JP2002174810A - Glass substrate for display, manufacturing method for the same and display using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass substrate for a display which is made thin and light in weight and manufactured in a short time and has high mechanical strength and transparency, and to provide a manufacturing method therefor and a display using the glass substrate. SOLUTION: A compressive stress layer having >=50 μm depth is formed by chemical strengthening treatment on the surface of a glass substrate formed by using a glass material which contains 40-70 wt.% SiO2, 0.1-20 wt.% Al2O3, 0-20 wt.% Na2O, 0-15 wt.% Li2O and 0.1-9 wt.% ZrO2 and has 3-20 wt.% total content of Li2O and Na2O.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a glass substrate for a display, a method for manufacturing the same, and a display using the same.

[0002]

2. Description of the Related Art Liquid crystal displays are used as display devices for information terminals such as personal computers and mobile phones. Generally, a liquid crystal display has a structure in which liquid crystal is sealed between a pair of substrates on which transparent electrodes are formed. As this substrate, a glass substrate formed of soda lime glass, non-alkali glass, or the like is used.

By the way, with the miniaturization of information terminals such as portable information terminals such as mobile phones, mobile personal computers, and portable AV devices, the weight of glass substrates for displays used in information terminals has been reduced and power consumption has been reduced. Is required. For example, in a reflective liquid crystal display in which an image is reflected by a reflector disposed on the back surface and displayed without using a backlight, when the glass substrate is thicker, parallax is generated, and the image appears to be doubled. Since the images erase each other in color, the brightness of the image decreases. Therefore, it is important to reduce the thickness of the glass substrate used for such a liquid crystal display.

On the other hand, when the thickness of the glass substrate is reduced, there is a problem that the glass substrate is liable to be broken during the manufacturing process or during use of the display. In order to address this problem, it has been proposed to use a tempered glass substrate whose strength has been increased by a tempering treatment as a display substrate. For example, JP-A-57-205343 and JP-A-9-2367
No. 92 discloses a glass substrate for a liquid crystal display whose strength is enhanced by a strengthening treatment.

[0005]

However, when the above-mentioned glass substrate is formed to a thickness used in a portable information terminal, the strength may not be sufficient. For example, in the above-mentioned reflective liquid crystal display, in order to maintain the brightness of the display, it is necessary to use a glass substrate having a thickness of 0.7 mm or less, usually about 0.4 mm. In this case, in a conventional tempered glass substrate, it is sometimes difficult to obtain necessary strength because the thickness of the glass substrate to be tempered is thin.

[0006] In addition, in order to provide a necessary strength by the conventional strengthening method, it may take a long time for the strengthening process.
For example, in order to form a compressive stress layer having a thickness of 50 μm or more on a glass substrate formed of soda lime glass, it is necessary to immerse the glass substrate in a molten salt for 16 hours or more. Even if it is, the labor and cost of manufacturing increase.

Further, depending on the treatment salt used for the strengthening treatment, there are problems that the glass substrate is colored and the treatment salt cost becomes too high. The present invention has been made to solve the above-described problems, and has been made thinner,
An object of the present invention is to provide a glass substrate for a display which can be reduced in weight, has high mechanical strength and transparency, and can be manufactured in a short time, a method for manufacturing the same, and a display using the same.

[0008]

The present invention has a thickness of 0.7 mm.
This is a display glass substrate having a compressive stress layer having a thickness of 50 mm or less and a depth of 50 μm or more on the surface. Since the glass substrate for a display of the present invention is as thin as 0.7 mm or less, it is possible to reduce the thickness and weight of the display and to prevent a decrease in luminance of the display. In addition, since the surface has a compressive stress layer having a depth of 50 μm or more, even if the thickness of the substrate is 0.7 mm or less, it has sufficient strength. For example, when the thickness of the glass substrate of the present invention is 0.4 mm, the glass substrate has a thickness of 0.8 mm and has the same strength as a glass substrate on which a compressive stress layer is not formed. The thickness of the glass substrate for a display of the present invention is preferably 0.2 to 0.5 mm, and 0.2 to 0.45 m.
m is more preferable, and 0.2 to 0.4 mm is most preferable. Further, the depth of the compressive stress layer is preferably at least 70 μm, more preferably at least 100 μm. Although the upper limit of the depth of the compressive stress layer of the glass substrate according to the present invention varies depending on conditions such as the thickness of the substrate, it is usually preferably about １ ／ times the thickness of the substrate.

