Developing blade and its manufacturing method

A developing blade (1) comprises a support member (2) having a coefficient of elasticity in the range of 0.5×104 to 4.0×104 kg/mm2 and a moment of inertia of area (Iz) in the range of 6.5E-04 to 1.2E-02, and a blade member (4) located on one surface of the support member (2) along one side edge (2A). The blade member (4) is made of a rubber material having a 25% modulus of no greater than 0.85 MPa, and has a moment of inertia of area (Iz) in the range of 8E-02 to 1.2E+01, and the blade member (4) has a warping of no greater than 10 mm in the longitudinal direction.

TECHNICAL ART

The present invention relates generally to a developing blade and its manufacturing method, and more specifically to a developing blade used with developer equipment for electrophotographic imagers such as laser printers, copiers and facsimiles, and its manufacturing method.

BACKGROUND ART

An imager making use of an electrophotographic imaging process comprises developer equipment for developing latent images on a photosensitive drum. For this developer, as shown typically inFIG. 12, there is a developer61known so far in the art, which is of the structure that comprises a hopper62, a developing roller63, a rotatable agitator64and a developing blade65(JP(A)2003-43812). With this developer61, a toner66in the hopper62is fed by the agitator64to the developing roller63so that the toner in thin layer form is uniformly carried on the peripheral surface of the developing roller63by frictional electrification between the developing blade65and the developing roller63. And then, the toner66passes from the developing roller63onto the photosensitive drum67with a latent image formed on it for development.

As shown typically inFIG. 13, the developing blade65known so far in the art is of the structure that comprises a rubber blade member74along the side edge72A of a metallic support member72having a thickness of about 0.1 mm.

A problem with the conventional developing blade is, however, that the support member72is deformed and warped toward the blade member74depending on differences in thermal shrinkage between them, because the blade member74is formed on one surface of the support member72. The developing blade undergoing such warpage is poor in handling capabilities, and poor in mounting capabilities as well, because the deformed product must be flattened for mounting.

And now, the aforesaid warping of the developing blade may be held back by increasing the thickness or width of the support member72or diminishing the width of the blade member74. However, as the thickness or width of the support member72grows large, it causes the spring action of the support member72to become worse, often doing some detriment to the appearance of the function of the developing blade in the developer or working to the detriment of size reductions of the developer, resulting in added manufacturing costs. A problem with diminishing the width of the blade member74is that it is difficult to form the blade member74by means of molding or it is detrimental to the appearance of the function of the developing blade in the developer.

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a developing blade that, albeit having sufficient spring action, is substantially free from warping, and a method for manufacturing such a developing blade.

According to the invention, such an object is accomplishable by the provision of a developing blade, comprising a support member and a blade member located on one surface of said support member along one side edge of said support member, wherein said support member has a coefficient of elasticity in the range of 0.5×104to 4.0×104kg/mm2and a moment of inertia of area (Iz) in the range of 6.5E-04 to 1.2E-02, said blade member is made of a rubber material having a 25% modulus of no greater than 0.85 MPa and has a moment of inertia of area (Iz) in the range of 8E-02 to 1.2E+01, and said blade member has a warping of no greater than 10 mm in the longitudinal direction.

In an embodiment of the invention, said support member is made of stainless steel and has a thickness of 0.07 to 0.2 mm and a width of 12 to 30 mm.

In an embodiment of the invention, said support member is made of phosphor bronze and has a thickness of 0.2 to 0.4 mm and a width of 12 to 30 mm.

In an embodiment of the invention, said side edge of said support member extends 0.02 to 2 mm out of the top end of said blade member.

In an embodiment of the invention, said support member has at a peripheral edge a minute projection jutting toward a surface having said blade member.

