JPS62982A - Method for fixing color toner image - Google Patents

Abstract

PURPOSE:To improve the reproducibility of an image by forming a color image with each color toner contg. a prescribed binding resin and having a prescribed softening point and by fixing the image with fixing rollers made of rubber having a prescribed average mol.wt. so as to prevent the stain of the surfaces of the rollers. CONSTITUTION:In a color electrophotographic copying machine, a transfer material is released from a gripper 24 after transfer, guided to a conveying belt 27 with a separating claw 26 and led to a fixing roller 28 and a lower pressure roller 29 as rotating bodies for fixing to fix a color image by heating under pressure. The color image is formed with each color toner contg. a binding resin and having about 60-150 deg.C softening point. The binding resin consists of 70-95wt% sharp-melt polyester resin and 5-30wt% styrene-acrylic copolymer. The rollers 28, 29 are made of methylvinylsilicone rubber having 20,000-200,000 average mol.wt. and vulcanized at a low temp. The stain of the surfaces of the rollers 28, 29 is prevented to improve the reproducibility of an image.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for fixing a color toner image, and more specifically, the present invention relates to a method for fixing a color toner image, and in particular, fixing each color toner containing a specific binder resin with a fixing roller having a specific rubber material improves offset resistance. , a color toner image fixing method KI31 that aims to prevent discoloration of the rubber of the fixing roller and improve durability.

BACKGROUND OF THE INVENTION Conventionally, in the field of electrophotography, color electrophotographs have been produced using, for example, a color electrophotographic reproduction apparatus as schematically shown in FIG. 1 of the accompanying drawings. That is,
An electrophotographic photosensitive drum 1 having an insulating layer on its surface is rotatably supported by a shaft 2, and starts rotating in the direction of an arrow 3 in response to a copy command. When the drum 1 rotates at a constant speed, the original 0 placed on the original platen glass 4 is illuminated by an illumination lamp 6 integrated with the first scanning mirror 5, and the reflected light is transmitted to the second scanning mirror. □ At 7, it is scanned. Since the first scanning mirror 5 and the second scanning mirror 9-7 move at a speed ratio of 1:1, the scanning of the original is performed while the optical path length between the original 0 and the lens 8 is always kept constant. The reflected light image passes through a lens 8 and a third mirror 9, is color-separated by a color separation filter 10, and further passes through a fourth mirror 11 and a dustproof sealing glass 12, and is imaged on the drum 1 by an exposure section 13.

The drum 1 is neutralized by a static eliminator 14, and then charged by a negative charger 15.
After being charged (for example, positive) by
The image illuminated by the illumination lamp 6 is subjected to slit exposure. At the same time, static electricity of the opposite polarity (for example, negative) to the drum C or - is removed by a static eliminator 16, and then a high-contrast electrostatic latent image is formed on the drum 1 by full-surface exposure using a full-face exposure lamp 17.

The electrostatic latent image on the photosensitive drum 1 is then developed into a toner image by a developing device 18. Developer 18 is yellow 18
It is composed of three developing devices: 1, magenta 182, and cyan 183, and the specified developing device works according to the color separation filter used for exposure to obtain a toner image of the required color.

The recording material 201 in the cassette 191 is fed into the machine by the paper feed roller 211, and the rough timing is determined by the first register roller 221, and then the accurate timing is determined by the second register roller 26. The tip of the transfer drum 53 is gripped by the gripper 24 of the transfer drum 53. As the transfer drum 53 rotates, the transfer material 20 is conveyed while being wrapped around the drum 33 and passed between the transfer charger 25 and the photosensitive drum 10.
A toner image of the photosensitive drum 1 is transferred onto the transfer material while the photosensitive drum 1 passes through the transfer material. The transfer drum 35 rotates at a required number of rotations while gripping the leading end of the transfer material with the gripper 24, and images of the required number of colors are transferred.

The copying machine shown in FIG. 1 is equipped with two cassettes loaded with transfer materials of different sizes and types so that the sheets can be fed selectively.

