JP5998030B2 - Glass for solar cell or display and method for producing the same - Google Patents

Description

  The present invention relates to glass for solar cells or displays and a method for producing the same. In particular, the present invention relates to a cover glass disposed on an incident light side of a solar cell, a glass disposed on a front surface of a display, and a method for manufacturing these.

  From the viewpoint of reducing the burden on the environment, solar cells that generate clean energy have attracted attention. As a cover glass of a solar cell, a template glass is often used. The irregularities on the surface of the template glass exhibit an antiglare function that scatters incident light. With this function, the template glass prevents the residents of the surrounding buildings from feeling dazzled by the reflected light from the solar cells. The template glass also prevents the surrounding scenery from being reflected in the cover glass and damaging the beauty of the building where the solar cells are installed.

  The cover glass of a solar cell is also required to have a reflection suppression (anti-reflection) function in order to increase the amount of light incident on the photoelectric conversion unit. In order to realize this function, generally, irregularities smaller than the irregularities on the surface of the template glass are suitable. In order to impart a reflection suppressing function, it has been proposed to form a low reflection film composed of silica fine particles and a binder on the surface of a glass plate (for example, Patent Document 1).

  In recent years, the demand for weight reduction has become more prominent for solar cells. This is because the structure of the support for installing the solar cell can be simplified if it is a lightweight solar cell, and the support (for example, the roof of a gas station) that is not designed in consideration of placing a heavy object is used. It is because it becomes easy to install also on the top.

  On the other hand, display glasses used in the liquid crystal screens of smartphones and tablet terminals also require an anti-glare function to prevent surrounding reflections and make it easier to see, and at the same time increase the amount of incident light from the light source of the liquid crystal unit. Therefore, a reflection suppressing function is required.

JP 2001-278737 A

  In order to reduce the weight of solar cells and displays, it is desirable to make the glass thinner. However, the roll-out method used for mass production of template glass is not suitable for the production of thin glass plates, specifically glass plates having a thickness of less than 3 mm. The glass plate which has it cannot be manufactured. On the other hand, as a manufacturing method suitable for mass production of a thin glass plate, there are a float method and a fusion down draw method. However, it is difficult to mass-produce thin glass plates having controlled surface irregularities using these manufacturing methods.

  If a low reflection film composed of silica fine particles and a binder is formed on a glass plate having a thin and smooth surface obtained by a float process or the like, at least a reflection suppressing function can be imparted. However, in this case, there is a problem with the strengthening treatment to be performed in order to compensate for the insufficient strength of the thin glass plate and to provide practical strength as glass. The air-cooling tempering treatment often used for automobile window glass cannot be applied to thin glass plates (even if applied, sufficient strength cannot be obtained). For this reason, in order to reinforce a glass plate that is as thin as described above, that is, a thickness of less than about 3 mm, it is necessary to perform a chemical strengthening process involving ion exchange on the glass surface. Since ion exchange cannot be performed on the glass surface after the low reflection film is formed, the surface of the thin glass plate is first subjected to a chemical strengthening treatment, and then the low reflection film is formed.

  As described in detail in Patent Document 1, a low reflection film composed of silica fine particles and a binder is formed by a so-called sol-gel method. In order to impart a practically desired strength to the low reflection film formed by the sol-gel method, the binder needs to be fired at a high temperature of about 600 ° C. or higher. However, when heated to such a high temperature, the ions introduced in the vicinity of the glass surface by the chemical strengthening treatment diffuse, and the improved strength decreases. As described above, the sol-gel method and the chemical strengthening treatment for forming the low reflection film are not compatible with each other when applied to the same glass plate surface. For this reason, it is difficult to provide a thin glass plate with practical strength and a reflection suppressing function by silica fine particles.

  Further, since the particle diameter of the silica fine particles suitable for the reflection suppressing function is different from the particle diameter of the silica fine particles suitable for the antiglare function, it is not easy to impart both functions using the silica fine particles. When silica particles with a relatively small particle size and suitable for suppression of reflection and silica particles with a relatively large particle size and suitable for anti-glare are arranged in the same region of the surface of the glass plate, the silica particle with a small particle size is This is because it is buried between large silica fine particles and unevenness due to the small silica fine particles hardly appears.

  In spite of this, demand for solar cell cover glass and display glass that have been provided with an antiglare function in addition to a reflection suppressing function while being reduced in weight is increasing. Therefore, the present invention aims to provide a method suitable for manufacturing glass for solar cells or displays having a thin glass plate that has been chemically strengthened while having an antiglare function and a reflection suppressing function, Furthermore, it aims at providing the glass for solar cells or the display excellent in both the glare-proof function and the reflection suppression function obtained by this method.

  In the present invention, the silicofluoride salt is obtained by bringing an etching solution containing hydrofluoric acid and fluoride salt into contact with the surface of a glass plate having a thickness of 0.1 mm to 1.5 mm and containing silicon oxide. Etching process for eroding the surface and depositing irregularities on the surface while depositing on the surface, deposit removing process for removing the silicofluoride salt adhering to the surface of the glass plate, and deposit removing process The manufacturing method of the glass for solar cells or a display which comprises the reinforcement | strengthening process of chemically strengthening the said glass plate implemented after.

  The present invention includes a glass plate having a thickness of 0.1 mm to 1.5 mm and containing silicon oxide, and the surface of the glass plate is subjected to an etching process to have irregularities and is subjected to a chemical strengthening process to be compressed. A haze ratio for incident light in a wavelength range of 380 nm to 1100 nm incident on the surface on which the unevenness is formed is 10% or more due to scattering of incident light due to the unevenness, and the unevenness is formed. The wavelength range that is incident on the surface of the glass plate, except that the transmittance for incident light in the wavelength range of 380 nm to 1100 nm that is incident on the surface is the same as that of the glass plate except that the unevenness and the compressive stress layer are not included. The glass for solar cells or display is higher by 0.1% or more than the transmittance for incident light.

