JPH0531256B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field of the invention] This invention uses a fiber plate as a substrate,
The present invention relates to an improvement in a method for manufacturing a fluorescent screen having a fluorescent layer formed on its surface. [Technical Background and Problems of the Invention] Image tubes, such as radiation image intensifier tubes, which generally have a built-in fluorescent screen are widely used for medical diagnosis and industrial non-destructive testing. This type of radiation image intensifier tube is constructed as shown in FIG. 1, and has an input surface 2 disposed inside the input side of a vacuum envelope 1 mainly made of glass and partially made of a thin metal plate. On the other hand, inside the output side of the vacuum envelope 1, an anode 3 and an output surface 4 are provided,
Further, a focusing electrode 5 is disposed on the side inside the vacuum envelope 1. The input surface 2 has a CsI/Na input phosphor layer 7 formed on the output side (concave side) of a spherical Al substrate 6, and a photocathode 8 further formed on this input phosphor layer 7. ing. Also, the output surface 4 is connected to the substrate 9
An output phosphor layer 10 is formed thereon. In operation, the radiation (not shown) excites the input phosphor layer 7 as it passes through the object (not shown) and is modulated by the radiation transmittance of the object.
The excitation light of the input phosphor layer 7 gives optical energy to the photocathode 8 and causes the photocathode 8 to emit electrons. These electrons are accelerated and focused on the output phosphor layer 10 by the electron lens action formed by the anode 3 and the focusing electrode 5, causing the output phosphor layer 10 to emit light. In this process, electrons are multiplied, and an image much brighter than the light image obtained at the input phosphor layer 7 is obtained on the output surface 4.
The object can be easily observed using this optical image. The output screen 4 of such a radiation image intensifier tube
There is an example in which a fiber plate (optical fiber bundle plate) is used as a holding substrate for the output phosphor layer 10 in the structure of 1. In contrast, it is useful to improve the contrast characteristics of radiographic image intensifier tubes. The outline of this proposal is shown in FIG. 2, in which an output surface 4 formed by forming an output phosphor layer 10 on a fiber plate 11 serving as a substrate is placed on the output side of the vacuum envelope 1. This proposal uses a conventionally well-known fiber plate as a part of the vacuum envelope 1 and does not lead the image signal of the radiation image intensifier tube directly outside the vacuum envelope 1, but is currently widely used. On the other hand, it has the advantage that the application of a high positive voltage as an accelerating voltage can be the same as in the conventional example shown in FIG. However, in order to improve the contrast characteristics using the fiber plate 11, simply forming the phosphor layer 10 on the fiber plate 11 will cause problems with the structure of the fiber plate 11 itself and the influence of the output window glass 12. Therefore, there is a limit to significantly improving contrast. The output surface 4 is formed by the following process. The fiber plate 11 is sliced into an appropriate thickness and polished. A phosphor is applied onto the fiber plate 11 by a deposition method such as a centrifugation method, a sedimentation method, or an electrodeposition method.
Apply to a thickness of ~10 μm. At this time, the fluorescent particles 2
In order to prevent the fiber plate 1 from detaching from the fiber plate 11, a glassy solvent is used to strengthen the adhesion between the two. After forming an NC film on the phosphor layer 10, Al vapor deposition is performed to form a metal back layer, and the output surface 4 is obtained after thermally decomposing the NC film. The degree of optical contact between the phosphor particles 21 and the fiber plate 11 is increased by the glassy solvent used in this step. On the other hand, the light transmitted within the fiber plate 11 will be explained with reference to a functional diagram of the fiber plate 11 consisting of a core material 31, a covering material 32, and an absorber 33 as shown in FIG. Here, the glass refractive index n ₁ of the core material 31 is 1.8, and the glass refractive index n ₂ of the coating material 32 is
Set it to 1.5. Further, when the refractive index n ₀ of vacuum is 1 and the angle of incidence of light on the fiber plate is θ ₀ , θ ₀ is expressed by the following equation. n ₀ sinθ ₀ =√ ₁ ² − ₂ ^2From this formula, θ ₀ is 90°. For light having an incident angle of 90°, the refraction angle of the core material 31 is 33.7°. In addition, the core material 31
The total reflection angle θ _C at the interface between the surface and the covering material 32 is 55.9°. By the way, for light whose θ ₁ is 33.7°, the incident angle θ _C at the interface between the core material 31 and the covering material 32 is 56.3°, which is larger than the critical angle, so it propagates through the fiber plate 11 while repeating total reflection, and the light is emitted. It is taken out from the surface 34. The aforementioned phosphor particles 21 and fiber plate 1
By increasing the degree of contact with the light incident surface 35 side of the core material 31, as shown in FIG.
