JPH0378940A - Light emitting screen - Google Patents

Abstract

PURPOSE:To have a light emitting screen with high resolution, light emission efficiency, and thermal conductivity by arranging a number of holes or aggregate thereof on both sides of the surface of a light emitting layer and the surface of a supporting element layer for it. CONSTITUTION:Holes or aggregate thereof are provided on both sides of the surface of a light emitting substance layer 1 and the surface of a light emitting substance layer supporting element 2, wherein the max. length of the opening in this aggregate shall be 700nm through 300mum, and the min. distance of this opening in aggregate from other hole or the opening in aggregate shall be 700nm through 1mm. The depth of these holes or the aggregate thereof is set to more than 1/3 of the intrusion depth of an electron beam for light emission energization and below the thickness of the light emitting layer 1. This allows the brightness of a crystalline thin film light-emitting screen to be increased by several tens of percent or more without impairing the picture quality. Also the thermal characteristics as excellent originally can be maintained, and the display thus accomplished is equipped with high brightness, high precision, and long lifetime.

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD 1 The present invention relates to a luminescent screen used in a cathode ray tube or the like, and particularly to a luminescent screen comprising a crystalline phosphor thin film supported on a support as a luminescent layer. BACKGROUND OF THE INVENTION Currently, the most commonly used luminescent screens for cathode ray tubes and the like are those coated with powdered phosphor to form a luminescent layer. When these powder light-emitting layers are heated by irradiation with an electron beam or the like for light emission, the contact area between the powder particles is small, so heat conduction is poor and they are susceptible to adverse effects from temperature rise. Furthermore, since the powder generally has a particle size of 5 to 15 μm, there is a limit to resolution. On the other hand, cathode ray tubes with larger screens and higher definition are desired for television receivers and the like. In order to meet these demands, there is a trend to increase the output of the emitted electron beam and to reduce the diameter, but the above-mentioned drawbacks become noticeable in luminescent screens having a powder luminescent layer. Furthermore, display tubes for drawings and characters are also required to be more precise than before. In recent years, screens in which a single crystal film of a light emitting material or a tightly structured polycrystal film is grown on a supporting substrate as a light emitting layer have attracted attention as having superior characteristics in these respects. These membranes are dense and integral throughout, so
It has good thermal conductivity and has few problems with resolution. Also,
Since there are fewer crystal defects, it is also expected to improve luminous efficiency. However, the phosphor thin film has a drawback in that the brightness at the position where light should be emitted is low. This is because there are few factors that scatter light within the film, and due to the difference in refractive index between the inside and outside of the film, light emitted within the film that makes an angle of more than a certain angle with respect to the interface will not reach the interface. This is because the light is repeatedly reflected and reaches the end face of the film, where it is radiated outside the film. To solve this problem, US Patent No. 4,298,8
No. 20 proposes a structure in which V-shaped grooves are finely dug in the vertical and horizontal directions in the light emitting layer. This proposal aims to improve the brightness by allowing the light in the area surrounded by the groove to be reflected from the side surfaces of the groove and radiated to the surface.

[Problem to be solved by the invention]

Most thin film luminescent screens are made by growing a luminescent layer on a single crystal or glass substrate. In many cases, the refractive index of the light-emitting layer and the supporting substrate are approximately equal. Therefore, light generated in one light-emitting layer is transmitted to the support layer almost without hindrance, reflected on the surface of the support layer, and then propagated into the film by being reflected again on the surface of the light-emitting layer. Since the light-emitting layer usually has a thickness of 5 to 10 μmJl, whereas the support layer has a thickness of usually about 0.3 to 1 mm, it can be said that most of the propagating light is transmitted within the substrate. In the above-mentioned conventional technology, no consideration is given to light propagating within the support layer due to reflection on the support surface, and much of the light is transmitted to the film edge without being affected by the structure of the light emitting layer surface. Further, in the above-mentioned conventional technology, the electron beam excitation light is emitted from the entire portion surrounded by the groove, particularly from the contour of the groove. Therefore,
There is a problem in that the resolution of the image is limited by the size of the area surrounded by the groove. Furthermore, garnet crystal, which is often used as a single crystal phosphor, has strong resistance to etching solutions, has a small etch rate, and has approximately the same etch rate in the lateral direction and in the depth direction. For this reason, when forming deep grooves, the groove width increases, and when attempting to make the pattern finer, the light-emitting layer is significantly scraped, resulting in a problem of reduced brightness. Moreover, the grooves occupy a large area on the screen, so
There is a problem in that the groove is reflected on the image. Furthermore, in the conventional technology, there is a problem in that the portion surrounded by the groove has little lateral heat conduction, making it difficult to take advantage of the characteristics of the thin film phosphor. An object of the present invention is to provide a luminescent screen with high resolution, high luminous efficiency, and good thermal conductivity.