  According to the method of the present invention, irregularities suitable for providing both the antiglare function and the reflection suppressing function can be formed on the surface of the glass plate by etching treatment. In the etching process using only hydrofluoric acid (hydrofluoric acid), the unevenness does not increase to such an extent that the antiglare function is sufficiently exhibited. The silicic acid salt deposited on the surface of the glass plate is thought to contribute to increasing the unevenness to such an extent that the erosion of the surface of the glass plate by the etching process proceeds non-uniformly and an anti-glare function can be obtained. It is done. The etching process that proceeds while depositing the silicic acid salt makes it possible to form irregularities that exhibit the anti-glare function and the anti-reflection function.

  The silicofluoride salt deposited on the surface of the glass plate hinders the uniform formation of the compressive stress layer introduced by ion exchange on the surface in the chemical strengthening treatment. For this reason, the silicofluoride salt is removed from the surface of the glass plate before the chemical strengthening treatment. A compressive stress layer having excellent uniformity is formed on the surface of the glass plate by the chemical strengthening treatment performed after removing the silicofluoride salt. This compressive stress layer gives the thin glass plate the practical strength required in applications as solar cell or display glass. When the etching process is performed after the chemical strengthening process, a part of the compressive stress layer introduced by the chemical strengthening process is lost. However, when the chemical strengthening process is performed after removing the silicic fluoride salt deposited after the etching process, the compressive stress layer is compressed. The stress layer remains without being cut. According to the present invention, it is possible to prevent a decrease in the strength improvement effect due to the introduction of the compressive stress layer. In the method of the present invention, since the irregularities are formed not by the precipitated silicofluoride salt but by erosion of the surface of the glass plate, the antiglare function and the reflection suppressing function are lost even if the silicofluoride salt is removed. There is nothing.

  According to the present invention, there is provided a glass for a solar cell or a display which exhibits an antiglare function to such an extent that the haze ratio is 10% or more and exhibits an antireflection function to an extent that the transmittance is 0.1% or more. Can be provided. Here, the object of the comparison of the transmittance is specifically a glass plate having the same composition and the same thickness in which the unevenness and the compressive stress layer are not introduced on the surface of the glass plate, more specifically, a chemical strengthening treatment. It is a glass plate with the same composition and the same thickness having a smooth surface. As will be described later, the increase in the transmittance may be reduced by the chemical strengthening process performed after the etching process. However, even if this is taken into consideration, if the increase ΔT1 in transmittance due to surface irregularities when compared with that before the etching treatment is set to 0.5% or more, the increase ΔT2 in transmittance after the strengthening process is obtained. It is possible to make it 0.1% or more. In addition, in order to exclude the influence of the silicofluoride salt adhering to the surface, the increase width ΔT1 due to the surface unevenness is specified by measuring the silicic acid salt together with the haze ratio due to the surface unevenness. become.

It is a perspective view which shows one form of the glass by this invention with the partial enlarged view of the main surface. It is a figure which shows an example of the surface roughness curve of a glass surface. It is a figure which shows the state which observed the main surface of the glass produced by Example 1 using the scanning electron microscope (SEM). It is a figure which shows the state which observed the main surface of the glass before the chemical strengthening process after the etching process in Example 1 using SEM. It is another figure which shows the state which observed the main surface of the glass before the chemical strengthening process after the etching process in Example 1 using SEM. It is another figure which shows the state which observed the main surface of the glass before the chemical strengthening process after the etching process in Example 1 using SEM. It is another figure which shows the state which observed the main surface of the glass before the chemical strengthening process after the etching process in Example 1 using SEM.

  In solar cells, an antiglare function and a reflection suppression function are mainly required in a wavelength range from the visible range to the near infrared range, typically in a wavelength range of 380 nm to 1100 nm. Also in display glass, importance is placed on the antiglare function and the reflection suppression function in the visible range. Therefore, it is appropriate to evaluate optical characteristics in a wavelength range of 380 nm to 1100 nm as glass used for a solar cell or a display. In view of this, “light” in the present specification basically targets light within the above wavelength range.

  FIG. 1 shows an example of the glass according to the present invention. The glass 10 is composed of a glass plate 1 that has been subjected to etching treatment and chemical strengthening treatment. The glass plate 1 has a thickness of 0.1 mm to 1.5 mm, preferably 0.3 mm to 1.1 mm. The thickness of the glass plate 1 is prescribed | regulated by the distance between a pair of main surfaces 11 and 12, and an exact value can be measured using a micrometer, for example. The main surfaces 11 and 12 are surfaces having the largest area among the surfaces of the glass plate 1.

  The main surfaces 11 and 12 have surface irregularities formed by an etching process. The surface irregularities include two types of irregularities that clearly differ in parameters such as height and period that characterize the irregularities. Hereinafter, the unevenness 20 described by relatively large parameters may be referred to as “long-period unevenness”, and the unevenness 30 described by relatively small parameters may be referred to as “short-period unevenness”. According to the etching process to be described later, these irregularities 20 and 30 can be formed in a superimposed manner in the same region, not in different regions.

