JP2854229B2 - Cleaning member for electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning member for an electrophotographic photosensitive member used for a copying machine, a printer and the like. More specifically, the present invention relates to a cleaning member for an electrophotographic photosensitive member having excellent elastic recovery and extremely small permanent distortion.

[0002]

2. Description of the Related Art An electrophotographic image recording apparatus using an electrophotographic photosensitive member is used for various purposes such as a copying machine, a laser beam printer, and a facsimile. In such an electrophotographic image recording apparatus, in particular, an image recording apparatus using plain paper as recording paper, an electrostatic latent image formed by exposing an electrophotographic photosensitive member (hereinafter, referred to as a photosensitive member) is formed by toner. And a transferred image is transferred to a recording sheet to form a copied image or the like.

For this reason, in the electrophotographic image recording apparatus, in the final step of one image recording process, the photoconductor is cleaned after transferring the image to the recording paper to remove the residual toner adhering thereto. is necessary.

[0004] Such a photoreceptor cleaning method is such that a cleaning member (a so-called cleaning blade) formed of an elastic body is brought into contact with the photoreceptor and relatively rubs the photoreceptor and the cleaning member. A method of scraping residual toner is known, and has a simple configuration, and is widely used in various image recording apparatuses. As a material for the cleaning member, a urethane elastomer is preferably used because it has better wear resistance than other materials.

[0005]

However, such a cleaning member for an electrophotographic photosensitive member has a thin plate-like shape formed of an elastic body and has a predetermined angle with respect to the photosensitive member. in a state that has been, is placed in pressure contact with the corner portion on the photosensitive member, by the arc both frictionally relatively slides for removing residual toner on the photosensitive member.

[0006] Therefore, in order to perform suitable cleaning, the cleaning member must have an appropriate hardness (JIS A hardness of 6).
(About 0 to 80 degrees). On the other hand, a cleaning member that is constantly pressed against the photoconductor is used for a long period of time, and causes permanent distortion. However, when permanent distortion occurs, the pressing force on the photoconductor is reduced and the cleaning function is reduced. Is also required to have a small permanent set. Further, since the photoreceptor is often disposed near the high-temperature fixing device, it is preferable that the cleaning member that is in pressure contact with the photoreceptor also has excellent corrosion resistance under high temperature and high humidity.

[0007] In general, if the hardness of the obtained formed product is reduced, the permanent set can also be reduced. However, if the cleaning member is made of a material having a too low hardness, the residual toner cannot be removed from the photoreceptor, which is not suitable for use. Also, when the permanent strain of the formed product is reduced, the rebound resilience generally tends to increase. Further, the resilience of the elastic body increases when the temperature becomes high. 7
If it exceeds 5%, unusual noise (so-called squeal) is apt to occur due to friction between the photosensitive member and the cleaning member, which is not preferable.

Various proposals have been made to solve such problems. For example, Japanese Patent Publication No. 1-49409 discloses a diol-based curing agent, a vicinal having both adjacent carbon atoms having a hydroxyl group. A) A cleaning member for an electrophotographic copying machine is disclosed which uses a urethane elastomer obtained by curing a urethane prepolymer by using a diol-based curing agent and a polyfunctional curing agent having three or more functionalities in combination.

However, a cleaning member for an electrophotographic copying machine which satisfactorily satisfies various required characteristics such as moderate hardness, low permanent set, low rebound resilience, and durability under high temperature and high humidity has been realized. Absent.

An object of the present invention is to solve the above-mentioned problems of the prior art, and has an appropriate hardness as a cleaning member for an electrophotographic copying machine, has excellent elastic recovery properties, and has both a compression set and an extension set. An object of the present invention is to provide a cleaning member for an electrophotographic photosensitive member which is extremely small, has low rebound resilience, especially low rebound resilience even at high temperatures, and has good durability under high temperature and high humidity.

[0011]

In order to achieve the above-mentioned object, the present invention provides a polyester polyol having an average molecular weight of 500 to 5000 obtained by ring-opening polymerization of ε-caprolactone using 2,2-dimethylpropanediol as a polymerization initiator. And a polyisocyanate to form a urethane prepolymer, and the prepolymer is a mixture of bifunctional and trifunctional
Provided is a cleaning member for an electrophotographic photosensitive member, wherein a urethane elastomer obtained by curing with riol is used as a material.

Hereinafter, the cleaning member for an electrophotographic photosensitive member of the present invention (hereinafter referred to as a cleaning member) will be described in detail.

The cleaning member of the present invention is a urethane elastomer which uses 2,2-dimethylpropanediol (neopentyl glycol) as a polymerization initiator and uses as a polyester polyol a polycaprolactone ester obtained by ring-opening polymerization of ε-caprolactone. Is the material.

