JPH0696685A - Shadow mask - Google Patents

Abstract

PURPOSE:To provide a shadow mask capable of restraining the occurrence of a color shear without impairing the advantage of a Fe-Ni alloy such as low temperature expansion and moldability. CONSTITUTION:A shadow mask is made of a Fe-Ni alloy material containing nickel at least within the range of 30 to 45wt.%. The alloy material has a surface layer containing Fe4N and/or Fe3NiN. Furthermore, only the surface layer of the alloy material is increased as Hv=170 or above. For example, when the surface layer hardness of the alloy material is H1 and the inside hardness is H2, a ratio of H1 to H2 is taken at 1.05 or above. According to this construction, a howling resistance characteristic can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shadow mask used for a color cathode ray tube (hereinafter referred to as C-CRT).

[0002]

2. Description of the Related Art Generally, in a C-CRT, an electron beam emitted from an electron gun is selectively passed through a shadow mask having a large number of pores formed on the inner surface of a glass envelope. A color image is reproduced by colliding an electron beam with a predetermined position on the phosphor layer. At this time, not all of the emitted electron beams pass through the aperture, and the electron beam that passes through the aperture is about
Less than 1/3, the rest of the electron beam hits the shadow mask directly and heats it. As a result, when the shadow mask thermally expands, the positions of the openings deviate from the design standard and are displaced, resulting in a color misregistration phenomenon on the phosphor screen.

For these reasons, Fe-Ni alloys having a low thermal expansion characteristic, for example, 36 wt% have recently been used in place of conventional steel materials such as low carbon rimmed cold rolled steel and low carbon aluminized cold rolled steel. Ni-Fe alloys (Amber alloys) are becoming popular as shadow mask materials.

[0004]

However, the Fe-Ni alloys described above have the advantage that the coefficient of thermal expansion is extremely small, but on the other hand, they have the drawback that the hardness is low. For example, the hardness of the amber alloy becomes about Hv 120 to Hv 140 when it is softened by annealing, and the vibration of the outside, for example, the vibration of the speaker causes resonance of the shadow mask. As described above, when the shadow mask vibrates, the electron beam passage hole formed in the shadow mask and the phosphor layer are displaced from each other, which causes color shift. In particular, in recent C-CRTs, the diameter and forming pitch of the electron beam passage holes tend to be reduced in order to satisfy high definition and high quality, so that the degree of color misregistration becomes more severe. .

On the other hand, the characteristics required for C-CRTs, especially industrial C-CRTs for displays, etc., are increasing year by year, and further higher definition and higher quality of images are required. With the improvement of the required characteristics for the C-CRT, naturally, the required characteristics for the shadow mask have become more severe. For example, suppressing howling of a shadow mask to prevent color misregistration is an important requirement for achieving high definition of an image.

The present invention has been made to address such a problem, and improves the hardness of the Fe-Ni-based alloy without impairing the advantage of low thermal expansion and the formability, and suppresses the occurrence of color misregistration. The purpose is to provide a shadow mask that makes it possible.

[0007]

The shadow mask of the present invention comprises Fe containing at least Ni in the range of 30% by weight to 45% by weight.
-In a shadow mask made of a Ni-based alloy material, the Fe
The -Ni-based alloy material is characterized by having a surface layer containing Fe ₄ N and / or Fe ₃ Ni N. Further, the present invention is
The Fe-Ni alloy material is characterized in that the hardness of its surface layer is Hv 170 or more.

That is, the shadow mask of the present invention is F
The howling resistance is improved by forming a nitride layer on the surface of the e-Ni alloy material in the process of manufacturing the shadow mask and increasing only the hardness of the surface layer.

Here, the amount of nitrogen is increased from the beginning of casting,
When nitride is introduced into the entire Fe-Ni alloy material and the hardness is increased overall, the howling resistance can be improved, but the formability is greatly reduced and the shape accuracy as a shadow mask is reduced. Will be invited. Therefore, in the present invention, by including Fe ₄ N and / or Fe ₃ Ni N in the surface layer and further increasing the hardness of only the surface layer to Hv 170 or more, both howling resistance and moldability are improved. Makes it possible to satisfy. Furthermore, increasing the hardness of only the surface layer can be expected to further improve the howling resistance as compared with the case of increasing the hardness as a whole. Here, the thickness of the surface layer containing Fe ₄ N and / or Fe ₃ Ni N is preferably 0.5 μm or more. The hardness of the surface layer means a value measured at a position of about 1 to 20 μm from the surface.