After the transfer is completed, the transfer material is released from the gripper 24, guided to the conveyor belt 27 by the separating claws 26, further guided to the fixing row 228 as a rotating body for fixing, and the lower pressure eye 229, where it is fixed by pressure and heat. , and then discharged onto the tray 30. Further, after the transfer, the surface of the photosensitive drum 1 is cleaned by a cleaning device 31 composed of an elastic blade, and the process proceeds to the next cycle.

As mentioned above, in the case of a color electrophotographic copying device, toners of multiple colors are loaded on the transfer material, and the toners are all heated and melted, and the colors are mixed to obtain a dark image.This color image is In order to obtain color reproducibility close to the original (original) K, a sharp melt toner with a low softening point is used for the toner, and care has been taken to ensure that the toner is sufficiently heated and melted in the fixing device and the colors are mixed.

In color electrophotography, multiple layers of toner are heated and melted to mix colors in order to reproduce colors close to those of the original document, so it is necessary to use toner with a low softening point. When using a toner with a low softening point, the toner will soften when fixed with a heating roller using a fixing roller equipped with a fluorine-based resin layer such as Teflon, which is used in ordinary black-and-white copiers. The offset phenomenon caused by adhesion to the rear side occurs significantly, making it extremely difficult to obtain a good fixed image.

Room temperature vulcanizable silicone rubber (hereinafter referred to as R
It has been proposed to use a fuser roller comprising a layer of TV silicone rubber (abbreviated as TV silicone rubber). However, RT
Although V silicone rubber has excellent mold releasability at the initial stage of use, it is inferior in durability, so if used many times or over a long period of time, the elastic properties of RTV silicone rubber will deteriorate and it will be easily contaminated by toner. , as a result, the lifespan is short.
Therefore, the frequency of replacing the fixing roller increases, making maintenance of the color electrophotographic copying machine difficult and leading to an increase in cost. ＆Maru, each color toner used in color electrophotographic copying machines is required to have extremely strict chromaticity, brightness, etc., as the tone reproducibility of color images is strictly tested. In order to do this, not only pigments but also dyes and/or sublimable dyes are added as coloring agents. Since these dyes and sublimable dyes have strong adhesion, they adhere to and contaminate the surface of the four-layer during fixing, and also promote deterioration of the KRTV silicone rubber.

An object of the present invention is to provide a color toner image fixing method that solves the above-mentioned problems.

That is, an object of the present invention is to improve the durability of the fixing rubber roller;
It is an object of the present invention to provide a method for fixing a color toner image using a hot roller 9, which has excellent offset resistance and has a long life with little dye staining on the roller surface.

Specifically, the present invention provides a method for fixing a toner image using a binder resin consisting of at least 70 to 95% by weight of a sharp-melt polyester resin and 5 to 30% by weight of a styrene-acrylic copolymer. The force 2-image formed from toner of each color and having a softening point of about 60'C to about 150'C is used as a rubber material with an average molecular weight of 2
A force 9 characterized by a fixing roller 2 having a low temperature vulcanization type methyl vinyl silicone rubber of 10,000 to 200,000 yen.
−)? - An image fixing method.

The present invention will be explained in more detail below.

The sharp-melt polyester resin used in the present invention is a polymer compound having an ester bond in the main chain of the molecule, which is synthesized from a diol compound and a dicarboxylic acid.

Examples of diol components include ethylene glycol, 1
．． 2-Full 1: 'Lenglyfur, 1.320 pyrene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butanediol, 1,4-bis(hydroxymethyl)cyclohexynane, bisphenol A,
Examples include bisphenol type diols such as hydrogenated bisphenol A, polyoxyethylenated bisphenol, and polyoxypropylenated bisphenol.

Examples of the dicarboxylic acid component include aliphatic dicarboxylic acids or aromatic dicarboxylic acids such as maleic acid, fumaric acid, isophthalic acid, terephthalic acid, cyclohexene dicarboxylic acid, succinic acid, adipic acid, heptapacic acid, malonic acid, and oxalic acid; Examples of these acid anhydrides include esters with lower alcohols.

