TWI520921B - Impact-damage-resistant glass sheet - Google Patents

Description

Glass sheet resistant to impact damage

The products and methods of the present disclosure are broadly related to tempered glass sheets, and in particular to glass sheets exhibiting high resistance to flexural stress and impact damage.

Cover glass for consumer electronic devices including mobile phones, PDAs, desktop/laptop/notebook computers, and LCD and plasma TVs is highly demanding today. The performance attributes of such sheets that can be highly evaluated by designers, producers, and end users of such devices include low thickness, high surface strength and scratch resistance, as well as high resistance to flexural stress and impact damage.

A commonly accepted method for assessing the resistance of a cover glass to impact damage, such as cracking or comminution, includes standardized flexural (bending) stress and ball drop (shock) testing. The ball drop test requirements are quite high and, without tight control of the glass quality, a wide range of impact damage resistance can be exhibited on even a single commercial cover glass sheet line. Therefore, the tightly distributed ball fall failure performance is as important as the damage resistance at higher ball drop heights.

Although the ball drop test is widely used in both system and component level tests, the glass properties that affect the ball drop performance are quite complicated. For example, in general it is expected and observed at higher ball drop heights, and/or reduced cover glass thickness or sheet strength, the failure rate will increase, but for common manufacturing sources, nominal thicknesses and equivalent bends The failure rate variability of a piece of glass with a folding strength at a single ball drop height has been the main issue.

In addition, the glass intensification method, which is extremely effective for the improvement of the sheet glass impact damage, is still likely to produce a sheet exhibiting extensive strength variability in a flexural test designed to evaluate the bending modulus of the glass breaking strength. For example, biaxial or toroidal ring flexural strength tests performed on a glass sample that has been pretreated to improve damage resistance may result in widely varying flexural strength results.

In accordance with the present disclosure, the problem of varying degrees of surface strength in a thin glass sheet can be addressed by providing a glass surface chemical treatment that significantly improves the biaxial flexural strength and impact damage resistance. Therefore, the consumer electronic device incorporating the thin cover sheet of the treated glass, especially the large-area cover sheet for LCD and plasma TV display screens, extends to the handheld electronic device, and can be used for The damage that may be encountered by the impact and flexural stress on the surface exhibits a greatly improved and more consistent impedance.

Thus, in a first feature, the present disclosure provides a glass sheet having impact damage resistance that contains at least one adapted and chemically etched surface and exhibits a standardized 128g ball fall failure height of at least 120 cm. To provide this performance, the glass sheet incorporates a surface compression layer having a depth of at least 8 microns and a surface compressive stress value of at least 200 MPa.

In particular, a specific embodiment of the present disclosure provides a thin, damage-resistant aluminum silicate glass sheet comprising at least one chemically etched, compressively stressed surface, wherein the value of the compressive stress at the surface is at least 400 MPa and the surface compression layer (DOL) The depth is at least 15 microns.

In still further embodiments, the present disclosure provides a thin, damage-resistant alkali metal silicate glass sheet comprising at least one chemically etched, compressively stressed surface, wherein the value of the compressive stress at the surface is at least 400 MPa and the surface is compressed The layer (DOL) has a depth of at least 30 microns.

The chemically etched surface can be an acid etched surface. In the ball drop test, it was found that a thin acid etched alkali metal silicate glass sheet having these characteristics exhibited a standardized ball drop failure height of at least 140 cm, or at least 180 cm, while a failure height in the range of 300 cm was observed. It is at a higher surface compression value and compression layer depth.

For the purposes of this disclosure, a thin glass sheet is a sheet of glass having a thickness of no more than 2 mm. An alkali metal aluminosilicate glass sheet refers to a glass sheet composed of a main (not more than 50% by weight) glass containing cerium oxide and aluminum oxide, which contains sufficient exchangeable alkali metal to be lower than The ion exchange strengthening treatment (chemical conditioning) is carried out at the temperature of the strain point of the glass to develop a surface compressive stress exceeding 500 MPa.

A particularly important embodiment of the damage resistant glass sheet disclosed herein comprises an alkali metal silicate glass sheet having a uniform thickness of no more than 1.5 mm, or even 1.0 mm. For such embodiments, the surface of the sheet will typically comprise a surface compression layer having a coating depth (DOL) of at least about 30 microns, or at least about 40 microns, and the surface of the sheet within the surface compression layer. The compressive stress value is at least about 500 MPa, or at least about 600 MPa.

In still another feature, the present disclosure provides a video display device including a reinforced glass cover sheet, wherein the glass cover sheet has a thickness in the range of 0.2 to 2 mm, an alkali metal silicate glass composition, and at least one A surface compression layer having a chemically etched surface is incorporated. The present disclosure incorporates a number of specific embodiments wherein the surface compressive layer incorporates an acidic etched surface and has a depth of at least 30 microns and a surface stress value of at least 500 MPa. At the same time, the present disclosure also incorporates a number of embodiments in which a surface compressive layer incorporating the acidic etched surface is applied to at least the back or non-exposed surface of the glass cover sheet.