[Means for solving the problem] In order to achieve the above object, in a luminescent screen having a phosphor thin film as a luminescent layer, a large number of holes or aggregations of pores are arranged on both the surface of the luminescent layer and the surface of the support layer. This is what I did. FIG. 1 schematically shows the structure of the screen of the present invention, in which (a) is a sectional view perpendicular to the nuclear submarine, and (b) is a top view of the surface of the light emitting film layer. A possible method for forming the above structure is to place a shielding material having a large number of holes on the surface of the fluorescent crystal film and perform etching. [Function] When a thin film phosphor emits light, the light excited by an electron beam or the like is generated depending on the angle of incidence on the surface: 1) the light that passes through the support layer and is emitted from the surface to the outside; 2) the light that is emitted from the support layer. 3) those that are reflected at the interface between the surface and the outside and propagate within the film, and 3) those that travel within the light-emitting layer almost parallel to the surface. Of these, the light in 3) normally propagates from the light emitting position of the film to near the film edge, but according to the structure of the present invention, the pore structure on the surface of the light emitting layer reflects and scatters this light, and the light is transmitted to the support layer. send out. Furthermore, when the light (2) is incident on the wall surface of the pore structure on the surface of the support layer, the angle with the surface becomes small, and the light is emitted from the pore structure to the outside. At this time, the optimal value θ of the angle of the wall surface of the pore structure with respect to the membrane surface is given by the following equation, assuming that the refractive index of the support is n<0> and the refractive index of the outside is 00. θ=2sin or 1 (n0/n) Furthermore, since the structure of the present invention is a thank-you note pattern, it is relatively easy to reduce the size of the opening, making the structure less noticeable on the screen, and reducing the resolution. It also has the characteristic of being able to raise the height. The beam spot diameter of a commonly used electron beam for luminescence excitation is approximately 300 lL@, and sufficient resolution can be obtained by making the structure smaller than that. Since the wavelength of visible light is about 300 nm to 700 nm, the structure needs to be larger than this. Furthermore, since the fluorescent film according to the present invention is continuous throughout, deterioration due to heat is reduced. Furthermore, if powder is used as a shield, an expensive mask can be dispensed with. The procedure can be greatly simplified by etching through the holes in the protective layer.

【Example】

Example 1 The present invention will be explained below using examples. The single-crystal phosphor is manufactured using yttrium aluminum garnet (hereinafter abbreviated as YAG) with a composition formula of Y and A150.2 as a substrate, and a composition formula (Yo-sgTbo, *) containing an activator Tb using the LPE method. )iA], sOt□
obtained by growing a film of y A a ml) surface, the composition is in weight ratio: Y, O,: Tb, O,: Al, O,: Pb, O
: B, O. = 2.1386 : 0.2377 : 3.627
3 : 250 : 6.2285 in the melt, 1
Growth was carried out at 060° C. for about 5 minutes to obtain a phosphor single crystal film with a thickness of about 5 μm. This film emitted green light when excited by ultraviolet rays or electron beams. The film structure was formed by etching with hot phosphoric acid using the SiO□ film as a mask. First, a SiO□ film of about 1 μm was applied by sputtering to the single crystal film prepared as described above, and then NiFe and Cr films were respectively applied thereon. A resist agent was applied on top of this, and a 5 μm thick resist was applied as a light shield.
Graphite powder with a relatively uniform particle size of 10 μm from
Exposure was carried out by dispersing the particles so that approximately one layer was present in a 20μ heel area. Cr and NiFe! After cutting a pattern by milling, reactive ion etching (Reac
tive Ion Etching: RIE)
A pattern was formed on the SiO□ layer. For comparison, one with a pattern only on the surface of the light emitting layer, and
Two types were prepared, a light-emitting layer and a support layer attached to both surfaces, and etched with phosphoric acid at 160° C. for about 5 minutes. As a result, aluminum was vapor-deposited to a thickness of about 1100 nm on the surface of the light emitting layer to a depth of about 2.1 μm to form a metal back layer. The fluorescent film obtained by the above method was set in an electron beam irradiation device, and an electron beam with an acceleration voltage of 27 kV and a current of 100 nA was applied for 10 minutes.
The luminous output of the fluorescent film was investigated by irradiating it with a X10+m'' raster, and comparisons were made between single-sided, double-sided, and the film before pattern formation.Electron beam irradiation was performed from above the metal back layer to the light-emitting layer surface. The opening is 10 mm+ in diameter at a position 12 μm perpendicularly away from the light emitting surface to emit light emitted from the support layer surface.
The relative brightness was measured using a probe. The results are shown in Table 1. Table 1 Examples 2 to 4 In order to investigate the influence of the depth of the structure formed on the film, Example 1
Examples 2 to 5 were prepared in which patterns were formed on both sides and the depth of the structure was varied by changing the etching time using the same method as above. Table 2 shows a comparison of the light emission output when the accelerating voltage of the irradiated electron beam is 27 kV, and FIG. 2 shows the relationship between the structure depth and the light emission output as a graph. Further, Table 3 shows the results of measurements performed on the screen of the same example using the same method with the acceleration voltage of the irradiated electron beam being 9 kV. Furthermore, the relationship between the structure depth and the light emission output under these conditions is shown in a graph in FIG. It is thought that the light emission output is related to the penetration depth of the electron beam that excites the light emission. In this measurement, the penetration depth of the electron beam was approximately 3 μm under the conditions in Table 2 (acceleration voltage 27kV), and the penetration depth of the electron beam was approximately 3 μm under the conditions in Table 3 (acceleration voltage 9kV).
It is approximately 2 μm in diameter. The thickness of the light emitting layer is approximately 5 μm. From Figures 2 and 3, it can be seen that the light emission output reaches its maximum value in the range from the depth of the structure exceeding about one-third of the beam penetration depth to the thickness of the light emitting layer. . It can also be seen that the influence of the structure on the light emitting characteristics appears to be greater in FIG. 3 than in FIG. 2. Table 2 Table 3 This is because under the conditions shown in Figure 2, the electron beam penetrating from the bottom of the structure reaches the support layer before the depth of the structure exceeds the electron beam penetration depth, resulting in a decrease in the amount of light emitted. This is because it decreases. By making the penetration depth more than twice the depth shown in FIG. 3, a remarkable effect of the structure can be obtained. Examples 5 to 7 In order to investigate the relationship between the density and resolution of the structures of the present invention, Examples 5 to 7 having structures with different densities were prepared and visually compared. Same as Example 1. Using this method, we fabricated a luminescent screen with structures on both sides. At that time, the particle size of graphite and the density at which it is dispersed were varied to obtain films with different pore structure sizes and mutual distances on the film. Table 4 shows the average maximum diameter of the hole openings and the closest distance between the holes in the examples. The obtained luminescent screen was irradiated with an electron beam in the same manner as in Example 1, and visually observed from the opposite side of the irradiated surface to examine the resolution. In Example 5, the light emitted spread widely from the spot of the electron beam. In Example 6, the emission was 2-3+a
In Example 7, light emission was observed on the surface within lam in the range of m. From the above, it can be seen that good resolution can be obtained when the distance between the openings is within 1000 μm. Example 8 As a fluorescent film, on a non-alkali glass substrate. A ZnS film containing Mn as an activator was grown by electron beam evaporation. A ZnS:Mn polycrystalline film with a thickness of about 4 μm was obtained at a substrate temperature of 500° C. This film emitted orange light when excited by an electron beam. The structure of the present invention was formed on the phosphor film obtained as described above using nitric acid as an etchant. First, a SiO□ film of approximately 100 na+ is deposited on the fluorescent film by sputtering
It was formed to a thickness of . As in Example 1, two types of fluorescent layers were prepared: one with only the surface of the fluorescent layer and one with both surfaces. This is 0.01
Etching was performed for about 5 minutes using specified nitric acid. The fluorescent film is etched through the many holes in the 5in2 film of the protective layer, and each hole has a diameter of 4μ per approximately 10μm square.
A conical bow-like structure with a depth of about 2 μm and a diameter of about 2 μm was obtained. Table 5 shows the luminescence output obtained by measuring the fluorescent film obtained by the above method under the same conditions as in Example 1, in comparison with the film before structure formation. Table 5 It can be seen that the structure according to the present invention significantly improves the light emitting output.

