JP2008076512A - Cleaning blade for image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an elastic cleaning blade having good cleaning property and causing no filming phenomenon even in the case of using a spherical polymerized toner having a smaller particle diameter than a conventional toner. <P>SOLUTION: The cleaning blade for an image forming apparatus comprises a thermosetting polyurethane elastic body and has a Young's modulus of 10-20 MPa, an elongation of 260-350%, a breaking strength of ≥25 MPa and a rebound resilience of ≤20%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cleaning blade for removing residual toner on the surface of a photosensitive member in an electrostatic image forming apparatus such as a plain paper copying machine, a plain paper facsimile machine, and a laser beam printer.

  As an elastic cleaning blade used in the image forming apparatus, a cleaning blade using a polyurethane elastomer is known (for example, Patent Documents 1 and 2).

  Patent Document 1 discloses a cleaning blade made of a polyurethane elastomer containing diphenylmethane diisocyanate (MDI) having a hardness of 64 to 66 as an isocyanate component as a cleaning blade having stable cleaning properties over a wide range of temperature conditions over a long period of time. Has been.

  Patent Document 2 discloses a polyurethane elastomer having a hardness of 75 to 80 as a cleaning blade having stable cleaning properties without causing chipping over a wide range of temperature conditions, and having MDI as an isocyanate component as in Patent Document 1. A cleaning blade is disclosed.

Patent Document 3 discloses that a cleaning blade excellent in durability even under high temperature and high humidity or in an ozone atmosphere is made of a polyurethane elastic body, has a JIS A hardness of 50 to 90, a Young's modulus of 40 to 90 kgf / cm ² , 100% modulus is 20 to 65 kgf / cm ² , 300% modulus is 70 to 150 kgf / cm ² , tensile strength is 240 to 500 kgf / cm ² , elongation is 290 to 500%, impact resilience is 30 to 70%, A cleaning blade having a permanent elongation of 4% or less is disclosed.

JP 2002-236438 A JP 2001-265190 A Japanese Patent No. 3444321

  In an image forming apparatus, image quality is constantly improved, and in recent years, a polymer toner having a spherical shape and a smaller particle diameter has been used to improve the image quality. For this reason, even if a cleaning blade has good cleaning properties when using conventional fine particle toner, cleaning failure or filming phenomenon due to toner slippage occurs when polymerized toner is used, and further improvement is required. It has been.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an elastic cleaning blade that has a good cleaning property and does not cause a filming phenomenon even when a polymer toner having a spherical shape and a smaller particle diameter than that of a conventional one is used.

The cleaning blade for an image forming apparatus of the present invention comprises a thermosetting polyurethane elastic body,
Young's modulus is 10 MPa or more and 20 MPa or less,
Elongation is 260% or more and 350% or less,
Breaking strength is 25 MPa or more,
Rebound resilience is 20% or less,
It is characterized by being.

  When the cleaning blade having such a configuration is used, even in the case where a spherical polymer toner having a smaller particle diameter is used in the image forming apparatus, the cleaning property is good and the occurrence of the filming phenomenon is prevented. .

  When the Young's modulus of the elastic cleaning blade is less than 10 MPa, the force with which the edge of the blade presses against the photosensitive member becomes small and toner slip occurs, and when it exceeds 20 MPa, the edge becomes difficult to bite into the photosensitive member. If it tries to bite into, the rotational torque of the photoreceptor increases. When the elongation of the elastic cleaning blade is less than 260%, edge chipping or filming may occur, and when it exceeds 350%, the cleaning property may be deteriorated. When the breaking strength is less than 25 MPa, edge chipping easily occurs. When the resilience elastic modulus of the elastic cleaning blade exceeds 20%, a stick-slip phenomenon occurs and toner slips easily.

  In the above-mentioned cleaning blade for an image forming apparatus, it is preferable that the polyol component constituting the thermosetting polyurethane elastic body is an adipic acid ester polyol.

  According to such a configuration, it is possible to easily obtain an elastic cleaning blade in which Young's modulus, elongation, breaking strength, and impact resilience satisfy the above-described ranges. The adipic acid type ester polyol means that 85 mol% or more, preferably 90 mol% or more of the dicarboxylic acid component constituting the polyester polyol is adipic acid, and the acid component may be only adipic acid.

  As the polyol component constituting the elastic blade made of polyurethane elastomer for the image forming apparatus of the present invention, a polyol compound for polyurethane elastomer can be used without limitation, and examples thereof include polyether polyol, polyester polyol, and polycarbonate polyol. The Among these, it is preferable to use an adipic ester polyol because an elastic cleaning blade having Young's modulus, elongation, breaking strength, and rebound resilience satisfying the above ranges can be easily obtained.