Albeit using the very thin support member having a coefficient of elasticity in the range of 0.5×104to 4.0×104kg/mm2and a moment of inertia of area (Iz) in the range of 6.5E-04 to 1.2E-02, such a developing blade of the invention as described above can have a warping of no greater than 10 mm in the longitudinal direction by using the blade member having a 25% modulus and a moment of inertia of area (Iz) within the predetermined ranges. This makes the developing blade excellent in flatness and allows the support member to produce good spring action. Thus, the ability of the developing blade to be mounted on a developer is improved without detrimental to the function of the developer and size reductions of the developer.

The invention also provides a method for manufacturing a developing blade comprising a blade member along one side edge of a support member by using as the support member a material having a coefficient of elasticity in the range of 0.5×104to 4.0×104kg/mm2and a moment of inertia of area (Iz) in the range of 6.5E-04 to 1.2E-02, using as the blade member a rubber material having a 25% modulus of no greater than 0.85 MPa and having a moment of inertia of area (Iz) in the range of 8E-02 to 1.2E+01, and using as a mold assembly a top mold comprising a mold surface with a cavity formed in it for the formation of the blade member and a gate in communication with said cavity, and a bottom mold having a flat mold surface, wherein while said cavity is closed up with said support member and the neighborhood of said side edge of said support member is held between the edge of said cavity in the top mold and the bottom mold, the top and bottom molds are brought in alignment and clamped together, so that a molding material is poured from said gate into said cavity.

In an embodiment of the invention, a portion 0.02 to 2 mm away from said side edge of said support member is held between the edge of said cavity in the top mold and the bottom mold.

In an embodiment of the invention, said support member has a minute projection at a side edge of one surface, and said support member is held while the surface having said minute projection faces the mold surface of said top mold.

With such an inventive manufacturing method as described above, it is possible to manufacture a developing blade that, albeit having sufficient spring action, is substantially free of warping. Further, the top and bottom molds are clamped together while the neighborhood of the side edge of the support member is held between the edge of the cavity in the top mold and the bottom mold, so that the top mold is in firm engagement with the neighborhood of the side edge of the support member, whereby entrance of the molding material between the top and the support member is staved off, and a developing blade with none of fins at the end (the side edge of the support member) can be manufactured.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the invention are now explained with reference to the drawings.

FIG. 1is a plan view of one embodiment of the developing blade according to the invention, andFIG. 2is illustrative in section of the developing blade shown inFIG. 1;FIG. 2Ais a sectional view as taken on arrowed line A-A andFIG. 2Bis a sectional view as taken on arrowed line B-B. As depicted inFIGS. 1 and 2, a developing blade1comprises a support member2and a blade member4formed on one surface of the support member2along one side edge2A, and the warping of the blade member in the longitudinal direction (the direction indicated by an arrow a inFIG. 1) is 10 mm or less.

The support member2forming a part of the developing blade1has a coefficient of elasticity in the range of 0.5×104to 4.0×104kg/mm2, preferably 1.0×104to 3.0×104kg/mm2, and a moment of inertia of area (Iz) in the range of 6.5E-04 to 1.2E-02, preferably 9.4E-04 to 5.2E-03. In other words, there is no limitation imposed on the material of the support member2; use may be made of, for instance, a metal substrate such as one made up of stainless steel, e.g., SUS301 and SUS304, and phosphor bronze for springs, e.g., C5210, and beryllium copper, a ceramics substrate, a resin substrate such as one made up of PC (polycarbonate), and PBT (polybutylene terephthalate), and a carbon fiber substrate.

The thickness and width of the support member2may be determined as desired in consideration of what it is made of. For instance, when the material is stainless steel, the thickness may be selected from the range of 0.07 to 0.2 mm, preferably 0.09 to 0.15 mm and the width from the range of 12 to 30 mm, preferably 15 to 25 mm, and when the material is phosphor bronze, the thickness may be selected from the range of 0.2 to 0.4 mm, preferably 0.25 to 0.35 mm and the width from the range of 12 to 30 mm, preferably 15 to 25 mm.

The coefficient of elasticity of the support member here is measured according to the metal material tensile testing method JIS Z2241.

