JPS6010617B2 - Toner for electrophotographic development - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner for electrophotographic development, more specifically, a toner for dry development that has a thin layer thickness, high solid area reflection density, and excellent resolution. This invention relates to a toner that is compatible with a heat roll fixing method.

Image formation by electrophotography is effectively used in dry copying, offset master production, etc., and its range of applications is gradually expanding, and a large number of developing toners for such image formation have already been proposed.

Incidentally, the resolving power of conventionally known powder toners for development is generally low, usually 5 to 6 lines/side, and excellent at about 8 to 10 lines/side.

Moreover, in the case of a product with relatively excellent key image power, the toner layer thickness must be made thinner in order to improve the image power.
The reflection density in the evening part of mackerel fish decreases. In other words, it has been extremely difficult to satisfy both the demands for improved resolution and increased solid area reflection density. Further, in the above image formation, a method of directly fusing a toner image obtained after development,
Alternatively, fixing is performed by a method of fusing after transfer.

To fix the toner image, for example, a non-contact heating method using an electric furnace or a pressure heating method using a heating roll (ie, a heating roll fixing method) is adopted. The above heat roll fixing method has good thermal efficiency and quick fixing.
It is attracting attention as an effective fixing method, and is especially suitable for high-speed copying. However, this method causes so-called offset development, in which toner adheres to the heating roll and stains the next copy sheet. In the past, various attempts have been made to prevent such development, but usually a template agent such as a wax or a wax-like substance (such as a low molecular weight polyolefin) is added to the toner, and the molten toner also has mold releasability. methods are commonly used. However, when these template agents are used, the powder fluidity of the toner is significantly deteriorated, which not only adversely affects developing performance but also causes problems such as smooth toner replenishment.

Therefore, in order to improve the powder flowability, commercially available toners for hot roll fixing systems have a particle size distribution of, for example, a particle weight range of 10 to 30 mm, and an average particle size of 15 to 17 mm. It is designed to be rougher than regular toner. However, even with this improved toner, its fluidity is only at an angle of repose of 47 to 500, which is still insufficient compared to that of normal toner (40 to 43 degrees). A decrease in the particle size distribution causes a decrease in resolution (usually reduced to about 4 to 5 lines/side) and a reduction in solid area reflection density (usually reduced to 1.0 to 1.2 wall density). Furthermore, in addition to the above-mentioned problems derived from the toner itself for the hot roll fixing method, in the hot roll fixing method, the toner image is fixed by the pressure of the roll, which inevitably reduces the scale image power (in particular, the toner image is fixed by the pressure of the roll). The problems of the method itself cannot be ignored, such as the tendency to become more pronounced when the layer thickness is thick.The purpose of the present invention is to provide a method that combines excellent scale image power and high solid area reflection density, and that is optimal for high-speed copying. The object of the present invention is to provide a toner for electrophotographic development which solves all of the above-mentioned problems even when used in a hot roll fixing system.

** As a result of intensive research to achieve this objective, the present inventors have determined that the type of each component (especially as a colorant) in a toner consisting of a toner resin, a release agent, a colorant, and a charge control agent. It has been found that the desired objective can be achieved by specifying the type of carbon black (carbon black) and its blending ratio, as well as setting the particle size distribution of the toner within a certain range. This knowledge will be explained in detail below. In general, (1) To increase the scale image power, the particle size distribution is made finer and the toner layer thickness is made thinner, and (2) Toner One possible method is to reduce the layer thickness.

However, although attempts have been made to employ the method related to the conventional toner for hot roll fixing, deterioration in fluidity and reduction in solid area reflection density are inevitable. In contrast, in the present invention, ``by specifying the toner's constituent components and narrowing its particle size distribution to a certain range, appropriate toner fluidity can be obtained.
Since the layer thickness of the toner image formed on the photoreceptor and then transferred onto the transfer paper can be made thinner,
The disadvantage of reduced resolution caused by conventional toners and methods itself can be overcome, and at the same time, the reduction in solid area reflection density expected from thinning the layer thickness can also be overcome, and proper high-speed copying is possible. Regarding these points, an example of comparative data when the toner of the present invention and a conventional product (commercially available product) are used in a hot roll fixing method is shown below.

