JPH10254324A - Cleaning blade for electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning blade for an electrophotographic device which obviates the generation of the local chipping of edges in spite of long-term use. SOLUTION: The blade member of the cleaning blade for the electrophotographic device consisting of the blade member, supplying member and adhesive layer consists of a polyurethane elastomer. This polyurethane elastomer consists of polyester polyol having a number average mol.wt. of 1000 to 5000, polyisocyanate and low-mol.wt. polyol having a mol.wt. of 62 to 250. This polyisocyanate consists of 4,4'-diphenyl methane diisocyanate and 2,4'-diphenyl methane isocyanate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning blade for an electrophotographic apparatus in which chipping of an edge portion is less likely to occur.

[0002]

2. Description of the Related Art An electrophotographic apparatus has a photoconductor provided with a photoconductor layer on a surface thereof. In operation, an outer peripheral surface of the photoconductor is uniformly charged. An electrostatic latent image is formed by exposing the outer peripheral surface of the electrostatic latent image via a copied image, and a toner image is formed by attaching toner to the electrostatic latent image, and the toner image is transferred and fixed on paper or the like. It is.

In this process, since a part of the toner remains on the outer periphery of the photoreceptor after the transfer, it is necessary to remove the residual toner. Removal of such toner is usually
This is performed by a cleaning blade. The cleaning blade is generally formed of a support member made of a metal plate, a blade member made of an elastomer, and an adhesive layer for attaching the blade member to the support member.

[0004] The blade member needs characteristics such as low friction and permanent deformation due to rubbing with the photoreceptor, low pressure during bonding, and low deformation of the adhesive layer by a solvent, and damage to the photoreceptor. And a hardness of 65 to 80 degrees (JIS)
-A) are preferred.

In order to satisfy these characteristics, a blade member cut from a sheet made of polyurethane elastomer to a predetermined size is widely used as a blade member. The polyurethane elastomer is usually added with a curing agent composed of a polyol to a prepolymer obtained by reacting a high molecular weight polyol such as polyethylene adipate ester or polycaprolactone ester with a polyisocyanate such as 4,4'-diphenylmethane diisocyanate. And then poured into a mold and cured.

However, the blade member made of the polyurethane elastomer obtained as described above has a problem that the edge portion which comes into contact with the photoreceptor is liable to be chipped during a long period of use.

JP-A-2-203372 discloses that the number of functional groups comprising a polyisocyanate and a polyol is 2.0.
It is disclosed that a cleaning blade for an electrophotographic apparatus having a blade member using a prepolymer of 2 to 2.5 has high edge part durability.

[0008] JP-A-5-15097 discloses that a prepolymer prepared from a polyisocyanate and a polyol having a molecular weight of 1,000 to 3,000 and having an isocyanate group content of 8 to 20% by weight has a number average molecular weight of 8 to 20% by weight. The polyol having a molecular weight of 1000 to 3000 and a molecular weight of 60
A cleaning agent for an electrophotographic apparatus having a blade member made of a polyurethane elastomer obtained by blending a curing agent consisting of a polyol having a molecular weight of 250 to a hydroxyl group / isocyanate group with an equivalent ratio of 0.8 to 0.9. It is disclosed that the blade hardly causes chipping of an edge portion and has excellent durability.

However, even when these cleaning blades are used, a local defect occurs at the edge of the blade member as the rubbing distance with the photosensitive member increases, and toner is removed from the defective portion. Problems such as slip-through and blurred images occurred, and the durability of the blade member was still insufficient.

Further, as another method for preventing local chipping from occurring at the edge portion of the blade member,
(A) a method of adding a lubricant to the polyurethane elastomer to reduce the coefficient of friction of the blade member, (b) a method of blending the lubricant with the toner, and (c) reducing the pressing force of the blade member on the surface of the photoreceptor. Methods have been proposed.

However, the method (a) and the method (b)
However, there is a problem that the added lubricant may adversely affect the photoreceptor, and the method (C) may cause the toner to slip through between the blade member and the surface of the photoreceptor. There is a problem.

