JP2010134213A - Fluororesin tube and pressure member using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluororesin tube that prevents an offset phenomenon and prevents soil accumulation on the surface of a pressure member, such as a pressure roller, and to provide the pressure member using the fluororesin tube. <P>SOLUTION: Conductive materials are dispersedly mixed into a fluororesin, and the fluororesin tube is molded of the fluororesin so that the gloss value may be ≥69, and the light absorption coefficient may be ≥0.011(1/μm), the pressure member has the fluororesin tube disposed as the outermost layer thereof. When using the fluororesin tube for the pressure member, such as the pressure roller 18, in a thermal fixing part, both of soiling properties and offset characteristics of the surface of the pressure member are evaluated as good. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fluororesin tube used in a heat fixing part of an electrophotographic copying machine, a laser beam printer or the like, and a pressure member using the same.

  FIG. 1 is a cross-sectional view of a fixing roller and a pressure roller in a heat fixing unit. The fixing roller 16 is provided with a release layer 28 made of a fluororesin such as PFA on a cored bar 26, and a heater 30 is provided in the cored bar 26. The pressure roller 18 has a core rubber 22 provided with a silicone rubber elastic layer 24 and a tube 20 made of a fluororesin such as PFA. The pressure roller 18 is pressed against the fixing roller 16 to form a nip width N. The paper with the toner attached is sequentially passed through the nip width N.

  As shown in FIG. 1, powdery toner 14 made of a thermoplastic resin kneaded with pigments deposited and deposited by electrostatic force on the surface of paper 12A, 12B is disposed oppositely at a heat fixing portion. By passing between the fixing roller 16 and the pressure roller 18, it is melted by pressure and heat and fixed to the papers 12 </ b> A and 12 </ b> B.

  The fixing roller 16 that is in direct contact with the toner 14 attracts the toner charged to a reverse voltage by the charge accumulated by frictional charging or the like and adheres to the roller surface, and doubles on the trailing edge of the paper 12A and the subsequent paper 12B. An offset phenomenon (hereinafter simply referred to as an offset) that transfers an image may occur.

  Further, when continuous paper passing is performed with the offset occurring, the toner adhering to the surface of the fixing roller 16 is added from the gap between the rear end of the paper 12A being passed through and the front end of the succeeding paper 12B. Transfering to the pressure roller 18 side, toner may accumulate on the peripheral surface of the pressure roller 18 as dirt, and the surface of the fixing roller and the back of the succeeding paper may be stained.

  As a measure for preventing or reducing deterioration in image quality due to offset and contamination of the back side of the paper, the outermost periphery of the pressure roller 18 paired with the fixing roller 16 is coated with a material having reduced resistivity, and the coated surface A means for preventing static electricity from accumulating on the surface of the fixing roller 16 has been proposed by forming an electrically conductive circuit in the metal casing of the main body of the electrophotographic copying machine or laser beam printer.

Further, a conductive PFA tube to which carbon is added is used as the surface material of the pressure roller 18. An example of the recommended value of the resistivity of the conductive PFA tube to which carbon is added is E14 to 17 Ω-cm (see Patent Document 1). Further, a technique related to a fluororesin tube material necessary for manufacturing this roller is also known (see Patent Document 2).
JP-A-6-167901 JP 59-198118

  The problem that remains even after making full use of the above-mentioned conventional technology is the stability of quality. That is, if the amount of carbon to be added is large or the dispersibility is poor and carbon is exposed on the tube surface, the accumulation of dirt on the pressure roller surface is promoted. On the other hand, if the amount of carbon is small, the effect of preventing charging of the roller is reduced.

  The present invention has been made in order to solve the above-described problems. A fluororesin tube that prevents the occurrence of an offset phenomenon and does not deposit dirt on the surface of a pressure member such as a pressure roller, and a pressure using the same. An object is to provide a member.

The following configurations are means for solving the above-described problems.
<Configuration 1>
A fluororesin tube characterized in that a conductive substance is dispersed and blended in a fluororesin, and is molded so that a gloss value is 69 or more and an absorbance coefficient is 0.011 (unit: 1 / μm) or more.

  When used for a pressure member such as a pressure roller of a heat fixing unit, good evaluation is obtained for both the dirtiness and offset characteristics of the surface of the pressure member.

<Configuration 2>
The fluororesin tube according to the first aspect, wherein PFA is used as the fluororesin, and a predetermined amount of carbon is dispersed and blended with the PFA and molded.