In still another feature, the present disclosure provides a method of making a tempered glass sheet comprising the steps of (i) subjecting at least one surface of the glass sheet to an adaptation treatment to develop a compressible surface layer thereon, and Ii) contacting at least one surface of the glass sheet with a chemically etched medium, such as an acidic etch medium, to remove a slight thickness of the surface layer of glass therefrom. In a particular embodiment of the present disclosure, at least one surface of the glass sheet is joined The step of contacting is for time and temperature effective to remove surface glass of no more than 4 microns from the sheet, or surface glass of no more than 2 microns.

A plurality of specific embodiments are specifically incorporated within the scope of the present method, wherein the glass sheet possesses an alkali metal ruthenate composition, and wherein the glass sheet to be adapted and etched is preselected to have at least one Surfaces that do not contain surface crucibles that are more than about 2 microns deep. In the case of an alkali metal silicate glass starting sheet, the conditioning treatment can be selected from the group consisting of thermal conditioning and chemical conditioning, and the etching medium can be an aqueous medium containing a fluid compound.

10‧‧‧Video display device

12‧‧‧Video display

14‧‧‧Adhesive layer

16‧‧‧ Cover Sheet

12a‧‧‧ display surface

16a‧‧‧Back surface

The products and methods of the present disclosure will be further described with reference to the accompanying drawings, in which: FIG. 1 is a drawing showing normalized ball drop test data for a first set of glass piece samples; FIG. 2 is a view showing a second set of glass The second pattern of the normalized ball drop failure data for the sample; Figure 3 is a diagram showing the normalized biaxial flexural strength data for the two sets of glass samples; Figure 4 is for the glass sample with the tantalum surface, point A plot of glass flexural strength versus enthalpy depth is plotted; Figure 5 is a graph showing normalized biaxial flexural strength data for three sets of tempered glass specimens; Figure 6 is a diagram showing the 4-point bending flexural strength data for two sets of reinforced glass sheet samples; and Figure 7 is a side cross-sectional schematic view of a video display device incorporating a tempered glass cover sheet.

The methods and products provided in accordance with the present disclosure, although widely applicable to a variety of product and product manufacturing processes, can be applied to the manufacture of cover glass sheets for use in incorporating displays for consumer electronic devices to achieve particular advantages. Thus, reference may be made specifically to such cover glass to exemplify specific examples and specific embodiments of such products and methods presented hereinafter, even if the methods and uses of the invention are not limited thereto.

Ion exchange reinforced aluminosilicate glass can be used in a variety of display overlay glass applications for a wide range of consumer electronic devices where high surface strength and resistance are required for surface damage. However, these current ion exchange strengthened glass sheets exhibit only limited, or at least undesirably, variability in resistance to impact damage and/or flexural stress failure. This issue is particularly important as the number and variety of consumer electronic devices increase and the environment in which such devices are used becomes more unfavorable.

As a result of the higher and more consistently standardized ball drop test results, it has been found that the chemical adaptation (ion exchange) treatment combined with the simple acid treatment of the glass cover sheet can significantly improve the thin aluminum silicate glass sheet. Impact damage resistance. For the purposes of this case, the standardized ball drop test is a ball with a standard size and weight, that is, A stainless steel sphere having a diameter of 31.75 mm and a weight of 128 grams was repeatedly dropped from the incremental height on a square piece of glass having an outer dimension of 50 x 50 mm until the sample of the glass piece was broken.

The traditional mechanical finishing procedure used to improve the surface finish of thin-adjusted glass sheets does improve ball drop impact resistance in some cases. However, there is no single mechanical means to impart consistent and effective results to various glass components and/or various glass shapes. At the same time, no mechanical finishing treatment can reduce the randomization effect on the shape of the glass and the shape and shape of the defect on the impact resistance or flexural strength of the glass. The use of chemical surface treatments that involve contacting one or both of the glass sheets with an acid glass etch medium provides considerable flexibility, is adaptable for most glasses, and can be applied to flat and complex overlays in a timely manner. Glass sheet geometry both. In addition, it has been found that even in glass having a low degree of surface flaws, especially including caps that are conventionally considered to be substantially free of surface imperfections during manufacturing or post-manufacturing processes or The squat (ie, melted) glass flakes are indeed effective in reducing strength variability.

With micro thickness (thickness The ball drop performance of the 2mm) glass cover sheet exhibits a particularly high degree of variation, and a large difference in impact damage resistance can be observed, even in a lower sheet with a smooth molten surface in a given treatment batch. with. For example, for a given set of test conditions, the height of the ball fall failure in a single pull sheet batch can range from as low as 20 cm to over 120 cm, ie up to six times the variability.

