JP2008139743A - Cleaning blade - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning blade having good cleaning performance even to spherical toner. <P>SOLUTION: The cleaning blade is disposed in an image forming apparatus using an electrostatic transfer process so as to remove residual toner on a photosensitive drum loaded in the image forming apparatus by rubbing, and has a blade member comprising a polyurethane elastomer, wherein the polyurethane elastomer satisfies (1) a 100% modulus in a tensile test of 3.0-5.0 MPa, (2) a breaking extension in the tensile test of ≤300%, (3) a hardness (IRHD) of 65-75° and (4) a peak temperature of tanδ in a dynamic viscoelasticity test of ≤0°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cleaning blade used in an image forming apparatus using an electrostatic transfer process such as an electrophotographic copying machine, a laser beam printer, and a facsimile machine.

  Electrophotographic copying machines and laser beam printers perform copying and printing by attaching toner onto an electrostatic latent image formed on a photosensitive drum and transferring the toner onto copying paper. As one of methods for removing residual toner remaining on the photosensitive drum after the transfer, a system using a blade member made of urethane elastomer and a cleaning blade made of a support fitting (holder) has been put into practical use.

  Conventionally, as a material used for the blade member, a polyester urethane elastomer having excellent mechanical strength such as wear resistance and low creep property (permanent deformation due to contact stress), particularly a thermosetting urethane elastomer is used. Has been used.

  The urethane elastomer is produced by a prepolymer method, a semi one-shot method, a one-shot method or the like using a polyisocyanate, a polyol, a chain extender and a catalyst.

  For example, when manufacturing a cleaning blade by the prepolymer method, a prepolymer is prepared using a polyisocyanate and a polyol, a chain extender and a catalyst are added to the prepolymer, and this is then injected into a molding die. And cured.

  In order to completely remove the residual toner on the photosensitive drum by the cleaning blade, it is necessary that the contact of the blade member on the outer peripheral surface of the photosensitive drum is always kept constant. For this reason, methods are generally used in which the positional relationship between the cleaning blade and the photosensitive drum is restricted, or the support fitting is pressed with a spring. However, in recent years, with the improvement in image quality of electrophotographic copying machines and laser beam printers, spherical toner having a smaller particle size than the conventional one has come to be used. As a result, the toner is more likely to slip between the photosensitive drum and the blade member as compared with the conventional case, and cleaning failure is likely to occur. In addition, poor cleaning tends to be further deteriorated in a low temperature environment (0 ° C.) due to a decrease in the rubber property of the urethane elastomer used for the blade member. With the spread of electrophotographic copying machines and laser beam printers, they are used in various environments.

  In view of this, as a measure for preventing the defective cleaning with respect to the spherical toner, for example, the linear pressure of the blade edge portion on the surface of the photosensitive drum can be raised. However, the countermeasures based on the mere increase in the linear pressure have technical problems such as the abrasion of the blade edge or the abrasion of the drum due to the contact of the blade, or the generation of abnormal noise due to the chatter vibration of the blade.

In addition, a method (for example, Patent Documents 1 and 2) in which spherical toner and irregular toner are mixed and used at a specific ratio has been proposed. However, even in such a method, since the spherical toner may pass through the gaps of the irregular toner and may pass through the blade edge portion, the cleaning failure for the spherical toner is not sufficiently improved.
JP 08-62893 A Japanese Patent Laid-Open No. 08-95286

  An object of the present invention is to provide a cleaning blade that has good cleaning performance even for spherical toner.