The light beam at an angle of 33.7 degrees will be emitted from the light exit surface 34 at an angle of 90 degrees. fiber plate 11
By forming the phosphor layer 10 thereon, light is emitted from the light emitting surface in all directions at an angle of 0 to 90 degrees. Now, when the light emitted from the fiber plate 11 enters the output window glass 12 of the radiation image intensifier tube, the light returns to the output surface 4 from the output window glass inner surface 36 by well-known Fresnel reflection. exist. To explain this as shown in FIG. 4, the light emitted from the phosphor particles 21 is
A part a of the light emitted from the output window glass 12
The light is reflected from both surfaces of the light and returns to the fluorescent surface 4. This light becomes scattered light at a location different from the location where the light is emitted, and is superimposed with light specific to that location, causing a reduction in contrast characteristics. Regarding the course of transmitted light within the fiber plate 11, as shown by path b in FIG. The phosphor layer 10 enters other core materials and is further diffused over a wide range.
To the side or the light emitting surface 3 of the core material 31 and the covering material 32
It is emitted from 4. There is also a light path c that is transmitted through the covering material 32 or the absorber 33, through which light should not originally be allowed to pass. The fact that these lights are emitted from the light emitting surface 34 is also one of the causes of deterioration of contrast characteristics. The above is an outline of the restrictions on the contrast characteristics due to light scattering factors due to refraction and reflection, focusing on the path of light on the fluorescent surface 4 using the fiber plate 11. It is known that the fiber plate 11 has optical defects due to its manufacturing process. This optical defect becomes a surface defect in the radiation image intensifier tube, and becomes a major hindrance in medical diagnosis. In order to prevent this, it has been confirmed that if the fiber plate 11 is sliced thinly to a thickness of 2 mm or less, the frequency of occurrence of the above defects will be reduced and good high-quality images can be obtained, and there are prospects for practical application. Ta. However,
The thin fiber plate 11 has the disadvantage that its contrast characteristics are lower than that of a thick fiber plate. The present invention was made in order to provide a fluorescent screen for a radiation image intensifier tube that has both high contrast characteristics and high quality performance. [Object of the Invention] An object of the present invention is to provide a method for manufacturing a fluorescent screen having a structure completely different from that of conventional fluorescent screens using a fiber plate as a substrate, and to improve the contrast characteristics and screen quality of the fluorescent screen to those of conventional fluorescent screens. This is a significant improvement over the previous model. [Summary of the Invention] The present invention provides a fluorescent screen in which a fluorescent surface is formed on the surface of a fiber plate and a metal back layer is formed on the surface of the fiber plate. A fluorescent screen comprising the steps of removing a part of the core material of the fiber plate component over a wider area, and forming a light absorption layer on this side excluding at least the upper surface of the core material. It is in the manufacturing method. [Embodiments of the Invention] The fluorescent screen according to the present invention uses a fiber plate with a core diameter of 20 μm or less as a supporting substrate,
A granular, plate-like or layered phosphor layer is provided on one surface, and a metal back layer is formed.
The thickness of the fiber plate is 3 mm or less. Embodiments of the invention will be described below with reference to FIGS. 5 and 8. The fluorescent screen is constructed as shown in FIG. 5, and the same parts as in the conventional example are given the same reference numerals. The fiber plate 11 is sliced into a desired thickness, preferably in the range of 0.5 to 2 mm, and both sides are optically polished. One surface thereof is a light entrance surface 35 and the other surface is a light exit surface 34.
Further, the cross-sectional shape is usually a structure consisting of a core material 31, a covering material 32, and an absorber 33 of the main light transmission section. There are several methods for forming the phosphor layer 10 on the light incident surface 35 of the fiber plate 11, but when using the sedimentation method, the fiber plate 11 is placed inside the container.
