JPWO2009157378A1 - Etching method and display device of alkali-free glass substrate - Google Patents

Abstract

The present invention is a method for etching the surface of an alkali-free glass substrate containing one or more metals selected from the group consisting of Ca, Sr, Ba and Mg, wherein HF and HCl are represented by the formula (A) HF: 5% by mass to less than 20% by mass, HCl: 9% by mass or more, formula (B) HF: 20% by mass to less than 30% by mass, and HCl: 5% by mass or more or formula (C) HF: The present invention relates to an etching method for etching the surface of the alkali-free glass substrate using an etching solution that satisfies the conditions of 30% by mass or more and HCl: 2% by mass or more and does not contain NH4F.

Description

  The present invention relates to a method for etching an alkali-free glass substrate. More specifically, the present invention relates to an etching method for thinning an alkali-free glass substrate used for a substrate of a display device such as a liquid crystal display device (LCD) or an organic EL display device (OELD).

  In the field of portable display devices such as LCDs and OLEDs with small and medium screen sizes, especially mobile, digital cameras and mobile phones, it is important to reduce the weight and thickness of display devices. In order to reduce the thickness of the glass substrate that constitutes the display device, a method of reducing the plate thickness by etching the outer surface of each glass substrate after the bonding process between the array substrate and the color filter substrate is widely adopted. ing. For example, a glass substrate having an original plate thickness of 0.4 to 0.7 mm is etched to form a glass substrate having a plate thickness of 0.1 to 0.4 mm.

  Currently, many alkali-free glass substrates are used for flat panel display (FPD) applications. In the etching of the alkali-free glass substrate, an etching solution containing hydrofluoric acid (HF) is generally used because of its excellent glass etching action (see Patent Document 1). An etching solution containing hydrofluoric acid is also used in an etching process performed for the purpose of making the surface of a glass disk for information recording media such as a hard disk drive into a desired surface having fine protrusions (Patent Document). 2).

Further, it is known that a mixed solution of hydrofluoric acid and hydrochloric acid is applicable as an etchant for etching a glass substance, and the etching state is controlled by changing the composition of both (Non-patent Document 1). . Non-Patent Document 1 targets silica glass (amorphous SiO ₂ ) and quartz (crystalline SiO ₂ ), and is different from the object (non-alkali glass) in the present invention. Non-Patent Document 1 mainly relates to the examination of the dissolution rate of the sample in the etching solution (which is almost the same as the etching rate) and does not have the purpose of thinning the glass sheet. Therefore, there is a description that the surface shape after etching is not regarded as important, but rather a large number of pits having a diameter of about 50 μm are generated on the surface (FIG. 8). This is clearly a problem because fine irregularities are generated on the glass surface, causing haze in which the glass becomes cloudy. Further, Non-Patent Document 1 does not pay attention to the residue generated during etching. This is because the etching with HF for silica glass (amorphous SiO ₂ ) and quartz (crystalline SiO ₂ ) has the following formula:
SiO ₂ + 6HF → H ₂ SiF ₆ + 2H ₂ O
The H ₂ SiF ₆ produced here is ionized in an acidic solution,
^{_{H 2 SiF 6 → 2H + +}} SiF 6 2-
It is thought that it exists stably in the form of ions and does not produce a residue. Therefore, it can be seen that the system is completely different from the etching of alkali-free glass, which is known to generate residues (hereinafter also referred to as suspended substances or unnecessary generated substances).

  Conventionally, in an etching process for thinning a large glass substrate for FPD use, it is known that glass and an etching solution react to generate a suspended substance, resulting in a reduction in performance of the etching solution. Therefore, in the etching process, the suspended substance is filtered and the cleaned etching solution is circulated so that the performance of the etching solution in the etching tank is maintained and the etching solution can be used continuously for a long time. (See Patent Document 3).

Further, in the glass substrate for FPD, flatness is strongly demanded from the viewpoint of displaying an image. In particular, generation of haze in which fine irregularities are generated on the glass surface and the glass becomes cloudy is the most problematic. In order to ensure the flatness of the surface of the glass substrate, for example, a method of performing a post-polishing step after pre-polishing with a strong acid such as 10 to 30% by mass of HF or 20 to 50% by mass of H ₂ SO ₄ (Patent Document 4) See).

Further, a method is known in which surface polishing is performed with 40 to 90% by mass of H ₂ SO ₄ and 0.4 to ₄ % by mass of HF, followed by post polishing with 2 to 30% by mass of HF. (See Patent Document 5).

  In the method using the two steps of pre-polishing and post-polishing as described above, it is impossible to etch the glass uniformly and deeply because the pre-polishing step contacts the glass only for a very short time. Furthermore, it is necessary to go through many steps. From the above, productivity is generally poor, and it is necessary to renew the equipment, which is extremely disadvantageous in terms of cost.