As shown by these results, improving the impact damage resistance of the thin glass cover sheet will require an increase in the low end of the failure height profile. End, and reduce the overall degree of change in these results. If the parent contains a member exhibiting an unacceptably low resistance to impact damage, the improvement in the average ball fall failure height of the product matrix is of little value. The chemical surface treatment method is particularly effective in providing significant improvements in overall impact strength result spreads collected for any particular group of processed samples without unacceptably reducing the strengthening effect of the chemical conditioning treatment.

The specific embodiment of the present method comprising both chemical adaptation (ion exchange treatment step) and acid etching step provides a consistently significant improvement in impact resistance when compared to glass that is chemically treated separately. The acidic treatment step is considered to provide a chemical polishing treatment of the surface to change the size and/or geometry of the surface defects, and such size and shape variables are considered to play an important role in the ball drop performance, but for the surface In general, the topology has only a low micro effect. In general, an acid etching process effective to remove surface glass of no more than about 4 microns, or in some embodiments no more than 2 microns, or even less than 1 micron, may be utilized for purposes of this disclosure.

However, surface glass that has been acid removed from the chemically-adapted glass sheet beyond the aforementioned thickness should be avoided for at least two reasons. First, excessive removal reduces both the thickness of the surface compression layer and the surface stress values provided by the coating. Both effects are detrimental to both the impact and flexural damage resistance of the glass. Second, excessive etching of the glass surface may increase the surface haze value in the glass to an unpleasant level. Correct For consumer electronic display applications, visually sensible surface haze is not acceptable within the glass cover of the display.

A variety of different chemicals, concentrations, and processing times can be utilized to achieve the selected ball drop impact test performance value. Examples of chemicals suitable for performing the acidic treatment step may include a fluorine-containing aqueous treatment medium containing at least one active glass etching compound selected from the group consisting of HF, HF and HCL, HNO ₃ and H ₂ SO ₄ , A combination of ammonium hydrogen fluoride, sodium hydrogen fluoride, and one or more other. That is, as a specific example, an aqueous acidic solution containing 5 vol.% HF (48%) and 5 vol.% H ₂ SO ₄ (98%) in water will be able to utilize a processing time of as little as one minute to significantly improve The ball drop performance of ion exchange-strengthened alkali metal silicate glass sheets in the thickness range of 0.5-1.5 mm.

The best results of an acidic etch medium consisting of HF/H ₂ SO ₄ can be obtained by using a pulverized sheet previously reinforced with a chemical (ion exchange) conditioning treatment. Glass that has not been subjected to ion exchange strengthening or thermal conditioning before or after acid etching may require different combinations of etching media, resulting in significant improvements in ball drop test results.

If the concentration of HF in the HF-containing solution and the dissolved glass composition can be closely monitored, it will help to maintain proper control of the thickness of the glass layer removed by the etching of the HF-containing solution. Regular replacement of the entire etch bath to restore acceptable etch rates is effective for this project, but bath replacement is expensive, while the cost of effectively processing and placing the removed etch solution is extremely high.

In accordance with the present disclosure, a method for continuously refreshing an HF etch bath containing excessive amounts of dissolved glass or insufficient concentration of HF is provided. According to the method, a bath containing a known concentration of dissolved glass composition and HF may be used, wherein the HF concentration is below a predetermined minimum and/or the mass of the dissolved glass is above a predetermined maximum to remove a volume of bath liquid. The removed volume is then replaced with an equivalent volume of HF containing solution containing HF having a concentration sufficient to restore the HF concentration of the bath to at least the predetermined minimum HF concentration. In a typical embodiment, the replacement solution will also be substantially free of dissolved glass components.

The method steps can be implemented in a stepwise manner or in a substantially continuous manner, i.e., as noted in the particular glass sheet completion plan to be utilized. However, if implemented in a stepwise manner, the removing and replacing steps are performed in accordance with or sufficient to maintain the HF concentration at or above the predetermined minimum, and maintain the quality of the dissolved glass component at the predetermined maximum. The value is performed at or below the frequency. The minimum HF and maximum dissolved glass values are predetermined from values found to unacceptably reduce the glass surface dissolution rate of the bath. The HF and dissolved glass concentrations in the bath at any selected time can be measured, or given the knowledge of the etching conditions, the dissolved glass composition, and the surface area of the treated glass sheet.

From the ball drop test results for commercially available treated glass sheets, the effectiveness of the foregoing method in improving the impact damage resistance of thin pull base metal silicate glass sheets can be seen. Figures 1 and 2 of the accompanying drawings are respectively provided for providing two such commercial glass sheets A strip chart of the test data for the film, Corning Code 2318 glass and Corning Code 2317 glass.

