JP2002184323A - Shadow mask preventing deterioration of color purity of screen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shadow mask that is constructed so that the electron beams reflected at the side face of the hole part constituting the electron beam passing holes may not bring about deterioration of color purity of the screen. SOLUTION: The shadow mask 1 comprises ridgeline 8, 8b, 8e that are formed by the side face of an electron gun side hole par and the side face of a fluorescent face side hole part crossing each other in the electron beam passing holes, which are formed by etching process of a metal plate material and made of the electron gun side hole 4a, 4b where electron beams enter and the fluorescent face side hole 3a, 3b from where electron beams emit. The electron beam passing hole is formed so that the electron beams, which are irradiated in a prescribed angle to the shadow mask surface formed with the electron gun side hole 4b, and of which a part are reflected at the side face 10e of the electron gun side hole 4b, may be obstructed by the side face 6b of the fluorescent face side hole 3b or returned to the electron gun side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shadow mask for a color cathode-ray tube, which prevents a decrease in color purity of a screen. The present invention relates to a shadow mask configured so that an electron beam reflected on a side surface of a hole constituting a hole does not cause a decrease in color purity of a screen.

[0002]

2. Description of the Related Art A shadow mask generally used as a color selection component for a CRT has an electron beam passing hole including an electron gun-side hole through which an electron beam enters and a phosphor screen side hole through which the electron beam exits. Are formed in large numbers. The shadow mask guides the electron beam to a predetermined position on the phosphor screen, and
It plays a role of emitting any single color of GB.

In such a shadow mask, the sizes and pitches of the holes on the electron gun side and the holes on the phosphor screen constituting the electron beam passage holes differ depending on the specifications of various CRTs. In particular, a CRT (hereinafter, referred to as CDT) used for a computer display is required to have higher definition than a CRT for consumer TV (hereinafter, referred to as CPT), and is represented by color purity and the like. There is also a demand for high quality image quality. Therefore, the shadow mask for CDT is required to be further miniaturized in the size and pitch of the electron beam passage holes, and high quality can be maintained in image quality characteristics represented by color purity of a screen. Structural correspondence is required.

[0004]

However, in the conventional shadow mask, if the shape of the electron beam passage hole formed therein is irregular or inappropriate,
The electron beam reflected by the side surface of the electron beam passage hole, specifically, the side surface at the hole on the electron gun side, etc., may irradiate the fluorescent screen at a position other than the position where the electron beam should be irradiated.

[0005] This causes a reduction in the color purity of the position to be illuminated and also causes a variation in the color purity of the illuminated phosphor screen with the reflected electron beam, resulting in a reduction in the purity of the entire screen. There was a risk of doing so.

In particular, as described above, since the shadow mask is required to further reduce the size and pitch of the electron beam passing holes, a solution has been desired.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and is configured so that an electron beam reflected on a side surface of a hole constituting an electron beam passage hole does not cause a decrease in color purity of a screen. A shadow mask is provided.

[0008]

According to a first aspect of the present invention, a metal plate material is formed by etching, and a hole on an electron gun side on which an electron beam is incident and a hole on a phosphor screen side on which the electron beam exits. In a shadow mask having an ridge formed by intersecting the side surface of the hole on the electron gun side and the side surface of the hole on the phosphor screen side, the electron beam passing hole consisting of The electron beam radiated at a predetermined angle β to the surface of the shadow mask in which the holes are formed and partially reflected by the side surfaces of the holes on the electron gun side are irradiated with the holes on the phosphor screen side. The electron beam passage hole is formed so as to be obstructed by the side surface of the substrate or return to the electron gun side.

According to the present invention, the electron beam passage hole is irradiated at a predetermined angle β to the surface of the shadow mask on which the hole portion on the electron gun side is formed, and the electron beam passage hole is formed on the side surface of the hole portion on the electron gun side. Since the partially reflected electron beam is formed so as to be hindered by the side surface of the hole on the phosphor screen side or to return to the electron gun side, electrons related to a single reflection involved in lowering the color purity of the screen. Lines can be prevented from reaching the phosphor screen. As a result, it is possible to prevent a decrease in the color purity of the screen of the color CRT.

