2019 AUG 14 (NewsRx) -- By a News Reporter-Staff News Editor at South Korea Daily Report -- According to news reporting originating from Alexandria, Virginia, by NewsRx journalists, a patent by the inventor Shin, Bu-Gon (Daejeon, South Korea), filed on May 1, 2014, was published online on August 12, 2019.
The assignee for this patent, patent number 10,364,179, is LG Chem Ltd. (Seoul, South Korea).
Reporters obtained the following quote from the background information supplied by the inventors: “Field of the Invention
“The present invention relates to a method for manufacturing a glass cliche using laser etching and an apparatus for laser irradiation therefor, and more particularly to a method for manufacturing a glass cliche using the phenomenon that an etching speed of glass is relatively increased only in a portion to which laser is irradiated.
“Description of the Related Art
“To produce a flat panel display (FPD) such as a liquid crystal display (LCD) and a plasma display panel (PDP), various kinds of patterning processes for making electrodes, black matrix, color filters, separators, thin film transistors and so on are required.
“In a general case, a photoresist is selectively removed using a photo mask by exposing and developing to make a photoresist pattern, and then the photoresist pattern is used for the patterning process. This patterning process using a photo mask uses a lot of materials such as photoresist and developing agent and also needs an expensive photo mask, which results in many processing steps or long processing time.
“To solve this problem, there have been proposed various methods for printing a pattern-forming material directly such as ink jet printing or laser transcription, without using photoresist. As one of such methods, there is an offset printing in which a patterned material is transcribed to a blanket using a cliche and then the pattern of the blanket is transcribed onto a cliche.
“The offset printing using a cliche ensures smaller material consumption and simpler process than a conventional method using photoresist and also ensures faster process speed than ink-jet printing or laser transcription. However, the offset printing needs cliches independently for substrates with different patterns, and a cliche generally made of glass is manufactured complicatedly and very expensive.
“A general method for making the glass cliche is explained with reference to FIG. 1. A photoresist 102 is applied onto a glass cliche 101 by means of spin coating, dip coating, spray coating, slit coating, bar coating or the like, as shown in FIG. 1(a).
“After that, a photo mask 103 is used to form a desired pattern as shown in FIG. 1(b) by means of exposure and development phenomena. During the exposure process, the photoresist 102 is selectively photo-sensitized by UV rays 104 passing through the photo mask 103 in which a desired pattern is already formed, and a pattern 105 is formed on the glass cliche as shown in FIG. 1© due to the difference of solubility for a developing solution between the photo-sensitized region and the non-sensitized region.
“FIG. 1© shows the case adopting a positive photoresist, but a negative photoresist may also be used. In case the negative photoresist is used, a region irradiated by UV rays 104 remains but a region not photo-sensitized by UV rays is removed.
“The glass cliche having the pattern of the photoresist 102 formed therein is dipped in a glass etching solution (not shown) as shown in FIG. 1(d), and then glass etching reaction occurs partially only on a region 106 where a glass cliche is exposed. Generally, an etching reaction of an amorphous material such as glass becomes an isotropic etching without no orientation, so an etching speed is identical in both depth and width directions of the glass.
“Thus, as the etching reaction occurs, a glass etching region 106 becomes wider than the width of the pattern of the photoresist 102, and a bottom portion of the etching portion has a rounded shape, as shown in FIG. 1(d). As the etching work progresses, the etching continuously occurs in depth and width directions as shown in FIG. 1(e), so a width 107 of the etched glass cliche becomes gradually wider than the pattern of the photoresist 102.
“If the etching is completed to a desired depth, the glass cliche is taken out of the etching solution and washed by a distilled water, and then the photoresist is removed to obtain a glass cliche 108 finally etched, as shown in FIG. 1(f).
“In the method of making a glass cliche using such a wet etching, isotropic etching occurs as shown in FIG. 1, so the pattern is etched in its sides as much as the same thickness as the etched depth.
“Thus, the pattern of photoresist used for etching should be formed with at least double margin of a desired etching depth, and due to this reason, there is a limit in precision for the pattern to be formed. Also, considering a room where an etching solution may penetrate, an actually etchable pattern should be three or four times as much as a minimal etching depth, so it is more difficult to form a pattern with fine line widths.
“In addition, due to the nature of isotropic etching, the etching is made in a substantially circular shape between a wall and a bottom to be etched, so an etching depth is gradually varying, which results in deteriorated printing quality. Also, since a photoresist pattern should be formed prior to the etching process, many processes such as an exposure process using a photo mask and a photoresist development process using a developing solution are needed before the etching work, and also a process of removing the remaining photoresist is also added after the etching work is completed.
“In addition to the above wet etching, a dry etching for etching a glass using plasma of an etching gas in a vacuum state is also available. The dry etching for etching a glass cliche using a gas containing fluorine such as CF4 and CF3H allows anisotropic etching, differently from the wet etching, so a line width is not widened or a region between a wall and a bottom is not etched in a circular shape as the dry etching progresses.
“However, a vacuum chamber and an expensive etching gas should be prepared for the dry etching, which increase a cost for the etching work and makes it difficult to apply the etching work to large-scale matters or mass production.
“Also, the drying etching makes an etching mask and an etching material be etched together, so the etching mask should have as slowest etching speed as possible. Generally, a mask layer made of metal such as chrome is used for glass etching, but this mask layer cannot be made too thick, so there is a limit in glass etching depth.