These ball drop tests are performed using the aforementioned standardized ball drop test procedure. The stainless steel ball system falls on the square (50mm x 50mm) glass piece from the incremental height until the sample impact fails. All tested samples were subjected to the same conventional ion exchange conditioning treatment prior to testing, and the selected ones of the samples were also previously subjected to 5 vol.% HF (48%) and 5 vol in water prior to ball drop testing. .% of the H ₂ SO ₄ (98%) aqueous solution was treated with an etched surface. The acid etched or treated (T) samples are differentiated from unprocessed (NT) samples in a bar pattern, as shown in the "Key" of each figure. All of the acid etching processes are performed for a processing time interval effective to allow the etching solution to remove a layer of glass having a thickness of no more than about 2 microns from the surface of the Corning Code 2318 and Corning Code 2317 glass sheets.

The height of the ball drop (failure height) of each of the two numbered set samples (one processed (T) sample and one accompanying unprocessed (NT) sample) at the impact failure is the vertical of each figure The bar height on the shaft (in/cm) is shown, except for the 180 cm bar height, with the exception of one of Figure 2, which indicates survival at the ball drop height rather than failure. The sets of samples are numbered on the horizontal axis of the graph, and the sets are arranged in an order that increases the failure height of the samples in increments. In this test series, samples that survived a 180 cm ball drop were not tested at higher ball drop heights.

A representative ball drop test result for a Corning Code 2318 glass piece sample having a thickness of 0.7 mm is shown in Figure 1, and a representative ball drop test result for a Corning Code 2317 glass piece sample having a thickness of 1.3 mm is shown in Figure 2. It is apparent that for both glasses and at both sheet thicknesses, the treated sheets are superior to the untreated sheets in impact damage resistance, even in such untreated sheets. The same is true for the case of exhibiting a relatively low impact damage resistance.

By using the method of the present invention to ensure improved ball drop performance, this represents the need to provide appropriate impact damage resistance for display overlay glass applications, even in samples that fail at the lower end of the ball drop height range. However, the use of the biaxial flexural strength test method to further evaluate the performance of the strengthened flakes shows that although the average flexural strength value is improved, the individual flake strengths remain unpredictable. Thus, a portion of the sheet will have a sufficiently low flexural strength value to present a risk of failure to produce an unacceptable cover sheet in future use.

Figure 3 is a graph showing the results of a biaxial flexural strength test for two thin glass sheet sample series. These data are the results from tests conducted on glass flake samples having a composition of aluminosilicate glass and a sheet thickness of 1.0 mm. The strength tests include subjecting each sample to the ring-to-ring flexural stress to a point of damage within the apparatus supporting the bottom surface of each of the samples on a 1 inch diameter ring, while using 0.5 centered on the bottom ring A ring of inch diameter is applied to the top surface of the biaxial flexural stress. The horizontal axis in Figure 3 indicates the damage of each of the samples. The failure load S applied at the point is in kilograms (kgf), while the vertical axis represents the percentage failure probability P (%) of the samples in each of the two groups.

The results of these two series fall on two different best-matched trend line curves, which are labeled A and B. The data on curve A is for ion exchange strengthened glass samples that are not subjected to replenishing surface treatment, while the data on curve B is for ion exchange strengthened glass samples subjected to complementary acid etching enhancement treatment according to the present disclosure.

The data in Figure 3 presents a significant increase in the average flexural strength that can be obtained by acid etching enhancement of the sample according to the method of the present invention. Thus, for a glass sheet having a selected composition and thickness, an average failed load of more than 840 kgf can be measured by the acid etched sample (B), while an average failure load of 294 kgf is measured for the sample (A). However, curve B also indicates that for such acidic etch samples, there is still a significant probability of failure (i.e., greater than 5%) at failure loads below 400 kgf. Thus, the combination of glass sheet adaptation and complementary acid etch enhancement treatments does not, in all cases, yield consistent high flexural strengths required for commercial applications of advanced information display devices.

The failure analysis performed to identify the origin of the fracture in the aforementioned low flexural strength sample points is toward a dwelling surface having a considerable depth and becomes a source of these cracks. That is, as introduced in the sheet manufacturing process, these defects cannot be effectively eliminated by the limited surface etching that can be tolerated in chemically-adapted glass sheets used in electronic information displays.

Based on these analyses, it is concluded that the flexural strength of the thin-adapted and acid-etched glass sheets is significantly affected by the surface quality of the starting glass sheet, especially including any that has appeared on the sheet prior to processing. The size and spatial distribution of the surface flaws. The source of the failure of this sheet cannot be seen from the ball drop test, which is obvious, because the surface area of the sheet strained under the impact of the ball drop is much smaller than that under the biaxial or four-point bending test.

