JP2017001902A - Cover glass and portable information terminal having the same, and method for producing cover glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cover glass which can reduce the warpage of a thin part and a portable information terminal having the same, and a method for producing a cover glass.SOLUTION: A cover glass 1 comprises at least one thin part 13 formed by providing at least one recess 7 on a surface 3 or a rear surface 5 of the cover glass 1, and a thick part 17 connected to the thin part 13. At least one of the surface 3 and the rear surface 5 of the thin part 13 has a film 21, 22 of 10-1000 nm formed thereon.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a cover glass, a portable information terminal having the cover glass, and a method for manufacturing the cover glass.

  In recent years, a method of using a fingerprint for personal authentication is actively used as an advanced security measure in electronic devices. Fingerprint authentication methods include an optical method, a thermal method, a pressure method, and a capacitance method, and the capacitance method is considered to be superior from the viewpoint of sensing sensitivity and power consumption.

  The capacitance type sensor detects a local change in capacitance at a site where the detection object approaches or comes into contact. A general electrostatic capacity type sensor (hereinafter also simply referred to as a sensor) measures the distance between an electrode arranged in the sensor and an object to be detected based on the magnitude of the electrostatic capacity. Since the fingerprint authentication function using such a capacitance type sensor is small and light and has low power consumption, it is particularly mounted on personal information terminals (PDAs) such as smartphones, mobile phones, and tablet personal computers. Has been.

  Usually, in order to protect a capacitive sensor, a protective cover (sensor cover) is disposed above the sensor. For example, in the capacitive sensor packaging of Patent Document 1, it is disclosed that a hole is provided in a cover glass so that the sensor can detect an object, and a sensor cover is disposed in the hole. As the sensor cover, a material having a high dielectric constant and a small thickness is used in order to improve sensing sensitivity. Moreover, as a cover glass, in order to ensure the durability with respect to the fall of an electronic device or a collision with another object, what strengthened the glass chemically is generally used.

  In the configuration in which a hole is formed in the cover glass and the sensor cover is disposed in the hole as in the invention described in Patent Document 1, a jig or the like for fixing the sensor cover to the hole is required, and thus the number of parts is large. This complicates the assembly process. Further, since a different material such as a sensor cover is required in addition to the cover glass, it is difficult to achieve a material sense of unity and the design is inferior.

International Publication No. 2013/173773

  Therefore, the present inventors have come up with a cover glass that is uniform in material and has a sense of unity and is excellent in design without using different materials such as a sensor cover. That is, the present inventors have conceived a cover glass comprising at least one thin part formed by providing at least one concave part on the front or back surface of the cover glass, and a thick part connected to the thin part. did. According to this cover glass, if the sensor is arranged at a position corresponding to the concave portion, the sensor can be protected by the thin portion.

  Furthermore, the present inventors have found that when a cover glass including a thin part and a thick part connected to the thin part is chemically strengthened, the thin part warps on the front side or the back side. This is considered to be because (thickness of the ion exchange layer / thickness of the non-ion exchange layer) is different between the thin portion and the thick portion. That is, since (thickness of ion exchange layer / thickness of non-ion exchange layer) in the thin-walled portion is larger than (thickness of ion-exchange layer / thickness of non-ion-exchange layer) in the thick-walled portion, It expands more than the thick part. And since the thin part expand | swells in the state in which the periphery was regulated by the thick part, it will warp the front side or the back side.

  This invention is made | formed in view of the subject mentioned above, The objective is to provide the manufacturing method of the cover glass which can reduce the curvature of a thin part, a portable information terminal which has this, and a cover glass. is there.

The above object of the present invention is achieved by the following configurations.
(1) A cover glass for protecting a protection object,
The cover glass includes at least one thin portion formed by providing at least one concave portion on the front or back surface of the cover glass, and a thick portion connected to the thin portion,
A cover glass in which a film having a thickness of 10 to 1000 nm is formed on at least one of a front surface and a back surface of the thin portion.
(2) The cover glass according to (1), wherein the surface compressive stress (CS) of the portion where the film is formed is smaller than the surface compressive stress of the compressive stress layer formed in the thick portion.
(3) The cover glass according to (1) or (2), wherein the main component of the film is an oxide.
(4) The cover glass according to (3), wherein the oxide is SiO ₂ .
(5) One thin portion is formed on the cover glass by providing one concave portion on the front surface or the back surface of the cover glass,
The thickness and area of the thin portion are t1 and s1, respectively.
When the thickness and area of the thick part are t2 and s2, respectively.
The cover glass according to any one of (1) to (4), wherein 0.05 ≦ t1 / t2 ≦ 0.9 and 0.001 ≦ s1 / s2 ≦ 0.9.
(6) A portable information terminal having the cover glass according to any one of (1) to (5).
(7) A cover glass manufacturing method for manufacturing a cover glass for protecting a protection target by chemically strengthening a glass member,
The glass member includes at least one thin portion formed by providing at least one concave portion on the front or back surface of the glass member, and a thick portion connected to the thin portion,
A film forming step of forming a film of 10 to 1000 nm on at least one of the front surface or the back surface of the thin portion;
After the film formation step, a chemical strengthening step for chemically strengthening the glass member,
A method for manufacturing a cover glass.

According to the present invention, when a device such as a sensor is arranged at a position corresponding to the concave portion, the device can be protected by the thin-walled portion. Therefore, unlike the above-described Patent Document 1, the material can be used without using a different material such as a sensor cover. A uniform and uniform cover glass with excellent design can be realized. Moreover, since the number of members is small and the assembly process can be simplified, the cost can be reduced.
Furthermore, since a 10-1000 nm film | membrane is formed in at least one of the surface of a thin part, and a back surface, a thin part becomes difficult to be chemically strengthened compared with a thick part. Thereby, the curvature of the thin part at the time of chemical strengthening can be reduced.

It is sectional drawing of a cover glass. It is an II-II cross-sectional arrow view in FIG. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. It is an III-III cross-sectional arrow view concerning a modification. It is an III-III cross-sectional arrow view concerning a modification. It is an III-III cross-sectional arrow view concerning a modification. It is an III-III cross section arrow view concerning a comparative example. It is an III-III cross-sectional arrow view concerning a modification. It is sectional drawing of a glass member. It is sectional drawing of the glass member in which the recessed part was formed. (A) is sectional drawing of the cover glass which concerns on a modification, (b) is the figure which looked at the recessed part from the Z direction. (A) is sectional drawing of the cover glass which concerns on a modification, (b) is the figure which looked at the recessed part from the Z direction. (A) is sectional drawing of the cover glass which concerns on a modification, (b) is the figure which looked at the recessed part from the Z direction. It is sectional drawing of the cover glass which concerns on a modification. (A) is sectional drawing of the cover glass which concerns on a modification, (b) is the figure which looked at the recessed part from the Z direction. It is sectional drawing of the glass member in which the film | membrane was formed. Sectional view of the cover glass 1 when the thin-walled portion warps to the front side It is sectional drawing of the cover member which concerns on a modification. It is sectional drawing of the cover member which concerns on a modification. It is sectional drawing of the cover member which concerns on a modification.

  Hereinafter, although an embodiment of the present invention is described, the present invention is not limited to the following embodiment. Various modifications and substitutions can be made to the following embodiments without departing from the scope of the present invention.

  The cover glass which concerns on this embodiment is used in order to protect arbitrary protection objects. Hereinafter, although it demonstrates as the protection target of a cover glass being portable information terminals, such as a smart phone, arbitrary objects are applicable as a protection target, for example, it can apply to electronic devices, such as a liquid crystal display device.

  As shown in FIG. 1 and FIG. 2, the cover glass 1 of the present embodiment is a substantially flat rectangular parallelepiped as a whole, and includes a front surface 3 on the upper side in FIG. 1 and a rear surface 5 on the lower side in FIG. Have. In the present specification, the surface means an outer surface of the assembly (assembly) including the cover glass 1, that is, a surface that can be touched by a user in a normal use state. Further, the back surface means an inner surface of the assembly, that is, a surface that cannot be touched by a user in a normal use state. In the following description, the longitudinal direction of the cover glass 1 is the X direction, the short direction is the Y direction, and the thickness direction is the Z direction.

