JPS6340350B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to panel glass used in color cathode ray tubes, and in particular to this type of glass having X-ray absorption characteristics and light selective absorption characteristics as well as a required chromaticity value. On the inner surface of the panel glass of a color cathode ray tube,
A set of red, green, and blue phosphors are arranged in a large number of dots or stripes to form a phosphor surface. By applying an electron beam emitted from an electron gun to this fluorescent surface through a shadow mask or aperture grill, a color image is observed through the panel glass. By the way, when this color image is viewed through a panel glass, external light existing around the viewer, such as sunlight incident through a window or indoor lighting such as a fluorescent light, enters the fluorescent surface through the panel glass. ,
There is a problem in that it significantly reduces the contrast of images made up of red, green, and blue light. Furthermore, such incident external light is reflected by the inner surface of the panel glass, causing so-called secondary reflection, causing a virtual image of objects such as indoor fixtures around the cathode ray tube to be seen, making it difficult to see the image. Conventionally, panel glass has been coated with NiO and CoO to prevent contrast degradation caused by external light.
It has been done to color the glass by adding a small amount of it to lower the transmittance of the glass. This colored glass has a neutral gray chromaticity. However, this neutral gray glass reduces transmittance almost uniformly over the entire visible wavelength range, including the red, green, and blue emission spectra, so The problem was that the brightness of the image was reduced as the light was also absorbed. The panel glass of a color cathode ray tube sufficiently transmits colors with wavelengths corresponding to the red, green, and blue fluorescence spectrum of the phosphor, but light with other wavelengths,
In particular, it is desirable to use glass that sufficiently absorbs yellow light, which is most sensitive to the human eye. Another method to prevent contrast deterioration due to external light is to add 3 to 5 wt% to Na ₂ O-CaO-SiO _2- based panel glass or filter glass.
The addition of Nd ₂ O ₃ to impart photoselective absorption properties is disclosed in GB 1154500. That is, the addition of Nd ₂ O ₃ allows red, green, and blue light to pass through well, but reduces the transmittance of yellow light. Adding Nd ₂ O ₃ to panel glass is also described in West German Patent No. 1286539, and
U.S. Patent No. 3143683 also describes Na ₂ O−CaO−
0.05-0.4wt% Fe ₂ O ₃ in SiO ₂ -based panel glass,
0.3~1.2wt% _Nd2O3 , 0.01~0.05wt _% NiO, 0.02
The addition of ~0.06 wt% CoO and 0.002-0.02 wt% Se has been shown to obtain the desired transmittance properties. However, none of the glasses disclosed in the British, West German, and American patent specifications have a high
It does not have radiation absorption properties, nor is it a glass that prevents browning due to X-rays or electron beams. Color cathode ray tubes usually have problems with X-ray leakage and discoloration of the panel glass because the panel is irradiated with electron beams. To solve such problems, SrO, BaO, PbO, ZnO, _ZrO2 and _WO3
For example, a panel glass comprising at least one of
It is disclosed in Specification No. 3663246 and Specification No. 3723354, and has also been put into practical use. By the way, when using a panel glass containing Nd ₂ O ₃ as shown in the above-mentioned British patent, West German patent, and US patent (No. 3143683), due to its light selective absorption characteristics, the contrast of the image may be affected by external light. However, such Nd ₂ O ₃
does not exhibit a neutral gray color upon irradiation with the tricolor fluorescent material P22. Therefore, there is a drawback that the light actually emitted from each of the red, green, and blue phosphors is not transmitted correctly. Moreover, such Nd ₂ O ₃ -containing glasses exhibit dichroism, ie, they appear to have different colors depending on the type of neutral light source with which they are irradiated. For example, under sunlight,