  Also known is a method of etching a multi-component FPD glass substrate using an etchant mainly composed of hydrofluoric acid, ammonium fluoride and hydrochloric acid (see Patent Document 6). Etching solutions containing ammonium fluoride are well known as buffered hydrofluoric acid and have been routinely used in semiconductor manufacturing processes. In addition, it has been tried for a long time to thin a glass substrate, and as one of the methods, it has been known that chemical polishing, that is, etching the surface of a glass substrate with an etching solution having a predetermined composition condition (Patent Document). 7). It has also been known that a glass substrate is etched with an etching solution having a specific composition as a surface treatment before resist application in a manufacturing process of LCD or the like (see Patent Document 8, Table 1).

  However, it is an etching method for thinning a multicomponent non-alkali glass substrate containing a predetermined amount or more of an alkaline earth metal, that is, Ca, Sr, Ba or Mg, which is an unnecessary suspension. An etching method that can suppress the generation of substances, can utilize an existing etching apparatus, and can complete etching for thinning in one etching process has not been known.

Japanese Unexamined Patent Publication No. 2003-313049 Japanese Patent Laid-Open No. 2002-237030 Japanese Unexamined Patent Publication No. 2008-127585 Japanese Unexamined Patent Publication No. 2005-343742 Japanese Unexamined Patent Publication No. 2007-297228 Japanese Unexamined Patent Publication No. 2003-63842 Japanese Unexamined Patent Publication No. 50-29620 Japanese Unexamined Patent Publication No. 52-144020

J. et al. Am. Ceramics Soc. , 70 [8] 570-77 (1987)

  The present invention is an etching method for reducing the thickness of a non-alkali glass substrate in order to solve the above-described problems of the prior art, in which the etching solution is not suspended by unnecessary products, that is, the volume of the precipitate. An object of the present invention is to provide an etching method that has a small ratio (hereinafter, referred to as volume precipitation rate), has a high etching rate, and can suppress the occurrence of haze on the surface of a glass substrate.

  Conventionally, hydrofluoric acid (HF) and hydrochloric acid or a mixed acid of other acids has been used as an etchant for etching a glass substrate. However, good etching conditions are specifically shown under conditions where the etching amount is as large as 1 to 1000 μm and haze on the surface of the glass substrate is likely to occur, as in etching for thinning an alkali-free glass substrate. Was not.

  In addition, etching characteristics suitable for mass production of FPDs are required. In addition, there has been no known method that can stably perform uniform etching treatment in a plane at a high etching rate using a material that is usually easily available.

  Patent Document 1 describes that an etchant containing a mixed acid of hydrofluoric acid and another acid such as hydrochloric acid, sulfuric acid, phosphoric acid, or the like is used as an etchant. However, it is not described that haze is generated on the glass substrate surface when the glass substrate surface is etched using an etchant containing hydrofluoric acid. Further, it has not been recognized at all that the etching solution needs to have a specific composition in order to suppress the generation of haze.

  Furthermore, since Patent Document 1 mainly discloses a method for regenerating an etching solution, it does not describe the surface properties of the glass after the etching process, and does not describe the etching rate during the etching process.

  Patent Document 3 aims to improve etching efficiency by filtering an etching solution and circulating it through an etching tank. However, there is no description of the presence or absence of haze generation on the glass substrate, the etching rate by the etching solution, and the like. Further, there is no description of changes in the volume precipitation rate depending on the composition of the etching solution.

  In the case of Patent Documents 4 and 5, it is necessary to go through a multi-step process, and although there is a description of the circulation of the etching solution, there is no description of measures against the precipitate generated during etching, and the occurrence of haze in the subsequent process There is no mention of countermeasures. In Patent Document 6, there is no disclosure about etching of an alkali-free glass substrate having a specific composition.

  As a result of diligent studies, the inventors of the present invention have found a new composition of an etching solution, and when the surface of an alkali-free glass substrate is etched, the volume precipitation rate of unnecessary products can be reduced and further haze is generated on the surface of the glass substrate. Thus, it has been confirmed that etching can be performed at a high etching rate.

That is, aspect 1 of the present invention is a method for etching the surface of an alkali-free glass substrate containing at least one metal selected from the group consisting of Ca, Sr, Ba and Mg,
An etching method in which the surface of the alkali-free glass substrate is etched using an etchant in which HF and HCl satisfy the conditions of formula (A), formula (B), or formula (C) and do not contain NH ₄ F. I will provide a.
HF: 5% by mass to less than 20% by mass, and HCl: 9% by mass or more (A)
HF: 20% by mass to less than 30% by mass, and HCl: 5% by mass or more (B)
HF: 30% by mass or more and HCl: 2% by mass or more (C)
In the method as described above, an aqueous HF solution and an aqueous HCl solution are mixed and diluted with water as necessary. HF is arbitrarily mixed with water at a boiling point (19.54 ° C.) or lower, and an aqueous solution of about 45 to 100% by mass is sold and used as a reagent. Here, HF for atomic absorption (concentration: 49.5 to 50.5% by mass) was used. HCl is usually sold and used as a reagent as a saturated aqueous solution, and its concentration is 35 to 37% by mass. Here, HCl for atomic absorption (concentration: 35.5 to 36.5% by mass) was used.