Figure 4 illustrates the effect of the calculated effect of the surface enthalpy depth on the modulus of the burst strength of the untreated glass sheet, which is measured by a conventional four-point bend. The surface depth D is in micrometers (micrometers) on the horizontal axis, and the calculated fracture stress modulus (MOR) is expressed in megapascals (MPa) on the vertical axis. That is, as shown by the damage stress curve in Fig. 4, the glass rupture strength modulus decreases rapidly with increasing enthalpy depth, while the maximum sag depth is observed in the 瑕疵 depth in the range of 0.5-3 microns.

Therefore, in order to ensure the consistency and high strength in the thin glass sheet subjected to the chemical adjustment and the acid etching treatment according to the method of the present invention, a preliminary step of treating the sheet having substantially no surface flaw of more than 2 micrometers in depth before processing is performed. It is of great importance. These sheets can consistently provide high flexural strength, even if etching is designed to remove only the minimum surface thickness from the adapted sheet.

The method of providing a glass sheet surface free of surface flaws exceeding 2 microns in depth is not critical. Use mechanical pre-completion (through grinding and polishing), or use the device to be protected after careful protection The manufacture of a variety of strength screening treatments for the treatment of damaged melt-constituting sheets can provide glass having the necessary conditions without large surface flaws. However, higher levels of strength intensification work are typically provided, wherein the present method can be applied to a glass sheet having a molten calendered surface.

For video display overlay applications involving touch screen functionality and/or video displays that require a minimum of practical cover glass thickness, high retention (post-etch) compressive surface stress and high retention compression layer are required. Both depths. Specific embodiments suitable for use in such applications include having an alkali metal ruthenate composition having a thickness of no more than 1 mm, or in some embodiments, a thickness of no more than 0.7 mm or a thickness of not more than 0.55 mm, and after manufacture A molten laminated glass sheet treated in accordance with the present disclosure. A satisfactory tempered glass cover sheet having said composition and thickness for such applications retains a compressed surface layer having a depth of at least 30 μm, or a depth of 40 μm, after the surface etching process, the surface layer providing at least 500 MPa, Or a peak pressure stress value of 650 MPa.

In order to provide a thin alkali metal silicate glass cover sheet having a combination of such properties, a sheet surface etching treatment for a limited period of time is required. In particular, the step of contacting the surface of the glass sheet with the etching medium may be carried out for a period of time which is not more than effective to remove the 2 μm surface glass, or in some embodiments, no more than one surface effective to remove the 1 μm surface glass. In any case, the actual etching time necessary to limit glass removal will depend on the composition and temperature of the etching medium and the composition of the solution and glass to be treated, but is effective for a selected glass. The removal of no more than 1 or 2 μm glass on the surface of the sheet can be determined in accordance with routine experimentation.

An alternative method to ensure that the strength of the glass sheet and the depth of the surface compression layer can be adapted for thin overlay or touch screen applications involves tracking the reduction in surface compressive stress values as the etching process is performed. The etching time is then limited, thereby limiting the reduction of the surface compression layer that is necessarily produced by the etching process. Thus, in some embodiments, the step of contacting the surface of the strengthened alkali metal silicate glass sheet with the etching medium is performed for a period of time not exceeding a period effective to reduce the compressive stress value in the surface of the glass sheet by 3%. . Again, the length of the period suitable for achieving this result will depend on the composition and temperature of the etch medium and the composition of the glass sheet, although it can be determined by routine experimentation.

That is, as noted above, the particular etching process used to process the surface of the conditioned glass sheet is not critical, but is dependent upon the particular etch medium employed and the particular requirements of the overlay glass application. In the case where the strengthening treatment can be limited to the rear side surface of only the video display cover sheet, that is, the surface of the sheet to be placed on or near the display surface of a selected video display device, the etching medium can be rolled by Applying, brushing, spraying, etc. are conveniently applied. On the other hand, in the case where both sides of the glass cover sheet are treated, the immersion method is the most economical procedure.

A tempered glass cover sheet exhibiting a combination of special strength and optical properties, such as haze, surface appearance and glare suppression, wherein the cover sheet is incorporated into a device designed for high resolution video displays The inside case may be necessary. The production of cover glass for these advanced applications will require further constraints on the available enhancement procedures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE STRENGTH COVER PLATE FOR HIGH PERFORMANCE VISUAL APPLICATIONS The present invention outlines the steps of selecting a glass sheet having an alkali metal ruthenate composition having a thickness of no more than about 1.0 mm; At least one surface of the glass sheet is in contact with an ion exchange strengthening medium comprising an alkali metal ion source having a larger ion diameter than at least one alkali metal ion component present in the glass. The step of contacting the surface with the ion exchange strengthening medium is carried out in the following manner (i) at a temperature below the strain point of the glass, and (ii) at a depth sufficient to have a depth of more than 40 μm. The time of the compressive stress layer and the peak compressive stress value exceeding 650 MPa.