The moment of inertial of area (Iz) is figured out of the equation: Iz=∫y2dA, where y is the distance from the center of gravity to a minute area dA, and dA is the minute area. More specifically, the moment of inertia of area (Iz) is worked out as follows.

(i) When the sectional shape of the support member is, or is approximate to, a triangle, it is worked out from the following equation (1):
Iz=bh3/36  Eq. 1

(b: the length (mm) of the base, and h: the height (mm))

(ii) When the sectional shape of the support member is, or is approximate to, a semicircle, it is worked out from the following equation (2):
Iz=0.1098r4Eq. 2

(r: the radius (mm) of the semicircle)

(iii) When the sectional area of the support member is, or is approximate to, a quarter circle, it is worked out from the following equation (3):
Iz=0.055r4Eq. 3

(r: the radius (mm) of the quarter circle)

(iv) When the sectional shape of the support member is, or is approximate to, a square, it is worked out from the following equation (4):
Iz=bh3/12  Eq. 4

(b: the width (mm), and h: the height (mm))

However, when the sectional area of the support member lies somewhere between the aforesaid cases (i), (ii), (iii) and (iv) and it is difficult to determine which of equations 1 to 4 applies in this case, the values of Iz's from multiple equations that seem pertinent are figured out and their average is taken as the moment of inertia of area (Iz). Further, when the sectional area of the support member comprises a combination of two or more of the aforesaid cases (i) to (iv), Iz is figured out from any one of equations (1) to (4) for each shape and the sum is taken as the moment of inertia of area (Iz).

In the embodiment illustrated, the support member2also comprises a plurality of holes3along the side edge2B opposite to the side edge2A. Such holes3may optionally be used for mounting, alignment or the like; they are never limited to what is illustrated in the drawings.

The blade member4comprises a blade body5formed along the side edge2A of the support member2and a skirt6positioned at one end of the blade body5. The area of contact of the blade body5with a developing roller defines a curved surface that, in the embodiment illustrated, is of an almost semicircular shape in section.

In the developing blade1illustrated, the side edge2A of the support member2extends out of the end portion5A of the blade body5of the blade member4. In such a case, the distance L (seeFIGS. 1,2A and2B) between the end portion5A of the blade body5and the side edge2A of the support member2may be in the range of 0.02 to 2 mm, preferably 0.02 to 1 mm, and more preferably 0.3 to 1 mm. It is here noted that the developing blade of the invention is never limited to the embodiment illustrated; for instance, the side edge2A of the support member2and the end portion5A of the blade body5of the blade member4may define together the same end face, or the side edge2A of the support member2may be of such structure as to be covered with the blade body5.

The skirt6defines a site where a gate is to be positioned in the top mold to be described later. As shown in depicted inFIG. 3, the blade body5may comprise skirts6aand6bat both its ends. In this case, the skirt6adefines a site where the gate is to be located in the top mold to be described later, and the skirt6bworks making smoother the flow of a molding material poured from the skirt6afor the formation of the blade body5. However, the gate may be located at either the skirt6aor6b.

Such blade member4has a 25% modulus of no greater than 0.85 MPa, and preferably in the range of 0.3 to 0.6 MPa, and a moment of inertia of area (Iz) in the range of 8E-02 to 1.2E+01, preferably 4.2E-01 to 6.0E+00. A 25% modulus exceeding 0.85 MPa is not preferable because there is likely to be a warp (deformation) of greater than 10 mm in the aforesaid support member2. As the moment of inertia of area (Iz) is less than 8E-02, it may make the molding of the blade member4difficult or may do damage to the function of the developer equipment. A moment of inertia of area (Iz) exceeding 1.2E+01, on the other hand, is not preferable because it may be detrimental to size reductions of the developer equipment and result in added manufacturing cost.

