Prime coat for improving breakdown resistance of photosensitive drum

Abstract

The invention belongs to the field of organic photoconductor drums, and particularly relates to a priming coat for improving breakdown resistance of a photoconductor drum. The adhesive comprises the following components in parts by weight: 1-5 parts of a catalyst, 3-10 parts of a dispersing agent, 5-15 parts of a coupling agent, 50-100 parts of a cross-linking agent, 250-300 parts of resin, 300-600 parts of oxide and 600-1000 parts of an organic solvent. The dielectric strength of the bottom coating of the photosensitive drum is improved, and the prepared photosensitive drum has good breakdown resistance under the conditions of normal temperature, normal humidity and low temperature and low humidity.

Description

Technical fields:

[0001] This invention belongs to the field of organic photoconductive drums, and particularly relates to a base coating that improves the puncture resistance of photoconductive drums. Background technology:

[0002] A photosensitive drum typically consists of a metal substrate (aluminum tube), a base coating, a charge generation layer (CGL), and a charge transport layer (CTL). The base coating is located between the metal substrate and the CGL, and its main functions include: blocking direct charge exchange between the metal substrate and the photoconductive layer; filling microscopic defects on the surface of the metal substrate to provide a uniform substrate for the upper layer; and optimizing the surface potential distribution to suppress charge leakage or breakdown.

[0003] During laser printing, the undercoat layer of the photosensitive drum needs to possess high uniformity, strong adhesion, resistance to charge leakage, and high resistivity (typically >10). 12 (Ω·cm) to prevent charge leakage from the photoconductive layer (CTL) to the metal substrate. However, the photosensitive drum needs to withstand a high-voltage electric field (typically ±500~1500V) during charging, exposure, and transfer. When the charging uniformity of the charging roller is poor or the dielectric strength of the undercoat is low, the undercoat is prone to breakdown. The following defects in the technical coating can easily lead to electrical breakdown, causing the photosensitive drum to fail:

[0004] 1. Insufficient material insulation: Traditional primer coatings often use a single resin, which has low dielectric strength and is prone to local breakdown under high voltage.

[0005] 2. Microscopic defects: Coating processes (such as spin coating) are prone to producing micropores, cracks or impurity accumulation, forming electric field concentration points.

[0006] 3. Charge injection effect: When the surface is rough or the interface energy level is mismatched, charge is easily injected from the substrate into the coating, accelerating the breakdown. Summary of the Invention:

[0007] The present invention addresses the above-mentioned problems by providing a base coating that improves the puncture resistance of photosensitive drums.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: an oxide is added to the traditional transport layer formulation solution to improve the dielectric strength of the undercoat and reduce the surface roughness of the undercoat, so as to effectively prevent the coating breakdown problem during the printing process and further prevent the generation of small black spots during printing.

[0009] The specific technical solution is as follows: the composition and weight parts of the primer layer are: 1-5 parts catalyst, 3-10 parts dispersant, 5-15 parts coupling agent, 50-100 parts crosslinking agent, 250-300 parts resin, 300-600 parts oxide, and 600-1000 parts organic solvent.

[0010] The catalyst is one or more of the following: quaternary ammonium salt, quaternary phosphorus salt, imidazole and its derivatives, organometallic complexes, methanesulfonic acid, and amine-blocked sulfonic acid;

[0011] The dispersant is one or more of polydimethylsiloxane, polyether-modified silicone oil, amino-modified silicone oil, and fluorosilicone compounds;

[0012] The coupling agent is one or more of aminosilane, epoxysilane, methacryloxysilane, phthalate, and aluminate.

[0013] The crosslinking agent is ethylenediamine or hexamethylenediamine;

[0014] The resin is one or more of polyester resin, polyamide resin, polyurethane resin, and epoxy resin;

[0015] The oxide may be one or more of aluminum oxide, titanium oxide, silicon oxide, and zinc oxide;

[0016] The solvent is one or more of methanol, propanol, and toluene.

[0017] The preparation method is as follows:

[0018] 1. According to the above ratio, first add some organic solvent to the glass container, then add crosslinking agent and catalyst in sequence. At 40-50℃, add resin while stirring until the solution is completely dissolved.

[0019] 2. Prepare another container, add the remaining organic solvent and dispersant, then add the coupling agent while stirring, and finally slowly add the oxide and stir for 15 minutes.