  At least one recess 7 is formed on the front surface 3 or the back surface 5 of the cover glass 1. FIG. 1 and FIG. 2 show an example in which one recess 7 is formed on the back surface 5 of the cover glass 1. The recess 7 is formed in the vicinity of the end portion in the X direction of the cover glass 1 and in the vicinity of the central portion in the Y direction. The X-direction side surfaces 9 and 9 and the Y-direction side surfaces 11 and 11 of the recess 7 extend so as to be parallel to the Z direction. In addition, as long as the position in which the recessed part 7 is formed is the surface 3 or the back surface 5 of the cover glass 1, you may set to arbitrary positions. Further, the shape and number of the recesses 7 are also arbitrary.

  By providing the recess 7 in this manner, the cover glass 1 is formed with a thin portion 13 at a position overlapping the recess 7 in the X direction and the Y direction, and is connected to the peripheral portion of the thin portion 13, so that the thin portion A thick portion 17 having a thickness in the Z direction larger than 13 is formed. The surfaces 14 and 18 of the thin-walled portion 13 and the thick-walled portion 17 have a planar shape and form a flush surface. Further, the back surfaces 15 and 19 of the thin wall portion 13 and the thick wall portion 17 are also planar, and form a step shape.

  In the configuration in which the concave portion 7 is provided on the back surface 5, a capacitive sensor such as a fingerprint authentication sensor is disposed in the concave portion 7, and an object to be detected (for example, a finger) that is in contact with the surface 14 of the thin portion 13. To detect. In such a configuration, since the surface 3 of the cover glass 1 is flat over the entire surface, the aesthetic appearance is very excellent.

  FIG. 3 shows the cross-sectional shape around the recess 7 (thin wall portion 13) in more detail. A film is formed on at least one of the front surface 14 and the back surface 15 of the thin portion 13. The cover glass 1 in FIG. 3 is formed on the surface film 21 formed on the surface 14 of the thin portion 13, the back film 22 formed on the back surface 15, and the X-direction side surface 9 and the Y-direction side surface 11 of the recess 7. And a side film 23.

  These films 21, 22, and 23 suppress chemical strengthening of the portions where the films are formed (the front surface 14, the back surface 15, the X direction side surface 9, and the Y direction side surface 11). Moreover, since these films 21, 22, and 23 alleviate the chemical strengthening reaction of the cover glass 1 and make it difficult for the cover glass 1 to undergo a rapid change, defects due to the chemical strengthening in the recesses 7 can be reduced. In order to exhibit the chemical strengthening suppressing effect, the films 21, 22, and 23 preferably contain oxides, nitrides, carbides, borides, silicides, metals, and the like as main components. This is because a film containing such a substance has a smaller diffusion coefficient of sodium ions and potassium ions in the film than in glass.

Examples of the oxide include a non-alkali oxide, a composite oxide containing an alkali element or an alkaline earth element, and SiO ₂ is particularly preferable. By applying SiO ₂ as the main component, diffusion of sodium ions and potassium ions in the film is moderately suppressed. Further, since the transmittance of the film is high and the refractive index is close to that of glass, the change in appearance due to the coating can be minimized. Also, film composed mainly of SiO _2, the physical durability and chemical durability is high.

  An alkali-free oxide is an oxide composed of an element other than an alkali metal element, and is an oxide and composite oxide containing one or more elements other than an alkali metal, or two or more oxides and composite oxides. It is a mixed oxide or a laminate of the above oxides and composite oxides.

  As the alkali-free oxide, an oxide comprising silicon and an oxide containing at least one composite oxide are preferable. In a film containing such an oxide, diffusion of sodium ions and potassium ions is moderately suppressed in the film. Further, since the transmittance of the film is high and the refractive index is close to that of glass, the appearance change due to the coating can be minimized. In addition, a film containing such an oxide has high physical durability and chemical durability.

  Examples of the nitride include nitrides such as silicon, boron, and titanium. Silicon nitride is particularly preferable. This is because the transmittance of the membrane in the visible range is relatively high and the physical durability and chemical durability are excellent.

  Examples of the carbide include carbides such as silicon carbide and titanium carbide.

  Examples of the metal include silicon, titanium, aluminum, zinc, tin, tantalum, zirconium, niobium, indium, and hafnium.

  The films 21, 22, and 23 may be films made of only one of oxide, nitride, carbide, etc., and may contain other compounds such as carbide, fluoride, sulfide, etc. May be. A film in which a small amount of a lanthanoid element or an actinoid element is doped may be used.

The combined capacitance of the films 21, 22, 23 and the thin portion 13 is preferably 1 × 10 ⁻¹³ F or more, more preferably 5 × 10 ⁻¹³ F or more, and further preferably 1 × 10 ^{−5. 12} F or more. This is because the parasitic capacitance indicating the capacitance component due to the physical structure is reduced and the sensing sensitivity is increased. The combined capacitance of the films 21, 22, 23 and the thin portion 13 is preferably 1 × 10 ⁻⁵ F or less, more preferably 1 × 10 ⁻⁶ F or less, and further preferably 2 ×. 10 ⁻⁷ F or less. This is because sensitivity changes due to changes in the external environment such as temperature and humidity are small and can be used stably.

  The film thicknesses of the films 21, 22, and 23 are 10 nm or more, preferably 12 nm or more, more preferably 15 nm or more, more preferably 20 nm or more, and further preferably 25 nm or more. When the film thickness is 10 nm or more, chemical strengthening of the portions where the films 21, 22, and 23 are formed can be suppressed due to the effect of ion exchange inhibition. The thicker the films 21, 22, and 23, the higher the chemical strengthening suppression effect.

  The thicknesses of the films 21, 22, and 23 are 1000 nm or less, preferably 500 nm or less, more preferably 200 nm or less, more preferably 100 nm or less, and further preferably 50 nm or less. When the film thickness exceeds 1000 nm, the warp of the thin portion 13 may be increased. Moreover, there is a possibility that the difference in appearance between the site with and without the films 21, 22, and 23 increases.

  The film thicknesses of the films 21, 22, and 23 can be measured by an X-ray reflectivity (XRR: X-Ray Reflectivity) method. By this measurement, the interface between the cover glass 1 (the thin portion 13 and the thick portion 17) and the films 21, 22, and 23 is defined.

  The coverage shown by the ratio of the area of the films 21, 22, 23 to the area of the front surface 14, the back surface 15, the X direction side surface 9 and the Y direction side surface 11 is preferably 80% or more, more preferably 90% or more, and 95%. The above is more preferable. As shown in FIG. 3, when the entire surface 14, the back surface 15, the X-direction side surface 9 and the Y-direction side surface 11 are covered with the films 21, 22, and 23 and the coverage is 100%, good chemical strengthening suppression An effect is obtained.

The film density of the films 21, 22, and 23 is preferably 0.001 mol / cm ³ or more, more preferably 0.005 mol / cm ³ or more, and still more preferably 0.01 mol / cm ³ or more. More preferably, it is 0.03 mol / cm ³ or more. When the film density is 0.001 mol / cm ³ or more, chemical strengthening of the portions where the films 21, 22, and 23 are formed can be suppressed due to the effect of inhibiting ion exchange.

The film density of the films 21, 22, and 23 is preferably 0.5 mol / cm ³ or less, more preferably 0.2 mol / cm ³ or less, still more preferably 0.1 mol / cm ³ or less, and more More preferably, it is 0.05 mol / cm ³ or less. If the film density exceeds 0.5 mol / cm ³ , the chemical strengthening of the cover glass 1 becomes insufficient, and the required strength may not be ensured.

  The film density can be determined by measuring the refractive index by ellipsometry and thereby evaluating the film density. The film density can be adjusted, for example, by changing the ratio of oxygen, nitrogen, hydrocarbon gas, etc. to the argon gas during sputtering.

When using a SiO ₂ film, the refractive index _{n d} of D line of film 21, 22, preferably less than 1.46, more preferably less than 1.45, more preferably less than 1.44. If the refractive index is greater than 1.46, the warp of the thin portion 13 may be increased.

