JP4965966B2 - Electrophotographic dry toner and electrophotographic image forming method - Google Patents

Description

  The present invention relates to a dry toner for electrophotography and an electrophotographic image forming method, and particularly to an invention such as a self-repairing dry toner for electrophotography that can provide excellent image quality.

  Conventionally, electrophotographic methods have been applied to copiers, fax machines, printers, and the like. The electrophotographic toner is used to visualize (develop) an image in the electrophotographic method applied as described above.

  The electrophotographic method includes charging, exposure, development, transfer, cleaning, and fixing processes, and the image quality (image quality) is greatly affected by the development process and the transfer process in these processes. In particular, in the transfer process, toner called image dust is scattered and adhered to a region outside the latent image, which is a major cause of inferior image quality compared to an offset print image. In other words, dot reproducibility is poor.

Various attempts have been made in the past to suppress such image dust, but they all suppress image dust in the transfer process, and those that attempt to repair image dust once generated on a transfer material are As far as the inventors know, there was nothing.
Conventionally, as a toner,
(1) The melt viscosity at the time of melting is low (so-called shababa state),
(2) It has been pursued to improve the wettability of paper and soak it into paper fibers when melted to improve the fixability.
On the other hand, finding an advantage by reducing the penetration into paper has never been done.

On the other hand, an invention of a wet (liquid) toner comprising a mixture of ethylene vinyl acetate and a copolymer ionomer of ethylene and methacrylic acid for the purpose of rapid melting and good film formability is known (for example, Patent Document 1). reference).
JP 7-700922A

However, the above-mentioned patent document relates to a wet toner, and nothing is mentioned about the dry toner and the function described in the present invention.
Furthermore, although mention is made of paper wettability, according to the present invention, it is stated that it is preferable to lower the melt viscosity and improve the wettability with paper in order to improve the permeability to paper. On the contrary, there is no idea of making wettability worse as far as the inventors know. Furthermore, nothing is written about toners combined with low surface energy materials.

  The present invention has been made in consideration of the above-described circumstances, and supplies an electrophotographic toner and an electrophotographic image forming method image forming apparatus having a function of self-recovering dust toner formed on a transfer material after transfer. For the purpose.

  In order to achieve the above object, the invention described in claim 1 heats a toner image including a target image developed with toner having at least a binder resin and a colorant and scattered toner scattered around the target image. It is a self-healing type electrophotographic dry toner that functions to fix and to self-repair the toner image to the target image.

  According to a second aspect of the present invention, in the electrophotographic dry toner according to the first aspect, the binder resin has a mixture of ethylene acetate vinyl ester and an ionomer derived from a copolymer of ethylene and methacrylic acid. Features.

  According to a third aspect of the present invention, in the electrophotographic dry toner according to the first or second aspect, the binder resin further contains a low surface energy resin.

  According to a fourth aspect of the present invention, in the electrophotographic dry toner according to any one of the first to third aspects, the toner is produced in a pulverization method or an aqueous medium.

  According to a fifth aspect of the present invention, there is provided an electrophotographic image forming method using the electrophotographic dry toner according to any one of the first to fourth aspects.

  According to the electrophotographic dry toner and the electrophotographic image forming method of the present invention, the image quality can be improved in a self-repairing manner.

  An object of the present embodiment is to supply an electrophotographic dry toner having a function of self-repairing dust toner formed on a transfer material after transfer. This makes it possible to improve the image quality on the transfer material after transfer, which has not even been conceived in the past, and an image forming method using such a dry toner for electrophotography. The purpose is to provide.

  Hereinafter, the dry toner for electrophotography and the electrophotographic image forming method of this embodiment will be described in detail with reference to the drawings.

  In electrophotography, a photoconductor and a developer are used, and images are formed by the charging, exposure, development, transfer, cleaning, and fixing processes. In terms of image quality, the image quality of the toner image on the photoconductor is developed. Deteriorated in the process and the transfer process. In particular, the image is disturbed in the transfer process. This is mainly because, in the transfer process, dust toner other than the target image is generated around the latent image called image dust in the image transferred onto the transfer material.

