JP2001117261A - Electrophotographic toner and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize the material and composition of an electrophotographic toner so as to obtain a white-and-black image with >=5 gloss (85 deg. gloss). SOLUTION: The electrophotographic toner contains 100 pts.wt. of a styrene- acrylic resin, 1 to 10 pts.wt. of a black coloring agent,,and 1 to 8 pts.wt. of at least one kind of wax selected from polyolefin waxes having 1000 to 20000 mol.wt. and containing polyethylene, polypropylene and ethylene-propylene polymer. Especially, the styrene-acrylic resin has two mol.wt. peaks in the mol.wt. distribution. The peak in the high mol.wt. side is >=50×104, and the peak in the low mol.wt. side is <=1×104. Especially, one kind of wax having 90 to 110 deg.C melting point and selected from the polyolefin waxes is internally added.

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 in an image forming apparatus employing an electrophotographic system, and to an image forming apparatus using the toner.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic method using a Carlson process has been widely used for image formation using toner. An image forming apparatus employing an electrophotographic method generally includes a charging device, an exposure device, a developing device, a transfer device, a fixing device, a cleaning device, and a charge removing device around a photosensitive drum having a photosensitive layer on a surface. It is configured by being arranged sequentially. Image formation by such an image forming apparatus is performed as follows.

First, in a dark place, the surface of a photosensitive drum is uniformly charged by a charging device. Next, an original image is projected onto the surface of the photoconductor drum by the exposure device, thereby removing the charge of the light-irradiated portion, thereby forming an electrostatic latent image on the surface of the photoconductor drum. Next, the toner charged in the polarity opposite to the charging electric field on the surface of the photosensitive drum and stored in the developing device is adhered to the electrostatic latent image to form a visible image. Next, a recording material such as paper is superimposed on the visible image, and a corona discharge is performed by a transfer device from the back surface of the recording material to give a charge having a polarity opposite to that of the toner, so that the toner image is transferred to the recording material. After the transfer, the toner image is fixed on the recording material by heat and pressure by a fixing device, and is made a permanent image. on the other hand,
The residual toner remaining on the photosensitive drum without being transferred to the recording material is removed by a cleaning device, and the electrostatic latent image on the photosensitive drum is discharged by a discharging device. Thereafter, the above-described steps starting from the charging of the photosensitive drum are repeated again, so that continuous image formation is performed.

[0004] The toner used in the above-mentioned image formation is a colored powder for forming a visible image and a powder having a charging function and a fixing function to a recording material. Functions are provided. Such a toner is conventionally manufactured by a pulverization method or a polymerization method. In the pulverization method, a colorant, a charge controlling agent and a wax as an offset preventing agent are melt-kneaded with a thermoplastic resin, solidified by cooling, then pulverized and classified to produce a toner. As the polymerization method, a suspension polymerization method and an emulsion polymerization method are typical.

Further, different types of toner are used depending on the type of a copying machine or a printer. This is due to differences in fixing speed and fixing temperature between models. That is, at the time of fixing, the surface of the fixing roller provided with the heating unit and the toner image come into contact with each other under pressure while the toner is fused. At this time, a part of the toner adheres to the surface of the fixing roller, and the toner is re-transferred to the recording material at the next fixing time, thereby soiling the recording material. The so-called offset phenomenon is affected by the fixing speed and the fixing temperature. It is. In the future, it is expected that the image forming speed of copiers and printers will be further increased, and in the fixing process, an offset resistance having a wide fixing temperature range applicable from a low image forming speed to a high image forming speed. It is desired to develop a toner having excellent performance.

In recent years, digital color copying machines and printers have been put into practical use, and high performance is required for color toners in addition to fixing performance. For example, Japanese Patent Application Laid-Open No. 10-282822 requires high color reproducibility when multicolor toner is sufficiently mixed in the fixing step and high transparency in an overbed projector film (OHP) image. 63-300
In Japanese Patent Publication No. 254, high glossiness is required to enhance a printed picture portion. Therefore, Japanese Patent Application Laid-Open No. 10-282822 discloses an image forming technique capable of forming a color image having excellent low-temperature fixability, anti-offset property, transparency of an OHP image, and stable glossiness. .

