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Improvement on the qualities of photosensitive members with cold sealing
Surface and Coatings Technology 169 – 170 (2003) 592–594
Improvement on the qualities of photosensitive members with cold sealing Jin Young Kim*, Yong Sun Won, Chang Hyun Kim, Ji Chul Yoo, Hee Taek Yum R&D Center, Samsung Electro-Mechanics, Suwon, Kyounggi-do 442-743, South Korea
Abstract Organic photo-conductor (OPC) drum used in a laser printer comprises photosensitive substrates including an anodized layer formed on the surface of an aluminum or aluminum alloy base. Hot sealing method has been dominantly used to seal the pores of anodized aluminum of OPC drum. Cold sealing procedure has been applied to enhance the sealing quality of OPC drum and the result showed that cold sealing method is more effective than hot sealing when the pore size is extremely small. As a result, defects such as spots on the printed images, smudges and cracks on the surface of OPC drum have been removed. Adhesion strength between photosensitive layers and the surface of anodized aluminum has greatly increased with improvement of sealing quality. 䊚 2003 Elsevier Science B.V. All rights reserved. Keywords: Hot sealing; Cold sealing; Organic photo-conductor drum; Anodized aluminum
1. Introduction Organic photo-conductor (OPC) drum is one of the main components of a laser printer. The image is generated by the laser beam which reaches on the lightsensitive drum as the pattern of an electric charge. The toner particles adhere to this pattern after the drum has brushed against the developing roller w1x (Fig. 1). OPC drum is comprised of several photosensitive layers including a charge generating layer and a charge transporting layer which coat the surface of anodized aluminum substrate. The anodized aluminum layer has porous structure containing columnar hexagonal cells consisting of central pores 30 nm in diameter. Sealing of the pores formed in the surface of OPC drum has been dominantly accomplished by immersion in boiling water, procedure known as ‘hydrothermal sealing or hot sealing’ w2–5x. While hot sealing method with nickel acetate bath was adopted, defects such as dots on the printed images, smudges and cracks on the surface of anodized aluminum were reported from both the sides of manufacturers and users of OPC drum. Since poor quality of sealing can be an origin of these defects, cold sealing using a *Corresponding author. Tel.: q82-31-210-6397; fax: q82-31-2103324. E-mail address: [email protected] (J.Y. Kim).
nickel fluoride bath has been newly adopted to improve the quality of sealing. In spite of its economical advantages cold sealing has not been commonly used in OPC drum with several difficulties related to the characteristics of printed images. Improvement on the sealing quality after using cold sealing method and investigation on the sealing mechanism has been discussed. 2. Experiments Sealing conditions are described as follows: ● Hot sealing: 0.5 gyl of nickel acetate, 85 8C and 7 min. ● Cold sealing: 0.5 gyl of nickel fluoride, additives less than 0.5 gyl, room temperature and 7 min. Sealing conditions were analyzed by FE-SEM (Hitachi S-4700) equipped with EDS (Noran Vantage). FTIR (Bio-Rad, FTS 65A) and IC (Dionex DX-500) are used to analyze the composition of sealants. 3. Results and discussion In hot sealing using nickel acetate bath, aluminum oxide on the wall of pores is transformed into bohemite
0257-8972/03/$ - see front matter 䊚 2003 Elsevier Science B.V. All rights reserved. PII: S 0 2 5 7 - 8 9 7 2 Ž 0 3 . 0 0 1 2 2 - 1
J.Y. Kim et al. / Surface and Coatings Technology 169 – 170 (2003) 592–594
593
Fig. 1. A schematic of a laser printer. Fig. 3. Defects found in OPC drum.
which is formed at the temperature of above 80 8C. The basic reaction in a hot sealing process can be expressed by w3x Al2O3qH2O™2AlO(OH); bohemite This conversion results in the volume expansion and closing of porosity. The bohemite can be formed at temperature above 80 8C and it exhibits the corrosion preventing effect for aluminum w5x. The supply of water by diffusion process has to be continued for this transformation to occur in the lower area of the pores. However, diffusion process of H2O towards the anodic oxide is not easy, especially, when the pore size is small, resulting in poor sealing. Fig. 2 shows the surface of imperfectly sealed anodized aluminum layer after hot sealing. As the sealing has not been thoroughly done, various kinds of defects such as black spots (or white ones, in a reversed development system), smudges and cracks on the surface of anodized layer have occurred. Direct charge injection from the aluminum substrate passed
Fig. 2. The surface of imperfectly sealed anodized aluminum layer.
