JPH04240660A - Method for fixing color copied image - Google Patents

Abstract

PURPOSE:To ensure OHP transparency in a fixing system using a heated roll made of fluororesin having advantage with respect to durability. CONSTITUTION:In a fixing system using a heated roll made of fluororesin and having <=3.0mum surface roughness Rz, a color tone contg. a resin having 5X10<5>-3X10<6> P melt viscosity at 100 deg.C, >=45mol.wt. distribution Mw/Mn (Mw is wt. average mol.wt. and Mn is number average mol.wt.) and 1,000-4,000 number average mol. wt. Mn as a binder component is used. OHP transparency, fixability and anti-offsetting property can be ensured by using the toner resin having the specified physical properties.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for fixing color copy images.

0002

2. Description of the Related Art Conventionally, in the fixation of copied images in color copying machines, the fixed toner itself has excellent translucency, for example, the translucency of color toner images on OHP sheets (hereinafter referred to as OHP translucency). ) requires the same level of translucency. In order to ensure this excellent light transmittance, a system is used in which a sharp melt toner with a low melt viscosity is used in a silicone rubber heating roller. In order to ensure this OHP transparency, it is necessary to use a heating roller with a high surface smoothness to make the surface of the toner image uniform.

Furthermore, in the above system, the surface of the heating roller is made of silicone rubber and a toner with a low melting viscosity is used, so that the toner easily adheres to the surface of the heating roller and offset occurs. Therefore, it is necessary to apply a large amount of a mold release agent such as silicone oil, which has a high affinity with silicone rubber and is relatively inexpensive, to the surface of the heating roller.

0004

[Problems to be Solved by the Invention] However, since the above-mentioned conventional system uses a sharp melt toner with a low melt viscosity, the mechanical strength of the toner is low and the cohesive force of the toner suddenly decreases. . For this reason, there are problems in that the fixing property between the toner and the recording paper is reduced, and the releasing property between the toner and the heating roller is reduced, making it easy for offset to occur.

[0005] Furthermore, since a large amount of silicone oil is used to improve mold releasability, there is also the problem that oil swelling and rubber deterioration occur due to the oil, shortening the life of the heating roller. By the way, in the Teflon roller fixing system that is the mainstream in black-and-white copying machines, there is no need to apply a release agent to the roller surface because Teflon has excellent release properties from toner. Therefore, the problem caused by the oil does not occur, which is advantageous in terms of the life of the heating roller.

The present invention has been made in view of the above-mentioned circumstances, and its technical problem is to create a color copy image that can ensure OHP transparency using a fluororesin-based heating roller that is advantageous in terms of durability. The purpose is to provide a fixation method.

[0007]

[Means for Solving the Problems] The color image fixing method of the present invention includes a heating roller whose surface is made of fluororesin and has a surface roughness of Rz 3.0 μm or less, and a pressure roller that is in pressure contact with the heating roller. In a color copy image fixing method in which the toner image is fixed on the recording paper by passing the recording paper holding the toner image so that the toner image side faces the heating roller, the melt viscosity at 100°C is 5. ×105 to 3×106 poise, molecular weight distribution (Mw/Mn, Mw: weight average molecular weight, M
n: number average molecular weight) is 45 or more, number average molecular weight (Mn
) is from 1,000 to 4,000 as a binder component.

The resin serving as the binder component of the color toner can be a styrene-acrylic copolymer resin or a polyester resin. When comparing a styrene-acrylic copolymer resin and a polyester resin, when both have the same melt viscosity, the polyester resin is superior in terms of heat resistance and mechanical strength of the resin. For this reason, it is preferable to use a polyester resin as the toner resin. In addition, when using styrene-acrylic copolymer resin, the above number average molecular weight (Mn) is 3000 to 40.
It is preferable to set it to 00. In addition, when using polyester resin, the number average molecular weight (Mn) should be 1000.
~4000. In addition, using polyester resin, the number average molecular weight (Mn) is 3000 to 40.
When it is set to 00, it becomes possible to particularly ensure the mechanical strength of the resin.

Examples of the styrene monomer constituting the styrene-acrylic copolymer resin include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, and 2,4-dimethylstyrene. , p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, Examples include styrene and its derivatives, such as p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene, among which styrene is most preferred.