[0007]

However, Japanese Patent Application Laid-Open Publication No.
Japanese Patent Application Laid-Open No. 0-282822 describes that it is desirable to reduce the glossiness of black-and-white toner because high glossiness makes characters difficult to read. However, the preferred glossiness range is not specifically described. Further, Japanese Patent Application Laid-Open No. 63-30 / 1988
Japanese Patent No. 0254 discloses that the glossiness (60-degree gloss) of a character portion is desirably 10% or less, but does not describe the lower limit. That is, in the prior art, the glossiness of the black and white toner is not so conscious. Incidentally, as described in JP-A-63-300254, a high gloss indicates that the surface of the toner layer is smooth, although there are, of course, factors in terms of actual gloss. It is considered that the low gloss indicates that the surface of the toner layer is uneven.

An object of the present invention is to provide a glossiness (85-degree gloss).
The object of the present invention is to provide an electrophotographic toner having an optimized material and composition for obtaining a monochrome image of 5 or more, and an image forming apparatus using the same.

[0009]

According to the present invention, there are provided a styrene-acrylic resin of 100 parts by weight, a black colorant of 1 to 10 parts by weight, a molecular weight of 1,000 to 20,000, polyethylene, polypropylene and ethylene-based resin. An electrophotographic toner comprising 1 to 8 parts by weight of at least one kind of wax selected from polyolefin waxes containing a propylene polymer.

According to the present invention, a black-and-white image having a glossiness (85-degree gloss) of 5 or more can be formed by using the toner composed of the above-described materials and compositions. According to such a black-and-white image, a wide non-offset area can be obtained, a high fixing strength can be obtained, and a sense of comfort can be given to the user. In evaluating the performance of the black and white toner, the glossiness is a large scale. That is,
The fact that the surface of the toner layer is smooth is a result of the fact that the toner is smoothly peeled off from the fixing roller provided with the heating means, and that the surface of the toner layer is uneven is that the toner is hardly peeled off from the fixing roller. Is the result of this. In other words, high gloss indicates that the toner is excellent in offset resistance and fixability. Also, high gloss means that the surface of the toner layer is smooth, which can reduce diffused reflection of light, has a good appearance, and gives the user a sense of comfort.

If the glossiness is too high, characters are difficult to read, which may cause fatigue of the eyes of the user.
When the glossiness is less than 5, the non-offset area of the toner is narrow, the fixing property is low, the usable fixing device is greatly restricted, the appearance is poor, and the user is likely to feel uncomfortable.

In the present invention, the styrene-acrylic resin has two molecular weight peaks in the molecular weight distribution, the molecular weight peak on the high molecular side is 500,000 or more, and the molecular weight peak on the low molecular side is 10,000 or less. It is characterized by being.

According to the present invention, the styrene-acrylic resin constituting the toner has a molecular weight peak as described above. Therefore, a black-and-white image having a gloss of 5 or more can be reliably formed, a wide non-offset region can be obtained, a high fixing strength can be obtained, and a sense of comfort can be given to the user.

Further, the present invention provides the styrene-acrylic resin, which has a melting point of 90 ° C. to 110 ° C.,
It is characterized in that one kind of wax selected from polyethylene, polypropylene and polyolefin-based wax containing ethylene-propylene polymer is internally added.

According to the present invention, the above-mentioned wax is internally added to the styrene-acrylic resin constituting the toner. Therefore, even if it does not have the above-mentioned molecular weight peak, a black and white image having a glossiness of 5 or more can be reliably formed by adding wax internally.
A wide non-offset region can be obtained, a high fixing strength can be obtained, and a sense of comfort can be given to the user.

According to the present invention, there is provided an image forming apparatus for forming an image by an electrophotographic method using an electrophotographic toner, wherein the toner is the above-mentioned toner.

According to the present invention, the use of the toner described above facilitates temperature control of the fixing device. Also,
Since the releasability of the toner is extremely high, traces of the peeling nail on the image are rarely left, and the fixing roller and the peeling nail are hardly stained. Therefore, a black-and-white image having a gloss level of 5 or more can be formed stably, which leads to an improvement in the durability of the fixing device.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION An electrophotographic toner used for forming an image by an electrophotographic method according to the present invention comprises 100 parts by weight of a styrene-acrylic resin, 1 to 10 parts by weight of a black colorant, and 1000 to 20,000, and contains 1 to 8 parts by weight of at least one kind of wax selected from polyolefin waxes including polyethylene, polypropylene and ethylene-propylene polymer.