Such a compressive stress layer can be formed by subjecting a glass substrate to physical strengthening such as quenching or chemical strengthening such as ion exchange. In the present invention, it is preferable to use the chemical strengthening treatment because a compressive stress layer having high mechanical strength can be obtained by the chemical strengthening treatment and the physical strengthening treatment is not suitable for a glass substrate having a thickness of 0.7 mm or less.

In this chemical strengthening treatment, alkali ions having a small ionic radius (eg, sodium ions) on the surface of the glass substrate are replaced with alkali ions having a large ionic radius (eg, potassium ions). By treating the glass substrate with a molten salt containing potassium ions.
By performing such an ion exchange treatment, the composition of the compressive stress layer on the surface of the glass substrate is slightly different from the composition before the ion exchange treatment, but the composition of the deep portion of the substrate is almost the same as the composition before the ion exchange treatment. .

Whether or not the compressive stress layer has been formed by the chemical strengthening treatment can be determined by examining the distribution of metal ions contained near the surface of the glass substrate. Specifically, the depth distribution of the alkali metal ion having a large ionic radius and the alkali metal ion having a small ionic radius is examined,
If (density of metal ions having a large ionic radius) / (density of metal ions having a small ionic radius) is larger in a portion closer to the surface than in a deep portion of glass (a portion having a depth of half the thickness of glass), It turns out that the chemical strengthening by ion exchange was performed.

The depth of the compressive stress layer can be determined by a Babinet correction method using a precision strain gauge or a method using a polarizing microscope. The Babinet correction method using a precision strain meter can be performed by a commercially available measuring device. In the method using a polarizing microscope, the ion-exchange-treated surface of the glass substrate is cut vertically, and its cross section is polished thinly to a thickness of 0.5 mm or less. This can be done by observing with direct Nicol. Since the chemically stressed glass has a compressive stress layer formed near the surface, the thickness of the compressive stress layer is measured by measuring the distance from the surface to the portion where the brightness or color changes.

As a glass substrate on which such a chemical strengthening treatment is performed, a glass substrate containing an alkali ion having a small ionic radius (for example, an alkali metal ion of potassium or less) is used. In addition, in order to form a compressive stress layer, it is necessary to treat the glass substrate with a molten salt when the temperature is below the strain point. Therefore, a glass substrate having a strain point of a certain temperature or higher is used.

The composition of such a glass substrate has durability,
Stability, ion exchange efficiency, strain point, transparency, solubility, machine
It can be determined in consideration of mechanical strength, etc.₂,
Al ₂O₃, Li₂O, Na₂O and ZrO₂Including
Is preferred. Regarding the content of the above components, the following points
It is decided in consideration of.

[0015] SiO ₂ is an essential component for forming a glass skeleton, its a content of less than 40% by weight chemical durability deteriorates, and the melting temperature exceeds 70 wt% is too high. Therefore, the content of SiO ₂ is 40-70.
It is preferable to set the weight%.

Al ₂ O ₃ is a component for improving the ion exchange performance of the glass surface. If its content is less than 0.1% by weight, it has no effect. Conversely, if its content exceeds 20% by weight, devitrification resistance is obtained. Is reduced. Therefore, the content of Al ₂ O _{3 is} 0.1.
The content is preferably set to 1 to 20% by weight.

Na ₂ O is a component that chemically strengthens the glass by being mainly replaced by potassium ions in the ion exchange treatment, and the chemical durability of which content exceeds 20% by weight decreases. Therefore, the content of Na ₂ O is preferably set to 0 to 20% by weight.

Li ₂ O is a component that chemically strengthens the glass by being mainly replaced by sodium ions in the ion exchange treatment. Since the ion exchange rate is higher than that of Na ₂ O, a deep compressive stress layer is formed in a short time. Used to If the content of Li ₂ O exceeds 15% by weight, the devitrification resistance and the chemical durability decrease, and the concentration of sodium ions on the outermost surface of the compressive stress layer increases, so that the Na elution amount increases. Therefore, the content of Li ₂ O is 0 to 15
It is preferable to set the weight%.