A suspension in which the phosphor particles 21 are dispersed is poured into this container and left to stand still. The thickness of the phosphor layer of the phosphor particles 21 that has settled by gravity can be determined depending on the amount of dispersion of the phosphor particles 21, and is usually 5 to 10 μm.
are used. Since the suspension contains a glassy solvent (water glass solution), the phosphor layer 10 will not be detached even if the fiber plate is pulled up from the container. A thin film of NC lacquer film is applied under tension on the phosphor layer 10 to make the surface of the phosphor layer 10 continuous. Then, a metal back layer 41 of about 5000 Å made of a light metal that easily transmits electron beams is formed on this by vacuum deposition. The steps described above are commonly used in the production of fluorescent screens. In order to remove a part of the core material 31 of the fiber plate 11 on the light exit surface 34 side, metal ion components of the glass material components are removed in order to make the core material 31, the coating material 32, and the absorber 33 have different refractive indexes. Selective etching is performed by taking advantage of the difference in the etching rates of both acids. Through this process, the core material 31 is etched, and the recess 4
2 is formed. Acid is generally 12%
If nitric acid is used, the shapes of the covering material 32 and the absorbent body 33 will not be eroded, and by controlling the etching time, the desired depth of the recess can be obtained. However, if you want to make the shape of the recessed part spherical by heat etching, you can also use another acid such as 10% hydrochloric acid or a mixed acid of 5% hydrochloric acid and 5% sulfuric acid to perform etching continuously or intermittently. It is possible. As a reference example, FIG. 6 shows the shape of the recessed portion of the core material 31 of the fiber plate 11 formed by etching with 12% nitric acid at room temperature. Since acid is used in this step, in order to prevent damage to the phosphor layer 10 side, as illustrated in FIG.
An etching jig is used that prevents it from turning to the sides. Here, it consists of a container 51 having an opening, an airtight ring 52, and a fastener 53, and is filled with an etching liquid 54 to dissolve and remove the core material 31. The diameter d ₁ of the opening of the container 51 is the fiber plate 11
This is also the diameter of the area where the recess 42 is formed, and must satisfy the conditions that it is smaller than the diameter d ₂ of the fiber plate 11 used and larger than the diameter d ₃ of the effective light image area of the output surface 4. That is, d ₃ ≦
The relationship d ₁ ≦d ₂ holds true. It has been confirmed that the etching depth, that is, the depth of the recess 42, is approximately proportional to the etching time when the processing conditions such as the type of acid and temperature are the same, so it can be arbitrarily selected. The depth is preferably 20 μm or less. After cleaning the fiber plate 11 so that no etching solution 54 remains on the light exit surface 34, the fluorescent screen is dried and taken out from the container 51. The above is the basic process of removing a part of the core material 31 of the fiber plate 11 to form the recess 42. This has the economical advantage that the recesses 42 can be formed using only the phosphor layer 10 that does not have surface defects that tend to occur during the process of forming the phosphor layer 10. The next step is the light absorption layer 43 shown in FIG.
is formed on the wall surface 45 of the recess 42 excluding the core upper surface 44 and on the surfaces 46 of the covering material 32 and the absorbent body 33. As a material for the light absorption layer 43, carbon, which itself is black, can easily be used, but considering the weak adhesion of the carbon film and the negative effects within the radiation image intensifier tube, a more suitable material is carbon, which is made of a thin film of metallic material. A light absorption layer 43 is formed as a lever. First, a fluorescent screen having recesses 42 is placed in a vacuum evaporator 61, and an evaporation source 62 is loaded with aluminum pellets 63. At this time, the positional relationship between the two is as shown in FIG.
Tilt (α°) to The inclination angle (α) is the recess 42
The light absorbing layer 43 can be formed around almost the entire circumference of the recessed wall surface 45 by rotating (rotating) the fluorescent screen while maintaining this inclination angle. . In vacuum deposition, aluminum is deposited at a solid angle, so
If the light absorbing layer 43 is formed by rotating and revolving, as in the case of the fluorescent screen shown in FIG. 2B, a large number of fluorescent screens can be efficiently formed. Of course, it is also possible to form the light absorption layer 43 without rotating or revolving. If it does not rotate at all, the wall surface 45 of the recess 42 of the fiber plate 11
Although a partial light absorption layer 43 is formed in this case, it is clear that there is an effect of improving contrast characteristics even in this case. In forming the light absorption layer 43 by such a vapor deposition method, not only the recess 42 but also the surface 46 of the coating material 32 and the absorber 33 face the evaporation source, so a sufficient concentration of light absorption can be obtained here as well. Needless to say, layer 43 is formed. In addition to aluminum, Ni and Cr can be used as vapor deposition materials.