[0020] 3. After thoroughly grinding and dispersing the solutions obtained in steps 1 and 2, mix them together;

[0021] 4. After filtering the mixed solution obtained in step 3, the final base coating solution is obtained.

[0022] In practical applications, the prepared base coating solution is applied to the aluminum tube substrate and dried to obtain a photosensitive drum base coating with a thickness of 2-3 μm.

[0023] The oxide is silicon oxide.

[0024] The beneficial effects of this invention are:

[0025] 1. Reduced the surface roughness of the base coating.

[0026] 2. The dielectric strength of the bottom coating of the photosensitive drum has been improved, and the resulting photosensitive drum has good breakdown resistance under both normal temperature and humidity and low temperature and low humidity conditions. Detailed implementation method:

[0027] Example 1

[0028] In a glass container, 500g of methanol solution, 50g of ethylenediamine, and 1g of amine-blocked sulfonic acid were added sequentially, while stirring, 250g of polyamide resin was added. In another container, 500g of methanol solution and 3g of dimethylsiloxane were added, while stirring, 5g of aminosilane was added, and then 250g of modified titanium dioxide (TY-100 titanium dioxide from Ishihara, Japan) and 50g of silicon dioxide were slowly added, and stirred for 15 minutes. The above solutions were mixed and then ball-milled with zirconia for 24 hours and filtered to obtain the base coating solution 1.

[0029] The obtained base coating solution 1 was applied to two aluminum tube substrates and dried at 120°C to obtain a photosensitive drum bottom coating with a thickness of 2 μm. One of the tubes was coated with a phthalocyanine solution on the base coating and dried at 80°C to obtain a 0.5 μm charge generation layer. A charge transport solution prepared by polycarbonate, charge transport material, and tetrahydrofuran solvent (mass ratio of polycarbonate, charge transport material, and tetrahydrofuran solvent is 1:2:7) was then applied to the charge generation layer and dried at 120°C to form a 20 μm charge transport layer, thus preparing the photoreceptor 1.

[0030] Example 2

[0031] The difference between Implementation 2 and Example 1 is that 250g of modified titanium dioxide and 50g of silicon dioxide are replaced with 200g of modified titanium dioxide and 100g of silicon dioxide. The remaining steps are the same to obtain the bottom coating liquid 2, which is then coated on the aluminum tube substrate to obtain a photosensitive drum bottom coating 2 with a thickness of 2μm and to prepare the photosensitive body 2.

[0032] Example 3

[0033] The difference between Implementation 3 and Example 1 is that 250g of modified titanium dioxide and 50g of silicon dioxide are replaced with 150g of modified titanium dioxide and 150g of silicon dioxide. The remaining steps are the same to obtain the bottom coating liquid 3, which is then coated on the aluminum tube substrate to obtain a photosensitive drum bottom coating 3 with a thickness of 2μm and to prepare the photosensitive body 3.

[0034] Example 4

[0035] The difference between Implementation 4 and Example 1 is that 250g of modified titanium dioxide and 50g of silicon dioxide are replaced with 100g of modified titanium dioxide and 200g of silicon dioxide. The remaining steps are the same to obtain the bottom coating liquid 4, which is then coated on the aluminum tube substrate to obtain a photosensitive drum bottom coating 4 with a thickness of 2μm and to prepare the photosensitive body 4.

[0036] Example 5

[0037] The difference between Implementation 5 and Example 1 is that 250g of modified titanium dioxide and 50g of silicon dioxide are replaced with 50g of modified titanium dioxide and 250g of silicon dioxide. The remaining steps are the same to obtain the bottom coating liquid 5, which is then coated on the aluminum tube substrate to obtain a photosensitive drum bottom coating with a thickness of 2μm and to prepare the photosensitive body 5.

[0038] Example 6

[0039] The difference between Implementation 6 and Example 1 is that 250g of modified titanium dioxide and 50g of silicon dioxide are replaced with 300 parts of silicon dioxide. The other steps are the same to obtain the bottom coating liquid 6, which is then coated on the aluminum tube substrate to obtain a photosensitive drum bottom coating with a thickness of 2μm and to prepare the photosensitive body 6.