[0012]

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide a cleaning blade for an electrophotographic apparatus in which local chipping of an edge portion hardly occurs even when used for a long time.

[0013]

According to the present invention, there is provided a cleaning blade for an electrophotographic apparatus comprising a blade member, a support member, and an adhesive layer, wherein the blade member comprises a polyurethane elastomer, and the polyurethane elastomer comprises: It comprises a polyester polyol (a) having a number average molecular weight of 1,000 to 5,000, a polyisocyanate (b), and a low molecular weight polyol (c) having a molecular weight of 62 to 250. This is a cleaning blade for an electrophotographic apparatus comprising '-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate. Hereinafter, the present invention will be described in detail.

[0014] The cleaning blade for an electrophotographic apparatus of the present invention comprises a blade member, a support member, and an adhesive layer. The blade member is made of a polyurethane elastomer. The polyurethane elastomer comprises a polyester polyol (a) having a number average molecular weight of 1,000 to 5,000, a polyisocyanate (b), and a low molecular weight polyol (c) having a molecular weight of 62 to 250.

The above polyisocyanate (b) is
4'-diphenylmethane diisocyanate and 2,4 '
-Consisting of diphenylmethane diisocyanate. The 4,4'-diphenylmethane diisocyanate is represented by the following formula (1), and the 2,4'-diphenylmethane diisocyanate is represented by the following formula (2).

[0016]

Embedded image

The above polyisocyanate (b) is
4'-diphenylmethane diisocyanate and 2,4'-
The compounding ratio with diphenylmethane diisocyanate is preferably 99.9: 0.1 to 70:30 by weight. If the amount of 2,4'-diphenylmethane diisocyanate is less than 0.1, the effect of preventing chipping of the edge portion cannot be obtained, and if it exceeds 30, the hardness of the obtained polyurethane elastomer is too low, and the strength is also lowered, resulting in abrasion resistance. The abrasion becomes worse and the life of the blade member is shortened.

The number average molecular weight used in the present invention is 100
The polyester polyol (a) of 0 to 5000 is
When the number average molecular weight is less than 1,000, the hardness of the obtained polyurethane elastomer is increased, and the elongation and flexibility are reduced. When it is more than 5,000, the elongation is increased, and the mechanical strength is reduced. Limited to range. Preferably, it is 1500-4000.

The polyester polyol (a) having a number average molecular weight of 1,000 to 5,000 is not particularly limited. For example, adipate-based polyester polyol which is a condensate of alkylene glycol and adipic acid; ring-opening polymerization of caprolactone The resulting polycaprolactone ester polyol; polycarbonate ester polyol, and the like. Among them, adipate polyester polyols and polycaprolactone ester polyols are preferred.

The adipate-based polyester polyol is not particularly restricted but includes, for example, polyethylene adipate ester polyol, polybutylene adipate ester polyol, polyhexylene adipate ester polyol, polyethylene-propylene adipate ester polyol, polyethylene-butylene adipate ester polyol, polyethylene -Neopentylene adipate ester polyol and the like. These may be used alone or in combination of two or more.

The caprolactone ester polyol is not particularly restricted but includes, for example, ε-caprolactone,
δ-caprolactone, γ-caprolactone, β-caprolactone, α-caprolactone, β-methyl-ε-caprolactone, ε-methyl-ε-caprolactone, α-methyl-ε-caprolactone, etc. obtained by ring-opening addition polymerization. And the like. These may be used alone or in combination of two or more.

The molecular weight used in the present invention is from 62 to 250.
If the molecular weight of the low molecular weight polyol (c) is less than 62, the resulting blade member will be too hard,
If it exceeds 0, the mechanical strength is insufficient, so that it is limited to the above range.

The low molecular weight polyol (c) having a molecular weight of 62 to 250 is not particularly limited.
Polyhydric alcohols, trihydric or higher polyhydric alcohols, amine-containing polyhydric alcohols and the like can be mentioned. These may be used alone or in combination of two or more.

