JPH10196639A - Semi-conductive roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semi-conductive roll which stably obtains electric capacitance even when it is used under severe conditions such as high temperature, high moisture, or low temperature low moisture for a long time, and also obtains stable image without polluting a photosensitive body. SOLUTION: A semi-conductive roll has a polyurethane elastic layer formed on a surface of a core member. The polyurethane elastic layer is made of polyurethane resin obtained by adding, in reacting polyol with polyisocyanate, 4-ammonium perchlorate indicated by the following formula. In the formula, at least one of R1 to R4 includes ethylene glycol radical having end alcohol group, others denote alkyl radical having different number of carbons.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductive roll for controlling electrically non-contact objects such as a charging roll, a transfer roll, a toner transport roll and a cleaning roll in an electrophotographic or electrostatic printer.

[0002]

2. Description of the Related Art With regard to the material properties of these semiconductive rolls, stability of electric resistance and appropriate hardness are particularly important. If the transfer roller does not maintain an appropriate electric resistance value from high temperature and high humidity to low temperature and low humidity, the charging or transfer efficiency is deteriorated, the density is reduced, and an image having a lot of fog is formed.

[0003] In a semiconductive roll, a conductive rubber such as a rubber material containing conductive particles such as carbon black, semiconductive particles or a metal oxide is used. As a method of controlling the electrical characteristics, a method of changing the blending amount of the conductive particles and the like are known, but it is difficult to balance the resistance because the hardness and the resistance conflict as the blending amount increases. For this reason, in order to obtain a good nip property, a large amount of a softener, a plasticizer, and the like must be blended,
When the semiconductive roll is stored for a long period of time, the softener migrates to the surface of the semiconductive roll, and image quality is likely to deteriorate.

In the case of an electron-conductive semiconductive roll in which carbon black is dispersed, it is difficult to control the medium resistance in the range of 10 ⁵ Ω to 10 ⁸ Ω, and the variation due to the measurement position of the electrical resistance and the variation between the rolls. It is difficult to obtain a stable image because the resistance is large and the resistance to the applied voltage is large.

[0005] Semiconductive rolls using various alkali metals, antistatic agents or conductive agents such as highly dielectric liquids to impart ionic conductivity have been studied. Not only the electrical resistance due to the environment is unstable, but also there are problems such as white streaks and black streaks due to surface contamination due to bleeding of the conductive agent and the electrical resistance gradually changes with time. It is difficult to maintain electrical characteristics.

Quaternary ammonium perchloric acid or lithium perchlorate such as tetrabutylammonium salt, trimethyloctadecylammonium salt and benzyltrimethylammonium salt as an ion conductive agent, potassium perchlorate, calcium perchlorate, sodium perchlorate With an alkali metal salt such as, a predetermined electrical resistance can be obtained by adjusting the blending amount,
In addition, although electrostatic coordination to a specific portion of the polymer such as a polyether chain is possible, its electric resistance is likely to rise for a while when voltage is continuously applied, and the charging roll, the transfer roll, the cleaning roll, etc. In the case of adapting to, the predetermined resistance value cannot be maintained, which leads to deterioration of image quality performance.

A conductive elastic roll formed of a polymer having a quaternary ammonium salt structure in a side chain has also been proposed (JP-A-4-119364). However, in the case of this conductive elastic roll, the acrylic polymer, the methacrylic group, and the styryl group-introduced vinyl polymer type have low compatibility with the urethane resin, and the polymer blend alone tends to cause sticking to the photoreceptor and image defects. Furthermore, since the backbone polymer is a polymer, it is difficult to obtain a desired resistance unless a large amount of ions are added.

[0008]

SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide a stable electric resistance even when used for a long period of time in a severe environment such as high temperature and high humidity to low temperature and low humidity. To provide a semiconductive roll whose electric resistance range can be adjusted. A second object of the present invention is to provide a semiconductive roll capable of eliminating a bleeding phenomenon of a conductive agent and providing a stable image without contaminating a photoreceptor even under high temperature and high humidity.

[0009]

A semiconductive roll according to the present invention is a semiconductive roll in which a polyurethane elastic layer is formed on a core material surface, wherein the polyurethane elastic layer is
When reacting polyol and polyisocyanate,
These have the general formula (1)

[0010]

Embedded image (In the formula, at least one of R ^{1 to} R ⁴ contains an ethylene glycol group having a terminal alcohol residue, and the others represent alkyl groups having different carbon numbers from each other.)
It comprises a polyurethane resin obtained by adding a grade ammonium perchlorate.