  The target image in the present embodiment refers to a so-called original image. For example, when transferring a document image (original image) read by an image reading device or the like, it is desirable that the image on the transfer paper and the document image are exactly the same. In order to make the image on the transfer paper the same as the original image, the target position where the toner is attached to the transfer paper and the position where the toner is actually attached need to be the same. That is, the target image is an image in which toner is attached to the target position, that is, an original image.

  It is considered that the main generation mechanism of dust toner is that toner is scattered when the toner is peeled off from the photosensitive member by a transfer means to which voltage is applied and arrives at the transfer material.

This process will be described in detail below.
In the electrophotographic method, a latent image formed on a photoreceptor is developed with a developer, transferred to a transfer material such as paper, and then an electrophotographic dry toner image on the transfer material is fixed. Get.
Conventionally, the toner image on the transfer material after transfer has been blurred so that the latent image cannot be identified. That is, the toner spreads from the latent image area, and the number of toner particles decreases as the distance from the center increases. After fixing, a film is formed in a portion where the toner layer thickness (pile height) is high, but the peripheral dust toner is crushed but does not move and is fixed on the spot. In this way, the image has a lot of dust, and the image is blurred, and the image quality is impaired.

On the other hand, conventionally, in order to complete the fixing property of the toner,
(1) The melt viscosity at the time of melting is low (so-called shaba shaba),
(2) Designed with good wettability to paper. In the fixing process, pressure is simultaneously applied in addition to the heat.
The melted toner is subjected to pressure on the paper side and has good wettability with the paper, so that it penetrates into the paper fiber (also wraps around the back side of the paper fiber). This is referred to as so-called anchoring, which makes the fixing property good.

  In this embodiment, when the toner image on the transfer material after transfer (an image by an electrophotographic dry toner image) is the same as described above, the toner at the center of the image melts and forms a lump after fixing, Except for isolated toner on the outer periphery, after the dust toner around the image is melted and merged (shrinked (rounded)), it spreads again by application of pressure (when combined with heating) and spreads slightly more than the latent image However, an image with good image reproducibility with less image dust (blurred image) can be obtained as compared with a conventional image after fixing. That is, the molten mass collects (absorbs) surrounding dust toner and improves image reproducibility (approximation to the target image). The toner having such an effect is referred to as a self-repairing toner in this embodiment. The above phenomenon occurs because the dry toner for electrophotography of the present embodiment forms a molten lump and merges the peripheral dust toner and shrinks like mercury (rounded: rounded by so-called interfacial tension during melting). This is because it has properties.

  Further, in order to easily form the molten mass, and to easily merge and round, it is desirable that the molten mass has a property of poor wettability with respect to paper fibers mainly composed of cellulose. This property is achieved by including a substance (low surface energy substance) that reduces surface energy such as a fluorine compound in the electrophotographic dry toner of this embodiment.

  Thus, even if the design is poor in wettability with paper, pressure is simultaneously applied at the time of fixing and melting, and the molten mass is pressed to the paper side by the pressure, and as a result, while maintaining sufficient fixing force ( Slightly less than the one having good wettability), soaking or wrapping around the paper fiber, that is, anchoring occurs, and fixing property is secured.

Repeatedly, the dust toner is absorbed and merged into the central portion (target image) to be rounded and then pressed to become a fixed image. That is, although the area is slightly larger than that of the latent image, the area that is larger than that of the conventional toner is small, and an image with good image reproducibility can be obtained.
In order to obtain such an image, the pressure at the time of fixing is not limited as long as the fixing property can be secured and the image is not crushed. For example, the pressure is preferably as small as possible. Thereby, higher image reproducibility can be obtained.

  The dry toner for electrophotography of this embodiment is achieved by employing a mixture of ethylene acetate vinyl ester and ethylene methacrylic acid copolymer ionomer as a binder resin.

  The mixture of ethylene acetate vinyl ester and ethylene methacrylic acid copolymer ionomer has a sharp drop in melt viscosity, a lower inflection point, and a rapid change in melt viscosity compared to when each is used alone. It has the property of melting and easily forming a film at a stretch. For this reason, it is preferable for the electrophotographic dry toner of this embodiment to use these mixtures as a binder resin for the toner.

