JP3449935B2 - Dry toner for electrophotography - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic dry toner, and more particularly to an electrophotographic dry toner which is preferably used as a developer in an image forming apparatus such as a copying machine or a printer which employs a heat roll fixing method. It relates to dry toner.

[0002]

2. Description of the Related Art In recent years, in the above-mentioned image forming apparatus using an electrophotographic system, energy saving (reduction of power consumption) has been made mainly for the purpose of multi-functionalization and cost reduction. There is a demand for speeding up for the purpose of spreading to so-called gray areas located on the border. Therefore, the electrophotographic toner (hereinafter abbreviated as toner) applied to the heat roll fixing method has a low fixing temperature, the toner is transferred to the heat roll after fixing, and the transferred toner is transferred to the next sheet. It is naturally demanded that an offset that would be transferred and contaminate an image does not occur. To meet these requirements, the molecular weight of the binder resin, which is the main component, can be reduced to lower the melting point of the binder resin, or the wax to be contained in the toner can be made to have a relatively low melting point. Attempts have been made to lower the melting start temperature of the toner and improve the low temperature fixability.

[0003]

However, since the binder resin having a low melting point has poor strength, the toner becomes fragile,
With a two-component developer (toner and carrier), the life of the developer is shortened, and with a one-component developer (toner alone), the life of the developing device is shortened due to toner fusion to the developing sleeve. It was Therefore, lowering the melting point of the binder resin has been a practical problem. On the other hand, the low melting wax is
The amount used is such that the toner is easily separated from the toner by the crushing process during manufacturing of the toner and stirring in the developing device, which causes image defects and offset such as deterioration of so-called fog after copying a large number of sheets. There was a limit to. In addition, the reduction of the toner particle size has been studied for the purpose of improving the image quality of the output image of a copying machine, a printer, etc., but in the production of the small particle size toner, the wax desorption phenomenon tends to occur remarkably. Therefore, the amount of the low melting point wax used in the small particle diameter toner is further limited.

Therefore, according to the present invention, a sufficient image density can be obtained without causing image defects such as deterioration of fog, and a high fixing strength can be obtained in spite of the lowering of the fixing temperature, resulting in an offset. It is an object of the present invention to provide a dry toner for electrophotography which can sufficiently obtain a fixing temperature range that does not occur.

[0005]

As a result of various studies on the dry toner for electrophotography, the present inventor has found that adding modified polyethylene to a polyolefin resin having a cyclic structure improves the fixing property of the toner. It has been found that it is extremely effective for expanding the non-offset width. Therefore, the dry toner for electrophotography of the present invention is made based on the above findings, and contains at least a polyolefin resin having a cyclic structure and a modified polyethylene obtained by grafting polystyrene onto polyethylene. It has a feature. Hereinafter, preferred embodiments of the present invention will be described in detail.

[0006]

Toner in DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a polyolefin resin having a cyclic structure, poly polyethylene
In addition to a binder resin and a colorant containing a modified polyethylene grafted with styrene , wax, a charge control agent, etc. can be appropriately added. These materials are mixed in a predetermined composition, melt-kneaded, pulverized, and classified. A powder is produced through the steps described above, and then the powder is mixed with an external additive to carry out surface treatment of the powder. Hereinafter, these suitable materials will be described in detail.

A. Polyolefin resin having a cyclic structure The polyolefin resin having a cyclic structure is, for example, an α-olefin such as ethylene, propylene or butylene, and an alicyclic compound having a double bond such as cyclohexene, norbornene or tetracyclododecene. It is a polymer. The polyolefin having this cyclic structure is a polymer obtained by a polymerization method using, for example, a metallocene-based or Ziegler-based catalyst.

The polyolefin resin having a cyclic structure used in the present invention has a number average molecular weight (hereinafter, abbreviated as Mn) measured by gel permeation chromatography (hereinafter, abbreviated as GPC) of less than 7,500, It is preferably 1000 to 7500, more preferably 3000 to 7500, and the weight average molecular weight (hereinafter abbreviated as Mw) is less than 15000, preferably 1000 to 15
000, more preferably a low molecular weight polyolefin resin (A) having a cyclic structure in the range of 4000 to 15000.
And Mn is 7500 or more, preferably 7500 to 500
00 and Mw is 15,000 or more, preferably 15,000
A mixture with a high molecular weight polyolefin resin (B) having a cyclic structure in the range of 100,000 is preferably used.

