JPH04328572A - Toner for electrophotography - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner used for developing electrostatic latent images in electrophotography and the like. Conventionally, as an electrophotographic method, U.S. Patent No. 229
The method described in No. 7691 is well known, but this generally utilizes a photoconductive insulator (such as a photocondrum) and generates a uniform electrostatic charge on the photoconductive insulator by corona discharge or the like. An electrostatic latent image is formed by irradiating a light image onto the photoconductive insulator by various means, and then the latent image is developed and visualized using a fine powder called toner. After transferring the toner image to paper etc. according to the
A toner image is fixed on a recording medium such as paper by means such as pressure, heating, irradiation with a solvent, steam, light, etc. to obtain a copy.

0002

[Prior Art] Toners for developing these electrostatic latent images have conventionally been prepared by dispersing a coloring agent such as carbon black in a binder resin made of natural or synthetic polymeric substances to a thickness of about 5 to 20 μm. Finely ground particles are used. Such toner is usually used alone or mixed with a carrier such as iron powder or glass beads to develop an electrostatic latent image.

[0003] When the toner is used alone for development (one-component development method), the toner usually contains magnetic powder,
The toner is frictionally charged by friction with the wall surface of the developing device, a member such as a magnet roll in the developing device, and is further held on the magnet roll by the magnetic force of the magnet roll, causing the magnet roll to rotate. This brings the toner to the area of the latent image on the photoconductive insulator, and development occurs when the charged toner adheres to the latent image by electrical attraction.

[0004] Furthermore, when using a mixture of carrier and toner (two-component development method), the developer consisting of toner and carrier is mixed and stirred in a developing device and is triboelectrically charged, so that the toner is supported on the carrier. The charged toner is transported to the latent image area on the photoconductive insulator, and development is performed by selectively adhering only the charged toner to the latent image due to electrical attraction. In this case as well, the toner image is formed only with toner.

In the case of a two-component development method, iron powder or other ferromagnetic particles are usually used as the carrier, and in this case, the magnetic particles are held by a magnet roll in the developing device and moved by a magnetic brush. The rotation of the magnetic roll carries the magnetic brush to the latent image area on the photoconductive insulator, thereby transporting toner to the latent image area.

On the other hand, as a binder resin used in toner, a low polymer polymer generally called an oligomer is often used. Oligomers have low molecular weights, low melt viscosity, and good thermal stability, so they are widely used as binder resins for electrophotographic toners. Further, the fixing is to melt the powder image of the toner and fix it to the recording paper, and the various methods described above are available for this purpose. Among these methods, flash fixing, which is a typical type of optical fixing, is a method in which fixing is performed using flash light from a discharge tube such as a xenon flash lamp, and has the following characteristics. (1) Since it is non-contact fixing, the resolution of the image during development does not deteriorate. (2) There is no waiting time after the power is turned on, and a quick start is possible. (3) Even if recording paper gets jammed in the fixing device due to system failure, no fire will occur. (4) Fixing is possible regardless of the material or thickness of the recording paper, such as glued paper, preprinted paper, or paper of different thickness.

The process by which toner adheres to recording paper by flash fixing is as follows. As described above, when a toner image is transferred to recording paper, it adheres to the recording paper as a powder to form an image, and if rubbed with a finger, for example, the image will collapse. When the toner is irradiated with a flash of light from a discharge tube such as a xenon flash lamp, the toner absorbs the energy of the flash, its temperature rises, it softens and melts, and adheres to the recording paper.

[0008] After the flash of light ends, the temperature decreases and the image solidifies into a fixed image, completing the fixing process.The fixed image fixed to the recording paper will not disintegrate even if it is rubbed with a finger, for example. What is important in flash fixing is that the toner melts and adheres firmly to the recording paper, and for this purpose the toner emits light energy, including thermal energy that is dissipated into the outside world and does not contribute to temperature rise. It must absorb and melt sufficiently from the flash.

[0009] Therefore, if the applied light energy is insufficient, the toner cannot be sufficiently melted and satisfactory fixing performance cannot be obtained. On the other hand, if the light energy is too strong, the viscosity of the toner decreases rapidly. At this time, when the surface tension acting on the toner overcomes the viscosity, the toner in the printing area aggregates and moves.
As shown in FIG. 1, a white spot phenomenon called void 5 occurs in the image, causing a decrease in image density.

[0010] Therefore, the toner for flash fixing needs to be free from voids due to movement of the toner. In FIG. 1, 2 is a recording paper, 3 is a flash of light, and 4 is a fixed image. Conventionally, epoxy resins such as bisphenol A diglycidyl ether polymer and polyester resins such as polyethylene terephthalate have been commonly used as binder resins for flash fixing toners.

[0011]

[Problems to be Solved by the Invention] However, in such conventional flash fixing toners, when the above-mentioned resin is used as a binder resin, in order to obtain good fixing properties, it is necessary to compare the molecular weight. It is necessary to use oligomers with a low melting point and a low melting point. However, when such oligomers are used, the melt viscosity is low, and when the toner is melted by flash light irradiation, the toner aggregates and solidifies due to the force of toner movement caused by surface tension. The occurrence of voids was unavoidable.

