JPH09190034A - Color toner fixing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color toner fixing method whereby toner releasability is made excellent by means of a simple structure without using oil and without being costly. SOLUTION: In fixing rollers, heat rollers 17 and 18 covered with two or more types of color toners 19 and elastic layers 14, 14', respectively, are arranged vertically. The color toners each contains polyester resin as a main binder component and 1-3wt.% Fisher-Tropsch wax is blended into it. The fixing rollers are formed so that a recess is made in the elastic layer 14, with which the surface of a transfer medium with the toner attached to it comes into contact, by firmly pressing the elastic layer 14' of the other heat roller into it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color fixing method used in a fixing device such as a color electrophotographic method, a color electrostatic recording method, a color electrostatic printing method or the like which is adopted in a color copying machine, a color printer or the like. In particular, the present invention relates to a color image fixing method in which the releasing property of a fixing roller is improved by a desired color.

[0002]

2. Description of the Related Art In a fixing device for a color toner image using an electrophotographic method, a pair of upper and lower heat rollers each having a surface covered with an elastic layer and having a heater built in each roller is used. The mainstream is a heat-pressurizing roller-type fixing device in which a transfer medium is passed through the nip formed in 1 above, an excessive load is applied, and a toner image is fused and fixed by heat.
Since this method fixes color toner having a larger thickness than a monochrome toner image, it cannot sufficiently melt the toner image with a device having a heat roller only on the surface of the toner image of the transfer medium to be fixed as in the past. . Therefore, in order to obtain a highly saturated color image with the heat-pressure roller type fixing device, a large amount of heat is applied from both the front surface and the back surface of the transfer medium to sufficiently melt the toner and eliminate the toner agglomerates to form an image. It is for smoothing. However, since such toner fixes the color toner with a large amount of heat, hot offset easily occurs. To prevent this, it is necessary to apply a large amount of release agent (oil) to the fixing roller. Since a release agent coating mechanism is required, the fixing device becomes complicated and the cost increases. Further, the application of a large amount of release agent causes deterioration of the fixing roller, and the life of the fixing device can withstand only 20,000 to 30,000 sheets of paper, and the release agent is used when printing OHP sheets. Some users may find it uncomfortable because of the adherence.

Therefore, it is possible to improve the releasability of the toner itself and fix the toner without oil. There is a binder resin containing a wax in order to improve the releasability of the toner. For example, as shown in JP-A-7-114204, a polyester resin is used as a main binder component and Fischer-Tropsch wax is contained in an amount of 1 to 5% by weight. There has been proposed a toner containing such a toner, which has improved releasability and meltability, prevents high-temperature offset, and realizes cleanerless fixing.

[0004]

However, color toners are required to have contradictory functions such that they are sufficiently melted and do not cause hot offset. Therefore, if the melting point of the toner binder resin or the melting point of the wax is too low, the photoreceptor and the fixing member are fixed. If the toner adheres to the device and the toner is too high, the toner does not melt and the agglomerates remain and the color saturation of the image decreases, so it is necessary to balance the binder resin and wax of the toner.

Further, in order to realize a color oilless fixing system, it is desired to optimize the structure of the fixing device and the material of the toner.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a color toner fixing method having a simple structure, low cost, and excellent toner releasability without using oil. And

[0007]

In order to solve the above-mentioned problems, the present invention provides at least two or more color toners of cyan, magenta, yellow and black containing a fixing resin medium as a main binder component. A fixing roller having a heat source and a surface covered with an elastic layer, the fixing rollers being arranged one above the other, the color toner is attached to the surface of the transfer medium, and the transfer medium is conveyed to the nip portion of the fixing roller, In a color toner fixing device configured to fix a toner image on a transfer medium, the color toner contains polyester resin as a main binder component and 1 to 3% by weight of Fischer-Tropsch wax. The hardness of the elastic layer is the same, and the thickness of the elastic layer of the heat roller that contacts the surface of the transfer medium is adjusted. Also a structure with a reduced thickness of the elastic layer of the heat roller in contact with the back surface of the transfer medium.