It looks like a pinkish color, but under a fluorescent light it looks bluish. Therefore, the image projected by a cathode ray tube using such a panel glass has the drawback that the color tone and contrast change depending on whether the image is viewed under sunlight or fluorescent light. Therefore, it is possible to simply add Nd ₂ O ₃ to a panel glass that has the X-ray absorption characteristics shown in the above-mentioned U.S. patents and prevents browning, in accordance with the teachings of the above-mentioned British patent specifications, etc. , it is impossible to obtain a panel glass that exhibits a neutral gray color and does not have dichroism when exposed to P22 irradiation. In addition, in color cathode ray tubes, the wall thickness of the panel glass differs between large tubes and small tubes, and in order to reduce the change in chromaticity of the color cathode ray tube image due to the difference in panel glass thickness, the wall thickness of the panel glass is different. It is desirable to use panel glass that exhibits small changes in chromaticity due to changes in thickness. In view of the above points, an object of the present invention is to provide a light selective transmission-absorption property that sufficiently transmits red, green, and blue light emitted from a phosphor and sufficiently absorbs light of other wavelengths, especially yellow light. It also has the required chromaticity and does not exhibit dichroism, making it possible to obtain high-contrast, high-luminance color images, and preventing secondary reflection of external light. An object of the present invention is to provide a panel glass for a cathode ray tube that exhibits small changes in chromaticity due to changes in wall thickness. The cathode ray tube panel glass of the present invention weighs 50~
75% _{SiO2 ,} 0~5% _Al2O3 , 0~4%CaO, 0~
3% MgO, 0~13% SrO, 0~16% BaO, 0~
3% PbO, 0-3% ZnO, 0-4% _ZrO2 , but the total of SrO, BaO, PbO, ZnO and _ZrO2 is 5-25%, 0-4% _Li2O , 3-15% Na ₂ O, 1
~10% _K2O , but the sum of _Na2O and _K2O is 5
~20%, 0-2% _TiO2 , and _0-3 % _CeO2 base glass containing 0.1-5.0% _Nd2O3 and _0.0005-0.05 % _Cr2O3 by weight. This is a characteristic feature. The panel glass according to the present invention, as described above,
Basic glass and Nd ₂ O ₃ added thereto,
The base glass, which is made of Cr ₂ O ₃ , has the necessary physical and chemical properties for use in color cathode ray tubes. In particular, color cathode ray tubes apply high operating voltages, which generate harmful X-rays and electron beams, so the base glass of such panel glass has a high ability to absorb X-rays and browning due to X-rays and electron beams. It has the property of preventing discoloration that would cause a decrease in the transmittance of the glass. Nd ₂ O ₃ 0.1 to impart selective transmission-absorption properties at visible wavelengths to the base glass having such properties.
_Cr2O3 is added in an _amount of 0.0005 to 0.05% in order to adjust the chromaticity of the glass and to reduce changes in chromaticity due to variations in wall thickness. The constituent components of the panel glass of the present invention will be explained below. First, the compositional component amounts of the basic glass will be explained. SiO ₂ is a major glass-forming oxide that is contained in large amounts, but if it is more than 75%, the solubility and processability will be poor, and if it is less than 50%, the expansion coefficient will be too large and the chemical durability of the glass will deteriorate. It will be inferior in quality. Al ₂ O ₃ has the effect of improving the chemical durability of glass, but if it exceeds 5%, the glass becomes poorly soluble and bubbles break easily. CaO and MgO have the effect of improving the chemical durability of glass, but if they exceed 4% CaO and 3% MgO, the glass tends to devitrify. SrO, BaO, PbO, ZnO, and _ZrO2 are contained in a total amount of 5 to 25% in order to provide the glass with high X-ray absorption ability, but SrO13%,
If BaO16%, ZnO3%, _ZrO2 exceeds 4%,
PbO3
%, the color tends to change to brown when exposed to electron beams. Li ₂ O has the effect of improving the meltability of glass, but if it exceeds 4%, the expansion coefficient becomes too large and the strain point becomes too low. _Na2O , _K2O
is effective for improving the meltability of glass and adjusting the expansion coefficient of glass, but Na ₂ O15
%, K ₂ O 10% and Na ₂ O + K ₂ O 20%, the chemical durability and electrical insulation properties of the glass deteriorate;
If it is less than 3% Na ₂ O, 1% K ₂ O, or 5% Na ₂ O + K ₂ O, the melting properties will deteriorate and devitrification will occur easily, and the strain point of the glass will become too high, resulting in poor workability. TiO ₂ and CeO ₂ are added because they have the effect of preventing browning of the glass due to X-rays or electron beams, but their amounts are 2% or less for TiO _{2 and} 3% or less for CeO 2 . In addition, this basic glass usually contains Sb ₂ O ₃ 0.5% or less, AS ₂ O ₃ 0.5% or less, and F ₂ 0-1% as fining agents.
included. Next, the additive components Nd ₂ O ₃ and Cr ₂ O ₃ contained in the base glass will be explained. Nd ₂ O ₃ is the primary phosphor emitted from red, green, and blue phosphors.