<Configuration 3>
A pressure member that is disposed and used with a nip width facing the outer peripheral surface of the fixing roller in the heat fixing portion, and the fluororesin tube described in Configuration 1 or Configuration 2 is provided in the outermost layer A pressure member characterized by that.

  A pressurizing member having good evaluation both in terms of surface dirtiness and offset characteristics can be obtained. That is, for example, it is possible to stably secure a mechanism for allowing static electricity accumulated on the surface of the fixing roller to escape through the surface of the pressure roller, to prevent the occurrence of an offset phenomenon, and to prevent dirt from being accumulated on the surface of the pressure roller.

<Configuration 4>
The pressure roller according to Configuration 3, comprising a cored bar, a silicone rubber elastic layer provided on the cored bar, and the fluororesin tube provided on the outer periphery of the silicone rubber elastic layer A pressure member characterized by the above.

The present invention stably secures a mechanism for discharging static electricity accumulated on the surface of the fixing roller through the surface of a pressure member such as a pressure roller to prevent the occurrence of an offset phenomenon. A fluororesin tube that does not deposit dirt on the surface of the pressure member and a pressure member using the same.
Hereinafter, the present invention will be described based on examples.

  Mitsui-DuPont Fluorochemical Pellets C9058 (trade name of conductive PFA pellets) and Pellet 950HPplus (trade name of insulating PFA pellets) were weighed at a predetermined weight ratio, stirred for 10 minutes and mixed. . Thereafter, the mixed PFA pellets were extruded with an extruder to obtain a conductive PFA tube.

  Nine types of conductive tubes were prepared by changing the mixing ratio of C9058 and 950HPplus, and the obtained conductive PFA tubes were respectively provided with a cored bar 22 as shown in FIG. Nine pressure rollers 18 were formed by covering the outermost layer 20 of the roller having the rubber elastic layer 24. As shown in FIG. 1, the pressure roller 18 is used so as to face the fixing roller 16.

  Each gloss value and absorbance coefficient of the nine types of conductive tubes were measured by a predetermined method, and each of the dirtiness and offset characteristics of each pressure roller surface was evaluated.

  FIG. 2 shows the gloss values and absorbance coefficients of the respective conductive tubes of the nine pressure rollers (Comparative Examples 1 to 5 and Examples 1 to 4), and the pressure rollers using these conductive tubes. Each evaluation of the surface soiling property and the offset property is shown.

  The measurement methods and evaluation criteria for the dirtiness and offset characteristics of the pressure roller surface were as follows. The offset characteristics are evaluated by visual judgment of the transfer condition to the paper 12, and the dirtiness on the surface of the pressure roller 18 is evaluated by visual judgment of the degree of adhesion of the toner 14 to the pressure roller 18, as shown below. The level is represented by x, △, ○.

(1) Level of dirtiness on the surface of the pressure roller 18 × ... A paper tester was placed in an environment of normal temperature (20 ° C) and normal humidity (60% RH) to fix the image of the prepared standard chart. At the time of passing 20,000 sheets, the toner 14 adheres or accumulates as a dirt on a part or the entire surface of the roller.
△ ... When a paper tester is placed in a room temperature (20 ° C) and normal humidity (60% RH) environment and the standard chart image prepared is fixed, the surface of the roller is The toner 14 adheres or accumulates as a dirt on a part or the entire surface.
○ ... When a paper tester is placed in a room temperature (20 ° C) and normal humidity (60% RH) environment and the standard chart image prepared is fixed, the surface of the roller is passed when 40,000 sheets are passed. Toner 14 dirt is not found.

(2) Level of offset characteristics × ... When a paper-sheet tester is placed in a room temperature (20 ° C) and normal humidity (60% RH) environment, and a grid-like image with 2 mm intervals is fixed on the paper 12, When 10,000 sheets are passed, double transfer (dirt image) occurs on the paper 12.
△ ... When a paper tester is placed in a room temperature (20 ° C) and low humidity (20% RH) environment and a grid-like image with a spacing of 2 mm is fixed on the paper 12, when 10,000 sheets are passed, Double transfer (dirt image) occurs on the paper 12.
○ ... Double transfer (stain of image) does not occur under any of the above conditions.

  When used for a pressure member such as the pressure roller 18 of the heat fixing unit, good evaluation is obtained for both the dirtiness and offset characteristics of the surface of the pressure member. That is, as shown in FIG. 2, the gloss value is 69 or more, the dirtiness of the surface of the pressure roller 18 is good, and the offset characteristic is good when the absorbance coefficient is 0.011 (1 / μm) or more. .