When the total content of Li ₂ O and Na ₂ O is less than 3% by weight, the efficiency at the time of ion exchange decreases, and it becomes difficult to form a compressive stress layer having a sufficient depth. on the other hand,
If it exceeds 20% by weight, both the chemical durability and the devitrification resistance of the glass will be reduced. Therefore, Li ₂ O and Na ₂ O
Is preferably 3 to 20% by weight.

ZrO ₂ is a component that improves the ion exchange rate and improves the chemical durability and hardness of glass. If its content exceeds 9% by weight, the solubility of ZrO ₂ becomes supersaturated, and It tends to precipitate without melting. Therefore, the content of ZrO ₂ is preferably 0.1 to 9% by weight.

Further, the glass substrate has an improved melting property,
Improvement of devitrification resistance, adjustment of glass viscosity, adjustment of strain point, heat
For the purpose of adjusting expansion characteristics, improving Young's modulus, fining, etc.
K ₂O, MgO, CaO, SrO, BaO, Zn
O, TiO₂, B₂O₃, La₂O₃, Y₂O₃, P₂
O₅, SnO₂, Sb₂O₃, SO₃Etc.
Can be. Of the above components, MgO, CaO, TiO
_2,Y₂O₃Is a component that improves the Young's modulus,
By containing it, a glass resistant to bending deformation can be obtained.
You.

[0022] Therefore, the glass substrate used in the present _invention, S i _{O 2} of 40 to 70 wt%, the _Al 2 _{O 3} 0.1 to 20 wt%, Li ₂ O 0 to 15 wt%, Na
The ₂ O 0 to 20 wt%, Li ₂ O and Na ₂ O total content 3 to 20 wt% of it is preferably formed of a glass containing a ZrO ₂ 0.1 to 9 wt%.

Further, SiO₂From 45 to 65% by weight of Al
₂O₃From 1 to 20% by weight of Li₂O to 3 to 10% by weight,
Na₂O to 3 to 15% by weight, ZrO₂From 3 to 8% by weight,
Sb ₂O₃Is formed of glass containing 0 to 1% by weight of
Is more preferable. Above desired composition and more preferred
In a new composition, the total content of the above components is 80% by weight.
Preferably at least 90% by weight
Is more preferred, and even more preferably 95% by weight or more.
Good.

When the glass substrate having the above composition is used as the glass substrate to be subjected to the chemical treatment, the treatment salt for performing the chemical strengthening treatment is a treatment salt containing at least one of sodium ion and potassium ion, for example, ,
NaNO ₃ , KNO ₃ or a mixture thereof can be used. In this case, the above treated salt is heated at 350 to 550 ° C.
Ion exchange can be performed by immersing the glass substrate in the molten salt for about 30 minutes to 6 hours for about 30 minutes to 6 hours. Thereby, a transparent compressive stress layer can be formed on the glass substrate.

By subjecting the glass substrate to the above chemical strengthening treatment, the movement of alkali metal ions in the glass substrate is suppressed, and the amount of alkali metal eluted from the glass substrate is reduced. Therefore, it is possible to prevent the alkali metal contamination of the liquid crystal element by the chemical strengthening treatment. In order to further reduce the amount of alkali metal eluted from the glass substrate,
After the chemical strengthening treatment, the glass substrate is washed with water or an acid aqueous solution, or the glass substrate is heated to 120 ° C. or more, preferably 150 ° C.
The heating may be performed to remove the hydronium ions on the surface of the glass substrate, or the surface of the glass substrate may be coated with SiO ₂ .

Further, by subjecting the glass substrate to a chemical strengthening treatment, a dimensional change accompanying heating and cooling of the glass substrate can be suppressed. This makes it difficult for the dimensions of the glass substrate to change due to a temperature change in the manufacturing process of the liquid crystal display. Accordingly, in the manufacturing process of the liquid crystal display in which the thin film and the wiring are superposed on the glass substrate, the displacement of the component parts is reduced, and it is possible to manufacture the liquid crystal display with high precision.