In the semiconductive roll of the present invention, the quaternary ammonium perchlorate represented by the general formula (1) is incorporated into the polyurethane resin by a polymer reaction, so that stable resistance can be maintained. Maintained for a long time. The quaternary ammonium perchlorate represented by the general formula (1)
Since it contains an ethylene glycol group, it has good compatibility with polyol, no resistance unevenness, and excellent production stability.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below.

In the present invention, the polyurethane elastic material used for the foamed elastic material layer made of polyurethane is composed of a known material prepared from a polyol and a polyisocyanate. Specific examples of polyols include polyether polyols, polyethylene glycol, polypropylene glycol, and copolymers or blends thereof, polyalkylene glycol, polytetramethylene ether glycol, copolymer polyols of tetrahydrofuran and alkylene oxide, and modifications thereof. Body or blended products.

The polyisocyanate used in the present invention is generally used triene diisocyanate (TDI), diphenylmethane diisocyanate (MD
I), hydrogenated MDI, xylylene diisocyanate (XD
I), tetramethyl xylene diisocyanate (TMX
DI), hexamethylene diisocyanate (HDI),
Isophorone diisocyanate (IPDI) or the like can be used. Other commonly used compounding agents include chain extenders, crosslinking agents,
Examples include low molecular polyols such as pigments and flame retardants, and amines and tin complexes as catalysts.

The quaternary ammonium perchlorate used in the present invention is represented by the above general formula (1), but is particularly preferably, for example, a quaternary ammonium perchlorate represented by the following general formula (2). Perchlorate.

Embedded image (Wherein, R ⁵ and R ⁶ each have 1 to 1 carbon atoms having different carbon numbers)
Represents 20 alkyl groups, and x + y = 2 to 15. )

In the present invention, the quaternary ammonium perchlorate is added to the polyurethane resin in an amount of 0.005% by weight to 30% by weight, more preferably 0.1% to 5% by weight. When the addition amount of the quaternary ammonium perchlorate is less than 0.005% by weight, the electric resistance of the semiconductive roll becomes 10 ¹⁰ Ω or more, and the transfer characteristics become poor. Also,
When the amount of the quaternary ammonium perchlorate exceeds 30% by weight, the reactivity of the urethane resin itself decreases, causing image deterioration, and the stability of the cell shape also decreases when foamed.

The quaternary ammonium ring chlorate used in the present invention contains an ethylene glycol group as compared with a normal quaternary ammonium salt having an alkyl group or an aryl group. And the mixing and stirring are easy to be uniform, the dispersibility is uniform, the resistance is not uneven, and the production stability is excellent, the bleeding property after production is small, and the resistance maintenance stability is excellent. In addition, since it has a reactive hydroxyl group at the terminal, it can be incorporated into the polyurethane resin by a polymer reaction and can maintain stable resistance for a long time.

In the present invention, in the reaction between the polyisocyanate and the polyol, the crosslinking reaction between the urethane molecular chains proceeds by adjusting the amount of the polyol to be excessive, so that the dissociation reaction of the quaternary ammonium perchlorate ion is promoted. Suppression becomes possible, and environmental fluctuation of the resistance value is reduced.

On the other hand, the ratio of NCO / OH is 0.95
1.11 is preferable, and more preferably 0.97 to 1.0
6. If this NCO / OH ratio is too small, 4
N which reacts with the terminal hydroxyl group of quaternary ammonium ring chlorate
Since the amount of CO is relatively small, the amount of free quaternary ammonium perchlorate is increased, so that ion transfer is likely to occur as a whole, and environmental fluctuations are increased.

When the ratio of NCO / OH is less than 0.95 or more than 1.11, the molecular weight of the polyurethane itself is reduced to cause poor curing, and the reaction speed rapidly progresses, so that molding in the mold is difficult. The unreacted urethane monomer and the ions themselves are likely to be precipitated, causing problems such as surface contamination.

In the urethane foam roll of the present invention,
Using silicone and a polyether polyol or a silicone side chain type multi-component copolymer prepared from polyesters as a foam stabilizer, the polyol, polyisocyanate, and quaternary ammonium perchlorine represented by the general formula (1) are used. A method of foaming a mixture obtained by adding and mixing an acid salt with a mechanical foaming method in which a gas such as air or nitrogen is mixed or a water foaming method is preferable.

