JPH0695546A - Fixing roller - Google Patents

Abstract

PURPOSE:To provide a fixing roller having excellent durability in the bond of a fluoric resin sleeve. CONSTITUTION:A fluoric resin sleeve 4 having a thickness of 0.1mm or less is put on a rubber layer 3 to form a fixing roller, wherein the wetting index of an etching processed layer on the inside of the sleeve is made over 54 after a 150 deg.C heat treatment test or our hr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing roller having an outer periphery coated with a fluororesin sleeve for use in an electronic copying machine or the like.

[0002]

2. Description of the Related Art Heretofore, as a fixing roller for an electronic copying machine or the like, there has been known a roller in which an outer circumference of a rubber roller containing a core metal is covered with a fluorine resin sleeve in order to improve the releasability of toner.

In the conventional roller of this type, both ends of a fluororesin sleeve having an outer shape smaller than the inner diameter of the cylindrical mold loaded inside the inner peripheral surface of the cylindrical mold are fixed to a side mold holding a core metal. In this state, the rubber material is injected and filled into the annular space between the cored bar and the sleeve at a high pressure, and the sleeve is integrated with the inner peripheral surface of the cylindrical mold while expanding the sleeve by the filling pressure. It is molded by being made into a material (Japanese Patent Publication No. 50-7097 and Japanese Patent Publication No. 51-27276).

However, in the conventional fixing roller manufactured by such a method, particularly when a thin-walled fluororesin sleeve having a wall thickness of 0.1 mm or less is used, the sleeve has a low tensile stress, so that the sleeve and the rubber material are combined. However, there is a drawback that the fixing roller has a short service life because peeling frequently occurs between the sleeve and the rubber layer.

For this reason, recently, in order to extend the life of the fixing roller, the inner surface treatment of the fluororesin sleeve has been studied. If the initial wetting index is in the range of 56 to 70, stable adhesion durability as the fixing roller is obtained. I know I can get it.

[0006]

The etching-treated fluororesin sleeve having a wetting index in this range generally uses an alkali metal solution treatment method using a liquid ammonia solution of sodium metal.

However, in the alkali metal solution treatment method using a liquid ammonia solution of sodium metal, a wettability index of 72 is often obtained depending on the treatment conditions.

Further, the wettability index is 72 in the alkali metal solution treatment method using the liquid ammonia solution of sodium metal.
It tends to be possible to stabilize the treatment process.

However, when a fluorine resin sleeve having a wettability index of 72 is used as a fixing roller, a problem that adhesive peeling occurs between the sleeve and the silicone rubber in the initial stage rarely occurs.

In view of the stability of the above-described etching process, the present invention is a conventional fixing roller using a fluororesin sleeve having a wetting index of 72, and the sleeve of the fixing roller is peeled off with a relatively small number of copies. To solve the problem that may occur.

[0011]

DISCLOSURE OF THE INVENTION The present invention has been studied in order to determine the durability of a fluororesin that has been subjected to an etching treatment under various treatment conditions so that the durability can be judged in advance.

That is, in a fixing roller having a fluorine resin layer on the surface layer, the adhesion durability of the fixing roller was examined by paying attention to the fact that it is always peeled from between the surface fluorine resin layer and the elastic layer (lower layer). .

That is, in chemical etching using a liquid ammonia solution of metallic sodium or a naphthalene-THF solution of metallic sodium, since fluorine ions are detected in the treatment liquid after the treatment, it is considered to be a defluorination reaction of the fluororesin, Carbon double bonds are formed on the treated surface.

Such chemical etching is performed by the following chemical formula 1.

[0015]

[Chemical 1]

As described above, it is considered that fluorine reacts with an alkali metal or the like from the surface to remove fluorine as NaF to form a double bond or carbon in the surface layer.

The double bond or carbon serves as an active site, and the silicone rubber and the fluororesin are firmly adhered to each other by the silicone-based adhesive. However, the heat resistance of the fluororesin-treated layer increases the adhesion durability. It is considered to depend on it.