If the glass substrate subjected to the chemical strengthening treatment has a crack source such as a minute scratch (micro crack), the crack source grows and causes the glass to break. The crack source has a greater effect on the substrate strength when present on the end face than when present on the chemically strengthened main surface. Therefore, the strength can be improved by removing the crack source of the glass substrate before the tempering treatment or the glass substrate subjected to the tempering treatment. In particular, it is desirable to remove the crack source on the end face of the glass substrate.

As a method of removing the crack source, there are a method by etching, a method by softening by heating, and the like. In the etching method, the strength of the substrate is improved by immersing the glass substrate in an etching solution containing an acid, removing microcracks, and dulling the tips of the cracks. As the etching solution, a solution containing hydrofluoric acid, for example, a mixed acid of hydrofluoric acid and sulfuric acid, hydrochloric acid, nitric acid or the like is preferably used. By using such a mixed acid, particularly a mixed acid containing hydrofluoric acid, it is possible to form a smooth surface without depositing by-products by etching on the glass substrate surface.

Such an etching treatment can be performed on the glass substrate before chemical strengthening, but by performing it after chemical strengthening, the alkali metal on the glass substrate surface can be removed without relaxing the compressive stress layer. It is desirable to apply after chemical strengthening.

In the method using heat softening, the edge of the glass is heated with a burner or the like to soften the glass. This closes the microcracks and makes the end face a new non-machined surface with no contact. When the shape of the glass surface changes due to softening, the flatness of the glass can be ensured by polishing only the glass surface. Since the method by heat softening requires heating the glass above the softening point, it must be performed before chemical strengthening.

When the glass substrate subjected to the above-mentioned chemical strengthening treatment is cut, the cut end face becomes unstrengthened glass having no compressive stress layer, and the strength is extremely reduced. The inventor found that when a glass substrate having a bending strength of 400 MPa was cut by a chemical strengthening treatment, the bending strength was about 100M.
It was confirmed that it decreased to Pa. Therefore, it is preferable that the glass substrate of the present invention is formed by performing a strengthening treatment on a glass substrate that has been processed in advance to dimensions at the time of use.

The glass substrate for display of the present invention can be polished within a range not exceeding the thickness of the compressive stress layer. The glass substrate of the present invention can be used for a liquid crystal display such as an STN liquid crystal display, a TFT liquid crystal display, a DSTN liquid crystal display, an organic EL display, a field emission display, and the like.

In particular, even if the thickness is 0.7 mm or less, it has a sufficient strength and can be used for a portable display such as a display device of a mobile personal computer, a mobile phone, or a small liquid crystal television. The glass substrate of the present invention can be used for a liquid crystal display such as a reflection type liquid crystal display, a transmission type liquid crystal display, and a semi-transmission type liquid crystal display by forming the thickness to be thin.

[0034]

The present invention will be further described below with reference to examples. (Examples 1 to 7) Glass materials having the compositions shown in Table 1 were heated and melted in a platinum crucible at 1400 to 1500 ° C., clarified, and then poured into a mold to prepare glass. After the glass was solidified, the glass was transferred to an electric furnace heated near the annealing point of the glass, and cooled to room temperature to obtain a glass block.
From this glass block, a thickness of 0.4 mm, 35 × 35
A glass substrate having both sides polished in mm was manufactured.

The glass substrate was immersed in a molten salt maintained at a predetermined temperature for a predetermined time to perform a chemical strengthening treatment, thereby obtaining a reinforced glass substrate having a compressive stress layer with a depth of 50 μm or more on both sides. Then, the uninjured bending strength and the injured bending strength of the obtained tempered glass substrate were measured. Uninjured bending strength is JI
It was measured according to the three-point bending test of S-R1601.

The bending bending strength was measured using a # 150 sandpaper to uniformly scratch one surface of the tempered glass substrate and apply a tensile stress to the surface. As a result, the uninjured strength is 400 MPa or more, and the injured bending strength is 250 MPa.
The above transparent tempered glass substrate was obtained.

Example 8 The tempered glass substrate obtained in Example 1 was immersed in a mixed aqueous solution of 5% diluted hydrofluoric acid and 30% sulfuric acid at room temperature for 5 minutes to perform an etching treatment. The undamaged bending strength of the tempered glass substrate subjected to such etching treatment was 550 MPa, which was able to be improved by about 10% as compared with the value of Example 1 in which no etching was performed.