In mixing this mixture, (NCO) /
The (OH) ratio is adjusted in the range of 0.95 to 1.11 in consideration of the OH value of the quaternary ammonium perchlorate, and is preferably adjusted in the range of 0.97 to 1.06, and is commonly used. A compounding agent can be added. It is desirable to produce a sponge roll using the mixture by a known method such as a one-shot casting method or a prepolymer method.

In the ionic conductor, the environmental fluctuation of the resistance value due to the change in temperature and humidity is large, and the change in electric resistance from low temperature and low humidity to high temperature and high humidity is more than two orders of magnitude. It is difficult to reduce environmental fluctuations by controlling only ionic species.
It is necessary to suppress the ease of movement at the time of voltage application by controlling the degree of crosslinking, molecular weight, etc. of the urethane resin itself and the concentration of ions.

For this reason, it becomes possible to control environmental fluctuations to some extent by incorporating ions into the polyurethane by a polymer reaction and controlling the easiness of charge transfer.
It is possible to reduce the state change of the electric resistance to about 2.2 to 1.4 digits.

The semiconductive polyurethane resin of the present invention can be used in the form of a hard resin or rubber, in addition to the use as a hard or soft foam. At this time, water cross-linking in the urethane resin is also progressing by using the water foaming method in combination, and by controlling the amount of addition, the environmental fluctuation of the electric resistance can be controlled to some extent. It can be reduced to 0.3 digits.

The semiconductive roll of the present invention, particularly the charging roll, can be manufactured as follows. A conductive adhesive is applied to the surface of the cored bar, and a semiconductive elastic layer is formed by using the above rubber composition and mold vulcanization. Next, N
-Mixed methylated nylon, carbon black, a mixed resin liquid prepared by mixing a tin oxide and a conductive agent, the surface of the elastic body layer is polished if necessary, sprayed thereon, such as dipping The coating is dried and, if necessary, is crosslinked by heat treatment to form a conductive resistance layer. The semiconductive roll thus obtained has a resistance of 10 ⁵ to 10 ⁹ Ω and can be applied as a charging member for electrophotography or a transfer member.

FIG. 1 is a sectional view showing a preferred embodiment of the semiconductive roll of the present invention. The semiconductive roll 1 is provided with a foamable elastic layer 12 on the outer periphery of a conductive metal core material 11 made of stainless steel (SUS) or iron plated with nickel.
Is configured. The foamed elastic layer 12 has a structure in which a conductive substance such as conductive carbon black is dispersed in a polyurethane polymer substance. A resistance layer 13 is formed on the outer peripheral surface of the foam elastic layer 12.
The semiconductive roll 1 is configured to apply a potential of a predetermined polarity to the photosensitive drum 2.

Next, FIG. 2 shows a preferred embodiment of an image forming apparatus in which the semiconductive roll of the present invention is applied to a transfer roll. This image forming apparatus is configured as a laser printer using an electrophotographic process.
In FIG. 2, reference numeral 21 denotes a photosensitive drum using an organic photosensitive member (OPC) as an image carrier. The photosensitive drum 21 is driven by a driving unit (not shown)
It is driven to rotate at a predetermined process speed in the direction of the arrow. The surface of the photosensitive drum 21 is primarily charged to a predetermined potential by a charging roll 22 that comes into contact with the surface of the photosensitive drum 21.

The charging roll 22 has, for example, a power source 2
3, DC component of voltage -350V and frequency of 350H
An oscillating voltage on which a sine wave AC component having a z voltage of 2000 Vpp is superimposed is applied, and the surface of the photosensitive drum 21 is uniformly charged by the charging roll 22 to -350 V which is equal to the DC component of the applied voltage. Thereafter, the surface of the photosensitive drum 21 is subjected to image exposure (not shown) output according to the image information from the laser writing device 29 to form an electrostatic latent image according to the image information.