The toner is sufficiently mixed with a styrene-acrylic resin, a colorant and a wax, and a charge controlling agent by a mixer such as a Henschel mixer or a super mixer, melt-kneaded by a twin-screw kneader, and then jet-milled. It is obtained by crushing and classifying. The volume average particle size of the toner is about 5 μm to 15 μm. In addition, if necessary, inorganic fine particles may be added, adhered by a mixer such as a Henschel mixer or a super mixer, and uniformly dispersed.

Examples of usable styrene-acrylic resins include styrene-methyl acrylate copolymer,
Styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer and styrene- α-methyl methacrylate copolymer.

Particularly, as the thermal characteristics of the styrene-acrylic resin, those having a glass transition point Tg in the range of 40 ° C. to 70 ° C. are preferable. A resin having a glass transition point Tg of 40 ° C. or lower is not preferable because the possibility of melting and agglomeration of toner particles when the temperature in the image forming apparatus rises is high. Further, a resin having a glass transition point Tg of 70 ° C. or more
It is not preferable because the fixing performance is inferior and cannot withstand actual use.

Further, the styrene-acrylic resin has two molecular weight peaks in the molecular weight distribution, the molecular weight peak on the high molecular side is 500,000 or more, and the molecular weight peak on the low molecular side is 10,000 or less. preferable.

The styrene-acrylic resin is one kind of wax selected from polyethylene, polypropylene and polyolefin wax containing ethylene-propylene polymer, and has a melting point of 90 ° C. to 110 ° C.
Preferably, the wax is internally added, that is, the wax is included in the resin during the resin production process, or the wax is added to the toner before the kneading process in the toner production so that the wax is included in the toner.

Examples of usable colorants include carbon black, iron black, alloy azo dyes and various other oil-soluble dyes and pigments.

The wax has a molecular weight of 1 as described above.
000 to 20,000, and at least one wax selected from polyolefin waxes including polyethylene, polypropylene and ethylene-propylene polymer is used. The wax is used in an amount of 1 to 8 parts by weight based on 100 parts by weight of the resin component. If the amount of the wax is less than 1 part by weight, the peeling property of the toner from the fixing roller is poor, and depending on the fixing device, there is a high possibility that traces of peeling nails are generated on the recording material. When the amount of the wax is 8 parts by weight or more, the glossiness and the anti-offset property are not greatly improved even if the wax is added more than that.

There are two types of charge control agents, one for controlling positive charge and the other for controlling negative charge. For example, azo dyes, carboxylic acid metal complexes, quaternary ammonium compounds, and nigrosine dyes can be used. The charge control agent is a resin component 10
It is preferable to add 0.1 to 5 parts by weight to 0 part by weight.

Examples of the inorganic fine particles to be added as necessary include fine particles of metal oxides such as silica, titanium, alumina, magnetite and ferrite, and fine particles of metal nitride such as silicon nitride and boron nitride. In addition, these fine particles may be subjected to a surface treatment with a silane coupling agent such as dimethyldichlorosilane or amylosilane, a surface treated with a silicone oil, or a fluorine-containing component. These may be used alone or in combination. Specifically, silica is added to ensure the fluidity of the toner and to promote the chargeability. Magnetite is added to polish the photosensitive drum.

In addition to the toner described above,
An image forming apparatus that forms an image by an electrophotographic method using the electrophotographic toner also belongs to the scope of the present invention.

Hereinafter, the present invention will be described in detail with reference to examples. However, the following examples are merely examples, and the present invention is not limited to these examples.

[0030]

First, a method for producing the toner of the present invention will be described. Samples A to J shown in Tables 1 and 2 were used as the styrene-acrylic resin. As a coloring agent, carbon black (330R, manufactured by Cabot Corporation)
Was used. As the wax, polyethylene (manufactured by Clariant Japan, PE130) and polypropylene (manufactured by Mitsui Chemicals, Inc., NP-505) were used. As the charge control agent, S-34 manufactured by Hodogaya Chemical Industry Co., Ltd. was used.
In addition, magnetite (KBC-100, manufactured by Kanto Denka Co., Ltd.) was used as the metal oxide fine particles.