  The long-period unevenness 20 is a surface texture formed by retreating the main surface 11 by an etching process, and includes a convex portion 21 and a concave portion 22 that forms a space therebetween. The convex portion 21 is not formed by adding a material different from the glass composition constituting the glass plate 1, but is constituted by the glass composition itself. Although the main surface 11 has undergone modification due to the application of etching treatment and chemical strengthening treatment, its composition may be slightly changed (for example, the alkali metal ions on the surface layer of the main surface 11 are eluted to decrease or have different types). In other words, it is basically composed of a glass surface. The long-period irregularities 20 can be formed over the entire main surface 11 that functions as a light incident surface.

  As will be described later, since the short-period unevenness 30 is too small to scatter light, the light scattering on the main surface 11 is considered to be substantially caused by the long-period unevenness 20. On the other hand, since the long-period unevenness 20 is too large to form the pseudo optical layer, it is considered that the light reflection suppression at the main surface 11 is substantially caused by the short-period unevenness 30. However, the long-period irregularities 20 may also contribute to suppression of reflection of incident light through multiple scattering of light, enlargement of the surface area of the glass surface, and the like depending on the shape and the like. The light incident on the main surface 11 is incident on the inside of the glass plate 1 while being subjected to the change of the optical path by the long-period irregularities 20 or is reflected (in other words, scattered). The degree of light scattering due to surface irregularities is generally evaluated based on the haze ratio, and the higher the haze ratio, the higher the degree of light scattering and the better the antiglare effect. As is well known, the haze ratio is a ratio of diffuse light transmittance to total light transmittance.

  Due to the long-period irregularities 20 on the main surface 11, the haze rate Hz of light incident on the main surface 11 is, for example, 10% or more, preferably 30% or more, more preferably 35% or more, still more preferably 40% or more, and particularly preferably Can be increased to 50% or more, most preferably 60% or more. Although there is no particular reason for limiting the upper limit of the haze rate, the haze rate Hz is, for example, 95% or less, and further 90% or less.

The average height H _av of the convex portions 21 constituting the long-period irregularities 20 is 0.1 μm to 5.0 μm, preferably 0.2 μm to 3.0 μm, and more preferably 0.3 μm to 2.5 μm. The average bottom length L _av of the convex portion 21 constituting the long-period irregularities 20, 0.2Myuemu～10.0Myuemu, preferably 0.3Myuemu～7.0Myuemu, more preferably at 0.4μm~5.0μm is there.

Here, with reference to FIG. 2, the measuring method of the height H of the convex part 21 and the bottom part length L is demonstrated. FIG. 2 is a profile of the glass surface appearing in the cross section when the main surface 11 is observed from the cross sectional direction of the glass plate 1. This profile can be measured, for example, as a surface roughness curve obtained by scanning the glass surface along a predetermined direction. In FIG. 2, the center line 40 is set according to the area standard. That is, the center line 40 is set such that the peak 41 protruding upward from the center line 40 and the valley protruding downward are of equal area. More specifically, the center line 40 is set so that the total area of the areas defined by the curve and the center line 40 above and below the center line 40 is equal. And regarding the peak part 41 which has an apex above the center line 40 and has a bottom part below the center line 40, the length of the line segment which connects between the bottom parts is made into the bottom part length L, and the apex of the peak part 41 A distance (shortest distance) between the line segment and the line segment is defined as a height H. The average height H _av and the average bottom length L _av are determined by the average value (number average value) of the height H and the bottom length L.

  The peak portion 42 whose top portion is below the center line 40 is often a profile in the vicinity of the lower portion of the bottom of the convex portion 21, and there is a high possibility that the height of the convex portion 21 is not appropriately reflected. For this reason, in the above description, when the height H and the bottom length L are determined, only the peak portion 41 having the top portion above the center line 40 is handled as a convex portion.

  In determining the height H and the bottom length L, it is based on a surface roughness curve having a measurement length of 50 μm (the length of the center line 40 is 50 μm) measured at an arbitrary portion of the main surface 11. The number of peak portions 41 (the number N of convex portions) existing in this length range is preferably 3 to 15, particularly 5 to 10. The surface roughness curve is, for example, a non-contact three-dimensional measuring apparatus of a stage scanning laser probe system (for example, manufactured by Mitaka Kogyo Co., Ltd.) equipped with a laser autofocus microscope for measuring the Z-axis height and a high-precision XYZ stage. NH series).

  The long-period irregularities 20 preferably have the following characteristics. The following parameters are all defined in JIS B0601: 2001, and can be obtained, for example, by measuring the main surface 11 using the above-described non-contact three-dimensional measuring apparatus.

Arithmetic mean roughness Ra: 0.05 μm to 1.0 μm, preferably 0.08 μm to 0.8 μm, more preferably 0.09 μm to 0.5 μm

Maximum height Ry: 0.2 μm to 8.0 μm, preferably 0.3 μm to 7.0 μm, more preferably 0.5 μm to 5.0 μm

Average interval Sm: 0.2 μm to 10.0 μm, preferably 0.3 μm to 8.0 μm, more preferably 0.8 μm to 6.0 μm

  A characteristic shape that is considered to be derived from an etching process to be described later may appear on the individual protrusions 21 constituting the long-period unevenness 20 (see FIG. 1). The convex portion 21 has, on a number basis, a plurality of linear ridge portions 24 that extend downward, with 50% or more, further 70% or more, and in some cases 80% or more, branched downward from the top portion 25 in some cases. And a flat mountainside (slope) 23 that spreads downward with the peak 24 as the upper side.

  Finer short-period irregularities 30 are formed on the glass surface constituting the long-period irregularities 20. In FIG. 1, the short-period unevenness 30 is shown only in the region D, but the unevenness 30 can also be formed over a wide range of the main surface 11 serving as a light incident surface, like the long-period unevenness 20. That is, the glass surface exposed to the main surface 11 can have the long-period irregularities 20 and the short-period irregularities 30 in a superimposed manner in the same area, not individually in different areas.