Next, the electrostatic latent image formed on the photosensitive drum 21 is developed by a developing roll 25 of a developing device 24 using a magnetic one-component developer or the like to form a toner image.
This toner image is transferred by transfer roller 30 onto transfer paper 26 as a transfer medium fed at a predetermined timing. A current controlled to a constant current of 3 to 5 μA as a transfer current is supplied to the transfer roll 30. Thereafter, the transfer paper 26 onto which the toner image has been transferred is separated from the surface of the photosensitive drum 21 and is conveyed to a fixing device 31, where the toner image is fixed to the transfer paper 26 by heat and / or pressure. Then, the image is discharged outside the apparatus, and the image forming process is completed.

After the toner image transfer process is completed, the surface of the photosensitive drum 21 is cleaned by a cleaning blade 28 of a cleaning device 27 to remove residual toner and the like.
It is prepared for the next image forming step.

[0032]

The present invention will be described below with reference to examples. Unless otherwise specified, [parts] means [parts by weight].

Example 1 Glycerin having a molecular weight of 5000 to which propylene oxide and ethylene oxide were added
Polyether Pole (Asahi Glass Exercise 82)
8) 100 parts, 25 parts of urethane modified MDI (Sumitomo Bayer Sumidur PF), 1,4 butanediol 2.5
Parts, the NCO / OH ratio was adjusted to 1.05, 1.5 parts of a silicone foam stabilizer (L520 manufactured by Nippon Yunika), 0.5 parts of nickel acetyl acetate, 0.0 parts of dibutyltin laurate
One part used 0.05 parts of coconut oil-modified quaternary ammonium salt (C-901 manufactured by Nippon Carlit Co., Ltd.). The structural formula of the coconut oil-modified quaternary ammonium salt (C-901 manufactured by Nippon Carlit Co., Ltd.) is an ethylene glycol-modified perchlorate as shown below.

[0034]

Embedded image (Where COCO is a coconut oil component and has 8 or more carbon atoms)
18 alkyl groups, x + y: 15)

The mixture was stirred and nitrogen gas was bubbled therein. The mixture was poured into a cylindrical mold having a length of 200 mm, a height of 30 mm and a depth of 30 mm, and was heated and cured at 160 ° C. for 30 minutes to obtain a polyurethane roll. The polyurethane foam roll obtained in this way is applied with DC 1000 V and 1 kg
When the load was applied to the roller shaft, the nip resistance was 5 × 10 ⁸ Ω at 10 ° C. and 15 RH%. The hardness of the foam was 33 degrees (Asker C). When a continuous voltage was applied to the roll as it was, the resistance change after 24 hours was 0.2 digits. The semiconductive roll is heated at 40 ° C. for 8
After being kept in contact with the organic photoreceptor under an atmosphere of 5 RH% for 2 weeks under pressure, the image was measured with a laser printer, and no image quality deterioration was observed.

[Example 2] Coconut oil-modified quaternary ammonium salt (Nippon Carlit C-C) was added to 100 parts of a polyester polyol (Kuraray P-2010, Kuraray).
C902) [The structure used in Example 1 and consisting of the structural formula of x + y = 2] 2 parts were added and dissolved by stirring, and then the temperature was adjusted to 100 ° C., and then Coronate HX (manufactured by Nippon Polyurethane Co., Ltd.)
42 parts were added and stirred to obtain a mixture. This mixture is poured into a 30 mm cylindrical mold in which a shaft (8 mm diameter, 270 mm length) is previously placed, and heated at 120 ° C. for 60 minutes to form a semiconductive urethane elastic roll on the shaft surface excluding both ends. did. The roll hardness is 42 degrees (JIS
A), and the roll resistance was measured by the same method as in Example 1 and found to be 2 × 10 ⁷ Ω. Further, as in the case of the first embodiment, the increase in resistance when a continuous voltage was applied was 0.3 digits.

Comparative Example 1 The coconut oil-modified quaternary ammonium salt of Example 1 (C-Nippon Carlit Co., Ltd.)
A urethane foam roll was produced in the same manner as in Example 1 except that tetrabutylammonium perchlorate was used instead of 901). The electric resistance of this roll is 8 × 1
Resistance variation after 0 was ⁸ Omega but continuous voltage application was 1.1 orders of magnitude. High temperature and high humidity (28 ° C, 85%) and low temperature and low humidity (1
(0 ° C., 15%), the environmental fluctuation of the resistance value was 2.3 digits, and an end fogging phenomenon was observed as a transfer roll characteristic at high temperature and high humidity. When the image was measured after storage in the same manner as in Example 1, black streaks occurred at the photoconductor nip.