  As the glycol component constituting the adipic acid ester polyol, known glycols can be used. Specifically, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neo Examples include pentyl glycol and 1,4-cyclohexanedimethanol. These glycols may be used alone or in combination of two or more. Among these, the glycol component constituting the ester polyol is more preferably a glycol having no side chain such as ethylene glycol, 1,4-butanediol, and 1,6-hexanediol.

  Examples of the diisocyanate compound that is a component forming the polyurethane elastic body constituting the cleaning blade of the present invention include 4,4′-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, naphthalene diisocyanate, 4,4 ′. -Aromatic diisocyanate compounds such as phenylene diisocyanate, aliphatic diisocyanate compounds such as ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), hydrogenated 4,4'-diphenylmethane diisocyanate (HMDI), 1,4-cyclohexane diisocyanate (CHDI), methylcyclohexylene diisocyanate, isophorone diisocyanate (IP I), hydrogenated m- xylylene diisocyanate (HXDI), alicyclic diisocyanate compounds such as norbornane diisocyanate can be exemplified. Two or more diisocyanate compounds can also be used in combination. Among these, it is more preferable to use either TDI or MDI.

  A chain extender and a crosslinking agent are used as components for forming the polyurethane elastic body constituting the cleaning blade of the present invention. A bifunctional glycol is preferably used as the chain extender, and a tri- or tetrafunctional polyhydric alcohol is used as the cross-linking agent.

  As a chain extender, the glycol illustrated as a structural component of the said adipic acid ester polyol can be used. Specific examples of the crosslinking agent include aliphatic polyhydric alcohols such as trimethylolpropane, glycerin, and pentaerythritol.

  The Young's modulus, elongation, and breaking strength of the cleaning blade of the present invention are determined by selecting the type of polyol compound, the reaction molar ratio between the polyol compound and (chain extender + crosslinking agent), the reaction molar ratio between the chain extender and the crosslinking agent, etc. This can be achieved by adjusting. The reaction molar ratio of the polyol compound and (chain extender + crosslinking agent) is preferably 0.25 to 0.35, and (isocyanate compound + chain extender + crosslinking agent) is 35-50 wt% of the polyurethane elastic body. %, And more preferably 40 to 50% by weight. The reaction molar ratio of the chain extender / crosslinking agent is preferably 4 to 9, and more preferably 5 to 9.

  As a method of forming a polyurethane elastomer using the above-mentioned polyurethane elastomer raw material, a one-shot method in which a predetermined amount of each component is mixed (mixing step) and the reaction stock solution composition is reacted and cured as a reaction stock solution composition, a polyol component A prepolymer is prepared by previously reacting at least a part with an isocyanate component (prepolymer production step), and the prepolymer, at least a chain extender and a crosslinking agent are mixed (mixing step) to obtain a reaction stock solution composition, There is a prepolymer method for reaction-curing the reaction stock solution composition, and any method may be used. However, since a polyurethane elastomer having more excellent physical properties can be obtained, the prepolymer method is preferable as described above. The NCO / OH equivalent ratio (NCO index) in the curing reaction is preferably 1.05 to 1.30.

  In the prepolymer method, a total amount of a polyol component and an isocyanate component are reacted to form a prepolymer, and a complete prepolymer method in which the prepolymer is reacted with a chain extender and a crosslinking agent. A part of the polyol component and an isocyanate component are combined. There is a pseudo prepolymer method in which a prepolymer is reacted to react with a mixture of the prepolymer, the remaining polyol component, a chain extender, and a crosslinking agent, and any method can be used.

The blade for an image forming apparatus can be manufactured, for example, by a manufacturing method having the following molding process.
<1> Sheet Forming Method 1) The reaction stock solution composition is cast into a sheet shape and reacted and cured to form a raw sheet, and the raw sheet is cut (cutting step) into a blade. In sheet forming, a centrifugal forming method is generally used.
2) A blade is mounted on a base material (metal fitting) for mounting the blade on the image forming apparatus by bonding or the like.
<2> Direct molding method A base material (metal fittings, etc.) for mounting the blade on the image forming apparatus is arranged in the mold having the cavity of the shape of the blade to be molded as required, and reacts to the molding cavity. The stock solution composition is cast to form a blade or blade unit.

<Example of polyurethane elastomer sheet production>
(Example 1)
Pseudo-prepolymer A was produced by heating and reacting 564 g of bifunctional polyethylene adipate having an average molecular weight of 2000 and 436 g of diphenylmethane diisocyanate by a conventional method. A curing agent composition was prepared by mixing 167 g of a bifunctional polyethylene adipate having an average molecular weight of 2000, 92 g of 1,4-butanediol (BD), and 16 g of trimethylolpropane (TMP). A polyurethane elastomer sheet having a thickness of 2 mm was prepared by centrifugal molding. After post-cure and aging, the physical properties were evaluated, and a cleaning blade having a predetermined shape was prepared, and the actual machine was evaluated.