  Similarly to the long-period unevenness 20, the short-period unevenness 30 is a surface texture made of glass itself, which is formed by retracting the main surface 11 by an etching process. The etching process for forming the short period unevenness 30 need not be performed separately from the etching process for forming the long period unevenness 20. That is, as shown in the examples described later, the long-period irregularities 20 and the short-period irregularities 30 can be formed on the main surface 11 by a single etching process.

  For example, when observing with high magnification using SEM, it may be confirmed that a part of convex part 21 is a flat plate-like surface. This flat surface often extends almost perpendicularly to the thickness direction of the glass plate. This surface is considered to have remained without erosion of the surface by etching due to the thick attachment of the silicofluoride salt. On this plateau-like surface, the short-period irregularities 30 are not normally developed, and in some cases, the flat-period irregularities 30 are smooth.

  Since the height and period of the short-period irregularities 30 are sufficiently smaller than the wavelength of light that is a problem in this specification (see the above-mentioned wavelength range), the glass surface on which the short-period irregularities 30 are formed It is considered to function as a pseudo optical layer having an apparent refractive index smaller than that of the bulk portion. The pseudo optical layer has a refractive index of glass (typical) for light having a wavelength sufficiently larger than the degree of fluctuation due to minute fluctuations at the interface between the glass and a substance in contact with the glass (usually air) in the layer. Specifically, it functions as a low refractive index layer having a refractive index between 1.52) and the refractive index of the substance (1 in the case of air). If the low refractive layer exists in the surface layer of the glass plate, reflection of light incident on the main surface 11 tends to be suppressed. However, referring to the results of various experiments conducted so far, there is a possibility that multiple scattering by the long-period irregularities 20 contributes to suppression of light reflection on the main surface 11. From the degree of the reflection suppression effect actually obtained, it is conceivable that the multiple scattering by the long-period unevenness 20 and the pseudo optical layer by the short-period unevenness 30 synergistically increase the reflection suppression effect.

  Due to the reflection suppressing function derived from the unevenness formed on the main surface 11, it is possible to improve the transmittance of light incident on the main surface 11. The transmittance increase ΔT (ΔT2) in the glass into which the compressive stress layer after the chemical strengthening treatment is introduced is 0.1% or more, preferably 0.2% or more, more preferably 0.3% or more, and particularly preferably 0.8. It can be 5% or more, especially 0.7% or more, and in some cases 1.0% or more. The transmittance increase width ΔT2 is a glass plate similar to the glass plate 1 except that the main surfaces 11 and 12 are smooth surfaces and does not have a compressive stress layer, specifically, etching treatment and chemical strengthening. Evaluation can be made on the basis of a glass plate having the same glass composition and thickness that has not been treated. The “smooth surface” used in the present specification is specifically a so-called “fire-making surface” manufactured by a manufacturing method such as a float method or a fusion down draw method, and subsequent processing (etching processing and strengthening). It refers to a glass surface that has not undergone treatment.

  The haze rate is raised to 10% or more, the surface has irregularities constituted by the glass surface itself with a transmittance increase width ΔT2 of 0.1% or more, and it has a compressive stress layer introduced by chemical strengthening treatment. The glass plate is extremely suitable for solar cell cover glass and display glass because of its antiglare effect, antireflection effect and practical strength.

The diameter DT of the convex part 31 which comprises the short period unevenness | corrugation 30 becomes like this. Preferably it is 20 nm-250 nm, More preferably, it exists in the range of 50 nm-200 nm. Height PV of the convex part 31 which comprises the short period unevenness | corrugation 30 becomes like this. Preferably it is 30 nm-150 nm, More preferably, it exists in the range of 50 nm-100 nm. The number TN of the protrusions 31 is preferably 50 to 2000, more preferably 100 to 1000, per 1 μm ² of the main surface.

  The diameter DT, the height PV, and the number TN can be determined based on observation results with a scanning electron microscope (SEM). The diameter DT of the convex portion 31 is determined by the diameter when the outer edge of the convex portion is regarded as a circle of equal area. Further, the height PV is determined by the method described with reference to FIG. 2 based on the profile obtained from the cross-sectional observation of the main surface of the glass plate by SEM. As this profile, a profile measured over a total length of 0.5 μm along the glass surface is used.

  In addition, in the recessed part 32 which comprises the short period unevenness | corrugation 30 with the convex part 31, the characteristic shape considered to originate in the etching process mentioned later may appear. That is, the recess 32 may be a crater-like depression hole in which the outer edge of the hole appearing on the glass surface is substantially circular.

  Strictly speaking, the “period” that distinguishes the long-period unevenness 20 and the short-period unevenness 30 can be specified by the average value of the interval W (see FIG. 2) of the apexes of the peaks 41 in the surface roughness curve. As the mountain portion 41, as described above, only those having a top portion located above the center line 40 which is an equal area line and a bottom portion located below are selected. In addition, the surface roughness curve about the short period unevenness | corrugation 30 shall use the curve of the measurement length of 0.5 micrometer obtained by cross-sectional observation of the glass surface using SEM.

  The period of the long-period unevenness 20 is on the order of microns, and is, for example, 0.5 μm to 8.0 μm. On the other hand, the period of the short period unevenness 30 is on the order of submicrons, and is, for example, 50 nm to 200 nm. Both the concave and convex portions 20 and 30 can be clearly distinguished because their period and height are different to the above extent.

