JP2011141568A - Protective plate for portable apparatus display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protective plate for a portable apparatus display device, the plate sufficiently protecting a display even when the thickness of the plate is reduced. <P>SOLUTION: The protective plate for a portable apparatus display device includes a sheet glass having a Young's modulus of not less than 75 GPa. The protective plate for a portable apparatus display device includes a sheet glass containing a composition composed of, by mass%, 50 to 75% of SiO<SB>2</SB>, 15 to 25% of Al<SB>2</SB>O<SB>3</SB>and 15 to 30% of Al<SB>2</SB>O<SB>3</SB>+MgO+ZnO. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a protective plate for protecting a display device of a portable device from damage or the like.

  In recent years, portable devices, particularly mobile phones, digital cameras, and personal digital assistants (PDAs) have been reduced in size, weight, and thickness. On the other hand, these displays have been increased in size. As such a display, a liquid crystal display (LCD) or an organic EL display (OELD) is mainly used.

  These displays are more susceptible to impacts and external forces in handling than displays that are fixed and used, such as television and personal computer monitors. For example, when an external force is applied to the LCD, image disturbance called “paddling” may occur, or the glass substrate may be damaged. Therefore, in order to protect the display, a transparent resin plate (protection plate) is installed in parallel with the display via a certain width interval (see, for example, Patent Document 1).

However, when the resin plate is used for a long period of time, the resin deteriorates and the transparency is lowered, or the surface is soiled or scratched, which makes it difficult to see the display. In order to solve such problems, it has been proposed to use a glass plate as a protective plate instead of a resin plate (see, for example, Patent Document 2).
JP 2004-299199 A JP 2003-140558 A

  As described above, a protective plate made of glass is required to have low transparency and be less susceptible to dirt and scratches. In recent years, however, the thickness of the protective plate itself has been increasing in order to reduce the thickness of portable devices. Thinning is required.

  However, if the thickness of the protective plate made of glass is reduced, the protective plate is likely to be broken and is easily bent and may not function as a protective plate.

  An object of the present invention is to provide a protective plate for a portable device display device that can sufficiently protect a display even when the wall thickness is reduced.

As a result of intensive studies, the inventors of the present invention added a large amount of Al ₂ O ₃ (15 to 25%) to the glass composition, and the glass plate is less likely to bend, and the effect of chemical strengthening is increased and is not easily damaged. The present invention is found and proposed as the present invention.

  The protective plate for a portable device display device of the present invention is characterized by comprising a plate glass having a Young's modulus of 75 GPa or more.

Moreover, the protective plate for portable device display devices of the present invention is a plate glass containing a composition of SiO ₂ 50 to 75%, Al ₂ O ₃ 15 to 25%, Al ₂ O ₃ + MgO + ZnO 15 to 30% in terms of mass%. It is characterized by comprising.

  Since the protective plate for a portable device display device of the present invention includes a plate glass having a Young's modulus of 75 GPa or more, it is difficult to bend and break even if it is thin. As a result, the display can be sufficiently protected even if the wall thickness is reduced, so that the mobile device itself can also be thinned.

  The Young's modulus is preferably 78 GPa or more, and more preferably 80 GPa or more.

  The protective plate for a portable device display device of the present invention is preferable because the hardness of the plate glass is not less than 500 Hv, so that the surface is not easily scratched. More preferably, it is 600 Hv or more, and further preferably 650 Hv or more.

  The protective plate for a portable device display device of the present invention is preferable because it is difficult to break if it is reinforced. In particular, it is preferable that the surface stress value is 700 MPa or more because the effect of preventing breakage is excellent.

As a method of strengthening the protective plate, a method of rapidly cooling from a temperature above the strain point (physical strengthening), or an alkali metal ion (for example, Li ⁺ or Na ⁺ ) contained in the protective plate is an alkali metal having a large ion radius. A method of ion exchange (chemical strengthening) with ions (for example, K ⁺ ) is widely used, but the method of ion exchange is preferable because it can impart a large compressive stress and is less likely to break.

  In the protective plate for a portable device display device of the present invention, it is preferable that an antireflection film is formed on at least one side (especially the outer surface side) because there are few reflections and images and videos on the display device are easy to see.