Actually, when the silicone rubber and the fluororesin are adhered with a silicone-based adhesive, the adhesion durability is 1,000 hours or more at 200 ° C., although it depends on the kind of the adhesive and the treatment.

This is because when the silicone rubber and the fluororesin are adhered by the silicone adhesive, the carbon double bond, which is the active point, and the silicone adhesive are strongly chemically bonded.

However, after the chemically treated fluororesin is heated at 200 ° C. for 1,000 hours, it has no adhesiveness because the active sites are completely deteriorated.

Therefore, the present inventor has studied the heat resistance of the chemically treated fluororesin, particularly the PFA sleeve.
Since the surface tension (wetting index) changes after a heat resistance test under relatively mild conditions, it is possible to obtain a fixing roller having a fluororesin on the surface layer with excellent durability by grasping the degree of this change. The present invention has been completed and the present invention has been completed.

According to the present invention, in a fixing roller coated with a fluororesin sleeve having a thickness of 0.1 mm or less as the fluororesin sleeve layer 4 covering the outer periphery of the rubber layer 3, the etching treatment layer inside the fluororesin sleeve is wet. A fixing roller 1 is proposed which uses a sleeve holding 54 or more after a heat resistance test at an index of 150 ° C. for 4 hours.

[0023]

[Function] In a fixing roller coated with a fluororesin sleeve having a thickness of 0.1 mm or less as the fluororesin sleeve layer 4 covering the outer periphery of the rubber layer 3, the etching treatment layer inside the fluororesin sleeve is 150 ° C. for 4 hours. By using a sleeve having a wetting index of 54 or more after the heat treatment test, the adhesiveness between the fluororesin sleeve 4 and the rubber material of the rubber layer 3 is significantly improved.

[0024]

EXAMPLE A fixing roller 1 has a metal cored bar 2 having an outer periphery covered with a rubber layer 3, and the outer periphery of the rubber layer 3 having a thickness of 0.
A fluororesin sleeve 4 of 1 mm or less is covered.

The rubber layer 3 is made of a heat-vulcanizable silicone rubber having a hardness of 40 degrees (JIS A type), and the sleeve 4 has a wetting index of 54 after a heat treatment test at 150 ° C. for 4 hours. The above-mentioned etched PFA sleeve is used.

First, by changing the treatment conditions, particularly the treatment temperature, etc. in the alkali metal solution treatment method using a liquid ammonia solution of sodium metal, Examples 1 to 1 having different materials and wetting indexes shown in Table 1 were used. 10 and Comparative Example 1
A sample of was obtained.

The wetting index of these samples is 56-72 dyne / cm
Met.

Further, as a reference, the sample was treated with a tetrahydrofuran solution of metallic sodium-naphthalene to obtain the sample shown in Comparative Example 2.

The wetting index of Comparative Example 2 was 50 dyne / cm.

Next, these samples were treated at 120 ° C. and 150 ° C., respectively.
Heat treatment is performed at ℃, 170 ℃, 180 ℃ for 4 hours,
The change of each wetting index and color tone was measured.

Table 1 shows the wetting index of the sleeves used in Examples 1 to 10 and Comparative Examples 1 and 2, and Table 2 shows the results of measuring the color tone of these samples by Macbeth density.

[0032]

[Table 1]

[0033]

[Table 2]

From the results shown in Table 1, there is no change from the initial (purchased) value in the heat treatment at 120 ° C. for 4 hours, and all samples are 30 or less in the heat treatment at 180 ° C. for 4 hours. It turns out that it is impossible to do
As shown in Examples 1 and 10, in the heat-resistant treatment for time, there are some values that are close to less than 30 at which the later-described wetting index cannot be measured, so there is concern as a test condition.

On the other hand, the heat treatment at 150 ° C. for 4 hours does not cause the above-mentioned problems, and it can be seen that it is suitable as a test condition.