After the ion exchange strengthening treatment, at least one surface of the glass sheet is brought into contact with an etching medium containing an acidic solution having a fluorochemical compound therein. According to a particular embodiment, the step of contacting the etching medium is carried out at a temperature for a period of time such that (i) no surface glass is removed from the surface of the sheet by more than 2 μm; (ii) on the surface of the sheet Maintaining a compressive stress of the glass of at least 650 MPa; (iii) maintaining a final transmittance and a surface image value of not less than 1% of the initial transmittance and the surface dimension of the glass sheet, respectively; and (iv) The glass sheet maintained a final haze value of no more than 0.1%.

The bottom table below shows the optical data collected for the thin alkali metal silicate glass flake samples, some of which contain uncorroded The surface is engraved, and some are surfaces having the aforementioned acid fluorinated solution etched to remove the amount of minute surface glass from the sheets. The "type" A sample in Table 1 is a glass piece sample having a surface that has been finished by grinding and polishing prior to processing, while the "type" B sample has the same unmodified or identical surface as the pull surface. Samples of the size and shape of the pull sheet.

The light transmission values illustrated in Table 1 include the percentage of visible light that is transmitted through the surface of both of the sample sheets from known light sources. The haze value determined according to the ASTM D1003 method is a measure of the percentage of light lost by wide-angle scattering of the light as it passes through the surface of the sheet from a known source. The Zeta value determined according to the ASTM D523 method is the total reflection of the combined light from both surfaces of each of the sheets, and for these particular samples exceeds 100% in total. The data from Table 1 does show the effectiveness of the surface etching process to improve the sample strength without significantly affecting the optical properties of the glass sheets.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a particular advantage for treating a thin alkali metal silicate glass sheet incorporating a glare resistant surface layer on at least one surface of the sheet. The production of the sheet usually involves an additional step of contacting the surface of the glass with the ion exchange strengthening medium, i.e., treating at least one surface of the sheet to provide a glare resistant surface. Floor. The step of providing a glare resistant surface and compatible with the intensifying method comprises the step of forming an inorganic, alkali metal ion on the glass sheet Any known method of penetrating, light scattering surface or surface layer. Coverage

A particular advantage of the sheet strengthening process is that it can be used to strengthen and have such an alkali-resistant aluminum silicate glass sheet without the unacceptable modification of the anti-glare characteristics of the surfaces.

A further embodiment of the present method includes wherein the glass sheet is pretreated prior to the strengthening treatment to reduce the number and/or size of surface imperfections thereon. Specific examples of such specific embodiments include those having an additional step prior to the step of contacting at least one surface of the glass with the ion exchange medium, such that at least one surface of the glass contacts an etch medium Remove the surface glass. The etching medium suitable for this pretreatment comprises the same fluorine-containing solution that can be used to remove the thin surface layer from the glass sheets, followed by ion exchange treatment.

Figure 5 is a graph showing the results of a biaxial flexural strength test for three thin glass sheet sample series subjected to different ion exchange and surface etching treatment combinations. These data are the results from tests conducted on glass flake samples having a composition of aluminosilicate glass and a sheet thickness of 1.0 mm. The intensification tests involve subjecting each sample to the ring-to-ring flexural stress and subsequently performing the procedure for generating the data shown in Figure 3 above. The horizontal axis in Figure 6 represents the flexural stress load S applied at the break point of each of the samples, in kilograms (kgf), while the vertical axis represents the sample in each of the three groups. Percentage failure probability P (%).

The results of these three sample series are outlined along three different trend lines, labeled A, B and C. Square data The data represented by the trend line A (A sample) is about the ion exchange strengthened glass sample that has not been subjected to the pre- or supplementary surface etching treatment by the fluorinated solution, but the circular data points and the trend The data represented by line B (B sample) is for a sample having the same composition and geometry and subjected to ion exchange strengthening treatment sequentially and then subjected to surface etching treatment of the acidic fluorochemical solution as described above. Finally, the triangular data points represented by trend line C (C sample) are sequentially subjected to pre-surface etching by acidic fluorinated solution and then treated as ion exchange enhancement of the A and B samples, and finally A sheet sample subjected to a second surface etching treatment with an acidic fluorochemical solution, wherein the solution is the same as the solution used to treat the B samples.

That is, as reflected in the data in FIG. 5, the C samples subjected to both the pre- and final etching processes exhibit a flexural strength at least equivalent to the B sample represented by curve B, and are at the minimum of the pattern. The intensity range has a significantly higher intensity than the samples of curves A and B. Thus, the curve C sample exhibited an average failure load at about 651 kgf breakage, while the curve A and curve B samples exhibited average failure loads at 258 kgf and 569 kgf breakage, respectively.