  These parameters (film thickness, coverage, film density, refractive index, etc.) defining the films 21, 22, and 23 are appropriately changed so as to satisfy a desired chemical strengthening suppressing effect. That is, when the warp of the thin portion 13 after chemical strengthening is large, the film thickness, coverage, film density, and refractive index of the films 21, 22, and 23 may be increased, and when the warp of the thin portion 13 is small. In this case, the film thickness, coverage, film density, and refractive index of the films 21, 22, and 23 may be reduced.

  In order to reduce warping of the thin portion 13 after chemical strengthening, a film (surface film 21 or back surface film 22) may be formed on at least one of the front surface 14 and the back surface 15 of the thin portion 13. Further, the side film 23 may or may not be formed on the side surface 9 in the X direction and the side surface 11 in the Y direction of the recess 7.

  That is, as shown in FIG. 4, the surface film 21 and the back film 22 may be formed, and the side film 23 may not be formed. As shown in FIG. 5, only the surface film 21 may be formed. As shown in FIG. 6, only the back film 22 may be formed.

  As described above, the thin portion 13 on which the films 21, 22, and 23 are formed is less chemically strengthened than the thick portion 17, and, for example, a difference occurs in the surface compressive stress (CS) of the compressive stress layer. The difference (ΔCS) between the CS on the surface of the thin portion 13 on which the film is formed and the CS on the thick portion 17 on the same surface as the surface on which the film is formed is preferably 30 MPa or more. Thereby, the curvature at the time of chemical strengthening of the thin part 13 can be suppressed. ΔCS is more preferably 50 MPa or more, whereby the warp of chemical strengthening can be more effectively suppressed. ΔCS is preferably 500 MPa or less, and more preferably 450 MPa or less. This is because the chemically strengthened cover glass 1 requires rigidity for practical use.

  As shown in FIGS. 5 and 6, when a film is formed on one surface of the thin portion 13, the difference between the CS of the surface 14 of the thin portion 13 and the CS of the surface 18 of the thick portion 17, The difference between the CS on the back surface 15 and the CS on the back surface 19 of the thick portion 17 is the respective ΔCS. As shown in FIGS. 3 and 4, when films are formed on both surfaces of the thin portion, at least one of the front and back surfaces may be considered.

  When the surface film 21 and the back film 22 are formed together, their film thickness, coverage, and film density may be different from each other. Thereby, not only chemical reinforcement suppression but finger slipperiness can be provided. Further, by adjusting the reflection color, the difference in appearance between the thick portion 17 and the thin portion 13 is reduced to give the glass member a sense of unity, or conversely, the difference is increased to reduce the thickness of the thin portion 13. Visibility can be improved.

  In addition, you may provide the recessed part 7 in the surface 3 of the cover glass 1, as shown in FIG. In the configuration in which the recess 7 is provided on the front surface 3, the capacitance type sensor is disposed on the back surface 5 of the cover glass 1 so as to face the recess 7 in the Z direction, that is, on the back surface 15 of the thin portion 13. Unlike the example of FIG. 3, since the sensor is not arranged in the recess 7, the sensor can be made larger than the recess 7 in at least one of the X, Y, and Z directions. Therefore, the thin portion 13 can be reinforced by arranging a sensor having a relatively large size on the back surface 15 of the thin portion 13. The sensor detects an object to be detected that is in contact with the surface 14 (surface film 21) of the thin portion 13. In such a configuration, the user of the portable information terminal can easily recognize the position of the thin portion 13 and the position of the sensor disposed on the back surface 15 of the thin portion 13 by visual or tactile sense using the concave portion 7. it can.

  Even in the configuration in which the concave portion 7 is provided on the surface 3 of the cover glass 1, a film (surface film 21 or back film 22) is formed on at least one of the surface 14 and the back surface 15 of the thin portion 13. In FIG. 8, the surface film 21 is formed on the surface 14 of the thin part 13, the back film 22 is formed on the back surface 15 of the thin part 13, and the side film 23 is formed on the X direction side surface 9 and the Y direction side surface 11 of the recess 7. A formed example is shown.

  As described above, the cover glass 1 of the present embodiment is not limited to the protection application of the portable information terminal, but particularly when used for protection of the portable information terminal, the thickness t2 of the thick portion 17 in the Z direction. Is 2 mm or less, preferably 1.5 mm or less, more preferably 0.8 mm or less. This is because if the thickness t2 of the thick portion 17 is larger than 2 mm, the difference from the thickness t1 of the thin portion 13 becomes large, making the processing difficult, and increasing the weight for use of the portable information terminal. Because it becomes. Further, the thickness t2 of the thick portion 17 in the Z direction is 0.1 mm or more, preferably 0.15 mm or more, and more preferably 0.2 mm or more in order to increase its rigidity. If it is thinner than 0.1 mm, the rigidity becomes too low, and there is a risk that the portable information terminal will not be used for protection.

  Further, the thickness t1 of the thin portion 13 in the Z direction is 0.4 mm or less, preferably 0.35 mm or less, more preferably 0.3 mm or less, still more preferably 0.25 mm or less, particularly preferably. Is 0.2 mm or less, and most preferably 0.1 mm or less. In particular, when a capacitive sensor is disposed on the back surface 15 of the thin portion 13, the detected capacitance increases as the thin portion 13 is thinner, and the sensing sensitivity is improved. For example, even in the case of fingerprint authentication that detects fine irregularities on a fingertip fingerprint, the difference in capacitance according to the minute irregularities on the fingerprint on the fingertip becomes large, so detection with high sensing sensitivity can be performed. . On the other hand, the lower limit of the Z-direction thickness t1 of the thin portion 13 is not particularly limited. However, when the thin portion 13 becomes excessively thin, the strength tends to decrease and it is difficult to exert an appropriate function as a protective portion such as a sensor. is there. Therefore, the Z-direction thickness t1 of the thin portion 13 is, for example, 0.01 mm or more, and preferably 0.05 mm or more. The relationship between the Z-direction thickness t1 of the thin portion, the Z-direction thickness t2 of the thick portion, and the Z-direction depth d of the recess 7 is represented by t1 = t2-d.

  The ratio (t1 / t2) of the Z-direction thickness t1 of the thin portion 13 to the Z-direction thickness t2 of the thick portion 17 is preferably 0.05 or more, more preferably 0.1 or more, 0 More preferably, it is 15 or more. If the ratio (t1 / t2) is less than 0.05, the rigidity of the thin portion 13 may be too low. When trying to secure the rigidity of the thin portion 13, the thickness of the thick portion 17 may be too large.

  The ratio (t1 / t2) is preferably 0.9 or less, more preferably 0.8 or less, and even more preferably 0.6 or less. If the ratio (t1 / t2) is greater than 0.9, the function of the sensor disposed in the thin portion 13 may not be sufficiently exhibited.

  When the ratio (t1 / t2) is in the range of 0.05 to 0.9, the rigidity of the thin portion 13 does not become too low, and the sensor disposed in the thin portion 13 can sufficiently function.

  In addition, the preferable range of the said ratio (t1 / t2) is the same even if it is a case where the thin part 13 is formed in multiple numbers by providing the recessed part 7 in the cover glass 1. FIG.

  When the area of the front surface 14 or the back surface 15 of the thin portion 13 is s1, and the area of the front surface 18 or the back surface 19 of the thick portion 17 is s2, the ratio of the area s1 to the area s2 (s1 / s2) is 0. It is preferably 001 or more, more preferably 0.002 or more, and further preferably 0.005 or more. If the ratio (s1 / s2) is less than 0.001, the area s1 of the thin-walled portion 13 becomes too small, and there is a risk that the sensing performance of fingerprint authentication will deteriorate. Alternatively, the area s2 of the thick portion 17 becomes too large, and portability as a PDA may be reduced.

  Further, the ratio (s1 / s2) is preferably 0.9 or less, more preferably 0.7 or less, and further preferably 0.5 or less. If the ratio (s1 / s2) is greater than 0.9, the area s1 of the thin portion 13 becomes too large, and there is a possibility that the rigidity of the cover glass 1 as a whole cannot be secured.

