• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.3
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• pp.310-321
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• 2019

Objectives: The purpose of this study was to investigate types and characteristics of chemical substances used in LCD(Liquid crystal display) panel manufacturing process. Methods: The LCD panel manufacturing process is divided into the fabrication(fab) process and module process. The use of chemical substances by process was investigated at four fab processes and two module processes at two domestic TFT-LCD(Thin film transistor-Liquid crystal display) panel manufacturing sites. Results: LCD panels are manufactured through various unit processes such as sputtering, chemical vapor deposition(CVD), etching, and photolithography, and a range of chemicals are used in each process. Metal target materials including copper, aluminum, and indium tin oxide are used in the sputtering process, and gaseous materials such as phosphine, silane, and chlorine are used in CVD and dry etching processes. Inorganic acids such as hydrofluoric acid, nitric acid and sulfuric acid are used in wet etching process, and photoresist and developer are used in photolithography process. Chemical substances for the alignment of liquid crystal, such as polyimides, liquid crystals, and sealants are used in a liquid crystal process. Adhesives and hardeners for adhesion of driver IC and printed circuit board(PCB) to the LCD panel are used in the module process. Conclusions: LCD panels are produced through dozens of unit processes using various types of chemical substances in clean room facilities. Hazardous substances such as organic solvents, reactive gases, irritants, and toxic substances are used in the manufacturing processes, but periodic workplace monitoring applies only to certain chemical substances by law. Therefore, efforts should be made to minimize worker exposure to chemical substances used in LCD panel manufacturing process.

• Korean Journal of Materials Research
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• v.32 no.12
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• pp.522-527
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• 2022

Among efforts to improve techniques for the chemical vapor deposition of large-area and high-quality graphene films on transition metal substrates, being able to reliably transfer these atomistic membranes onto the desired substrate is a critical step for various practical uses, such as graphene-based electronic and photonic devices. However, the most used approach, the wet etching transfer process based on the complete etching of metal substrates, remains a great challenge. This is mainly due to the inevitable damage to the graphene, unintentional contamination of the graphene layer, and increased production cost and time. Here, we report the systematic study of an H₂ bubbling-assisted transfer technique for graphene films grown on Cu foils, which is nondestructive not only to the graphene film but also to the Cu substrate. Also, we demonstrate the origin of the graphene film tearing phenomenon induced by this H₂ bubbling-assisted transfer process. This study reveals that inherent features are produced by rolling Cu foil, which cause a saw-like corrugation in the poly(methyl methacrylate) (PMMA)/graphene stack when it is transferred onto the target substrate after the Cu foil is dissolved. During the PMMA removal stage, the graphene tearing mainly appears at the apexes of the corrugated PMMA/graphene stack, due to weak adhesion to the target substrate. To address this, we have developed a modified heat-press-assisted transfer technique that has much better control of both tearing and the formation of residues in the transferred graphene films.

• Restorative Dentistry and Endodontics
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• v.34 no.1
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• pp.42-50
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• 2009

Deterioration of long-term dentin adhesion durability is thought to occur by hydrolytic degradation within hydrophilic domains of the adhesive and hybrid layers. This study investigated the hypothesis that priming the collagen network with an organic solvent displace water without collapse and thereby obtain good bond strength with an adhesive made of hydrophobic monomers and organic solvents. Three experimental adhesives were prepared by dissolving two hydrophobic monomers, bisphenol-A-glycidylmethacrylate (Bis-GMA) and triethyleneglycol dimethacrylate (TEGDMA), into acetone, ethanol or methanol. After an etching and rinsing procedure, the adhesives were applied onto either wet dentin surfaces (wet bonding) or dentin surfaces primed with the same solvent (solvent-primed bonding). Microtensile bond strength (MTBS) was measured at 48 hrs, 1 month and after 10,000 times of thermocycles. The bonded interfaces were evaluated using a scanning electron microscope (SEM). Regardless of bonding protocols, well-developed hybrid layers were observed at the bonded interface in most specimens. The highest mean MTBS was observed in the adhesive containing ethanol at 48 hrs. With solvent-primed bonding, increased MTBS tendencies were seen with thermo cycling in the adhesives containing ethanol or methanol. However, in the case of wet bonding, no increase in MTBS was observed with aging.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.125-132
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• 2006