The present invention was completed based on the above-mentioned knowledge, and its gist is 'a - weight average molecular weight (hereinafter abbreviated as "Mw") 3
000 or more styrene resin 100 parts (by weight, the same applies hereinafter), 'b} 5 to 15 parts of furnace type carbon black with a pH of 6.5 to 9.5, 'c} 3 to 1 part of a low molecular weight polyolefin of not more than Mwlooooo , and {d} 0.5 to 5 parts of a charge control agent, and an electrophotographic developing toner characterized in that it has a grain size range of 5 to 20 μm and an average particle size of 9 to 10 grains. exists in

In the toner of the present invention, among the styrene resins used as toner resins, especially M
Polystyrene resin, styrene or its derivatives (p
-chlorostyrene, pinyltoluene, etc.) and other vinyl monomers (ethylene, vinyl chloride, butadiene, methyl acrylate, butyl methacrylate, acrylonitrile,
Examples include copolymer resins with acrylamide, vinyl methyl ether, vinyl methyl ketone, N-vinyl pyrrole, etc., and one or a mixture of two or more of these may be used.

Commercially available products of such styrene resins include, for example, Sanyo Kasei Co., Ltd.'s product names "Himaichi SBM600, SBM73";
Goodyear product name "Priolite S-9B, V"
Examples include TL, VTACL, ACL, HM Yamaichi, and Esso Chemical Co., Ltd.'s product name "Picolastic D-150, D-125."Incidentally, among the above styrene-based resins, those with Mw 300*1 are used. Even when used, the softening point is too low, so when used as a powder, storage stability is poor and so-called blocking development occurs at room temperature.

In the toner of the present invention, the carbon black as the component b has a bait of 6.5 to 9. Preferably pH 7-8.5
Use a neutral to weakly basic furnace type.

This carbon black usually has a particle size of 10 to 25 mr, preferably 15 to 20 mr. In particular, the Tinting Strength Index (TintingStrenQhIndex), which indicates the coloring strength of carbon black,
) is 100 or more, preferably 115 or more.

Commercially available carbon blacks include, for example, "Monarch 700, 800" manufactured by Cabot Corporation.
88o, 900", "Black Pearls 70
0,800,880,900ha Columbian Carbon manufactured by Nippon Co., Ltd. under the trade name "RAVENI 170, 1250, etc.", and one or a mixture of two or more of these may be used.The amount used is 10 dollars of the above component a. It is selected in the range of 5 to 15 parts, preferably 5 to 1 part per part.
If it is less than 5 parts, the reflection density of the toner particles themselves will be low, and if it exceeds 15 parts, the layer thickness of the toner image will be insufficient and the reflection density will be reduced.

The acidity (basicity) of the carbon black has a large effect on the density of toner images, and the pH is 6.
When the toner image size is 4.5 mm rather than 5.0 mm, minute voids are more likely to occur in the toner image layer, and the toner layer thickness also becomes thicker.

On the other hand, if the pH is greater than 9.5, the layer thickness of the toner image becomes too thin, making it impossible to provide a sufficient solid area reflection density. As a result of research conducted by the present inventors, a toner made by combining the carbon black with a modified epoxy resin has been devised, and an application for this has already been filed.

However, when comparing the toner of this application and the toner of the present invention, the technical effects of the two toners are clearly different. This is because the former toner is intended for transfer to a photosensitive resin plate and does not include the technical content of fixing a toner image, whereas the toner of the present invention is compatible with a fixing method using a hot roll. The constituent components are limited, and the defined range of particle size distribution is different. In the toner of the present invention, the C component, the low molecular weight polyolefin, is added to the toner for hot roll fixing, so the polyolefin has a molecular weight of less than Mwlooooo, preferably 20,000 to 800.
0 low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight polypropylene.

Commercially available products of such low molecular weight polyolefins include, for example, "AC Polyethylene Kushi 617" manufactured by Allied Chemical Co., Ltd., and "Viscol 55 Ho" manufactured by Sanyo Chemical Co., Ltd.
etc., and one or a mixture of two or more of these may be used. The amount used is selected in the range of 3 to 1 part, preferably 3 to 5 parts per 10 parts of component a, from the viewpoint of imparting mold release properties and improving fluidity. Note that even if one of the above-mentioned low molecular weight polyolefins having a molecular weight exceeding Mwloooo is used, offset development cannot be prevented because the softening point is high.

As the charge control agent for the component d in the toner of the present invention, commonly used nigrosine dyes, metal-containing dyes, and the like can be used.