The 25% modulus here is measured pursuant to the low deformation tensile testing method JIS K6254. In this case, measurement is carried out with a strip-form test piece of 5 mm in width, 100 mm in length and 2.0±0.2 mm in thickness and a gauge-to-gauge distance set at 40 mm at the middle of the test piece in the longitudinal direction while the test piece is elongated 25% (the gauge-to-gauge distance changes from 40 mm to 50 mm) at a tensile rate of 50±5 mm/min. Note here that the measuring gauge used is Strograph made by Toyo Seiki Co., Ltd. The moment of inertia of area (Iz) of the blade member is figured out as is the case with the moment of inertia of area of the aforesaid support member.

To determine the degree of warping (deformation) of the developing blade, a developing blade comprising a support member of 18 mm in width W and 240 mm in length L (seeFIG. 1) is placed on a horizontal plate with the blade member turned upside to obtain measurements for the maximum amount of warping (deformation) from the horizontal plate to the support member2at both ends2aand2bof the support member2in the longitudinal direction of the blade member4so that they are summed up to find the amount of warping (deformation) (mm). Referring typically toFIG. 4, when of the amounts of warping h1and h2at two corners of one end2a, the maximum amount of warping is h1, and of the amounts of warping h3and h4at two corners of the other end2b, the maximum amount of warping is h3, the amount of warping of the developing blade1becomes (h1+h3). As a matter of course, the measurement of the amount of warping is not limited to the corners of each end, and includes deformation of the developing blade due to its own weight.

The blade member4may be made of any desired material having a 25% modulus of no greater than 0.85 MPa, for instance, silicone rubber (Q), nitrile rubber (NBR), flurorubber (FKM), urethane rubber (U), epichlorohydrin rubber (CO), and hydrogenated nitrile rubber (HNBR).

FIG. 5is a plan view of another embodiment of the developing blade according to the invention. InFIG. 5, a developing blade11comprises a support member12and a blade member14formed on one surface of the support member12along one side edge12A. And the blade member14comprises a blade body15and a skirt16formed along the blade body15. As is the case with the aforesaid skirt6, that skirt16defines a site for locating a gate in the top mold to be described later, and works making smooth the flow of a molding material poured for the formation of the blade body15. The gate may be located at either one or the other end of the skirt16.

It is noted here that the support member12forming a part of the developing blade11comprises a plurality of holes13along the other side edge12B.

In that developing blade11, too, the side edge12A of the support member12may extends out of the end portion15A of the blade body15of the blade14, in which case the distance between the end portion15A of the blade body15and the side edge12A of the support member12may be in the range of 0.02 to 2 mm, preferably 0.02 to 1 mm, and more preferably 0.3 to 1 mm.

FIG. 6is illustrative in section, as inFIG. 2A, of yet another embodiment of the developing blade according to the invention. InFIG. 6, a developing blade21comprises a support member22and a blade member24formed on one surface of the support member22along one side edge22A. In that developing blade21, the blade member24comprises a blade body25and a skirt26continuously integral with the blade body25. As is the case with the aforesaid skirt6, such skirt26defines a site for locating a gate in the top mold to be described later, and works making smooth the flow of a molding material poured for the formation of the blade body25. The gate may be located at either one or the other end of the skirt26.

It is noted here that the support member22forming a part of the developing blade21comprises a plurality of holes along the other side edge22B.

In that developing blade21, too, the side edge22A of the support member22may extend out of the end portion25A of the blade body25of the blade24, in which case the distance between the end portion25A of the blade body25and the side edge22A of the support member22may be in the range of 0.02 to 2 mm, preferably 0.02 to 1 mm, and more preferably 0.3 to 1 mm.

The support member12,22and blade member14,24forming the aforesaid developing blade11,21are similar to the support member2and blade member4forming the aforesaid developing blade1. Accordingly, the support member12,22has a coefficient of elasticity in the range of 0.5×104to 4.0×104kg/mm2, preferably 1.0×104to 3.0×104kg/mm2, and a moment of inertia of area (Iz) in the range of 6.5E-04 to 1.2E-02, preferably 9.4E-04 to 5.2E-03. The blade member14,24is made of a rubber material having a 25% modulus of no greater than 0.85 MPa, preferably 0.3 to 0.6 MPa, and has a moment of inertia of area (Iz) in the range of 8E-02 to 1.2E+01, preferably 4.2E-01 to 6.0E+00.