Softening temperature of sharp melt polyester resin used in the present invention: 60 to 150°C, preferably 80 to 120'C
is good. In addition, polyester resin has a weight average molecular weight (
My) is 4 Q OO, ~20 to 000 preferably 40
00 to toa, ooo, and the number average molecular t (Mn) is 2500 to 7000. Preferably 5oon to 5ooo
(However, MY≧Mn) is preferable. moreover,
The MV/Mn of the polyester resin is preferably 7 or less (more preferably 6 or less). That is, if the average molecular weight is below the specified range, the molecular weight is too low and booking or offset occurs, and if the average molecular weight is above the specified range, the fixing temperature becomes too high to be of practical use.

Moreover, if the MW/Mn of the polyester resin is 7 or more, sharp melting will not be exhibited and color mixing will be insufficient.

The softening point in the present invention refers to a value obtained by measuring a temperature To measured by the following method. Note that changes may be made with reference to the measurement method according to the present invention. That is, using a 70-chistar OF
Applying an extrusion load of oIc9 and setting the initial temperature to 80°C, after preheating I#11300 seconds, the temperature is raised at a constant rate of 5°C/min, and the plunger drop amount of toner drawn at death - temperature curve (
Hereinafter, the softening S-shaped curve 5) will be determined. The sample toner used was a fine powder of 1-3I, and the cross-sectional area of the plunger was 1.0 cm2. The softening A-shaped curve is usually the curve shown in FIG. Constant velocity □Temperature rises (as a result, the toner is gradually heated and begins to flow out. , (Plunger descent → B) When the temperature is further increased, the molten toner largely flows out. B −+ O → D) The plunger descent stops and ends. (D→E) The height H of the B-shaped curve indicates the total outflow amount, and the temperature To corresponding to the 0 point of ψ indicates the softening point of the toner.

The sheep-melt resin in the present invention has a melt viscosity of I
Q' The temperature when cp is shown is τ1.5) The temperature when 104cp is shown is T2, and the time of death T1=H]O~? 50℃1ΔTl==ITl−T21
==5~5 Refers to a resin that satisfies the conditions of Q'C.

In addition, melt viscosity measurement is performed using a constant temperature bath that can control the temperature of the sample and rotor (for example, product name Vi#aon-H engineering, model To
The test can be carried out using a B-type rotational viscometer for high viscosity (e.g., BaH type (manufactured by Tokyo Keiki)) equipped with a rotor of FU4 or FU5.

Sharp-melt resins having these temperature-melt viscosity characteristics are characterized in that their viscosity decreases more sharply when heated.

Such a decrease in viscosity causes appropriate mixing of the fifth toner layer and the bottom toner layer, and furthermore, rapidly increases the transparency of the toner layer itself, resulting in good subtractive color mixing.

Toners using resins with a T1 of 100°C or lower, for example, easily block and have shortcomings in storage stability.Furthermore, if T1 is 150°C or higher, color mixing properties are poor and fixing properties are poor. Difficulties also arise.

Acrylic monomers for styrene-acrylic copolymers include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, and ethyl methacrylate. , butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylic nitrile, acrylamide, etc.

The copolymer resin used in the present invention 8AK is obtained by copolymerizing the above-mentioned seven polymers by a general method such as solution polymerization or bulk polymerization, and at the same time subjecting it to a certain degree of crosslinking treatment using a crosslinking agent such as divinylbenzene. Weight average molecular weight is approximately 25
QOOO~40 (about LO00).

Furthermore, as an optional component, materials conventionally used as binders for toners can be appropriately mixed as long as they do not impede the effects of the present invention. For example, polyvinyl chloride, natural resin-modified phenol, natural resin-modified! Leic acid resin, polyvinyl acetate, silicone resin, polyurethane, polyester resin, polyamide resin, ionomer resin, 7
, 7 resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumarin indene resin, petroleum resin, chlorinated paraffin, etc. can be used as appropriate.