According to the present invention, by using such a polyester polyol for a urethane elastomer, it is possible to obtain appropriate hardness, extremely small permanent set, moderate rebound resilience, durability under high temperature and high humidity, and particularly, elastic recovery. Although the cleaning member excellent in both the compression set and the extension set is extremely small, the obtained polycaprolactone ester is amorphous by using neopentyl glycol as the ring-opening polymerization initiator of ε-caprolactone. It is considered that the urethane elastomer using the polyester polyol as a polyester polyol has excellent elastic recovery and extremely small permanent set.

In the cleaning member of the present invention, the average molecular weight of such a polyester polyol is 500 to 500.
5000. If the average molecular weight is less than 500, the reaction rate is too fast in a curing (crosslinking) reaction in which a polyisocyanate and a curing agent are added later, and the composition is cured before the molding is completely performed to obtain a cleaning member having a predetermined shape. Can not do. Conversely, if the average molecular weight exceeds 5,000, the effect of using neopentyl glycol as a polymerization initiator is dilute, and characteristics such as small permanent distortion cannot be exhibited. Further, when the average molecular weight of the polyester polyol is large, there is also a problem that the viscosity of a prepolymer obtained by mixing a polyisocyanate and a curing agent later is high, and moldability is deteriorated.

Preferably, by setting the average molecular weight of the polyester polyol to about 800 to 3000, favorable results are obtained in terms of elastic recovery, permanent set, and the like.

The method for synthesizing such a polyester polyol (polycaprolactone ester) is not particularly limited, and may be a general method. The quantitative ratio between ε-caprolactone and neopentyl glycol may be set, for example, stoichiometrically.

The cleaning member of the present invention uses, as a material, a urethane elastomer obtained by curing a urethane prepolymer obtained by reacting a polyisocyanate with the polyester polyol. There is no particular limitation on the polyisocyanate used, and various polyisocyanates used in the production of conventional urethane elastomers can be used. Specifically, tolylene diisocyanate, 4,
Examples thereof include 4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, 1,5-naphthalenediisocyanate, and dicyclohexylmethane diisocyanate.

The cleaning member of the present invention mainly manufactured from these raw materials is preferably manufactured by the following method. First, a polyester polyol (polycaprolactone ester) synthesized by a conventional method was used in an amount of 100-1.
After dehydration for 2 to 5 hours at 20 ° C. and 0 to 5 mmHg,
The polyisocyanate is mixed and reacted at a temperature of 50 to 120 ° C for 1 to 4 hours to obtain a urethane prepolymer. Next, a mixture of bifunctional and trifunctional is added to the urethane prepolymer.
Add the curing agent of the compound polyol and mold it into a predetermined shape,
The composition is cured (crosslinked) at a temperature of 100 to 140 ° C. for about 10 to 120 minutes to obtain a urethane elastomer having a desired hardness of about 60 to 80 degrees in JIS A hardness. The obtained urethane elastomer is processed into a predetermined shape to obtain a cleaning member of the present invention.

As the curing agent for the urethane prepolymer, various curing agents for mixed polyols of difunctional and trifunctional can be used. Specifically, 1,4-butanediol, 2,3- Butanediol, 1,1,1-trimethylolpropane, ethylene glycol, hydroquinone-bis (β-hydroxyethyl) ether, 3,3′-
From dichloro-4,4'-diaminodiphenylmethane, etc.
A mixture of bifunctional and trifunctional polyols selected from the group consisting of
Le can be exemplified. Further, the amount ratio of the curing agent to the urethane prepolymer is not particularly limited, but is preferably NCO /
The ratio (OH and / or NH ₂ ) is about 0.8 to 1.3, more preferably about 0.9 to 1.1.

[0021]

Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention. It is needless to say that the present invention is not limited to the following embodiments.

<Experimental Examples> The following three types of urethane elastomers were prepared. [Urethane Elastomer A] Ring opening polymerization of ε-caprolactone using 2,2-dimethylpropanediol (neopentyl glycol) as a polymerization initiator, average molecular weight 20
By reacting 43.3 parts by weight of 4,4'-diphenylmethane diisocyanate with 100 parts by weight of the polyester polyol (polycaprolactone ester) of Example No. 00, a urethane prepolymer having 6.7% of free isocyanate was obtained. To 100 parts by weight of the urethane prepolymer, 6.5 parts by weight of a curing agent (1,4-butanediol / 1,1,1-trimethylolpropane = 60/40 molar ratio) was added (NCO / OH = 0.40). 9) After curing at 140 ° C. for 1 hour, a urethane elastomer A (corresponding to the product of the present invention) was obtained.

[Urethane Elastomer B] 100 parts by weight of a polyester polyol (polycaprolactone ester) having an average molecular weight of 2,000 obtained by ring-opening polymerization of ε-caprolactone using diethylene glycol as a polymerization initiator,
4,4'-diphenylmethane diisocyanate 38.1
By reacting parts by weight, a urethane prepolymer of 6.1% free isocyanate was obtained. A curing agent (1,4-butanediol / 1,1,1-trimethylolpropane = 75 /
5.7 parts by weight (NCO / OH)
= 0.95) and cured at 140 ° C for 1 hour to obtain a urethane elastomer B (corresponding to a conventional product).