  When the ratio (s1 / s2) is in the range of 0.001 to 0.9, the rigidity of the cover glass 1 can be ensured without deteriorating the fingerprint authentication sensing performance.

In addition, the preferable range of the said ratio (s1 / s2) is a thing when one thin part 13 is formed by providing one recessed part 7 in the cover glass 1, Comprising: The recessed part 7 is formed in the cover glass 1. When a plurality of thin portions 13 are formed by providing a plurality, the following relational expression is set. That is, the total area of the surface 14 or rear surface 15 of the plurality of thin portions 13 and _{s1 all,} when the area of the surface 18 or rear surface 19 of the thick portion 17 and s2, the ratio to the area s2 of the total area _{s1 all (s1 all} / S2) is preferably 0.001 or more, more preferably 0.002 or more, and further preferably 0.005 or more. If the ratio (s1 _all / s2) is less than 0.001, the area s1 of the thin portion 13 becomes too small, and the sensing performance of fingerprint authentication may be deteriorated. Alternatively, the area s2 of the thick portion 17 becomes too large, and portability as a PDA may be reduced.

The ratio (s1 _all / s2) of the total area s1 _{all to} the area s2 is preferably 0.9 or less, more preferably 0.7 or less, and even more preferably 0.5 or less. . If the ratio (s1 _all / s2) is greater than 0.9, the area s1 of the thin portion 13 becomes too large, and the rigidity of the cover glass 1 as a whole may not be secured.

  The Young's modulus of the thin portion 13 is 60 GPa or more, preferably 65 GPa or more, and more preferably 70 GPa or more. When the Young's modulus of the thin-walled portion 13 is 60 GPa or more, the thin-walled portion 13 can be sufficiently prevented from being damaged due to a collision with an external collision object. Moreover, when a capacitive sensor is arrange | positioned at the recessed part 7, damage to the thin part 13 resulting from fall or collision of a smart phone etc. can fully be prevented. Furthermore, damage to the sensor protected by the thin portion 13 can be sufficiently prevented. Moreover, although the upper limit of the Young's modulus of the thin part 13 is not specifically limited, From a viewpoint of productivity, the Young's modulus of the thin part 13 is 200 GPa or less, for example, Preferably it is 150 GPa or less.

  The Vickers hardness Hv of the thin portion 13 is preferably 3.9 GPa or more, more preferably 4.9 GPa or more. When the Vickers hardness of the thin-walled portion 13 is 3.9 GPa or more, the thin-walled portion 13 can be sufficiently prevented from being scratched due to a collision with a colliding object from the outside. Further, when the capacitive sensor is disposed in the recess 7, it is possible to sufficiently prevent the thin-walled portion 13 from being scratched due to dropping or collision of a smartphone or the like. Furthermore, damage to the sensor protected by the thin portion 13 can be sufficiently prevented. In addition, the upper limit of the Vickers hardness of the thin portion 13 is not particularly limited, but if it is too high, polishing and processing may be difficult. Accordingly, the Vickers hardness of the chemically strengthened glass is, for example, 12 GPa or less, and preferably 10 GPa or less. The Vickers hardness can be measured by, for example, a Vickers hardness test described in Japanese Industrial Standard JIS Z 2244.

  The relative dielectric constant of the thin portion 13 at a frequency of 1 MHz is preferably 7 or more, more preferably 7.2 or more, and further preferably 7.5 or more. When the capacitance type sensor is disposed on the back surface 15 of the thin portion 13, the detected capacitance can be increased by increasing the relative dielectric constant of the thin portion 13, thereby realizing excellent sensing sensitivity. it can. In particular, when the relative permittivity of the thin portion 13 at a frequency of 1 MHz is 7 or more, the capacitance corresponding to the fine irregularities of the fingertip fingerprint is also obtained in the case of fingerprint authentication for detecting the fine irregularities of the fingertip fingerprint. Because the difference between the two becomes large, detection is possible with high sensing sensitivity. The upper limit of the relative dielectric constant of the thin portion 13 is not particularly limited, but if it is too high, the dielectric loss increases, the power consumption increases, and the reaction may become slow. Therefore, the relative dielectric constant of the thin portion 13 at a frequency of 1 MHz is, for example, preferably 20 or less, and more preferably 15 or less. The relative dielectric constant is obtained by measuring the capacitance of the capacitance in which electrodes are formed on both surfaces of the cover glass 1.

  It is preferable that a printed layer is provided on the back surface 5 of the cover glass 1. In particular, as shown in FIG. 3, when the concave portion 7 is provided on the back surface of the cover glass 1, it is preferable to provide a printing layer also on the concave portion 7 (the back surface 15 of the thin portion 13). By providing such a printed layer, the portable information terminal that is the protection target of the cover glass 1 and the capacitive sensor arranged on the back surface 15 of the thin portion 13 are visually recognized through the cover glass 1. Can be effectively prevented. Moreover, a desired color can be imparted and an excellent appearance can be obtained.

  The print layer can be formed from, for example, an ink composition containing a predetermined color material. The ink composition contains, in addition to the color material, a binder, a dispersant, a solvent, and the like as necessary. The color material may be any color material (colorant) such as a pigment or a dye, and can be used alone or in combination of two or more. The color material can be appropriately selected depending on the desired color. For example, when a light shielding property is required, a black color material or the like is preferably used. The binder is not particularly limited, and for example, polyurethane resin, phenol resin, epoxy resin, urea melamine resin, silicone resin, phenoxy resin, methacrylic resin, acrylic resin, polyarylate resin, polyester type Resins, polyolefin resins, polystyrene resins, polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, polyvinyl acetate, polyvinylidene chloride, polycarbonate, celluloses, polyacetal, and other known resins (thermoplastic resins, thermosetting Resin, photocurable resin, etc.). A binder can be used individually or in combination of 2 or more types.

  The printing method for forming the printing layer is not particularly limited, and appropriate printing such as gravure printing method, flexographic printing method, offset printing method, letterpress printing method, screen printing method, pad printing method, spray printing method, etc. The law can be applied.

  Here, when the recessed part 7 is provided in the surface 3 of the cover glass 1, it is easy to form a printing layer in the back surface 5 which is planar shape. By changing the color to a location corresponding to the side or bottom of the recess 7, it is possible to make the location easy to understand visually. Also, if the location corresponding to the side part is specular reflection printing (for example, silver printing), the shape having the curvature of the side part shows the lens effect, and the reflection corresponding to the side part is wide even if the angle of the cover glass is changed. Because it reflects at an angle, it can sparkle and produce a high-class feel.

  On the other hand, when the recessed part 7 is provided in the back surface 5 of the cover glass 1, it is preferable that printing is separately implemented by the said recessed part 7 and the flat part in which the recessed part 7 is not formed in the back surface 5 of the cover glass 1. FIG. This is because the shape followability is not so high in the printing direction such as the screen printing method, and it is difficult to print the concave portion 7 and the flat portion where the concave portion 7 is not formed at a time. Therefore, highly accurate printing can be realized by individually printing these portions. In addition, by changing the color or texture of printing between the concave portion 7 and the flat portion where the concave portion 7 is not formed, the position of the sensor can be displayed in a visually easy-to-understand manner, which can be used as an accent on the design.

  More specifically, a first printed layer is provided on a flat portion where the concave portion 7 is not formed on the back surface 5 by a screen printing method or the like. In the screen printing, after a printing material is placed on a screen having an opening, a squeegee is pressed and slid on the screen, and the printing material is pushed out from the opening of the screen to print a pattern of the opening. Say the method. Moreover, since the recessed part 7 has a side surface which is a curved surface shape, it is preferable to print the recessed part 7 by a pad printing method. Thereby, the second printed layer is formed on the bottom surface and the side surface of the recess 7. Here, the pad printing method is a method of printing by pressing a soft pad (for example, a silicone pad) provided with an ink pattern on the surface against a target substrate and transferring the ink pattern onto the surface of the substrate. Pad printing is sometimes called tacho printing or tampo printing. Thus, in the pad printing method, a pad that is relatively soft and has good shape followability is used. Therefore, it is preferable to perform printing on the side surface of the concave portion by the pad printing method. On the other hand, the printing method such as the screen printing method is not suitable because the shape following property is not so high and the ink cannot be printed on the side surface. The order of printing on the first and second print layers is not particularly limited.

