JP5183320B2 - Manufacturing method of glass substrate of cover glass for portable device - Google Patents

Description

  The present invention relates to a cover glass used for protection of portable terminal devices such as a mobile phone and PDA (Personal Digital Assistant) and a digital still camera (DSC), and a method for producing a glass substrate used for a main body of a portable device.

Glass is used as a display cover and body cover against the backdrop of thinning and high quality of portable terminal devices such as mobile phones and PDAs and DSCs. Glass superior in hardness compared to conventional plastics (polycarbonate and acrylic resin) has the advantage that it is not easily scratched. 2. Description of the Related Art In recent years, a protective plate using chemically strengthened glass that is strong even if it is a thin plate has been proposed with a reduction in thickness of portable terminal devices and portable devices (for example, Patent Document 1).
JP 2007-99557 A

  In the conventional processing method described in Patent Document 1, the glass end surface is rough, and the glass end surface is chamfered so that micro cracks of about several tens to several hundreds of μm exist on the glass substrate. However, there is a problem that the mechanical strength required for the above cannot be obtained.

  In order to solve this problem, in the prior application (Japanese Patent Application No. 2007-325542), the present applicant forms a resist pattern of a desired shape on a glass substrate, and etches the glass substrate using the resist pattern as a mask. Thus, it is provided to obtain a glass substrate having a desired shape.

  However, in a process using general photolithography, a substrate excellent in dimensional accuracy and mechanical strength can be obtained. On the other hand, the manufacturing process is complicated and is subject to various restrictions such as setting conditions. Further, since expensive chemicals such as photosensitive resin are used, the process becomes expensive.

The present invention has been made in view of the above points, and has a simple manufacturing process, and a method for manufacturing a glass substrate of a cover glass for portable equipment capable of obtaining a glass substrate excellent in dimensional accuracy and mechanical strength. The purpose is to provide.

The manufacturing method of the glass substrate of the cover glass for portable devices of the present invention is applied to the etchant of the glass substrate by mesh screen printing method or metal screen printing method on one and other main surfaces of the plate-like glass substrate. Forming a resin pattern having etching resistance, and etching the glass substrate from each of the one and the other main surfaces with an etchant capable of etching the glass substrate using the resin pattern as a mask. A step of cutting into a shape; a step of removing the resin pattern formed on the glass substrate; and a step of removing the resin pattern formed on the glass substrate, and then chemically strengthening the glass substrate by ion exchange treatment. It includes a step of, wherein the resin pattern is resistant to solvents containing hydrofluoric acid A, and, characterized in that it consists of a material selected from the group consisting of soluble phenolic resin, unsaturated polyester resin and diallyl phthalate resin in an alkaline solvent.

According to this method, since the printing method is used for forming the mask without using photolithography, the manufacturing process is simple, and a glass substrate excellent in dimensional accuracy and mechanical strength can be obtained. Moreover, since the compressive stress layer is formed on the main surface and end face of the glass substrate, the mechanical strength can be further increased.

In the manufacturing method of the glass substrate of the cover glass for portable devices of the present invention, the glass substrate contains at least one selected from the group consisting of SiO ₂ , Al ₂ O ₃ , Li ₂ O and Na ₂ O. Aluminosilicate glass is preferred. According to this method , a plate-like glass substrate can be formed by the downdraw method (fusion method), so that the main surface of the glass substrate is not scratched and has a very high smoothness on the nanometer order. It can be a glass surface. Therefore, the mirror surface polishing process of the main surface is not required at the time of producing the glass substrate, and a glass substrate free from microcracks is obtained even on the main surface, resulting in a glass substrate having excellent mechanical strength.

According to the manufacturing method of a glass substrate of a cover glass for portable devices of the present invention, the manufacturing process is simple, it is possible to obtain a glass substrate of a cover glass for portable devices with excellent dimensional accuracy and mechanical strength.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
A glass substrate according to an embodiment of the present invention forms a resin pattern having etching resistance against an etchant of the glass substrate on a main surface of a plate-like glass substrate by a printing method, and the resin pattern The mask is obtained by etching the glass substrate into a desired shape by etching with an etchant capable of etching the glass substrate and removing the resin pattern formed on the glass substrate.