Selectively transmits light of the wavelength shown in the figure,
On the other hand, it is a component that gives glass the ability to absorb light particularly at wavelengths around 580 mμ. like this
Due to the optical properties of the Nd ₂ O ₃ component, images with high brightness and high contrast can be obtained. Furthermore, when viewing television images in the presence of external light, especially under white fluorescent lamps, light in the wavelength range of 570 to 600 mμ, which has the highest intensity in the fluorescent lamp's emission spectrum, is absorbed. The secondary reflection is greatly reduced, and the effect of almost eliminating the virtual image of surrounding objects caused by this reflection is exerted. In order to obtain such effects, Nd ₂ O ₃ needs to be at least 0.1%, but if it exceeds 5.0%, the glass will take on a reddish-purple color, making it difficult to achieve the required neutral gray color as panel glass for color cathode ray tubes. It becomes difficult to obtain a degree. Note that Pr ₆ O ₁₁ as an impurity normally contained in the raw material of Nd ₂ O ₃ may be 25% or less of Nd ₂ O ₃ . Cr ₂ O ₃ improves the chromaticity of the panel glass, which has X-ray absorption properties and is prevented from browning by adding selective light transmission and absorption properties through the addition of Nd ₂ O ₃ . It is the most effective ingredient for adjusting to neutral gray without degrading the color. Also, this
Cr ₂ O ₃ has the effect of reducing changes in chromaticity due to changes in wall thickness of panel glass containing such Nd ₂ O ₃ . In other words, the color of glass containing Nd ₂ O ₃ changes from deep purple when the wall is thick to light reddish purple when the wall is thin, so the wall thickness of the panel glass is different between large and small tubes. Although it is unsuitable for cathode ray tubes because the chromaticity of the image changes significantly, the addition of Cr ₂ O ₃ can be used without impairing the selective transmission-absorption characteristics of the Nd ₂ O _3- containing glass mentioned above. Changes in chromaticity of the image due to variations in the thickness of the panel glass can be significantly controlled. Furthermore, by adding Cr ₂ O ₃ , the transmittance of red and blue light wavelengths can be lowered without substantially changing the transmittance of green light wavelengths. Therefore, the dichroism of the glass containing Nd ₂ O ₃ mentioned above is removed. In addition, since the luminous efficiency of green phosphors is usually lower than that of red and blue phosphors, the current value of the electron gun that makes the green phosphors emit light is increased, so that the green phosphors emit light. The reality is that it increases the brightness of the body, but due to the above effect of adding Cr ₂ O ₃ , red,
The peak current values of the green and blue phosphors can be made substantially equal. The content of Cr ₂ O ₃ to obtain such an effect of Cr ₂ O ₃ is 0.0005 to 0.05 wt%. In addition to Cr ₂ O ₃ , NiO 0.05% or less is additionally added as a subtle chromaticity adjustment and brightness adjustment component.
CoO 0.05% or less and Fe ₂ O ₃ 1% or less may be added. Examples of glasses of the present invention are shown in the following table.

[Table] The raw material powder for each glass shown in the table was weighed to prepare a batch, which was melted in a furnace at 1450°C, and the molten glass was placed in a mold to form a panel. Various tests were conducted on the obtained panels. Some of the test data is shown in the bottom column of the table. Further, the light transmission curve and chromaticity value of the panel glass will be explained with reference to FIGS. 2 to 4. Referring to FIG. 2, solid line a is the transmittance curve of No. 1 glass (thickness 10 mm) in the above table.
The figure also shows Nd ₂ O 3 and Nd 2 O ₃ for comparison.
Instead of Cr ₂ O ₃ , neutral gray glass containing NiO and CoO (thickness 10
mm) is shown by the chain line b. Conventional gray glass exhibits substantial absorption over the entire visible wavelength range, including the red, green, and blue emission spectra. In contrast, the glass according to the present invention has an emission spectrum of about 570 to 600 mμ between the red and green emission spectra.
In other words, it shows particularly large absorption in the wavelength range corresponding to yellow light, and also shows absorption in the wavelength range of 510 to 540 μm.On the other hand, it has high transmittance for light in the wavelength range corresponding to the emission spectrum of each phosphor. It shows. The light transmission curve shown in Figure 2 is based on the above-mentioned British patent
As is clear from the comparison with the light transmission curve in Figure 2 of the specification of No. 1154500, in the glass panel of the present invention containing Cr ₂ O ₃ together with Nd ₂ O ₃ , the glass panel containing only Nd ₂ O ₃ The transmittance in the red and blue wavelength regions is lower than that of glass panels that do not contain Cr ₂ O ₃ . Therefore, according to the present invention, dichroism can be eliminated and the peak current values of the red, green, and blue phosphors can be made the same. Glasses containing Cr ₂ O ₃ along with Nd ₂ O ₃ also exhibit a neutral gray color. This will be explained with reference to FIG. Figure 3 is a chromaticity diagram based on the x and y coordinates of CIE (Commission Internationale de Illumination).