  The main surface 12 opposite to the main surface 11 serving as a light incident surface is usually a light emission surface. The main surface 12 may be a flat surface on which surface unevenness such as the long-period unevenness 20 and the short-period unevenness 30 is not formed, for example, a smooth surface. And the surface which has the short period unevenness | corrugation 30 may be sufficient. In addition, the main surfaces 11 and 12 of a glass plate are a pair of surfaces which have the largest area in the surface of a glass plate, and the thickness of a glass plate will be decided by the distance between them.

  The production method according to the present invention will be described below. As described above, in this manufacturing method, the etching process, the deposit removal process, and the strengthening process are performed in this order.

  First, a glass plate is prepared. As the glass plate, it is sufficient to use a mass-produced glass plate of general-purpose composition, typically a glass plate (float glass) made of soda lime silica glass manufactured by the float process. However, the glass plate is not limited to this, and a glass plate obtained by various manufacturing methods such as a fusion down draw method may be used. The type of glass plate is not limited to the above, and glass plates having various compositions such as borosilicate glass and aluminosilicate glass can also be used. The glass plate needs to have a glass composition containing silicon oxide in order to supply silicon necessary for the progress of a chemical reaction, which will be described later, and silicon oxide is a main component of a network forming component (a component occupying 50% by mass or more). It is preferable to have a glass composition that is, and it is more preferable to have a glass composition in which silicon oxide is the main component among all the components. The thickness of the glass plate is suitably in the range of 0.1 mm to 1.5 mm in order to reduce the weight of the cover glass. Since unevenness is imparted by the etching treatment, the glass plate is a glass plate in which both main surfaces are smooth surfaces and the haze ratio is less than 1%, further less than 0.5%, particularly less than 0.1%. In particular, it is sufficient to prepare float glass that is mass-produced.

The composition of soda lime silica glass is shown below as an example of the glass composition suitable for the glass plate. Below, the content rate of each component is displayed by the mass%. SiO ₂ : 65-80%
_{, Al 2 O 3: 0~5%} , MgO: 0~10%, CaO: 5~15%, MgO + CaO: 5~15%, Na 2 O: 10~18%, K 2 O: 0~5%, _{Na 2 O + K 2 O:} 10~20%, B 2 O 3: 0~5%, other trace components: 0 to 1%. Here, examples of “other trace components” include colored components represented by Fe ₂ O ₃ and clarified components represented by SO ₃ .

  An etchant (etchant) to be prepared together with the glass plate is prepared containing hydrofluoric acid (hydrofluoric acid) and a fluoride salt. The fluoride salt is preferably at least one selected from potassium fluoride, ammonium fluoride and sodium fluoride. This etching solution can be prepared, for example, by mixing hydrofluoric acid and an aqueous fluoride salt solution.

  In the etching process, erosion of the surface of the glass plate is performed while depositing a silicofluoride salt. For example, when an etching solution containing hydrofluoric acid and potassium fluoride is brought into contact with the surface of the glass plate, the reaction of the formula (1) involving silicon oxide eluted from the glass plate into the etching solution proceeds, and the produced silicon fluoride is generated. Potassium halide precipitates. When the etching solution containing hydrofluoric acid and ammonium fluoride is brought into contact with the glass plate, the reaction of the formula (2) proceeds and the produced ammonium silicofluoride is precipitated. Similarly, when sodium fluoride is used, the reaction of formula (3) proceeds and the produced sodium silicofluoride precipitates.

SiO ₂ + 4HF + 2KF → K ₂ SiF ₆ ↓ + 2H ₂ O (1)
SiO ₂ + 4HF + 2NH ₄ F → (NH ₄ ) ₂ SiF ₆ ↓ + 2H ₂ O (2)
SiO ₂ + 4HF + 2NaF → Na ₂ SiF ₆ ↓ + 2H ₂ O (3)

  When etching proceeds with a silicofluoride salt such as potassium silicofluoride or ammonium silicofluoride deposited on the glass surface, fine irregularities appear on the surface of the glass plate. The fine surface irregularities are also formed in the region where the silicofluoride salt is adhered. From this fact, it is considered that the fine surface irregularities are formed by non-uniform progression of erosion caused by etching by the silicic acid salt adhering to the surface of the glass plate as a porous body.

  Conventionally, minute projections formed on a glass plate by using an etching solution containing hydrofluoric acid and a fluoride salt such as potassium fluoride have been mainly used for manufacturing a magnetic disk substrate. In this application, a minute convex portion having a height of about 5 nm to 70 nm is used as a protrusion for preventing the magnetic head from adhering to the substrate. Since a glass plate as a substrate for a magnetic disk is basically required to have a smooth surface, in the technical field of magnetic disks, the etching process using the etching solution exceeds the above-mentioned minute convex portions. It has been considered appropriate to carry out under conditions such that the convex portions are not formed.

  If etching proceeds further with silicic acid salts such as potassium silicofluoride deposited on the surface of the glass plate, erosion due to etching proceeds non-uniformly according to local differences in the amount of silicic acid salt deposited. However, larger irregularities appear than the fine surface irregularities described above. Thus, when the erosion of the glass surface is further advanced, surface irregularities (long-period irregularities 20) having a relatively large period and long periods are formed together with surface irregularities (short-period irregularities 30) having a relatively small period and a short period. In order to obtain a glass plate having a main surface having both surface irregularities 20 and 30, it is important to apply conditions under which erosion by etching proceeds sufficiently and appropriately on the glass surface to which the deposited silicofluoride salt has adhered. is there. Erosion due to etching is sufficient by comprehensively adjusting the temperature of the etching solution, the time of the etching process, the concentration of hydrofluoric acid and fluoride salt in the etching solution, the composition of the glass plate, etc., taking into account the mutual influences. And it can proceed appropriately.