through the unsealed pores originates the undesirable spots on the printed images. Cracks can be generated on the surface of aluminum oxide during the storage due to the expansion of air filled in pores as the temperature rises (Fig. 3). Cold sealing procedure based on nickel fluoride solutions has fostered since the 1980s w6–8x. The mechanism of cold sealing has not become well understood so far. A possible scheme of the cold nickel fluoride sealing is suggested w6x. Al2O3q6Fyq3H2O™2AlF3q6OHy Niq2q2OHy™Ni(OH)2 Al2O3q3H2O™2Al(OH)3 These reactions are synergistic, leading to coprecipitates within the micropores and eventually blocking the pores. EDS analysis of the cross-section of the pores confirms that nickel hydroxide seals the pore (Fig. 4). The problem of continuous growing of hydroxide has been solved by the use of endcapping agent. Additionally, an amine type of organic additive is used to facilitate penetrating of sealant into the pores. As a
Fig. 4. Proposed schematic of plugged pores after cold sealing.
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J.Y. Kim et al. / Surface and Coatings Technology 169 – 170 (2003) 592–594
4. Conclusion Cold sealing method using a nickel fluoride has been adopted to seal the anodized aluminum of OPC drum. The pores were thoroughly impregnated with nickel hydroxide in the cold sealing method. Special additives have been used to stop further formation of hydroxides and to facilitate the sealing process. As a result, previously reported defects such as spots on the printed images, cracks and smudges on the surface of aluminum oxide have been terminated. In addition, adhesion strength has increased more than five times with the improvement on the sealing quality. Fig. 5. The surface of anodized aluminum after (a) hot sealing and (b) cold sealing.
result, spots and smudges have not generated anymore. High quality of cold sealing has come to be proved good in the prevention of cracks. Moreover, a remarkable improvement of the adhesion strength between the photosensitive layer and the anodized layer, an unexpected outcome, was achieved. Evaluation of adhesion showed that adhesion strength increased more than five times after the new sealing method was adopted (Fig. 5).
References w1x Available from http:yywww.epson.deyenqyaboutylaser. w2x S. Wernick, The Surface Treatment and Finishing of Aluminum and its Alloys, fifth ed. w3x K. Wefers, Aluminum 8 (1973) 553–561. w4x K. Wefers, Aluminum 9 (1973) 622–624. w5x R.C. Spooner, Metal Finish. December (1968) 44–49. w6x B. Racel Cheng, L. Hao, Metal Finish. May (2000) 48–55. w7x J.A. Gonzalez, S. Feliu Jr., J. Appl. Electrochem. 29 (1999) 845–854. w8x C. Liden, Contact Dermatitis 31 (1994) 22–24.
Improvement on the qualities of photosensitive members with cold sealing Jin Young Kim*, Yong Sun Won, Chang Hyun Kim, Ji Chul Yoo, Hee Taek Yum R&D Center, Samsung Electro-Mechanics, Suwon, Kyounggi-do 442-743, South Korea
Abstract Organic photo-conductor (OPC) drum used in a laser printer comprises photosensitive substrates including an anodized layer formed on the surface of an aluminum or aluminum alloy base. Hot sealing method has been dominantly used to seal the pores of anodized aluminum of OPC drum. Cold sealing procedure has been applied to enhance the sealing quality of OPC drum and the result showed that cold sealing method is more effective than hot sealing when the pore size is extremely small. As a result, defects such as spots on the printed images, smudges and cracks on the surface of OPC drum have been removed. Adhesion strength between photosensitive layers and the surface of anodized aluminum has greatly increased with improvement of sealing quality. 䊚 2003 Elsevier Science B.V. All rights reserved. Keywords: Hot sealing; Cold sealing; Organic photo-conductor drum; Anodized aluminum
1. Introduction Organic photo-conductor (OPC) drum is one of the main components of a laser printer. The image is generated by the laser beam which reaches on the lightsensitive drum as the pattern of an electric charge. The toner particles adhere to this pattern after the drum has brushed against the developing roller w1x (Fig. 1). OPC drum is comprised of several photosensitive layers including a charge generating layer and a charge transporting layer which coat the surface of anodized aluminum substrate. The anodized aluminum layer has porous structure containing columnar hexagonal cells consisting of central pores 30 nm in diameter. Sealing of the pores formed in the surface of OPC drum has been dominantly accomplished by immersion in boiling water, procedure known as ‘hydrothermal sealing or hot sealing’ w2–5x. While hot sealing method with nickel acetate bath was adopted, defects such as dots on the printed images, smudges and cracks on the surface of anodized aluminum were reported from both the sides of manufacturers and users of OPC drum. Since poor quality of sealing can be an origin of these defects, cold sealing using a *Corresponding author. Tel.: q82-31-210-6397; fax: q82-31-2103324. E-mail address: [email protected] (J.Y. Kim).