In the present invention, the polyolefin resin having a cyclic structure which satisfies the above characteristics may be mixed with other resins. In this case, the ratio of the polyolefin resin having a cyclic structure to the other resin is 1 to 100 for the polyolefin resin having a cyclic structure in the total amount of the polyolefin resin having a cyclic structure and the other resin.
It is preferably 20 to 90% by weight, more preferably 50 to 90% by weight, and if the polyolefin resin having a cyclic structure is less than 1% by weight, it becomes difficult to obtain sufficient fixing strength in low temperature fixing.

Other resins include polystyrene resin, polyacrylic acid ester resin, styrene-acrylic acid ester copolymer resin, styrene-methacrylic acid ester copolymer resin, polyvinyl chloride, polyvinyl acetate,
Polyvinylidene chloride, phenol resin, epoxy resin,
Examples thereof include polyester resins, and those having a melting start temperature (softening point) as low as possible (for example, 120 to 150 ° C.) are preferable for the purpose of improving the fixing performance of the toner.
Further, in order to improve the storage stability, those having a high glass transition point of 65 ° C. or higher are preferable.

In addition, in the total amount of the polyolefin resin having a cyclic structure and the other resin, the content of the high molecular weight polyolefin resin (B) having a cyclic structure is 50% by weight or less in low temperature fixing. It is preferable to obtain high fixing strength.

Further, by introducing a carboxyl group into a polyolefin resin having a cyclic structure by a melt air oxidation method or modification with maleic anhydride, compatibility with other resins and dispersibility of the pigment can be improved. Also, the same improvement can be realized by introducing a hydroxyl group and an amino group by a known method. Furthermore, a polyolefin resin having a cyclic structure, norbornadiene,
Cyclohexadiene, by copolymerization with a diene monomer such as tetracyclododecadiene, or to a polyolefin resin having a carboxyl group-introduced cyclic structure,
By introducing a crosslinked structure by adding a metal such as zinc, copper or calcium, the fixability can be improved.

B. The modified polyethylene resin in the modified polyethylene resins present invention, and it incompatible unnecessarily polyolefin resin having a pre-Symbol cyclic structure, since it has the effect of widening the fixing temperature range in which the offset does not occur, polystyrene polyethylene Limited to grafted copolymers. This graft copolymer has a structure represented by the following chemical formula 1, and is manufactured by Mitsui Chemicals, Inc. under trade names: HW1120H, HW1140H, HW1.
Examples include those marketed as 160H and the like. The modified polyethylene resin has a viscosity average molecular weight of 500.
It is preferable that the melting point is from 3,000 to 3,000 and the melting point is from 90 to 120 ° C. because the low temperature fixability is improved.

[0014]

[Chemical 1]

C. Colorant Colorants include carbon black, nigrosine dye,
Aniline blue, chalco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal and the like are used alone or in combination. These colorants need to be contained in a sufficient proportion so that a visible image having a sufficient image density is formed,
For example, it is preferably contained in a proportion of about 1 to 20 parts by weight with respect to 100 parts by weight of the binder resin.

D. Wax The toner of the present invention may contain a synthetic wax, a petroleum wax or the like in order to lower the melting start temperature of the toner and to improve the low temperature fixability. Examples of synthetic waxes include polypropylene wax and Fischer-Tropsch wax, and examples of petroleum waxes include paraffin wax, microwax, petrotam and the like. In addition, carnauba wax, rice wax, candelilla wax, bees wax and other plant-based, animal-based natural wax, stearic acid amide,
An oil and fat-based synthetic wax such as behenic acid amide and ethylenebisstearylamide may be contained.

E. Charge Control Agent The charge control agent is added to impart polarity to the toner, and is divided into positively charged toner and negatively charged toner.
Of a positively charged toner, nigrosine dye, quaternary ammonium salt, Pi Rijiniumu salt and azine or the like is used. Further, for negatively charged toner, an azo metal-containing complex or a salicylic acid metal complex is used.

F. External Additives External additives are added to control the fluidity, charging properties, cleaning properties, storage properties, etc. of toner, and include silica, alumina, talc, clay, calcium carbonate, magnesium carbonate, titanium oxide, and various resins. Fine particles are used.
This external additive is added at a rate of about 0.3 to 3 parts by weight by post-addition with respect to 100 parts by weight of the toner main component. The surface treatment of the main component powder with an external additive can be carried out using a general agitator such as a turbine type agitator, a Henschel mixer and a super mixer.