Further, the elastic layers of the heat rollers have the same thickness, and the heat rollers contacting the back surface of the transfer medium are harder than the hardness of the elastic layer of the heat roller contacting the transfer medium surface. A configuration in which the hardness of the elastic layer is increased may be used.

[0009] As a result, if a concave recess is formed on the side of the upper heat roller that comes into contact with the surface of the transfer medium, the transfer medium conveyed along the upper heat roller cannot follow and becomes difficult to wind around the upper roller. In addition, since the toner is mixed with the Fischer-Tropsch wax having good releasability, hot offset can be prevented even if heat is excessively applied by the upper and lower heat rollers.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a color image forming apparatus used in the color fixing method of the present invention. Reference numerals 1, 1 ′ are optical devices that emit laser light. Reference numerals 2 and 2 ′ are photoconductors that form an electrostatic latent image by irradiating the laser light modulated by the laser light deflection device. 3, 4, 5 and 6 are developing devices for developing an electrostatic latent image formed on the surface of the photoconductor 2 to form a toner image, 3 containing yellow toner, 4 containing black toner and 5 containing Contains magenta toner,
6 contains a cyan toner. Reference numerals 11 and 11 'denote first transfer rollers which are arranged inside the intermediate transfer drum 7 and transfer a toner image onto the surface of the intermediate transfer drum 7.

Reference numeral 8 denotes a second transfer roller, which transfers the toner images formed by the toners of the developing devices 3, 4, 5, and 6 color-superposed on the intermediate transfer drum 7 to the transfer medium 9. The transfer medium 9 is not particularly limited, and means a medium such as thin paper, thick paper, or OHP sheet for transferring. A fixing device 10 uses the color fixing method of the present invention to fix the toner image transferred on the surface of the transfer medium.

The toner contains a polyester resin as a main binder component. The polyester resin is obtained by polycondensation or copolycondensation of an alcohol component and a carboxylic acid component, and specific examples of each component used include the following.

Examples of the divalent or trivalent or more alcohol component include the following.

1) diols; ethylene glycol,
Diethylene glycol, triethylene glycol, 1,
2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediene Methanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc.

2) Bisphenols; etherified bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropyleneated bisphenol A and the like.

3) Trihydric or higher alcohols; sorbitol, 1,2,3,6-hexanetetrol, 1,4-
Sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,2. 4-butanetriol, trimethylolethane, trimethylolpropane, 1,
3,5-trihydroxymethylbenzene and the like.

As the divalent or trivalent or more carboxylic acids, divalent or trivalent carboxylic acids, their acid anhydrides or their lower alkyl esters are used, and the carboxylic acids are exemplified below.

4) divalent carboxylic acid; maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, Malonic acid, or n-butylsuccinic acid,
n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid, isododecenyl succinic acid, etc. Alkyl or alkenyl succinic acid etc.

5) Trivalent or higher carboxylic acids; 1,2,4
-Benzenetricarboxylic acid (trimellitic acid), 1,
2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,2
5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,
2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, enpol trimer acid and the like. Acid anhydrides or lower alkyl esters of these carboxylic acids can also be used.

Generally, a color toner has a low softening point in order to melt the toner sufficiently to eliminate the grain boundaries of the toner and smooth the surface, and a binder resin having a single peak of the molecular weight distribution and a narrow sharp melting property is used. It is used, and polyester resins are often used in consideration of the transparency, storage stability, and fixability of the resin.However, in the resin design as described above, simply adding wax to the toner does not However, hot offset could not be prevented, and a release agent had to be applied to the fixing roller.

However, in order to sufficiently melt the toner without applying a release agent to the fixing roller and obtain a good color image, the binder resin and the auxiliary agent in consideration of the fixing characteristics and the offset balance were examined, and as a result, It was found that the effect of using the wax obtained by the Fischer-Tropsch method on the polyester resin is effective.

The composition of the binder resin is such that the low molecular weight component has a melting function, and the high molecular weight component has elasticity to provide two functions of preventing adhesion to the fixing roller. A broad molecular weight distribution with a peak and a second peak on the polymer side is good.

