JP2005255452A - Panel glass for cathode ray tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a panel glass for a cathode ray tube less liable to elute alkali components from its surface and capable of preventing the deterioration of the glass surface even when kept for a long period. <P>SOLUTION: This panel glass for a cathode ray tube contains substantially no PbO, contains 50-70% SiO<SB>2</SB>, 1-3% Al<SB>2</SB>O<SB>3</SB>, 0.3-1.5% MgO, 0.3-1.5% CaO, 7-10% SrO, 7-10% BaO, less than 0.2-1.0% ZnO, 5-10% Na<SB>2</SB>O, 5-10% K<SB>2</SB>O, 0-3% ZrO<SB>2</SB>, 0-3% TiO<SB>2</SB>, 0-3% CeO<SB>2</SB>, 0-2% Sb<SB>2</SB>O<SB>3</SB>, and 1.0-3.0% MgO+CaO+ZnO by mass percentage, and has an X-ray absorption coefficient at 0.6Å of not smaller than 28.0 cm<SP>-1</SP>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a panel glass for a cathode ray tube used for a color television tube.

  The envelope of the cathode ray tube includes a panel portion on which an image is projected, a tubular neck portion on which an electron gun is mounted, and a funnel-shaped funnel portion connecting the panel portion and the neck portion. The electron beam emitted from the electron gun causes the phosphor provided on the inner surface of the panel unit to emit light and display an image on the panel unit. At this time, braking X-rays are generated in the tube, and this is generated outside the tube through the envelope. This type of envelope is required to have a high X-ray absorption capability because leakage will adversely affect the human body.

  In order to increase the X-ray absorption coefficient of the glass, PbO may be contained in the glass. However, when the glass containing PbO is used as a panel glass, it is caused by the electron beam and X-ray irradiation generated when displaying an image. Coloring called “browning” occurs, and the image becomes difficult to see.

Therefore, in order to suppress browning, a panel glass for a cathode ray tube in which SrO and BaO are contained in a large amount in place of PbO has been developed.
JP 2001-32885 A

  By the way, in recent years, thin displays such as liquid crystal displays and plasma displays have become mainstream as display devices, and the amount of cathode ray tubes used for color television tubes has been decreasing. Therefore, glass products used for the panel glass, funnel glass, and neck glass constituting the cathode ray tube have been stored in warehouses for a long period of time.

  When these glasses are stored in a warehouse for a long period of time, alkali components are eluted from the surface of the glass product by moisture in the air, and the eluted alkali components erode the glass, thereby reducing the surface quality of the glass. In particular, in the case of panel glass, when the surface quality of the glass is lowered, there arises a problem that an image becomes difficult to see.

In a glass containing an alkaline component such as Na ₂ O or K ₂ O, such as a cathode ray tube panel glass, in order to suppress elution of the alkaline component, the content of the alkaline component may be reduced. When the content of is reduced, there arises a problem that a thermal expansion coefficient matching with the funnel glass cannot be obtained.

  An object of the present invention is to provide a panel glass for a cathode ray tube which is difficult to elute an alkali component from the glass surface even when stored for a long period of time, and can prevent the deterioration of the surface quality of the glass.

The cathode ray tube panel glass of the present invention substantially does not contain PbO, and is in a mass percentage of SiO ₂ 50 to 70%, Al ₂ O ₃ 1 to 3%, MgO 0.3 to 1.5%, CaO 0. 0.3 to 1.5%, SrO 7 to 10%, BaO 7 to 10%, ZnO 0.2 to less than 1.0%, Na ₂ O 5 to 10%, K ₂ O 5 to 10%, ZrO ₂ 0 -3%, TiO ₂ 0-3%, CeO ₂ 0-3%, Sb ₂ O ₃ 0-2%, MgO + CaO + ZnO 1.0-3.0%, and the X-ray absorption coefficient at 0.6% is 28. It is 0 cm ⁻¹ or more.

  Even when the panel glass for a cathode ray tube of the present invention is stored for a long period of time, it is difficult for an alkali component to elute, so that a reduction in the surface quality of the glass can be prevented. Therefore, it is suitable as a panel glass for a cathode ray tube, particularly as a panel glass for a cathode ray tube used for a color television tube.

  Since the cathode ray tube panel glass of the present invention contains MgO, CaO, and ZnO as essential components, the glass can be used without reducing the content of alkali components to obtain a thermal expansion coefficient that matches the funnel glass. The elution of the alkaline component can be suppressed.

  When MgO, CaO, and ZnO are contained in the glass, the crack resistance of the glass is usually lowered, and the glass is easily damaged and broken in the transport process and the like. By limiting the percentage to MgO 0.3-1.5%, CaO 0.3-1.5%, ZnO 0.2-1.0%, MgO + CaO + ZnO 1.0-3.0% While suppressing the elution of components, it is possible to prevent a decrease in the crack resistance of the glass.

  In addition, as for the concrete value about the elution of the alkaline component of the panel glass for cathode ray tube of the present invention, it is desirable that the elution amount of the alkaline component in the test based on JIS R3502 is 0.5 mg or less, and the crack resistance of the glass As for the properties, it is desirable that the pressure load (crack resistance) is 20 g or more when an indentation is made in the glass with a Vickers indenter and the crack generation rate generated from the indentation becomes 50%.