The present invention that solves the above-described problems comprises a polyurethane elastomer that is disposed in an image forming apparatus using an electrostatic transfer process, and that removes residual toner on a photosensitive drum included in the image forming apparatus by rubbing. In the cleaning blade having a blade member, the polyurethane elastomer satisfies the following (1) to (4).
(1) 100% modulus in tensile test is 3.0 MPa or more and 5.0 MPa or less (2) Elongation at break in tensile test is 300% or less (3) Hardness is 65 ° or more and 75 ° or less (IRHD)
(4) The peak temperature of tan δ in the dynamic viscoelasticity test is 0 ° C. or lower In other words, the present inventors conducted various studies in order to obtain a cleaning blade having good cleaning performance even for spherical toner. In the process, it has been found that 100% modulus, elongation at break, hardness, and tan δ peak temperature in the tensile test are important indexes as indicators of cleaning performance for spherical toner. And it discovered that an intended purpose could be achieved by setting these appropriately, and reached the present invention.

  When the 100% modulus at the time of the tensile test is less than 3.0 MPa, the linear pressure at the blade edge applied to the surface of the photosensitive drum is insufficient, the toner is likely to slip through, and cleaning failure is likely to occur, and the blade edge is deformed. Since it becomes easy to do, it becomes easy to produce a chip. When the pressure exceeds 5.0 MPa, the linear pressure of the blade edge applied to the surface of the photosensitive drum is increased, and wear of the blade edge or the surface of the photosensitive drum is likely to occur. Further, when the elongation at break in the tensile test exceeds 300%, when the blade edge is chipped due to rubbing against the photosensitive drum, the chip is likely to be large, which causes a cleaning failure.

  When the hardness is less than 65 ° (IRHD), the blade edge is soft and the toner tends to slip through. When the hardness exceeds 75 ° (IRHD), the blade edge becomes too hard and the photosensitive drum wears quickly.

  When the tan δ peak temperature in the dynamic viscoelasticity test is higher than 0 ° C, the rubber property of the urethane elastomer is reduced in a low temperature (0 to 10 ° C) environment and cannot be uniformly contacted with the drum. Defects are likely to occur.

The polyurethane elastomer contains the following materials (A) to (E), and the concentration of (A) polyisocyanate calculated by the following formula (I) is 1.00 mmol / g or more and 1.15 mmol. / G or less.
(A) Polyisocyanate (B) Polyol having a number average molecular weight of 2000 or more and 4000 or less (C) Chain extender having a molecular weight of 200 or less (D) Polyol (E) for curing a polyol (E) having a number average molecular weight of more than 200 and less than 2000 Catalyst (A) Concentration of polyisocyanate (mmol / g)
= W _iso / (Mn _iso × W _all ) × 1000 (I)
(In the formula (I), W _iso is the charged amount of (A) polyisocyanate (g), Mn _iso is the number average molecular weight of (A) polyisocyanate, and W _all is the material of (A) to (E). Represents total mass (g)).

  When manufacturing a blade member, the raw material for urethane elastomer adjusted and mixed to a predetermined amount is poured into a molding die and cured. Here, the time from the injection to the mold until the curing / demolding, that is, the curing time greatly affects the production efficiency. If the curing time is long, the number of molds must be increased, and enormous investment is required. For this reason, various studies have been made to shorten the curing time.

  Therefore, in order to shorten the curing time, it is possible to increase the amount of urethane curing catalyst. However, when the raw material for urethane elastomer is not distributed in the mold, or when a polyol having a number average molecular weight of 2000 to 4000 and a chain extender having a molecular weight of 200 or less are used in combination, the reaction is caused because the molecular weight is greatly different. It tends to be uneven. As a result, there has been a problem that a surface pattern resulting from distortion of the molded product and unevenness of shrinkage occurs. Therefore, by using the polyurethane raw material composition containing the above (A) to (E), the flowability to the mold is good and the surface pattern due to shrinkage unevenness does not occur, so that the production efficiency can be increased. . Here, by using at least two kinds of polyester polyols constituting the polyurethane elastomer, the crystallinity of the soft segment of the polyurethane elastomer can be lowered, and the peak temperature of tan δ can be lowered.