  Further, the ethylene methacrylic acid copolymer ionomer improves the film formability of the toner and exhibits a sharp melting property. This works effectively by mixing with the above-mentioned ethylene methacrylic acid copolymer ionomer.

Furthermore, the mixture of ethylene acetate vinyl ester and ethylene methacrylic acid copolymer ionomer has a shrink property (shrinkage: property of rounding) when heated and melted.
This is because the toner containing a mixture of the ethylene vinyl acetate and the ethylene methacrylic acid copolymer ionomer has an irregular shape in which the beard-like (fiber-like) parts gathered randomly, and these fibers are entangled and bulky. It is presumed that it has a high composition and shrinks (shrinks rapidly) in a state where these bulks collapse and coalesce at the time of heat melting.

A suitable mixing ratio of the two is, by weight, ethylene acetate vinyl ester: ethylene methacrylic acid copolymer ionomer = 1: 1 to 1: 4. A preferable content of the mixture is 10 to 70% by weight based on the total weight of the toner.
Examples of the ethylene vinyl acetate include Elbux (registered trademark) 4355 (manufactured by DuPont), and examples of a suitable ethylene methacrylate copolymer ionomer include Surlyn (registered trademark) 9020 (manufactured by DuPont).

  In the present embodiment, it is preferable that the mixture of the ethylene acetate vinyl ester and the ethylene methacrylic acid copolymer ionomer further has a low surface energy substance. As such a preferable low surface energy substance, a thermoplastic fluororesin is used. And polypropylene or polyethylene having a number average molecular weight of 200 to 10,000. These may be used alone or in combination. As the fluororesin, polytetrafluoroethylene having the following structural formula is well known as a low surface energy substance.

CF ₃ — (— CF ₂ ) n —CF ₃ : In the formula, n is a repeating unit. In the above formula, fluorine element is —OH, —H, —Cl or other group (for example, alkyl group, aryl group, amino group, amide) It may be replaced with a group.
More specifically, for example, thermoplastic fluororesin: manufactured by Sumitomo 3M: THV220 (melting point: 110 ° C.) may be used, but various other thermoplastic fluororesins may be used.

  Polyethylene is a polymer composed of hydrocarbons, and has poor polarity and poor wettability to cellulose, which is the main component of paper. However, when the molecular weight is 10,000 or more, the melting point increases and the melt viscosity also increases. The characteristics of the embodiment are inappropriate. Polypropylene has the same molecular weight range, and has poor wettability to paper, as is the case with polyethylene. The addition of polypropylene and polyethylene to the toner has been known for some time, but not so as to reduce the wettability of the paper fiber this time, but to prevent adhesion (referred to as offset) to the fixing roller during fixing. This is for providing moldability, and the content is at most 10% by weight (that is, less than 10% by weight), and 10 to 90% by weight of the binder resin is not contained as in this embodiment.

  Polypropylene and polyethylene may be used alone or in combination. Moreover, you may use together at least 1 sort (s) of a polypropylene or polyethylene (a polypropylene or polyethylene, a polypropylene, and polyethylene) and a thermoplastic fluororesin.

  An SP value (solubility parameter) can be used as a scale for judging wettability. As for the SP value, for example, the SP value of the fluororesin is about 6, polypropylene is 7.9, polyethylene is 8, and if the paper is represented by cellulose, the cellulose is about 20. Therefore, the order of decreasing the wettability is also the order of fluororesin, polypropylene, and polyethylene.

The electrophotographic dry toner of this embodiment is preferably formed by mixing a mixture of ethylene acetate vinyl ester and ethylene methacrylic acid copolymer ionomer, or a mixture thereof with a low surface energy substance. The mixing method is not limited. For example, it can be dissolved in a soluble solvent or dispersed in a dispersion medium and mixed. Suitable solvents (dispersing agents) used at this time include ethyl acetate, MEK (methyl ethyl ketone), toluene and the like, but other solvents or dispersing agents may be used. The amount of these solvents or dispersion media used is not particularly limited.
As for the content, the content of the low surface energy substance can be added in the range of 10 to 100% by weight, preferably 10 to 90% by weight as described above in terms of the solid content with respect to the total weight of the toner.