“In addition, the dry etching needs to form a mask pattern prior to etching, similarly to the wet etching, so many processes such as preprocesses for vacuum-deposition of a metal mask layer, formation of a photoresist layer, exposure of the photoresist using a photo mask, development of the photoresist layer to form a pattern, etching of the metal layer used as a mask as well as postprocesses for removal of the metal mask after etching are required.
“In order to solve the above problems in a glass cliche making process using wet etching or dry etching, a new method using laser etching is proposed in the Korean Laid-open Patent Publication No. 10-2007-0000100 or the like.
“The Korean Laid-open Patent Publication No. 10-2007-0000100 discloses a method for making a cliche having a desired pattern by directly etching an insulating substrate with laser. In case a glass cliche is directly etched with laser to make a cliche, there may be advantages in process since an etching solution is not used. However, since the glass is removed by means of photothermolysis on regions irradiated by laser, the used laser should have a high power and an etching speed is relatively slow. Also, it is impossible to prevent generation of HAZ (Heat Affected Zone) that may cause pattern deterioration, and fine cracks may happen in the glass cliche due to thermal impacts caused by continuous irradiation of the laser with strong energy.
“Along with them, since a roll means playing a role of moving a material transcribed to a glass cliche continuously transfers load to the glass cliche, the load may weaken durability of the glass cliche or causes fine cracks in the glass cliche. Also, residuals of pattern material, not moved by the roll means, may remain in a blanket.”
In addition to obtaining background information on this patent, NewsRx editors also obtained the inventor’s summary information for this patent: “The present invention is designed to solve the problems of the prior art, and therefore it is an object of the present invention to provide a method for etching a glass cliche with a high aspect ratio and high work efficiency by means of harmonized use of wet etching and laser etching.
“In addition, another object of the present invention is to provide a method for etching a glass cliche, which may effectively disperse a physical load of a roll means, transferred to a glass cliche, and differentially control a laser irradiation area according to an irradiation time such that a pattern capable of minimizing residuals of a blanket may be formed on the glass cliche.
“Other objects and advantages of the present invention will be explained below and understood from embodiments of the present invention. In addition, the objects and advantages of the present invention may be realized by combinations of components defined in the appended claims.
“In order to accomplish the above object, the present invention provides a method for manufacturing a glass cliche using laser etching, comprising a dipping step for dipping a glass cliche, which will be etched, into an etching solution; a patterning step for irradiating laser to the glass cliche dipped in the etching solution to form a pattern therein; and a washing step for washing the patterned glass cliche.
“Also, in the patterning step, a pattern may be formed by means of a plurality of laser irradiation surfaces applied to the glass cliche. In addition, the pattern formed by the plurality of irradiation surfaces is preferably made using a mask having a laser transmission pattern identical to the pattern to be formed on the glass cliche.
“In the present invention, the patterning step includes an input step for receiving image information of a pattern to be formed; an calculating step for calculating area information of a laser irradiation surface corresponding to the image information; and an irradiating step for irradiating laser having differential irradiation areas according to irradiation time based on the calculation area information to form a pattern.
“In addition, in the irradiating step, a pattern is preferably formed by irradiating laser whose irradiation area is decreased as the irradiation time goes.
“In another aspect of the present invention, there is also provided an apparatus for laser irradiation, which is used for laser etching to form a pattern on a glass cliche dipped in an etching solution by irradiating laser thereto, the apparatus comprising a laser source for irradiating laser; an input unit for receiving shape information of the pattern to be formed; an calculation unit for calculating area information of a laser irradiation surface corresponding to the shape information; and a controller for controlling the laser source to irradiate laser having differential irradiation areas according to irradiation time based on the calculated area information.
“In the apparatus for laser irradiation, the controller preferably controls the laser source to irradiate laser whose irradiation area is decreased as the irradiation time goes.”
The claims supplied by the inventors are:
“What is claimed is:
“1. An apparatus for laser irradiation, which is used for laser etching to form a pattern on a glass cliche dipped in an etching solution by irradiating laser thereto, the apparatus comprising: an irradiating laser beam produced by a movable excimer laser source that is movable in a vertical direction with respect to a cliche surface so that a distance between the movable excimer laser source and the cliche surface can be controlled such that a focus of the irradiating laser beam can be formed at the cliche surface; a focusing lens, the position of which between the laser source and the cliche surface is controlled according to an etched depth as the etching progresses to maintain a focus of the laser beam on the cliche surface at the etched depth; a shadow mask comprising a laser transmission pattern identical to the pattern to be formed on the glass cliche, the pattern forming a plurality of laser irradiation areas on the glass cliche when the irradiating laser beam is transmitted through the pattern of the shadow mask; an input unit comprising an electronic circuit configured for receiving shape information of the pattern to be formed; a calculation unit comprising an electronic circuit configured for calculating area information of a laser irradiation surface corresponding to the shape information; and a controller configured for controlling the movable excimer laser source.
“2. The apparatus for laser irradiation according to claim 1, wherein the controller is configured to control the movable excimer laser source according to an irradiation time based on the calculated area information.
“3. The apparatus for laser irradiation according to claim 1, wherein the movable excimer laser is a KrF laser or an ArF laser.”
For more information, see this patent: Shin, Bu-Gon. Method For Manufacturing Glass Cliche Using Laser Etching And Apparatus For Laser Irradiation Therefor. U.S. Patent Number 10,364,179, filed May 1, 2014, and published online on August 12, 2019. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=10,364,179.PN.&OS=PN/10,364,179RS=PN/10,364,179
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