The toner of the present invention can be used as particles having a volume average particle diameter of 4 to 20 μm by a step of pulverizing and classifying each of the above materials by heat melting and kneading, and in addition, the toner particles can be obtained by a polymerization method. You may get it.

The toner of the present invention can be used as a non-magnetic one-component developer or a two-component developer toner. Further, the toner of the present invention can be mixed with magnetic powder and used as a one-component magnetic toner, or can be used as a full-color toner.

[0021]

EXAMPLES The present invention will be described in more detail by way of examples. In the following description, "part" means "part by weight". <Example 1> 100 parts of polyolefin resin having a cyclic structure (Mn: 2900, Mw: 20000, Mw / Mn: 6.9, glass transition point: 66 ° C) • Modified polyethylene resin: 3 parts (trade name: HW1120H,・ Mitsui Chemicals Co., Ltd. ・ Carbon black 6 parts (Product name: REGAL330R, Cabot Co.) ・ Chromium-containing dye 1 part (Product name: S-34, Orient Chemical Co., Ltd.) Mix and
After hot melt kneading with a pressure kneader at 120 ° C., the kneaded product was pulverized with a jet mill and classified with a dry airflow classifier to obtain toner particles having an average particle size of 11 μm. Next, 0.3 parts of hydrophobic silica (trade name: R972, manufactured by Nippon Aerosil Co., Ltd.) is mixed with 100 parts of the toner particles by a Henschel mixer to obtain a negatively chargeable dry toner for electrophotography of the present invention. It was The physical properties of the modified polyethylene resin are shown in Table 1 below.

[0022]

[Table 1]

Further, Mn and Mw of the above-mentioned polyolefin resin having a cyclic structure are values measured by GPC under the following conditions. That is, at a column temperature of 35 ° C., chloroform was flown at a flow rate of 1 mL / min, polystyrene was used as a standard substance, and then the measured value was converted to a polyethylene conversion value.

Example 2 A negative charge type electrophotographic dry toner of the present invention was obtained in the same manner as in Example 1 except that the modified polyethylene resin was changed to 3 parts by trade name: HW1140H manufactured by Mitsui Chemicals, Inc. It was The physical properties of the modified polyethylene resin are shown in Table 1 above.

<Example 3> A negatively chargeable electrophotographic dry toner of the present invention was obtained in the same manner as in Example 1 except that the modified polyethylene resin was changed to 3 parts by trade name: HW1160H manufactured by Mitsui Chemicals, Inc. It was The physical properties of the modified polyethylene resin are shown in Table 1 above.

Example 4 As a polyolefin resin having a cyclic structure, a low molecular weight polyolefin resin (A) having a cyclic structure (Mn: 1900, Mw: 3100, M)
w / Mn: 1.6, glass transition point: 68 ° C.) 75 parts and high molecular weight polyolefin resin (B) (M) having a cyclic structure
n: 17500, Mw: 31000, Mw / Mn: 1.
8. Glass transition point: 68 ° C.) A negatively chargeable electrophotographic dry toner of the present invention was obtained in the same manner as in Example 1 except that 25 parts were used. The Mn and Mw of the above-mentioned polyolefin resin having a cyclic structure are values measured by GPC under the same conditions as in Example 1.

<Comparative Example 1> A negatively chargeable electron for comparison was prepared in the same manner as in Example 1 except that the modified polyethylene resin was replaced with 3 parts of polypropylene resin (trade name: NP-105, manufactured by Mitsui Chemicals, Inc.). A photographic dry toner was obtained.

<Comparative Example 2> A low density polyethylene resin obtained by modifying a modified polyethylene resin (trade name: NL2)
No. 00, manufactured by Mitsui Chemicals, Inc.) In the same manner as in Example 1 except that 3 parts were used to obtain a dry electrophotographic toner for comparison having a negative charging property.

Comparative Example 3 The procedure of Example 1 was repeated except that the polyolefin resin having a cyclic structure was replaced with 100 parts of styrene-acrylic acid ester copolymer resin (trade name: CPR-100, manufactured by Mitsui Chemicals, Inc.). As a result, a dry electrophotographic toner having a negative chargeability for comparison was obtained.