【Effect of the invention】

According to the present invention, the brightness of a crystalline thin film luminescent screen can be significantly increased to several fractions of a second or more without degrading the image quality. In addition, the original excellent thermal properties can be maintained, which is useful for realizing display devices with high brightness, high definition, and long life.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view and a top view schematically showing a luminescent screen obtained by the present invention. FIG. 2 is a graph showing the relationship between the depth of the hole structure and the light emission output when the screen of the example of the present invention is irradiated with a 27 kV electron beam. FIG. 3 is a graph showing the relationship between the depth of the hole structure and the light emission output when the screen of the example of the present invention is irradiated with a 9 kV electron beam. Explanation of symbols 1... Luminescent layer 2... Support 3... Reflective film (metal back layer) 4... Luminescent layer surface structure 5... Support layer surface structure 1st 2nd Figure ◎ ◎ ◎ ◎ / 2 3 4 1 compliance: /7 (μ ki)

Claims (1)

[Scope of Claims] 1. A crystalline thin film of a substance supported on a support that emits light by electron beam excitation, which has pores or aggregations of pores on both the surface of the phosphor layer and the surface of the phosphor layer support. However, the maximum length of the opening of the hole or aggregation of holes is 300 μm or less70
0 nm or more, and the closest distance between the opening of the hole or hole aggregate and the opening of another hole or hole aggregate is 1
700 nm or more, and the depth of the hole or a collection of holes is at least one third of the penetration depth of an electron beam for excitation of light emission and at most the thickness of the light emitting layer. 2. A luminescent screen having the structure according to claim 1, wherein the thickness of the luminescent layer is at least twice the penetration depth of the electron beam for excitation of luminescence. 3. A method for producing a luminescent screen, characterized in that the hole or hole aggregate structure according to claim 1 is formed using dispersed particulate matter as a mask. 4. A method for manufacturing a luminescent screen, characterized in that the hole or hole aggregate structure according to claim 1 is formed by etching through a film defect hole that occurs in a protective layer formed on the surface. 5. A cathode ray tube comprising the luminescent screen according to claim 1.