According to a second aspect of the present invention, in the shadow mask according to the first aspect, a height from a surface of the shadow mask, in which the hole on the electron gun side is formed, to the ridge, is:
It is characterized in that the thickness is not more than 1/10 of the thickness of the metal plate.

According to this invention, the height from the surface of the shadow mask where the hole on the electron gun side is formed to the ridge line is set to 1/10 or less of the thickness of the metal plate material. Among the electron beams reflected on the side surface of the hole, it is possible to prevent the electron beam related to the single reflection related to the reduction of the color purity of the screen from reaching the phosphor screen. As a result, it is possible to prevent a decrease in the color purity of the screen of the color CRT.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an example of a sectional form of electron beam passage holes 2a and 2b formed in a shadow mask 1 of the present invention. 1A shows the form of an electron beam passage hole 2a formed in the center of the shadow mask 1, and FIG. 1B shows the form of the electron beam passage hole 2b formed in the periphery of the shadow mask 1. It is a form. FIG. 2 is a mounting view of a stretchable shadow mask 21 having a slit type electron beam passage hole 22, and the electron beam through hole 22 has a cross-sectional shape shown in FIG. In FIG. 2, the stretchable shadow mask 21 stretches a shadow mask grid from above and below with a steel frame 23 (also referred to as a stretch).
It is manufactured and mounted in a cathode ray tube. In the CRT 24 thus configured, an electron beam 26 emitted from an electron gun 25 passes through an electron beam passage hole 22 formed in a stretchable shadow mask and is irradiated on a fluorescent screen 27.

As shown in FIG. 1, the shadow mask 1 of the present invention has holes 4a, 4b on the electron gun side where an electron beam is incident.
And electron beam passing holes 2a and 2b formed by holes 3a and 3b on the phosphor screen side from which electron beams are emitted, are formed by etching a metal plate material. In the shadow mask 1, holes 4a, 4a on the electron gun side are provided.
An electron beam (shown by hatching in each drawing) irradiated at a predetermined angle β (see FIG. 3) with respect to the surface of the shadow mask on which the b is formed passes through a hole on the electron gun side. A part thereof is reflected by the side surface 10e of the portion 4b. The electron beam passage hole 2b is formed so that the reflected electron beam is blocked by the side surface 6b of the hole 3b on the fluorescent screen side or returns to the electron beam side.

As the type of shadow mask, a slit type shown in FIG. 2 is particularly preferable, but a slot type (not shown) having a substantially rectangular electron beam passing hole also has a circular electron beam passing hole. It may be of a dot type and is not particularly limited. Therefore, regardless of the type of the shadow mask based on the shape of the electron beam passage hole, the technical idea of the present invention is applied to a shadow mask in which the color purity of the screen is reduced by the electron beam reflected by the electron beam passage hole. It can be applied preferably. The slit type shadow mask is generally called an aperture grill.

Next, the form of the electron beam passage hole will be described in detail.

As shown in FIG. 1, the electron beam passage holes 2a and 2b are formed with holes 4a and 4b on the electron gun side where the electron beam enters.
The holes 3a and 3b on the fluorescent screen side from which the electron beam is emitted are formed. The opening width S or the opening area of the holes 3a and 3b on the phosphor screen side is usually larger than the opening width P or the opening area of the holes 4a and 4b on the electron gun side so that an electron beam can be easily emitted. You.

The holes 4a and 4b on the electron gun side and the holes 3a and 3b on the phosphor screen side, which form the electron beam passage holes 2a and 2b,
The position formed differs depending on the coordinate position on the shadow mask. Specifically, in the central portion of the shadow mask, the electron beam is irradiated almost straight toward the electron beam passage hole 2a, so that the hole 4a on the electron gun side and the hole 3a on the phosphor screen side are: The respective center positions are almost the same. On the other hand, in the peripheral portion of the shadow mask, the electron beam is irradiated obliquely toward the electron beam passage hole 2b, so that the hole 3b on the phosphor screen side is more peripheral than the hole 4b on the electron gun side. It is formed so as to shift in the direction. At this time, as the formation position of the electron beam passage hole goes from the center to the periphery, the hole 3b on the phosphor screen side is gradually shifted toward the outer periphery of the shadow mask as compared with the hole 4b on the electron gun side. It is formed as follows.

