JP4489614B2 - Method for improving bending strength of glass substrate - Google Patents

Description

  The present invention relates to a means for improving the bending strength of a thin glass plate suitably used for thin displays such as organic EL displays and liquid crystal displays.

  Thin displays such as organic EL displays and liquid crystal displays are expected to be applied to portable devices, electronic paper, cards, electronic books, etc., and the displays are required to be thin and light and flexible. Therefore, further reduction in thickness and flexibility are required for the glass substrates used for them. By reducing the thickness of the glass substrate to 500 μm or less, the glass substrate becomes flexible. When the thickness is 200 μm or 100 μm or less, the flexibility of the glass is further improved, such as electronic paper. This is desirable for realizing the thin display expected for use in the above-described applications.

  However, since such a thin glass has strength problems such as low impact resistance, measures such as forming a film layer on the glass substrate are taken. For example, Patent Document 1 discloses a base material in which a thin plate made of glass is provided on at least one surface of a transparent resin base material as a glass base material for a liquid crystal display. Patent Document 2 discloses a base material made of glass and plastic having a thickness ≦ 200 μm. These are improving the intensity | strength of a base material by providing a resin layer in thin plate glass.

However, there is a temperature increasing / decreasing process at the time of manufacturing the display, and a thermal load is applied to the substrate. Particularly in a high-definition display equipped with a thin film transistor (TFT), stability at a temperature of 350 ° C. or higher is required. Therefore, it is preferable that the film layer formed on the glass substrate taking these into consideration is also inorganic.
JP-A-4-235527 JP 11-329715 A JP-A-11-322367

  The present invention relates to means for improving the bending strength of a thin glass sheet by forming an inorganic film layer, and provides means for improving the bending strength of a glass substrate and further reducing the thickness of the glass substrate. Is an issue.

  The method for improving the bending strength of a glass substrate according to the present invention is based on forming a film layer by applying and solidifying a silica sol obtained by hydrolysis and polycondensation of a silica precursor onto a glass substrate having a thickness of 200 μm or less. The silica precursor is composed of a tetrafunctional silica precursor and a trifunctional silica precursor, and the surface of the glass substrate is chemically treated before the silica sol is applied to the glass substrate. Etching is performed.

  It is disclosed in Patent Document 3 that chemical cracking in a glass substrate removes microcracks present in the glass surface layer and improves the strength of the glass. In Patent Document 3, a film having a hardness of 5H or more is formed with a pencil scratch value for the purpose of holding a chemically etched glass surface layer.

  Although this method seems to be effective in improving the end face strength of a glass having a thickness of several millimeters, the present invention aims to improve the bending strength of a glass substrate having a thickness of 200 μm or less. Did not have a noticeable effect. In fact, even if a glass substrate having a thickness of 100 μm is chemically etched, it is not ineffective, but hardly contributes to an improvement in bending strength.

  And as a result of earnestly examining a method effective for improving the bending strength of a glass substrate having a thickness of 200 μm or less, the present invention has been made. That is, in the present invention, after a glass substrate is chemically etched, a silica sol obtained by hydrolyzing and polycondensing a silica precursor composed of a tetrafunctional silica precursor and a trifunctional silica precursor is applied to the glass substrate. The most characteristic feature is to form a film layer by solidification. Bending strength can be improved by chemical etching of the glass substrate and formation of a film by the above means.

  The above-described chemical etching of the glass substrate surface is preferably performed using a phosphoric acid solution, a phosphoric acid solution containing hydrogen fluoride, a hydrofluoric acid solution, or an alkaline solution. The use of a hydrofluoric acid solution is particularly preferred, and a hydrofluoric acid solution having a hydrogen fluoride concentration of 0.05 to 0.2% by weight is particularly preferred. The etching solution may be in a heated state, that is, a solution at 40 to 80 ° C.

  And about an above described silica precursor, when the molar ratio of a tetrafunctional silica precursor and a trifunctional silica precursor shall be 1.1: 1 thru | or 1: 1.1, it will improve the bending strength of a glass base material. This is preferable because it produces an effect. The bending strength of the glass substrate also affects the state of the film layer formed on the glass substrate. When a film formed on a glass substrate is prepared using a silica precursor having a composition with the above ratio as a raw material, it is particularly effective in improving the bending strength of the glass substrate.

  The method for improving the bending strength of a glass substrate of the present invention can improve the bending strength of the glass substrate by a simple means. In addition, when the glass substrate is chemically etched, the glass substrate can be made thinner by extending the etching time, which is advantageous for improving the flexibility of the glass substrate. The present invention is effective in providing a glass substrate desirable for realizing the above-mentioned thin display expected to be used for the above.