nickel fluoride bath has been newly adopted to improve the quality of sealing. In spite of its economical advantages cold sealing has not been commonly used in OPC drum with several difficulties related to the characteristics of printed images. Improvement on the sealing quality after using cold sealing method and investigation on the sealing mechanism has been discussed. 2. Experiments Sealing conditions are described as follows: ● Hot sealing: 0.5 gyl of nickel acetate, 85 8C and 7 min. ● Cold sealing: 0.5 gyl of nickel fluoride, additives less than 0.5 gyl, room temperature and 7 min. Sealing conditions were analyzed by FE-SEM (Hitachi S-4700) equipped with EDS (Noran Vantage). FTIR (Bio-Rad, FTS 65A) and IC (Dionex DX-500) are used to analyze the composition of sealants. 3. Results and discussion In hot sealing using nickel acetate bath, aluminum oxide on the wall of pores is transformed into bohemite
0257-8972/03/$ - see front matter 䊚 2003 Elsevier Science B.V. All rights reserved. PII: S 0 2 5 7 - 8 9 7 2 Ž 0 3 . 0 0 1 2 2 - 1
J.Y. Kim et al. / Surface and Coatings Technology 169 – 170 (2003) 592–594
593
Fig. 1. A schematic of a laser printer. Fig. 3. Defects found in OPC drum.
which is formed at the temperature of above 80 8C. The basic reaction in a hot sealing process can be expressed by w3x Al2O3qH2O™2AlO(OH); bohemite This conversion results in the volume expansion and closing of porosity. The bohemite can be formed at temperature above 80 8C and it exhibits the corrosion preventing effect for aluminum w5x. The supply of water by diffusion process has to be continued for this transformation to occur in the lower area of the pores. However, diffusion process of H2O towards the anodic oxide is not easy, especially, when the pore size is small, resulting in poor sealing. Fig. 2 shows the surface of imperfectly sealed anodized aluminum layer after hot sealing. As the sealing has not been thoroughly done, various kinds of defects such as black spots (or white ones, in a reversed development system), smudges and cracks on the surface of anodized layer have occurred. Direct charge injection from the aluminum substrate passed
Fig. 2. The surface of imperfectly sealed anodized aluminum layer.
through the unsealed pores originates the undesirable spots on the printed images. Cracks can be generated on the surface of aluminum oxide during the storage due to the expansion of air filled in pores as the temperature rises (Fig. 3). Cold sealing procedure based on nickel fluoride solutions has fostered since the 1980s w6–8x. The mechanism of cold sealing has not become well understood so far. A possible scheme of the cold nickel fluoride sealing is suggested w6x. Al2O3q6Fyq3H2O™2AlF3q6OHy Niq2q2OHy™Ni(OH)2 Al2O3q3H2O™2Al(OH)3 These reactions are synergistic, leading to coprecipitates within the micropores and eventually blocking the pores. EDS analysis of the cross-section of the pores confirms that nickel hydroxide seals the pore (Fig. 4). The problem of continuous growing of hydroxide has been solved by the use of endcapping agent. Additionally, an amine type of organic additive is used to facilitate penetrating of sealant into the pores. As a
Fig. 4. Proposed schematic of plugged pores after cold sealing.
594
J.Y. Kim et al. / Surface and Coatings Technology 169 – 170 (2003) 592–594
4. Conclusion Cold sealing method using a nickel fluoride has been adopted to seal the anodized aluminum of OPC drum. The pores were thoroughly impregnated with nickel hydroxide in the cold sealing method. Special additives have been used to stop further formation of hydroxides and to facilitate the sealing process. As a result, previously reported defects such as spots on the printed images, cracks and smudges on the surface of aluminum oxide have been terminated. In addition, adhesion strength has increased more than five times with the improvement on the sealing quality. Fig. 5. The surface of anodized aluminum after (a) hot sealing and (b) cold sealing.
result, spots and smudges have not generated anymore. High quality of cold sealing has come to be proved good in the prevention of cracks. Moreover, a remarkable improvement of the adhesion strength between the photosensitive layer and the anodized layer, an unexpected outcome, was achieved. Evaluation of adhesion showed that adhesion strength increased more than five times after the new sealing method was adopted (Fig. 5).
References w1x Available from http:yywww.epson.deyenqyaboutylaser. w2x S. Wernick, The Surface Treatment and Finishing of Aluminum and its Alloys, fifth ed. w3x K. Wefers, Aluminum 8 (1973) 553–561. w4x K. Wefers, Aluminum 9 (1973) 622–624. w5x R.C. Spooner, Metal Finish. December (1968) 44–49. w6x B. Racel Cheng, L. Hao, Metal Finish. May (2000) 48–55. w7x J.A. Gonzalez, S. Feliu Jr., J. Appl. Electrochem. 29 (1999) 845–854. w8x C. Liden, Contact Dermatitis 31 (1994) 22–24.