Commercially available products of such charge control agents include, for example, "Bontron N-01, N-02, N-" manufactured by Orient Chemical Co., Ltd.
03, S-31 etc., and one or two of these
A mixture of more than one species is ready for use. The amount used is 0.5 to 5 parts, preferably 0.5 to 5 parts, based on the 10 parts of component a above.
Select within the scope of 2 parts. If it is less than 0.5 parts, the charge amount will be too low and dust will be generated when it is used as a developer, causing fog on the copy, and if it exceeds 5 parts, the charge amount will be too high and solid areas will be produced. reflection density decreases.

The toner of the present invention is produced by treating each of the above-mentioned components a to d in predetermined proportions according to a conventional method.

For example, after premixing components a to d, they are melt-kneaded using a hot roll, extruder, etc., then coarsely ground using a hammer mill, etc., finely ground using a jet mill, etc., and finally classified using a zigzag classifier, etc. Bye. It is important that the toner of the present invention thus obtained has a particle weight range of 5 to 20 particles and an average particle size of 9 to 10 particles. If the particle size is less than 5 within this range, the durability of the toner itself will be reduced, background smudges will increase, and powder fluidity will deteriorate, resulting in a decrease in developing performance and furthermore, toner replenishment will be difficult. It becomes difficult to do it smoothly. On the other hand, if it is larger than 20 degrees, the density of toner development becomes small, creating voids in the layer and increasing the layer thickness.

When the layer thickness becomes thick in this manner, heat conduction does not occur smoothly during high-speed copying, and offset (cold offset) development occurs due to so-called fixing failure. This development involves increasing the amount of release agent (for example, 15
~20% by weight), it will no longer occur, but if this happens, the powder fluidity will deteriorate, and as mentioned above, this will have an adverse effect on developing performance and toner replenishment. is the angle of repose approximately 43o ~ 45
Shows appropriate fluidity such as o.

The toner of the present invention can be mixed with a carrier such as iron powder according to a conventional method and used as a developer for a known copying machine.

For example, when mixed with iron powder and used for development using a magnetic brush development method, 8 to 15 images (conventional product: 20 to 30
If one layer of thin toner (1) is used and heat roll fixing is performed after transfer, the scale image power on the transfer paper will be 10-12.5 lines/rail (conventional product; 5-6 lines/side), solid area reflection density 1 .4-1.5
(Conventional product: 1.0 to 1.2) A high image is formed.
The toner of the present invention having the above structure satisfactorily combines the excellent resolution and high solid area reflection density required for an electrophotographic toner with a thin toner layer thickness, and its usefulness is particularly It can be said that this technology can be used to a greater extent if a heat roll fixing method, which is most suitable for high-speed copying, is adopted. Next, the present invention will be specifically explained with reference to Examples and Comparative Examples. Example 1 Styrene-acrylic copolymer resin (manufactured by Sanyo Kasei Co., Ltd., trade name "Himer SBM600", Mw: 60000) 10 anchor parts, low molecular weight polypropylene (Sanyo Kasei Co., Ltd. trade name "Piskor 55 Cape Ha Mw: 4000)" 5 Carbon black (Columbiyan 4 Carbon manufactured by Nihon Sha Co., Ltd. Product name: RAV
EN1250", pH 7.0) and 8 parts of a charge control agent (
Orient Chemical Co., Ltd. (product name: “Bontron S-31”) 2
After premixing the parts with a mixer, they are melt-kneaded using hot rolls, and then coarsely pulverized, finely pulverized, and classified to give 5-20%
A toner having an average particle size of 9 to 10 mm was prepared.

The angle of repose of this toner (measured with a product name "Powder Tester" manufactured by Hosokawa Iron Works Co., Ltd., hereinafter the same) was 43o. Add 5 parts of the above toner to iron powder (product name: EFV20 manufactured by Nippon Iron Powder Co., Ltd.).
0/300'') to obtain a developer, and a toner image was formed on a commercially available selenium drum by magnetic brush development.

The toner layer thickness was approximately 14 mm. When this was electrostatically transferred to paper and fixed on a 185-200 qo Teflon-coated heat roll at a speed of 12 units/sec, no offset development occurred, the resolution was 1 stop/side, and the solid area reflection density ( A clear copy of 1.50 was obtained using a Macbeth reflection densitometer. Also, change the conveyance speed to 1.
Even when the speed was increased from 2 rams/sec to 20 rams/sec, the fixation was good. Comparative example 1 “No-Imer SBM600
” 100 copies, “Biscole 55 Sails” 1 anchorage, “RAVE
8 parts of "N1250" and 2 parts of "Bontron S-31" were treated in the same manner as in Example 1 to prepare a toner.