The acrylic monomers constituting the styrene-acrylic copolymer resin include acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, and n-octyl acrylate. , acrylic acid and its derivatives such as dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate,
Propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, propyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, methacrylic acid Examples include methacrylic acid and its derivatives such as diethylaminoethyl, (meth)acrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide, and the like.

The above polyester resin is synthesized from, for example, a polyol component and dicarboxylic acid, and the polyol component includes ethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, and 1,4-propylene glycol. Butanediol, 1,4-bis(hydroxymethyl)cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethylated bisphenol A, etc. can be used, and as dicarboxylic acid components, maleic acid, fumaric acid, mesaconic acid,
Citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, malonic acid, 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid,
1,2,4-cyclohexanetricarboxylic acid, 1,2,
5-cyclohexanetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,3-dicarboxy-2-methyl-2-methylcarboxypropanetetra(methylcarboxy)methane, etc. can be used.

[0012] Further, as the coloring agent used in the above color toner, for example, C.I. I. Pigment Yellow 12, C. I. Pigment Yellow 13 etc. as a red colorant and C.I. I. pigment red 122,
C. I. Pigment Red 57:1, C.I. as a blue colorant. I. Pigment Blue 15 and the like can be mentioned, but the colorant is not limited to these, and pigments, dyes, etc. of various colors conventionally used in translucent color toners can be used. In addition to the coloring agent, desired additives such as a charge control agent may be added to the color toner. The amounts of these colorants and other necessary additives can be the same as conventional ones.

[0013] The above-mentioned toner is usually prepared as a toner having an average particle size of 4 to 25 μm by kneading, pulverization, or the like. Note that the fixing method of the present invention has high surface smoothness (Rz3.
(0 μm or less) Use a fluororesin heating roller.

[0014]

[Operation] In the color image fixing method of the present invention, the molecular weight distribution of the resin serving as the binder component of the color toner used is over a very wide range of 45 or more. As a result, the polymer side is widened in order to ensure mold releasability and prevent offset, and to ensure the cohesive force of the resin and maintain the fixing strength of the toner. In order to ensure its properties, the overall molecular weight is reduced. In addition, 10
When the melt viscosity at 0°C is less than 5 x 105 poise, or when a styrene-acrylic copolymer resin is used as the resin, the number average molecular weight is less than 3000, or when a polyester resin is used as the resin. If the number average molecular weight is less than 1000, the cohesive force of the resin cannot be ensured, resulting in lower fixing properties, as well as poorer releasability and lower offset resistance. Further, when the melt viscosity at 100° C. is larger than 3×10 6 poise or when the number average molecular weight is larger than 4000, OHP translucency cannot be ensured.

[0015] Furthermore, styrene having a molecular weight distribution of 47
FIG. 2 shows the relationship between the melt viscosity at 100° C. and the number average molecular weight of the acrylic copolymer resin. The color image fixing method of the present invention uses a color toner having a toner resin with defined physical properties as a binder component.
HP transparency, fixing properties, and offset resistance can be ensured.

[0016]

[Examples] Examples of the present invention will be described below. (Example 1) Styrene-acrylic resin (Mn≒3500, Mw
/Mn = 47), 100 parts of colorant (manufactured by Dainichiseika,
Seikafast Red. 8040), 2 parts of a charge control agent (Bontron E-81, manufactured by Orient Chemical Co., Ltd.), and 4 parts of low molecular weight PP wax (Viscol 330P, manufactured by Sanyo Chemical Co., Ltd.) were heated and kneaded in a three-roll mill. The powder was crushed and classified to obtain a color toner having a particle size of 12 μm.

The melt viscosity of this toner at 100° C. was measured using a descending flow tester melt viscosity measuring device, and the result was 2×1.
It was 06 poise. The above toner was transferred to a Minolta copier (EP-5400) equipped with the fixing device shown in Figure 1.
), and after forming an image on an OHP sheet and fixing it, the light transmittance, fixing property, and offset resistance were evaluated. The results are shown in Table 1. In the table, in the evaluation of OHP translucency, ◯ indicates that the color was clear and the translucency was good, and × indicates that it was darkened. Further, in the evaluation of fixability, ○ indicates that white defects were present only in the folded portion, and × indicates that white defects were observed in the folded portion. Further, in the evaluation of offset resistance, ◯ indicates that no offset occurred, and × indicates that offset occurred.