  In the present invention, a printing method is used when a resin pattern having etching resistance to an etchant of a glass substrate is formed on the main surface of the glass substrate. The film thickness of this resin pattern can be arbitrarily set as long as it has a sufficient etchant resistance to the etchant of the glass substrate. Considering resistance, non-porous resin pattern, and film thickness variation, a thick film is preferable. As a specific printing method, any method capable of forming a pattern having a printed film thickness of 20 μm or more may be used. For example, screen printing methods, such as a mesh screen printing method and a metal screen printing method, can be mentioned.

  The material of the resin pattern can be appropriately used as long as it has sufficient resistance to the etchant used when etching the glass substrate, but in general, such as hydrofluoric acid contained in the etchant of the glass substrate. In view of resistance to the acid solution, a thermosetting resin is preferable. When using a thermosetting resin, the process of heat-processing the said thermosetting resin pattern is added after the process of forming the thermosetting resin pattern which has tolerance with respect to the etchant of the said glass base material by the printing method.

  The thermosetting resin is preferably a material that is resistant to a solvent containing hydrofluoric acid and is soluble in an alkaline solvent. Examples of such materials include phenol resin, melamine resin, alkyd resin, epoxy resin, resorcin-formalin resin, urea resin, unsaturated polyester resin, or diallyl phthalate resin. . Of these, phenol resins, unsaturated polyester resins, or diallyl phthalate resins are particularly preferred.

  These thermosetting resin patterns are thermoset by performing a heat treatment after printing. The heat treatment conditions vary depending on the type of thermosetting resin, but are 100 ° C. to 250 ° C. for 1 minute to 60 minutes.

  The etching method for etching the glass substrate using the resin pattern as a mask may be either wet etching (wet etching) or dry etching (dry etching). Wet etching is preferable from the viewpoint of reducing the processing cost. The etchant used for wet etching may be anything as long as it can etch a glass substrate. Preferably, an acidic solution mainly containing hydrofluoric acid or a mixed acid containing at least one acid among sulfuric acid, nitric acid, hydrochloric acid, and silicic hydrofluoric acid can be used. The etchant used for dry etching is not particularly limited as long as it can etch a glass substrate. For example, a fluorine-based gas can be used.

  As a chemical | medical agent which removes the resin pattern which remain | survives on a glass substrate, organic alkalis, such as NaOH (sodium hydroxide), KOH (potassium hydroxide), TMAH (tetramethylammonium hydroxide), etc. can be used.

  As a glass substrate, one formed directly from molten glass into a sheet, or one obtained by cutting a glass body molded to a certain thickness into a predetermined thickness and polishing the main surface to a predetermined thickness, etc. Can be used. It is preferable to use what was directly molded into a sheet form from molten glass. This is because the main surface of the glass substrate molded directly from molten glass into a sheet is a hot-molded surface, and has a very high smoothness and a surface state without microcracks. Examples of a method for directly forming a sheet from molten glass include a downdraw method and a float method. Of these, the downdraw method is preferred. In addition to the effects such as high smoothness described above, when performing external processing by an etching process, using the resist pattern formed on both main surfaces of the glass substrate as a mask, when etching the glass substrate from both main surfaces, This is because etching can be performed uniformly from both main surfaces, so that the dimensional accuracy is good and the cross-sectional shape of the end face of the glass substrate is also good. The thickness of the glass substrate is preferably from 0.3 mm to 1.3 mm.

Examples of the glass that can be formed into a glass plate by the downdraw method include aluminosilicate glass containing SiO ₂ , Al ₂ O ₃ , Li ₂ O and / or Na ₂ O. In particular, the aluminosilicate glass is composed of 62 wt% to 75 wt% SiO ₂ , 5 wt% to 15 wt% Al ₂ O ₃ , 4 wt% to 10 wt% Li ₂ O, 4 wt% to 12 wt%. of _Na 2 O, and 5.5 wt% preferably contains ZrO ₂ of 15 wt%, _further, the weight ratio of Na 2 O / ZrO ₂ is 0.5 to 2.0, further Al ₂ O ₃ / weight ratio of ZrO ₂ it is preferred that the composition is 0.4 to 2.5.

SiO ₂ is a main component that forms a glass skeleton. Mobile devices, especially cover glasses for mobile phones, are used in extremely harsh environments such as touching human skin and contact with water and rainwater. It is necessary to have sex. The ratio of SiO ₂ is preferably 62% by weight to 75% by weight in consideration of the chemical durability and the melting temperature.