A blackish-brown or brownish-brown light absorbing layer 43 having properties comparable to those of other colors is possible. In this step, it is almost unnecessary to form the light absorption layer 43 on the phosphor layer 10 side, so it is preferable to use a shielding member that does not adhere to this side. This vapor deposition process is performed under the following conditions. First, the inside of the device 61 is arranged as described above and
Pressures below 10 ^-4 Torr should be evacuated. The thickness of the thin film that will become the light absorption layer 43 is measured using a monitor (not shown) and is deposited in the range of 100 to 2000 Å on the surface to which it is deposited.
Experiments have revealed that a thickness of 100 to 500 Å is suitable considering the shape. The adhesion strength of the light absorption layer 43 is sufficient even when deposited at almost room temperature, but to further improve it, a fluorescent screen (adhesion surface) of 100%
Heating to ~300°C is effective. In forming the light absorption layer 43, the contrast and brightness of the fluorescent screen can be selected by appropriately combining some of these vacuum deposition conditions. Formation of the light absorption layer 43 by such a vacuum evaporation method has many advantages in that it can prevent dirt and dust from adhering to minute surfaces in a clean environment, can be formed uniformly, and can be efficiently produced in large quantities. Further, when this fluorescent screen is disposed inside a radiation image intensifier tube, the light absorption layer 43 does not fall off, so it does not become dust inside the tube, which is more advantageous than other materials. Now, the phosphor layer 10 of the fiber plate 11
A part of the core material 31 on the opposite side of the recess 4 is removed.
2 and a light absorbing layer 43 is formed on the wall surface 45 excluding at least the upper surface portion 44 of the core material, the covering material 32, and the surface 46 of the absorber 33. The fluorescent screen has the following effects. As shown in FIG.
1 and is emitted from the light emitting surface 34, the emitting position of the light is almost limited to the core upper surface 44 (path a), impairing the function of the fiber plate 11 (path b), or not contributing to the function. The light (path c) is stopped by the light absorption layer 43 and is not emitted to the outside and is not reflected inside. Therefore, when the light inside the fiber plate 11 focuses on one core material 31, it becomes a single pixel, and the pixel component has excellent contrast characteristics with extremely little influence of superimposition due to scattering of light inside the fiber plate 11. Become. Furthermore, due to the formation of the concave portion 42, the light that has been transmitted through the core material 31, which is the main light transmission portion, by total reflection is emitted from the core material upper surface portion 44, so that the light emission angle distribution as a light emitting surface is narrower than in the case of a normal flat fiber plate, and when the light propagates from its exit surface to the output window glass, it is also narrower and the angle of incidence at that time becomes smaller, so the rate of Fresnel reflection is extremely reduced. do. Since the return of light due to this Fresnel reflection is one of the causes of the deterioration of contrast characteristics, it can be seen that the narrowing of the light emission angle distribution due to the formation of the recesses 42 very effectively contributes to the improvement of contrast characteristics. Furthermore, the return light due to Fresnel reflection generated at the boundary surface of the output window glass due to the formation of the light absorption layer 43 is directed into the fiber plate 11, but when it enters the portion where the light absorption layer 43 is formed, it is caused by this. It also has the effect of preventing the light from being absorbed and entering the fiber plate 11 again, causing light scattering. By forming the concave portions 42 and the light absorption layer 43, it is possible to solve the problem of contrast reduction due to the thinning of the fiber plate 11, which has been a problem in the past, so that thin fiber plates of 2 mm or less can be put to practical use and have high quality. Images can also be provided at the same time. Therefore, the subject can be clearly identified with the high-definition images that are particularly required for medical diagnosis, and the high-definition images can be provided with fluorescent screens and radiation image intensifiers that do not interfere with the diagnosis. . Next, another embodiment of the present invention will be described with reference to FIGS. 7 to 10. As shown in FIG. 7, the fiber plate 1 of the fluorescent screen