  The transmittance increase ΔT1 by the etching process is 0.5% or more, further 0.6% or more, particularly 0.8% or more, particularly 1.0% or more, and in some cases 1.3% or more. be able to. By the etching treatment, the haze rate Hz can be increased to 10% or more, further 30% or more, particularly 35% or more, especially 40% or more, in some cases 50% or more, and optionally 60% or more. ΔT1 is the transmittance of the glass plate before the etching process (the glass plate used as a reference for comparison is as described above) and the glass plate after the etching step and the deposit removal step and before the strengthening step This is the increase in transmittance determined by the difference from the transmittance. It should be noted that the haze rate Hz and ΔT1 can be determined only after substantially all of the deposit (silicofluoride salt) has been removed by the deposit removal step.

  The temperature of the etching solution during the etching process is slightly higher than room temperature (20 to 25 ° C.), for example, 28 ° C. or more, and preferably 30 to 35 ° C. The time for the etching process depends on the temperature to be applied, but for example, 10 seconds or more, and further 30 to 600 seconds are appropriate. The concentration of hydrofluoric acid in the etching solution is preferably 1 to 10% by mass. Further, the concentration of a fluoride salt such as potassium fluoride is preferably 10 to 20% by mass. However, the concentration of hydrofluoric acid and fluoride salt should be adjusted as appropriate according to the applied temperature and time.

  By the etching treatment, a silicofluoride salt such as potassium silicofluoride adheres to the glass surface, and in some cases, the entire glass surface is covered with the silicofluoride salt. This silicic acid salt is removed in a deposit removing step performed subsequent to the etching step in which the etching process is performed. The deposit removing process can be performed by, for example, cleaning using a cleaning liquid. As the cleaning liquid, an acidic cleaning liquid, specifically, various acids such as hydrochloric acid, nitric acid, and sulfuric acid are suitable. Surface irregularities 20 and 30 are formed on the glass surface exposed through the deposit removing process. After washing with an acid, the glass surface may be washed with water as appropriate in order to wash away the adhering acid. The glass plate 1 in which the surface irregularities 20 and 30 are formed on the main surface 11 is obtained through a glass plate drying process that is further performed as necessary. If water is used as the cleaning liquid, the attached substances cannot be completely removed unless washing is performed for a long time while applying a physical force. Therefore, the acid exemplified above is suitable as the cleaning liquid.

  In the deposit removing step, it is preferable to remove substantially all of the silicofluoride salt. In the present specification, it is considered that substantially all of the silicofluoride salt has been removed when the presence of the silicofluoride salt is not observed when observed at a magnification of 10,000 using an SEM.

  4A to 4D show examples of the main surface having long-period surface irregularities and short-period surface irregularities formed in the etching process and exposed by the deposit removing process.

  The etching process and the deposit removal process may be applied to both the main surfaces 11 and 12 of the glass plate 1 or only to the main surface 11. In the latter case, the main surface 11 is provided with surface irregularities 20 and 30, and the main surface 12 is held as a smooth surface.

  After the deposit removing process, a chemical strengthening process is performed. The chemical strengthening treatment compresses the surface of the glass plate by exchanging monovalent ions with a relatively small ionic radius contained in the glass plate and monovalent ions with a relatively large ionic radius contained in the treatment liquid. The stress layer itself is a known strengthening treatment. The chemical strengthening process is usually applied to both main surfaces 11 and 12.

A compressive stress layer containing monovalent ions introduced by ion exchange exists on the surface of the chemically strengthened glass plate. The chemical strengthening treatment is generally included in the vicinity of the surface of the glass plate by exchanging alkali metal ions, for example, by replacing lithium ions (Li ⁺ ) contained in the vicinity of the surface of the glass plate with sodium ions (Na ⁺ ). It is carried out by exchanging sodium ions and potassium ions (K ⁺ ), and typically by ion exchange between sodium ions contained in the glass plate and potassium ions contained in the treatment liquid. Examples of the treatment liquid for performing this ion exchange include molten salts of potassium salts represented by potassium nitrate. That is, the chemical strengthening treatment can be preferably performed by immersing the glass plate in a molten salt containing potassium ions and performing ion exchange between potassium ions and sodium ions contained in the glass plate. The conditions of the chemical strengthening treatment, such as the temperature of the molten salt and the dipping time of the glass plate, may be appropriately selected from known conditions. For example, the temperature of the molten salt is 380 to 480 ° C., particularly 380 to 460 ° C. The immersion time is 30 minutes to 1440 minutes. The chemical strengthening treatment is a treatment capable of introducing a compressive stress layer into a thin glass plate, and is suitable as a treatment for imparting practical strength to a glass for a solar cell or a display in which the thin glass plate is used.

  Thus, a glass plate having the characteristic surface irregularities 20 and 30 realized by the above-described etching process and having a main surface into which compressive stress is introduced by ion exchange in the chemical strengthening process is obtained. The shape of the short period unevenness 30 tends to increase its pitch by the chemical strengthening treatment. Since the increase in the transmittance may be slightly reduced by the chemical strengthening process, it is preferable to perform the etching process in anticipation of this decrease. The haze rate often increases slightly due to the chemical strengthening treatment.

  An example of the main surface after the chemical strengthening treatment is shown in FIG.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited by a following example. The evaluation method of characteristics was as follows.

[Haze rate Hz, transmittance T]
Measurement was performed using a spectrophotometer “UV3100” manufactured by Shimadzu Corporation with a measurement wavelength range of 380 to 1100 nm.

[Arithmetic average roughness Ra, maximum height Ry, average interval Sm]
Measurement and analysis were performed using a non-contact three-dimensional measuring device “NH-3N” manufactured by Mitaka Kogyo Co., Ltd.