As shown in FIG. 1, the electron beam passage holes 2a and 2b have side surfaces 1a of the hole portions 4a and 4b on the electron gun side.
Ridges 8, 8 formed by intersecting 0, 10b, 10e with side faces 6, 6b, 6e of holes 3a, 3b on the phosphor screen side.
b, 8e. The ridges 8, 8b, 8e are:
FIG. 3 shows an intersection of a hole on the electron gun side and a hole on the phosphor screen side.

According to the present invention, an electron beam is irradiated at a predetermined angle β to the surface of a shadow mask in which a hole on the electron gun side is formed, and a part of the electron beam is reflected on a side surface of the hole on the electron gun side. Is a shadow mask in which an electron beam passage hole is formed so as to be obstructed by the side surface of the hole on the phosphor screen side or return to the electron gun side, at this time, the side surface of the hole portion on the electron gun side is It is preferable that the angle is formed at a predetermined angle α with respect to the shadow mask surface on the electron gun side.

The shadow mask having such a configuration is as follows.
In particular, in the peripheral portion of the shadow mask, among the electron beams reflected on the side surface 10e of the hole portion 2b on the electron gun side, the electron beam related to the single reflection related to the reduction of the color purity of the screen is converted into the hole on the phosphor screen. It can be blocked by the side surface 6b of the portion 3b or returned to the electron gun side.

FIG. 3 shows the angle β at which the electron beam is incident on the surface of the shadow mask having the hole on the electron gun side.
The angle α taken by the side surface of the hole on the electron gun side with respect to the shadow mask surface; the coordinate width W in the X direction from the ridge line (intersection position) to the side surface end of the hole on the phosphor screen side; FIG. 9 shows a relationship between the height H (= t−h) from a portion (intersection position) to the surface of the shadow mask where the hole on the phosphor screen side is formed.

In this case, in order for the electron beam reflected on the side surface 10e of the hole 2b on the electron gun side to be blocked by the side surface of the hole on the phosphor screen side, the reflected electron beam must move along the horizontal axis in FIG. On the other hand, the angle must be equal to or less than the angle θ.
The angle θ varies depending on the coordinate width W and the height H in the X direction, but mainly the angle β at which the electron beam is incident.
And the angle α of the side surface of the hole on the electron gun side. When the side surface of the hole on the electron gun side is not a uniform flat surface, the angle α is represented by an approximate angle considering the overall shape of the side surface.

For example, even if a part of the electron beam incident on the electron beam passage hole at the incident angle β is reflected on the side surface of the hole on the electron gun side, its path is obstructed by the side surface of the hole on the fluorescent screen side. The angle α of the side surface of the hole on the electron gun side can be defined in a preferable range so as to return to the electron gun side.

At the periphery of the shadow mask, the incident angle β of the electron beam becomes acute, so that the angle α on the side surface of the hole on the electron gun side also becomes acute. However, strictly controlling the angle α of the side surface of the hole on the electron gun side has some difficulties in manufacturing. Therefore, in the peripheral portion of the shadow mask, the angle α of the side surface of the hole side on the electron gun side is not so sharp. In addition to reducing the height h to the ridge line,
It is preferable to reduce the coordinate width W in the X direction. By doing so, the reflection of the electron beam itself can be reduced, and the path of some of the reflected electron beam can be hindered by the side surface of the hole on the phosphor screen side. The overall balance can also be favorable.

In setting such a relationship and a preferable range, the angle β of incidence of the electron beam, the angle α of the side surface of the hole on the electron gun side, the coordinate width W in the X direction, the height By performing a computer simulation using H, etc. as parameters, a suitable shape of the electron beam passage hole can be designed. Needless to say, the agreement or correlation between the computer simulation result and the actual result is a matter that has been confirmed in advance.

According to the present invention, the hole 4a on the electron gun side,
It is preferable that the height h from the shadow mask surface on which the mask 4b is formed to the ridges 8, 8b, 8e is not more than one tenth of the thickness t of the metal plate constituting the shadow mask 1. Due to the height h, a part of the electron beams reflected on the side surfaces 10, 10b, 10e of the holes 4a, 4b on the electron gun side is related to a single reflection related to a decrease in the color purity of the screen. Electron beams can be prevented from reaching the phosphor screen. Considering the path of the electron beam reflected on the side surface of the hole on the electron gun side, the height h is the height h from the outer periphery of the electron beam passage hole 2b on the shadow mask outer side to the ridge 10e in the outer peripheral direction. It is preferred that In addition,
Needless to say, the ridgeline portion 10, which extends over the entire circumference,
The height h at 10b may be used.