  Aspect 2 provides the etching method according to aspect 1, wherein the alkali-free glass substrate is a color filter substrate in which a transparent electrode and a color filter are provided on one surface of the glass substrate.

  Aspect 3 provides the etching method according to aspect 1, wherein the alkali-free glass substrate is an active element substrate in which a transparent electrode and an active element are provided on one surface of the glass substrate.

  Aspect 4 is the etching method according to aspects 1, 2, or 3, wherein the non-alkali glass substrate and another glass substrate are combined to face each other to form a display cell in which an internal circuit is sealed, and then etching is performed. provide.

  Aspect 5 provides the etching method according to aspect 4, wherein the other glass substrate is also the alkali-free glass substrate.

  Aspect 6 provides the etching method according to aspect 4, wherein the glass substrates on both sides of the display cell are the non-alkali glass substrates, respectively, and the outer surfaces thereof are etched simultaneously.

Aspect 7 provides the etching method according to Aspect 1, 2, 3, 4, 5 or 6 in which the alkali-free glass substrate satisfies the following composition (1) in terms of an oxide-based mass percentage.
SiO _2: 50-66 _{wt%, Al} 2 O 3: _{10.5~22 wt%, B} 2 O 3: _1~12 wt%, MgO: 0 to 8 mass%, CaO: from 0 to 14.5% by weight , SrO: 0 to 24% by mass, BaO: 0 to 13.5% by mass, MgO + CaO + SrO + BaO: 9 to 29.5% by mass (1)

Aspect 8 provides the etching method according to Aspect 1, 2, 3, 4, 5 or 6 in which the alkali-free glass substrate satisfies the following composition (2) in terms of an oxide-based mass percentage.
SiO _2: 58 to 66 _{wt%, Al} 2 O 3: _{15~22 wt%, B} 2 O 3: _5~12 wt%, MgO: 0 to 8 mass%, CaO: 0 to 9 wt%, SrO: 0 .5 to 12.5% by mass, BaO: 0 to 2% by mass, MgO + CaO + SrO + BaO: 9 to 18% by mass (2)

Aspect 9 provides the etching method according to Aspects 1, 2, 3, 4, 5 or 6 in which the alkali-free glass substrate satisfies the following composition (3) in terms of oxide-based mass percentage.
SiO _2: 50 to 61.5 _{wt%, Al} 2 O 3: _{10.5~18 wt%, B} 2 O 3: _7~10 wt%, MgO: 2 to 5 wt%, CaO: 0 to 14.5 Mass%, SrO: 0 to 24 mass%, BaO: 0 to 13.5 mass%, MgO + CaO + SrO + BaO: 14.5 to 29.5 mass% (3)

  Aspect 10 provides the etching method according to any one of aspects 1 to 9, wherein the etching is performed while maintaining the temperature of the etching solution at 20 to 60 ° C. When the temperature at the time of etching is high, the etching rate of the glass substrate can be increased.

In aspect 11, when etching, bubbling into the etching solution in which the glass substrate is immersed, spraying of the etching solution onto the surface of the glass substrate, stirring of the etching solution in which the glass substrate is immersed, and immersion The etching method in any one of the aspects 1-10 which perform 1 or more types of operation chosen from the group which consists of rocking | fluctuation or rotation of the glass substrate in the etching liquid which is being provided is provided.
In the above operation, the etching solution may be injected either in the etching solution in which the glass substrate is immersed or in the air. However, it is preferable to spray the glass substrate in the etching solution in which the glass substrate is immersed. It is preferable because it can be easily etched and controlled uniformly.

  Aspect 12 provides the etching method according to any one of Aspects 1 to 11, wherein the etching rate of the glass substrate is 1.3 μm / min or more.

  Aspect 13 is the etching according to any one of aspects 1 to 12, wherein the etching liquid for composition adjustment is replenished so as to keep the content ratio of HF and HCl substantially constant while etching the alkali-free glass substrate. Provide a method.

  Aspect 14 provides a display device including a glass substrate treated by the etching method according to any one of aspects 1 to 13. Examples of the display device include OLED and LCD.