  The method for improving the bending strength of a glass substrate according to the present invention is based on forming a film layer by applying and solidifying a silica sol obtained by hydrolysis and polycondensation of a silica precursor onto a glass substrate having a thickness of 200 μm or less. The silica precursor is composed of a tetrafunctional silica precursor and a trifunctional silica precursor, and the surface of the glass substrate is chemically treated before the silica sol is applied to the glass substrate. Etching is performed.

  Examples of the tetrafunctional silica precursor include tetramethoxysilane, tetraethoxysilane, tetraphenoxysilane, tetraceacetoxysilane, and tetrachlorosilane.

Trifunctional silica precursors include methyltrimethoxysilane, methyltriethoxysilane, hexyltrimethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, phenyl Triethoxysilane, trifluoromethylmethoxysilane, trifluoromethylethoxysilane, 3-aminopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3- (N, N-diglycidyl) aminopropyltrimethoxysilane, 3-glycidoxysipropyl Limethoxysilane, heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, trifluoropropyltrimethoxysilane, methyltris (2-methoxyethoxy) silane, phenyltris (2-methoxyethoxy) silane, methyltriacetoxysilane , Phenyltriacetoxysilane, vinyltriacetoxysilane, methyltrichlorosilane, phenyltrichlorosilane, vinyltrichlorosilane, octadecyltrichlorosilane, heptadecafluorodecyltrichlorosilane, tridecafluorooctyltrichlorosilane, trifluoropropyltrichlorosilane, etc. .

As the silica precursor, in addition to the tetrafunctional silica precursor and the trifunctional silica precursor, a bifunctional silica precursor may be introduced as necessary. Bifunctional silica precursors include dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, methylphenyldimethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, 3-glycidoxy Propylmethyldimethoxysilane, 3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropylmethyldiethoxysilane, cyclohexylmethyldimethoxy Silane, heptadecafluorodecylmethyldimethoxysilane, 3-methacryloxypropyldimethoxysilane, octadecylmethyldimethoxysilane, dimethyldiacetoxysila , Diphenyl diacetoxy silane, dimethyldichlorosilane, diethyl dichlorosilane, diphenyl dichlorosilane, methylphenyl dichlorosilane, methylvinyl dichlorosilane, octadecyl methyl dichlorosilane, heptadecafluorodecyl methyldichlorosilane, and the like.

  Examples of mixtures used include tetraethoxysilane and methyltriethoxysilane, tetraethoxysilane and methyltrimethoxysilane, tetramethoxysilane and methyltrimethoxysilane, tetraethoxysilane and methyltrimethoxysilane. Examples thereof include a mixture of ethoxysilane and dimethyldiethoxysilane.

  The silica precursor as described above is diluted in a solvent, preferably acidic catalyst such as hydrochloric acid, nitric acid, sulfuric acid, acetic acid, trifluoroacetic acid, phosphoric acid, polycarboxylic acid, sodium hydroxide, potassium hydroxide, hydroxide A basic catalyst such as ammonium, triethylamine, diethylamine, triethanolamine, diethanolamine, alkoxysilane having an amino group or the like may be contained, and more preferably, silica sol is obtained by adding water.

  Examples of the solvent include alcohols such as methanol, ethanol, propanol, butanol and 3-methyl-3-methoxy-1-butanol; glycols such as ethylene glycol and propylene glycol; ethylene glycol monomethyl ether and propylene glycol monomethyl ether Ethers such as propylene glycol monobutyl ether and diethyl ether; ketones such as methyl isobutyl ketone and diisobutyl ketone; amides such as dimethylformamide and dimethylacetamide; ethyl acetate, ethyl cellosolve acetate, 3-methyl-3-methoxy-1 -Acetates such as butanol acetate; aromatic or aliphatic hydrocarbons such as toluene, xylene, hexane, cyclohexane, and γ-buty Lactones, it is preferred to use N- methyl-2-pyrrolidone, an organic solvent such as dimethyl sulfoxide.

The amount of the solvent, the amount of the acidic catalyst or the basic catalyst, and the amount of water can be arbitrarily selected, but the amount of the solvent is 0.1 to 100 times by weight with respect to the silica precursor 1. The amount of acidic or basic catalyst is 0 . 001 times to 0.1 times the amount of water can be used in the range of 0.1 times to 10 times the amount. As means for applying the silica sol to the glass substrate, known means such as dip coating, flow coating, spin coating, roll coating, spray coating, screen printing, flexographic printing and the like can be used.