The developing blade of the invention may be manufactured by either injection molding or transfer molding.

Taking the aforesaid developing blade1as an example, the developing blade manufacturing method of the invention is now explained.

FIGS. 7 and 8are illustrative of one example of the mold assembly used for manufacturing the developing blade of the invention by means of injection molding;FIG. 7is a sectional view of the aforesaid developing blade at a site shown inFIG. 2A, andFIG. 8is a sectional view of the aforesaid developing blade at a site shown inFIG. 2B.

Referring toFIGS. 7 and 8, a mold assembly31used herein is built up of a top mold32and a bottom mold33having a flat mold surface. The top mold32comprises a mold surface with a cavity34formed in it for the formation of a blade member, and a gate35in communication with the cavity34. The gate35is located at a site corresponding to the skirt6of the aforesaid developing blade1. And the support member2is inserted such that the cavity34is closed up with a support member2, and the neighborhood of the side edge2A of the support member2is held between the edge32A of the cavity34in the top mold and the bottom mold33. In this state, the top mold32and bottom mold33are brought in alignment with each other and clamped together. Thereafter, a molding material is poured from the gate35and filled up in the cavity34to manufacture the developing blade1.

FIG. 9is illustrative of a further embodiment of the developing blade according to the invention;FIG. 9Ais a sectional view of the developing blade at a site corresponding toFIG. 2A, andFIG. 9Bis a sectional view of the developing blade at a site corresponding toFIG. 2B. As depicted inFIG. 9, a developing blade41comprises a support member42and a blade member44formed along one side edge42A of the support member42.

The support member42forming a part of the developing blade41comprises a plurality of holes43along the side edge42B opposite to the side edge42A. The support member42also comprises a minute projection42ajutting toward the surface with the blade member44formed on it, and there are minute projections43alying around the holes43. It is here noted that each hole43is provided for mounting, alignment or the like as desired: it is never limited to the embodiment illustrated.

The blade member44is similar to the blade member4forming a part of the aforesaid developing blade1, and comprises a blade body45formed along the side edge42A of the support member42and a skirt46positioned at each end of the blade body45. In the embodiment illustrated, the side edge42A of the support member42extends out of the end portion45A of the blade body45of the blade44, in which case the distance L (seeFIG. 9) between the end portion45A of the blade body45and the side edge42A of the support member42may be in the range of 0.02 to 2 mm, preferably 0.02 to 1 mm, and more preferably 0.3 to 1 mm.

The support member42and blade member44forming the aforesaid developing blade41are similar to the support member2and blade member4forming the aforesaid developing blade1. Accordingly, the support member42has a coefficient of elasticity in the range of 0.5×104to 4.0×104kg/mm2, preferably 1.0×104to 3.0×104kg/mm2, and a moment of inertia of area (Iz) in the range of 6.5E-04 to 1.2E-02, preferably 9.4E-04 to 5.2E-03. The blade member44is made of a rubber material having a 25% modulus of no greater than 0.85 MPa, preferably 0.3 to 0.6 MPa, and has a moment of inertia of area (Iz) in the range of 8E-02 to 1.2E+01, preferably 4.2E-01 to 6.0E+00.

Taking the aforesaid developing blade41as an example, the developing blade manufacturing method of the invention is now explained.

FIGS. 10 and 11are illustrative of the mold assembly used for manufacturing the developing blade, of the invention;FIG. 10is a sectional view of the aforesaid developing blade41at a site shown inFIG. 9A, andFIG. 11is a sectional view of the aforesaid developing blade41at a site shown inFIG. 9B.