  In the present embodiment, in addition to the binder resin, conventionally used styrene acrylic resins, polyester resins, polyol resins, epoxy resins, vinyl resins, butyral resins, phenol resins, and the like can be used in combination.

  Generally used pigments are suitably used in the present embodiment. For example, carbon black for black and white toner, magenta for quinacridone, naphthol, cyan for copper phthalocyanine, and yellow for C.I. I. Pigment Yellow 17 is typical, but other known pigments and the like can also be used.

  As the release agent in the present embodiment, those generally used are preferably used. For example, natural waxes such as carnauba wax, beeswax, candelilla wax, rice wax and montan wax, petroleum waxes such as paraffin wax and microcrystalline wax, higher fatty acids such as stearic acid, palmitic acid and myristic acid and higher Examples include fatty acid metal salts, higher fatty acid amides, and various modified waxes thereof.

Examples of the charge control agent used in the electrophotographic dry toner of this embodiment include a salicylic acid metal complex, a quaternary ammonium salt, nigrosine, an azo pigment, a fluorine compound, and curixallene.
After the toner particles are generated, an additive composed of inorganic fine particles may be mixed and adhered to the surface. Suitable additives include silica, titanium oxide and the like, which may be used alone or in combination of two or more.
The particle diameter of the electrophotographic dry toner of this embodiment is preferably about 3 to 10 μm in terms of volume average particle diameter.

The binder resin used in the electrophotographic dry toner of this embodiment can be produced by a conventional pulverization method, or can be produced by a method of generating in an aqueous medium that has been spreading rapidly in recent years. As a production method in an aqueous medium, suspension polymerization, emulsion aggregation, polymer aggregation method, association method, seed polymerization, dispersion polymerization, extension reaction method and the like can be used.
In the dry toner for electrophotography used in the examples of the present embodiment, a method of obtaining a dry toner by a spray dry method after once generating a liquid toner was used. It can also be created by other methods, but is not limited to this. In this case, a mold release agent, an additive, etc. can be used separately.

The electrophotographic toner of this embodiment is preferably used as a dry toner. The dry toner may be used alone as a one-component toner, but may be used as a two-component developer by mixing with a carrier.
As a carrier when used as a two-component developer, for example, core particles made of magnetic particles such as ferrite, hematite and iron powder are provided with a resin coating. The particle size is preferably 25-100 μm. As the coating resin, silicone resin, fluororesin, methylmethacrylic resin, or the like is used.
The carrier and the toner are used by charging the toner by stirring. A suitable mixing ratio is 1 to 10% by weight with respect to the carrier 100. The absolute value of the charge amount of a suitable toner obtained at this time is about 10 to 30 μC / g.

  As will be described later, the image was printed using a commercial machine manufactured by our company. Measurement and evaluation methods will be described next to the examples.

[Example]
Hereinafter, the present embodiment will be described in more detail by way of examples. All parts are parts by weight, and% is% by weight.

[Example 1]
(Magenta toner)
Binder resin A (ethylene acetate vinyl ester (Elbacs 4355 manufactured by DuPont): ethylene methacrylic acid copolymer ionomer (Surlin 9020 manufactured by DuPont) = 1: 4 (weight ratio), inflection point of melt viscosity 40 ° C.)
1000 parts by weight Isopar L 1000 parts by weight is mixed at low speed for 1 hour in a jacketed double planetary mixer connected to an oil heater set at 170 ° C.

  To this mixture is added 2000 parts by weight of ISOPAR L2000 preheated to about 110 ° C., and the whole is further mixed at high speed for 1 hour. The material is cooled in the mixer until it reaches about 70 ° C., at which point the material is drained from the mixer into an aluminum pan. The material is cooled to room temperature, cut and passed through a meat grinder to create a crushed material.

1050 parts by weight of pigment-added crushing material Quinacridone-based magenta pigment (CI Pigment Red 122)
66 parts by weight Isopar L 1200 parts by weight was charged into an S1 grinder (manufactured by Union Press) and finely pulverized with a 3/16 inch carbon steel ball for 10 hours while cooling with water. The resulting toner particles have a median diameter value (by weight) of about 2 μm. The resulting material is diluted with Isopar L to a non-volatile solid content of 1.5%. To the obtained diluted solution, zirconium naphthenate is added as a charge control agent so as to contain 0.5% based on the solid content to control the charging of the toner particles.

