, silicone powder (trade name: Trefil R-925 manufactured by Toray Dow Corning Co., Ltd.) and room temperature curing type silicone resin (trade name manufactured by Toray Dow Corning Co., Ltd.) were used. : SR2410) and curing catalyst ((trade name: SH3 manufactured by Toray Dow Corning Co., Ltd.
The same operation as in Example 1 was performed except that 170 K) was not added to obtain a comparative electrophotographic toner.

Comparative Example 2 To 100 parts of the toner particles A used in Example 1, 0.01 parts of a room temperature curable silicone resin (trade name: SR2410 manufactured by Toray Dow Corning) and a curing catalyst (product of Toray Dow Corning manufactured) Name: SH3170K) added in a small amount, silicone powder (Toray Dow Corning
Trade name: Trefill R-925)
The same operation as in Example 1 was performed to obtain a comparative electrophotographic toner.

Comparative Example 3 To 100 parts of the toner particles A used in Example 1, 0.4 parts of silicone powder (trade name: Trefil R-925, manufactured by Toray Dow Corning Co., Ltd.) was added, and a room temperature curable silicone resin ( Toray Dow Corning product name: S
R2410) and a curing catalyst (trade name: SH3170K manufactured by Toray Dow Corning Co., Ltd.) are not added.
The same operation as above was performed to obtain a comparative electrophotographic toner.

Comparative Example 4 To 100 parts of the toner particles A used in Example 1, 1.0 part of silicone powder (trade name: Trefil R-925 manufactured by Dow Corning Toray Co., Ltd.) was added, and a room temperature curable silicone resin (Toray Co., Ltd.) was added. Dow Corning product name: S
R2410) and a curing catalyst (trade name: SH3170K manufactured by Toray Dow Corning Co., Ltd.) are not added.
The same operation as above was performed to obtain a comparative electrophotographic toner.

Comparative Example 5 0.4 part of silicone powder having a particle size of 1 to 10 μm (trade name: Torayfill R-902 manufactured by Toray Dow Corning Co., Ltd.) and 100 parts of toner particle A, and silicone resin (trade name of Toray Dow Corning Co., Ltd .: SR2410) 0.01
The same operation as in Example 1 was carried out except that a part was added to obtain a comparative electrophotographic toner.

The blocking properties of the toners obtained in Examples 1 to 5 and Comparative Examples 1 to 5 were evaluated. To evaluate the blocking property, 20 g of each of the obtained toners was filled in a 150 cc bottle and left in a constant temperature bath at 50 ° C. for 8 hours, and then the caking state of the toner was visually confirmed. The results are shown in Table 1.

[0034]

[Table 1]

Further, the above Examples 1 to 5 and Comparative Examples 1 to
5 parts of the toner obtained in Comparative Example 5 and a ferrite carrier (trade name F141-1530 manufactured by Powder Tech Co., Ltd.) 1
A developer was prepared by mixing with 100 parts. The obtained developer is a laser printer (trade name WD- manufactured by SHARP).
02LP) and the image quality and fixability of the toner were confirmed.

The fixing property of the toner was measured by setting the heat roller temperature of the laser printer to 130 ° C., measuring the image density (A) of the image obtained by fixing the toner, and then rubbing the image with an eraser. Then, the obtained image density (B) was measured and confirmed by the residual ratio (%) according to the following formula.

Residual rate (%) = (B / A) × 100

The residual ratio of the image density is a value measured by a Macbeth reflection thermometer (trade name: RD-914 manufactured by Toshiba Chemical Co.). Image quality is 25 ° C and 60% RH,
A continuous print test of 5,000 sheets was conducted using the above laser printer, an image density was measured using the Macbeth reflection densitometer, and a white meter (manufactured by Nippon Denshoku Industries Co., Ltd., trade name: MOD
It was confirmed by measuring the background stain of the non-image area using EL Z-1001 DP). The results of these measurements are shown in Table 2 below. In the table, ID is image density, BG
Indicates the background stain of the non-image area.