Next, the above Examples 1 to 4 and Comparative Examples 1 to
5 parts of the dry toner for electrophotography obtained in 3 and 95 parts of a silicone ferrite carrier (volume average particle diameter 90 μm) are mixed to produce a two-component developer, and the following items are tested for these developers. went.

1. Fixing strength: A black solid image of 2 cm in length and 2 cm in width is transferred onto a recording sheet , and a heat roller having a surface layer made of Teflon and a fixing device having a pressure roller having a surface layer made of silicone rubber are used to roll pressure: 30 kg. / Cm ² , roll speed: 170 mm / sec, roll surface temperature: 170 ° C., the toner image was fixed on the recording sheet, and the image density of the fixed toner image was measured by a reflection densitometer (trade name: RD-9
14, manufactured by Macbeth Co.). Then, this toner image is rubbed 5 times with a cotton pad (trade name: PPC pad, manufactured by Dynic Co., Ltd.) under a load of 500 g, and the image density of the toner image after rubbing is measured. The fixing strength was calculated by. Fixing strength (%) = (image density after rubbing / image density before rubbing) × 100 The fixing strength is required to be 85% for practical use.

2. Non-offset temperature range The roll surface temperature of the fixing device was changed stepwise to fix the toner image transferred onto the recording sheet at each surface temperature. At this time, it was observed whether or not the toner was contaminated in the blank space, and the temperature region in which the contamination was not generated was defined as the non-offset temperature width.

3. Image Density and Fog Applying each developer to a commercially available copying machine (trade name: ED-3850, manufactured by Toshiba Corp.), continuous copying is performed up to 100,000 sheets. The fog of the part was measured. Image density is a solid image with reflection densitometer (Product name: R
D-914, manufactured by Macbeth Co.), and the fog is measured by a colorimetric color difference meter (trade name: ZE2000, manufactured by Nippon Denshoku Industries Co., Ltd.)
It was measured by. The image density should be 1.35 or more for practical use, and the fog should be 1.00 or less for practical use. The above evaluation results are shown in Table 2.

[0034]

[Table 2]

As is clear from the results shown in Table 2, in the toners of Examples 1 to 4 satisfying the conditions of the present invention,
It was confirmed that the fixing strength, the image density, and the fog were practically no problem, and the non-offset temperature range was wide. Further, it was confirmed that low-temperature fixing was possible because the lower limit temperature of the non-offset temperature width fell to around 130 ° C.
On the other hand, in the toners of Comparative Examples 1 to 3, there is practically no problem in image density, but Comparative Examples 1 and 3
The fixing strength and the non-offset temperature width were not sufficient, and Comparative Example 2 had a narrow non-offset temperature width and had a practical problem.

[0036]

As described above, according to the dry toner for electrophotography of the present invention, a polyolefin resin having a cyclic structure as a component of the toner and a polyethylene resin are used.
By containing at least the modified polyethylene resin grafted with styrene, the fixing strength can be improved despite the decrease in the fixing temperature, the non-offset temperature range is wide, and there is no deterioration in image quality due to deterioration of fog, Moreover, there is an epoch-making effect that a sufficient image density is achieved at the same time.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Klaus Berger 65830 Cliftel Königsberger Strasse 19 (72) Inventor Toru Nakamura 3-chome 13-201 Tsukino, Abiko-shi, Chiba References JP 2000- 284528 (JP, A) JP 2000-66438 (JP, A) JP 60-93456 (JP, A) JP 58-63847 (JP, A) JP 9-152737 (JP, A) Kaihei 9-101631 (JP, A) JP 6-271628 (JP, A) JP 5-339327 (JP, A) JP 5-9223 (JP, A) International Publication 98/029783 (WO , A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 9/08

Claims (2)

(57) [Claims] 1. A dry toner for electrophotography, which comprises at least a polyolefin resin having a cyclic structure and a modified polyethylene resin obtained by grafting polyethylene onto polystyrene . 2. The polyolefin resin having a cyclic structure comprises a low molecular weight polyolefin resin (A) having a cyclic structure having a number average molecular weight of less than 7500 and a weight average molecular weight of less than 15,000 as measured by GPC, and a number average molecular weight of the polyolefin resin. The dry toner for electrophotography according to claim 1, which is a mixture with a high molecular weight polyolefin resin (B) having a cyclic structure having a weight average molecular weight of 7500 or more and a weight average molecular weight of 15000 or more.