[0040] Example 7

[0041] The difference between Example 7 and Example 1 is that the prepared coating liquid is applied to an aluminum tube substrate to obtain a photosensitive drum bottom coating 7 with a thickness of 3μm, and a photosensitive body 7 is prepared.

[0042] Example 8

[0043] The difference between Example 8 and Example 1 is that 250 parts of modified titanium dioxide and 50 parts of silicon dioxide are replaced with 300 parts of modified titanium dioxide. The remaining steps are the same to prepare coating solution 8, and photoreceptor 8 is prepared.

[0044] Example 9

[0045] The difference between Example 9 and Example 1 is that the prepared coating liquid is applied to an aluminum tube substrate to obtain a photosensitive drum bottom coating 9 with a thickness of 3μm, and a photosensitive body 9 is prepared.

[0046] The photoreceptors 1-9 obtained in Examples 1-9 were tested using an electrical performance tester to measure their residual potential VL and a withstand voltage tester to measure their insulation breakdown time. The results are shown in Table 1. Another photosensitive drum substrate coating remaining from Examples 1-9 was used to test the insulation resistance of the substrate coating and the surface roughness of the coating. The results are shown in Table 2.

[0047] Table 1

[0048] Photoreceptor VL(V) Breakdown time (min) Photoreceptor 1 -75 25 Photoreceptor 2 -78 28 Photoreceptor 3 -85 30 Photoreceptor 4 -90 30 Photoreceptor 5 -97 31 Photoreceptor 6 -100 30 Photoreceptor 7 -83 No breakdown occurred Photoreceptor 8 -65 19 Photoreceptor 9 -71 25

[0049] As shown in Table 1, adding a small amount of silica significantly prolongs the breakdown time. With increasing silica content, the breakdown resistance of the photoreceptor gradually increases, reaching its optimal level at 250g. Further increasing the silica content leads to a significant increase in the breakdown volume (VL), but also deteriorates the electrical properties of the photosensitive drum. Simultaneously, the breakdown resistance of the photosensitive drum increases with increasing undercoat thickness.

[0050] Table 2

[0051] base coat Insulation resistance (Ω) Roughness (μm) Base coat 1 0.25M 0.28 Base coat 2 0.30M 0.23 Base coat 3 0.34M 0.21 Base coat 4 0.38M 0.18 Base coat 5 0.40M 0.15 Base coat 6 0.40M 0.12 Base coat 7 0.45M 0.26 Base coating 8 0.18M 0.30 Base coating 9 0.25M 0.30

[0052] As shown in Table 2, with the increase of silicon oxide content, the insulation resistance of the base coating increases, while its surface roughness decreases. Combining the results of Tables 1 and 2, the following conclusions can be drawn: adding a certain amount of silicon oxide to the base coating of the photosensitive drum can effectively reduce its roughness. A smooth surface reduces local electric field concentration caused by microscopic protrusions or depressions, thereby reducing the risk of charge leakage or breakdown, enhancing stability under high voltage conditions, and increasing the thickness of the base coating can increase its insulation resistance, further enhancing the photosensitive drum's breakdown resistance.

Claims

1. A base coating for improving the puncture resistance of a photosensitive drum, characterized in that, The composition and weight parts are as follows: catalyst 1-5 parts, dispersant 3-10 parts, coupling agent 5-15 parts, crosslinking agent 50-100 parts, resin 250-300 parts, oxide 300-600 parts, organic solvent 600-1000 parts. The catalyst is one or more of the following: quaternary ammonium salt, quaternary phosphorus salt, imidazole and its derivatives, organometallic complexes, methanesulfonic acid, and amine-blocked sulfonic acid; The dispersant is one or more of polydimethylsiloxane, polyether-modified silicone oil, amino-modified silicone oil, and fluorosilicone compounds; The coupling agent is one or more of aminosilane, epoxysilane, methacryloxysilane, phthalate, and aluminate. The crosslinking agent is ethylenediamine or hexamethylenediamine; The resin is one or more of polyester resin, polyamide resin, polyurethane resin, and epoxy resin; The oxide may be one or more of aluminum oxide, titanium oxide, silicon oxide, and zinc oxide; The solvent is one or more of methanol, propanol, and toluene.

2. The base coating for improving the puncture resistance of a photosensitive drum according to claim 1, characterized in that, The oxide is silicon oxide.