KR100269364B1 - Bird Cage Mask of Color CRT - Google Patents

Abstract

PURPOSE: A shadow mask of a color Braun tube is provided to improve the color purity by reducing a doming phenomenon of a shadow mask. CONSTITUTION: A shadow mask member(20) has a plurality of opening portion(21). The shadow mask(20) is formed with an AK(Aluminium Killed) steal of a low price. A shape Memory Effect layer(22) is formed at one side of the shadow mask member(20) for forming a fluorescent layer. A plurality of black layer(23,24) is formed at both sides of the shadow mask member(20) and the shape Memory Effect layer(22). The Shape Memory Effect layer(22) is formed with an alloy of a nickel and a titanium or an alloy of a copper and an aluminium with transformation temperature.

Description

Bird Cage Mask of Color CRT

The present invention relates to a shadow mask of a color CRT tube coated with a special material, and particularly, when a doming phenomenon in which the shadow mask swells due to a temperature rise occurs, the dominant phenomenon is suppressed due to shrinkage of the coaming membrane, thereby distributing the color distribution of the CRT. It relates to a bird's eye mask of color CRT.

Conventional shadow mask type color CRT tube is, as shown in Figure 1, a panel 10, a fluorescent screen 14 is formed, a shadow mask 11 made of a thin metal sheet having a large number of openings, And a rectangular frame 12 for welding and supporting the shadow mask 11 and an elastically deformed spring 13 for connecting and fixing the frame 12 to the panel 10. The spring 13 is configured to be pinched by panel pins mounted on the panel 10 so that the shadow mask 11 is supported by the panel 10. When power is supplied to the shadow mask type color CRT configured as described above, a plurality of electron beams are emitted from an electron gun assembly embedded in a neck (not shown), and these electron beams are focused into an opening in the shadow mask 11, and the panel The formed fluorescent screen 14 is reached. At this time, about 80% of the electrons of the plurality of electron beams emitted from the electron gun do not pass through the openings and impinge on the shadow mask to be converted into heat, and the shadow mask 11 is heated by the heat. Due to this heating, the heat around the shadow mask 11 in contact with the frame 12 is conducted through the frame 12 or the like, so that the temperature of the peripheral portion is lower than the temperature of the center portion of the shadow mask 11. . As a result, the temperature mask between the center portion and the peripheral portion of the shadow mask is generated by the so-called doming phenomenon in which the center portion swells in a dome shape as shown in FIG. 2. When such a doming phenomenon occurs, the distance between the shadow mask 11 and the fluorescent screen 14 is changed, so that accurate landing of the electron beam is difficult, so-called mis-landing occurs, resulting in poor color distribution. Mis-landing due to the dominant phenomenon occurs remarkably early in the CRT operation.

To date, various methods have been proposed to reduce the dominant phenomenon. Most of them have attempted to reduce the thermal expansion of shadow masks or to increase the thermal emissivity of shadow masks using special materials.

As a method of reducing thermal expansion of a shadow mask, an invar material having a very low thermal expansion rate is used. The invar material can significantly reduce mis-landing and is mainly used for a CRT which requires high color purity. However, the Inba material containing 36% of nickel is difficult to manufacture, and has the disadvantage of being expensive.

On the other hand, the method of increasing the thermal emissivity of the shadow mask is disclosed in US Patent No. 2826538, Domestic Patent No. 92-5980, US Patent No. 4612061 and the like.

U.S. Patent No. 2826538 discloses that the shadow mask has a black layer made of graphite, so that the thermal radiation coefficient is added by 0.4-0.5 to reduce the temperature of the shadow mask. This method of letting is adopted in most CRTs at present.

In addition, Korean Patent No. 92-5980 discloses that a porous black layer is formed on the surface of a shadow mask so that the thermal reflectivity is improved due to the black pigment of the porous layer so as to suppress the doming phenomenon.

In US Patent No. 4612061, an electron beam reflection coating film using Bi ₂ O ₃ , commonly referred to as bismuth coating, is formed on the electron gun side of the shadow mask, so that its reflectivity is about 0.24-0.28, which is added to the shadow mask from the electron beam. It is disclosed that energy can be reduced by about a quarter.