  The obtained liquid toner was sent to Pulvis Mini-Spray GS31 (manufactured by Yamato Kagaku Co., Ltd.), which is a small spray dryer, and spray-dried to collect the toner in a collection bottle under the cyclone. At this time, the air pressure of the compressor for spraying was 2 kg. The actual yield of toner was about 120 g. The volume average particle diameter of the toner was 8.0 μm.

Spray Drying Process Liquid toner is sent to a spray dryer (spray dryer). Delivery is controlled by a valve. The liquid toner is sent to the nozzle by a pump, is sent to the nozzle tube at high pressure by high-pressure air sent from the other side to the nozzle, and is sprayed from the nozzle tip in the chamber. The chamber and the cyclone are connected, exhaust air is sucked from the cyclone by decompression means (for example, vacuum pump with trap), and the air separated into the solvent and air returns to the chamber again and becomes a parallel flow by the control plate, and the weak flow becomes steady Formed and circulated.

  Since air is blown from the nozzle tip at a high pressure, an air flow is generated in the chamber, and the chamber diameter is very large compared to the nozzle tip diameter, so that the flow rate rapidly decreases. Further, since the outflow amount is negligible compared to the air flow in the chamber, the air flow in the chamber is not affected. The airflow in the chamber becomes a vortex in the cyclone, and the airflow decreases in the cyclone and reaches the bottom of the cyclone.

Since the diameter of the collection bottle is larger than the diameter of the bottom of the cyclone, the velocity of the airflow entering here is further reduced, and the toner particles are almost free-falling and separated by gravity and collected in the collection bottle. Be collected. The collected toner particles are completely dried while passing through the above air flow.
A weak rotating air stream remains in the center of the cyclone, but this is sucked by the depressurizing means as described above and sent to the solvent / air separation section. The separated solvent is recovered and air is circulated.

As described above, the obtained toner and the base toner have an irregular shape in which the beard-like (fiber-like) portions are randomly gathered, and these entangled fibers are combined at the time of heat melting and shrink (bulk). Is suddenly reduced).
Further, 0.5 part by weight of hydrophobic silica was mixed with 100 parts by weight of the obtained base toner using a Henschel mixer to obtain toner 1 as the final magenta toner.
Coulter counter manufactured by Coulter Electronics Co., Ltd. The volume average particle diameter of Toner 1 measured by Model TA-II was 8.9 μm.

  The toner 1 was added at a ratio of 5 parts by weight to 100 parts by weight of a carrier in which a silicone resin was surface-coated on ferrite particles having an average particle diameter of 50 μm, and mixed using a tumbler mixer to obtain a magenta developer 1. .

Using the magenta developer 1 thus obtained, a pseudo image was formed, the toner image was magnified (approximately 1,000 times) with an optical microscope, photographed, and then carefully passed through a single fixing device for fixing property evaluation. Similarly, the corresponding parts were photographed and compared.
Although the details of the results will be described later, a portion where peripheral toner is absorbed is recognized in the image after fixing.
The structure of a single fixing device for evaluating the fixing property is a device in which a MF2200 fixing unit made in-house using a Teflon (registered trademark) roller as a fixing roller is modified. The fixing condition is that the linear velocity of paper feed is 120 mm / sec. The surface pressure was 1.2 kgf / cm ² and the nip width was 3 mm.

[Example 2]
(Cyan toner)
A cyan dry toner 2 was obtained in the same manner as in Example 1 except that the pigment was replaced with 66 parts by weight of the blue pigment BT-383D (DuPont) in Example 1.
As with the toner 1, the base toner of the toner 2 had an irregular shape in which the beard-like (fiber-like) portions gathered randomly.
Coulter Counter manufactured by Coulter Electronics Co., Ltd. The volume average particle diameter of Toner 2 measured by Model TA-II was 8.3 μm.