The dihydric alcohol is not particularly restricted but includes, for example, 1,4-butanediol, ethylene glycol, propylene glycol, diethylene glycol,
Triethylene glycol, neopentyl glycol,
1,6-hexanediol, dipropylene glycol,
3-methyl-1,5-pentanediol and the like.

The trihydric or higher polyhydric alcohol is not particularly restricted but includes, for example, 1,1,1-trimethylolpropane, glycerin, 1,2,6-hexanetriol, 1,2,4-butanetriol, Trimethylolethane, 1,1,1-tris (hydroxyethoxymethyl) propane, diglycerin, pentaerythritol and the like. The amine-containing polyhydric alcohol is not particularly limited, and includes, for example, triethanolamine, triisopropanolamine, diisopropanolamine and the like.

In the present invention, in order to impart suitable mechanical strength as a blade member and improve permanent set,
It is preferable to use the dihydric alcohol and the trihydric alcohol in combination. As such a combination, for example,
A dihydric alcohol such as 1,4-butanediol;
Combination with a trihydric alcohol such as 1,1-trimethylolpropane and the like can be mentioned. In this case, the dihydric alcohol and 3
The molar ratio with the dihydric alcohol is preferably 3: 1 to impart suitable mechanical strength and improve permanent set.
It is preferable that the hydric alcohol is 60:40 to 90:10.

The support member used in the present invention is not particularly limited, and may be, for example, a rigid metal, an elastic metal;
Examples thereof include those manufactured from plastics, ceramics, and the like. Usually, untreated steel sheets; those manufactured from steel sheets subjected to surface treatment such as zinc phosphate treatment and chromate treatment, and the like are used. Can be. In the production of the cleaning blade for an electrophotographic apparatus of the present invention, it is preferable that the support member is used after being degreased with a solvent or the like.

The method of manufacturing the cleaning blade for an electrophotographic apparatus of the present invention is performed by a commonly used method. For example, a polyurethane elastomer sheet obtained by centrifugal molding or the like is cut into a predetermined size to obtain a blade member. After that, a commonly used adhesive is applied to the support member, and a blade member is bonded on the support member by heating and pressing, and the support member coated with the adhesive is held in a blade member molding die. Alternatively, a method of injecting a polyurethane producing liquid into the vicinity of the bonding portion and bonding at the same time as the curing reaction can be adopted. In this case, the adhesive used for the bonding is not particularly limited, and examples thereof include a hot melt adhesive. The adhesive used for simultaneous curing and bonding is not particularly limited, and examples thereof include a phenol-based solution adhesive.

The cleaning blade for an electrophotographic apparatus of the present invention uses the above 4,4'-diphenylmethane diisocyanate and the above 2,4'-diphenylmethane diisocyanate together as a polyisocyanate. 4 above
In 4'-diphenylmethane diisocyanate, since the two isocyanate groups are located at symmetric positions, the resulting polyurethane molecule becomes linear, and the regularity is increased. In the above 2,4'-diphenylmethane diisocyanate, two isocyanate groups are located at asymmetrical positions, the resulting polyurethane molecule has a bent structure, and the regularity of the molecule is disturbed. Therefore, a polyurethane elastomer using only 4,4'-diphenylmethane diisocyanate has a high molecular regularity, a structure having a high cohesive force between molecules, is relatively brittle, and is likely to be chipped at an edge portion.

In the present invention, by using the above 4,4'-diphenylmethane diisocyanate and the above 2,4'-diphenylmethane diisocyanate together, the regularity of the molecules is disturbed, the cohesive force between the molecules is low, and the A flexible and supple polyurethane elastomer can be obtained, and when this is used as a blade member, chipping does not easily occur at the edge even after long-term use, and wear is slight and uniform.

The blade member according to the present invention includes other blades such as a developing blade, a charging blade, and a transfer blade that regulate the thickness of the toner layer in order to carry the toner in a thin layer on the outer periphery of the developing roll in an electrophotographic apparatus or the like. Can also be applied.