The softening point of the polyester resin is 110 to 1
30 degreeC is preferable and 110-120 degreeC is more preferable. The weight average molecular weight M _W1 of the first peak is 1.
0 × 10 ^{4 to} 3.0 × 10 ⁴ , and the weight average molecular weight M _W2 of the second peak is 5.0 × 10 ^{5 to} 7.0 × 1.
0 ⁵ , the ratio M _{W of} the weight average molecular weight M _W and the number average molecular weight M _N
/ M _N is preferably 10-20.

Fischer-Tropsch wax is a wax obtained by catalytic hydrogenation of carbon monoxide using coal as a raw material, and particularly preferably has a low melting point of 90 to 110 ° C. Fischer-Tropsch wax is blended in the toner containing polyester resin as the main component to exert the effect as a viscosity reducing agent, and easily melts at the time of fixing to function as a melting initiator and also functions as a release agent. Then
The effect of improving fixability and the effect of preventing offset are obtained.
Also, since the dispersibility in the polyester resin is good,
No drum filming occurs.

The Fischer-Tropsch wax is blended in the toner of the present invention in an amount of 1 to 3% by weight, preferably 1 to
2% by weight. If the content is less than 1% by weight, the low temperature fixing property and the offset resistance cannot be improved, while if it exceeds 3% by weight, filming on the fixing roller occurs.
Fischer-Tropsch wax is available from Sazol Company of South Africa.

In the toner of the present invention, waxes other than Fischer-Tropsch wax can be mainly used as a release agent. For example, low molecular weight polyolefin wax such as polyethylene wax and polypropylene wax, and Teflon wax. Can be used.
With the above configuration, it is possible to give the toner both functions of good meltability and no hot offset due to the effects of both the binder resin and the wax. The toner of the present invention may further contain conventional components for toner, such as dyes and pigments, magnetic agents and charge control agents.

FIG. 2 shows a block diagram of the fixing device used in the present invention. The configuration of this fixing device will be described with reference to the drawings. The fixing device includes an upper roller 17 and a lower roller 18. The upper roller 17 has the halogen lamp heater 12 built in the aluminum tube 15, the outside of the aluminum tube is covered with the silicone rubber 14, and the upper part thereof is covered with the PFA tube.
The lower roller 18 has a halogen lamp heater 12 'built in an aluminum tube 15', a silicon rubber 14 on the outside of the aluminum tube, and an FLC coating on the silicon rubber 14.

In the present invention, the silicone rubber layers 14, 14 'are
The upper roller 1 has the same hardness (JIS A, same below)
By making the rubber thickness of 7 larger than that of the lower roller 18, the upper roller 17 is compressed and deformed more than the lower roller 18 to form a nip having a recess. However, the present invention is not limited to this, and the heat roller on the side in contact with the surface of the transfer medium holding the toner may be formed with another roller to form the concave portion. For example, assuming that the rubber thickness is the same, the hardness of the elastic layer of the heat roller contacting the back surface of the transfer medium is made larger than the hardness of the elastic layer of the heat roller contacting the transfer medium surface (toner image side). Is also good.

The transfer medium 9 onto which the unfixed color toner 19 has been transferred is fixed when it passes through the fixing device. However, the upper roller is compressed and deformed more than the lower roller to form a concave nip. Since the peeling angle θ when the transfer medium 9 is peeled from the nip becomes large and the melted toner does not adhere to the upper roller 17 and the transfer medium is easily released from the roller, the shape of the nip of the shape after fixing is fixed. Since the surface is smoothed like the toner 19 ', irregular reflection of light on the toner surface can be prevented and a color image with high saturation can be obtained. The toner image formed on the photoconductor by the toner of the present invention is transferred to a transfer medium and is preferably fixed by a heat roll fixing device. In this case, the fixing temperature is 12
0-170 degreeC is suitable, Preferably it is 130-160.
° C.