1, before forming the phosphor layer 10 on the fiber plate 11, a part of the core material 31 on the surface that will become the light emitting surface 34 is dissolved and removed with acid to form the recess 42. can be formed. After this step, by forming the phosphor layer 10 and the metal back layer 41 on the light incident surface 35 in the manner described above, a phosphor screen having a similar structure can be obtained. A feature of this method is that corrosion of the phosphor layer 10 due to acid can be prevented, but special care must be taken to prevent dirt and dust from forming the minute portions of the recesses 42 throughout the process of forming the phosphor screen. Forming a recess on one side of the fiber plate 11, that is, the light exit surface 34 side, and not forming a recess on the light incidence surface 35 side, that is, the phosphor layer 10 side, means that the phosphor layer 10 is formed on the flat surface of the fiber plate 11. Since the formation of the phosphor layer 10 is generally performed in a solution, this flat surface can be used to prevent liquid from remaining in the recesses and to form a phosphor layer with a uniform thickness. This often results in improved process efficiency. In FIG. 7, the opening of the etching jig is filled with the etching liquid 54, but on the contrary, the etching liquid 54 is
The recesses 42 can be formed as described above by immersing the fiber plate 11 or the phosphor screen on which the phosphor layer 10 is formed into a container filled with . Needless to say, stirring and heating the solution are effective in shortening the etching time. The recesses 42 are formed in a wider range than the effective output image diameter of the fluorescent screen, but the amount of light emitted from each core material 31 varies depending on the depth of the recesses 42, so it depends on the type of radiation image intensifier tube. Eventually, this can be used to create recesses 4 in the center and periphery of the fluorescent screen.
2 can be varied to help improve the brightness uniformity of the output light image. The light absorption layer 43 is preferably formed with a uniform concentration on the surface on which it is formed, but the core material 3 of the fiber plate 11
The diameter of the recess 42 is usually 5 to 20 μm, and when the depth of the recess 42 is 15 μm or more, the light absorption layer 43 is coated on all of the wall surfaces 45 of the recess 42, as shown in FIG. It may not be formed. In addition, the light absorption layer 43 on the wall surface 45 of all the recesses 42
However, it is likely that the adhesion area will not be uniform. In such a case, the process is improved by adjusting the inclination angle and rotation speed and using a plurality of evaporation sources to avoid these problems as much as possible. When the light absorption layer 43 is formed as shown in FIG. 9, it can be seen from the path of light that it has the same effect as in FIG. 6, and it has been confirmed that the effect on improving contrast characteristics is almost the same. Ta. As the simplest method, it is possible to form the light absorption layer 43 by vapor deposition from one direction, so as shown in FIG. 46 has a light absorption layer 4
It can be seen that 3 can be provided. If this method is carried out intermittently or continuously, the light absorption layer 43 as shown in FIG. 5 or 9 will be obtained. As a method for forming the light absorption layer 43 by vacuum deposition on the upper surface 46 of the covering material 32 and the absorber 33, as shown in FIG. Place it in At this time, a thin layer of low-temperature decomposable resin is buried to cover the upper surface portion 44 of the core material in the recess 42 . Next, by vapor depositing metal as described above, a light absorption layer 43 having a sufficient concentration can be formed on the upper surface portion 46. The resin embedded in the recesses 42 can be completely removed by heating the fluorescent screen or fiber plate in a heat treatment furnace, preferably a vacuum heat treatment furnace in which oxidation is not promoted. Note that the larger the angle between the evaporation source 62 and each recess 42 of the fluorescent screen or fiber plate is, the more the light absorption layer 43 is formed on the wall surface 45. If vacuum evaporation is performed with almost parallel movement (at a certain angle of inclination), the light absorption layer 4 will be formed on the upper surface 46 and the wall surface 45 at the same time.
3 is formed, and this method has the advantage that there is no need to provide the vacuum chamber 61 with a complicated mechanism for rotation and revolution. Conversely, if the evaporation source 62 is used frequently, the same result will occur. Here, the light absorption layer 43 is formed on the fiber plate 11 having the concave portions 42, but since the adhesion strength of the metal thin film by vacuum evaporation is high and it does not peel off during the process of forming the phosphor layer 10, the light absorption layer 43 is After forming phosphor layer 43, phosphor layer 10 and metal back layer 41 can be formed to obtain the desired phosphor screen. The specific contrast characteristics of the fluorescent screen of this invention obtained through the above steps were improved by 10%.