  And after applying silica sol to the glass substrate, by means of air drying, heating, etc., silanol groups in the polycondensate from the silica precursor, silanol groups in other polycondensates and silanol groups on the glass substrate surface Are combined to obtain a glass substrate on which a film layer is formed by solidifying the coating.

The chemical etching of the glass substrate surface before forming the film layer is performed by bringing an etching solution such as a phosphoric acid solution, a phosphoric acid solution containing hydrogen fluoride, a hydrofluoric acid solution, or an alkaline solution into contact with the glass surface. it can be carried out in. For the contact, a method of immersing the glass substrate in an etching solution, a method of spraying an etching solution on the surface of the glass substrate, etc. can be adopted. If this process is performed, a thinner glass substrate can be obtained.

  Moreover, you may make water contact the film | membrane layer side of the formed glass base material in order to improve the bending strength of a glass base material. As the water to be brought into contact with the membrane layer, water vapor or liquid can be used. However, it is preferable to use liquid because it can be an inexpensive process. In addition, the water is an acid such as hydrochloric acid, nitric acid, sulfuric acid, acetic acid, trifluoroacetic acid, phosphoric acid, polycarboxylic acid, sodium hydroxide, potassium hydroxide, ammonium hydroxide, triethylamine, diethylamine, triethanolamine, Basic substances such as diethanolamine and alkoxysilane having an amino group may be included.

  The glass substrate used in the method for producing a glass substrate of the present invention has a thickness of 200 μm or less, and in particular, the thickness of the glass substrate is preferably 10 μm or more, which is required as a thin display substrate. Is preferably 10 μm to 150 μm, more preferably 50 μm to 100 μm thick. As a material for the glass substrate, soda lime glass, borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, low alkali glass, non-alkali glass, or the like can be used.

1. Selection of Silica Precursor As a silica precursor, tetraethoxysilane (hereinafter referred to as TEOS) which is a tetrafunctional silica precursor and methyltriethoxysilane (hereinafter referred to as MTES) which is a trifunctional silica precursor. Got ready.

  Four times the amount of ethanol solvent was mixed with the silica precursor at room temperature of about 20 ° C. for 10 minutes to obtain a mixture. At this time, TEOS and MTES were mixed at five molar ratios of 100: 0, 70:30, 50:50, 30:70, and 0: 100. Water containing 0.1% by weight of hydrochloric acid was added to the mixture in an amount 4 times the amount of silica precursor introduced and mixed at room temperature of about 20 ° C. for 2 hours to hydrolyze and polycondense the silica precursor. A silica sol was obtained.

  The silica sol was applied to an alkali-free glass (D263, manufactured by Schott) having a thickness of 50 mm × 50 mm × 0.1 mm by a dip coating method with a lifting speed of 3.03 mm / second, and dried at room temperature of about 20 ° C. for 1 hour. Ten samples were obtained for each silica precursor, heated at 0 ° C. for 1 hour.

  The bending strength of the sample obtained in this example was evaluated with a tensile and compression tester [Orientec Co., Ltd .; STA-1225] equipped with a cylindrical bending jig. First, an indenter having a cylindrical inner diameter of 10 mm and a support base having a cylindrical outer diameter of 30 mm were respectively attached to the testing machine, and the center positions of the indenter and the support base were adjusted by an axis alignment jig. In the measurement, the load (breaking load) when the glass was broken when the sample was placed on the support and the load was applied to the sample at a load speed of 0.5 mm / min was measured. Ten samples for measurement were prepared for each sample preparation condition, and the average value of the obtained breaking loads was taken as the bending strength of the sample, and the standard deviation was also obtained.

  The results are shown in FIG. The value of the breaking load is plotted by “◯”, the average value is indicated by “←” in the figure, and the standard deviation is indicated by “n”. In FIG. 1, the X axis represents the molar ratio between TEOS and MTES, and the Y axis represents the bending strength. From this result, it was found that the optimal molar ratio of TEOS to MTES was 50:50, so that the film layer formed after chemical etching of the glass substrate was a silica precursor having the above composition ratio. It was obtained from the body.

2. Evaluation of bending strength when a film layer is formed on a chemically etched glass substrate 5N or 2N NaOH aqueous solution or 5N KOH aqueous solution, 1% by weight or 0.1% by weight The glass substrate surface was chemically etched by immersing it in a 30% aqueous hydrofluoric acid solution for a predetermined time. FIG. 2 shows the relationship between the immersion time and the amount of mass reduction when the glass substrate is immersed in a 0.1 wt% hydrofluoric acid aqueous solution. The thickness of the glass substrate decreased by 0.6 μm after 60 minutes of immersion.