[Urethane Elastomer C] Average molecular weight 2
4,4'-diphenylmethane diisocyanate in 100 parts by weight of polyethylene butylene adipate
By reacting 4 parts by weight, a urethane prepolymer of 6.1% free isocyanate was obtained. A curing agent (1,4-butanediol / 1,1,1-trimethylolpropane = 65) was added to 100 parts by weight of the urethane prepolymer.
/ 35 mol ratio) and 6.3 parts by weight (NCO / O
H = 0.95) and cured at 140 ° C. for 1 hour to obtain a urethane elastomer C (corresponding to a conventional product).

For each of the obtained urethane elastomers, according to JIS K6301, JIS A hardness, breaking strength, elongation, 25%, 50% and 100% elongation modulus, tear strength, compression set, and various temperatures Was measured for rebound resilience. The tensile set was measured by measuring the amount of strain after elongating 50% at room temperature and holding for 24 hours. Further, in order to examine the moisture and heat deterioration resistance of each urethane elastomer, the urethane elastomer was subjected to an environment at 70 ° C. and a humidity of 95%.
The 25% elongation modulus after storage for 0 days was measured, and the retention of the 25% elongation modulus before and after the environmental storage was calculated. The results are shown in Table 1 below. FIG. 1 shows the relationship between the temperature and the rebound resilience of each urethane elastomer.

[0026]

[Table 1]

As shown in Table 1, the urethane elastomer A used for the cleaning member of the present invention has an appropriate hardness and a sufficient strength as a cleaning member, and has both a permanent compression set and a permanent tensile set. Is extremely small as compared with urethane elastomers B and C used for the cleaning member. Also, as described above, ordinary elastomers have a higher permanent resilience when the permanent set is reduced,
The rebound resilience tends to increase as the temperature rises. However, if a rebound resilience (especially 75% or more) is used for a cleaning member for a photoconductor, there is a problem that so-called squealing occurs. Here, as shown in FIG. 1, the urethane ethastomer A corresponding to the product of the present invention has a smaller rebound resilience than the urethane ethastomers B and C, which have a large permanent set, though the permanent set is extremely small. In addition, the improvement in rebound resilience against a temperature rise is small. In addition, the urethane ethastomer A corresponding to the product of the present invention is extremely excellent in resistance to moist heat deterioration compared to the urethane ethastomers B and C corresponding to the conventional product. Therefore, the cleaning member of the present invention using such a urethane elastomer exhibits a suitable cleaning function over a long period of time due to an appropriate height, a small compression set, and excellent resistance to heat and moisture deterioration, In addition, it can be seen that it has excellent performance with little problem of squeal and the like.

<Embodiment> A cleaning member was manufactured using the urethane elastomers A, B and C manufactured in the above experimental example, and was attached to a copying machine of 30 sheets / min.
The cleaning property after copying on 00 sheets of plain paper and the abrasion amount at the corners of the cleaning member were measured.

As a result, in the cleaning member of the present invention using the urethane elastomer A, 20,000
Even after copying a sheet of plain paper, good cleaning performance was exhibited, and a good copied image could be obtained. On the other hand, the conventional cleaning member using the urethane elastomer B produces a defective copy image having toner stains after copying 20,000 sheets of plain paper, and the conventional cleaning member using the urethane elastomer C uses 20,000 sheets of plain paper. After copying, only a defective copied image could be obtained.

The abrasion of the corners after copying 20,000 sheets of plain paper was 0 to 5 μm for the cleaning member of the present invention using the urethane elastomer A, which was sufficiently usable thereafter. On the other hand, the conventional cleaning member using the urethane elastomer B has a wear amount of 5 to 5.
The conventional cleaning member using the urethane elastomer C has a thickness of 10 μm, which is 10 to 15 μm, which needs to be replaced immediately after continued use or is difficult to use thereafter. From the above results, the effect of the present invention is clear.

[0031]

As described in detail above, the cleaning member for an electrophotographic photoreceptor of the present invention has an appropriate hardness, is excellent in elastic recovery, and has extremely small compression set and extension set. The rebound resilience, especially at high temperatures, is lower than before, and the durability under high temperature and high humidity is also good. A good cleaning function is stably exhibited over a long period of time. Excellent performance with few problems.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the rebound resilience of urethane elastomer and temperature.

Claims (1)

(57) [Claims] 1. A polyester polyol having an average molecular weight of 500 to 5000 obtained by ring-opening polymerization of ε-caprolactone using 2,2-dimethylpropanediol as a polymerization initiator,
A urethane prepolymer is reacted with a polyisocyanate, and the prepolymer is mixed with a bifunctional and trifunctional mixed polyol.
A cleaning member for an electrophotographic photosensitive member, wherein a urethane elastomer obtained by curing with a tool is used as a material.