The heat resistance test conditions for the fluororesin treated layer are not limited to 150 ° C. for 4 hours, but similar thermal history conditions, such as 100 ° C. for 100 to 160 hours and 120 ° C. for 24 to 40 hours, 170 ° C.
Conditions such as 45 to 100 minutes at ℃ may be used, but if the temperature is too low, the test time will be longer and the result determination will be delayed.

Further, at a high temperature for a short time, for example, at 200 ° C., 10
Under the condition of minutes, there is a possibility that the measurement results will vary due to a slight difference in the test time.

Judging from the above, a total of 4
It is considered that the heat-resistant treatment for a long time is the most conditionally stable and appropriate result can be obtained.

The method of measuring the wetting index of the sleeve 4 used in the above experiment is defined in ASTM D2578 and JIS K6768. The wetting index referred to here is a series of standard values in which the surface tensions are different in order. It is a numerical value of the surface tension (dyne / cm) of a standard solution which was determined to be applied with the solution on the surface of the film and just wet the film.

The standard solution having a wetting index of 31 to 56 is a mixture of formamide and ethyl cellosolve (ethylene glycol monoethyl ether).
For 70, a mixture of formamide and distilled water is used.

For example, the standard solution having a wetting index of 50 is a mixture of formamide 90.7 V / V% and ethyl cellosolve 9.3 V / V%, and the standard solution having a wetting index 66 is formamide 18.2 V / V.
%, A mixed solution of distilled water 81.8V / V%.

Ethyl cellosolve is used as the standard solution having a wetting index of 30, and distilled water is used as the standard solution having a wetness index of 72.

Since the standard solution of the wetting index is only from 30 to 72, samples less than 30 or more than 72 cannot be measured.

Further, the standard solution contains 0.03% of a highly colored dye such as Victoria Pure Blue PO as a colorant.
It is added at the following concentrations.

In the measured values of the wetting index shown in Table 1, for example, the wetting index of the sample under the heat treatment condition of 180 ° C. for 4 hours is
When 30 standard solutions were applied, the surface of the sample could not be wetted and the solution was completely repelled, so it was judged to be less than 30, and indicated as <30.

On the other hand, Examples 8 to 10 and Comparative Example 1
The initial wetting index is 72, which means that the standard solution with a wetting index of 72 wets the sample.

In general, when the surface of the fluororesin is chemically etched, the treated product becomes brown or black, but the relationship between the color tone and the wetting index does not necessarily match.

That is, the reflection density by the Macbeth densitometer shown in Table 2 changes from 0.00 to 2.50 as the color tone changes from white to black, but as shown in Example 10, the wetting index is high. In some cases, the reflection density is low (that is, the color is light).

Further, when the sample is heated, the color tone of the treated layer of the fluororesin becomes lighter, and the tendency tends to become larger as the heating temperature becomes higher, but the degree of change is different from that of the wetting index shown in Table 1. It was found that the heat resistance of the fluororesin treated layer cannot be judged by the change in color tone.

Next, in order to evaluate the durability of each of the above samples, a paper passing test by a copying machine was conducted, and the results of Table 3 were obtained.

As a method of evaluating the durability in this paper passing test, the diameter of the heat roller was 50 mm, and the surface temperature was 2
With a specification of 00 ℃, nip load of 60kgf / total, and peripheral speed of 250mm / sec, blank paper is passed between fixing rollers at a speed of 50 sheets / 1 minute, and peeling between sleeve 4 and rubber layer 3 is evaluated as life. did.

A roller having an outer diameter of 50 mm, a rubber layer thickness of 6 mm and a rubber layer length of 340 mm was used as the pressure roller in the fixing roller of the evaluation method.

[0053]

[Table 3]

As can be seen from the results shown in Table 3, the roller of the present invention has a very good adhesion between the fluororesin sleeve and the rubber layer and has a long-term durability. No such uneven fixing, paper wrinkle, curl, etc. occurred.