InFIGS. 10 and 11, the mold assembly51used, similar to the aforesaid mold assembly11, comprises a top mold52comprising a mold surface with a cavity54formed in it for the formation of the blade member44and a gate55in communication with the cavity54and a bottom mold53having a flat mold surface. The gate55is located at a site corresponding to the skirt46of the aforesaid developing blade41. And the support member42is inserted such that the support member42having the minute projection42aon the end side of one surface and minute projections43aaround the holes43is placed with the surface having the minute projections42aand43ain opposition to the mold surface of the top mold52, the cavity45is closed up with the support member42, and the neighborhood of the side edge42A of the support member42is held between the edge portion52A of the cavity54in the top mold52and the bottom mold53. In this state, the top mold52and bottom mold53are in alignment and clamped together. Thereafter, a molding material is poured from the gate55to fill up the cavity54to manufacture the development blade41.

The support member42having the minute projections42aand43aon one surface may be prepared by punching out a sheet material having a coefficient of elasticity in the range of 0.5×104to 4.0×104kg/mm2, preferably 1.0×104to 3.0×104kg/mm2, and a moment of inertia of area (Iz) in the range of 6.5E-04 to 1.2E-02, preferably 9.4E-04 to 5.2E-03. The minute projections42aand43ajutting from the surface of the support member42may have its height and width set in the range of, for instance, 0.02 to 0.05 mm, and 0.02 to 0.1 mm, respectively.

The width of the support member42held between the edge52A of the cavity54in the top mold52and the bottom mold53is in the range of 0.02 to 0.2 mm, preferably 0.02 to 1 mm, and more preferably 0.3 to 1 mm as viewed from the side edge42A. As the width of the held support member42is less than 0.02 mm, the engagement of the support member42including the minute projection42awith the top mold52becomes insufficient, resulting possibly in the occurrence of fins. On the other hand, exceeding 2 mm is not preferable because there is an increase in the size upon mounting of the developing blade.

In the invention, the top and bottom molds are clamped together while the neighborhood of the side edge42A of the support member42is held between the edge52A of the cavity in the top mold and the bottom mold53. Consequently, the minute projections42aand43aare deformed by the clamping pressure into firm engagement with the top mold52and, at the same time, the minute projection42aworks as a barrier, making surer prevention of fins from occurring in a direction toward the side edge42A of the support member42. Accordingly, the resultant developing blade41is free from fins at its end (the side edge42A of the support member42).

It is here understood that when the minute projections42aand43aare deformed by the clamping pressure, there is going to be a fine gap G occurring between the support member42and the top mold52, and entrance of the molding material in that gap G may give rise to fins. However, such fins have no adverse influence on the function of the developing blade41at all, because they cannot possibly be located at the end of the developing blade41(the side edge42A of the support member42).

The aforesaid embodiments have been described by way of example alone but not by way of limitation.

The invention is now explained in further details with reference to more specific examples.

A SUS301 sheet material of 0.1 mm in thickness, 18 mm in width and 240 mm in length was readied up for the support member. This support member had a coefficient of elasticity of 1.9×104kg/mm2and a moment of inertial of area (Iz) of 1.5E-0.3. Note here that the coefficient of elasticity of the support member was measured pursuant to the metal material tensile testing method JIS Z2241, and that the moment of inertia of area (Iz) was figured out from the sectional morphology of the support member: the aforesaid equation (4) Iz=bh3/12 for the rectangular support member, yielding Iz=18×0.13/12=1.5E-03.

Then, six mixtures of liquid silicone rubber and curing agents (mixtures A to F) were readied up. Then, the six mixtures as well as such an injection molding assembly as shown inFIGS. 7 and 8and the aforesaid support member were used to prepare six developing blades (samples 1 to 6). The 25% modulus of the blade member forming a part of each developing blade was measured by the following method, with the results being set out in Table 1. The moment of inertia of area (Iz) of the blade member forming a part of each developing blade was 7E-01.