  In addition, when the concentration of (A) polyisocyanate is less than 1.00 mmol / g, the amount of hard segments in the polyurethane elastomer is reduced and softened, so the above conditions (1) to (4) may not be satisfied. . On the other hand, when the polyisocyanate concentration exceeds (A) 1.30 mmol / g, the amount of hard segments in the polyurethane elastomer becomes too large and hard, so that the physical properties of the above conditions (1) to (4) are not satisfied. There is.

  According to the present invention, it is possible to obtain a cleaning blade having good cleaning performance even for spherical toner.

  In the cleaning blade of the present invention, a liquid composition containing a polyisocyanate, a polyol, a chain extender, and a urethane curing catalyst is injected into a mold for cleaning blade on which a support member is disposed, cured, and after demolding, a predetermined composition is obtained. It can be made by cutting into dimensions.

  As the polyisocyanate, 4,4′-diphenylmethane diisocyanate (MDI) is preferable, but is not particularly limited, and the following polyisocyanates can also be used. For example, isophorone diisocyanate, 4,4′-dicyclohexyl diisocyanate, trimethylhexamethylene diisocyanate, tolylene diisocyanate, carbodiimide modified diisocyanate, polymethylene phenyl polyisocyanate, orthotoluidine diisocyanate, naphthalene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, paraphenylene Examples include diisocyanate, lysine diisocyanate methyl ester, and dimethyl diisocyanate. These may be used alone or in combination of two or more.

  The polyol used together with the polyisocyanate is not particularly limited, and for example, a conventionally known polyol can be used. Specific examples include adipate polyesters such as polyethylene adipate polyester polyol, polybutylene adipate polyester polyol, polyhexylene adipate polyester polyol, polyethylene-propylene adipate polyester polyol, polyethylene-butylene adipate polyester polyol, and polyethylene-neopentylene adipate polyester polyol. A polyol etc. are mentioned. Moreover, polyether polyols, such as polycaprolactone type | system | group polyester polyol obtained by ring-opening polymerization of caprolactone, polyethyleneglycol, polypropylene glycol, polytetramethylene glycol, are mentioned. Polycarbonate diol may also be used. These may be used alone or in combination of two or more.

  The chain extender is not particularly limited, and for example, a conventionally known polyol can be used. Specifically, 1,4-butanediol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, xylylene glycol And polyols having a molecular weight of 200 or less, such as triethylene glycol, trimethylolpropane, glycerin, pentaerythritol, sorbitol, 1,2,6-hexanetriol. These may be used alone or in combination of two or more.

  Examples of the urethane curing catalyst include amine compounds such as tertiary amines and organometallic compounds. Urethane curing catalysts are roughly classified into isocyanurate-forming catalysts and urethane-forming catalysts. As the urethane curing catalyst, it is preferable to use an isocyanurate-forming catalyst and a urethane-forming catalyst in combination.

  Examples of the isocyanuration catalyst include tertiary amines such as N-ethylpiperidine, N, N′-dimethylpiperazine and N-ethylmorpholine; tetraalkylammonium such as tetramethylammonium, tetraethylammonium and tetrabutylammonium. Hydroxides and weak organic acid salts; Hydroxyalkylammonium hydroxides and weak organic acid salts such as trimethylhydroxypropylammonium and triethylhydroxypropylammonium; acetic acid, propionic acid, butyric acid, caproic acid, capric acid, valeric acid, octylic acid, myristic acid , One of alkali metal salts of carboxylic acids such as naphthenic acid, or a mixture thereof. Among these, alkali metal salts of carboxylic acids that do not bloom after molding and do not affect other parts are preferable. These may be used alone or in combination of two or more.

  As the urethanization catalyst, a commonly used polyurethane curing catalyst can be used, and examples thereof include a tertiary amine catalyst. Specifically, amino alcohols such as dimethylethanolamine and N, N, N′-trimethylaminopropylethanolamine; trialkylamines such as triethylamine; N, N, N ′, N′-tetramethyl-1,3- Examples include tetraalkyl diamines such as butane diamine; triethylene diamine, piperazine, and triazine. Moreover, the metal catalyst normally used for urethane may be sufficient and a dibutyltin dilaurate etc. can be illustrated. Of these, amino alcohols that are reactive and bloom after molding without affecting other parts are preferred. More preferred is N, N, N'-trimethylaminopropylethanolamine. These may be used alone or in combination of two or more.