  Moreover, you may print separately by the flat part in which the recessed part 7 is not formed in the back surface 5, the flat bottom face of the recessed part 7, and the curved-surface side. In this case, a first printing layer is provided on a flat portion where the concave portion 7 is not formed on the back surface 5 by a screen printing method or the like. Next, a second printing layer is provided on the bottom surface of the recess 7 by a screen printing method or the like. And the 3rd printing layer is provided in the side surface of the recessed part 7 by the pad printing method. In order to prevent pad printing on the bottom surface, the pad has a cylindrical shape having no portion corresponding to the bottom surface. In this way, by separately printing the bottom surface and the side surface of the recess 7, the control of the film thickness and flatness of the second print layer formed on the bottom surface becomes accurate. Therefore, it is possible to improve the sensor sensitivity when a capacitive sensor is disposed on the bottom surface of the recess 7. The order of printing for the first to third print layers is not particularly limited. In addition, by changing the printing color or texture in the first printing layer, the second printing layer, and the third printing layer, the position of the sensor can be displayed visually intelligibly, and it can be used as an accent on the design. For example, when the first print layer and the second print layer are the same color and the third print layer is printed in a different color, the design can be such that the third print layer is recognized as an annular pattern.

  In addition, the printing method with respect to flat parts, such as the part in which the recessed part 7 is not formed in the back surface 5, and the bottom face of the recessed part 7, is not restricted to the thing by a screen printing method, if the film thickness etc. of a printing layer can be controlled accurately. Alternatively, a rotary screen printing method, a relief printing method, an offset printing method, a spray printing method, or the like may be used. Also, printing by electrostatic copying method, thermal transfer method, ink jet method or the like may be used.

  In addition, when the bottom surface of the recess 7 has a curved shape, such as when the bottom surface of the recess 7 protrudes in the Z direction toward the center, printing on the bottom surface can also be performed by the pad printing method. preferable.

  In addition, the printing method for the curved surface shape such as the side surface of the recess 7 or the bottom surface in the case of having a protruding shape is not limited to the pad printing method as long as the followability to the curved surface shape is good. For example, a spray printing method is adopted. May be.

  According to such a cover glass 1, a capacitance sensor or the like is provided on the back surface 15 of the thin portion 13 when it is incorporated in a housing or the like in order to protect an arbitrary surface (for example, a front surface or a side surface) of a portable information terminal or the like. Various devices can be arranged. Here, since the sensor incorporated in the back surface 15 of the thin wall portion 13 is protected by the thin wall portion 13 facing in the Z direction, the material is uniform and uniform without using different materials such as a sensor cover. The cover glass 1 excellent in a certain design property can be realized. Further, since the number of members is small and the assembly process can be simplified, there is a great effect in cost reduction.

(Method for manufacturing cover glass)
Next, the manufacturing method of the said cover glass 1 in case the cover glass 1 of this embodiment is chemically strengthened glass is demonstrated. First, the raw materials of each component are prepared so as to have the composition described later, and heated and melted in a glass melting furnace. The glass is homogenized by bubbling, stirring, adding a clarifying agent, etc., formed into a glass plate having a predetermined thickness by a conventionally known forming method, and gradually cooled. Examples of the glass forming method include a float method, a press method, a fusion method, a downdraw method, and a rollout method. In particular, a float method suitable for mass production is suitable. Further, continuous molding methods other than the float method, that is, the fusion method and the downdraw method are also suitable. The glass member formed into a flat plate shape by an arbitrary forming method is gradually cooled, then cut into a desired size (the size of the cover glass 1), and subjected to a polishing process. As a result, a glass member 101 having a flat surface 103 and a back surface 105 as shown in FIG.

  Next, as shown in FIG. 10, the concave portion 107 is provided by performing etching or machining on the back surface 105 of the glass member 101.

  The etching method may be either wet etching or dry etching, but wet etching is preferable from the viewpoint of cost. Examples of the etchant include a solution containing hydrofluoric acid as a main component in the case of wet etching, and a fluorine-based gas in the case of dry etching.

  The etching process is preferably performed while relatively moving the glass member 101 and the etchant in a direction parallel to the back surface 105 of the glass member 101 (XY direction). Such etching may be performed while the glass member 101 is swung in the XY directions, may be performed by causing the etchant to flow in the XY directions, or may be performed in combination. Since the etching process basically proceeds isotropically with respect to the glass member 101, the etching also proceeds in the lateral direction with a radius equal to the depth to be etched. Therefore, as shown in FIG. 11, when the recess 107 is formed by etching, the side surface 109 can be formed into a curved shape that smoothly connects to the bottom surface 108. As shown in FIG. 12, even when the concave portion 107 is formed on the surface 103, the side surface 109 can be formed into a curved surface shape that smoothly connects to the bottom surface 108 by the etching process.

  As shown in FIGS. 13 and 14, it is preferable that the connecting portion between the side surface 109 and the back surface 105 or the front surface 103 has a smoothly continuous curved surface shape. By making the connection portion into a curved surface without an edge, there is an effect of making it difficult to cause chipping or breakage due to dropping or contact with an external hard member. In order to make the connecting portion between the side surface 109 and the back surface 105 or the front surface 103 a smoothly continuous curved surface, the connecting portion can be finished by buffing or the like after the recess 107 is formed. However, in the case where the concave portion 107 is provided by wet etching, the connecting portion can be made smooth by keeping the time until the glass member 101 is extracted from the etchant and the mask is peeled and cleaned after the etching process. It can be a continuous curved surface. Etchant remains at the boundary between the side surface 109 of the recess 107 formed by etching and the mask due to surface tension, and etching proceeds slightly at the connection portion between the side surface 109 in contact with the remaining etchant and the back surface 105 or the surface 103. , The edge of the connection part becomes a smooth continuous curved surface. The holding time for that purpose is adjusted between several seconds to several tens of minutes depending on the etchant used and the etching resistance of the glass member 101.

  Further, as shown in FIG. 15, etching is performed while relatively moving the glass member 101 and the etchant in the direction parallel to the front surface 103 or the back surface 105 (XY direction) of the glass member 101 as described above. The bottom surface 108 of the recess 107 can be shaped to protrude toward the center. Thereby, the touch feeling of the protruded part improves. The thickness t in the Z direction of the central portion (the most protruding portion) of the protruding portion of the bottom surface 108 is preferably 5 μm or more and 20 μm or less. When the Z-direction thickness t of the protruding portion of the bottom surface 108 is 20 μm or more, there is a high possibility that the sensor erroneously recognizes, and when it is 5 μm or less, the change cannot be confirmed with the feeling of touch.

  The glass member 101 formed into a flat plate shape may be reheated and press-formed in a melted state, or the molten glass may be poured onto a press mold and press-formed to form the recess 107. . If the thickness of the thin portion 113 does not reach the required thickness only by press molding, the thickness can be adjusted by additionally etching the recess 107 or polishing the surface 114 side.

  The method of providing the concave portion 107 on one surface of the front surface 103 or the back surface 105 of the glass member 101 is not limited to the above-described etching method, and may be a machining method. In the machining method, a grinding stone is brought into contact with the front surface 103 or the back surface 105 of the glass member 101 using a machining center or other numerically controlled machine tool, and the concave portion 107 having a predetermined dimension is formed. For example, using a grindstone in which diamond abrasive grains, CBN abrasive grains or the like are fixed by electrodeposition or metal bond, the spindle rotation speed is 100 to 30,000 rpm, and the cutting speed is 1 to 10,000 mm / min. Grind with.

