IMAGE FORMING APPARATUS AND IMAGE FORMING METHOD
FIG10 is a graph representation illustrating a relationship between volume median diameter of toner, number average roundness of toner, and linear pressure of a cleaning blade
The minimum linear pressure necessary for cleaning was measured with respect to each of 15 toners having a D50 of 4.0 µm, 6.0 µm, or 8.0 µm and a number average roundness of 0.960, 0.965, 0.970, 0.975, or 0.980. Table 10 shows measurement results. In FIG10, the vertical axis represents minimum linear pressure necessary for cleaning (unit: N/m), and the horizontal axis represents number average roundness of toner. In FIG10, circles on the plot indicate measurement results of the toners having D50 of 4.0 µm, diamonds on the plot indicate measurement results of the toners having a D50 of 6.0 µm, and crosses on the plot indicate measurement results of the toners having a D50 of 8.0 µm. FIG10 demonstrates that the smaller D50 of toner is, the higher the minimum linear pressure necessary for cleaning is. FIG10 also demonstrates that the higher the number average roundness of toner is, the higher the minimum linear pressure necessary for cleaning is. FIG10 also indicates that a linear pressure of at least 10 N/m is necessary for the use of the toner having a D50 of 6.0 µm and a number average roundness of 0.960. FIG10 also indicates that a linear pressure of approximately 40 N/m is preferable for the use of the toner having a D50 of 4.0 µm and a number average roundness of 0.980. The above-described tendency of the photosensitive member (P-B1), which has a chargeability ratio of lower than 0.60, indicated in FIG10 is expected to be true for photosensitive members having a chargeability ratio of at least 0.60. Therefore, study was made as follows on photosensitive members that can inhibit occurrence of a ghost image even if the linear pressure of the cleaning blade is at least 10 N/m and no greater than 40 N/m.
graph
35
fixing device no greater than
5
expression
30
image forming section no greater than
20
polyarylate resin polyarylate resins
40
no greater than
10
than
15
greater than
['1. An image forming apparatus (1) comprising: an image bearing member (50); a charger (51) configured to charge a circumferential surface (50a) of the image bearing member to a positive polarity; and a cleaning member (81) pressed against the circumferential surface of the image bearing member and configured to collect a toner (T) remaining on the circumferential surface of the image bearing member, wherein a linear pressure of the cleaning member on the circumferential surface of the image bearing member is at least 10 N/m and no greater than 40 N/m, the image bearing member includes a conductive substrate (501) and a single-layer photosensitive layer (502), the single-layer photosensitive layer contains a charge generating material, a hole transport material, an electron transport material, and a binder resin, and the image bearing member satisfies formula (1),  0.60 ≦ V Q / S × d / ε r ⋅ ε 0  where in formula (1), Q represents a charge amount of the image bearing member, S represents a charge area of the image bearing member, d represents a film thickness of the single-layer photosensitive layer, ε r  represents a specific permittivity of the binder resin contained in the single-layer photosensitive layer, ε 0  represents a vacuum permittivity, V is a value calculated in accordance with the following expression: V = V 0  - V r , V r  represents a first potential of the circumferential surface of the image bearing member yet to be charged by the charger, and V 0  represents a second potential of the circumferential surface of the image bearing member charged by the charger.', '4. The image forming apparatus according to any one of claims 1 to 3, wherein the binder resin includes a polyarylate resin including a repeating unit represented by general formula (20), where in general formula (20), R 20  and R 21  each represent, independently of one another, a hydrogen atom or an alkyl group having a carbon number of at least 1 and no greater than 4, R 22  and R 23  each represent, independently of one another, a hydrogen atom, a phenyl group, or an alkyl group having a carbon number of at least 1 and no greater than 4, R 22  and R 23  may be bonded to one another to form a divalent group represented by general formula (W), and Y represents a divalent group represented by chemical formula (Y1), (Y2), (Y3), (Y4), (Y5), or (Y6), and in general formula (W), t represents an integer of at least 1 and no greater than 3, and asterisks each represent a bond']