These resins may be mixed together to the extent that the properties of the copolymer of the present invention are not impaired.

The ratio of the polyester resin to the styrene-acrylic copolymer is such that 5-30% by weight of the styrene-acrylic copolymer is added to 70-95% by weight of the polyester resin. When the amount of the styrene-acrylic copolymer added exceeds 30% by weight, the toner tends to lose its sharp melting properties, making it impossible to achieve sufficient color mixing during fixing. Further, if the amount is 5% by weight or less, the staining of dyes and pigments contained in the toner on the fixing roller increases.

The fixing roller used for fixing in the present invention has a rubber material layer, and the rubber material layer is an addition reaction low temperature vulcanization type methyl vinyl silicone rubber (hereinafter referred to as L'ff silicone rubber (abbreviated as). The LTV silicone rubber used in the present invention has an average molecular weight of 2
It is good to have a weight of 50,000 to 200,000, preferably 50,000 to 150,000. When the average molecular weight of IITV silicone rubber is less than 20,000, there is a marked tendency for offset resistance to decrease, making it extremely difficult to put it into practical use. In case, rubber p-2
cannot obtain the strength necessary for fixing, and is extremely difficult to use as a fixing device. The fixing device 2 equipped with the LTV silicone rubber used in the present invention is less likely to be dyed and contaminated by toner than the conventionally used RTV silicone rubber, has excellent offset resistance, and has a durable (number of sheets of paper) can be improved.

The I,'ff silicone rubber used in the present invention is an addition reactor, and those containing a vinyl group as an unsaturated group and represented by the following formula are mainly used.

uHs Lj 5 -H1 (In the formula, m indicates the degree of polymerization.) On the other hand, the conventionally used RTV silicone rubber is a condensation reactor, and the terminal hydroxyl group is blocked and the rubber shown in the following formula is Being used.

(In the formula, n indicates the degree of polymerization.) These RT'V silicone rubbers are polyester resins (having -coon groups, -OH groups) used as binder resins having OH groups at the terminals. shows potential affinity with. L' for polyester resin against slippage
The affinity of l'V silicone rubber is for RTV with OH groups.
Since it has a weaker affinity than silicone rubber, it has excellent anti-offset properties. In addition, organic colorants contained in color toners often have polar groups, and the core layer colorant is RT having an OH group rather than L'ff silicone rubber.
``l has a high tendency to adhere to silicone rubber, and its rounded radius
? '7 Silicone rubber fixers tend to deteriorate faster due to adhesion of colorants than silicone rubber fixers.

Atasho, which easily applies LTV silicone rubber, if necessary, conventionally used heat resistance improvers, antioxidants, fillers for toning, surface treatment agents for fillers, Even if various fillers such as silica fillers are added, they will not fade. For example, it is preferable to add petals and the like. Conventionally known techniques can be used to manufacture the fixing roller using L'ff silicone rubber or L'ff silicone rubber composition.

Furthermore, in the fixing process used in the present invention, a release improver such as dimethyl silicone oil may be applied to the pressure roller and heating roller by a conventionally known method. The toner used in the present invention is manufactured from toner constituent materials by a conventionally known method. For example, polyester resin,
Styrene-acrylic resin, colorant, charge control agent, etc. are melt mixed, pulverized, and classified to produce toner. If necessary, an external addition step of adding various external additives to the toner may be added.

- It is used as a two-component additive when mixed with -. Carriers include cobalt, iron, ferrite, copper, nickel,
For gold 5-t-+, alloys of zinc, aluminum, brass, etc. are used. The carrier may be coated with silicone resin, styrene-acrylic resin, or the like.

Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited only to the Examples.