As for the kind and the compounding quantity of each component used for the blade member of the cleaning blade of the present invention, the polyurethane elastomer preferably contains (A) to (E) described later. In addition, it is preferable to select and form the polyisocyanate so that the concentration of (A) polyisocyanate calculated by the following formula (I) satisfies 1.00 mmol / g or more and 1.15 mmol / g or less. Hereinafter, the preferable form is demonstrated.
(A) Polyisocyanate (B) Polyol having a number average molecular weight of 2000 or more and 4000 or less (C) Chain extender having a molecular weight of 200 or less (D) Polyol (E) for curing a polyol (E) having a number average molecular weight of more than 200 and less than 2000 Catalyst (A) Concentration of polyisocyanate (mmol / g)
= W _iso / (Mn _iso × W _all ) × 1000 (I)
(In the formula (I), W _iso is the charged amount of (A) polyisocyanate (g), Mn _iso is the number average molecular weight of (A) polyisocyanate, and W _all is the material of (A) to (E). (Represents total mass (g))
Here, when the concentration of the polyisocyanate (A) is less than 1.00 mmol / g, the amount of hard segments in the polyurethane elastomer is reduced and softened, so the above conditions (1) to (4) may not be satisfied. is there. On the other hand, when the polyisocyanate concentration exceeds (A) 1.15 mmol / g, the amount of hard segments in the polyurethane elastomer increases and becomes too hard, so the physical properties of the above conditions (1) to (4) are not satisfied. There is.

  (A) As polyisocyanate, the polyisocyanate mentioned above can be used. 4,4'-diphenylmethane diisocyanate is preferred. It is preferable to use 25-30 mass parts of (A) polyisocyanate with respect to a total of 100 mass parts of (A)-(D).

  (B) As the polyol, a polyol having a number average molecular weight of 2000 or more and 4000 or less is used. (B) As for the number average molecular weight of the whole polyol, 2000-2800 are preferable. It is preferable to use 52 to 60 parts by mass of (B) polyol with respect to 100 parts by mass in total of (A) to (D).

  (A) Polyisocyanate and (B) polyol are prepolymerized before use. The mass ratio of (A) polyisocyanate and (B) polyol used for prepolymerization is preferably 30/70 to 40/60.

  (C) As the chain extender, the above-described chain extender having a molecular weight of 200 or less can be used. 1,4-butanediol and trimethylene glycol are preferred. It is preferable to use 3 to 5 parts by mass of the chain extender (C) with respect to 100 parts by mass in total of (A) to (D).

  (D) As the polyol, a polyol having a number average molecular weight larger than 200 and smaller than 2000 is used. Specifically, (D) The number average molecular weight of the whole polyol is preferably 500 to 1500. It is preferable to use 9 to 15 parts by mass of (D) polyol with respect to 100 parts by mass in total of (A) to (D).

  (E) As the urethane curing catalyst, an all-resin urethane curing catalyst can be used. It is preferable to use an isocyanurate catalyst and a urethanization catalyst in combination. It is preferable to use 0.04 to 0.06 parts by mass of the catalyst for urethane curing (E) with respect to 100 parts by mass in total of (A) to (D).

  In the present invention, a cleaning blade is produced in the following manner, for example, according to the prepolymer method. First, a cleaning blade mold is prepared, and a holder to be a support member is disposed. Next, a urethane rubber prepolymer partially polymerized with a polyol (preferably polyisocyanate and polyester polyol), a urethane curing catalyst and a chain extender is added to the casting machine and stirred in the mixing chamber. A liquid mixture is obtained. A cleaning blade in which a blade member made of polyurethane elastomer is molded on a holder can be manufactured by pouring this into the mold, reaction curing, then removing the cured product, and cutting to a predetermined size. it can. It is preferable to apply an adhesive to the portion of the holder where the blade member is molded.