(Measurement of the 25% Modulus)

Measurement was carried out pursuant to the low elongation tensile testing method JIS K6254. In this case, the six liquid silicone rubber/curing agent mixtures A to F were cured into strip-form test pieces of 5 mm in width, 100 mm in length and 2.0±2 mm in thickness. A gauge-to-gauge distance was set 40 mm at the middle of each test piece in the longitudinal direction, and it was elongated 25% at a tensile rate of 50±5 mm/minute (the gauge-to-gauge distance changed from 40 mm to 50 mm). The measuring gauge used was Strograph (made by Toyo Seiki Co., Ltd.).

The thus prepared developing blades (samples 1 to 6) were each measured for the amount of warping by the following method, with the results being set out in Table 1.

(Measurement of the Amount of Warping)

The developing blade was placed on a horizontal plate with the blade member turned upside, and the maximum amount of warping from the horizontal plate to the support member is measured at both ends of the blade member in the longitudinal direction. To find the amount of warping (deformation), these measurements (mm) are summed up.

As set out in Table 1, the developing blades (samples 1 to 4) all had an amount of warping of no greater than 10 mm, each comprising a SUS301 sheet material support member that had a coefficient of elasticity of 1.9×104kg/mm2and a moment of inertial of area (Iz) of 1.5E-03 and was very thin as expressed by a thickness (0.1 mm)-to-length (240 mm) ratio of 2,400 and a blade member that had a linear expansion coefficient one-digit different from that of the support member, a moment of inertia of area (Iz) of 7E-01 and a 25% modulus of no greater than 0.85 MPa.

The same SUS301 sheet material as in Example 1 was readied up for the support member.

Then, NBR, and FKM (LT303 made by Daikin Kogyo Co., Ltd.) and silicone rubber (X34-1595-B made by The Shin-Etsu Chemical Co., Ltd.) were readied up for the rubber material. Developing blades (samples 7 and 8) were prepared by molding blade members on one surface of the aforesaid support member by use of transfer molding. As a result of measuring the 25% modulus of the blade member forming a part of each developing blade as in Example 1, that of the developing blade (sample 7) for which NBR was used was 0.7 MPa, and that of the developing blade (sample 8) for which FKM and silicone rubber were used was 0.5 MPa. The moment of inertia of area (Iz) of the blade member was 7E-01 in both samples 7 and 8.

As a result of measuring the amount of warping of each of the thus prepared developing blades as in Example 1, that of the developing blade (sample 7) for which NBR was used was 4 mm, and that of the developing blade (sample 8) for which FKM was used was 2 mm. From this, it is found that as long as the blade member has a moment of inertia of area (Iz) of 7E-01 and a 25% modulus of no greater than 0.85 MPa, an amount of warping of no greater than 10 mm is achievable even when NBR or FKM is used as the rubber material and the SUS301 sheet material support member used has a coefficient of elasticity of 1.9×104kg/mm2and a moment of inertia of area (Iz) of 1.5E-03 and is very thin.

The same SUS301 sheet material as in Example 1 was readied up for the support member.

Then, the same liquid silicone rubber/curing agent mixture B as used in Example 1 was readied up. Then, five developing blades (samples 9 to 13) comprising blade members having different moments of inertia of area were prepared by means of injection molding as in Example 1 with the exception of using an injection molding assembly having a top mold having a different cavity capacity. The moment of inertia of area of each of the blade members forming five such developing blades (samples 9 to 13) is set out in Table 2. The 25% modulus of the blade member forming a part of each developing blade was 0.6 MPa.

The five developing blades (samples 9 to 13) prepared as described above were each measured for the amount of warping as in Example 1. The results are set out in Table 2.