  FIG. 3 is a drawing-substituting photograph obtained by observation with an atomic force microscope on the surface of a glass substrate immersed in a 1 wt% hydrofluoric acid aqueous solution for 1 second, and FIG. 4 is 0.1 wt% hydrofluoric acid. The drawing substitute photograph obtained by observation with the atomic force microscope of the glass base-material surface immersed in aqueous solution for 10 minutes is shown. From this result, it can be seen that a smooth glass surface can be obtained by etching for a long time with a low concentration of hydrogen fluoride.

  A film layer having a molar ratio of TEOS to MTES of 1: 1 was formed on a glass substrate subjected to chemical etching, and the bending strength was evaluated in the same manner as described above. FIG. 5 shows the bending strength of a glass substrate on which a film layer is formed after chemical etching is performed by immersing the glass substrate in an aqueous NaOH solution or an aqueous KOH solution for 30 minutes.

  The value of the breaking load is plotted by “◯”, the average value is indicated by “←” in the figure, and the standard deviation is indicated by “n”. The X axis in FIG. 5 represents the conditions when the sample was prepared, the parentheses indicate the type of the etching solution, and “coating” indicates the glass substrate on which the film layer is formed. And the Y-axis has shown bending strength (Fracture strength). When a film layer is formed on a glass substrate that has been chemically etched, it is significantly more glass than a glass substrate or a glass substrate that has only been chemically etched or a glass substrate that has only been subjected to a chemical layer. The bending strength of the substrate was improved.

  Next, changes in the bending strength of the glass substrate when chemical etching is performed with an aqueous hydrogen fluoride solution will be described. FIG. 6 shows the bending strength of a glass substrate on which a film layer has been formed after chemical etching is performed by immersing the glass substrate in an aqueous hydrogen fluoride solution.

  The value of the breaking load is plotted by “◯”, the average value is indicated by “←” in the figure, and the standard deviation is indicated by “n”. The X axis in FIG. 6 represents the conditions when the sample was prepared. The parentheses indicate the concentration of hydrogen fluoride and the immersion time of the glass substrate, and “coating” indicates the glass substrate on which the film layer is formed. Show. And the Y-axis has shown bending strength (Fracture strength). When a film layer is formed on a chemically etched glass substrate, the glass substrate is bent compared to a glass substrate or a chemically etched glass substrate or a glass substrate with only a film layer formed. The strength was improved, and the bending strength of the glass substrate was significantly improved by optimizing the hydrogen fluoride concentration of the hydrofluoric acid solution. This is presumed that the smooth glass surface formation at the time of chemical etching of the glass substrate was successful as shown in FIG.

It is a figure which shows the relationship between the molar ratio of TEOS and MTES at the time of film layer formation at the time of forming a film layer in the glass base material which has not been chemically etched, and the bending strength of a glass base material. It is a figure which shows the relationship between immersion time when a glass base material is immersed in 0.1 weight% hydrofluoric acid aqueous solution, and mass loss. FIG. 5 is a drawing-substituting photograph obtained by observation with an atomic force microscope on the surface of a glass substrate immersed in a 1 wt% hydrofluoric acid aqueous solution for 1 second. It is a drawing substitute photograph obtained by observation with an atomic force microscope on the surface of a glass substrate immersed in a 0.1 wt% hydrofluoric acid aqueous solution for 10 minutes. It is a figure which shows the bending strength when a film | membrane layer is formed in the glass base material chemically etched by NaOH aqueous solution or KOH aqueous solution. It is a figure which shows the bending strength when a film | membrane layer is formed in the glass base material chemically etched with the hydrogen fluoride aqueous solution.

Claims (3)

Silica precursor to form a hydrolysis and membrane layer by causing coating and solidification polycondensing the sol formed by the thickness of 200μm or less of the plate glass substrate is a method for improving the bending strength of the substrate, the silica The precursor comprises a tetrafunctional silica precursor and a trifunctional silica precursor, and the molar ratio of the tetrafunctional silica precursor to the trifunctional silica precursor is 1.1: 1 to 1: 1.1. , improved method for bending strength of the plate glass substrate, characterized by chemically etching the plate glass substrate surface prior to applying the sol to the plate glass substrate. Chemical etching of the plate surface of the glass base material, phosphoric acid solution, phosphoric acid solution containing hydrogen fluoride, hydrofluoric acid solution, the plate glass substrate according to claim 1, characterized in that an alkaline solution Bending strength improvement method. Chemical etching of the plate surface of the glass base material, a plate glass substrate to Claim 1, the concentration of hydrogen fluoride, and carrying out in a hydrofluoric acid solution of 0.05 to 0.2 wt% To improve the bending strength of steel.