The above-mentioned fixing device is composed of a heating roller 1 having a built-in heater 11 and a pressure roller 2, and both rollers are pressed together by a biasing spring 3 with a pressure of 30 kg on one side and 60 kg on both rollers. ing. The heating roller 1 is made of an aluminum core 12 (outer diameter 39.6 mm, length 318 m).
PTFE-based fluororesin layer 1 with a thickness of 30 μm on the surface of
It is coated with 3. The surface roughness of the heating roller 1 is polished to Rz 2.5 μm. Further, a temperature measuring element 4 and a separating claw 5 are installed on the surface of the heating roller 1. On the other hand, the pressure roller 2 is formed by covering the surface of an iron core metal 21 (outer diameter 30 mm, length 320 mm) with a silicone rubber layer 22 having a thickness of 5 mm. The fixing speed in this fixing device is 110 mm/sec. (Comparative Example 1) The surface roughness of the heating roller of Example 1 was set to R
The same evaluation as above was performed under the same conditions as in Example 1 except that z was set to 3.5 μm. The results are also shown in Table 1. (Comparative Example 2) A toner was prepared in which the Mn of the styrene-acrylic resin of Example 1 was changed to 2500 (Mw/Mn≈47), and the same evaluation as in Example 1 was performed under the same conditions. The results are also shown in Table 1. The melt viscosity of this styrene-acrylic resin at 100°C is 1.
It was 1×106 poise. (Comparative Example 3) Mn of the styrene-acrylic resin of Example 1 was 3500, M
A toner with w/Mn≈40 was prepared and evaluated in the same manner as in Example 1 above. The results are also shown in Table 1. The melt viscosity of this styrene-acrylic resin at 100°C is 1.3 x 106 poise
Met. (Comparative Example 4) A toner was prepared in which the Mn of the styrene-acrylic resin of Example 1 was changed to 4200 and Mw /Mn ≈45, and the same evaluation as in Example 1 was performed under the same conditions. The results are also shown in Table 1. The melt viscosity of this styrene-acrylic resin at 100°C was 3.5 x 106 poise.

[0019]

[Table 1] In Example 1, OHP translucency and fixing properties were good without applying oil to the heating roller, and no offset occurred.

On the other hand, in Comparative Example 1, since the surface roughness of the heating roller is as rough as Rz 3.5 μm, the surface of the toner fixed on the OHP sheet becomes uneven, and the OHP translucency deteriorates due to the influence of light reflection, etc. decreased. Further, in Comparative Example 2, the number average molecular weight of the resin as a binder component of the color toner is as small as 2,500. For this reason, the cohesive force of the resin was low, and the fixing ability between the toner and the OHP sheet was reduced, and the releasability between the toner and the heating roller was also reduced, causing offset.

Furthermore, in Comparative Example 3, the molecular weight distribution of the resin as a binder component of the color toner was as small as 40. As a result, the cohesive force decreased and offset occurred. Furthermore, in Comparative Example 4, the number average molecular weight of the resin as a binder component of the color toner was as large as 4200, and 10
The melt viscosity at 0°C is also as high as 3.5 x 106. For this reason, the toner is not completely melted and does not form a film.
OHP translucency decreased.

[0022]

As described in detail above, the color copy image fixing method of the present invention uses a fluororesin-based hot roller fixing system that is advantageous in terms of durability, and has excellent OHP translucency, fixing performance, and offset resistance. It became possible to secure the Therefore, highly reliable image fixing can be performed for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a side view of a fixing device used in an example.

FIG. 2 is a graph showing the relationship between melt viscosity at 100° C. and number average molecular weight of styrene-acrylic resin.

[Explanation of symbols]

1 is a heating roller, 2 is a pressure roller 2, and 13 is a fluororesin layer.

Claims (1)

[Claims] [Claim 1] The surface is made of fluororesin and Rz3.0
By passing a recording paper holding a toner image between a heating roller having a surface roughness of μm or less and a pressure roller that is in pressure contact with the heating roller so that the toner image surface faces the heating roller, the toner can be removed. In a color copy image fixing method for fixing an image onto the recording paper, the melt viscosity at 100°C is 5 x 105 to 3 x 106 poise.
, a color toner containing a resin as a binder component having a molecular weight distribution (Mw/Mn, Mw: weight average molecular weight, Mn: number average molecular weight) of 45 or more and a number average molecular weight (Mn) of 1000 to 4000 is used. A method for fixing a color copy image.