The electron beam passage holes 2a, 2b having such a shape
The shadow mask of the present invention having
It is preferably applied to a slit type shadow mask or a slot type shadow mask in which the side surfaces 10, 10b, 10e of a and 4b are formed in a plane.

If the height h exceeds one-tenth of the thickness t of the metal plate, for example, the side surface 10e of the hole 4b on the electron gun side
In some of the electron beams reflected at the screen, the electron beam related to the single reflection involved in the reduction of the color purity of the screen cannot be prevented from reaching the phosphor screen, and the color purity of the screen may be reduced. . Note that the lower limit of the height h is preferably about 3 μm for reasons such as easy production and prevention of deformation.

As described above, according to the shadow mask of the present invention, the electron beam passing hole formed in the shadow mask has the color purity of the screen of the electron beam reflected by the side surface of the hole on the electron gun side. The electron beam related to the single reflection involved in the decline,
It is configured to prevent it from reaching the phosphor screen. As a result, the reflected electron beam that lowers the color purity of the screen does not reach the phosphor screen, so that it is possible to prevent the color purity of the screen of the color CRT from lowering.

Next, an example of a method for manufacturing the above-described shadow mask will be described. The shadow mask of the present invention is not limited to the following manufacturing method.

The shadow mask 1 can be formed by a conventionally known method. Usually, it is performed in each step of photo etching, and is manufactured by a continuous in-line device. For example, a water-soluble colloid-based photoresist or the like is applied to both surfaces of an iron-nickel alloy material having a thickness t of about 0.10 mm or 0.08 mm, and dried. Thereafter, a photomask having the above-described shape pattern of the holes 3a and 3b on the fluorescent screen side is adhered to the front surface, and the shape pattern of the hole portions 4a and 4b on the electron gun side is formed on the back surface. The exposed photomask is brought into close contact, exposed to ultraviolet light such as high-pressure mercury, and developed with water. The hole 3a on the phosphor screen side,
The positional relationship between the photomask on which the pattern of 3b is formed and the photomask on which the patterns of the holes 4a and 4b on the electron gun side are formed and their shapes are determined by the hole 3a on the phosphor screen side formed on the obtained shadow mask. 3b and hole 4 on the electron gun side
They are designed and arranged in consideration of the positional relationship with a and 4b and their sizes. The exposed portion of the metal whose periphery is covered by the resist film image is formed in each of the shapes described above based on the difference in the etching progress rate of each portion. The etching is usually performed by performing a half-etching by spraying a ferric chloride solution from both sides after heat treatment or the like, and thereafter, one of the half-etched holes on both sides. After filling, a second etching to etch the other hole again.
This is performed by stepwise etching to form an electron beam passage hole. Thereafter, a shadow mask is manufactured by continuously performing post-processes such as washing and peeling.

In particular, in the present invention, the above-described dimensions (height h, thickness t of the metal plate) and shape parameters (incident angle β of the electron beam, angle α of the side surface of the hole on the electron gun side, X direction) Can be adjusted to the above-mentioned preferable range by changing the etching mask pattern and the etching conditions in consideration of the material and the thickness of the metal plate material. At this time, the dimensions described above can be adjusted by arbitrarily setting the first etching condition and the second etching condition. Specific examples of the etching conditions include the temperature, viscosity, injection pressure, and selection of the side to be clogged with the etching solution.

The manufactured shadow mask is processed into a predetermined shape by stretching or pressing, and then subjected to a surface blackening process. This surface blackening treatment is performed to prevent the generation of secondary electrons, heat radiation, rust, and the like, and is particularly effective in improving corrosion resistance.

[0035]

The present invention will be described more specifically with reference to the following examples and comparative examples.