Most of the CRTs currently produced use blackened masks for the purpose of reducing the temperature, and the heat generation coefficient increases by 0.4-0.5 due to the blackening treatment. In the manufacturing process of the CRT, the adhesion of the black layer is lowered due to the temperature change during the heat treatment process, so that the small pieces fall off due to some peeling due to the external vibration of the CRT, and the openings of the shadow mask are blocked by the small pieces. The picture quality on the fluorescent screen is deteriorated, and furthermore, the small pieces cause a spark between the electrodes of the electron gun, thereby degrading the breakdown voltage characteristic.

On the other hand, in the case where the porous layer is employed without using the blackening treatment, the above-mentioned disadvantages of the blackening treatment are eliminated, and the thermal radiation effect of the shadow mask is not significantly different from that of the blackening treatment, but from the viewpoint of thermal energy, the blackening treatment or the porous The use of layers has a rather detrimental effect on the thermal energy imposed on the shadow mask. That is, the reflectance decreases because the thermal emissivity is increased, which causes the shadow mask to absorb much of the collision energy of the electron beam, so that the temperature of the shadow mask does not drop significantly.

In addition, when using bismuth coating, the heat energy applied to the shadow mask itself is reduced by about a quarter, but also has a problem that the doming phenomenon cannot be greatly reduced because it has radiant heat of about 3/4.

Therefore, the present invention was invented in view of the above-described problems of the prior art, and the dome phenomenon of the shadow mask is significantly reduced by absorbing thermal expansion of the shadow mask by coating a shape memory alloy contracting at a constant temperature on the shadow mask. It is to provide a bird mask to improve the color purity of the CRT.

1 is a diagram schematically showing one end surface of a conventional color CRT,

2 is a diagram illustrating mis-landing due to shadow mask ming phenomenon;

3 is a view schematically showing a cross-sectional mask mask according to an embodiment of the present invention,

4 is a graph showing the temperature characteristics of the shape memory alloy.

Explanation of symbols for main parts of the drawings

10: panel 11, 20: new mask

12: frame 13: spring

14 phosphor 21 opening

22: shape memory alloy layer 23, 24: black layer

The shadow mask of the color CRT tube of the present invention for achieving the above object is a shape memory alloy which is formed on the side where the shadow mask member having a plurality of openings and the fluorescent film of the shadow mask member is formed and contracted at a predetermined temperature or more. It is characterized by having a layer.

Preferably, black layers are formed on both sides of the shadow mask layer and the shape memory alloy layer.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

3 is a schematic enlarged view of a portion of a shadow mask of the present invention, including a shadow mask member 20 having a plurality of openings 21 and formed of AK steel, and the shadow mask member 20. ) Is formed of a shape memory alloy layer 22 coated on one side where a fluorescent film is formed, and black layers 23 and 24 formed on both sides of the shadow mask member 20 and the shape memory alloy layer 22, respectively. It is.

The shadow mask member uses inexpensive AK (Aluminum Killed) steel and the shape memory alloy is transformed from the martensite to the austenoid phase and contracted at 70-80 ° C., which is the operating temperature of the CRT. For example, NiTinol or a copper aluminum alloy which is a nickel titanium alloy is used.

In addition, the black layers 23 and 24 are made of graphite, which is to increase the emissivity due to the electron beam that strikes the shadow mask as in the prior art. The bismuth coating layer reflects the electron beam instead of the black layer. May be used.

According to the shadow mask of the present invention configuration as described above, it is possible to absorb almost no thermal expansion coefficient of the shadow mask by using the thermal contraction rate of the shape memory alloy.

That is, the thermal expansion coefficient of the mixture in which the AK steel, which is a constituent material of the shadow mask member, and the shape memory alloy are mixed is expressed by Equation 1 below.

Where α _eg is the thermal expansion coefficient of the shadow mask, α ₁ and α ₂ are the thermal expansion coefficients of AK steel and shape memory alloy, f ₁ and f ₂ are the volume ratios of AK steel and shape memory alloy, respectively, E ₁ and E ₂ are AK Modulus of elasticity of steel and shape memory alloy.