[Average height H _av , average bottom length L _av , number of protrusions N]
Based on the surface roughness curve obtained by using the non-contact three-dimensional measuring apparatus, it was specified according to the above-described calculation method. The surface roughness curve is obtained by scanning the main surface over a length of 50 μm.

[Diameter DT, convex height PV, convex number TN of (short-period irregularities)]
From the observation result using SEM, it specified according to the above-mentioned calculation method. Here, the diameter DT and the number TN were determined based on the result of observing a 1.2 μm × 0.9 μm region on the main surface at a magnification of 100,000 times. The height PV was determined from a profile obtained by cross-sectional observation of the vicinity of the main surface at a magnification of 100,000 times. This profile was obtained with a measurement length of 0.5 μm.

( Reference Example 1)
As a glass plate to be etched, a soda lime silica glass plate (haze ratio Hz: 0.05%, transmittance T: 89.1%) manufactured by a float method as a glass plate is 5 mass as an etching solution. % Aqueous solutions containing hydrofluoric acid (hydrofluoric acid) and 20% by mass of potassium fluoride were prepared. The etching solution was kept at 30 ° C., and the glass plate was immersed in this etching solution for 30 seconds to carry out the etching treatment. During the etching process, the glass plate was allowed to stand and the etching solution was not stirred. Next, the glass plate taken out from the etching solution was immersed in 5% by mass of sulfuric acid to perform a cleaning process to remove the adhering potassium silicofluoride. During the cleaning process, the glass plate was rocked in sulfuric acid. Furthermore, the glass plate taken out from the sulfuric acid was washed with water to obtain a glass plate having surface irregularities formed on both main surfaces. The haze rate Hz of this glass plate was 32.4%, and the transmittance T was 89.8% (ΔT1: 0.7%).

  Then, the chemical strengthening process was implemented about the glass plate after an etching process. This treatment was performed by immersing the glass plate in molten potassium nitrate maintained at 460 ° C. for 30 minutes. The glass plate taken out from the potassium nitrate molten salt was washed with water to obtain a glass plate having surface irregularities and chemically strengthened. The glass plate after chemical strengthening had a haze ratio Hz of 33.4% and a transmittance T of 89.3% (ΔT2: 0.2%).

(Example 1 )
A glass plate having surface irregularities formed and chemically strengthened was obtained in the same manner as in Reference Example 1 except that the etching treatment time was 2 minutes. In Example 1 , the haze rate Hz of the glass plate after the etching treatment and the cleaning treatment was 72.6%, and the transmittance T was 90.9% (ΔT1: 1.8%). Moreover, the haze rate Hz of the glass plate after the chemical strengthening treatment in Example 1 was 73.6%, and the transmittance T was 90.4% (ΔT2: 1.3%).

( Reference Example 2 )
Except that the concentration of hydrofluoric acid in the etching solution was 1.2% and the concentration of potassium fluoride was 11.6%, a glass plate having surface irregularities formed and chemically strengthened was obtained in the same manner as in Example 1 . . In Reference Example 2 , the haze rate Hz of the glass plate after the etching treatment and the cleaning treatment was 30.8%, and the transmittance T was 90.2% (ΔT1: 1.1%). Moreover, the haze rate Hz of the glass plate after the chemical strengthening treatment in Reference Example 2 was 31.8%, and the transmittance T was 89.7% (ΔT2: 0.6%).

(Comparative Example 1)
A chemically strengthened glass plate was obtained in the same manner as in Example 1 except that the concentration of potassium fluoride in the etching solution was 40%. In Comparative Example 1, the haze rate Hz of the glass plate after the etching treatment and the cleaning treatment was 0.05%, and the transmittance T was 89.1% (ΔT1: 0.7%). Moreover, the haze rate Hz of the glass plate after the chemical strengthening treatment in Comparative Example 1 was 0.05%, and the transmittance T was 88.9% (ΔT2: −0.2%).

(Reference Example 3 )
A glass plate (untreated soda-lime silica glass plate having a thickness of 1.1 mm manufactured by the float process) before performing the etching treatment, the cleaning treatment and the chemical strengthening treatment was used as Reference Example 3 as it was.

(Reference Example 4 )
A chemically strengthened glass plate was obtained in the same manner as in Reference Example 1 except that the etching process and the cleaning process were not performed.

(Example 2 )
Glass having a surface irregularity formed and chemically strengthened in the same manner as in Reference Example 1 except that the concentration of hydrofluoric acid in the etching solution is 5%, the concentration of potassium fluoride is 5%, and the etching treatment time is 10 minutes. I got a plate. In Example 2 , the haze rate Hz of the glass plate after the etching treatment and the cleaning treatment was 83.8%, and the transmittance T was 90.6% (ΔT1: 1.5%). Moreover, the haze rate Hz of the glass plate after the chemical strengthening treatment in Example 2 was 85.0%, and the transmittance T was 90.4% (ΔT2: 1.3%).

(Example 3 )
Glass having a surface irregularity formed and chemically strengthened in the same manner as in Reference Example 1 except that the concentration of hydrofluoric acid in the etching solution is 5%, the concentration of potassium fluoride is 10%, and the etching treatment time is 10 minutes. I got a plate. In Example 3 , the haze rate Hz of the glass plate after the etching treatment and the cleaning treatment was 74.3%, and the transmittance T was 90.8% (ΔT1: 1.7%). Moreover, the haze rate Hz of the glass plate after chemical strengthening treatment in Example 3 was 76.0%, and the transmittance T was 90.6% (ΔT2: 1.5%).