[0032]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Examples 1-4 and Comparative Examples 1-3 Prepolymers were synthesized with the composition shown in Table 1. In the synthesis of the prepolymer, polyethylene adipate is
After dehydration under reduced pressure at 3 ° C. × 3 mmHg × 3 hours, a predetermined polyisocyanate was weighed and added, and the mixture was heated at 70 ° C.
C. for 3.5 hours. Table 1 shows the content of isocyanate groups in the obtained prepolymer.

The obtained prepolymer was heated at 60 ° C. × 3 mmH
Degassed under reduced pressure for 1 g × 1 hour. Next, polyethylene adipate, 1,4-butanediol and 1,1,1
A curing agent consisting of trimethylolpropane at 60 ° C. × 3
After degassing under reduced pressure for 1 mmHg × 1 hour, the mixture was mixed at a ratio of [the number of moles of isocyanate groups of the prepolymer] / [the number of moles of hydroxyl groups in the curing agent] = 1.10, and rotated at 400 rpm heated to 150 ° C. Into a centrifugal forming drum.
Thereafter, the speed was immediately increased to 1000 rpm, and the mixture was cured for 50 minutes. After that, take out the molded cylindrical sheet,
After cutting to ２, it was post-crosslinked in an oven at 120 ° C. for 12 hours, and left for 7 days to form a material sheet for a blade member.

The obtained material sheet for a blade member was washed with isopropyl alcohol and then cut to a predetermined size to obtain a blade member. In addition, OD-X-102 (hydroxyl value = 56.1, number average molecular weight 2000) manufactured by Dainippon Ink and Chemicals, Inc. was used as polyethylene adipate.

(1) Hardness The hardness of the obtained blade member was measured by a JIS-A spring hardness meter, and is shown in Table 1.

(2) Durability The durability of the blade member was evaluated by the following method and is shown in Table 1. Attach a cleaning blade to a P-5400 printer manufactured by Matsushita Electric Industrial Co., Ltd.
, Continuous printing was performed until a cleaning failure (black streaks appeared on the paper surface) occurred. The printing was performed in an A4 size, normal temperature and normal humidity, black and white 6% character chart as an image to be copied in a five-sheet intermittent mode (repeating the engine stop after copying five sheets).

(3) Observation of Edge The edge of the cleaning blade was observed by the following method. When cleaning failure occurs,
The printing was stopped, the blade was removed from the printer, and a scanning electron microscope S-800 manufactured by Hitachi, Ltd. was used for 2000.
The state of the edge portion was observed at × 2.

[0039]

[Table 1]

[0040]

As described above, the cleaning blade for an electrophotographic apparatus according to the present invention is as described above, so that even when used for a long period of time, local chipping of the edge portion hardly occurs, and the wear is slight and uniform.

[Brief description of the drawings]

FIG. 1 is a view showing an example of a cleaning blade manufactured by laminating and bonding.

[Explanation of symbols]

 Reference Signs List 1 blade member 2 adhesive layer 3 support member

Continued on the front page (72) Inventor Tsutomu Toshige 3-13-26 Kuguchi, Amagasaki City Sumitomo Bayer Urethane Co., Ltd.

Claims (2)

[Claims] 1. A cleaning blade for an electrophotographic apparatus comprising a blade member, a support member, and an adhesive layer, wherein the blade member is made of a polyurethane elastomer, and the polyurethane elastomer has a number average molecular weight of 1,000 to 5,000. Certain polyester polyol (a), polyisocyanate (b), and having a molecular weight of 6
Consisting of a low molecular weight polyol (c) of 2-250,
A cleaning blade for an electrophotographic apparatus, wherein the polyisocyanate (b) comprises 4,4'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate. 2. The polyisocyanate (b) is 4,4 ′
The cleaning blade for an electrophotographic apparatus according to claim 1, wherein the compounding ratio of -diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate is 99.9: 0.1 to 70:30 by weight.