Al ₂ O ₃ is contained in order to improve the ion exchange performance on the glass surface. The proportion of Al ₂ O ₃ is preferably 5% by weight to 15% by weight in view of chemical durability and devitrification resistance.

Li ₂ O is an essential component for chemically strengthening glass by being ion-exchanged mainly with Na ions in the ion-exchange treatment bath at the glass surface layer. The ratio of Li ₂ O is preferably 4% by weight to 10% by weight in consideration of ion exchange performance, devitrification resistance and chemical durability.

Na ₂ O is an essential component when the glass is chemically strengthened by ion exchange with K ions in the ion exchange treatment bath at the glass surface layer. The ratio of Na ₂ O is preferably 4% by weight to 12% by weight in consideration of the mechanical strength, devitrification resistance, and chemical durability.

ZrO ₂ has the effect of increasing the mechanical strength. The ratio of ZrO ₂ is preferably 5.5% by weight to 15% by weight in consideration of chemical durability and stable production of homogeneous glass.

  Further, the above-described aluminosilicate glass can be further enhanced in mechanical strength by chemical strengthening by ion exchange treatment to form a compressive stress layer on the glass surface. Chemically strengthened glass refers to glass strengthened by replacing alkali metal ions constituting the glass with alkali metal ions having a size larger than that by ion exchange. Note that other multicomponent glass may be used instead of aluminosilicate glass. Further, crystallized glass may be used as long as the transparency necessary for the glass substrate is ensured.

In addition, as ion exchange treatment conditions, a single salt of potassium nitrate (KNO ₃ ), a single salt of sodium nitrate (NaNO ₃ ), and a mixed salt obtained by mixing potassium nitrate and sodium nitrate at an arbitrary weight ratio may be used. The temperature may be selected in the range of 350 ° C. to 450 ° C. and the time in the range of 1 hour to 20 hours.

The mechanical strength of the obtained glass substrate is preferably 5000 kgf / cm ² or more, more preferably 7000 kgf / cm ² or more, most preferably 10000 kgf in terms of the three-point bending strength (three-point bending strength). / Cm ² or more is desirable.

  Next, examples performed for clarifying the effects of the present invention will be described. In the examples shown below, a cover glass for a portable terminal will be described as an example of the glass substrate.

Example 1
First, SiO ₂ is 63.5% by weight, Al ₂ O ₃ is 8.2% by weight, Li ₂ O is 8.0% by weight, Na ₂ O is 10.4% by weight, and ZrO ₂ is 11.9% by weight. The aluminosilicate glass contained was formed into a plate-like glass substrate (sheet-like glass) having a plate thickness of 0.5 mm by the downdraw method. The surface roughness (arithmetic mean roughness Ra) of the main surface of the sheet-like glass formed by this downdraw method was 0.2 nm when examined by an atomic force microscope.

  Next, a phenolic thermosetting resin pattern in the form of a cover glass for mobile terminals is formed on both main surfaces of the sheet-like glass by a mesh screen printing method with a thickness of 20 μm. With respect to this phenolic thermosetting resin pattern, The baking process for 15 minutes was performed at 200 degreeC.

Next, using the phenolic thermosetting resin pattern as a mask, using a mixed acid aqueous solution (40 ° C) of hydrofluoric acid (15%) and sulfuric acid (24%) as an etchant, the sheet glass is etched from both main surface sides. The region was etched and cut into a predetermined shape. Thereafter, the phenol-based thermosetting resin remaining on the glass was dissolved using an NaOH solution, peeled off from the glass, and rinsed. Thus, the cover glass for portable terminals of Example 1 (hereinafter simply referred to as cover glass) was obtained. Further, with respect to the cover glass, the proportion of sodium nitrate (NaNO ₃₎ and potassium nitrate (KNO _3): the _{(NaNO 3} KNO 3), weight ratio of 4: mixed in molten salt 6, 380 ° C., 2 hours Immersion and chemical exchange strengthened by ion exchange treatment. About the obtained cover glass, the bending strength measurement before and behind chemical strengthening was performed. The results are shown in Table 1 below.