A further benefit obtained from the step of subjecting the thin aluminosilicate glass sheet to chemical etching followed by conditioning treatment is to significantly improve the sheet resistance of the resulting flexural damage due to edge defects occurring at the edges of the sheet. These defects can be induced, for example, during the processing of sheet cutting.

Figure 6 shows the failure probability data for two thin glass specimens subjected to a 4-point bending stress to the breakage point. The 4-point bending data is a measure of the edge strength of the sheet, that is, the weakening of any edge defects appearing on the glass sheet sample, compared to the ball drop and ring-ring test environment that yields the surface quality and strength of the glass sheet. effect.

The data plotted in Figure 6 represents the results of the bending test obtained from a thin sheet glass sample having a size of 44 mm by 60 mm. The data point represented by trend line A of Figure 6 is the failure probability value P (expressed as a percentage on the vertical axis of the graph) for the adapted, unetched sample group, and represented by trend line B. The data points are values for a sample group that is subjected to an acid etch followed by an adaptation process. The etching treatment is carried out in accordance with the composition and manner of the acidic fluorochemical solution described above. The stress value S applied at the point of failure of each of the samples is expressed in megapascals (MPa) on the horizontal axis of the graph.

From this data, the improvement results exhibited by the B (acid etched) samples in the bending strength can be seen in Figure 6, which exhibit an average failure stress of about 663 MPa and the B samples exhibit an average failure stress of about 728 MPa. Even if the amount of glass removed by the etching treatment is small (about 2 μm) and the edge of the sheet strength is limited to have a range of 15-30 μm, it is true that these improvement results are obtained.

Figure 7 shows a schematic cross-sectional illustration of a video display device incorporating a shock-damping glass cover sheet in accordance with the present disclosure. That is, as shown in the side cross-sectional view of FIG. 7, the video display device 10 includes a video display 12, which is bonded to the impact damage impedance base by a selective adhesive layer 14. A metal silicate glass cover sheet 16 is provided. In the embodiment of Fig. 7, at least the rear side surface 16a of the cover sheet facing the action display surface 12a of the video display is an acid etched surface having a surface compression layer. In a particular embodiment, the back side surface 16a is at a surface compressive stress of at least 400 MPa and the surface compressive layer has a depth of at least 15 μm.

Of course, the specific embodiments of the glass products, the video display, and the glass processing method described in the present disclosure are presented for illustrative purposes only, and are not intended to be in the scope of the patent application. The design, use, or practice of the method or its equivalent is limited or constrained.

10‧‧‧Video display device

12‧‧‧Video display

14‧‧‧Adhesive layer

16‧‧‧ Cover Sheet

12a‧‧‧ display surface

16a‧‧‧Back surface

Claims (26)