Emission chromaticity of P22, chromaticity of No. 1 glass in the table above, and chromaticity of glass containing 0.5% Nd ₂ O ₃ without Cr ₂ O ₃ for comparison at P22, A and B points, respectively. Indicated. Note that to measure the chromaticity of glass, we use a three-color fluorescent light source P22 (the chromaticity of the emitted light is x : 0.2870, y: 0.3160) is used and displayed as a 11.43 mm thickness conversion value. As is clear from Figure 3, simply add 0.5 Nd ₂ O ₃
%, as shown at point A, the chromaticity of the glass is x: 0.2852, y: 0.3032, which is reddish-purple and cannot be said to have a chromaticity suitable for panel glass for color cathode ray tubes. However, in the No. 1 glass with 0.0063% Cr ₂ O ₃ added to this glass,
The chromaticity moves almost parallel to the y axis and in the direction of increasing y value, as shown at point B, x: 0.2853, y:
It has a neutral gray chromaticity characteristic of 0.3151, which is desirable as panel glass for color cathode ray tubes. FIG. 4 is a chromaticity diagram for explaining changes in chromaticity due to changes in glass thickness, taking the No. 1 glass listed in the table above as an example. The same chromaticity diagram using the P22 light source shows the glass containing 0.5% Nd ₂ O ₃ and the No. 1 glass of the present invention, which is the Nd ₂ O ₃ containing glass containing 0.0063% Cr ₂ O ₃ . , 5mm each,
The chromaticity points measured at wall thicknesses of 10 mm and 15 mm are shown. According to this chromaticity diagram, glass simply containing Nd ₂ O ₃ has a large chromaticity change due to wall thickness variation, but
It can be seen that by adding Cr ₂ O ₃ to this Nd ₂ O ₃ -containing glass, the change in chromaticity due to wall thickness variation becomes significantly smaller. When each glass shown in the table above was observed under sunlight and fluorescent light, each glass showed the following:
No color difference was observed. Rather, they all took on a neutral gray color. That is, it was confirmed that none of the glasses exhibited dichroism. This means that, as mentioned above, by adding Cr ₂ O ₃ to Nd ₂ O 3 -containing glass, the transmittance of red and blue wavelengths decreases, while the transmittance of green _light hardly changes. ,
This is also easily understood from the fact that the chromaticity of glass is almost equal to the chromaticity of P22 white light. As explained above, the panel glass according to the present invention not only has X-ray absorption properties and browning prevention properties, but also has excellent optical properties in terms of light transmission performance and chromaticity. Color cathode ray tubes provide images with high contrast and high brightness, and also have the effect of preventing secondary reflection of external light so that the images can be viewed clearly. Further, since the glass of the present invention has little change in chromaticity due to variations in wall thickness, it is possible to reduce changes in chromaticity in images of color cathode ray tubes due to differences in wall thickness of panel glass. Furthermore, since it does not exhibit dichroism, images with the same color tone can be obtained under sunlight or fluorescent light. The panel glass of the present invention is suitable not only for color cathode ray tubes for general household use, but also for cathode ray tubes for display devices and display devices.

[Brief explanation of the drawing]

Figure 1 shows the emission spectrum of the phosphor;
The figure shows the transmittance curves of the panel glass according to the present invention and the conventional gray glass, FIG. 3 is a chromaticity diagram explaining the process of chromaticity adjustment in the panel glass of the present invention, and FIG. Simply with No.1 glass
FIG. 2 is a chromaticity diagram showing chromaticity changes with respect to wall thickness variations for Nd ₂ O ₃ -containing glass.

Claims (1)

[Claims] 1 50-75% SiO ₂ , 0-5% Al ₂ O ₃ , 0-75% by weight
4% CaO, 0-3% MgO, 0-13% SrO, 0-
16% BaO, 0~3% PbO, 0~3% ZnO, 0~
4% _ZrO2 , but the total of SrO, BaO, PbO, ZnO and _ZrO2 is 5-25%, 0-4% _Li2O , 3
~15% _Na2O , 1-10% _K2O , but for a base glass where the sum of _Na2O and _K2O is 5-20%, 0-2% _TiO2 , and 0-3% _CeO2 By weight,
A panel glass for a color cathode ray tube, characterized in that it contains 0.1 to _5.0 % _Nd2O3 and 0.0005 to _0.05 % _Cr2O3 .