When the particles were crushed and classified to an average particle size of 9 to 10 degrees with a particle size range of 5 to 20 degrees, the angle of repose was 53 degrees, and the fluidity was poor and toner replenishment could not be carried out smoothly. Therefore, grain law range 10
~Crushed with an average particle size of 15 to 16 pieces using 25 pieces. When it was classified, the angle of repose was 47o. Five parts of such toner are
A developer was obtained by mixing 95 parts of "FV200/300", and the same test as in Example 1 was conducted. As a result, the toner layer thickness was about 25 pm, and no offset development occurred during fixing, but the particle size was Due to the roughness, the resolution is 5 lines/yanagi, and the solid area reflection density is 1.

I was only able to get a copy of 0.

In addition, the conveyance speed has been increased from 12 m/sec to 20 m/sec.
When the speed was increased to sec, fixing failure occurred and offset development (so-called cold 8 offset) occurred. Comparative example 2 100 copies of “/・immer SBM600”, “Viscoll 5”
5 parts of "Columbian 8 Carbon" manufactured by Nippon Co., Ltd., product name "RAVEN1255", pH 3.0
) and 2 parts of "Bontron S-31" were treated in the same manner as in Example 1 to obtain "grain size range of 5 to 20 degrees, average grain size of 9 to 10 degrees."
A toner of this type was prepared.

The angle of repose of this toner was 450. A developer was obtained by mixing 5 parts of the above toner with 95 parts of "EFV200/300", and a test was conducted on the same machine as in Example 1. As a result, the toner layer was as thick as about 30A, resulting in poor fixing. Offset development occurred.

The scale image power was 5 lines/skin, and the solid area reflection density was 1.2.
Further, when the conveyance speed was increased to 200 ribs/sec, offset development became severe.
*Examples 2 to 7 A toner having the composition and angle of repose shown in Table 1 was prepared by processing in the same manner as in Example 1, and then a developer was prepared, and then the same test as in Example 1 was conducted. The toner image layer thickness and performance data are shown in Table 1.

(Table 1 left ■) "Picolastic D-150": Polystyrene Shioji (M: approx. 5000) manufactured by Esso Kagaku Tsurugasa.

"Picolastic D-125": Polystyrene resin (MW: approx. 3000) manufactured by Esso Chemical Strings. "AC Polyethylene 6A": Low molecular weight polyethylene manufactured by Araido Chemical Company. "AC Polyethylene 617": Alite Chemical Nene Myotan Europe Polyethylene o "Monarch 8
80": carbon black manufactured by Capot Loquat (pH 8.
0). Examples 8 and 9 The same machine as Example 1 was processed, and the second
After preparing a toner with the composition and angle of repose shown in the table, and then preparing a developer, a test similar to that of Example 1 was conducted, except that a commercially available trizinc oxide photoreceptor was used in place of the selenium drum. The layer thickness and performance data of the toner images are shown in Table 2.

2nd page ■) "Priolite VTL": Pinyltluene-butadiene copolymer resin (Mw: 7800
0).

"Bontron N-02": Orient Chemistry 2 Earthen Charged Rare Chest"

Claims (1)

[Scope of Claims] 1 (a) 100 parts by weight of a styrene resin having a weight average molecular weight of 3000 or more, (b) 5 to 15 parts by weight of furnace type carbon black having a pH of 6.5 to 9.5, (c) Weight average molecular weight 3 to 10 parts by weight of a low molecular weight polyolefin of 10,000 or less, and (d) 0.5 to 5 parts by weight of a charge control agent.
A toner for electrophotographic development, characterized in that it consists of parts by weight, has a particle size range of 5 to 20 microns, and has an average particle size of 9 to 10 microns. 2. The toner described in item 1 above for use in a hot roll fixing method. 3. The toner according to item 1 or 2 above, wherein the low molecular weight polyolefin is low molecular weight polyethylene and/or low molecular weight polypropylene. 4. The toner according to any one of items 1 to 3 above, wherein the charge control agent is a nigrosine dye and/or a metal-containing dye.