  In the present invention, the total content of alkaline earth metals contained in the alkali-free glass substrate is at least 9% by mass or more in terms of oxide based mass percentage. The effect of the etching solution of the present invention is more exhibited when the etching solution of the present invention is used for alkali-free glass having a total alkaline earth metal content of 14.5% by mass or more.

  Furthermore, it is preferable to use the etching solution of the present invention for an alkali-free glass substrate containing Ca, Sr, Ba, or Mg in a glass in an oxide-based mass percentage display of 15% by mass or more.

  In addition, among alkaline earth metals, Sr is present on an alkali-free glass substrate containing 0% by mass or more, preferably 2% by mass or more, and more preferably 4% by mass or more in terms of mass percentage based on oxide. It is preferable to use the etching solution of the invention.

  According to the present invention, it is possible to reduce the volume sedimentation rate of the precipitate generated by the reaction between the etching solution and the alkali-free glass substrate (35% by volume or less). Furthermore, the haze of the glass substrate surface can be reduced (haze value is 1 or less), and the surface of the glass substrate can be etched at a high etching rate (1.3 μm / min or more).

  Therefore, it is suitable for the etching process aiming at thinning of a glass substrate, for example, the etching process of the glass substrate for thinning a display device. In particular, it is suitable for etching processing of glass substrates for small and medium-sized LCDs and OLEDs typified by portable display devices such as mobiles, digital cameras and mobile phones.

Furthermore, since the above-mentioned effect can be obtained only by exchanging the etching solution for the current equipment that is performing the etching operation for the purpose of reducing the thickness of the glass substrate, no new equipment investment is required. Furthermore, the etching process does not need to go through a multi-step process, and since the etching rate is high, it is considered that it is very useful for improving productivity.
Further, if the condition of the above formula (A), (B) or (C) is satisfied, the etching rate is 1.3 μm / min or more, the haze value is 1 or less, and the volume precipitation rate is 35% by volume or less. Can be achieved.

FIG. 1 is an explanatory view showing an etching method of the present invention. FIG. 2 is a schematic diagram showing a cross-sectional structure of the LCD.

  The present invention aims to reduce the thickness of an alkali-free glass substrate and the like, and etches the surface of a glass substrate in an etching amount of 1 to 1000 μm. The present invention relates to one side of the surface of the glass substrate and can be preferably used for etching by an etching amount of 10 to 650 μm. Furthermore, it is suitable for performing an etching process with an etching amount of 150 to 600 μm.

In the etching method of the present invention, the surface of the glass substrate is etched as a mixed acid by combining HF concentration and HCl concentration under a predetermined condition as an etchant. In this case, the condition is that no ammonium fluoride is contained. When ammonium fluoride is contained, ammonium ions (NH ₄ ⁺ ) and Al ions (Al ³⁺ ) are combined with F ⁻ in the etching solution to form Al—F ions, thereby generating unnecessary products and etching. This is because it shows an unstable tendency. However, it is possible to include an extremely small amount of ammonium fluoride in the etching solution to such an extent that unnecessary products are not generated.

  In the present invention, the method of contacting the etching solution with the non-alkali glass substrate, which is an object to be etched, can be selected widely from known methods such as an immersion method, a spray method, and a showering method. Therefore, there is no big barrier to using existing facilities, which is preferable. In the case of etching an alkali-free glass substrate by the dipping method, the etching solution is stirred from the viewpoint of suppressing the generation of haze on the surface of the glass substrate and preventing the generation of precipitates in the etching solution. However, it is preferable to perform the etching treatment. The stirring action can be substituted by other methods having stirring ability such as bubbling and ultrasonic treatment.

  In the present invention, as the etching solution, the HF concentration and the HCl concentration are set so as to satisfy the above formula (A), formula (B), or formula (C), thereby reducing the volume precipitation rate and generating haze. Without etching, the glass substrate surface has a high etching rate, preferably 1.3 μm / min or more, more preferably 2.5 μm / min or more, further preferably 5 μm / min or more, particularly preferably 10 μm / min or more, most Preferably, the etching can be performed at an etching rate of 15 μm / min or more.

  When the HF concentration in the etching solution is less than 5% by mass, the etching rate is lowered, and in order to achieve a desired etching amount, it takes a long time to treat the glass substrate with the etching solution. For example, in the case of the dipping method, since the time for dipping the glass substrate in the etching solution becomes long, the productivity deteriorates, which is not preferable. It is generally known that the etching rate is improved when the HF concentration is increased.

  Moreover, when etching time becomes long, precipitate will generate | occur | produce on the glass surface and will cause a haze. Furthermore, in the present invention, it was revealed that the volume precipitation rate can be reduced by increasing the concentration of HF. Since a higher etching rate can be obtained, generation of haze of the glass substrate after etching can be suppressed. Furthermore, in order to reduce the volume precipitation rate, the HF concentration is preferably 10% by mass or more, more preferably 20% by mass or more, and most preferably 30% by mass or more.