  In addition, when a transparent conductive film is formed on the protective plate for a portable device display device of the present invention, it is possible to shield electromagnetic waves, and it is difficult to be charged, so that dirt such as dust is difficult to adhere. As the transparent conductive film, oxides such as tin-containing indium oxide (ITO), antimony-containing indium oxide, and fluorine-containing indium oxide, and metal thin films such as aluminum, gold, and silver can be used.

  The protective plate for a portable device display device of the present invention is preferably formed with a scattering prevention film because fragments are hardly scattered even if the glass sheet is broken. The anti-scattering film may be formed on either side, but it is preferable that the anti-scattering film is formed on the outer surface side because it is excellent in the effect of preventing debris from scattering.

When the protective plate for portable device display device of the present invention is made of glass containing a composition of SiO ₂ 50 to 75%, Al ₂ O ₃ 15 to 30%, Al ₂ O ₃ + MgO + ZnO 15 to 30% by mass%. The Young's modulus is large and is difficult to bend.

SiO ₂ is a component that forms a glass skeleton. If it is less than 50%, the weather resistance tends to be difficult to obtain, and if it exceeds 80%, the viscosity of the glass tends to be high, so that melting tends to be difficult, and the liquidus temperature rises and molding becomes difficult. Cheap. Preferably it is 55-75%, More preferably, it is 60-70%, More preferably, it is 62-68%.

Al ₂ O ₃ is also a component that enhances Young's modulus and facilitates ion exchange and strengthening. If the amount is less than 15%, the above effect tends to be hardly obtained. If the amount is more than 30%, the viscosity of the glass becomes high, so that melting becomes difficult, and the liquidus temperature rises, so that molding becomes difficult. . Preferably it is 17 to 28%, more preferably 20 to 25%.

Al ₂ O ₃ , MgO, and ZnO are components that increase the Young's modulus. If the total amount of these components is less than 15%, the Young's modulus tends to be insufficient, and if it exceeds 33%, it is difficult to melt or devitrification tends to occur, such being undesirable.

  MgO is not an essential component but can be added up to a content of 5%. If it exceeds 5%, devitrification tends to occur and molding is difficult. The content is preferably 4% or less, and more preferably 3.5% or less.

  ZnO is not an essential component but can be added up to a content of 5%. If it exceeds 5%, devitrification tends to occur. The content is preferably 4% or less, and more preferably 3.5% or less.

  In addition to the above, the following components can be added.

Li ₂ O is a component used for strengthening the glass by ion exchange and increasing the meltability, and can be added up to 6%. If the content is more than 6%, the glass tends to be devitrified, or it may become cloudy due to phase separation. The content is preferably 5.5% or less, and more preferably 5.2% or less.

Na ₂ O is also a component used to strengthen the glass by ion exchange and to increase the meltability, and can be added up to 5%. If the content is more than 5%, the Young's modulus may decrease, such being undesirable. The content is preferably 4.5% or less, and more preferably 4.2% or less.

Since Li ₂ O and Na ₂ O are components strengthened by ion exchange with K ⁺ , the content is preferably 1% or more. If it is less than 1%, it is not preferred because it is not sufficiently strengthened even if ion exchange with K ⁺ is performed.

K ₂ O is a component that enhances the meltability and increases the thermal expansion coefficient, and can be added up to 5%. If the content is more than 5%, the Young's modulus may decrease, which is not preferable. The content is preferably 4.5% or less, and more preferably 4.2% or less.

  CaO, SrO, and BaO are components that increase the meltability, but are also components that easily cause devitrification. Therefore, these components can be added up to 8% in total. It is preferably 7% or less, and more preferably 6.5% or less.

TiO ₂ is a component that lowers the glass viscosity at high temperatures and imparts weather resistance, but is a component that easily causes devitrification, and can be added up to 8%. It is preferably 6% or less, and more preferably 4% or less.

ZrO ₂ is a component that imparts weather resistance, but is also a component that is easily devitrified and difficult to melt, and can be added up to 7%. It is preferably 5% or less, and more preferably 4% or less.

P ₂ O ₅ is a component that suppresses the occurrence of devitrification, but can be added up to 7% because it is a component that is easily phase-separated. It is preferably 5% or less, and more preferably 4% or less.

As ₂ O ₃ , Sb ₂ O ₃ , Sb ₂ O ₅ , SO ₃ , Cl and F may be added up to 2% each as a fining agent, but As ₂ O ₃ is not contained because it is an environmentally hazardous substance. It is preferable.