Example 1 A computer simulation was performed on the cross-sectional shape of an electron beam passage hole of a shadow mask and the path of an electron beam passing through the electron beam passage hole. In Example 1, the shape of the electron beam passage hole was changed as shown in FIG.
Based on the dimensions shown in FIG. 4A, the electron beam passage holes shown in FIG. An electron beam is passed through the electron beam passage hole.
The path of the electron beam incident at an angle β of 2 ° and reflected by the side surface of the hole on the electron gun side was simulated. Here, the thickness t of the metal plate material is 0.100 mm, and the ridge portion (intersection position)
The simulation was performed with a height h of 5.0 μm and an angle α of the hole side surface on the electron gun side of 78.7 °.

As a result, part of the electron beam reflected on the side surface of the hole on the electron gun side did not reach the phosphor screen as it was, and its path was obstructed on the side surface of the hole on the phosphor screen side. From the results of such a simulation, it is estimated that the shadow mask of the first embodiment is effective for preventing a decrease in the color purity of the screen.

Example 2 In Example 2, the shape of the electron beam passage hole was based on the dimensions shown in FIG. 5A, and the electron beam passage hole shown in FIG. 5B was formed. In the second embodiment, the height h up to the ridge is 7.2 μm, the angle α of the side surface of the hole on the electron gun side is 81.9 °, and the other embodiments are the same as in the first embodiment.
A simulation was performed in the same manner as described above.

As a result, only a small part of the electron beam reflected by the side surface of the hole on the electron gun side reaches the phosphor screen as it is, and most of the electron beam is reflected by the hole on the phosphor screen side. The path was obstructed on the side. From the results of such a simulation, it is estimated that the shadow mask of the second embodiment is effective in preventing a decrease in the color purity of the screen.

Comparative Example 1 In Comparative Example 1, the shape of the electron beam passage hole was based on the dimensions shown in FIG. 6A, and the electron beam passage hole shown in FIG. 6B was formed. In Comparative Example 1, a simulation was performed in the same manner as in Example 1 except that the height h up to the ridge line portion was 11.0 μm, the angle α of the hole side surface on the electron gun side was 86.4 °.

As a result, a part of the electron beam reflected on the side surface of the hole on the electron gun side did not hinder the path of the electron beam on the side surface of the hole on the phosphor screen side, and reached the phosphor screen as it was. From the results of such a simulation, it is estimated that the shadow mask of Comparative Example 1 causes a reduction in the color purity of the screen.

Comparative Example 2 In Comparative Example 2, the electron beam passage hole shown in FIG. 7B was formed based on the shape of the electron beam passage hole shown in FIG. 7A. In Comparative Example 2, a simulation was performed in the same manner as in Example 1, except that the height h up to the ridge line was 14.1 μm, the angle α of the hole side surface on the electron gun side was 87.6 °.

As a result, a part of the electron beam reflected on the side surface of the hole on the electron gun side did not hinder the course of the electron beam on the side surface of the hole on the phosphor screen side, and reached the phosphor screen as it was. From the results of such a simulation, it is estimated that the shadow mask of Comparative Example 1 causes a reduction in the color purity of the screen.

(Results of Confirmation Experiment) The thicknesses of Examples 1 and 2 and Comparative Examples 1 and 2 were 0.10 m.
m, a photosensitive material is applied to a metallic material (L / C material), dried, and then the pattern of the stretchable shadow mask is exposed, developed,
Each processing such as etching and peeling was sequentially performed, and further, a stretching process was performed to form a shadow mask having the same shape as the simulated shape. In the production of the shadow mask and the formation of the electron beam passage hole, the shape was controlled by changing the etching mask pattern and the etching conditions while considering the material and thickness of the metal plate. Specifically, the height h, the thickness t of the metal plate material, and other shape parameters (the incident angle β of the electron beam, the angle α of the side surface of the hole on the electron gun side, the coordinate width W in the X direction, the height H, Etc.)
The dimensions described above were adjusted by arbitrarily setting the first etching condition and the second etching condition. Using the obtained shadow mask, the same evaluation as in the simulation was performed.

As a result of evaluating the red purity of the CRT screen, the shadow mask corresponding to the first embodiment has the highest purity, followed by the second embodiment. However, it was confirmed that the shadow masks corresponding to Comparative Examples 1 and 2 had deteriorated color purity.