  FIG. 1 shows a configuration example of the cleaning blade of the present invention. In the cleaning blade shown in FIG. 1, a blade member 150 having an L-shaped cross section in the free length direction 110 and the thickness direction 120 of the cleaning blade is uniformly formed in the longitudinal direction 100 of the holder 130. The formation position and shape of the blade member in the cleaning blade can be appropriately selected so that the blade member can come into contact with the photosensitive drum.

The blade member possessed by the cleaning blade thus obtained must satisfy the following conditions.
(1) 100% modulus in tensile test is 3.0 MPa or more and 5.0 MPa or less (2) Elongation at break in tensile test is 300% or less (3) Hardness is 65 ° or more and 75 ° or less (IRHD)
(4) The peak temperature of tan δ in the dynamic viscoelasticity test is 0 ° C. or less. When the 100% modulus during the tensile test is less than 3.0 MPa, the linear pressure at the blade edge portion on the surface of the photosensitive drum is insufficient, Since the toner slips through, cleaning defects are likely to occur, and the blade edge is likely to be deformed, so that chipping is likely to occur. When the pressure exceeds 5.0 MPa, the linear pressure of the blade edge applied to the surface of the photosensitive drum is increased, and wear of the blade edge or the surface of the photosensitive drum is likely to occur. Preferably, it is 4.0-4.5 MPa.

  Further, when the elongation at break in the tensile test exceeds 300%, when the blade edge is chipped due to rubbing against the photosensitive drum, the chip is likely to be large, which causes a cleaning failure. Preferably, it is 250% or less. From the viewpoint of wear resistance, the elongation at break during the tensile test is preferably 150% or more.

  When the hardness is less than 65 ° (IRHD), the blade edge is soft and the toner tends to slip through. When the hardness exceeds 75 ° (IRHD), the blade edge becomes too hard and the photosensitive drum wears quickly. Preferably, it is 67-73 degrees (IRHD).

  When the tan δ peak temperature in the dynamic viscoelasticity test is higher than 0 ° C, the rubber property of the urethane elastomer is reduced in a low temperature (0 to 10 ° C) environment and cannot be uniformly contacted with the drum. Defects are likely to occur. Preferably, it is −5 ° C. or lower. Further, from the viewpoint of cleaning in a high temperature region, the tan δ peak temperature in the dynamic viscoelasticity test is preferably −15 ° C. or higher.

  By setting the 100% modulus, elongation at break, hardness, and tan δ peak temperature of the polyurethane elastomer constituting the blade member, a cleaning blade having good cleaning performance can be obtained even for spherical toner. In addition, about the measuring method of these physical properties, it demonstrates in the below-mentioned Example.

  FIG. 2 is an example of an image forming apparatus to which the cleaning blade of the present invention can be applied.

  FIG. 2 is an example of an image forming apparatus to which the cleaning blade of the present invention can be applied.

  In the image forming apparatus shown in FIG. 2, an image carrier 51 such as a photosensitive drum is rotationally driven around the support shaft in the clockwise direction in the drawing at a predetermined peripheral speed. The surface of the image carrier 51 is subjected to a primary charging process so as to have a predetermined polarity and potential by a charging member 52 such as a corona discharger or a charging roller. The surface of the image carrier 51 that has been uniformly charged is then subjected to exposure of target image information (laser beam scanning exposure, slit exposure of a document image, etc.) by the exposure means L, and a static image corresponding to the target image information. An electrostatic latent image 53 is formed. Then, the electrostatic latent image 53 is sequentially visualized as a toner image by the developing unit 54.