Comparative Example 2 The coconut oil-modified quaternary ammonium salt of Example 2 (C-C90 manufactured by Nippon Carlit)
A semiconductive roll was formed in the same manner as in Example 2 except that 0.05 parts of lithium perchlorate was added instead of 2). The roll hardness was 40 degrees. Resistance value is 6 × 1
0 ⁷ Ω. In the same manner as in Example 2, the resistance rise in the case of continuous application was 1.3 digits, and the image quality of the actual roll was measured. As a result, a fogging phenomenon due to poor charging was observed for the charging roll.

Example 3 100 parts of N-methoxymethylated nylon (CM-8000, manufactured by Toray) and Ketjen Black EC60 were added to the semiconductive roll prepared in Example 2.
0JD 15 parts (manufactured by Lion Akzo) are dissolved in a solvent of methyl ethyl ketone / methyl isobutyl ketone = 3/1 (weight ratio), the viscosity is adjusted to 500 centipoise, dip coated, dried at 130 ° C. for 30 minutes, and subjected to surface resistance. A charging roll having a layer was prepared. The thickness of the surface resistance layer is 15 μm and the electric resistance of the roller is 7 × 10
⁵ Ω and hardness was 45 degrees (Asker A). When the image quality of the actual machine was measured using this charging roll, good image quality without fogging was obtained.

[0040]

According to the present invention, it is possible to reduce the dependence of the electrical resistance on the electrical characteristics due to the environmental resistance of the urethane resin semi-conductive roll using a specific quaternary ammonium salt as compared with the conventional ionic conductive roll. And a roll capable of controlling the resistance variation width of about 2.3 digits to about 1.3 digits.
It is possible to control the electric resistance widely, and it is possible to provide a semiconductive roll of 10 ⁵ to 10 ⁹ Ω without laminating a large number of resistive layers having a function of separating an appropriate electric resistance, and to produce a copied image such as fog development. Absent. Lithium perchlorate and quaternary ammonium salts having an alkyl or aryl group are only electrostatically coordinated to the crosslinked structure, and dissociation is promoted by the influence of moisture absorbed in the roll, and is moved. Although the resistance cycle up phenomenon occurs due to continuous use, the ionic conductive agent itself has a reactive group of the urethane resin, so that it is incorporated into the urethane molecular chain by a polymer reaction, and it does not bleed out to the surface for a long time. Maintaining a stable electric resistance is also possible by continuous use. The dissociation phenomenon of the conductive agent is also eliminated, and the contamination of the photoreceptor surface can be avoided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a preferred embodiment of a semiconductive roll of the present invention.

FIG. 2 is a schematic configuration diagram showing an embodiment of an image forming apparatus in which the semiconductive roll of the present invention is applied to a transfer roll.

DESCRIPTION OF SYMBOLS 1 Charge roll 2 Photoconductor drum 11 Conductive metal core material 12 Conductive elastic layer 13 Resistive layer 21 Photoconductor drum 22 Charging roll 23 Power supply 24 Developing device 25 Developing roll 26 Transfer paper 27 Cleaning device 28 Cleaning Blade 29 laser writing device

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B29K 75:00

Claims (3)

[Claims] In a semiconductive roll having a polyurethane elastic layer formed on the surface of a core material, when the polyurethane elastic layer reacts a polyol with a polyisocyanate, the polyurethane elastic layer reacts with a general formula (1). ] (In the formula, at least one of R ^{1 to} R ⁴ contains an ethylene glycol group having a terminal alcohol residue, and the others represent alkyl groups having different carbon numbers from each other.)
A semiconductive roll comprising a polyurethane resin obtained by adding a quaternary ammonium perchlorate. 2. The quaternary ammonium perchlorate is represented by the following general formula (2): (Wherein, R ⁵ and R ⁶ each have 1 to 1 carbon atoms having different carbon numbers)
Represents 20 alkyl groups, and x + y = 2 to 15. )
The semiconductive roll according to claim 1, wherein 3. A mixture comprising a polyurethane resin having a hydroxyl value / isocyanate ratio of 0.95 to 1.11 in a formulation containing a hydroxyl value contained in the general formula (1) and controlling the mixing ratio of a polyol and an isocyanate. The semiconductive roll according to claim 1, wherein the semiconductive roll is a roll.