The toner 2 was added at a ratio of 5 parts by weight to 100 parts by weight of a carrier in which a silicone resin was surface-coated on ferrite particles having an average particle diameter of 50 μm, and mixed with a tumbler mixer to obtain a cyan developer.
When the obtained cyan developer was used and the images before and after fixing were compared in the same manner as in Example 1, a portion where peripheral toner was absorbed as in Example 1 was observed.

[Example 3]
(Yellow toner)
In Example 1, a yellow dry toner 3 was obtained in the same manner as in Example 1 except that the pigment was replaced with yellow pigment YT-717D66 parts by weight.
As with the toner 1, the base toner of the toner 3 had an irregular shape in which the bearded (fiber-like) portions gathered randomly.
Coulter counter manufactured by Coulter Electronics Co., Ltd. The volume average particle diameter of the toner 3 measured by Model TA-II was 7.9 μm.

The toner 3 was added at a ratio of 5 parts by weight to 100 parts by weight of a carrier in which a silicone resin was surface-coated on ferrite particles having an average particle diameter of 50 μm, and mixed with a tumbler mixer to obtain a yellow developer.
When the obtained yellow developer was used and the images before and after fixing were compared in the same manner as in Example 1, a portion where peripheral toner was absorbed as in Example 1 was observed.

[Example 4]
(Black toner)
A black dry toner 4 was obtained in the same manner as in Example 1 except that the pigment was replaced with 66 parts by weight of Mogal L carbon black (Cabot) in Example 1.
As with toner 1, the base toner of toner 4 had an irregular shape in which the beard-like (fiber-like) portions gathered randomly.
Coulter Counter manufactured by Coulter Electronics Co., Ltd. The volume average particle diameter of Toner 1 measured by Model TA-II was 8.1 μm.

The toner 4 was added at a ratio of 5 parts by weight to 100 parts by weight of a carrier in which a silicone resin was surface-coated on ferrite particles having an average particle diameter of 50 μm, and mixed using a tumbler mixer to obtain a black developer.
When the obtained black developer was used and the images before and after fixing were compared in the same manner as in Example 1, a portion where peripheral toner was absorbed as in Example 1 was observed.

[Example 5]
The binder resin A is a mixture of the following ethylene acetate vinyl ester (Elbacs 4355 manufactured by DuPont): ethylene methacrylate copolymer ionomer (Surlin 9020 manufactured by DuPont) = 1: 4 (weight ratio), inflection point of melt viscosity 40 ° C. )
800 parts by weight Low surface energy substance (thermoplastic fluororesin: manufactured by Sumitomo 3M: THV220, melting point 110 ° C.) Magenta dry toner 5 was obtained in the same manner as in Example 1 except that 200 parts by weight was used.
As with the toner 1, the base toner of the toner 5 had an irregular shape in which the bearded (fiber-like) portions gathered randomly.
Coulter Counter manufactured by Coulter Electronics Co., Ltd. The volume average particle diameter of Toner 1 measured by Model TA-II was 8.6 μm.

The toner 5 was added at a ratio of 5 parts by weight with respect to 100 parts by weight of a carrier in which a silicone resin was surface-coated on ferrite particles having an average particle diameter of 50 μm, and mixed with a tumbler mixer to obtain a magenta developer 2.
When the obtained magenta developer 2 was used and the images before and after fixing were compared in the same manner as in Example 1, the shrinkage was stronger than in Example 1.

[Comparative example]
Binder resin B: Polyester resin synthesized from ethylene oxide adduct of bisphenol A, terephthalic acid, fumaric acid, Mw: 35000, Mn: 12,000, softening point 92 ° C. 100 parts by weight Wax: carnauba wax: melting point 60 ° C. 4 Part by weight Carbon black # 44 (Mitsubishi Chemical) 4 parts by weight Charge control agent: salicylic acid derivative zinc salt (Bontron E-84)
2 parts by weight The above materials were sufficiently mixed with a blender and then melt-kneaded with two rolls heated to 130 to 140 ° C. The obtained kneaded product was allowed to cool naturally, then coarsely pulverized by a cutter mill, pulverized by a fine pulverizer using a jet stream, and a base toner of a magenta comparative example was obtained using an air classifier.