Recently, surface finishing and protection materials were developed to restore performance of the deteriorated concrete and inhibiting corrosion of the reinforcing-bar. For this purpose, surface protection agent as well as coatings are used. Coatings have the advantage of low Permeability of $CO_2,\;SO_2$ and water. However, for coatings such as epoxy, urethane and acryl, long-term adhesive strength is reduced and the formed membrane of those is blistered by various causes. Also when organic coatings are applied to the wet surface of concrete, those have a problem with adhesion. On the other hand, surface protection agent penetrates into pore structure in concrete through capillary and cm make a dense micro structure in concrete as a result of filling effect. Furthermore, the chemical reaction between silicate from surface protection agent and cement hydrates can also make a additional hydration product which is ideally compatible with concrete body. The aim of this study is to examine the effect of penetrative surface protection agent(SPA) by evaluating several concrete durability characteristics. The results show that the concrete penetrated surface protection agent exhibited higher durability characteristics for instance, carbonation velocity coefficient, resistance to chemical attack and chloride ion penetration than the plain concrete. These results due to formation of a discontinuous macro-pore system which inhibits deterioration factors of concrete by changed the pore structure(porosity and pore size distributions) of the concrete penetrated surface protection agent.

• Journal of the Korean Wood Science and Technology
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• v.16 no.4
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• pp.48-53
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• 1988

This study was carried out to investigate the effects of pressing time and spreading amount, moisture content, gap-distance with butt to butt joint and adhesives on bonding strength in manufacturing the laminated wood with Pitch pine (Pinus rigida). The results obtained were as follows: 1) The pressing time of 12 hours, 10 kilogram per square centimeter of pressure and 200 gram per square meter of spreading amount were required to reach over 50 kilogram per square centimeter (block shear strength) in manufacturing the laminated wood by aqueous vinyl urethane adhesive. 2) The bonding strength decreased with the increase of moisture content of wood. The block shear strength, however, showed over 100 kilogram per square centimeter when the strength test was carried out after air-drying the laminated wood in high moisture content (30-70%). 3) Regardless of direction of load, every flexural property decreased with the increase of gap-distance with butt to butt joint. However, little of every flexural property was changed at 0.5 millimeter of joint-gap distance. The flexural property of vertically laminated wood (perpendicular to glue line to load direction: 1) showed more than that of horizontally laminated wood (parallel to glue line to load direction: //). 4) Among five adhesives used at this experiment, the bonding strength of aqueous vinyl urethane adhesive was the highest in dry bond and wet tests.

• Korean Journal of Materials Research
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• v.9 no.9
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• pp.926-931
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• 1999

The microstructure, wettability, shear strength and aging effect of Sn-3.5Ag/Cu and Alloy42 lead-frame solder joints were measured for comparison. In the case of Sn-3.5Ag/Cu, $Ag_3Sn and Cu_6Sn_5$ phases in the matrix Sn and $1~2\mu\textrm{m}$ thick $Cu_6Sn_5$ phase at the interface of solder/lead-frame were formed. In the case of Sn-3.5Agl Alloy42, only AgJSn phase of low density in the matrix Sn and $0.5~1.5\mu\textrm{m}$ thick $FeSn_2$, phase at the interface of solder/leadframe were formed. Comparing to Cu, Alloy42 showed wider area of spread and smaller contact angle, thus better wet­tability. But shear strength and ductility of Alloy 42 solder joints were only 33% and 75% of those of Cu, respectively After aging at $180^{\circ}C$ for 1 week, $\xi-Cu_3Sn$ layer on $\eta-Cu_6Sn_5$ layer was formed on Cu lead-frame, while coarsened cir­cular $Ag_3Sn$ phase in the matrix and thickened $FeSn_2$, at the interface were formed on Alloy42 lead- frame.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.23-31
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• 2004