  Subsequently, the bottom surface 108 and the side surface 109 of the recess 107 may be polished. In the polishing process, the polishing process portion of the rotary polishing tool is brought into contact with the bottom surface 108 and the side surface 109 of the recess 107 separately at a constant pressure, and is moved relatively at a constant speed. By polishing under conditions of constant pressure and constant speed, the ground surface can be uniformly polished at a constant polishing rate. The pressure at the time of contact with the polishing portion of the rotary polishing tool is preferably 1 to 1,000,000 Pa in terms of economy and ease of control. The speed is 1 to 10,000 mm / min. In terms of economy and ease of control. Is preferred. The amount of movement is appropriately determined according to the shape and size of the glass member 101. The rotary polishing tool is not particularly limited as long as the polishing portion can be polished, and examples thereof include a method of attaching the polishing tool to a spindle and a router having a tool chucking portion. As a material of the rotary polishing tool, at least the polishing portion can process and remove a workpiece such as a cerium pad, a rubber grindstone, a felt buff, polyurethane, and the Young's modulus is preferably 7 GPa or less, more preferably 5 GPa or less. The type is not limited as long as it is present. By using a member with a Young's modulus of 7 GPa or less as the material of the rotary polishing tool, the bottom surface 108 and the side surface 109 can be processed to a desired surface roughness by deforming the polishing portion along the shape of the recess 107 by pressure. Examples of the shape of the polishing portion of the rotary polishing tool include a circular or donut-shaped flat plate, a cylindrical shape, a shell type, a disk type, and a barrel type.

  When polishing is performed by bringing the polishing processing portion of the rotary polishing tool into contact with the bottom surface 108 and the side surface 109 of the concave portion 107, it is preferable to perform the processing in a state where an abrasive grain slurry is interposed. In this case, examples of the abrasive grains include silica, ceria, alundum, white alundum (WA), emery, zirconia, SiC, diamond, titania, germania, and the particle size is preferably 10 nm to 10 μm. As described above, the relative movement speed of the rotary polishing tool is 1 to 10,000 mm / min. Can be selected within the range of The number of rotations of the polishing portion of the rotary polishing tool is 100 to 10,000 rpm. If the rotation speed is low, the processing rate will be slow, and it may take too much time to polish.If the rotation speed is high, the processing rate will be high, or the tool will be worn hard, making it difficult to control the polishing. There is.

  As described above, when the bottom surface 108 and the side surface 109 of the recess 107 are polished by bringing the rotary polishing tool into contact with each other with independent pressure, a pneumatic piston, a load cell, or the like can be used to adjust the pressure. For example, if a pneumatic piston that moves the rotary polishing tool back and forth toward the bottom surface 108 of the concave portion 107 and another pneumatic piston that moves the rotary polishing tool toward the side surface 109 of the concave portion 107 are provided, the bottom surface 108 of the concave portion 107 is provided. And the pressure of the polishing process part with respect to the side surface 109 can be adjusted. In this way, the pressures on the bottom surface 108 and the side surface 109 of the recess 107 are made independent, and the single rotary polishing tool is moved relatively at a constant speed while the rotary polishing tool is in contact with each surface at an independent constant pressure. Thus, each surface can be uniformly polished at an independent polishing rate at the same time.

  Note that polishing may be performed by relatively moving the rotary polishing tool and the glass member 101 along the shape of the recess 107. Any moving system may be used as long as the moving amount, direction, and speed can be controlled to be constant. For example, a method using a multi-axis robot or the like can be used.

  By providing the concave portion 107, the glass member 101 is formed with a thin portion 113 at a position overlapping the concave portion 107 in the X direction and the Y direction, and is connected to the peripheral portion of the thin portion 113, and more than the thin portion 113. A thick portion 117 having a large thickness in the Z direction is formed. At this time, the front surface 118 and the back surface 119 of the thick wall portion 117 and the front surface 114 and the back surface 115 of the thin wall portion 113 have a planar shape, and the front surface 118 and 114 of the thick wall portion 117 and the thin wall portion 113 constitute a flush shape, The thick portions 117 and the back surfaces 119 and 115 of the thin portion 113 form a step shape.

Subsequently, as shown in FIG. 16, the surface film and the back surface 115 of the thin portion 113 and the X-direction side surface (not shown) and the Y-direction side surfaces 111 and 111 of the concave portion 107 are surface films that suppress chemical strengthening of the respective portions. 121, a back film 122, and a side film 123 are formed. Examples of the method for forming these films 121, 122, and 123 include sputtering, CVD (Chemical Vapor Deposition), wet coating, and vapor deposition. Among these, the sputtering method is preferable from the viewpoints of film thickness uniformity, reproducibility, and film quality controllability. For example, in order to form the silicon dioxide (SiO ₂ ) films 121, 122, 123 by sputtering, silicon as a target may be sputtered in a mixed gas of oxygen and argon. Note that portions of the glass member 101 that do not require the films 121, 122, and 123 are masked with a mask member such as Kapton (registered trademark) tape before sputtering.

  Next, the glass member 101 is subjected to a chemical strengthening process to obtain a cover glass 1 as shown in FIG. The chemical strengthening treatment refers to a treatment of replacing (ion exchange) alkali ions (for example, sodium ions) having a small ion radius on the surface layer of glass with alkali ions (for example, potassium ions) having a large ion radius. The method of chemical strengthening treatment is not particularly limited as long as alkali ions on the surface layer of the glass can be ion-exchanged with alkali ions having a larger ionic radius. For example, a glass containing sodium ions is used as a molten salt containing potassium ions. This can be done by processing. Since such an ion exchange treatment is performed, the composition of the compressive stress layer on the glass surface layer is slightly different from the composition before the ion exchange treatment, but the composition at the center of the substrate thickness is almost the same as the composition before the ion exchange treatment. .

  When glass containing sodium ions is used as the glass to be chemically strengthened, it is preferable to use a molten salt containing at least potassium ions as the molten salt for performing the chemical strengthening treatment. As such a molten salt, for example, potassium nitrate is preferably exemplified. It is preferable to use a molten salt having a high purity.

  The molten salt may be a mixed molten salt containing other components. Examples of other components include alkali sulfates such as sodium sulfate and potassium sulfate, alkali chlorides such as sodium chloride and potassium chloride, carbonates such as sodium carbonate and potassium carbonate, sodium bicarbonate and potassium bicarbonate, etc. Bicarbonate etc. are mentioned.

  The heating temperature of the molten salt is preferably 350 ° C. or higher, more preferably 380 ° C. or higher, and still more preferably 400 ° C. or higher. The heating temperature of the molten salt is preferably 500 ° C. or lower, more preferably 480 ° C. or lower, and more preferably 450 ° C. or lower. By setting the heating temperature of the molten salt to 350 ° C. or higher, it is possible to prevent chemical strengthening from becoming difficult due to a decrease in the ion exchange rate. Moreover, decomposition | disassembly and deterioration of molten salt can be suppressed by heating temperature of molten salt to 500 degrees C or less.

  The time for bringing the glass into contact with the molten salt is preferably 1 hour or longer and more preferably 2 hours or longer in order to impart sufficient compressive stress. Moreover, in long-time ion exchange, while productivity falls and a compressive stress value falls by relaxation, 24 hours or less are preferable and 20 hours or less are more preferable. Specifically, for example, it is typical to immerse the glass in a molten potassium nitrate at 400 to 450 ° C. for 2 to 24 hours.

  In the cover glass 1 (cover glass) obtained by subjecting the glass member 101 to chemical strengthening treatment, a compressive stress layer is formed on the surface layer. The compressive stress (CS) of the compressive stress layer is preferably 300 MPa or more, and more preferably 400 MPa or more. CS can be measured using a surface stress meter (for example, FSM-6000 manufactured by Orihara Seisakusho).

  When ion exchange is performed between the sodium ions on the glass surface layer and the potassium ions in the molten salt by chemical strengthening, the depth of the surface compressive stress layer (DOL) generated by chemical strengthening can be measured by any method. EPMA (electron probe micro analyzer, electron beam microanalyzer) performs alkali ion concentration analysis in the depth direction of the glass (in this case, potassium ion concentration analysis), and the ion diffusion depth obtained by the measurement is expressed as DOL. Can be considered. DOL can also be measured using a surface stress meter (for example, FSM-6000 manufactured by Orihara Seisakusho). When ion exchange is performed between lithium ions on the glass surface layer and sodium ions in the molten salt, a sodium ion concentration analysis in the depth direction of the glass is performed with EPMA, and the ion diffusion depth obtained by the measurement is regarded as DOL. .