The total content of colored oxides such as Fe ₂ O ₃ , CuO, CoO, Cr ₂ O ₃ and NiO is preferably 1% or less. The total content is more preferably 0.7% or less, and further preferably 0.5% or less.

  Hereinafter, the present invention will be described in detail using examples and comparative examples.

  Table 1 shows the glass composition and characteristics of each sample, Table 2 shows the amount of deflection of each sample, and Table 3 shows the characteristics before and after chemical strengthening.

  Each sample (Example and Comparative Example 1) was produced as follows.

  First, after preparing a glass raw material so that it might become a composition of Table 1, it injected | threw-in to the platinum crucible and it was set as the molten glass using the electric furnace at 1600 degreeC for 5 hours.

  Next, the molten glass was poured out onto the carbon plate, and a glass plate having a thickness of 1.2 mm was produced using a roller.

  Finally, after annealing at 650 ° C., the surface was optically polished to prepare a sample.

  The Young's modulus was measured by a resonance method by preparing a 20 × 40 × 1 mm sample. As a measuring device, a nondestructive elastic modulus measuring system (Kanebo KI-11) was used.

  The hardness was measured 10 times using a micro hardness meter (Matsuzawa Seiki MXT-50), and the average was calculated.

  For the average transmittance, a 40 × 40 × 0.7 mm sample was prepared, and the transmittance at each wavelength of 400 to 700 nm was measured at a slit width of 2 nm using a spectrophotometer (UV-3100PC manufactured by Shimadzu Corporation). Calculated on average.

  The density was measured by the well-known Archimedes method.

  Next, the amount of deflection was measured as follows.

  First, each sample shown in Table 2 was prepared and arranged on a frame in which each side of the sample was supported with a width of 1 mm.

  Next, a 10 N load was applied in the direction perpendicular to the sample surface with a rod having a square cross section of 10 mm × 10 mm at the center of the sample, and the amount of displacement at the center was measured as the amount of deflection.

  Next, five samples each of 35 × 35 × 0.70 mm were prepared for the samples of Example and Comparative Example 1, and immersed in the potassium nitrate melt under the conditions described in Table 3.

  Using a surface stress meter (FSM-60 manufactured by Toshiba), it was confirmed that a compressive stress layer was formed on the sample surface, and the stress value and the depth thereof were measured.

  In addition, the immersed sample is placed on a smooth ring with an inner diameter of 25 mm, and a load is applied to the center of the sample using a smooth indenter with a diameter of 12.5 mm until it breaks. Calculated as the average breaking strength.

  As is clear from Table 1, the Young's modulus of Example 1 was 81 GPa, the Young's modulus of Example 2 was 82 GPa, and Comparative Example 1 was 70 GPa.

  Further, as is apparent from Table 2, in the sample of the same size, the example has a smaller amount of deflection than the comparative example 1. For this reason, since the embodiment can reduce the thickness of the sample itself or the distance from the display, it is effective for reducing the thickness of the portable device.

  Further, as apparent from Table 3, Example 1 and Example 2 after strengthening had higher average fracture strength than Comparative Example 1 after strengthening.

  The protective plate for a portable device display device according to the present invention can be used as a protective plate for a display such as a portable game machine, a portable music player, an IC recorder, and an electronic dictionary as well as a mobile phone, a digital camera, and a PDA.

Claims (6)

  A protective plate for a portable device display device, comprising a plate glass having a Young's modulus of 75 GPa or more.   The protective plate for a portable device display device according to claim 1, wherein the plate glass is physically strengthened or chemically strengthened.   The protective plate for a portable device display device according to claim 1, wherein the plate glass has a surface stress value of 700 MPa or more.   The protective plate for a portable device display device according to any one of claims 1 to 3, wherein an anti-scattering film is attached to the surface of the plate glass. For a portable device display device comprising a plate glass containing a composition of SiO ₂ 50-80%, Al ₂ O ₃ 15-30%, Al ₂ O ₃ + MgO + ZnO 15-30% in terms of mass%. Protective plate. Glass sheet represented by _mass%, claims 1 to 4, characterized in that it consists of glass containing _{SiO 2 50~80%, Al 2 O} 3 15~30%, a composition of _{Al 2 O 3 + MgO + 15~30} % ZnO A protective plate for a portable device display device according to any one of the above.