  By adding HCl to the etching solution, the etching rate is improved, the generation of haze is suppressed, and the volume precipitation rate of the precipitate is further reduced. When HCl is not added, all of the above three points become worse. In view of the etching rate, the generation of haze, and the volumetric precipitation rate of the precipitate, in the present invention, it is essential to add HCl to the etching solution.

  Moreover, the most preferable form in the etching liquid of this invention is mixing HF aqueous solution (including anhydrous HF) of arbitrary density | concentration and saturated HCl aqueous solution so that it may become a desired HF density | concentration. At that time, the higher the concentration of the HF aqueous solution, the more preferable. In the present invention, HF and HCl are combined and used as a mixed acid as described above. HCl is suitable for uniform etching of the surface of the glass substrate, and is considered to be superior in terms of solubility of unnecessary products as compared with other acidic substances.

When an alkali-free glass substrate containing an alkaline earth metal is etched using an etchant containing HF, a large amount of precipitates may be generated in the etchant. This is because Al ions (Al ³⁺ ) eluted from the glass substrate during the etching process combine with F ⁻ in the etching solution to generate AlF ₆ ^3- ions, which are further metal ions (Ca ²⁺ , Mg ²⁺ , Sr ²⁺ , Ba ²⁺ ) and insoluble or poorly soluble salts (M ₃ [AlF ₆ ] ₂ M is Ca ²⁺ , Mg ²⁺ , Sr ²⁺ or Ba ^{2 +} ) Is considered to be the cause. Therefore, it is considered that containing a large amount of Ca, Mg, Sr, or Ba contributes to the generation of unnecessary products during the etching of the glass substrate.

Among insoluble or hardly soluble salts (M ₃ [AlF ₆ ] ₂ ), Sr ₃ [AlF ₆ ] ₂ is difficult to settle and exists in a floating state in the etching solution. May be a problem.
AlF ₆ ³⁻ ions that cause this insoluble or hardly soluble salt (M ₃ [AlF ₆ ] ₂ ) are likely to be generated under acidic conditions of pH 1-6. An etching solution containing only HF has an acidic condition of pH _{1 to} ³ , and AlF ₆ ³⁻ ions are likely to be generated. As a result, the generation of insoluble or hardly soluble salt (M ₃ [AlF ₆ ] ₂ ) increases, and the precipitate in the etching solution increases.

On the other hand, in the etching method of the present invention, a mixed acid of an etching solution having an HF concentration of 5% by mass or more and an HCl concentration of 2% by mass or more is used as an etching solution, so that the etching solution has a strong acid condition of pH 1 or less. Therefore, generation of AlF ₆ ³⁻ ions hardly occurs. As a result, the production of insoluble or hardly soluble salts (M ₃ [AlF ₆ ] ₂ ) is reduced, and the amount of precipitates generated in the etching processing solution is greatly reduced.

This is a preferable characteristic for repeatedly using the etching solution. Furthermore, in this invention, the volume precipitation rate of an unnecessary product can be reduced by setting HF density | concentration high. The principle / mechanism is not clear, but a large amount of F ⁻ ions and metal ions (Ca ²⁺ , Mg ²⁺ , Sr ²⁺ , Ba ²⁺ ) eluted from the glass substrate are directly bonded to form crystalline This is probably because a precipitate with a small volumetric precipitation rate was produced.

According to the present invention, the composition of the alkali-free glass substrate to be etched is not particularly limited. While satisfying the conditions of alkali-free glass, it can be applied to alkali-free glass having a wide range of compositions. Among these, precipitation during etching treatment is performed on an alkali-free glass substrate containing Ca ²⁺ , Mg ²⁺ , Sr ²⁺ , and Ba ²⁺ in the glass composition, particularly an alkali-free glass substrate containing Sr ^2+. The etching solution of the present invention is preferable in that the amount of the material can be greatly reduced. Al ³⁺ is a component usually contained in the glass composition.

The present invention is suitable for etching treatment of an alkali-free glass substrate having the following composition (1) in terms of oxide-based mass percentage.
Of alkali-free glass (100% by mass), SiO ₂ : 50 to 66% by mass, Al ₂ O ₃ : 10.5 to 22% by mass, B ₂ O ₃ : 1 to 12% by mass, MgO: 0 to 8% by mass %, CaO: 0 to 14.5 mass%, SrO: 0 to 24 mass%, BaO: 0 to 13.5 mass%, MgO + CaO + SrO + BaO: 9 to 29.5 mass% (1).