In Equation 1, the elastic modulus of the AK steel and the shape memory alloy is almost the same, and the coefficient of thermal expansion (α ₂ ) of the shape memory alloy has a negative value at the transition temperature of 70-80 ° C. (which is the shape memory alloy at the transition temperature). When the volume ratio (f ₂ ) and the coefficient of thermal expansion (α ₂ ) of the shape memory alloy are properly adjusted according to the volume ratio (f ₁ ) and the coefficient of thermal expansion (α ₁ ) of the AK steel, f ₁ E ₁ α ₁ + f ₂ E ₂ α ₂ = 0 Thus, the thermal expansion coefficient α _eg of the shadow mask can be made zero.

That is, since the volume ratio of the shape memory alloy is about 1 / 10-1 / 50 compared to that of AK steel, if the thermal contraction rate of the shape memory alloy is 10-50 times larger than that of AK steel, f ₁ E ₁ α ₁ + f ₂ E ₂ α ₂ = 0 Thus, the thermal expansion coefficient α _eg of the shadow mask can be made zero. However, shape memory alloys having such properties are very difficult to manufacture, so when using a shape memory alloy formed of nitinol or copper aluminum alloy, the volume of the shape memory alloy is 1/10 of AK steel. In addition, the thermal contraction rate of the shape memory alloy can be 8 times larger than the thermal expansion rate of AK steel, and the thermal expansion coefficient (α _eg ) of the shadow mask is about 1/10 of that of AK steel. It will have the same coefficient of thermal expansion.

By the contraction and expansion of the shape memory alloy layer as shown in Figure 4 the temperature rise of the shadow mask member formed of AK steel due to the shrinkage of the shape memory alloy layer at t ₀ of the operating temperature 70-80 ℃ of the CRT It is possible to substantially eliminate the expansion rate of the entire shadow mask by absorbing the expansion of the expansion, and when the operation of the CRT stops, the temperature of the shape memory alloy layer is expanded at a temperature t ₁ lower than the temperature t _{0 at} which the shrinkage occurs. Restore to state

And since the structure of the shadow mask is formed to be convex toward the side of the fluorescent layer, the shape memory alloy layer should be coated on the phosphor side of the shadow mask member so as to suppress adverse effects due to stress caused by shrinkage and expansion of the shape memory alloy layer. do.

As described above, according to the shadow mask of the color CRT tube of the present invention, a shape memory alloy having a characteristic of shrinking at the CRT operating temperature is coated on the phosphor side of the shadow mask, thereby inexpensive AK steel due to heat generated during operation of the CRT. Absorbs the expanded portion of the shadow mask formed by the shrinkage of the shape memory alloy coating layer, thereby suppressing thermal expansion of the entire shadow mask to be almost zero, thereby preventing the doming phenomenon, thereby greatly improving the color purity of the CRT and inexpensive. Since AK steel can be used as a shadow mask member, the manufacturing cost can be greatly reduced.

Claims (5)

A bird mask member having a plurality of openings, A shadow mask of a color CRT tube, characterized by having a shape memory alloy layer coated on the phosphor side of the shadow mask member and shrinking at an operating temperature. The method of claim 1, A shadow mask of a color CRT tube, characterized in that a black layer formed of graphite is formed on both sides of the shadow mask member and the shape memory alloy layer. The method of claim 1, A shadow mask of a color CRT, characterized in that a bismuth coating layer, which is a reflection layer of a transfer beam, is formed toward an incident side of the shadow mask member. The method of claim 1, The shadow mask member is AK steel and the shape memory alloy is a nickel titanium alloy or copper aluminum alloy which causes a shrinkage action at 70-80 ° C., the operating temperature of the color cathode ray tube. The method of claim 4, wherein And the volume of the shape memory alloy is 1/10 of the volume of the AK steel, and the thermal shrinkage of the shape memory alloy is 8 times larger than the thermal expansion rate of the AK steel.

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