The hardness difference between the surface layer and the inside is
When the surface layer hardness of the Fe—Ni alloy material is H ₁ and the internal hardness is H ₂ , the ratio H ₁ / H ₂ of these is preferably 1.05 or more.

The shadow mask of the present invention contains 30% by weight of Ni.
Fe-based alloy (Fe-Ni alloy) contained in the range of ~ 45 wt%, when the Ni content is out of the above range,
Any of these causes an increase in the coefficient of thermal expansion, resulting in a decrease in performance as a shadow mask. Further, as the additive element other than Ni, various elements can be used depending on the characteristics to be obtained. For example, Mn and Si may be added to improve deoxidation and hot workability. Not only Fe-Ni alloys, but also Fe-Ni-Cr alloys, Fe-Ni-Co alloys, Fe-Ni alloys
It is also possible to use a -Cr-Co alloy or the like. further,
V, Cr, Nb, Ta, W, Mo, Ti as easy nitriding elements
It is also possible to contain at least one element selected from Al and Al in the range of 0.01% by weight to 0.5% by weight.
Thereby, the surface hardness can be increased more easily. The above-mentioned nitriding-prone element is added in an amount of 0.01
If it is less than wt%, the effect of improving the nitriding property cannot be sufficiently obtained.
Adding more than 0.5% by weight not only brings no further effect, but also causes an increase in the coefficient of thermal expansion.

The shadow mask of the present invention is manufactured, for example, as follows. That is, first, a Fe-Ni alloy component adjusted to a predetermined alloy composition is melted and cast, and this cast material is hot rolled to an intermediate plate thickness. Next, cold rolling and annealing are repeatedly performed on this hot rolled material until a desired plate thickness is obtained. After this, through holes are formed in a matrix shape by etching or the like in the cold plate material having a desired plate thickness, and after annealing as necessary, the plate material with the through holes is formed into a desired shadow. A desired shadow mask can be obtained by warm forming into a mask shape. At this time, the formation of the surface nitrided layer, that is, the increase of the surface hardness is achieved by performing the annealing after the cold rolling and the annealing after the etching in the nitrogen atmosphere or the ammonia decomposition gas atmosphere. The conditions at this time are set as appropriate according to the alloy composition used.

As described above, by performing annealing in a nitrogen atmosphere or an ammonia atmosphere, nitrogen is introduced only into the surface layer to deposit a nitride and the hardness of only the surface layer increases. The above nitriding conditions are Fe ₄ N and / or Fe ₃ Ni N
There is no limitation as long as is formed on the surface of the Fe-Ni alloy material. However, if nitriding proceeds too much, Fe ₃ N and Fe ₂ Ni N may be generated on the surface, and the surface layer may peel off.
Fe ₄ N and / or Fe ₃ Ni N are preferred.
The amount of introduced nitrogen is preferably in the range of 30 ppm to 300 ppm as the average nitrogen content. If the average nitrogen content is less than 30 ppm, the hardness of the surface layer cannot be sufficiently increased. Further, if it exceeds 300 ppm, the hardness is increased as a whole.

[0014]

In the shadow mask of the present invention, the hardness of only the surface layer is reduced to Hv by forming the nitride layer on the surface portion.
It is higher than 170. This makes it possible to improve howling resistance without lowering moldability. Further, by increasing the hardness of only the surface layer, the howling resistance can be improved more than the hardness is increased as a whole. Furthermore, the property of the Fe-Ni alloy, which has a low thermal expansion, is maintained as it is.

[0015]

EXAMPLES Next, examples of the present invention will be described.

Examples 1 to 10 Fe-Ni alloy components each having the composition shown in Table 1 were melted and cast to obtain cast materials of 200 mm x 800 mm x L, respectively. Next, each of these cast materials was passed through hot rolls and hot-rolled at a temperature of 1100 ° C. so that the plate thickness became 3 mm.

Next, for each hot rolled material obtained,
By repeatedly performing cold rolling by a cold roll and annealing twice, a plate material having a thickness of 0.25 mm was obtained.
Here, the annealing process after cold rolling is performed in a nitrogen atmosphere.
It was carried out under the conditions of 00 ° C x 5 to 20 minutes.