  The toner image formed on the surface of the image carrier 51 is then transferred to the surface side of the transfer material P by the transfer means 55. The transfer material P is conveyed from an unillustrated paper feeding unit to the transfer unit between the image carrier 51 and the transfer unit 55 at an appropriate timing in synchronization with the rotation of the image carrier 51. The transfer means 55 in this example is a corona discharger, and the toner image on the surface of the image carrier 51 is transferred to the surface side of the transfer material P by charging the reverse polarity of the toner from the back of the transfer material P. The transfer means 55 may be a roller type. In addition, in a color LBP that outputs a color image using four color toners, for example, the toner is temporarily transferred to an intermediate transfer member such as a roller or a belt in order to develop and visualize the four color images. The toner image is transferred to the surface side of the transfer material P. The transfer material P that has received the transfer of the toner image is separated from the image carrier 55 and is forwarded to fixing means 58 such as a heat fixing roll to receive image fixing and output as an image formed product.

  After the transfer, the surface of the image carrier 51 is cleaned by the cleaning means 56 after removal of attached contaminants such as residual toner, and is repeatedly used for image formation. As the cleaning means 56, the cleaning blade of the present invention can be preferably used.

  Examples of the image forming apparatus to which the cleaning blade of the present invention can be applied include an image forming apparatus using an electrostatic transfer process such as an electrophotographic copying machine, a laser beam printer, and a facsimile. Further, among the components in the image forming apparatus such as the image carrier, the charging unit, the developing unit, and the cleaning unit, a process cartridge in which a plurality of elements are integrally incorporated, and the process cartridge can be attached to and detached from the apparatus main body. You can also

  Next, examples and comparative examples of the present invention will be shown. The present invention is not limited only to these examples.

Example 1
(Preparation of thermosetting polyurethane raw material composition)
In the ratio shown in Table 1, (A) 4,4′-diphenylmethane diisocyanate (MDI) and (B) polybutylene adipate polyester polyol (PBA, number average molecular weight 2000) were reacted for 120 minutes in an 80 ° C. nitrogen atmosphere. A prepolymer was obtained. Moreover, in the ratio shown in Table 1, (C) 1,4-butanediol (1,4-BD) and trimethylolpropane (TMP), (D) polyhexylene adipate polyester polyol (PHA, number average molecular weight 1000) ) And (E) catalyst were mixed to obtain a curing agent.

When the blade member was molded using the prepolymer and the curing agent, a polyurethane raw material composition was prepared in which the ratio of hydroxyl groups to isocyanate groups (α value) was 0.65. The number average molecular weight is calculated according to a conventional method by preparing a calibration curve between the peak count number and the number average molecular weight of the monodisperse polystyrene by GPC using monodisperse polystyrene for gel permeation chromatography (GPC). The measurement conditions of such a sample are as follows: Column: G3000PWXL × 2 (manufactured by Tosoh Corporation), elution solvent: 20 mM phosphate buffer, detector: differential refractometer, flow rate: 0.5 mL / min, sample solution usage: 10 μL, The column temperature was 45 ° C. )
(Manufacture of cleaning blades)
A holder was prepared as a support member in advance, and an adhesive was applied to one end surface of the holder. Placed in a mold for cleaning blade consisting of upper mold and lower mold with one end of adhesive applied to the holder protruding into the cavity and injecting the thermosetting polyurethane raw material composition into the cavity did. This was reaction-cured at a heating temperature of 130 ° C., and then the cured product was removed from the mold and cut into a predetermined size to produce a cleaning blade in which a blade member was molded on the holder.

  The cleaning blade thus prepared was subjected to measurement of 100% modulus and elongation at break, measurement of hardness, measurement of tan δ peak temperature, image evaluation, flowability evaluation, and dent pattern evaluation in a tensile test.

[Measurement of 100% modulus (M100)]
The measurement of the 100% modulus of the blade member constituting the produced cleaning blade was performed based on JIS K6251 using a tensile tester (trade name: Unitron TS-3013) manufactured by Ueshima Seisakusho. The results are shown in Table 3.