  The internal tensile stress (CT) of the cover glass 1 is preferably 400 MPa or less, more preferably 200 MPa or less, still more preferably 100 MPa or less, and most preferably 80 MPa or less. In general, CT is approximately obtained by the relational expression CT = (CS × DOL) / (t−2 × DOL) where t is the thickness of the cover glass 1. Therefore, since the thin portion 113 of the glass member 101 according to the present embodiment has a smaller thickness in the Z direction than the thick portion 117, when the thin portion 113 and the thick portion 117 are chemically strengthened under the same conditions, the cover after chemical strengthening The CT of the thin portion 13 of the glass 1 is larger than the CT of the thick portion 17.

  As described above, when the thin part 113 and the thick part 117 of the glass member 101 are chemically strengthened under the same conditions, the thin part 13 and the thick part 17 of the cover glass 1 have different CTs. It expands more than the thick part 17. Since the thin portion 13 expands in a state where the peripheral edge thereof is regulated by the thick portion 17, the thin portion 13 is deformed to the front side (see FIG. 17).

  Further, the front surface 3 and the back surface 5 of the cover glass 1 are preferably polished. A tempered glass plate subjected to chemical strengthening by ion exchange has defects on its surface. In addition, fine irregularities of up to about 1 μm may remain. When a force acts on the cover glass 1, stress concentrates at a location where the above-described defects and fine irregularities exist, and the cover glass 1 may break even with a force smaller than the theoretical strength. Therefore, a layer (defect layer) having defects and fine irregularities existing on the front surface 3 and the back surface 5 of the cover glass 1 after chemical strengthening is removed by polishing. In addition, although the thickness of the defect layer in which a defect exists is based also on the conditions of chemical strengthening, it is 0.01-0.5 micrometer normally. The polishing is performed by, for example, a double-side polishing apparatus. The double-side polishing apparatus has a carrier mounting portion having a ring gear and a sun gear that are driven to rotate at a predetermined rotation ratio, and a metal upper surface plate and a lower surface plate that are driven to rotate reversely with respect to the carrier mounting portion. The carrier mounting portion is mounted with a plurality of carriers that mesh with the ring gear and the sun gear. The carrier rotates around its own center and rotates in a planetary gear so as to revolve around the sun gear, and both surfaces (front surface 3 and back surface 5) of a plurality of cover glasses 1 attached to the carrier by planetary gear movement are on top. Polished by friction with surface plate and lower surface plate.

  The strain point of the glass member 101 before chemical strengthening is preferably 530 ° C. or higher. This is because when the strain point of the glass member 101 before chemical strengthening is set to 530 ° C. or higher, the surface compression stress is less likely to be relaxed.

Examples of the glass (glass member 101) used for chemical strengthening include any one of the following glasses (i) to (vii). In addition, the glass compositions of the following (i) to (v) are compositions expressed in mol% based on oxide, and the glass compositions of (vi) to (vii) are expressed in mass% based on oxide. Composition.
(I) SiO ₂ 50 to 80% of _{Al 2 O 3 2~25%, 0~10} % of Li ₂ O, the Na ₂ O 0~18%, 0~10% of _{K 2} O, MgO, 0-15%, glass containing 0-5% 0-5% and ZrO ₂ to the CaO.
(Ii) a SiO ₂ 50 to 74%, the _{Al 2 O 3 1~10%, 6~14} % of Na ₂ O, 3~11% of _{K 2} O, the MgO 2 to 15%, 0 to the CaO 6% and 0 to 5% of ZrO ₂ , the total content of SiO ₂ and Al ₂ O ₃ is 75% or less, the total content of Na ₂ O and K ₂ O is 12 to 25%, MgO and Glass whose total content of CaO is 7 to 15%.
(Iii) SiO ₂ and 68 to 80%, the _{Al 2 O 3 4~10%, 5~15} % of Na ₂ O, 0 to 1% of _{K 2} O, the MgO 4 to 15% and ZrO ₂ 0 Glass containing ˜1%, and the total content of SiO ₂ and Al ₂ O ₃ is 80% or less.
(Iv) a SiO ₂ 67 to 75%, the _{Al 2 O 3 0~4%, 7~15} % of Na ₂ O, 1~9% of _{K 2} O, the MgO having 6 to 14%, 0 to the CaO 1% and 0 to 1.5% of ZrO ₂ , the total content of SiO ₂ and Al ₂ O ₃ is 71 to 75%, the total content of Na ₂ O and K ₂ O is 12 to 20% Glass.
(V) a SiO ₂ 60 to 75%, the _Al 2 _{O 3 0.5~8%,} a Na ₂ O 10~18%, a _{K 2} O _0~5%, the MgO 6 to 15%, the CaO Glass containing 0-8%.
(Vi) a _{SiO 2 63~75%, Al 2 O} 3 3-12% of MgO 3 to 10% of CaO 0.5 to 10% 0 to 3% of SrO, and BaO 0 to 3% Na ₂ O 10-20%, K ₂ O 0-8%, ZrO ₂ 0-3%, Fe ₂ O ₃ 0.005-0.25%, R ₂ O / Al ₂ O ₃ (wherein R ₂ O is Na ₂ O + K ₂ O) is 2.0 or more and 4.6 or less.
(Vii) the _{SiO 2 66~75%, Al 2 O} 3 0-3% the MgO 1 to 9% 1 to 12% of CaO, 10 to 16% of Na ₂ O, 0 to a _{K 2} O Glass containing 5%.

  Up to this point, the cover glass 1 in which the peripheral edge (four side ends) of the thin portion 13 is connected to the thick portion 17 in the XY plane has been described. However, as shown in FIG. The structure connected to the thick part 17 may be sufficient. In this case, one end of the thin portion 13 (the end in the Y direction in the example of FIG. 18) is not connected to the thick portion 17 and is an open end. Further, as shown in FIG. 19, the two end portions of the thin portion 13 may be connected to the thick portion 17. In this case, the two ends of the thin portion 13 (both ends in the Y direction in the example of FIG. 19) are not connected to the thick portion 17 and are open ends. Further, as shown in FIG. 20, one end portion of the thin portion 13 may be connected to the thick portion 17. In this case, the three end portions of the thin portion 13 (Y direction end portions and X direction end portions in the example of FIG. 20) are not connected to the thick portion 17 and are open ends.

  Moreover, the shape of the recessed part 7 is not specifically limited, You may apply arbitrary shapes. For example, the cross-sectional shape of the recess 7 viewed from the Z direction is not limited to a rectangular shape, and for example, a circular shape or a triangular shape can be applied.

  The influence of the presence or absence of the surface film 21, the back film 22, and the side film 23 on the cover glass 1 on the warp of the thin portion 13 after chemical strengthening was tested.

Each cover glass 1 used in the test is expressed in terms of mol% based on oxides, and SiO ₂ is 64.4%, Al ₂ O ₃ is 8.0%, Na ₂ O is 12.5%, and K ₂ O is 4. A glass containing 0%, MgO 10.5%, CaO 0.1%, SrO 0.1%, BaO 0.1% and ZrO ₂ 0.5% was used. The dimensions of the cover glass 1 were X direction 35 mm × Y direction 35 mm × Z direction 0.7 mm. One concave portion 7 was provided on the back surface 5 of the cover glass 1 and its dimensions were 20 mm in the X direction × 10 mm in the Y direction × 0.5 mm in the Z direction. The dimension of the thin portion 13 was 20 mm in the X direction × 10 mm in the Y direction × 0.2 mm in the Z direction.

  Each cover glass 1 has all of the surface film 21, the back film 22, and the side film 23 in Examples 1 to 3 (see FIG. 3), and has the surface film 21 and the back film 22 in Example 4 (FIG. 4). Example 5 has a surface film 21 (see FIG. 5), and Example 6 has a back film 22 (see FIG. 6). Further, as Comparative Example 1, a cover glass 1 having no surface film 21, back film 22, and side film 23 was prepared. Further, as Comparative Example 2, as shown in FIG. 7, a surface film 21 was formed on the surface 18 of the thick portion 17 in addition to the surface 14 of the thin portion 13 (the surface film 21 on the entire surface 3 of the cover glass 1). A cover glass 1 was prepared.