Further, it is particularly suitable for etching treatment of an alkali-free glass substrate having the following compositions (2) and (3) in terms of oxide-based mass percentage.
Of alkali-free glass (100% by mass), SiO ₂ : 58 to 66% by mass, Al ₂ O ₃ : 15 to 22% by mass, B ₂ O ₃ : 5 to 12% by mass, MgO: 0 to 8% by mass, CaO: 0-9 mass%, SrO: 0.5-12.5 mass%, BaO: 0-2 mass%, MgO + CaO + SrO + BaO: 9-18 mass% (2).

Of alkali-free glass (100% by mass), SiO ₂ : 50 to 61.5% by mass, Al ₂ O ₃ : 10.5 to 18% by mass, B ₂ O ₃ : 7 to 10% by mass, MgO: 2 to 2 5 mass%, CaO: 0-14.5 mass%, SrO: 0-24 mass%, BaO: 0-13.5 mass%, MgO + CaO + SrO + BaO: 14.5-29.5 mass% (3).

  The present invention relates to a glass substrate for a display device, in particular, a glass substrate for a small-to-medium-sized LCD represented by a portable display device such as a mobile, a digital camera or a mobile phone, a glass substrate for an OLED, and an LCD for a notebook PC It is suitable for performing an etching process for the purpose of thinning a glass substrate. However, the present invention is not limited to these applications. For the purpose of thinning other glass substrates, for example, a glass substrate for large LCDs for monitors and televisions, a glass substrate for large OLEDs, and a glass substrate for PDPs are thin plates. It can be preferably used also for the etching treatment for the purpose of making it.

  Hereinafter, the present invention will be described in more detail with reference to examples. In the examples, the following experiments were conducted on the type 1 and type 2 glass substrates shown in Table 1 below. In the table, NA indicates that no experiment was conducted. X in the table indicates that the etching solution could not be produced because the concentration was not theoretically obtained when the reagents used in this experiment were mixed.

(Etching rate)
An etching solution having the composition shown in Table 2 below was filled in a thermostat kept at 25 ° C., and a 4 × 4 cm glass substrate was immersed using a jig. After etching for a predetermined time, the glass substrate was taken out, washed, and the mass of the glass substrate was measured. The etching amount was estimated from the difference in mass, area, and specific gravity of each glass substrate. This operation was repeated, the relationship of the etching amount with respect to the etching time was determined, and the slope of the approximate line was taken as the etching rate. Note that the etching solution was changed as appropriate.

(Haze value)
A 2 × 2 cm glass substrate was immersed in an etching solution having the composition shown in Table 3 below using a jig. Using the etching rate investigated by the above method, the surface of the glass substrate was etched for a time during which the etching amount on one side of the glass substrate was 150 μm. Note that the etching solution was changed as appropriate. After washing, the haze value of the glass substrate surface was measured with a touch panel type haze computer manufactured by Suga Test Instruments Co., Ltd. In addition, if the haze value of the glass substrate surface is 1 or less, it can be said that substantially no haze was generated, and the haze value is more preferably 0.5 or less. In addition, <in the table | surface means that the value smaller than the numerical value to compare is shown on measurement precision.

(Volume sedimentation rate)
To a polyethylene test tube, 0.25 g of glass obtained by pulverizing a glass substrate was added, and 10 ml of an etching solution shown in Table 4 below was added. After ultrasonic treatment for 10 minutes, the mixture was allowed to stand, and the volume precipitation rate obtained by dividing the precipitation amount after 24 hours by the etching solution amount was calculated. In these experiments, the temperature of the etching solution can be performed at room temperature, but it can also be preferably maintained at 30 to 60 ° C. The volume precipitation rate is preferably 35% by volume or less, more preferably 20% by volume or less, and particularly preferably 10% by volume or less. <In the table of volumetric precipitation rate means that the value is smaller than the numerical value to be compared in terms of measurement accuracy.
It should be noted that the etching rate, haze value, and volumetric precipitation rate are difficult to adjust independently when performing etching and are parameters that are related to each other. Therefore, considering these three factors, either one or two Etching can also be performed under conditions that emphasize parameters.

  As apparent from Tables 2 to 5 above, when the HF and HCl concentrations satisfy the conditions of the formula (A), the formula (B), or the formula (C), the surface of the glass substrate is formed without generating haze. It was possible to etch at an etching rate of 1.3 μm / min or more.

  As apparent from Tables 6 and 7 above, it was confirmed that the volume precipitation rate of unnecessary products decreased as the HF concentration and the HCl concentration in the etching solution increased. Under the present experimental conditions, the volume precipitation rate is preferably 35% by volume or less, more preferably 20% by volume or less, and most preferably 10% by volume or less from the viewpoint of the etching solution life.

  Therefore, etching is performed so as to satisfy the conditions of the above formula (A), formula (B), or formula (C). However, when etching a glass substrate of a specific display device, as an etching rate, 1.3 μm / min or more, haze value is 1 or less, or volume precipitation rate is 35% by volume or less individually evaluated, It is also possible to perform etching by selecting one or two parameters and satisfying the reference value and selecting composition conditions of HF and HCl. This is because there is an allowable range depending on the glass composition of the glass substrate and the substrate size.