Normally, coating is used for protecting reinforced concrete. For this purpose, both organic and inorganic coatings are used. The advantages of inorganic coatings are lower absorption of UV, non-burning etc. On the other hand, organic coatings have the advantage of low permeability of $CO_2, SO_2$ and water. Organic coatings provide better protection for reinforced concrete. However, organic coatings such as epoxy, urethane and acryl reduce long-term adhesive strength by the difference of their thermal expansion coefficients and elastic modules from those of concrete, and the formed coating cover of these is blistered by poor breathing. Also, when organic coatings are applied to the wet surface of concrete, they have a problem with adhesion. In this study, a new coating material for protecting concrete was hybridized with polymer and ceramics. And tests were carried out on its physical and durable characteristics, and safety characteristic on elution. All results were compared with organic coating materials and epoxies and showed that the performance of the developed coating material was not inferior to that of other organic coatings in protecting concrete. On the other hand, safety characteristic on elution was superior to epoxies which were used in this study. So, the developed coating material was considered as a suitable protecting coating material which have advantages of inorganic and organic coatings for protecting underground concrete structures, especially in contact with water.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.2
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• pp.157-169
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• 2009

The aim of this study was to evaluate effect of implant abutment screw coating treatment on joint stability, investigating mechanical properties of these. For this study used $ExFeel^{(R)}$ external hexed implant system and $15mm{\times}1mm$ discs. Experimental group was $1{\mu}m$ TiN, TiCN, TiC coated abutment screws and discs. To know mechanical property, i evaluated adhesion strength, surface hardness, using disc, corrosion test using screw. The results were as follows : rotation angle of coated screws increased than that of non-coated screw because of lower friction coefficient, especially TiC coated screw group had the largest value, but removal torque decreased in all coated screws (p<0.05). Torque loss before and after fatigue test was the smallest in TiC-coated screws, and the largest in non-coated screws (p<0.05), and there was no statistically significant difference between dry condition and wet condition of screws because of higher surface hardness and lower friction coefficient. From the above results, TiN, TiCN, TiC coating group had high abrasion resistance, especially TiC coated group which had low torque-consuming, high rotation angle as low friction coefficient will be considered to influence on implant abutment screw joint stability positively.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.1
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• pp.39-47
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• 2007

It is investigated how KOH and Rthylenediamine(EDA) treatment conditions on Polyimide film surface affect the interfacial fracture energy between electroless plated Ni and Polyimide film by $180^{\circ}$ peel test. Estimated values of interfacial fracture energy were 24.5 g/mm and 33.3 g/mm for the KOH treatment times under 1 and 5 minutes, respectively, while, those were 31.6 g/mm and 22.3 g/mm for EDA treatment times under 1 and 5 minutes, respectively. Interfacial bonding between electroless plated Ni and Polyimide seems to be dominated by chemical bonding effect rather than mechanical interlocking effect. It is found that chemical treatment produces carboxyl and mine functional groups which are closely related the interfacial bonding mechanism. Finally, it is speculated that interfacial fracture energy seems to be controlled by O=C-O bonding near cohesive failure region.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.379-387
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• 2016

In this study, a survey was conducted on the required measurement and waterproofing performance for residential building underground structure leakage prevention system. According to the results of the survey, it has been determined that leakage problem is considered to be quite severe, and many respondents have agreed. The legal guidelines and regulation systems do not reflect properly on the environmental requirements or conditions, resulting in continued leakage problem. In regards to this, a standardized waterproofing technique that can be used in underground areas of residential structures is required as an obligation and the development of high performance waterproofing method that allows for wet concrete surface adhesion and a guideline, design and maintenance method that allows the control of overall situational control of leakage is required.