[0046]

As described above, according to the shadow mask of the present invention, the electron beam passing hole has a predetermined angle β with respect to the shadow mask surface in which the hole on the electron gun side is formed.
Since the electron beam irradiated at the side and partially reflected by the side surface of the hole on the electron gun side is formed so as to be blocked by the side surface of the hole portion on the fluorescent screen side or returned to the electron gun side, the screen Can prevent the electron beam related to the single reflection, which is related to the reduction in color purity, from reaching the phosphor screen. As a result, it is possible to prevent a decrease in the color purity of the screen of the color CRT.

At this time, since the height from the shadow mask surface where the hole on the electron gun side is formed to the ridge line is set to 1/10 or less of the thickness of the metal plate material, the height of the hole on the electron gun side is reduced. Among the electron beams reflected on the side surface, it is possible to further prevent the electron beam related to the single reflection related to the reduction of the color purity of the screen from reaching the phosphor screen. As a result, it is possible to prevent a decrease in the color purity of the screen of the color CRT.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a cross-sectional form of an electron beam passage hole formed in a shadow mask 1 of the present invention.

FIG. 2 is a mounting view of a stretch type shadow mask having a slit type electron beam passage hole, and the electron beam through hole has a cross-sectional shape shown in FIG.

FIG. 3 shows an angle β at which an electron beam enters the shadow mask surface, an angle α taken by the side surface of the hole on the electron gun side with respect to the shadow mask surface, and a side surface of the hole from the ridge line to the phosphor screen side. FIG. 3 is a cross-sectional configuration diagram of an electron beam passage hole showing a relationship between a coordinate width W in an X direction to an end portion and a height H (= th−h) from a ridge line portion to a shadow mask surface on a phosphor screen side.

FIG. 4 is a computer simulation result of an electron beam passing hole and a cross-sectional shape of the electron beam passing through the electron beam passing hole in Example 1.

FIG. 5 is a computer simulation result of a cross-sectional shape of an electron beam passage hole and an electron beam passing through the electron beam passage hole in Example 2.

FIG. 6 is a computer simulation result of a cross-sectional shape of an electron beam passage hole and an electron beam passing through the electron beam passage hole in Comparative Example 1.

7 is a computer simulation result of a cross-sectional shape of an electron beam passage hole and an electron beam passing through the electron beam passage hole in Comparative Example 2. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Shadow mask 2a, 2b Electron beam passage hole 3a, 3b Hole on fluorescent screen side 4a, 4b Hole on electron gun side 6, 6b, 6e Side face 7, 7b, 7e End of hole on fluorescent screen side 8, 8b, 8e Ridge line 9 End of electron gun side hole 10, 10b, 10e Side surface of electron gun side hole α Angle taken by side of electron gun side hole with respect to shadow mask surface β Electron beam is shadowed Angle incident on mask surface θ Angle of reflected electron beam with respect to horizontal axis t Thickness of metal plate h Height from ridge W Width in X direction from ridge to side edge of hole on phosphor screen side Coordinate width H Height from ridge to shadow mask surface on phosphor screen S Opening width of hole on phosphor screen P Opening width of hole on electron gun side

Continued on the front page (72) Inventor Yoko Ochiai 1-1-1 Ichigaya Kagacho, Shinjuku-ku, Tokyo Dai Nippon Printing Co., Ltd. F term (reference) 5C031 EE02 EF07 EH04

Claims (2)

[Claims] An electron beam passing hole formed by etching a metal plate material and having a hole on an electron gun side on which an electron beam enters and a hole on a phosphor screen side on which the electron beam exits is formed by the electron beam passing hole. In a shadow mask having a ridge portion formed by intersecting a side surface of a hole on the gun side and a side surface of a hole on the phosphor screen side, a shadow mask surface on which the hole on the electron gun side is formed The electron beam radiated at a predetermined angle β and partially reflected by the side surface of the hole on the electron gun side is obstructed by the side surface of the hole on the phosphor screen side or on the electron gun side. A shadow mask, wherein the electron beam passage hole is formed so as to return. 2. The method according to claim 1, wherein a height from a surface of the shadow mask, in which the hole on the electron gun side is formed, to the ridge is less than one-tenth of a thickness of the metal plate. Item 7. The shadow mask according to Item 1.