Next, a predetermined matrix of electron beam transmitting holes is formed on each of the above-mentioned plate materials by photoetching, and then 900 ° C. in a dry hydrogen atmosphere.
Annealing was performed under the condition of ℃ × 10 to 30 minutes. After that, press molding was performed so as to have a predetermined mask shape, and shadow masks were obtained.

The average nitrogen concentration, the hardness at a position of 1 to 20 μm from the surface and the hardness at the center of the plate thickness of each shadow mask thus obtained were measured. The howling resistance was evaluated according to the following procedure. That is, by actually incorporating each shadow mask into the C-CRT,
The degree of color misregistration was measured by applying vibration of 100 Hz to 300 Hz. The results are shown together in Table 1.

Comparative Example 1 in the table is a shadow mask manufactured under the same conditions as those of the above Examples except that the annealing process after cold rolling is performed in dry hydrogen, and Comparative Example 2 is used during casting. Nitrogen was introduced to deposit nitrides entirely.

[0021]

[Table 1] As is clear from Table 1, each of the shadow masks according to each example has only improved surface hardness, which reduces resonance due to external vibration and suppresses the occurrence of color misregistration. .

Examples 11 to 20 Using Fe-Ni based alloy components having the same compositions as those of Examples 1 to 10 described above, and in the same manner as in Examples 1 to 10, the plate thickness was set to 0.
I got a 25mm plate.

Next, a predetermined matrix of electron beam transmitting holes is formed in each of the above plate materials by photoetching, and then at 850 ° C. in a dry hydrogen atmosphere.
Was annealed. After that, press molding was performed so as to have a predetermined mask shape, and shadow masks were obtained.
Then, the shadow mask was subjected to a nitriding treatment for 30 minutes and 24 hours in an ammonia atmosphere at 580 ° C., and subsequently subjected to a blackening treatment in water vapor.

The shadow mask thus obtained is nitrided up to 1 μm and 20 μm from the surface, and the crystals constituting the surface layer are Fe ₄ N and / or Fe ₃ Ni.
It was N.

The average nitrogen concentration of these shadow masks, the hardness of the surface layer, and the hardness at the plate thickness center were measured. In addition, the anti-howling characteristics were evaluated in the above-mentioned Examples 1 to 1.
In the same manner as in No. 10, the color shift was measured. At that time, neither so-called howling occurred.

[0026]

[Table 2] As can be seen from Table 2, the shadow masses in each of the examples have only the surface hardness improved, which suppresses resonance due to external vibration and suppresses the occurrence of the color shift phenomenon. .

[0027]

As described above, according to the present invention, F
Since the hardness of only the surface layer of the e-Ni alloy plate material is increased, it is possible to provide a shadow mask excellent in howling resistance without impairing moldability.

[0028]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Mitsuharu Hagiwara Mitsuharu Hagiwara 2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Stock company, Toshiba Keihin Office (72) Inventor Yasuhisa Otake 1-2-9 Harara-cho, Fukaya-shi, Saitama Stock Company Toshiba Fukaya Electronics Factory

Claims (6)

[Claims] 1. A shadow mask comprising a Fe-Ni alloy material containing at least Ni in the range of 30 wt% to 45 wt%, wherein the Fe-Ni alloy material is Fe ₄ N and / or Fe ₃ Ni N.
A shadow mask having a surface layer containing: 2. The shadow mask according to claim 1, wherein the surface layer containing Fe ₄ N and / or Fe ₃ Ni N has a thickness of 0.5 μm or more. 3. A shadow mask made of a Fe—Ni alloy material containing at least Ni in the range of 30 wt% to 45 wt%, wherein the Fe—Ni alloy material has a surface layer hardness of Hv 170 or more. A shadow mask that is characterized by being. 4. The shadow mask according to claim 3, wherein when the surface layer hardness of the Fe—Ni alloy material is H ₁ and the internal hardness is H ₂ , the ratio H ₁ / H _{2 of} these is 1.05. A shadow mask characterized by the above. 5. A shadow mask made of a Fe—Ni alloy material containing at least Ni in the range of 30 wt% to 45 wt%, wherein the Fe—Ni alloy material has an average nitrogen content of 30 ppm to 300 p.
A shadow mask characterized by being in the pm range. 6. The shadow mask according to claim 5, wherein the Fe—Ni alloy material contains 0.01 weight% of at least one element selected from V, Cr, Nb, Ta, W, Mo, Ti and Al. %
A shadow mask characterized by being contained in an amount of up to 0.5% by weight.