[0030]

EFFECT OF THE INVENTION Polyester resin as a main binder component and Fischer-Tropsch wax in an amount of 1 to 3% by weight.
A heat roller type fixing device in which the color toner for developing the electrostatic latent image and the upper roller and the lower roller are covered with an elastic layer, and the upper roller is compressed and deformed more than the lower roller to form the nip of the recess. By the fixing method of the color image forming apparatus that enables the oilless fixing by using, the toner melts without offset and a good color image is obtained, and the life of the fixing device can be extended.

[0031]

[Example 1] Toner: Binder Polyester resin Wax Fischer-Tropsch wax 1% by weight Polypropylene wax 2% by weight Softening point (T _m ) 117 ° C Fixer: Total load 50 Kgf Nip width 4 mm Roller material Upper roller PFA Tube roller Lower roller FLC Coat roller Rubber hardness 50 ° (JIS A) for both upper roller and lower roller Transfer to paper using toner and fixing device under the above conditions
A 100% image (solid image) fixing experiment was conducted to examine the fixing rate, glossiness, and the presence or absence of offset.

The fixing ratio is obtained by rubbing 10 times back and forth by applying a load of 1 kg made of brass in which the image for measurement after fixing is wrapped in cotton cloth. The image density before and after this operation was measured with a Macbeth reflection densitometer and the ratio of the densities was calculated as the fixing rate.

The gloss is measured by a gloss meter (Minolta GM-06
0) was used to measure at 60 ° and -60 ° based on JIS Z8741.

At a fixing temperature of 130 to 160 ° C., a fixing ratio of 100% and a good color image free from hot offset were obtained. In particular, an image having a glossiness of 20% or more can be obtained at a fixing temperature of 140 to 150 ° C., which is preferable. The durability of the fixing device is 3
Good results were obtained with over 10,000 copies.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image forming apparatus to which the present invention is applied.

[Fig. 2] Fixing device

[Explanation of symbols]

 1, 1 ': Optical device 2, 2': Photoconductor 3, 4, 5, 6: Developing device 9: Transfer medium 10: Fixing device 17, 18: Heat roller 12, 12 ': Heater 14, 14': Elastic Layer 19: Color toner

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G03G 15/20 102 G03G 9/08 361 103 365

Claims (3)

[Claims] 1. A cyan roller comprising a heat roller having a heat source inside and at least one surface of which is covered with an elastic layer, the heat roller being arranged above and below, and a fixing resin medium being a main binder component on the surface of the transfer medium. In a color toner fixing method, at least two kinds of color toners of magenta, yellow, and black are attached, and the transfer medium is conveyed to a nip portion of the fixing roller to fix a toner image on the transfer medium. The color toner contains a polyester resin as a main binder component and 1 to 3 wt% of Fischer-Tropsch wax is mixed, and the hardness of the elastic layer of each heat roller is the same, and the surface of the transfer medium is Elasticity of the heat roller that contacts the back surface of the transfer medium rather than the thickness of the elastic layer of the heat roller that contacts Color toner fixing method which is characterized in that to reduce the thickness of the layer. 2. A fixing roller having a heat roller internally having a heat source and at least a surface of which is covered with an elastic layer, the fixing roller having a fixing resin medium as a main binder component on the surface of a transfer medium, and cyan and magenta. In the color toner fixing method, at least two types of color toners of yellow, black, and black are attached, and the transfer medium is conveyed to the nip portion of the fixing roller to fix the toner image on the transfer medium. The color toner contains polyester resin as a main binder component and 1 to 3% by weight of Fischer-Tropsch wax. The elastic layers of the heat rollers have the same thickness and are in contact with the surface of the transfer medium. The hardness of the elastic layer of the heat roller that contacts the back surface of the transfer medium is higher than the hardness of the elastic layer of the heat roller. Color toner fixing method which is characterized in that a larger degree. 3. The softening point of the color toner is 110 to 13
0 ° C., the weight average molecular weight of the color toner in the resin medium is 3.0 × 10 ^{4 to} 9.0 × 10 ⁴ , and the weight average molecular weight distribution has at least first and second peaks. 3. The color toner fixing method according to claim 1, wherein the ratio M _W / M _N of the molecular weight M _W and the number average molecular weight M _N of the color toner in the resin medium is set to 10 to 20.