The respective films 21, 22, and 23 of silicon dioxide (SiO ₂ ) were formed by sputtering. In Examples 1 to 3, the ratio of oxygen and argon during sputtering (O ₂ / Ar ratio) was changed to 100%, 80%, and 60%, respectively. The O ₂ / Ar ratio in Examples 4 to 6 and Comparative Example 2 was 100%.

  The chemical strengthening process was performed by immersing the cover glasses 1 according to Examples 1 to 6 and Comparative Examples 1 and 2 in 100% potassium nitrate molten salt at 425 ° C. for 6 hours. And in the cover glass 1 chemically strengthened, the maximum value of the curvature of the thin part 13, CS, and DOL, and CS and DOL of the thick part 17 were measured. In addition, about CS and DOL of the thin part 13, it measured on the surface 14 side and the back surface 15 side, respectively. The measurement results are shown in Table 1.

  In Table 1, a value indicated by “+” indicates warpage to the front side, and a value indicated by “−” indicates warpage to the back side. FIG. 17 shows a cross-sectional view of the cover glass 1 when the thin portion 13 is warped to the front side. In FIG. 17, the films 21, 22, and 23 are not shown. The maximum value of the warp of the thin portion 13 means “the maximum distance in the Z direction between the surface 14 of the thin portion 13 and the surface 18 of the thick portion 17”. The maximum value of the warpage was measured with a laser displacement meter (LT-9030 manufactured by Keyence Corporation). The CS and DOL of the thin portion 13 and the thick portion 17 were measured by a surface stress meter (FSM-6000 manufactured by Orihara Seisakusho). In Table 1, numerical values with “*” are numerical values obtained as a result of computer simulation. In Table 2, the numerical value with “**” is the same as the thin part 13 (X direction 20 mm × Y direction 10 mm × Z direction 0.2 mm) in 100% potassium nitrate molten salt at 425 ° C. It is a numerical value obtained by conducting chemical strengthening treatment by immersing the substrate in 6 hours and actually measuring it. Temporarily, when trying to obtain CS and DOL of the thin portion 13 of Comparative Example 1 by actual measurement in the same manner as in Examples 1 to 3, the warp maximum value of the thin portion 13 is very large, so that a correct value can be obtained. Can not.

When Examples 1 to 3 are compared, the warp of the thin portion 13 is suppressed in Examples 1 and 2 where the O ₂ / Ar ratio is 100% and 80% compared to Example 3 where the O ₂ / Ar ratio is 60%. . This is considered to be because the SiO ₂ film becomes denser and the thin-walled portion 13 becomes harder to chemically strengthen as the O ₂ ratio increases. In Examples 1 and 2, the warp maximum values of the thin-walled portion 13 are almost equal because in the film formed under the condition that the O ₂ / Ar ratio is 80% or more, there is no change in the density of the SiO ₂ film, This seems to be because there is not much change in the chemical strengthening suppression effect.

  When comparing Examples 1 to 6 in which the films 21, 22, and 23 are formed on at least one of the front surface 14 and the back surface 15 of the thin-walled portion 13, and Comparative Example 1 in which these films 21, 22, and 23 are not formed at all, In all Examples 1 to 6, it can be seen that the warp maximum value, CS, and DOL of the thin portion 13 are smaller than those of Comparative Example 1. In Examples 1 to 6, due to the films 21, 22, and 23, the thin portion 13 is less likely to be chemically strengthened than the thick portion 17, and CS and DOL of the thin portion 13 are CS and DOL of the thick portion 17. It is considered that the warpage of the thin portion 13 is also reduced.

  When Examples 1 and 4 were compared, it became clear that the warp maximum values, CS, and DOL of the thin portion 13 did not change much, and the presence or absence of the side film 23 did not significantly affect the warp of the thin portion 13.

  When Example 4 is compared with Examples 5 and 6, in Example 4 in which both the front surface film 21 and the back surface film 22 are formed, the warp maximum values, CS, and DOL of the thin portion 13 are reduced. I understand that. This is because in Example 4, the chemical strengthening of the front surface 14 and the back surface 15 of the thin portion 13 is suppressed, whereas in Example 5, the back surface 15 of the thin portion 13 is chemically strengthened. In Example 6, since the surface 16 of the thin portion 13 is chemically strengthened in Example 6, the CS and DOL on the surface 16 side are increased, and as a result, the maximum value of warpage is considered to be increased. The reason why the maximum warpage value of Example 5 is smaller than that of Example 6 is considered as follows. In Example 5, by forming the film 21 on the surface 14 side of the thin portion 13, the surface of the boundary between the region (I) where the film 21 is formed and the region (II) where the film is not formed is II. A force is exerted to extend from I to I (F1). On the other hand, on the back surface 15 side, a force that extends from the thin portion 13 toward the thick portion 17 acts on the boundary between the thin portion 13 and the thick portion 17 (-F2). In Example 6, by forming the film 22 on the back surface 15 side of the thin portion 13, the boundary between the thin portion 13 and the thick portion 17 tends to extend from the thick portion 17 toward the thin portion 13. Force to work (F3). On the other hand, on the surface 14 side, a force that tries to extend in the direction from I to II acts on the surface of the boundary between the region I and the region II (−F4). Since F1-F2 <F3-F4, the maximum value of warpage is smaller when the film 21 is formed on the surface 14 side of the thin portion 13.

  When Example 5 and Comparative Example 2 are compared, it can be seen that in Example 5, warping of the thin portion 13 is suppressed. In Comparative Example 2, it is considered that the surface 18 of the thick portion 17 is also coated, so that the chemical strengthening of the entire surface 3 of the cover glass 1 is less likely to enter than the back surface 5 and is thus greatly warped.

  As described above, it is preferable to form the films 21, 22, and 23 on at least one of the front surface 14 and the back surface 15 of the thin portion 13, and it is more preferable to form the films 21 and 22 on both the front surface 14 and the back surface 15. It became clear that it was preferable. It is also clear that the formation of the films 21 and 22 on the front surface 18 or the back surface 19 of the thick portion 17 is not preferable in terms of suppressing chemical strengthening of the thick portion 17 as well as the thin portion 13. It was.

DESCRIPTION OF SYMBOLS 1 Cover glass 3 Front surface 5 Back surface 7 Recess 9 X direction side surface 11 Y direction side surface 13 Thin part 14 Surface 15 Back surface 17 Thick part 18 Surface 19 Back surface 21 Surface film 22 Back surface film 23 Side film 101 Glass member 103 Surface 105 Back surface 107 Concave part 108 Bottom surface 109 Side surface 113 Thin portion 114 Front surface 115 Back surface 117 Thick portion 118 Front surface 119 Back surface

Claims (7)

A cover glass that protects a protection object,
The cover glass includes at least one thin portion formed by providing at least one concave portion on the front or back surface of the cover glass, and a thick portion connected to the thin portion,
A cover glass in which a film having a thickness of 10 to 1000 nm is formed on at least one of a front surface and a back surface of the thin portion.   The cover glass according to claim 1, wherein a surface compressive stress (CS) of a portion where the film is formed is smaller than a surface compressive stress of a compressive stress layer formed in the thick portion.   The cover glass according to claim 1, wherein a main component of the film is an oxide. The cover glass according to claim 3, wherein the oxide is SiO ₂ . By providing one concave portion on the front or back surface of the cover glass, one thin-walled portion is formed on the cover glass,
The thickness and area of the thin portion are t1 and s1, respectively.
When the thickness and area of the thick part are t2 and s2, respectively.
The cover glass according to any one of claims 1 to 4, wherein 0.05≤t1 / t2≤0.9 and 0.001≤s1 / s2≤0.9.   The portable information terminal which has a cover glass of any one of Claims 1-5. A cover glass manufacturing method for manufacturing a cover glass for protecting a protection target by chemically strengthening a glass member,
The glass member includes at least one thin portion formed by providing at least one concave portion on the front or back surface of the glass member, and a thick portion connected to the thin portion,
A film forming step of forming a film of 10 to 1000 nm on at least one of the front surface or the back surface of the thin portion;
After the film formation step, a chemical strengthening step for chemically strengthening the glass member,
A method for manufacturing a cover glass.

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