8 parts by weight of a coloring agent, 1.0 part by weight of a polyethylene wax, 1.5 parts by weight of a polypropylene wax, 1 part by weight of a charge controlling agent and 1 part by weight of magnetite are added to 100 parts by weight of a styrene-acrylic resin. Add 3 parts by weight, mix well with a supermixer (V-20, manufactured by Kawada), and use a twin-screw kneader (PCM-3, manufactured by Ikegai Iron Works).
0), and the mixture was pulverized and classified by a jet pulverizer (IDS-2, manufactured by Nippon Pneumatic Industries, Ltd.). The volume average particle size of the toner thus obtained was about 7.5 μm. 0.7 parts by weight of silica fine particles (R972, manufactured by Nippon Aerosil Co., Ltd.) and magnetite (EPT-, manufactured by Toda Kogyo Co., Ltd.) were added to the obtained toner.
0.5) was added externally, that is, uniformly adhered on the surface of the obtained toner to complete the production of the toner.

Next, an image was formed using the toner produced as described above, and the solid image (black solid image) was evaluated for glossiness (85 ° gloss), non-offset area, and fixing strength. In addition, glossiness is JIS Z
8741 and JIS P8142.
Specifically, the fixing temperature is 190 ° C., the fixing speed is 175 mm / sec, and the fixing speed is 175 mm / sec on catsa paper (weighing 75 g / m ² ).
Solid images were formed at 05 mm / sec and 225 mm / sec, and measured using VG-2000 manufactured by Nippon Denshoku Industries Co., Ltd. at an incident angle θ = 85 °, an average value at five locations was obtained, and this was repeated three times. The average value was defined as the glossiness.

In the non-offset region, a fixing device (AR-S400, manufactured by Sharp Corporation) was used, and the fixing temperature was set to 130 ° C. to 2
It changes within the range of 60 ° C., and the fixing speed is 175 mm / sec.
c, fixation is performed at 205 mm / sec and 225 mm / sec, and the case where no offset is generated by visual evaluation is marked as “」 ”. The case where the offset is slightly generated and the offset is not known unless carefully observed. Was evaluated as “△”, the case where the offset was clearly visible at a glance was evaluated as “×”, and the case where the offset was slightly generated and had no problem in use was evaluated as “△ Δ”.

The fixing strength was evaluated based on the minimum residual ratio (%) and the residual ratio (%) when the image density ID was 1.3. Specifically, first, a copying machine (AR-S33 manufactured by Sharp Corporation) is used.
0) to form an unfixed gray scale chart (defined by Sharp Corporation) on catsa paper, and then use a fixing device (AR-S400, manufactured by Sharp Corporation) to adjust the fixing temperature to 160.
° C and 190 ° C, and the fixing speed is 175 mm / sec.
c, fixing was performed at 205 mm / sec and 225 mm / sec. Subsequently, the ID before and after the rubbing test in which the eraser with a load of 1 kg was reciprocated three times was measured using a Macbeth densitometer (RD-914, manufactured by Macbeth), and the residual ratio was determined from the change in ID. Point I
Using D, a graph was created with the residual ratio on the vertical axis and the ID before rubbing on the horizontal axis. The minimum remaining rate is the minimum value of the graph that draws a downwardly convex curve.

FIG. 1 is a graph showing the correlation between the glossiness of a sample and the non-offset region. A relational expression of Y = 0.0486X + 1.8235 is established between the glossiness and the non-offset region, and a correlation coefficient R ² = 0.7891 and R =
0.8883, indicating a correlation between the two. That is, the gloss and the temperature range of the non-offset region have a substantially linear relationship, and it can be seen that the gloss can be a large scale for evaluating the offset resistance.

Table 1 shows the evaluation results of the glossiness, the non-offset area, and the fixing strength of Samples A to F. Sample D has low gloss, despite the non-offset area being comparable to sample E. This is probably because the fixing strength of Sample D is inferior to that of Sample E. That is, it can be seen that the glossiness is an index for comprehensively evaluating not only the offset resistance but also the offset resistance and the fixability. Further, increasing the degree of gloss to some extent means that the surface of the toner layer becomes smooth, and irregular reflection of light is reduced, the appearance is good, and the user can be provided with comfort.

[0037]

[Table 1]

From the above results, it can be said that a glossiness of 5 or more is required to obtain a toner which is excellent in offset resistance and fixability, has a good appearance in an image, and can provide a user with a peace of mind.