[Measurement of Elongation at Break (EB)]
The elongation at break of the blade member constituting the produced cleaning blade was measured using a tensile tester (trade name: Unitron TS-3013) manufactured by Ueshima Seisakusho based on JIS K6251. The results are shown in Table 3.

[Measurement of hardness]
The measurement of the international rubber hardness of the blade member constituting the produced cleaning blade was performed based on JIS K6253 using a hardness meter manufactured by HW WALLACE. The results are shown in Table 3.

[Measurement of tan δ peak temperature]
The tan δ peak temperature of the blade member constituting the produced cleaning blade was measured using DMS6100 (trade name) manufactured by Seiko Instruments Inc. as follows. First, a strip-shaped test piece was prepared from the blade member of the produced cleaning blade. Next, after fixing this test piece so that the measurement length is 20 mm, the test piece is distorted at an amplitude of 5 μm and a frequency of 10 Hz, and at a heating rate of 2 ° C./min, about every 0.5 ° C. Tan δ from −30 ° C. to 60 ° C. was measured. The temperature at which the value of tan δ is maximum is taken as the peak temperature of tan δ.

[Image evaluation]
The prepared cleaning blade was incorporated into a Canon LASER SHOT LBP-2510 (trade name) manufactured by Canon, and a cleaning property test was performed to observe the cleaning property (under 10 ° C./30%, 23 ° C./55% environment). Here, “Good” indicates that the cleaning property is good, and “No” (minor) or × (noticeable) indicates that the cleaning failure occurred depending on the degree. The results are shown in Table 3.

[Flowability evaluation]
As the flowability to the cleaning blade mold, the cleaning blade formed by reaction curing was visually observed, the presence or absence of unfilled parts due to flow failure was inspected, and the flowability to the mold was evaluated according to the following criteria.

  ○: No unfilled site was found.

  X: The unfilled site | part was recognized.

[Evaluation of dent pattern]
The appearance of 100 cleaning blades formed by reaction curing was visually observed, and the number of cleaning blades in which a dent pattern was found on the blade member was determined and evaluated according to the following criteria.

  ○: The number of dent patterns was 0.

  (Triangle | delta): The number of what the dent pattern was recognized was 1-30.

  X: The number of the thing in which the dent pattern was recognized was 31 or more.

Example 2
A cleaning blade was prepared and evaluated in the same manner as in Example 1 except that a prepolymer and a curing agent were prepared according to the formulation shown in Table 1 and the α value was 0.6. The results are shown in Table 3.

Comparative Example 1
(D) A cleaning blade was prepared and evaluated in the same manner as in Example 1 except that a prepolymer and a curing agent were prepared with the formulation shown in Table 2 without using a polyol, and the α value was 0.65. went. The results are shown in Table 3.

Comparative Example 2
A cleaning blade was prepared and evaluated in the same manner as in Example 1 except that a prepolymer and a curing agent were prepared with the formulation shown in Table 2 and the α value was set to 0.8. The results are shown in Table 3.

  In Tables 1 and 2, the numbers in the columns of MDI, PBA, PHA, 1,4-BD, TMP, and (E) the nurating catalyst and the urethanizing catalyst represent parts by mass.

Moreover, the following were used as each said constituent material.
・ 4,4′-diphenylmethane diisocyanate (MDI): Millionate MT (trade name), manufactured by Nippon Polyurethane Industry Co., Ltd.・ 1,4-Butanediol (1,4-BD): manufactured by Mitsubishi Chemical Corporation ・ Trimethylolpropane (TMP): manufactured by Mitsubishi Gas Chemical Co., Ltd. ・ Polyhexylene adipate polyester polyol (PHA): NIPPOLAN 164 ( (Trade name), Nippon Polyurethane Industry Co., Ltd., urethane curing catalyst (urethane catalyst): POLYCAT 17 (trade name), Tosoh Corporation, urethane curing catalyst (nurate catalyst): P15 (trade name) Made by Air Products Japan