In order to prevent this, it is necessary to increase the melt viscosity of the binder resin to prevent the toner from moving and causing white spots. As a method to increase melt viscosity,
(1) Increasing the degree of polymerization of the binder resin, (2) Introducing relatively long side chains of C4 or more into the main chain structure of the binder resin, (3) Introducing crosslinks between the main chain structures of the binder resin. , etc. can be considered.

However, in the methods (1) and (3), although the melt viscosity can be increased, the melting point also increases, so although the generation of voids can be prevented, the fixing performance is often impaired. Further, in method (2), the melt viscosity can be increased without significantly increasing the melting point, but in this case, the glass transition point of the binder resin is lowered, so blocking resistance is often extremely impaired.

The present invention has been made in view of these conventional problems, and aims to provide a toner for flash fixing that has excellent void resistance without impairing fixing properties and blocking resistance. The purpose is

[0015]

[Means for solving the problem] As a result of study, the inventors found that
In order to prevent a decrease in fixing properties due to an increase in the melting point of the binder resin or a decrease in blocking resistance due to a decrease in the glass transition point, even when a binder resin with a relatively low melt viscosity is used, at least the surface tension or binder resin We have discovered that the generation of voids due to aggregation can be suppressed by using a toner that reduces the surface tension by dispersing a substance that reduces the intermolecular force that acts between the molecules that make up the toner, that is, a surface tension reducing agent. The present invention has been accomplished.

The polymer used for the surface tension reducing agent is a perfluoroalkyl polyester represented by the following general formula, which is a fluorosurfactant having a hydrophilic group and a hydrophobic group and exhibiting surface activity.

[0017]

[Case 2]

R1 :H or F R2 :H or F R3 :H or alkyl group Even if the fluorine-based surfactant used as the surface tension reducing agent is added at the stage of polymerizing the binder resin from the monomer, it will not affect the toner constituent materials. It may be added at the stage of melting and kneading.

However, when the surface tension reducing agent is added during the polymerization stage of the binder resin, the surface tension reducing agent does not thermally decompose even at the synthesis temperature of the binder resin, does not inhibit the polymerization of the binder resin, or induces side reactions. Limited to materials. The surface tension of fluorine-based surfactants is 5 to 25 dy at 23°C.
ne/cm (0.1 wt% aqueous solution), and its thermal decomposition temperature is preferably 230°C or higher.

The amount of the surface tension reducing agent used in the present invention is determined based on the material of the surface tension reducing agent and the surface tension of the binder resin. , 15 dyne/cm 2 or less, which corresponds to 0.01 to 5.00 wt% based on the toner weight. The reason why the amount of fluorosurfactant added must be 5.00 wt% or less is that if it is more than this, the melt viscosity becomes too low due to the melt viscosity reduction effect of the surface tension reducing agent, and the void prevention ability decreases. This is because it ends up happening.

[0021] The reason why the content must be 0.01 wt% or more is that if it is less than 0.01 wt%, the effect of void prevention ability due to surface tension reduction cannot be expected. The toner binder used in the present invention may be any resin used in electrophotography, and for example, styrene acrylic, epoxy resin, polyester resin, etc. can be used alone or in combination.

[0022] When a binder resin in which a surface tension reducing agent is dispersed is used in combination with another binder resin, if the required amount of surface tension reducing agent is added as a whole, the surface tension reducing agent is added to only one binder resin. A resin to which is added may also be used. The toner used in the present invention can be manufactured by a conventionally known method. That is, a binder resin, a coloring agent, a surface tension reducing agent, carbon, a charge control agent, etc., if necessary, are melt-kneaded and uniformly dispersed using, for example, a pressure kneader, roll mill, extruder, etc., and then finely dispersed using, for example, a jet mill. The desired toner can be obtained by pulverizing the toner and classifying it using a classifier, for example, a wind classifier.

[0023]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto. The evaluation results of toners prototyped in Examples and Comparative Examples are shown in the attached table. Example 1 Epoxy resin (bisphenol A) was used as the binder resin.
Diglycidyl ether, epoxy equivalent weight 900-1000
), 2 parts by weight of perfluoroalkyl polyester (manufactured by Sumitomo 3M) as a surface tension reducing agent, and carbon black (Black Pearls L; average particle size 0.024 μm, as a coloring agent).
5 parts by weight of specific surface area 138 m2/g; manufactured by Cabot Corporation) and 3 parts by weight of nigrosine dye (Oil Black BY, manufactured by Orient Chemical Co., Ltd.) were added, and the mixture was heated at 130°C in a pressure kneader for 30 minutes.
The mixture was melted and kneaded for 0 minutes to obtain a toner mass.