The base toner of the comparative example was merely indefinite, and had no beard-like (fiber-like) structure.
Therefore, it is predicted that there is no shrinking (rounding) function.
Further, 0.5 parts by weight of hydrophobic silica was mixed with 100 parts by weight of the obtained base toner of the comparative example using a Henschel mixer to obtain a magenta comparative toner 1.
Coulter Counter manufactured by Coulter Electronics Co., Ltd. The volume average particle diameter of Comparative Toner 1 measured by Model TA-II was 8.6 μm.

The comparative toner 1 is added at a ratio of 5 parts by weight to 100 parts by weight of a carrier in which a silicone resin is surface-coated on ferrite particles having an average particle diameter of 50 μm, and is mixed using a tumbler mixer to obtain a comparative magenta developer 1. It was.
Using the obtained magenta developer 1, a pseudo image was formed, and the toner image was magnified (approximately 1,000 times) with an optical microscope to take a photograph, and then passed through a single fixing device for fixing property evaluation. Similarly, the corresponding part was photographed and compared. The configuration and conditions of the single fixing device for fixing property evaluation were the same as those in Example 1.

After fixing, the portion having a high toner layer thickness (pile height) forms a film, but the surrounding dust toner is crushed but does not move and is fixed on the spot.
Therefore, it was concluded that there was no shrinking (rounding) function (which was naturally predicted from the fact that the above-described structure is not the structure of the present embodiment).

  As described above, the shrinking (rounding) function of the toner of the present invention is caused by having a special shape of the special binding resin of the toner of the present invention due to a special blending, etc. Resin, manufacturing method, etc. are different, and the toner of the present invention has no function and shape.

The following is a result of comparison from photographs of images in Example 1 and Comparative Example. All are photomicrographs taken at a magnification of 1,000. The image is a pseudo image and is an irregular image.
The difference in function and shape between the toner of the present invention and the comparative toner 1 depends on the special resin and the production method, and the influence of the pigment is small. Therefore, the toner of Example 1 (magenta toner) and the comparative toner 1 (black toner) are different in pigment, but have no essential influence.

FIG. 1 is a photograph of the toner 1 in Example 1 before fixing. In this photograph, some lump of toner is recognized, and the toner in the upper right part of the figure is sparsely present. FIG. 2 is a photograph after fixing of FIG.
In FIG. 2, the arrow points are filled with black in FIG. 1 before fixing, indicating that there is toner. This is white in FIG. 2, indicating that the toner in the black part of FIG. 1 has been absorbed, moved and disappeared when the upper mass shrinks (rounds). Then, as shown in FIG. 2, the dots are left behind.
In FIG. 2, the portion immediately to the left of the arrow is black before fixing in FIG. 1, but in FIG. 2 after fixing, a rounded and isolated point is recognized. This indicates that the toner has been absorbed into the lump and disappeared as described above.
Similarly, in FIG. 3B after fixing, the left two circles are isolated, but this is because the toner around the dots in FIG. 3A becomes a lump. It is the result of being absorbed, gone and whitened.
Similarly, in FIG. 4, the toner image that was one block in FIG. 4A before fixing is the two round parts on the left side (although the circles are connected) in FIG. 4B after fixing. The toner in the white part is left in the lump, leaving the round part on the right side.

  2, 3 (b), and 4 (b), it can be seen that the edge of the fixed image is generally rounded, and that it also shrinks (rounds). It can be said that it is one that supports it. Such a rounded phenomenon is not observed in the comparative examples described later.