Example t Propylene glycol 5.25 parts (4 L quantity) Tofumaric acid 5. oo part (mole amount) was reacted at 170 to 200'C for 4 hours to give a softening point of 113℃Mv22000℃Mn4000
polyester resin (TI=1!13℃, T2 electric 15B
'e, 1ΔT +=25°C) was obtained. 95 parts by weight of the obtained polyester resin, 5 parts by weight of styrene-butyl methacrylic copolymer (Himer 8BM 7S manufactured by Sanyo Chemical Co., Ltd.) and the following colorant (mixed in 3 parts by weight per 100 parts by weight of binder resin) were added. They were mixed, melt-kneaded, cooled, crushed, and classified to obtain toners of each color with an average particle size of 9 μm. The softening point of the toner was 116°C.

Colorant 4: t, m -; 7zo yellow dye (trade name Kay
aset Yssllov Magenta: Rhodamine-based magenta dye (Rhodamine Base FB manufactured by BAaF) Cyan: Phthalocyanine-based blue pigment (Onol Blue 10. manufactured by Toyo Ink) 610 parts by weight of each color toner obtained was mixed with carrier iron powder with an average particle size of 5゜μ. 90 parts by weight of each were mixed to prepare active agents for each color. The prepared formulations for each color have an average molecular weight of 10.
Use A4 size paper that has been placed in the copying machine shown in Figure 1, which incorporates a fixing roller with a surface layer of LTV dimethyl silicone rubber, and has been subjected to a copying test at a temperature of 140 to 150'C on the surface of the fixing roller. In a full-color continuous sheet feeding test, no discoloration or offset occurred on the surface of the fixing roller, and there was no practical problem even if up to 4,000 sheets were fed.90 Comparative Example 1 Polyester used in Example 1 Yellow and magenta cyan color developers were prepared in the same manner as in Example 1 except that only the resin was used.

Note that the softening point of the toner was 114°C.

The developer of each color prepared was put into the copying machine shown in Figure 1, which incorporated a fixing roller having a RTV silicone rubber (Shin-Etsu Chemical Exhibition Xi14OO) layer, and a full-color continuous paper feeding test was carried out using A4 size paper. It was carried out in the same manner as in Example 1. The surface of the fixing roller turned black from around the 1000th sheet passed, and an offset phenomenon started around the 5000th sheet passed. Comparative Example 2 Prepared with Example 1, which is a toner containing polyester resin and styrene-acrylic resin. R
Using the developing machine used in Comparative Example 1, which is equipped with a fixing roller having a TV silicone rubber layer, an A4 full color one continuous sheet feeding test was conducted. The roller surface began to turn black around the 3000th sheet passed, and offset development started around the 8000th sheet passed.

Example 2 Polyester resin (Atrac 382 manufactured by Kao Soap Co., Ltd.)
85 parts by weight and styrene-acrylic copolymer (Mitsubishi Sea 1
Developers for each color were prepared in the same manner as in Example 1 except that 15 parts by weight of B-85 (manufactured by Fu Co., Ltd.) were used. A full-color continuous paper-passing test was conducted using sized paper. No discoloration or offset was observed on the surface of the fixing roller.
Even after passing up to 0,000 sheets, there were practical problems.

Example 5 Developers for each color were prepared in the same manner as in Example 1, except that 70 parts by weight of the polyester resin used in Example 2 and 30 parts by weight of the 9-styrene-acrylic copolymer used in Example 2 were used. A continuous sheet feeding test was carried out in the same manner as in Example 1. No discoloration or offset phenomenon of the fixing roller was observed, and up to 40,000 sheets were fed without any practical problems.90 Example 4 Propylene glycol 5. Polyester resin (Mw
=7000, Mn=3000, T+=126℃, T2
=IS9℃, 1△T I=13℃).

85 parts by weight of the obtained nine polyester resin and styrene-butyl methacrylate copolymer (My=e30QOOO,
Developers for each color were prepared in the same manner as in Example 1 except for using 15 parts by weight (Mn = 30,000, copolymerization ratio 85:15).Next, LTV methyl vinyl silicone rubber having an average molecular weight of 20,000 was prepared. A continuous paper passing test was conducted in the same manner as in Example 1 except for incorporating a fixing roller using . Discoloration of the fixing roller and offset development were not observed up to 20,000 copies.