As set out in Table 2, samples 9 to 12 all had an amount of warping of no greater than 10 mm, each comprising a SUS301 sheet material support member that had a coefficient of elasticity of 1.9×104kg/mm2and a moment of inertial of area (Iz) of 1.5E-03 and was very thin as expressed by a thickness (0.1 mm)-to-length (240 mm) ratio of 2,400 and a blade member that had a linear expansion coefficient one-digit different from that of the support member, a moment of inertia of area (Iz) in the range of 8E-02 to 1.2E+01 and a 25% modulus of no greater than 0.85 MPa (0.60 MPa).

In contrast, the developing blade (sample 13) comprising a blade member having a moment of inertia of area (Iz) of greater than 1.2E+01 has an amount of warping of greater than 10 mm: it could not practically be used.

Five SUS301 sheet materials (support members A to E) having a width of 18 mm and a length of 240 mm and different coefficients of elasticity were readied up for the support members. The coefficients of elasticity of such support members A to E were measured as in Example 1, with the results being set out in Table 3. Note here that the moment of inertia of area (Iz) of each of the support members A to E was 1.5E-03.

Then, the same liquid silicone rubber/curing agent mixture B as used in Example 1 was readied up, and five developing blades (samples 14 to 18) were prepared by means of injection molding as in Example 1. The blade member forming a part of each developing blade had a 25% modulus of 0.6 MPa and a moment of inertia of area of 7E-01.

The five developing blades (samples 14 to 18) prepared as described above were each measured for the amount of warping as in Example 1. The results are set out in Table 3.

As set out in Table 3, the developing blades (samples 15, 16, 17) all had an amount of warping of no greater than 10 mm, each comprising support member B, C, D having a coefficient of elasticity in the range of 0.5×104to 4.0×104kg/mm2and a moment of inertia of area (Iz) of 1.5E-03 and a blade member having a moment of inertia of area in the range of 8E-02 to 1.2E+01 and a 25% modulus of no greater than 0.85 MPa (0.60 MPa).

In contrast, the developing blade (sample 14) for which the support member A having a small coefficient of elasticity was used had an amount of warping of 15 mm. On the other hand, the developing blade (sample 18) for which the support member E having a large coefficient of elasticity was used had an amount of warping of as small as 0.1 mm; however, the support member, because of having a large coefficient of elasticity, was likely to work against the appearance of the function of the developing blade and give rise to an increase in the manufacturing cost.

Five SUS301 sheet materials (support members F to J) having a width of 18 mm and a length of 240 mm and different thicknesses were readied up for the support members. The moment of inertia of area of each support member F, G, H, I, J was figured out as in Example 1, with the results being set out in Table 4. Note here that the coefficient of elasticity of each support member F, G, H, I, J was 1.9×104kg/mm2.

Then, the same liquid silicone rubber/curing agent mixture B as used in Example 1 was readied up, and five developing blades (samples 19 to 23) were prepared by means of injection molding as in Example 1. The blade member forming a part of each developing blade had a 25% modulus of 0.6 MPa and a moment of inertia of area of 7E-01.

The five developing blades (samples 19 to 23) prepared as described above were each measured for the amount of warping as in Example 1. The results are set out in Table 4.

As set out in Table 4, the developing blades (samples 20, 21, 22) all had an amount of warping of no greater than 10 mm, each comprising support member G, H, I having a moment of inertia of area in the range of 6.5E-04 to 1.2E-02 and a coefficient of elasticity of 1.9×104kg/mm2and a blade member having a moment of inertia of area in the range of 8E-02 to 1.2E+01 (7E-01) and a 25% modulus of no greater than 0.85 MPa (0.60 MPa).

In contrast, although the developing blade (sample 19) using the support member F having a moment of inertia of area exceeding 1.2E-02 had an amount of warping of 0 mm, yet the support member was detrimental to the appearance of the function of the developing blade because of its decreased spring action. On the other hand, the developing blade (sample 23) using the support member J having a moment of inertia of area of less than 6.5E-04 had an amount of warping exceeding 10 mm, so it could not practically be used.

INDUSTRIAL APPLICABILITY

The present invention is applicable to developing blades used on developers in electrophotographic imagers.