In addition, the cathode ray tube panel glass of the present invention needs to have an X-ray absorption coefficient of 28 cm ⁻¹ or more at a wavelength of 0.6 mm. This is because if the X-ray absorption coefficient is smaller than 28 cm ^{−1, the} amount of X-ray transmission increases so much that the human body may be adversely affected. In addition, what is necessary is just to contain 7% or more of SrO and BaO in glass, respectively, in order to raise an X-ray absorption coefficient.

  The reason why the glass composition is limited as described above in the present invention is as follows.

  PbO is a component that enhances the X-ray absorption ability of glass. However, when PbO is contained, coloring called browning is caused by electron beam and X-ray irradiation, so that introduction into a substantial glass should be avoided. In addition, substantial introduction into glass means that PbO is 0.1% or less.

SiO ₂ is a glass network former. When the content increases, the viscosity of the glass becomes high and melting becomes difficult, or the coefficient of thermal expansion becomes too small, and the consistency with the funnel glass tends to be difficult. On the other hand, when the content is reduced, the viscosity of the glass becomes low and molding becomes difficult, or the coefficient of thermal expansion becomes too large, and the consistency with the funnel glass tends to be difficult. When the content of SiO ₂ is 50% to 70%, without deteriorating the meltability and formability of the glass, glass having a thermal expansion coefficient matching the funnel glass can be easily obtained. A preferred range is 53-67%.

Al ₂ O _{3 is} also a component that becomes a glass network former. When the content increases, the viscosity of the glass becomes high and melting becomes difficult, or the coefficient of thermal expansion becomes too small, and the consistency with the funnel glass tends to be difficult. On the other hand, when the content is reduced, the viscosity of the glass becomes low, and molding becomes difficult, or the coefficient of thermal expansion becomes too large, so that consistency with the funnel glass tends to be difficult. If the content of Al ₂ O ₃ is 1 to 3%, it becomes easy to obtain a glass having a thermal expansion coefficient that matches the funnel glass without deteriorating the meltability and formability of the glass. A preferable range is 1.2 to 2.8%.

  MgO and CaO are components that suppress elution of alkali components from glass. When each content increases, the crack resistance of the glass is lowered, and the glass is easily damaged and broken in the transporting process and the like. On the other hand, when the content decreases, it becomes difficult to obtain the effect of suppressing the elution of the alkali component from the glass. If the content of MgO and CaO is 0.3 to 1.5%, elution of alkali components from the glass can be suppressed without reducing the crack resistance of the glass. Preferable ranges are each 0.4 to 1.4%.

  SrO and BaO are components that facilitate melting of the glass, adjust the thermal expansion coefficient and viscosity, and increase the X-ray absorption ability. When each content increases, the glass tends to be devitrified and difficult to be molded. On the other hand, when the content decreases, sufficient X-ray absorption ability tends to be difficult to obtain. If the content of SrO and BaO is 7 to 10%, respectively, it becomes easy to obtain a glass having a sufficient X-ray absorption coefficient without devitrification. Preferable ranges are 7.2 to 9.8%, respectively.

  ZnO is a component that suppresses elution of alkali components from the glass and increases the X-ray absorption ability. When the content is increased, the glass tends to be devitrified and difficult to be molded, or the crack resistance of the glass is lowered, and the glass is easily damaged and broken in the transport process or the like. On the other hand, when the content decreases, it becomes difficult to obtain an effect of suppressing elution of alkali components from the glass and sufficient X-ray absorption ability. If the content of ZnO is less than 0.2 to 1%, the glass is not devitrified and the crack resistance of the glass is not lowered, and the effect of suppressing elution of alkali components from the glass and sufficient X-ray absorption. It becomes easy to obtain glass having a coefficient. A preferable range is 0.22 to 0.6%.

Na ₂ O and K ₂ O are components that adjust the thermal expansion coefficient and viscosity. If each content increases, the thermal expansion coefficient becomes too large, making it difficult to achieve consistency with the funnel glass, and the viscosity becomes too low to make molding difficult. In addition, the electrical insulation tends to decrease. On the other hand, when the content is reduced, the thermal expansion coefficient is lowered, and it tends to be difficult to match the thermal expansion coefficient of the funnel glass. Na 2 _O, content of _K 2 _O, if 5-10%, respectively, formability, without reducing the electrical insulation, the glass tends to give having a thermal expansion coefficient matching the funnel glass. Preferable ranges are 6 to 9%, respectively.

ZrO ₂ is a component that adjusts the thermal expansion coefficient and viscosity, and further increases the X-ray absorption ability. When the content increases, the glass tends to be devitrified and difficult to mold. If the content of ZrO ₂ is 0 to 3%, the glass having a sufficient X-ray absorption coefficient is easily obtained without devitrification. A preferable range is 0 to 2.5%.

TiO ₂ is a component that suppresses ultraviolet coloring of glass. The effect can not be obtained remarkably be contained more than the TiO ₂ 3%, the raw material cost becomes high. A preferable range is 0 to 2%.