An impact damage resistant glass sheet comprising at least one tempered and chemically etched surface that does not contain surface defects having a depth of more than 2 microns, the glass sheet exhibiting a standardized 128g ball drop failure of at least 120 cm The height and the tempered and chemically etched surface incorporate a surface compression layer having a depth of at least 8 microns and a surface compressive stress value of at least 200 MPa. A glass sheet for impact damage resistance according to the scope of claim 1 wherein the glass sheet is a flat sheet having a uniform thickness of no more than 2 mm, wherein the chemically etched surface is an acid etched surface, and wherein the surface compressive layer has at least 15 microns The depth and the surface compressive stress value of at least 400 MPa. An impact-damaged glass sheet according to claim 2, wherein the glass sheet is composed of alkali metal aluminosilicate glass and wherein the surface compression layer is an ion exchange surface layer having at least about 30 microns The depth and the surface compressive stress value of at least about 500 MPa. A glass sheet of impact damage resistance according to item 3 of the patent application, wherein the thickness does not exceed 1 mm and the ion exchange surface layer has a depth of at least about 40 microns and a surface compressive stress value of at least about 650 MPa. Video display formed by alkali metal aluminosilicate glass A cover sheet having a thickness of no more than 1 mm, a compressive stress surface layer having a thickness of at least about 40 microns, and a peak surface compressive stress value of at least about 650 MPa, wherein the compressive stress surface layer is chemically etched and free Surface flaws over 2 microns deep. A cover sheet according to item 5 of the patent application, wherein the sheet has a thickness of not more than 0.7 mm. A video display device comprising a glass cover sheet with impact damage resistance, wherein the glass cover sheet has (i) a thickness in the range of 0.2-2 mm, (ii) an alkali metal aluminosilicate glass component, and (iii) At least one surface compression layer incorporating a chemically etched surface, wherein the chemically etched surface is free of surface defects having a depth of more than 2 microns. The display device of claim 7, wherein the glass cover sheet has a thickness of no more than 1 mm, wherein the chemically etched surface is an acid etched surface, and wherein the surface compressive layer incorporating the acid etched surface has at least 30 The depth of the micron and the surface compressive stress value of at least 500 MPa. A method of making an impact damage resistive glass sheet, the method comprising the steps of: (i) applying at least one surface of the glass sheet to a tempering treatment to develop a compressible surface layer thereon, and (ii) the glass sheet At least one surface is in contact with the chemical glass etching medium A layer of glass is removed, wherein the surface of the tempered glass sheet is substantially free of surface imperities greater than 2 microns in depth. The method of claim 9, wherein the step of applying at least one surface of the glass sheet to the tempering treatment comprises subjecting the glass sheet to a tempering treatment to effectively provide a surface of at least 400 MPa in the surface of the glass sheet. The compressive stress value, and wherein the step of contacting at least one surface of the glass sheet with the chemical glass etch medium comprises contacting the surface with the acidic etch medium at a temperature for a period of time to effectively remove a surface of no more than 4 microns from the glass sheet glass. The method of claim 9, wherein the step of applying the tempering treatment to the surface of the glass is prior to contacting the surface of the glass with the etching medium. The method of claim 9, wherein the glass piece is an alkali metal aluminosilicate glass component. The method of claim 9, wherein the tempering treatment is selected from the group consisting of thermal tempering and chemical tempering. The method of claim 13, wherein the tempering treatment comprises chemical tempering and the step of contacting at least one surface of the glass with the ion exchange strengthening medium. The method of claim 9, wherein the etching medium is an aqueous solution containing fluoride. According to the method of claim 15 of the scope of patent application, which includes The etching efficiency of the etching bath having the etching medium is maintained by removing a volume of the medium from the bath, the bath (i) containing a concentration of HF below a predetermined minimum and/or (ii) containing a high The removed volume is replaced by a concentration of dissolved glass at a predetermined maximum, and the HF concentration contained in the HF solution exceeds a predetermined minimum. A method of manufacturing a display cover sheet for a video display device, the method comprising the steps of: selecting an alkali metal aluminosilicate glass sheet having a thickness of not more than 1 mm, contacting at least one surface of the glass sheet with an ion exchange strengthening medium A compressive surface layer is developed thereon, and at least one surface of the glass sheet is contacted with a chemical glass etch medium to remove a layer of surface glass therefrom, wherein the at least one surface is free of surface defects having a depth of more than 2 microns. The method of claim 17, wherein the step of contacting at least one surface of the glass sheet with the glass etching medium comprises contacting the surface with an acidic fluoride-containing glass etching medium and performing at a temperature for a period of time not exceeding The time to effectively remove a layer of surface glass having a thickness of no more than 4 microns from the glass sheet. The method of claim 17, wherein the step of contacting at least one surface of the glass sheet with the acid glass etching medium is performed at a temperature for a period of time to effectively remove the thickness of the glass sheet from a thickness of no more than about 2 μm. a layer of surface glass. The method of claim 17, wherein the step of contacting at least one surface of the glass sheet with the acid glass etching medium is performed for a period of time not exceeding the effective reduction of the compressive stress value in the surface of the glass sheet. 3% of the time. The method of claim 17, wherein the step of contacting at least one surface of the glass sheet with the ion exchange strengthening medium comprises contacting the surface with a source of alkali metal ions having a larger ion diameter, the ion diameter of which is greater than at least the presence of the glass An alkali metal ion component. The method of claim 21, wherein the step of contacting at least one surface of the glass sheet with the ion exchange strengthening medium is performed at a temperature below the strain point of the glass, and for a period of time sufficient to develop depth A compressive stress layer exceeding 40 microns and a peak compressive stress value exceeding 650 MPa in at least one surface. The method of claim 17, wherein the step of contacting at least one surface of the glass sheet with the glass etching medium is performed at a temperature for a period of time such that (i) does not remove more than 2 microns of thickness from the surface of the sheet. (ii) maintaining a compressive stress of at least 650 MPa on the surface of the sheet; (iii) maintaining the final haze value of the glass sheet not exceeding 0.1%; (iv) maintaining the initial light transmission of the glass sheet compared to the glass sheet The difference between the degree value and the initial surface gloss value is not exceeded. Over 1% final transmittance value and final surface gloss value. The method of claim 17, wherein prior to the step of contacting at least one surface of the glass sheet with the ion exchange strengthening medium, further comprising the step of treating at least one surface of the glass sheet to provide an anti-glare surface thereon. The method of claim 17, wherein before the step of contacting at least one surface of the glass sheet with the ion exchange strengthening medium, further comprising pre-treating at least one surface of the glass sheet to reduce the number of surface flaws thereon And/or size steps. The method of claim 25, wherein the pre-treating step comprises contacting at least one surface of the glass sheet with an etching solution to remove the surface glass therefrom.