[0024] The cooled toner mass was made into coarse toner having a particle size of about 2 mm using a rotoplex pulverizer. Next, the coarse toner is finely pulverized using a jet mill (PJM pulverizer, manufactured by Nippon Pneumatic Industries), and the pulverized product is classified using an air classifier (manufactured by Alpine) to form positively charged toner with a particle size of 5 to 20 μm. I got an A. Toner A5 parts by weight, unshaped iron powder TSV100/200 (manufactured by Nippon Iron Powder) 95 as carrier
A developer consisting of parts by weight was prepared and FACOM-6715
D. A printing test was conducted using a modified laser printer, and the optical density of the image was measured using a Macbeth PCM meter. Note that the occurrence of voids was visually observed. Further, the surface tension of Toner A was measured at 200° C. using a surface tension measuring device (Digiomatic ESB-V, manufactured by Kyowa Kagakusha Co., Ltd.).

As a result of the printing test, Toner A had excellent void resistance and the printing density was 1.0. Further, the surface tension of toner A was 13 dyne/cm 2 . Example 2 As a binder resin, polyester (polyethylene terephthalate, weight average molecular weight 100
Further, 5 parts by weight of carbon black and 3 parts by weight of nigrosine dye were added as colorants, and the mixture was melt-kneaded at 130° C. for 30 minutes using a pressure kneader to obtain a toner mass.

[0026] The cooled toner mass was made into coarse toner having a particle size of about 2 mm using a rotoplex pulverizer. Next, the coarse toner was pulverized using a jet mill, and the pulverized product was classified using an air classifier to obtain positively charged toner B having a particle size of 5 to 20 μm. As a result of printing evaluation, Toner B had excellent void resistance and print density was 1.1. Further, the surface tension of toner B was 12 dyne/cm 2 . Example 3 As a binder resin, 60 parts by weight of styrene acrylic to which 2 parts by weight of perfluoroalkyl polyester was added based on the weight of the resin, and a polyester resin (polyethylene terephthalate, weight average molecular weight 1000) to which no fluorine surfactant was added. Using 30 parts by weight, 3 parts by weight of carbon black (Black Pearls L) and 3 parts by weight of nigrosine dye were added as colorants, and the mixture was melt-kneaded at 130° C. for 30 minutes using a pressure kneader to obtain a toner mass.

The cooled toner mass was made into coarse toner having a particle size of about 2 mm using a rotoplex mill. Next, the coarse toner was pulverized using a jet mill (PJM pulverizer), and the pulverized product was classified using an air classifier (manufactured by Alpine) to obtain positively charged toner C having a particle size of 5 to 20 μm. As a result of printing evaluation, Toner C had excellent void resistance and print density was 1.1. Also, the surface tension of toner C is 12
dyne/cm. Comparative Example 1 Toner D was obtained in the same manner as in Example 1, except that no surface tension reducing agent was added during toner melt-kneading. As a result of a printing test and surface tension measurement conducted using the same method as in Example 1, it was found that the printing of this toner had many voids and the printing density was 0.
．． It was 8. Moreover, the surface tension of the toner D is 25dy
It was ne/cm. Comparative Example 2 Toner E was obtained in the same manner as in Example 2, except that a fluorine-based surfactant as a surface tension reducing agent was not applied to the binder resin. As a result of performing a printing test and surface tension measurement using the same method as in Example 1, it was found that the printing of this toner E had many voids and the printing density was 0.7. Also, toner E
The surface tension of was 23 dyne/cm. Comparative Example 3 Using 92 parts by weight of epoxy resin as the binder resin,
On the other hand, toner F was obtained in the same manner as in Example 1 except that 3 parts by weight of a fluorosurfactant was used as a surface tension reducing agent. As a result of performing print evaluation and surface tension measurement using the same method as in Example 1, it was found that the print of this toner had a large number of voids and the print density was 0.7. Further, the surface tension of Toner F was 10 dyne/cm 2 . Comparative Example 4 Toner G was obtained in the same manner as in Example 2, except that no fluorine-based surfactant was added as a surface tension reducing agent to the styrene acrylic. As a result of performing a printing test and surface tension measurement using the same method as in Example 1, it was found that the printing of this toner G had many voids and the printing density was 0.6. Further, the surface tension of Toner G was 33 dyne/cm 2 .

[0028]

[Table 1]

[0029]

[Effects of the Invention] As explained above, according to the present invention, fixing properties and anti-blocking properties are not impaired;
A toner for flash fixing having excellent void resistance can be obtained.

[Brief explanation of drawings]

[Figure 1] Illustration of void generation

[Explanation of symbols]

1: Toner 2: Recording paper 3: Flash 4: Fixed image 5: Void

Claims (4)

[Claims] 1. An electrophotographic toner using a binder resin, which contains a surface tension reducing agent in the binder resin.
An electrophotographic toner characterized by using a fluorine-based surfactant represented by the following general formula. [Formula 1] R1 :H or F R2 :H or F R3 :H or an alkyl group 2. The toner for electrophotography according to claim 1, wherein the amount of the fluorine-based surfactant used in the toner is 0.01 to 5.00 wt%. 3. The fluorosurfactant used in the toner has a surface tension of 5 to 25 dyne/cm at 25°C.
The toner for electrophotography according to claim 1, wherein the toner is a 0.1 wt% aqueous solution. 4. The electrophotographic toner according to claim 1, wherein the fluorosurfactant used in the toner has a thermal decomposition temperature of 230° C. or higher.