[0038]

[Table 1]

Example 9 Using the tempered glass substrate (0.4 mm thick, 35 × 35 mm) obtained in Example 8, a transflective 1.8-inch STN liquid crystal display was manufactured. The brightness of this display is 20% compared to a liquid crystal display using a tempered glass substrate with a thickness of 1 mm.
The degree could be improved. Further, the thickness of the substrate is set to 0.
In the case of 7 mm, the brightness could be improved by about 10% compared with the conventional product.

The tempered glass substrate has a sufficient bending strength to reduce the possibility of the substrate being damaged during the manufacturing process of the display, and has a sufficient resistance to the damage expected during use. A durable display could be provided.

Comparative Examples 1 to 3 Glass substrates were manufactured in the same manner as in Examples 1 to 7 using the glass raw materials having the compositions shown in Table 2. The glass substrate was immersed in a treatment salt maintained at a predetermined temperature for a predetermined time to perform a chemical strengthening treatment, thereby obtaining a reinforced glass substrate having a compressive stress layer on both main surfaces. And Example 1
The uninjured bending strength and the injured bending strength of the reinforced glass substrate were measured in the same manner as in Examples 7 to 7.

As a result, the undamaged bending strength was 100 to 45.
Although there was a satisfactory one at 0 MPa, the wound bending strength was 70 MPa.
When the substrate is reduced in thickness and weight is reduced, the substrate is liable to be broken if damaged during use, and is not practically usable.

[0043]

[Table 2]

[0044]

As is apparent from the above description, according to the present invention, a glass substrate for a display having a sufficient strength even if the thickness is reduced is provided. Therefore, by using such a substrate, it is possible to reduce the thickness and weight of the display and to prevent a decrease in the luminance of the display without increasing power consumption.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H090 JB02 JD01 JD13 KA08 LA04 4G059 AA08 AC16 HB03 HB13 HB14 HB23 4G062 AA18 BB01 DA05 DA06 DB02 DB03 DB04 DC01 DD01 DE01 DF01 EA01 EA02 EA03 EA01 EB01 EB01 EB01 EB01 EG01 FA01 FB01 FC02 FC03 FD01 FE01 FF01 FG01 FH01 FJ01 FK01 FL01 GA01 GA10 GB01 GC01 GD01 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ05 JJ07 KK10 KK10 KK10 KK10 KK10 KK10

Claims (8)

[Claims] 1. A surface having a thickness of 0.7 mm or less and a depth of 50 mm
A glass substrate for a display having a compressive stress layer of μm or more. 2. A composition comprising 40 to 70% by weight of SiO ₂ and Al ₂ O
₃ 0.1 to 20 wt%, 0-20 wt% of Na ₂ O,
Li ₂ O is contained in an amount of 0 to 15% by weight, ZrO ₂ is contained in an amount of 0.1 to 9% by weight, and the total content of Li ₂ O and Na ₂ O is 3 to 20%.
A glass substrate for a display having a compressive stress layer having a depth of 50 μm or more on the surface of a glass substrate formed of a glass material of weight%. 3. The display glass substrate according to claim 1, wherein an end surface of the display glass substrate is a surface cut before the compression stress layer is formed. 4. A portable liquid crystal display substrate having a compressive stress layer having a depth of 50 μm or more on its surface. 5. A glass substrate for a reflective liquid crystal display having a compressive stress layer having a depth of 50 μm or more on the surface. 6. A method for producing a glass substrate for a display, comprising a step of chemically strengthening a glass substrate having a thickness of 0.7 mm or less to form a compressive stress layer having a depth of 50 μm or more on the surface. 7. A composition comprising 40 to 70% by weight of SiO ₂ and Al ₂ O
₃ 0.1 to 20 wt%, 0-20 wt% of Na ₂ O,
Li ₂ O is contained in an amount of 0 to 15% by weight, ZrO ₂ is contained in an amount of 0.1 to 9% by weight, and the total content of Li ₂ O and Na ₂ O is 3 to 20%.
A method for manufacturing a glass substrate for a display, comprising a step of chemically strengthening a glass substrate formed of a glass material of weight% to form a compressive stress layer having a depth of 50 μm or more on the surface. 8. A display comprising the glass substrate for display according to claim 1 or a display substrate manufactured by the method according to claim 6 or 7.