CeO ₂ is a component that suppresses X-ray coloring of glass. Even if CeO ₂ is contained in an amount of more than 3%, the effect cannot be obtained remarkably, and the raw material cost increases. A preferable range is 0 to 2%.

Sb ₂ O ₃ is a component that acts as a fining agent. Even if Sb ₂ O ₃ is contained in an amount of more than 2%, the effect cannot be remarkably obtained, and the raw material cost increases. A preferable range is 0 to 1%.

  In order to achieve both suppression of elution of alkali components from the glass and prevention of crack resistance reduction, it is important that the total amount of MgO, CaO and ZnO is 1.0 to 3.0%. When the total amount of these components is reduced by 1.0%, it is difficult to obtain the effect of suppressing the elution of alkali components from the glass. On the other hand, when it exceeds 3.0%, the crack resistance of the glass is lowered, and the glass is easily damaged and broken in the transporting process and the like.

In addition to the above components, it is possible to add other components as long as the properties of the glass are not impaired. For example, P ₂ O ₅ is added up to 0.5% as a component for suppressing devitrification. Also good. Further, as the coloring agent, CoO, may be added to NiO and _Fe 2 _{O 3} up to 1% in total. However, Li ₂ O, which is a component that adjusts the coefficient of thermal expansion and viscosity, is the most easily eluted component among the alkali components, so it is desirable to avoid substantial introduction into glass. Note that the introduction of substantial glass, Li 2 _O is meant that 0.1% or less.

  Hereinafter, the panel glass for a cathode ray tube of the present invention will be described in detail based on examples.

  Tables 1 and 2 show examples (samples Nos. 1 to 5) and comparative examples (samples Nos. 6 to 8) of the present invention.

  Each sample in the table was prepared as follows.

  First, the raw material batch prepared so that it might become the glass composition in a table | surface was put into the platinum crucible, and it melted at about 1500 degreeC for 4 hours. In order to obtain homogeneous glass, defoaming was carried out by stirring for 3 minutes using a platinum stirring rod in the middle. Thereafter, the molten glass was formed into a predetermined shape and then gradually cooled.

  About each sample obtained in this way, the elution amount of the alkaline component, crack resistance and X-ray absorption coefficient were measured, and the results are shown in the table.

As can be seen from the table, the sample No. In each of the samples 1 to 5, the elution amount of the alkali component was as low as 0.5 mg or less, the crack resistance was 21 g or more, and the crack resistance was excellent. Furthermore, the X-ray absorption coefficient was as high as 29 cm ⁻¹ .

  On the other hand, sample No. which is a comparative example. 6 and no. In No. 7, the elution amount of the alkali component is as high as 0.6 mg or more, and the surface quality of the glass is expected to be lowered. Sample No. No. 8 has a crack resistance as low as 18 g, is inferior in crack resistance, and is expected to be easily scratched and easily cracked in the conveying process or the like.

  In addition, about the elution amount of the alkali component, it measured by the test method based on JISR3502. Specifically, each sample is first crushed and classified, and a crushed material having a size of 250 to 425 μm is taken out. Next, the crushed material is washed with water, transferred to a beaker, and dried in a dryer. Further, 2.8 g of this crushed material was placed in a round bottom flask together with 50 ml of pure water and kept in a boiling water bath for 60 minutes. Then, the alkaline component in the solution was quantified with an atomic absorption analyzer to determine the elution amount.

  As for the crack resistance, the method proposed by Wada et al. (M. Wada et al. Proc., The Xth ICG, vol. 11, Ceram. Soc., Japan, Kyoto, 1974, p39) was used. In this method, a sample glass is placed on the stage of a Vickers hardness tester, and a diamond-shaped diamond indenter is pressed against the surface of the sample glass with various loads for 15 seconds. Then, the number of cracks generated from the four corners of the indentation was counted up to 15 seconds after unloading, and the ratio to the maximum number of cracks (4) that could be generated was determined to obtain the crack generation rate. Further, the load when the crack occurrence rate was 50% was defined as “crack resistance”. A large crack resistance means that cracks are unlikely to occur even under high loads, that is, excellent crack resistance.

  The crack occurrence rate was measured 20 times with the same load, and the average value was obtained. The measurement conditions were a temperature of 25 ° C. and a humidity of 30%.

  The X-ray absorption coefficient was obtained by calculating the absorption coefficient for a wavelength of 0.6 mm based on the glass composition and density.

Claims (1)

Substantially free of PbO and in mass percentage, SiO ₂ 50-70%, Al ₂ O ₃ 1-3%, MgO 0.3-1.5%, CaO 0.3-1.5%, SrO 7~10%, BaO 7~10%, ZnO less than _{0.2~1.0%, Na 2 O 5~10%} , K 2 O 5~10%, ZrO 2 0~3%, TiO 2 0~3 %, CeO ₂ 0 to 3%, Sb ₂ O ₃ 0 to 2%, MgO + CaO + ZnO 1.0 to 3.0%, and the X-ray absorption coefficient at 0.6% is 28.0 cm ⁻¹ or more. Panel glass for a cathode ray tube.