[0039]

[Table 2]

In Comparative Examples 1 to 4, toner lumps were generated in the developer to cause image defects, and in Comparative Example 5, fine line reproducibility was poor.

From the results shown in Tables 1 and 2 above, it is understood that the toner according to this embodiment is superior in fixing property, storability and image characteristics to the conventional toner.

In the electrophotographic toner according to this embodiment, the surface of the toner particles is provided with the cured coating of the mixture of the curable resin and the fine particles, so that the binder resin occupying most of the toner weight is heated by the heat. Even if softened, the binder resins do not come into contact with each other, so that blocking can be prevented from occurring.

Further, the melting start temperature of the entire electrophotographic toner of this embodiment could be controlled to 89 ° C. Since this temperature is considerably lower than the melting start temperature of the conventional toner of 110 ° C., the thermal fixing device can be maintained at a temperature much lower than the conventional temperature. Therefore, according to the electrophotographic toner of this embodiment, the power consumption of the copying machine can be reduced.

[0044]

The electrophotographic toner according to the present invention is an electrophotographic toner containing at least a binder resin and a colorant, and has a cured resin on the surface of the toner particles and an average particle size of 1 μm.
Since the cured coating is provided with a mixture of fine particles of m or less, even if the binder resin, which occupies most of the weight of the toner, is softened by heat, the binder resins do not come into contact with each other. It can be prevented from occurring.

The electrophotographic toner according to the present invention is an electrophotographic toner containing at least a binder resin and a colorant, and the curable resin on the surface of the toner particles and the average particle size of 1 μm.
A cured coating is provided with a mixture of fine particles of m or less,
Since the melting start temperature of this toner is considerably lower than the melting start temperature of the conventional toner, which is 110 ° C., the heat fixing device can be maintained at a temperature considerably lower than the conventional temperature. Therefore, according to the electrophotographic toner of this embodiment, the power consumption of the copying machine can be reduced.

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[Procedure amendment]

[Submission date] June 22, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

As a method for forming a coating film of a mixture of a curable resin and fine particles on the surface of toner particles, a mixture of a curable resin such as a silicone resin and fine particles is previously added while stirring the toner in a high-speed stirrer. , After the addition,
A cured film of the resin is formed by blowing hot air into the stirrer while stirring or by raising the jacket temperature of the stirrer. Or a mixture hybridizer which is used as a surface treating device, Angmill, turbo mill, it is possible to obtain an effect of forming a cured object layer in a short time by hardening and simultaneously processed using such cryptron.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

At this time, in order to prevent the toner from blocking, the curable resin used is preferably a low temperature curable resin. Further, the curable resin may be dissolved in an organic solvent and added, or may be added as an emulsion.
In this case, a solvent removal or dehydration process is required after the addition. As a method other than the above, were mixed in advance toner particles and fine particles, stirring them at high speed stirrer, it was well dispersed, forming methods hardening coating to form a cured coating film by adding a curable resin It is preferable because the effect of being uniform can be obtained.

Claims (6)

[Claims] 1. An electrophotographic toner containing at least a binder resin and a colorant, wherein the surface of the toner particles is coated with a mixture of a curable resin and fine particles of an inorganic or organic material having an average particle diameter of 1 μm or less. Toner for electrophotography. 2. The toner for electrophotography according to claim 1, wherein the curable resin is a silicone resin. 3. The toner for electrophotography according to claim 1, wherein the glass transition temperature of the toner particles is 60 ° C. or lower. 4. The toner for electrophotography according to claim 1, wherein the average particle diameter of the fine particles made of an inorganic material or an organic material is 0.2 μm or more and 0.6 μm or less. 5. A toner for electrophotography, characterized in that the surface of toner particles containing at least a binder resin and a colorant is coated with a mixture of a curable resin and fine particles of an inorganic or organic material having an average particle size of 1 μm or less. Manufacturing method. 6. A toner film containing at least a binder resin and a colorant and fine particles of an inorganic material or an organic material are mixed in advance and dispersed by stirring, and then a curable resin is added to form a cured film. A method for producing a toner for electrophotography.