This was done by contrast measurement. There are two types of samples: a fluorescent screen and a radiation image intensifier tube equipped with the fluorescent screen. To define the contrast, a shield plate corresponding to 10% of the light emitting area was placed at the center of these samples, and the center line of the light emitting area was scanned with a spotmeter. The maximum brightness obtained at this time is a, and the lowest brightness at approximately the center of the shield plate is b.
As, the contrast is (a-b)/a×100
Expressed in (%). Therefore, the larger the obtained value, the better the contrast. First, the measurement results of the fluorescent screen are shown in the table below.

〔Effect of the invention〕

As described above, the present invention has the effect of extremely reducing the influence of superimposition due to scattering of light inside the fiber plate and significantly improving contrast.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view showing an example of a radiation image intensifier tube applied to the present invention, Fig. 2 is an enlarged sectional view showing the output section of Fig. 1, and Fig. 3 is a conventional fiber plate light beam. FIG. 4 is an explanatory diagram showing Fresnel reflection of a conventional image tube output section. FIG. 5 is a schematic sectional view showing an embodiment of the present invention. FIG. 6 is an embodiment of the present invention. FIG. 7 is a schematic view showing a jig for forming the core recess of the fiber plate of FIG. 6, and FIG. A schematic view showing the inside of a vacuum chamber used for forming a fluorescent screen in one embodiment, and FIGS. 9 to 11 are schematic sectional views showing other embodiments of the present invention. 1... Vacuum envelope, 2... Input surface, 3... Anode, 4... Output surface, 5... Focusing electrode, 6... Al
Substrate, 7... Input phosphor layer, 8... Photocathode, 9...
... Output board, 10 ... Output phosphor layer, 11 ... Fiber plate, 12 ... Output window glass, 21
... Fluorescent particle, 31 ... Core material, 32 ... Covering material, 33 ... Absorber, 34 ... Light exit surface, 35 ...
...Light incidence surface, 36...Output window glass inner surface, 41...
... Metal back layer, 42 ... Recessed part, 43 ... Light absorption layer, 44 ... Core material upper surface part, 45 ... Wall surface, 46
...On the surface, 51...Container, 52...Ring, 53
... Fastener, 54 ... Etching liquid, 61 ... Vacuum chamber, 62 ... Evaporation source, 63 ... Pellet.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a fluorescent screen in which a fluorescent surface is formed on the surface of a fiber plate and a metal back layer is formed on the surface of the fiber plate, wherein at least an effective light image on the light exit surface side of the fluorescent screen is provided. Fluorescence characterized by comprising a step of removing a part of the core material of a fiber plate constituent member in an area wider than the area, and a step of forming a light absorption layer on this side excluding at least the upper surface of the core material. Screen manufacturing method. 2. Form a phosphor layer and a metal back layer on the light incident surface of the fiber plate, and add the core material of the fiber plate that includes the effective light image area on the opposite surface and is located within the surface of the fiber plate to a core material solution solution. A method for manufacturing a fluorescent screen according to claim 1, characterized in that the fluorescent screen is removed by twisting the screen. 3. The method for manufacturing a fluorescent screen according to claim 2, wherein the core material dissolving solution uses one type or a mixture of acids. 4. The method for manufacturing a fluorescent screen according to claim 1, wherein the light absorption layer is formed using one or more of metal materials such as Al, Ni, and Cr by a vacuum deposition method. 5. A fiber plate fluorescent screen with a concave core on the light exit surface side is placed in a vacuum evaporation apparatus, and the inclination of the fluorescent screen with respect to the evaporation source is adjusted from the radiation position centered on the evaporation source. The fluorescent screen according to claim 1, characterized in that the light absorbing layer is formed by performing oblique vapor deposition in a range that does not include an angle that is a vertical plane, and forming a light absorption layer on at least the upper surface of the recessed portion of the core material. manufacturing method. 6. A method for manufacturing a fluorescent screen according to claim 5, characterized in that a shielding member is used to prevent the light absorption layer from adhering to the surface of the fluorescent screen on the fluorescent layer side. 7. A patent claim characterized in that when forming the light absorption layer, the fluorescent screen is arranged at an angle with respect to the evaporation source, and the light absorption layer is formed while the fluorescent screen is rotated or rotated or both. A method for manufacturing a fluorescent screen according to item 5.