Table 1 shows the conditions for the etching process. Moreover, the measurement result about each Example after implementing a chemical strengthening process, each comparative example, and each reference example is put together in Table 2, and is shown. However, for each of the comparative examples and the reference examples 3 and 4 , since the surface unevenness was not substantially formed, the measurement related to the unevenness was not performed.

When the glass plates obtained in Reference Examples 1 and 2 and Examples 1 to 3 were observed by SEM, long-period surface irregularities and short-period surface irregularities were formed on the main surface. The observation result by SEM of the glass plate obtained by Example 1 is shown as FIG. Moreover, the observation result by SEM of the glass plate after the washing process in Example 1 is shown as FIGS. In Example 1 , the period of the long-period irregularities determined according to the method described above was 3.2 μm, and the period of the short-period irregularities was 80 nm. Moreover, it has confirmed that the silicofluoride (potassium fluoride) was removed by the washing process.

Although the transmittance T is slightly reduced by the chemical strengthening treatment (Reference Example 4 ), it can be seen that an increase in the transmittance T that can sufficiently compensate for this reduction can be obtained by providing appropriate unevenness by the etching treatment. ( Reference examples 1-2, each Example). In Comparative Example 1, it was considered that the unevenness was hardly formed because the etching reaction for eroding the glass surface did not proceed sufficiently because the concentration of potassium fluoride was too high.

Etching treatment similar to that in Reference Example 1 was performed except that ammonium fluoride was used instead of potassium fluoride. Further, etching similar to that in Reference Example 1 was performed except that sodium fluoride was used instead of potassium fluoride. When the treatment was performed, it was confirmed that both long-period surface irregularities and short-period surface irregularities were formed in the same manner as in Reference Example 1.

(Application examples)
Two glass plates (681 mm × 979 mm) obtained in the same manner as in Reference Example 1 were prepared. A resin intermediate film (ethylene-vinyl acetate copolymer (EVA)) was placed on one surface of the glass plate, and silicon solar cells connected by lead wires were evenly arranged on the intermediate film. . Next, the resin intermediate film was placed on the solar cell, and the other glass plate was placed on the intermediate film. The surface of the glass plate in contact with the intermediate film was previously wiped with ethanol. The laminated body thus obtained was temporarily fixed with a tape and then integrated by heating while vacuuming, and then kept at 160 ° C. for defoaming and the like to produce a laminated glass. After cooling, remove the tape, and then insert an aluminum frame filled with hot-melt butyl into the ends of the four sides of the laminated glass, screw the aluminum frame, and transmit light from between the solar cells. The solar cell module was obtained. When the load resistance test prescribed | regulated to IEC61215 "10.16 Mechanical load test" was implemented about this solar cell module, neither glass breakage nor the output fall was observed and it has confirmed that it passed the test.

DESCRIPTION OF SYMBOLS 1 Glass plate 10 (for solar cells or displays) Cover glass 11, 12 Main surface 20 Long period unevenness 21,31 Convex part 22,32 Concavity 23 Mountainside part 24 Peak part 25 Top part 30 Short period uneven part 40 Center line 41,42 Yamabe

Claims (6)

A glass plate having a thickness of 0.1 mm to 1.5 mm and containing silicon oxide;
The surface of the glass plate is subjected to etching treatment and has irregularities, and subjected to chemical strengthening treatment and has a compressive stress layer,
The haze ratio for incident light in a wavelength range of 380 nm to 1100 nm incident on the surface on which the unevenness is formed by scattering of incident light due to the unevenness is 60 % or more,
The surface of the glass plate having the same transmittance as that of the glass plate except that the transmittance with respect to the incident light having a wavelength range of 380 nm to 1100 nm incident on the surface on which the unevenness is formed does not include the unevenness and the compressive stress layer. 1.0 % or more higher than the transmittance for incident light in the wavelength range incident on
Glass for solar cell or display. A method for producing the solar cell or display glass according to claim 1,
By bringing an etching solution containing hydrofluoric acid and fluoride salt into contact with the surface of a glass plate having a thickness of 0.1 mm to 1.5 mm and containing silicon oxide, silicofluoride salt is deposited on the surface. However, an etching step of eroding the surface and imparting irregularities to the surface;
An adhering matter removing step for removing the silicofluoride salt adhering to the surface of the glass plate;
A strengthening step for chemically strengthening the glass plate, which is performed after the deposit removing step;
Comprising
In the etching step, a haze ratio for incident light in a wavelength range of 380 nm to 1100 nm incident on the surface after performing the strengthening step is 60% or more, and enters the surface after performing the strengthening step. The irregularities are formed on the surface such that the transmittance for incident light in the wavelength region is 1.0% or more higher than the transmittance for incident light in the wavelength region incident on the surface before performing the etching step. The manufacturing method of the glass for solar cells or a display to develop. The manufacturing method of the glass for solar cells or a display of Claim 2 which removes the said silicofluoride salt by wash | cleaning the said surface of the said glass plate using an acidic washing | cleaning liquid in the said deposit | attachment removal process. The manufacturing method of the glass for solar cells or display of Claim 2 or 3 which removes substantially all of the said silicofluoride salt in the said deposit | attachment removal process. The method for producing a cover glass for a solar cell or a glass for display according to any one of claims 2 to 4, wherein the fluoride salt is at least one selected from potassium fluoride, ammonium fluoride, and sodium fluoride. In the strengthening step, the glass plate is immersed in a molten salt containing potassium ions, and a compression stress layer is formed on the surface of the glass plate by ion exchange between the potassium ions and sodium ions contained in the glass plate. The manufacturing method of the glass for solar cells in any one of claim | item 2 -5 or display.