Next, the results of the study of the molecular weight composition in the styrene-acrylic resin will be described. The results are shown in Table 1 above. The blanks in Table 1 indicate that the measurement was not performed because the offset resistance was poor. From the evaluation results in Table 1, in order to achieve a gloss of 5 or more by designing the molecular weight of the resin, the styrene-acrylic resin particularly has two molecular weight peaks in the molecular weight distribution, and the molecular weight peak on the polymer side is It can be seen that a styrene-acrylic resin having a molecular weight peak of 500,000 or more and a low molecular weight peak of 10,000 or less is preferable.

Next, the case where a styrene-acrylic resin internally containing a polyolefin wax is used will be described. As the polyolefin-based wax, one type of wax selected from polyethylene, polypropylene, and polyolefin-based wax containing an ethylene-propylene polymer, having a melting point of 90 ° C to 110 ° C, was used. Table 2 shows the results. The blanks in Table 2 indicate that the measurement was not performed because the offset resistance was poor. From the evaluation results in Table 2, it can be seen that even when the molecular weight distribution of the resin is not in the above range, glossiness of 5 or more can be obtained by internally adding a polyolefin-based wax having a relatively low melting point.

[0041]

[Table 2]

[0042]

As described above, according to the present invention, 100 parts by weight of a styrene-acrylic resin, 1 to 10 parts by weight of a black colorant, a molecular weight of 1,000 to 20,000, polyethylene, polypropylene and By using an electrophotographic toner comprising 1 to 8 parts by weight of at least one kind of wax selected from polyolefin waxes containing an ethylene-propylene polymer, glossiness (85 degree gloss) is obtained. Can form a black-and-white image of 5 or more, a wide non-offset area and a high fixing strength can be obtained, and a sense of comfort can be given to the user.

According to the present invention, in particular, the molecular weight distribution has two molecular weight peaks, the molecular weight peak on the high molecular side is 500,000 or more, and the molecular weight peak on the low molecular side is 1 or more.
By containing a styrene-acrylic resin of not more than 10,000, a black-and-white image having a gloss of 5 or more can be surely formed.

According to the present invention, in particular, the melting point is 90 ° C.
~ 110 ° C wax, by including a styrene-acrylic resin internally adding one type of wax selected from polyethylene, polypropylene and polyolefin-based wax containing ethylene-propylene polymer, Five or more black-and-white images can be reliably formed, a wide non-offset area can be obtained, a high fixing strength can be obtained, and a sense of comfort can be given to the user.

Further, according to the present invention, by realizing an image forming apparatus using the toner as described above, the temperature control of the fixing device becomes easy, and the releasability of the toner is extremely high. There is little trace of peeling nails left, and there is little soiling of the fixing roller and peeling nails. Therefore, a black and white image having a gloss of 5 or more can be formed stably, which leads to an improvement in durability of the fixing device.

[Brief description of the drawings]

FIG. 1 is a graph showing the correlation between the glossiness of a sample and a non-offset region.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshitaka Urata 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Yuichiro Takei 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp F term in the company (reference) 2H005 AA01 AA06 CA04 CA13 EA03 EA06 EA07 2H077 EA11

Claims (4)

[Claims] 1. 100 parts by weight of a styrene-acrylic resin, 1 to 10 parts by weight of a black colorant, a molecular weight of 1,000 to 20,000, polyethylene,
An electrophotographic toner comprising 1 to 8 parts by weight of at least one kind of wax selected from polypropylene and a polyolefin-based wax containing an ethylene-propylene polymer. 2. The styrene-acrylic resin has two molecular weight peaks in the molecular weight distribution, the molecular weight peak on the high molecular side is 500,000 or more, and the molecular weight peak on the low molecular weight side is 10,000 or less. The electrophotographic toner according to claim 1, wherein: 3. The styrene-acrylic resin is a wax having a melting point of 90 ° C. to 110 ° C., and one kind of wax selected from polyethylene, polypropylene, and a polyolefin-based wax including an ethylene-propylene polymer. 2. The electrophotographic toner according to claim 1, wherein the toner is internally added. 4. An image forming apparatus for forming an image by an electrophotographic method using an electrophotographic toner, wherein the toner is any one of claims 1 to 3. .