In addition, as shown in FIG. 1A, the bending strength measurement is performed by placing a cover glass, which is a glass substrate 1, on two supports (fulcrum points) 2 and 3 arranged at a fixed distance. The test was carried out by applying a load P to the central point between the three through the load body 4 and measuring the maximum bending stress when it was broken. Since the three-point bending strength depends on the distance between the fulcrums, the substrate width, and the substrate thickness, normalization was performed using the following equation.
σ = (3PL) / (2 wt ² )
Here, σ indicates the three-point bending strength (kgf / cm ² ), P indicates the maximum load (kgf) when the glass substrate (cover glass) breaks, and L indicates the distance between the supports 2 and 3. (Cm), w indicates the glass substrate (cover glass) width (cm) as shown in FIG. 1 (b), and t indicates the glass substrate (cover glass) as shown in FIG. 1 (b). Thickness (cm) is shown.

(Example 2)
A portable terminal in the same manner as in Example 1 except that an unsaturated polyester resin pattern in the form of a cover glass for a portable terminal was formed on both main surfaces of the same sheet-like glass as in Example 1 by a mesh screen printing method with a thickness of 30 μm. A cover glass was prepared. About the obtained cover glass, the bending strength measurement before and behind chemical strengthening was performed. The results are also shown in Table 1 below.

(Example 3)
A portable terminal cover glass-like diallyl phthalate resin pattern having a thickness of 25 μm was formed on both main surfaces of the same sheet-like glass as in Example 1 by a mesh screen printing method. A cover glass was produced. About the obtained cover glass, the bending strength measurement before and behind chemical strengthening was performed. The results are also shown in Table 1 below.

Example 4
For portable terminals in the same manner as in Example 1, except that a cover glass-shaped ferrule resin pattern with a thickness of 40 μm was formed on both main surfaces of the same sheet-like glass as in Example 1 by metal screen printing. A cover glass was produced. About the obtained cover glass, the bending strength measurement before and behind chemical strengthening was performed. The results are also shown in Table 1 below.

(Comparative Example 1)
The same sheet glass as in Example 1 was cut out into a cover glass shape for a portable terminal by machining, and then chemically strengthened in the same manner as in Example 1 to produce a cover glass for a portable terminal. About the obtained cover glass, the bending strength measurement before and behind chemical strengthening was performed. The results are also shown in Table 1 below.

As can be seen from Table 1, the glass substrates of Examples 1 to 4 had a three-point bending strength (three-point bending strength) of 5000 kgf / cm ² or more and a high mechanical strength. This is presumably because the glass end surface is an etched surface, so that the surface roughness is small and microcracks of about several tens to several hundreds of μm are not present on the cut surface. On the other hand, the glass base material of Comparative Example 1 is considered to have microcracks of about several tens of μm to several hundreds of μm on the cut surface because the glass end surface is a machined surface.

  The present invention is not limited to the above embodiment, and can be implemented with appropriate modifications. For example, the materials, processing procedures, and the like in the above-described embodiment are merely examples, and various modifications can be made within the scope of the effects of the present invention. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  The glass substrate obtained by the method of the present invention can be used for a cover glass used for protecting a portable terminal device such as a mobile phone or a PDA, a digital still camera, or a main body of a portable device.

It is a figure for demonstrating a bending strength measuring apparatus.

Explanation of symbols

1 Glass substrate 2, 3 Support body 4 Load body

Claims (2)

Forming a resin pattern having resistance to etching on the etchant of the glass substrate on one and the other main surfaces of the plate-like glass substrate by a mesh screen printing method or a metal screen printing method; and Etching the glass substrate from each of the one and the other main surfaces with an etchant capable of etching the glass substrate as a mask, and cutting the resin pattern into a desired shape, and the resin pattern formed on the glass substrate And removing the resin pattern formed on the glass substrate and then chemically strengthening the glass substrate by ion exchange treatment ,
The resin pattern is made of a material selected from the group consisting of a phenolic resin, an unsaturated polyester resin, and a diallyl phthalate resin that is resistant to a solvent containing hydrofluoric acid and is soluble in an alkaline solvent. A method for producing a glass substrate of a cover glass for a portable device, which is characterized by the above. The glass substrate _is mobile according to claim 1, characterized in that the aluminosilicate glass containing at least one selected from _{SiO 2, Al 2 O 3,} Li 2 O and the group consisting of Na ₂ O The manufacturing method of the glass base material of the cover glass for apparatuses.

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