(Example 2)
Pseudo-prepolymer B was prepared by heating and reacting 565 g of bifunctional polyethylene adipate having an average molecular weight of 2000 and 435 g of diphenylmethane diisocyanate by a conventional method. A curing agent composition prepared by mixing 116 g of bifunctional polybutylene adipate with an average molecular weight of 2000, 89 g of 1,4-butanediol and 21 g of trimethylolpropane was prepared, and 1000 g of the pseudo prepolymer B and 226 g of the curing agent composition were mixed. In the same manner as in Example 1, a polyurethane elastomer sheet was prepared and evaluated, and a cleaning blade was prepared and evaluated.

(Comparative Example 1)
A pseudo-prepolymer C was prepared by heating and reacting 590 g of bifunctional poly ε-caprolactone polyol (Placcel 230CP: Daicel Chemical Industries) and 410 g of diphenylmethane diisocyanate by a conventional method. A curing agent composition prepared by mixing 132 g of bifunctional poly ε-caprolactone polyol having an average molecular weight of 2000 (Placcel 220N: Daicel Chemical Industries), 77.1 g of 1,4-butanediol, and 33.3 g of trimethylolpropane was prepared. Prepolymer C (1000 g) and curing agent composition (242.4 g) were mixed, and in the same manner as in Example 1, production and evaluation of a polyurethane elastomer sheet, and production of a cleaning blade and evaluation of an actual machine were performed.

(Comparative Example 2)
A curing agent composition prepared by mixing 188 g of bifunctional poly ε-caprolactone polyol having an average molecular weight of 2000 (Placcel 220N: Daicel Chemical Industries), 77.8 g of 1,4-butanediol, and 30.1 g of trimethylolpropane was prepared. The pseudo prepolymer C produced in Example 1 was mixed with 1000 g of the curing agent composition, and 295.9 g of the curing agent composition was mixed. In the same manner as in Example 1, production and evaluation of a polyurethane elastomer sheet, and production of a cleaning blade and evaluation of an actual machine were performed.

(Comparative Example 3)
Pseudo-prepolymer D was prepared by heating and reacting 571 g of bifunctional polybutylene adipate having an average molecular weight of 2000 and 429 g of diphenylmethane diisocyanate by a conventional method. A curing agent composition was prepared by mixing 175.5 g of bifunctional polybutylene adipate having an average molecular weight of 2000, 98.2 g of 1,4-butanediol (BD), and 16.1 g of trimethylolpropane (TMP). D1000g and the curing agent composition 298.8g were mixed, and a polyurethane elastomer sheet having a thickness of 2 mm was prepared by a centrifugal molding method. After post-cure and aging, the physical properties were evaluated, and a cleaning blade having a predetermined shape was prepared, and the actual machine was evaluated.

<Evaluation>
(Young's modulus, elongation, breaking strength)
It measured based on JISK6251 using the polyurethane elastic body sheet obtained in the manufacture example.

(Rebound resilience)
The rebound resilience at 23 ° C. was measured according to JIS K 6255 (Lupke type).
(hardness)
Hardness measured Shore A hardness using the durometer hardness meter based on JISK6253. The measurement was performed on a sample obtained by overlapping six polyurethane elastic sheets having a thickness of 2.0 mm obtained in the production example to a thickness of 12.0 mm.

(Actual machine evaluation)
The cleaning blade produced in the example and the comparative example is bonded and fixed to a predetermined metal fitting using a hot melt adhesive, and mounted on a commercially available laser beam printer MAGICOLOR 2300DL (Konica Minolta) using polymerized toner, and an image formation test. Went. The 50001th image after printing 5000 test images (5k) and the photoreceptor were visually evaluated.

<Evaluation results>
The evaluation results are shown in the lower part of Table 1. From these results, the evaluation results of the cleaning blade of the present invention were all good, but the cleaning blade of Comparative Example 1 having a small Young's modulus and elongation generated filming, had a small Young's modulus and breaking strength, and had a rebound resilience. The cleaning blade of Comparative Example 2 having an excessively high rate produced filming and edge chipping. Further, the cleaning blade of Comparative Example 3 having an elongation exceeding 350% also caused filming.

Claims (2)

It consists of a thermosetting polyurethane elastic body,
Young's modulus is 10 MPa or more and 20 MPa or less,
Elongation is 260% or more and 350% or less,
Breaking strength is 25 MPa or more,
An image forming apparatus cleaning blade having a rebound resilience of 20% or less.   The cleaning blade for an image forming apparatus according to claim 1, wherein the polyol component constituting the thermosetting polyurethane elastic body is an adipic acid ester polyol.