  Therefore, by combining the measurement values obtained by the respective measurement methods, it is possible to obtain the pressure roller 18 having a favorable evaluation in terms of both dirtiness and offset characteristics on the surface of the pressure roller 18. That is, for example, a mechanism for stably discharging static electricity accumulated on the surface of the fixing roller 16 through the surface of the pressure roller 18 can be stably ensured, the occurrence of an offset phenomenon can be prevented, and dirt can not be accumulated on the surface of the pressure roller 18. can get.

The gloss value is also referred to as glossiness, and was determined according to the provisions of “4. Measurement method” of JIS Z 8741 (mirror glossiness—measurement method).
The gloss value is a physical property value reflecting surface irregularities. As the surface irregularities increase, the gloss value decreases. When adding conductive pellets as a master batch to impart conductivity to the insulating fluororesin pellets, increasing this ratio will increase the aggregated diameter of the particles that are the conductivity-imparting material and increase the surface roughness. The value becomes smaller.

  At this time, the probability that the conductivity-imparting material is exposed to the surface is increased, and using this as a foothold, the filler in the paper such as toner, paper powder or talc becomes dirty and adheres and accumulates. By being transferred to the fixing member that touches the back side of the paper or the image, it is connected to dirt during printing.

On the other hand, the absorbance coefficient α is a physical property value that is inversely proportional to the light transmittance, and has the following relationship with the absorbance A of the object.
A = log ₁₀ (I ₀ / I) = αL
I ₀ = incident light intensity
I = transmitted light intensity α = absorbance coefficient
L = material thickness (μm)
The absorbance coefficient depends not on the surface but on the state in the cross-sectional direction. The larger the conductivity imparting material is, the larger the value becomes, and the larger the value becomes evenly dispersed. If the absorbance coefficient is 0.011 (1 / μm) or more, the amount of the conductivity-imparting material is sufficient, the dispersion and connection are evenly distributed, and the charging potential can be stably reduced.

  The present invention can be applied to well-known pressure belts, bar platens, and the like in addition to the pressure roller disposed opposite to the fixing roller in the heat fixing unit. That is, the pressure belt 32 is formed by winding a laminated belt 34 disposed opposite to the fixing roller 16 around a pressing member 36 and a driven roller 38 in a substantially triangular shape as shown in FIG. The resin tube is provided in the outermost layer of the laminated belt 34.

  As shown in FIG. 4, the bar platen 40 is provided in contact with the outer periphery of the fixing roller 16 and fixed with a nip width. An elastic body 44 and a surface layer 46 are provided on a metal support 42. Therefore, the fluororesin tube according to the present invention is provided as the surface layer 46.

It is sectional drawing which shows the fixing roller and pressure roller in a heat fixing part. It is a figure which shows each evaluation of the dirt value and offset characteristic of the surface of each pressurization roller which uses the measured value of each type of fluororesin tube, the light absorbency coefficient, and these electroconductive tubes. It is sectional drawing which shows the fixing roller and pressure belt in a heat fixing part. It is sectional drawing which shows the fixing roller and bar platen in a heat fixing part.

Explanation of symbols

12A, 12B Paper 14 Toner 16 Fixing roller 18 Pressure roller 20 Fluorine resin tube 22 Core metal 24 Elastic layer 26 Core metal 28 Release layer 30 Heater 32 Pressure belt 34 Lamination belt 36 Press member 38 Drive roller 40 Bar platen 42 Metal support Body 44 Elastic body 46 Surface layer

Claims (4)

  A fluororesin tube characterized in that a conductive substance is dispersed and blended in a fluororesin, and is molded so that a gloss value is 69 or more and an absorbance coefficient is 0.011 (unit: 1 / μm) or more. In the fluororesin tube according to claim 1,
A fluororesin tube, wherein PFA is used as the fluororesin, and a predetermined amount of carbon is dispersed and blended in the PFA as the conductive material. A pressure member that is arranged and used with a nip width facing the outer peripheral surface of the fixing roller in the heat fixing unit,
A pressurizing member comprising the fluororesin tube according to claim 1 or 2 as an outermost layer. The pressurizing member according to claim 3,
A pressure member comprising a cored bar, a silicone rubber elastic layer provided on the cored bar, and the fluororesin tube provided on the outer periphery of the silicone rubber elastic layer. .

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