On the other hand, FIG. 5 shows an image before fixing using comparative toner 1 (black), and FIG. 6 shows the image after fixing.
In FIG. 5, some toner lumps are observed. In the lower part of the figure, the toner in the lower part of the large lump is sparsely present, but in FIG. 6 after fixing, the toner is crushed and connected. Also, the hole in the center left block is completely closed. However, all of them are crushed at the place before fixing, and no toner is lost from the place before fixing. That is, when FIG. 5 and FIG. 6 are compared, all the toner is fixed and crushed on the spot, and there is no toner that has moved or rounded and disappeared. That is, there is no shrinking (rounding) function.
7 to 8 are also slightly smaller images, but are images before and after another fixing of the comparative toner 1, (a) is a toner image before fixing (after transfer), and (b) is an image after fixing. is there. Like FIG. 5 and FIG. 6, the toner is crushed on the spot and rounded as shown in FIG.
Although not directly related to the present invention, when the edge (boundary region) of the toner in FIG. 5 is closely observed, a fine particle structure inside the finely pulverized toner can be seen. Moreover, when FIG. 6 after fixing is seen, the fine particle structure can be found also in the boundary region. That is, it can be said that the particle structure of the conventional toner has hardly changed even after fixing. In FIGS. 7 to 8 (a) and (b), a fine particle structure is recognized as in FIGS.
On the other hand, in FIGS. 1 to 4 of the toner of the present invention, no internal structure is recognized before or after fixing.

As described above, in the toner of the present invention, the black portion (portion where the toner is present) in the image before fixing is lost after fixing, and the toner in this portion is absorbed into the lump by fixing and is lost. Is shown.
As described above, the toner of the present invention has a characteristic of forming a so-called shrinkable film and exhibiting self-repairing properties to form an image.

  According to the electrophotographic dry toner and the electrophotographic image forming method of the present embodiment, the scattered toner scattered around the toner image on the transfer material composed of at least the binder resin and the colorant is converted into the toner image at the time of heat fixing. Self-healing electrophotographic dry toner characterized by self-healing that combines and absorbs, and in the transfer process, on the transfer material after transfer, the image transferred onto the transfer material is called image dust In addition, it is possible to prevent image distortion due to generation of dust toner around the latent image other than the target image, and to improve the image quality in a self-repairing manner.

2 is a micrograph (magnification 1000 times) before fixing with the toner of Example 1. FIG. FIG. 3 is a micrograph showing that self-repairability after fixing with the toner of Example 1 was developed (particularly, the portion of the arrow in FIG. 1 is rounded by the application of heat and pressure during fixing as indicated by the arrow in FIG. 2. 1), the black portion of the arrow in FIG. 1, that is, the portion with the toner is white, and is absorbed by the lump above the arrow. FIG. 4 is another micrograph showing the self-repairing property of the toner of Example 1, (a) is before fixing, (b) is after fixing (in FIG. As in FIGS. 1 and 2, the toner in the lower black portions 1 and 2 in the figure is absorbed by the lump and disappears due to the toner rounding property as in FIGS. FIG. 4 is another micrograph showing the self-repairing property of the toner of Example 1 (a) is before fixing, and (b) is a photograph showing an example after fixing (1 to 1 in FIG. 3 is the same as in FIGS. 1 and 2 because of the roundness of the toner as in FIGS. 1 and 2, the toner at the upper right of parts 1 and 2 and the left of 3 is the center. It is not absorbed by the lump.) 3 is a photomicrograph before fixing with comparative toner 1. FIG. 3 is a micrograph after fixing with comparative toner 1 (after fixing, toner is not absorbed and shows that the toner is fixed in its place). It is the microscope picture before and behind fixation of the comparison toner 1, (a) is a thing before fixing, (b) is the photograph after fixing. It is the microscope picture before and behind fixation of the comparison toner 1, (a) is a thing before fixing, (b) is the photograph after fixing.

Claims (4)

A toner having at least a binder resin having a mixture of ethylene acetate vinyl ester and an ionomer derived from a copolymer of ethylene and methacrylic acid, and a colorant , wherein the target image developed with the toner and the periphery of the target image The toner image including the scattered toner scattered on the surface is heated and fixed, and the toner forms a molten lump, and the scattered toner is melted and shrunk so that the toner image self-repairs to the target image. A self-healing electrophotographic dry toner characterized by the above. The mixing ratio of the mixture is, by weight, an ionomer derived from a copolymer of ethylene acetate vinyl ester: ethylene and methacrylic acid = 1: 1 to 1: 4. Dry toner for electrophotography. The binder resin, electrophotographic dry toner as claimed in claim 1 or 2, characterized in that it further comprises a low surface energy resin. An electrophotographic image forming method using the electrophotographic dry toner according to any one of claims 1 to 3.

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