  As can be seen from the results shown in Table 3, the cleaning blades produced in Examples 1 and 2 exhibited good cleaning performance with no cleaning failure. Moreover, since (D) polyol was used, there was no problem in the flowability to the mold and the dent pattern. On the other hand, in the cleaning blade produced in Comparative Example 1, the 100% modulus and the tan δ peak temperature of the polyurethane elastomer are outside the scope of the present invention, and due to poor cleaning in a low temperature and low humidity environment of 10 ° C / 30%. An image defect occurred. Moreover, (D) Since the polyol was not used, poor flowability to the mold and a dent pattern occurred. In the cleaning blade produced in Comparative Example 2, the 100% modulus and elongation at break of the polyurethane elastomer are outside the scope of the present invention, so that sufficient contact pressure against the photosensitive drum cannot be obtained, and a large chip occurs. As a result, a cleaning failure occurred.

It is a typical perspective view showing a schematic structure of a cleaning blade concerning one embodiment of the present invention. 1 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus to which a cleaning blade according to an embodiment of the present invention can be applied.

Explanation of symbols

51 Image carrier 52 Charging means 53 Electrostatic latent image 54 Developing means 55 Transfer means 56 Cleaning means 58 Fixing means 130 Holder 150 Blade member L Exposure means P Transfer material

Claims (5)

A cleaning blade that is disposed in an image forming apparatus using an electrostatic transfer process and has a blade member made of polyurethane elastomer for rubbing and removing residual toner on a photosensitive drum included in the image forming apparatus. A cleaning blade, wherein the polyurethane elastomer satisfies the following (1) to (4).
(1) 100% modulus in tensile test is 3.0 MPa or more and 5.0 MPa or less (2) Elongation at break in tensile test is 300% or less (3) Hardness is 65 ° or more and 75 ° or less (IRHD)
(4) Tan δ peak temperature in dynamic viscoelasticity test is 0 ° C or less The urethane elastomer contains at least the following materials (A) to (E), and (A) the polyisocyanate concentration calculated by the following formula (I) is 1.00 mmol / g or more and 1.15 mmol / g. The cleaning blade according to claim 1, wherein:
(A) Polyisocyanate (B) Polyol having a number average molecular weight of 2000 or more and 4000 or less (C) Chain extender having a molecular weight of 200 or less (D) Polyol (E) curing catalyst having a number average molecular weight of more than 200 and less than 2000 (A) Polyisocyanate concentration (mmol / g)
= W _iso / (Mn _iso × W _all ) × 1000 (I)
(In the formula (I), W _iso is the charged amount of (A) polyisocyanate (g), Mn _iso is the number average molecular weight of (A) polyisocyanate, and W _all is the material of (A) to (E). (Represents total mass (g)) The (B) polyol having a number average molecular weight of 2000 or more and 4000 or less contains at least one of polybutylene adipate polyester polyol and polyhexylene adipate polyester polyol, and the number average molecular weight is 2000 or more and 4000 or less,
The (D) polyol having a number average molecular weight of greater than 200 and less than 2000 includes at least one of polybutylene adipate polyester polyol and polyhexylene adipate polyester polyol, and the number average molecular weight is greater than 200 and less than 2000.
The polyurethane elastomer comprises at least a prepolymer obtained from the above (A) and (B) and a curing agent containing at least the above (C) to (E), a polybutylene adipate polyester polyol, a polyhexylene adipate polyester polyol, The cleaning blade according to claim 2, wherein the cleaning blade is obtained by mixing and curing so that the molar ratio (α value) of the hydroxyl group to the isocyanate group is 0.5 or more and 0.7 or less.   4. The cleaning blade according to claim 2, wherein the (A) polyisocyanate is 4,4'-diphenylmethane diisocyanate.   The cleaning blade according to claim 2, wherein the (E) urethane curing catalyst contains an isocyanurate-forming catalyst and a urethanization catalyst.

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