In addition, in the case of HF 20 mass% or more, it turns out that the said characteristic is satisfy | filled even if HCl concentration is 0 mass%. Particularly, the volume precipitation rate is small because the F ⁻ ions present in large quantities and the metal ions (Ca ²⁺ , Mg ²⁺ , Sr ^2+, Ba ²⁺ ) eluted from the glass substrate are directly bonded, This is thought to be due to the mechanism that forms a rough precipitate. However, when the HCl concentration is 0% by mass, the change in the etching rate with time is large, and it is predicted that actual process management will be difficult. The reason is shown below. HF is a weak acid and is weakly ionized in an aqueous solution as follows.
HF ⇔ H ^{+ +} F ^-
When the etching solution is only HF, F consumed by etching and free F ⁻ become ions of SiF ₆ ²⁻ and AlF ₆ ³⁻ , and precipitates of CaF ₂ , MgF ₂ , SrF ₂ , BaF _{2 and the} like. And no longer contributes to etching. Therefore, the etching rate is lowered.
On the other hand, HCl is a strong acid and is mostly ionized in the aqueous solution as follows.
HCl ⇒ H + + Cl ^-
In the case where the etching solution is a mixed acid of HF and HCl, a sufficient amount of H ⁺ is present due to the ionization of HCl, so that the balance of HF ⇔ H ⁺ + F ⁻ is closer to the left side. That is, the amount of free F ⁻ is reduced. Furthermore, since Cl ⁻ acts as a counter ion for Ca ²⁺ , Mg ²⁺ , Sr ^{2+, and} Ba ²⁺ , it is considered that precipitates such as CaF ₂ , MgF ₂ , SrF ₂ , and BaF ₂ are less likely to be generated. Due to the above effects, the amount of F that does not contribute to etching decreases, and the etching rate is unlikely to decrease. Therefore, it is suitable for process management. Therefore, in the present invention, it is essential to contain HCl.

  Using the etching method described above, an ultra-thin display device such as a TFT-LCD or an OLED can be formed. FIG. 2 shows a schematic cross-sectional view of the liquid crystal cell 2. The liquid crystal cell 12 includes a TFT array substrate 21 (active element substrate) each having an alkali-free glass substrate and a color filter (CF) substrate 20. There are types of TFT, such as TN (Twisted Nematic), VA (Virtical Alignment), and IPS (In-Place-Switching).

  As in the etching apparatus 10 shown in FIG. 1, the etching tank 14 is filled with the etching solution 11 having the above composition, the liquid crystal cell 12 to be etched is supported on the support device 13, and immersed in the etching solution 11. Etching is performed while the etching solution is sufficiently stirred by the stirring device 15 so that unnecessary products do not adhere to the glass substrate surface. After a lapse of time according to the desired etching amount, the liquid crystal cell is pulled up, the whole is cleaned, and then necessary inspection is performed. In this way, an ultra-thin display device can be stably manufactured. In addition, when performing etching according to the present invention, the etching tank is replenished with an etching solution for composition adjustment prepared in advance while monitoring the state of the etching solution so that the HF and HCl contents are kept substantially constant. It is preferable.

  In the present invention, etching is based on immersion in an etching bath. At that time, it is preferable to perform bubbling and stirring in the etching solution being immersed. Alternatively, in order to prevent unnecessary products from adhering to the glass substrate surface, it is preferable to spray an etching solution onto the glass substrate surface. Alternatively, it is preferable to swing or rotate the glass substrate in an etching solution in which the glass substrate is immersed.

  FIG. 2 schematically shows a state before and after thinning the both surfaces of the glass substrate by etching according to the present invention. In the figure, the detailed structure of the liquid crystal cell is omitted. The periphery of the glass substrate is sealed with a sealant, and driving elements and color filters are formed inside the cell and filled with a liquid crystal substance. The interior space of the liquid crystal cell is sealed and separated from the outside.

  In general, since a multi-mapping method for forming a large number of liquid crystal cells on a large mother glass substrate is adopted, the mother glass substrate or a multi-substrate obtained by dividing a part of the mother glass substrate is also used when performing the etching method of the present invention. This is advantageous in terms of production process. Alternatively, etching can be performed in units of one liquid crystal cell. When performing the etching, a protective member is provided so that the peripheral portion of the liquid crystal cell is not affected by the etching solution.

  In the example of FIG. 2, the glass surfaces after the etching according to the present invention are shown as etching end surfaces 30 and 31. If the same kind of non-alkali glass substrate is provided and etching is performed with the etching conditions in the etching tank being substantially uniform, the same etching amount can be obtained on the glass substrates on both sides.

Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2008-166537 filed on June 25, 2008, the contents of which are incorporated herein by reference.

  According to the present invention, it is possible to reduce the volume sedimentation rate of the precipitate generated by the reaction between the etching solution and the alkali-free glass substrate (35% by volume or less). Furthermore, the haze of the glass substrate surface can be reduced (haze value is 1 or less), and the surface of the glass substrate can be etched at a high etching rate (1.3 μm / min or more). Therefore, it is suitable for the etching process aiming at thinning of a glass substrate, for example, the etching process of the glass substrate for thinning a display device. In particular, it is suitable for etching processing of glass substrates for small and medium-sized LCDs and OLEDs typified by portable display devices such as mobiles, digital cameras and mobile phones.

10: Etching device 11: Etching solution 12: Liquid crystal cell 13: Support device 14: Etching tank 15: Stirring device 20: CF substrate 21: TFT array substrate (active element substrate)
30: End surface of etching 31: End surface of etching

Claims (14)

A method of etching the surface of an alkali-free glass substrate containing one or more metals selected from the group consisting of Ca, Sr, Ba and Mg,
An etching method in which the surface of the alkali-free glass substrate is etched using an etchant in which HF and HCl satisfy the conditions of formula (A), formula (B), or formula (C) and do not contain NH ₄ F. .
HF: 5% by mass to less than 20% by mass, and HCl: 9% by mass or more (A)
HF: 20% by mass to less than 30% by mass, and HCl: 5% by mass or more (B)
HF: 30% by mass or more and HCl: 2% by mass or more (C)   The etching method according to claim 1, wherein the alkali-free glass substrate is a color filter substrate in which a transparent electrode and a color filter are provided on one surface of the glass substrate.   The etching method according to claim 1, wherein the alkali-free glass substrate is an active element substrate in which a transparent electrode and an active element are provided on one surface of the glass substrate.   The etching method according to claim 1, wherein etching is performed after the non-alkali glass substrate and another glass substrate are combined to face each other to form a display cell in which an internal circuit is sealed.   The etching method according to claim 4, wherein the other glass substrate is an alkali-free glass substrate.   The etching method according to claim 4, wherein the glass substrates on both sides of the display cell are the alkali-free glass substrates, and the outer surfaces thereof are etched simultaneously. The etching method according to any one of claims 1 to 6, wherein the alkali-free glass substrate satisfies a condition of the following composition (1) in terms of an oxide-based mass percentage.
SiO _2: 50-66 _{wt%, Al} 2 O 3: _{10.5~22 wt%, B} 2 O 3: _1~12 wt%, MgO: 0 to 8 mass%, CaO: from 0 to 14.5% by weight , SrO: 0 to 24% by mass, BaO: 0 to 13.5% by mass, MgO + CaO + SrO + BaO: 9 to 29.5% by mass (1) The etching method according to any one of claims 1 to 6, wherein the alkali-free glass substrate satisfies a condition of the following composition (2) in terms of an oxide-based mass percentage.
SiO _2: 58 to 66 _{wt%, Al} 2 O 3: _{15~22 wt%, B} 2 O 3: _5~12 wt%, MgO: 0 to 8 mass%, CaO: 0 to 9 wt%, SrO: 0 .5 to 12.5% by mass, BaO: 0 to 2% by mass, MgO + CaO + SrO + BaO: 9 to 18% by mass (2) The etching method according to any one of claims 1 to 6, wherein the alkali-free glass substrate satisfies a condition of the following composition (3) in terms of an oxide-based mass percentage.
SiO _2: 50 to 61.5 _{wt%, Al} 2 O 3: _{10.5~18 wt%, B} 2 O 3: _7~10 wt%, MgO: 2 to 5 wt%, CaO: 0 to 14.5 Mass%, SrO: 0 to 24 mass%, BaO: 0 to 13.5 mass%, MgO + CaO + SrO + BaO: 14.5 to 29.5 mass% (3)   The etching method according to claim 1, wherein etching is performed while maintaining the temperature of the etching solution at 20 to 60 ° C.   When etching, bubbling into the etchant dipping the glass substrate, spraying the etchant on the surface of the glass substrate, stirring the etchant dipping the glass substrate, and in the dipped etchant The etching method according to claim 1, wherein at least one operation selected from the group consisting of rocking or rotating the glass substrate is performed.   The etching method according to claim 1, wherein the glass substrate is etched at an etching rate of 1.3 μm / min or more.   The etching method according to any one of claims 1 to 12, wherein an etching solution for composition adjustment is replenished so as to keep the HF and HCl contents substantially constant while etching the alkali-free glass substrate. .   The display device provided with the glass substrate processed with the etching method of any one of Claims 1-13.

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