Example 5 Polyvarnish 7', Ill/resin (My-15000, Mn=!1000) having a softening point of 105° C. was obtained from bisphenol starch (mol) and fumaric acid 2 parts (mol).

85 parts by weight of the obtained polyester resin and styrene-2-
Ethylhexyl acrylate copolymer (Mw=2500
Developers for each color were prepared in the same manner as in Example 1, except that 15 parts by weight of 0.00, Mn=15000, copolymerization ratio 9:10) were used.

Next, a continuous sheet feeding test was conducted in the same manner as in Example 1 except that a copying machine incorporating a fixing roller using LTV methylvinyl silicone rubber having an average molecular weight of 200,000 was used.

No discoloration or offset phenomenon of the fixing roller was observed, and up to 30,000 sheets were passed, but there was no practical problem, but some damage was observed on the roller surface.◎ Comparative Example 3 Except for using only polyester resin Developers for each color were prepared in the same manner as in Example 1, and a continuous paper feeding test was conducted in the same manner as in Example 1. The toner contains a styrene-acrylic copolymer, and the fixing roller becomes colored after about 5,000 sheets of paper are passed through, and the color of the fixing roller changes after about 9,000 sheets of paper pass through.
Hirakoro's versatile friend is starting to stand out.

Comparative Example 4 Developers for each color were prepared in the same manner as in Example 1, except that 98 parts by weight of the polyester resin and 2 parts by weight of the styrene-acrylic copolymer used in Example 1 were used. 0 styrene which was subjected to continuous paper passing test.
Since the content of the acrylic copolymer was low, only the same results as in Comparative Example 3 were obtained.

Comparative Example 5 Developers for each color were prepared in the same manner as in Example 2, except that 60 parts by weight of the hazardous polyester resin and 40 parts by weight of the styrene-acrylic copolymer used in Example 2 were used. A continuous paper passing test was conducted in the same manner. Although there was no discoloration of the fixing roller, the content of the styrene-acrylic copolymer was too high, so the color mixing of each color toner was not good, and there was a large difference in tone between the original and the color toner image. Comparative example 6 A continuous paper passing test was conducted in the same manner as in Example 1, except that a fixing roller having an LTV vinyl silicone rubber layer having an average molecular weight of 250,000 was incorporated. Due to the insufficient joint strength of the rubber roller, the rubber layer begins to break after about 5,000 sheets have been passed.Comparative Example 7 Fixing roller having an L'ff methylvinyl silicone rubber layer with an average molecular weight of 10,000 A continuous sheet feeding test was conducted in the same manner as in Example 1, except that a copying machine incorporating the following was used. Around the 40th sheet of paper that has been passed, the surface of the fixing roller becomes discolored, and around the 9000th sheet of paper that has been passed, offset begins to occur.

[Brief explanation of the drawing]

Among the accompanying drawings, the first drawing shows a schematic cross-sectional view for explaining a specific example of a color electrophotographic copying device, and the second drawing shows a graph for explaining a toner softening S-shaped curve. 0 1... Drum 4... Document glass 5.7, 9.11 - Remirror 6 - Lamp 8 - Lens 10.1 Filter 14.16... Static eliminator 15... - Next Charger 17...Lamps 18t, 182, 183...Developer 191...Cassette 201...Transfer material 33...Transfer drum 24 Thorn ripper 29.31 tatami mats...Pressure roller 28...Fixing a-ra

Claims (1)

[Claims] (1) In a method for fixing a color toner image, a binder resin containing at least 70 to 95% by weight of a sharp-melt polyester resin and 5 to 30% by weight of a styrene-acrylic copolymer and having a softening point of approximately Fixing a color image formed from toner of each color at 60° C. to about 150° C. with a fixing roller comprising low-temperature vulcanizable methyl vinyl silicone rubber with an average molecular weight of 20,000 to 200,000 as a rubber material. A color toner image fixing method characterized by: