JP5351364B2 - Cover glass for portable device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a cover glass for a mobile device used for protecting a display screen of a mobile device such as a mobile phone, a smartphone, or a PDA (Personal Digital Assistant), and a method for manufacturing the same.

  In portable devices such as mobile phones, smartphones, and PDAs, a transparent protective plate is disposed outside the display device in order to protect the display device such as a liquid crystal panel. A resin such as acrylic is often used as the protective plate. However, since the protective plate made of resin is easily bent, it is necessary to increase the thickness of the plate or to leave a large gap with the display device. Therefore, cover glasses made of a glass material have begun to spread as protective plates for the above display devices. Since glass has high hardness, there is little deflection and it can contribute to thickness reduction.

  However, since glass has the property of breaking, it is necessary to improve the strength that tends to be insufficient due to the reduction in thickness of the cover glass for portable devices that is required to have high strength. As a technique for improving the strength, it has been proposed to chemically strengthen a glass substrate cut out in the outer shape of a cover glass (chemical strengthening treatment). By this chemical strengthening treatment, by forming an ion exchange layer in which a compressive stress acts on the surface, bending is suppressed and sufficient strength is obtained, so that it is difficult to break.

  In order to perform the above-described chemical strengthening treatment, the glass substrate serving as the cover glass needs to have a composition capable of performing the treatment. Specifically, as the chemical strengthening treatment, an ion exchange treatment is performed in which alkali metal ions in the glass are exchanged with ions having a larger ion radius than the alkali metal ions. Therefore, when performing chemical strengthening, the glass substrate used as the object needs to be the composition containing an alkali metal ion.

  By the way, in general, a cover glass is manufactured by extracting a plurality of glass substrates having an arbitrary shape from a large sheet of glass and processing the extracted glass substrates. Thereby, productivity higher than the case where one cover glass is manufactured one by one is obtained. The glass substrate extracted from the plate-like glass is subjected to a process such as the above-described chemical strengthening process, and then a desired character or pattern is printed on its surface to become a cover glass. For example, in patent document 1, the film which printed the character or the pattern was stuck on the surface of the tempered glass board (glass substrate), or the character or the pattern was baked and painted.

JP 2003-140558 A

  As described above, since the cover glass for portable devices is used for protecting the display screen that is most visually recognized by the user, extremely high quality is required, and the required print pattern must be printed accurately. As a print pattern, in addition to characters and patterns exemplified in Patent Document 1, a frame bordering the periphery of the display area may be printed. In recent years, cover glass for portable devices is required to have a higher level of printing quality, and if a printing defect occurs due to slight ink repelling or the like, it may be a defective product.

  In view of such problems, the present invention has an object to provide a method for manufacturing a cover glass for a portable device that can prevent defective printing and improve the yield.

  When the inventor scrutinized to solve the above problems, it was found that storage from the production of the glass substrate to the printing processing step affects the occurrence of printing defects. During storage, contaminants from the surrounding environment adhere to the glass substrate, foreign substances generated from the packing material move to the glass substrate surface, or alkali metal ions contained in the glass substrate and atmospheric water (humidity). ) And the generation of so-called burn products due to the reaction with carbon dioxide, and so on. Therefore, the inventor diligently studied and thought that it was possible to eliminate printing defects by modifying the surface of the glass substrate that had deteriorated.

  However, printing defects do not occur in all stored glass substrates. Therefore, it is inefficient and causes an increase in manufacturing cost to perform a modification process on all glass substrates. . Therefore, it is preferable to select a glass substrate that may cause problems during the printing process from among the glass substrates, and perform a process of modifying only the glass substrate. For this reason, as a result of further studies, the inventor has surprisingly found that there is a correlation between the contact angle of water on the surface of the glass substrate and poor printing.

  Specifically, even if the glass substrate is stored after finishing the process before the printing process, if the surface state does not change, in other words, if the surface has not changed, If the contact angle of water is almost the same as the contact angle of water when the process is completed, and the surface of the glass substrate is altered during storage, it is considered that the contact angle of water on the surface increases due to the alteration. The inventors have conceived that printing defects can be reduced by managing the water contact angle of the glass substrate in the area to be printed, and the present invention has been completed by further research.

  That is, the typical structure of the manufacturing method of the cover glass for portable devices concerning this invention is a manufacturing method of the cover glass for portable devices including the printing process process which performs a printing process on the surface of the glass substrate containing an alkali metal ion. Then, using the fact that the contact angle of water in the printing region subjected to the printing process in the printing process step on the surface of the glass substrate has a correlation with the print quality on the printed glass substrate, the portable device A printing process step is performed on a glass substrate having a contact angle of water that satisfies the printing quality required for the cover glass.

  In the above configuration, the print processing step is performed only on the glass substrate in which the contact angle of water is in a range satisfying the required print quality by using the above-described correlation. That is, a glass substrate that can be printed favorably and a glass substrate that can cause printing defects are selected based on the contact angle of water, and the printing process is performed only on the glass substrate that can be printed favorably. With this configuration, it is possible to obtain a well-printed cover glass without generating a cover glass that causes defective printing, improve the yield of the cover glass for portable devices, and thus improve the production efficiency, thereby reducing the manufacturing cost. It becomes possible to suppress.

  For the glass substrate having a water contact angle that does not satisfy the print quality required in the cover glass for the portable device, after the adjustment step of adjusting the water contact angle to contact the glass substrate immediately before performing the printing process step, A print processing step may be performed. As described above, the surface of the glass substrate that has been determined to be defective in printing due to the contact angle of water can be modified by the treatment in contact with the acidic solution. Therefore, even such a glass substrate can be subjected to a printing process without any trouble, and a well-printed cover glass can be obtained.

  Another structure of the method for producing a cover glass for a portable device according to the present invention is a method for producing a cover glass for a portable device in which a printing process is performed on the surface of a glass substrate containing alkali metal ions, Print quality required for the cover glass for portable devices by utilizing the correlation between the contact angle of water in the print region of the surface of the substrate and the print quality on the printed glass substrate In order to satisfy the requirements, an adjustment step of adjusting the contact angle of water on the surface of the glass substrate is performed immediately before performing the printing process.

  According to the above configuration, using the correlation between the contact angle of water in the printing region and the print quality in the printed glass substrate, the contact angle of water to the glass substrate before performing the printing process is It can be determined whether or not the print quality required for the cover glass for a portable device is within a range that satisfies the print quality, that is, whether or not there is a possibility that a problem occurs during the printing process on the glass substrate. And based on the correlation, by adjusting the contact angle of water on the glass substrate surface before the printing process, it is possible to prevent printing defects due to the alteration of the glass substrate surface. Therefore, the yield at the time of manufacturing the cover glass for portable devices can be improved.

  After the adjustment step, a print processing step for performing a printing process on the glass substrate surface may be performed. As described above, if the contact angle of water with respect to the glass substrate surface is adjusted in the adjusting step, it is possible to avoid the occurrence of printing defects during the subsequent printing process.

  Said adjustment process is good in making a glass substrate contact an acidic solution. When the contact angle of water does not satisfy the required print quality, in other words, when the glass substrate that has been out of the above range is subjected to such an acid solution, the surface of the glass substrate is modified. Thereby, since the contact angle of a glass substrate falls and it becomes in the range with which the required printing quality is satisfy | filled, it becomes possible to make a glass substrate into the cover glass printed favorably.

  Said glass substrate is good in the glass composition which can be chemically strengthened. Thereby, high intensity | strength can be obtained in a cover glass.

  Moreover, the manufacturing method of the cover glass for portable devices concerning this invention is a manufacturing method of the cover glass for portable devices which consists of a glass substrate containing an alkali metal ion, Comprising: The printing process process which performs a printing process to a glass substrate It includes at least a process of reducing the contact angle of water with respect to the area where the glass substrate is printed immediately before performing the printing process.

  A method for producing a cover glass for a portable device according to the present invention is a method for producing a cover glass for a portable device comprising a glass substrate containing alkali metal ions, and includes at least a printing process step of performing a printing process on the glass substrate. The glass substrate is brought into contact with an acidic solution immediately before performing the printing process.

  According to the said structure, the glass substrate surface is modified by making the glass substrate surface before a printing process process contact an acidic solution, and it becomes possible to adjust the contact angle of water in the range mentioned above. Thereby, since the trouble at the time of the printing process such as ink splashing in the glass substrate whose surface has been modified before the printing process can be solved, the yield of the cover glass for portable devices can be improved.

  A representative configuration of a cover glass for a portable device according to the present invention is a glass composition that can be chemically strengthened, and is a cover glass for a portable device in which printing is performed on at least one of the main surfaces, and the main surface of the glass substrate The contact angle of water in the area where printing is performed is 30 degrees or less.

  In the glass substrate used as the cover glass for portable devices, by setting the contact angle of water in the region where the printing of the main surface is performed within the above range, it is possible to suppress printing defects due to the alteration of the glass substrate surface. . Therefore, the cover glass for portable devices after printing can be made favorable, and the yield at the time of manufacture can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the cover glass for portable devices which can prevent a printing defect and can improve a yield, and its manufacturing method can be provided.

It is an exploded view which shows an example of a portable apparatus provided with the cover glass for portable apparatuses. It is a top view which shows an example of a cover glass and a glass substrate. It is a top view which shows an example of a cover glass and a glass substrate. It is a schematic diagram explaining the contact angle of water in a glass substrate. It is a schematic diagram explaining the contact angle of water in a glass substrate.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  FIG. 1 is an exploded view showing an example of a portable device provided with a cover glass for a portable device. In FIG. 1, a mobile terminal 100 (mobile phone) is shown as an example of the mobile device, but the present invention is not limited to this. A cover glass for a portable device (hereinafter, referred to as a cover glass 120) manufactured by the manufacturing method of this embodiment described in detail later is a portable device such as a PDA, a portable game machine, a portable camera machine, that is, portable. The present invention can be applied to any device. In the present embodiment, an example of the touch panel type mobile terminal 100 is shown, but the display unit and the operation unit may be mobile terminals having different configurations.

  A portable terminal 100 illustrated in FIG. 1 is a touch panel device, and includes a large cover glass 120 that covers the entire front portion of the housing 102. A housing 102 of the portable terminal 100 houses a main substrate 104, a display device such as a liquid crystal panel or an organic EL panel, a speaker 108, a button 110, and the like. A film 112 having a transparent electrode 114 for realizing a touch panel function is disposed inside the cover glass 120 (on the display screen 106 side). A wiring 116 made of a flexible cable is attached to the transparent electrode 114, and the transparent electrode 114 is electrically connected to the main substrate 104 via a connector (not shown). In addition, when using a capacitance-type transparent electrode as the transparent electrode 114, the transparent electrode 114 is arrange | positioned at the surface at the side of the cover glass 120 in the film 112. FIG. On the other hand, when a pressure-sensitive transparent electrode is used as the transparent electrode 114, the transparent electrode 114 is disposed on the surface of the film 112 on the display screen 106 side.

  The cover glass 120 is attached to protect the display screen 106 of the mobile terminal 100. Moreover, the shape of the cover glass 120 is a substantially rectangular shape. A speaker hole 132 is formed at one end of the cover glass 120 in the longitudinal direction. A plurality of button holes 134 are formed at the other end of the cover glass 120 in the longitudinal direction. In the present embodiment, the cover glass 120 that protects the display screen 106 is illustrated, but the cover glass 120 is, for example, a cover glass that protects the lens portion of the camera, a cover glass that protects the casing of the portable device, or the like. It may be.

  2 is a plan view showing an example of the cover glass 120 and the glass substrate, FIG. 2A is a plan view of the cover glass 120 shown in FIG. 1, and FIG. 2B is a plan view of the glass substrate that becomes the cover glass 120 of FIG. 2A. FIG. For easy understanding, the frame coating 122 applied to the cover glass 120 in FIG. 1 is shown in black in FIG. 2A, and the print area 130a to which the frame coating 122 is applied is hatched in FIG. 2B. Show.

  As shown in FIG. 2A, the cover glass 120 has a substantially rectangular plate shape as a whole, and as shown in FIG. 2B, a glass substrate 130 to be the cover glass 120 has substantially the same shape as the cover glass 120. is there. The cover glass 120 is configured by applying a frame coating 122 to a printing region 130a on the outer peripheral portion of the glass substrate 130 illustrated in FIG. The display screen 106 built in the portable terminal 100 has a non-display area at the edge, and a gap is provided between the side surface of the display device and the side wall of the housing 102. Further, the wiring 116 of the transparent electrode 114 is provided on the outer peripheral edge inside the cover glass 120. Here, the frame coating 122 is provided to hide these non-display areas, gaps, wirings, and the like. The frame coating 122 is formed by applying a paint such as black or white.

  As described above, the cover glass 120 protects the display screen 106 most visible to the user in the mobile terminal 100. For this reason, when printing defects such as ink repelling occur in the frame coating 122, the frame coating 122 becomes a defective appearance product. Therefore, the cover glass 120 is required to be in a state where there is no ink repelling when the print region 130a (frame coating 122) on the glass substrate 130 is visually observed, in other words, the print quality is satisfied. It is done. Therefore, an object of the present embodiment is to provide a method for manufacturing a cover glass for a portable device that can prevent defective printing and improve the yield.

  Next, the manufacturing method of the cover glass for portable devices of this embodiment is demonstrated. In such a manufacturing method, first, a glass substrate 130 is formed by dividing a sheet glass (not shown) into pieces. Sheet glass is formed directly from molten glass into a sheet shape, or a glass body molded to a certain thickness is molded to a predetermined thickness, and the main surface is polished to a predetermined thickness. Can be used. In particular, when it is directly molded into a sheet form from molten glass, the main surface of the sheet glass is preferable because it has a surface state free from microcracks. Examples of the method for directly forming a sheet from molten glass include a downdraw method and a float method.

The plate glass is preferably composed of aluminosilicate glass, soda lime glass, borosilicate glass, crystallized glass, or the like. Among _them, it is preferred that the aluminosilicate glass containing _{SiO 2, Al 2 O 3,} Li 2 O and / or Na ₂ O. Al ₂ O ₃ is useful because it improves ion exchange performance in chemical strengthening described later. Li ₂ O is a component for ion exchange with Na + ions in chemical strengthening. Na ₂ O is a component for ion exchange with K + ions in chemical strengthening.

As aluminosilicate glass, the composition _components, SiO 2: 50 to 75 _{wt%, Al} 2 O 3: _{5~20 wt%, Li 2 O, Na 2} O, among the alkali metal oxide selected from _{K 2} O It is preferable that the glass contains at least one kind. Further, the aluminosilicate glass according to the present invention is Na ₂ O: 8 wt% or more, MgO: 6 wt% or less (including 0), CaO: 7 wt% or less (including 0), ZrO 2: 10 wt% or less. It is preferable to contain (including 0).

  That is, the plate-like glass of this embodiment, and by extension, the glass substrate 130 formed by dividing it into individual pieces, is a glass material containing alkali metal ions that can be chemically strengthened. Thus, when the glass substrate 130 has a glass composition that can be chemically strengthened, high strength can be obtained by chemical strengthening. Here, in the glass material containing alkali metal ions, it has been clarified by the inventor's research that depending on the storage state from after chemical strengthening until printing processing, the manufacturing method according to this embodiment If so, the cover glass 120 on which the frame coating 122 is well printed can be manufactured by using the contact angle of water with the glass substrate 130 as will be described later.

  In the present embodiment, the glass substrate 130 is formed by etching. Specifically, a resist pattern is formed on the main surface of the sheet glass, and the glass substrate 130 is cut out and molded by etching with an etchant. By forming in this way by etching, the end surface becomes an etched surface and has very high smoothness, and microcracks that are inevitably generated by machining do not occur, so the high strength required for the cover glass for mobile terminals is high. Can be obtained. Moreover, even a complicated shape difficult to machine can be easily processed.

  The etching method may be either wet etching (wet etching) or dry etching (dry etching). The etchant used for wet etching may be any material that can etch plate glass. For example, an acidic solution containing hydrofluoric acid as a main component or a mixed acid containing at least one of sulfuric acid, nitric acid, hydrochloric acid, and silicic hydrofluoric acid in hydrofluoric acid can be used. The etchant used for the dry etching is not particularly limited as long as it can etch the plate-like glass. For example, a fluorine-based gas can be used.

  In the above description, the case where the glass substrate 130 is formed (divided into pieces) by etching is illustrated, but the present invention is not limited to this, and it is naturally possible to form using other methods such as machining. Is possible. However, when machining is used, micro-cracks tend to occur, and it is preferable to take measures against them.

  Subsequently, the strengthened glass substrate 130 is chemically strengthened by ion exchange treatment. Chemical strengthening is a process of further increasing mechanical strength by forming a compressive stress layer on the glass surface by exchanging ions on the surface of the glass with other ions having a large ionic radius. For chemical strengthening, for example, by using a molten salt such as potassium nitrate or sodium nitrate and performing treatment at a temperature of 300 ° C. to 450 ° C. for 1 hour to 30 hours, Li + ions in the glass are changed to Na + ions in the molten salt, Exchange Na + ions in the glass with K + ions in the molten salt. The compressive stress layer formed by chemical strengthening may be 5 μm or more. The thickness of the compressive stress layer is preferably 50 μm or more, more preferably 100 μm.

  Moreover, as for the alkali metal ion contained in the glass substrate 130 (cover glass 120), the total amount of Li, Na, and K when converted to an oxide is within a range of 12 to 18.5% by weight based on the whole. Good. However, the cover glass having such a composition is likely to be burned due to the chemical strengthening treatment, and thus the surface state is easily changed. Therefore, the present invention is particularly effective.

  In addition, it is preferable to perform chemical strengthening after cutting out the glass substrate 130 like this embodiment. This is because the end surface of the glass substrate 130 is also chemically strengthened, so that it is possible to prevent chipping or cracking when the cover glass 120 (glass substrate 130) is attached to the mobile terminal 100. However, the present invention is not limited to this, and it is possible to perform chemical strengthening in the state of the sheet glass before being singulated.

  After the chemical strengthening is finished, the glass substrate 130 is washed in order to remove the molten salt and other deposits attached to the glass substrate 130. As the cleaning method, a method of washing with a cleaning solution such as water, a dipping method of immersing in the cleaning solution, a scrub cleaning method of contacting a rotating roll body with the glass substrate 130 while flowing the cleaning solution, or the like can be used. The dipping method may be performed in a state where ultrasonic waves are applied to the cleaning liquid.

  The glass substrate 130 that has finished from molding to cleaning after chemical strengthening has a frame coating 122 printed on the surface by the printing process in the printing process to become the cover glass 120. Here, the glass substrate 130 that has been cleaned after chemical strengthening may proceed to the next print processing step as it is, or may proceed to the print processing step after being stored. Among these, there is no problem when the printing process is performed immediately after washing, but when the printing process is performed after storage, the glass substrate 130 is deteriorated on the surface of the glass substrate due to adhesion of contaminants or burns. May cause printing failure.

  Therefore, in this embodiment, in order to satisfy the print quality required for the cover glass 120, the contact angle of water on the surface of the glass substrate 130 is measured immediately before performing the printing process, and the contact angle of water that satisfies the print quality is obtained. A printing process is performed on the glass substrate 130. Moreover, the adjustment process which adjusts the contact angle of water is performed just before performing a printing process process with respect to the glass substrate which has the contact angle of water which does not satisfy print quality. At this time, as described in detail below, the contact angle of water in the printing region 130a (the region where the printing process is performed in the printing process) in the surface of the glass substrate 130 and the printed glass substrate 130 (the cover glass) 120) The fact that there is a correlation with the print quality in 120) is used.

  Here, the contact angle is an angle formed between the solid surface and the tangent of the droplet by the surface tension of the droplet dropped on the solid surface. The contact angle is an index for evaluating the wettability of the liquid droplet on the solid surface. When the contact angle is large, the wettability of the liquid droplet on the solid surface is poor, that is, it tends to be repelled. On the other hand, when the contact angle is small, it can be evaluated that the wettability of the droplet on the solid surface is good, that is, it tends to be difficult to play.

  The glass substrate 130, that is, the cover glass 120, from the molding to the cleaning after chemical strengthening, the frame coating 122 is printed on the surface by the printing process in the printing process. After performing the adjustment process mentioned above, the printing process process which performs a printing process to the printing area | region 130a among the surfaces of the glass substrate 130 is performed. Thereby, the cover glass 120 in which the frame coating 122 is applied to the printing region 130a of the glass substrate 130 is manufactured. As a printing ink, as a resin component, a thermosetting type or a UV curable type containing one or more of epoxy, phenol, polyester, polyimide, polyurethane, polymethyl methacrylate, polyolefin, polyvinyl, polyvinyl butyral, acrylonitrile butadiene styrene Can be used.

  Here, the cover glass 120 that has been cleaned after chemical strengthening may proceed to the next print processing step as it is, while the print processing step may be performed after being stored under various conditions. Among these, there is no problem when the printing process is performed immediately after washing, but when the printing process is performed after storage, the glass substrate 130 is deteriorated on the surface of the glass substrate due to adhesion of contaminants or burns. May cause printing failure.

  Therefore, in the present embodiment, in order to satisfy the print quality required for the cover glass 120, the main surface (in this embodiment, the frame coating 122 is printed on the glass substrate 130 (glass) to be the cover glass 120 is printed. The water contact angle of the main surface on the side having the printing area 130a to be printed is managed. Specifically, the contact angle of water on the main surface is set within a range of 30 degrees or less.

  FIG. 3 is a schematic diagram for explaining the contact angle of water on the glass substrate 130. As a method for measuring the contact angle, a droplet method can be suitably used. As shown in FIG. 3, in this embodiment, the contact angle θ formed by the surface (solid surface) of the printing region 130 a (see FIG. 2B) of the glass substrate 130 and the tangent line 152 of the water drop 150 (droplet) dropped on the surface. Ask for. The measurement was performed according to the JIS R3257 sessile drop method.

  In the glass substrate 130 which is a non-defective cover glass 120 which does not have problems such as ink splashing, that is, satisfies the printing quality, the contact angle θ of water (water droplet 150) is small as shown in FIG. 3A. On the other hand, in the glass substrate 130 of the cover glass 120 in which defects such as ink splash occur and the printing quality is not satisfied and the printing is defective, the contact angle θ of water (water droplet 150) is large as shown in FIG. 3B. . Thus, there is a correlation between the contact angle of water in the printing region of the glass substrate 130 and the print quality. Therefore, if this correlation is utilized, the contact angle θ of the glass substrate 130 before the printing process can be adjusted to a range that can satisfy the printing quality. Therefore, it is possible to prevent defective printing and improve the yield when manufacturing the cover glass.

  In this embodiment, it was made to contact with an acidic solution as an adjustment process which adjusts the contact angle of the water of the surface of the glass substrate 130. FIG. By performing the treatment in contact with the acidic solution, the surface of the glass substrate 130 is modified, the contact angle is lowered, and the printing quality required for the cover glass 120 is satisfied. For this reason, it becomes possible to perform favorable printing on the glass substrate 130.

  In addition, it is preferable that it is just before a printing process as a timing which performs the process (adjustment process) which contacts an acidic solution. In this case, “immediately before” means that there is no other step between the acidic solution treatment (adjustment step) and the printing treatment. Other processes include a cleaning process, a molding process (etching), and a storage process. This is because the contact angle of water on the surface of the glass substrate adjusted by the adjusting process may change again after such other processes.

  After performing the adjustment process mentioned above, the printing process process which performs a printing process to the printing area | region 130a among the surfaces of the glass substrate 130 is performed. Thereby, the cover glass 120 in which the frame coating 122 is applied to the printing region 130a of the glass substrate 130 is manufactured. In this embodiment, since the contact angle θ of water with respect to the surface of the glass substrate 130 is adjusted in the adjustment process, the occurrence of printing defects during the printing process is suppressed, and the frame coating 122 is printed well. Glass 120 can be obtained.

  The printing ink used in the above printing process includes a resin component, heat containing one or more of epoxy, phenol, polyester, polyimide, polyurethane, polymethyl methacrylate, polyolefin, polyvinyl, polyvinyl butyral, acrylonitrile butadiene styrene. A curable type or a UV curable type can be used.

  In the above embodiment, the case where the adjustment process is performed on all the glass substrates 130 before the printing process is illustrated, but the present invention is not limited to this. For example, using the above-described correlation, printing is performed only on the glass substrate 130 having a water contact angle θ that satisfies the print quality required for the cover glass 120 (the water contact angle θ is in a range that satisfies the print quality). Processing steps may be performed.

  In other words, in such a configuration, the above-described correlation is used, and the glass substrate 130 before the printing processing step has a contact angle θ within a range satisfying the print quality required for the cover glass 120 (printable satisfactorily). The substrate 130 and the glass substrate 130 out of the above range (which may cause printing defects) are selected. And a printing process process is performed with respect to the glass substrate 130 which could be printed favorably. Thereby, the cover glass 120 printed favorably can be obtained, without generating the cover glass 120 used as a printing defect.

  On the other hand, if the contact angle θ of the glass substrate 130 before the printing process is not within the range satisfying the print quality required for the cover glass 120 (if the angle does not satisfy the print quality), the glass substrate 130 is left as it is. When the printing process is performed, there is a possibility that the cover glass 120 is a defective print product. Therefore, in the present embodiment, the glass substrate 130 is brought into contact with an acidic solution as an adjustment step, and then a print processing step is performed. Thereby, since the surface of the glass substrate 130 can be modified and the contact angle θ can be set within a range satisfying the printing quality required for the cover glass 120, the printing process can be performed without any trouble. It becomes possible to make the cover glass 120 printed on.

  According to the above configuration, it is possible to determine whether or not printing failure occurs on the glass substrate 130 by using the correlation between the contact angle of water on the glass substrate 130 and the print quality. Therefore, the glass substrate 130 which needs to perform the process (adjustment process) in contact with the acidic solution can be selected. Then, the glass substrate 130 that can be printed satisfactorily is subjected to a printing process as it is, and the glass substrate 130 that may cause a printing failure is subjected to the printing process after the acid solution treatment, thereby improving the yield of the cover glass 120, It is possible to improve production efficiency and thus reduce manufacturing costs.

  In the present embodiment, the cover glass 120 is manufactured by performing the glass substrate 130 in the order of molding (individualization), chemical strengthening, and printing processing. However, the present invention is not limited to this. In the manufacturing process of the cover glass 120, at least the printing process may be performed after chemical strengthening, and the order other than these can be changed as appropriate. For example, the manufacturing process of the cover glass 120 may be performed in the order of chemical strengthening, printing processing, glass substrate molding (single piece), or chemical strengthening, glass substrate forming (single piece), and printing processing. Good.

  As described above, in order to manage the contact angle of water with respect to the cover glass 120 (glass substrate 130), in the manufacturing process of the cover glass 120, the glass substrate 130 may be brought into contact with the acidic solution immediately before performing the printing process. . Thereby, the surface of the glass substrate 130 is modified, and the contact angle of water can be adjusted within the above-described range.

(Example)
Examples of the present invention will be described below, but the present invention is not limited to the following examples. In the following examples, a cover glass was manufactured by sequentially performing (1) a glass substrate shape processing step as a forming step, (2) a chemical strengthening step, and (3) a printing processing step. In Example 1-12 (see Table 1), the relationship between the contact angle of water and the print quality was measured and evaluated.

(1) Glass substrate shape processing step A glass substrate for cover glass was produced by cutting out a predetermined size from a 0.5 mm thick plate glass made of an aluminosilicate gate glass produced by a float process. Glass composition of the aluminosilicate _glass, SiO 2: from 63.5 to 66.5 _{wt%, Al} 2 O 3: _{14.5~17.5 wt%,} Li 2 O: _2~5 wt%, _Na 2 O : 9 to 12% by weight, MgO: 0 to 3% by weight, CaO: 1 to 4% by weight, ZrO2: 0 to 3% by weight, and the total amount of Li, Na and K in terms of oxide is 13 to 16% by weight % Glass for chemical strengthening was used.

  The cutting of the plate glass was performed by etching. That is, a resist was applied to both surfaces of the plate glass, and predetermined exposure and development were performed to form a resist having a resist pattern having a cutting line pattern. Then, using this resist as a mask, wet etching is performed using an etching solution for etching a glass material (for example, an acidic solution containing hydrofluoric acid) to cut into small pieces (10 cm × 5 cm), and the remaining resist is removed and washed. did.

(2) Chemical strengthening process Next, the glass substrate which finished the said shape process was chemically strengthened. Chemical strengthening was performed by heating a chemical strengthening solution in which potassium nitrate and sodium nitrate were mixed to about 380 ° C. and immersing the glass substrate after the shape processing for about 4 hours. The glass substrate after chemical strengthening was sequentially immersed in each washing tank of sulfuric acid, alkaline detergent, pure water, pure water, IPA, and IPA (steam drying), ultrasonically cleaned, and dried.

  The contact angle of water on the glass substrate subjected to the chemical strengthening treatment was measured using a sessile drop method according to JIS R3257. The measurement was carried out at 10 locations on one glass substrate, and the average value was taken as the measured value.

(3) Print processing step Samples with different water contact angles were prepared from the above-mentioned measured products, and the print processing step was performed. In this printing process, a frame coating of a predetermined printing layer (ink layer) was formed by screen printing on the outer peripheral portion (region to be printed) of the glass substrate. As the printing ink, a thermosetting type containing epoxy as a resin component was used.

The print quality of the cover glass after the printing process was visually evaluated. Table 1 shows the measurement and evaluation results of the water contact angle and print quality. The rank of print quality is as follows.
Rank ○: No ink playing Rank ×: Ink playing (small playing part)
Rank XX: Ink is played (the playing part is large)

  Here, flipping is a phenomenon in which a portion that is not printed is generated in a portion that should be printed in the printing region of the cover glass. Rank ○ is a level where there is no problem in print quality for the product. On the other hand, ranks X and XX are levels at which a problem in print quality may occur. When the playing part is small, the rank is X, and when the playing part is large, the rank is XX. Here, the boundary between the size of rank X and rank XX is about 100 um.

  In Table 1, the contact angles of water are about 25 degrees in Example 1-4, about 40 degrees in Example 5-8, and about 50 degrees in Example 9-12, and the print quality ranks are ○, ×, × Since it was x, it turns out that the contact angle of water and print quality have a correlation. The smaller the water contact angle, the higher the print quality. This is presumed that the smaller the water contact angle of the glass substrate, the better the ink adhesion (wetting), and as a result, the ink repelling is suppressed and the print quality is improved.

  Moreover, when the thermosetting ink containing an epoxy is used as a resin component in the glass composition and printing process of this example, it can be seen that the printing quality is good when the contact angle of water is 30 degrees or less.

Also produced by the down-draw method, _SiO a glass composition 2: 62 to 65 _{wt%, Al} 2 O 3: from 12.5 to 15.5 _wt%, Li 2 O: 4.5 to 7.5 wt%, Na ₂ O: 9 to 12% by weight, MgO: 0 to 3% by weight, CaO: 0 to 3% by weight, ZrO2: 4.5 to 7.5% by weight, and Li, Na and K in terms of oxides As a result of conducting a similar experiment using a glass for alumina silicate chemical strengthening containing a total amount of 15 to 18% by weight and using a UV curable ink containing polymethyl methacrylate as a resin component, water was used. There was a correlation between the contact angle and the print quality, and the same results as in Examples 1 to 12 where the print quality was better as the contact angle of water was smaller were obtained. Even in this experiment, when the contact angle of water was lowered to 30 degrees or less, the print quality was at a level with no problem.

  In Example 13-18 (see Table 2), the change in the contact angle of water when the glass substrate was brought into contact with the acidic solution as an adjustment step was examined. Table 2 shows the measurement results of the contact angle of water before and after contact with the acidic solution (adjustment step). In Example 13-18, the contact angle of water was measured in the same manner as in Example 1-12, and glass substrates having different contact angles of water were prepared. Next, after performing the adjustment process which makes the said glass substrate contact an acidic solution, the contact angle of the water of a glass substrate was measured. The acidic solution used in this adjustment process is a sulfuric acid solution. The glass substrate was immersed in and contacted with the sulfuric acid solution under the conditions of a concentration of about 15% by weight, a temperature of about 45 ° C., and an immersion time of about 3 minutes. This acidic solution has a pH ≦ 3. In addition, the measuring method of the contact angle of water and the method of obtaining the measurement value are the same as in Example 1-12.

  Next, the contact angle of water on the glass substrate after the adjusting step was measured, and immediately after that, a printing process was performed to evaluate the printing quality. Table 2 shows the measurement results of the water contact angle before and after contact with the acidic solution (adjustment step) and the evaluation results of the print quality after the adjustment step. The method for measuring the contact angle of water and the method for obtaining the measurement values are the same as in Examples 1-12. Moreover, the printing process and the evaluation of the printing quality were also carried out in the same manner as in Examples 1-12.

  From Table 2, the glass substrate having a water contact angle of about 36 (Example 13) to about 50 degrees (Example 17) becomes about 17 degrees to about 24 degrees by contact with the acidic solution (adjustment process). It can be seen that the contact angle of water is greatly reduced by contact with the acidic solution. In addition, the glass substrate whose water contact angle has exceeded 30 degrees, which is a problem in print quality before coming into contact with an acidic solution, is brought to 30 degrees or less by contacting with an acidic solution, and does not cause a problem in print quality. It can be seen that In addition, although the glass substrate of the contact angle of water equivalent to the said Examples 13-18 was not made to contact acidic solution, but was made to contact with pure water, the contact angle of water did not become 30 degrees or less.

Also produced by the down-draw method, _SiO a glass composition 2: 62 to 65 _{wt%, Al} 2 O 3: from 12.5 to 15.5 _wt%, Li 2 O: 4.5 to 7.5 wt%, Na ₂ O: 9 to 12% by weight, MgO: 0 to 3% by weight, CaO: 0 to 3% by weight, ZrO2: 4.5 to 7.5% by weight, and Li, Na and K in terms of oxides The same experiment was conducted using a UV curable ink containing polymethyl methacrylate as a resin component using alumina silicate chemically strengthened glass containing a total amount of 15 to 18% by weight. The same results as in Examples 13 to 18 in which the treatment with the solution reduces the contact angle of water were obtained. Also in this experiment, the contact angle of water was reduced to 30 degrees or less, and the print quality was at a level with no problem.

From the above, as the glass composition, SiO ₂ : 62 to 66.5 wt%, Al ₂ O ₃ : 12.5 to 17.5 wt%, Li ₂ O: _{2 to} 5.5 wt%, Na ₂ O: 9 to 12% by weight, MgO: 0 to 3% by weight, CaO: 0 to 4% by weight, ZrO2: 0 to 7.5% by weight, and the total amount of Li, Na and K in terms of oxide is 13 to 18% by weight When an aluminosilicate glass containing a resin is printed with a thermosetting or UV curable ink containing epoxy or polymethyl methacrylate as a resin component, there is a correlation between the contact angle of water and the print quality, It can be seen that the smaller the contact angle, the better the print quality, and that the water contact angle is 30 degrees or less and the print quality is at a satisfactory level.

  In the above description, printing defects are reduced by managing the water contact angle of the glass substrate. However, instead of the printing process of the present embodiment, a transparent conductive film such as ITO (indium tin oxide) (or a transparent insulating material film such as SiO2) is formed on the main surface of the glass substrate. You may perform the film-forming process process which performs a process, and the coating process process which performs the coating process of antifouling materials, such as fluorine resin materials, such as a perfluoro polyether compound, with respect to a glass substrate, for example. It is also effective to manage the contact angle of water for the coating treatment of the antifouling material and the film formation treatment of the transparent conductive film. That is, it is possible to reduce the coating failure of the antifouling material and the film formation failure of the transparent conductive film, and to improve the adhesion stability of each functional film to the glass substrate.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  INDUSTRIAL APPLICATION This invention can be utilized for the manufacturing method of the cover glass for portable devices used for protection of the display screen of portable devices, such as a mobile telephone, a smart phone, and PDA (Personal Digital Assistant).

Claims (10)

A method for producing a cover glass for a portable device comprising a printing process step of performing a printing process on the surface of a glass substrate containing an alkali metal ion,
Utilizing that the contact angle of water in the printing region subjected to the printing process in the printing process step of the surface of the glass substrate and the print quality on the printed glass substrate have a correlation,
The manufacturing method of the cover glass for portable devices characterized by performing the said printing process process with respect to the glass substrate which has the contact angle of the water which satisfies the printing quality calculated | required in the said cover glass for portable devices.   For a glass substrate having a water contact angle that does not satisfy the print quality required for the cover glass for portable devices, the contact angle of water for bringing the glass substrate into contact with the acidic solution is adjusted before performing the printing process step. The method for manufacturing a cover glass for a portable device according to claim 1, wherein the print processing step is performed after the adjustment step. A method for producing a cover glass for a portable device in which a printing process is performed on the surface of a glass substrate containing alkali metal ions,
Utilizing the fact that the contact angle of water in the printing region subjected to the printing process on the surface of the glass substrate has a correlation with the print quality on the printed glass substrate,
In order to satisfy the print quality required for the cover glass for portable devices, an adjustment process for adjusting the contact angle of water on the surface of the glass substrate is performed before performing the printing process. Method.   The manufacturing method of the cover glass for portable devices of Claim 3 which performs the printing process process which performs a printing process on the glass substrate surface after the said adjustment process.   The method for producing a cover glass for a portable device according to claim 3 or 4, wherein the adjusting step is to bring the glass substrate into contact with an acidic solution.   The said glass substrate is a glass composition which can be chemically strengthened, The manufacturing method of the cover glass for portable devices of any one of Claims 1-5 characterized by the above-mentioned. A method for producing a cover glass for portable equipment comprising a glass substrate containing alkali metal ions,
Including at least a printing process step of performing a printing process on the glass substrate;
A method for producing a cover glass for a portable device, wherein a treatment for reducing a contact angle of water is performed on an area on which the glass substrate is printed before the printing treatment step.   The method for producing a cover glass for a portable device according to claim 7, wherein the treatment for reducing the contact angle of water on the glass substrate is to bring the glass substrate into contact with an acidic solution. It is a glass composition that can be chemically strengthened, and is a cover glass for portable devices in which printing is performed on at least one of the main surfaces,
A cover glass for a portable device, wherein a contact angle of water in an area of the main surface of the glass substrate on which the printing is performed is 30 degrees or less.   In the printing process, a thermosetting or UV curable resin containing one or more of epoxy, phenol, polyester, polyimide, polyurethane, polymethyl methacrylate, polyolefin, polyvinyl, polyvinyl butyral, and acrylonitrile butadiene styrene is used. The manufacturing method of the cover glass for portable devices of any one of Claims 1-8 characterized by the above-mentioned.

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