In the present invention, the fluororesin sleeve 4
The etching treatment method for the inner surface of is not particularly limited, and an alkali metal solution treatment method using a liquid ammonia solution of metal sodium is generally used.

Further, a method of treating with molten sodium hydroxide, an alkali metal solution treating method of bringing a mercury amalgam of an alkali metal such as lithium into contact with a fluororesin, and the like can be applied.

Although not chemical etching, corona discharge treatment or plasma discharge treatment can be applied.

The wetting index mentioned here is a value measured immediately before the bonding process between the rubber and the sleeve.

Generally, the wetness index tends to be high immediately after the chemical etching of the fluororesin and is stable after aging for several weeks. The extent of the difference immediately after etching and after aging cannot be determined in any way, but a decrease of 6 dyn / cm is illustrated when the fluororesin is treated with a liquid ammonia solution of metallic sodium.

In the method of treating with a liquid ammonia solution of sodium metal, the reaction proceeds too much when the treatment time is long, and in an extreme case, the color of the treated layer changes to black and the treated layer is delaminated.

It is considered that the treated layer in this case is transformed into an organic compound containing no fluorine atom, and in such a state, the wetting index shows 72 or more, but there is no adhesion durability, and the reason is that the treated layer is It is presumed that the heat resistance of is deteriorated to the level of an organic polymer such as ordinary polyethylene.

In the present invention, the rubber of the rubber layer 3 is not particularly limited, but normally silicone rubber is used in consideration of heat resistance and compression set.

As the silicone rubber, any of a thermal vulcanization type, an addition type and a condensation type can be used. However, since the condensation type is not a deep cure type, it is preferable to use the thermal vulcanization type or the addition type.

In the present invention, the rubber hardness of the rubber layer 3 is not particularly limited and can be arbitrarily selected within the range of 4 to 60 degrees.

The compounding recipe of the filler and the like is not particularly limited, and is determined in consideration of the mechanical properties of the cured rubber layer 3, that is, physical strength, rubber hardness, compression set, thermal conductivity and the like. It ’s something like Aerosil or
Examples include fumed silica represented by Cab-O-Sil, wet silica such as Hi-Sil and Nipsil, diatomaceous earth such as Celite and Radiolite, and quartz powder such as Minucil and Crystallite. Are usually used in combination of several types.

In addition to these fillers, aluminum oxide (alumina), titanium oxide, magnesium oxide, aluminum silicate, zinc oxide, iron oxide and carbonic acid are added in order to impart properties such as thermal conductivity and conductivity. You may use calcium, carbon black, etc. together.

Further, in consideration of the sealing aging property, a heat-resistant agent such as cerium oxide or an acid acceptor such as magnesium oxide may be added.

The adhesion between the fluororesin sleeve 4 and the silicone rubber layer 3 can be dealt with by using a silicone-based primer as disclosed in Japanese Patent Publication No. 36-7389.

The metal cored bar 2 and the rubber layer 3 can be adhered to each other by using a silicone-based primer such as Primer No. 16 (manufactured by Shin-Etsu Chemical Co., Ltd.). After activating the surface by sandblasting or the like in advance, a primer is applied.

The fixing roller of the present invention has been described mainly for the pressure roller, but it goes without saying that the heating roller (heat roller) of the fixing roller can be similarly applied.

[0071]

As described above, according to the present invention, it is possible to obtain a fixing roller having extremely excellent adhesion durability of the fluororesin sleeve.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing the structure of a fixing roller according to the present invention.

[Explanation of symbols]

 1 Fixing roller 2 Metal core 3 Rubber layer 4 Fluororesin sleeve

Claims (1)

[Claims] 1. In a fixing roller in which a rubber resin layer coated on the outer periphery of a metal core bar is coated with a fluororesin sleeve having a thickness of 0.1 mm or less, a wetting index of an etching treatment layer inside the fluororesin sleeve is A fixing roller characterized by using a fluororesin sleeve holding 54 or more after a heat resistance test at 150 ° C. for 4 hours.