JP2006164854A - Fluorescent screen and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorescent screen being hardly deteriorated and hardly causing discharge even when it is driven with high luminance, and to provide an image display device with the fluorescent screen incorporated therein. <P>SOLUTION: This fluorescent screen is provided with: phosphor ceramic pieces 6R, 6G and 6B arranged on an inorganic transparent substrate 7 and each having a size equivalent to a pixel; and a metal back layer 9 formed on surfaces of the phosphor ceramic pieces 6R, 6G and 6B. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a phosphor screen and an image display device, and more particularly to an electron beam excited thin image display device such as a field emission display device and a phosphor screen suitable for the image display device.

  Electron beam excited thin image display devices (electron beam excited flat panel displays) such as field emission displays (FEDs) have been developed as thin and large screen display devices. These image display devices emit light by exciting the phosphor forming the phosphor screen with an electron beam by emitting the electron beam from a position close to several millimeters or less with respect to the phosphor screen serving as an anode. is there. In such an image display device, an electron source corresponding to each pixel is provided.

  A fluorescent screen of a conventional electron beam excitation display is coated with a powder phosphor having a particle size of several μm. That is, a powder phosphor is applied on a glass substrate, a pattern is formed by a light exposure method or the like, and a phosphor pattern of three primary colors is formed by applying this method to each of red, green, and blue phosphors. Has been made. This is a common practice in CRTs (cathode ray tubes), and phosphor screens are formed using powder phosphors also in electron beam excited flat panel displays.

As a phosphor suitable for CRT, a powder phosphor of silver activated zinc sulfide as a blue phosphor, copper activated zinc sulfide as a green phosphor, and europium activated yttrium oxysulfide as a red phosphor is known. These phosphors are also used in electron beam excited flat panel displays. However, the zinc sulfide phosphor is easily deteriorated and it is difficult to extend the life of the display. Further, when the excitation intensity is increased to increase the luminance, luminance saturation occurs and the light emission efficiency decreases. On the other hand, when the excitation intensity is increased or the life is extended, powders such as europium-activated yttrium oxide, terbium-activated yttrium silicate, and cerium-activated yttrium silicate are suitable for the projection CRT. It is also conceivable to select a rare earth phosphor as a phosphor for an electron beam excited flat panel display. However, even these phosphors are greatly deteriorated under strong excitation.
JP 2003-229075 A

  As described above, in the electron beam excited flat panel display, the phosphor screen using the conventional powder phosphor is greatly deteriorated when the display is performed with high luminance, and the life is shortened. Further, as disclosed in Patent Document 1, in an electron beam excited flat panel display, when the acceleration voltage is increased for the purpose of obtaining high brightness, discharge is likely to occur because the anode and the cathode are close to each other.

  The present invention has been made to solve such a technical problem, and an object of the present invention is to provide a phosphor screen that is less deteriorated even when driven at a high luminance and is less likely to cause a discharge, and the phosphor screen. It is providing the image display apparatus which incorporated.

  The features according to the embodiment of the present invention are that, on the phosphor screen, phosphor ceramic pieces having a size corresponding to pixels arranged on an inorganic transparent substrate, and a metal back layer formed on the surface of the phosphor ceramic pieces It is to provide.

  In addition, in the image display device, the feature according to the embodiment of the present invention is that the phosphor ceramic piece having a size corresponding to the pixels arranged on the inorganic transparent substrate and the metal back layer formed on the surface of the phosphor ceramic piece. And a rear plate that is arranged to face the face plate and has a plurality of electron sources that emit electrons to each pixel of the phosphor screen.

  ADVANTAGE OF THE INVENTION According to this invention, even when it drive | operates with high brightness | luminance, there can be provided the fluorescent screen with little deterioration and little discharge generation, and an image display device incorporating this fluorescent screen.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description of the drawings, the same portions are denoted by the same reference numerals, and overlapping descriptions are omitted.

(Embodiment)
As shown in FIG. 1, the image display device 1 according to the present embodiment excites the phosphor layer 6 with an electron beam emitted from an electron source 2 provided facing each pixel, and this excitation A thin image display device configured to view emitted light from the opposite side to the electron source 2 through an inorganic transparent substrate (glass substrate 7), and phosphor ceramic pieces 6R, 6G, and 6B having a size corresponding to pixels are arranged. Thus, the phosphor layer 6 is formed.

  In the image display device 1 shown in FIG. 1, a field emission electron source 2 for emitting electrons collides with a rear plate 4 provided on a glass substrate 3 and electrons emitted from the electron source 2. Thus, the phosphor layer 6 that emits light is disposed to face the face plate 8 provided on the glass substrate 7 with an interval of several mm. The air gap between the rear plate 4 and the face plate 8 is kept airtight by side walls (not shown) provided around the rear plate 4 and the face plate 8, and is maintained in a vacuum state. The

  An aluminum layer 9 is deposited as a metal back layer on a surface portion of the phosphor layer 6 provided on the face plate 8 and facing the rear plate 4. The phosphor layer 6 and the aluminum layer 9 constitute a phosphor screen. Yes.

  In the phosphor layer 6, phosphor ceramic pieces 6 R, 6 G, and 6 B of each pixel that emits red, green, and blue light are respectively arranged and fixed at the pixel formation position on the glass substrate 7. A light reflecting layer 11 is provided between the pieces. The light reflecting material 11 can improve the light emission output (luminance) in the phosphor layer 6. Note that by providing a black matrix instead of the light reflecting material 11, the contrast of the image displayed by the phosphor layer 6 can be improved.

  The thickness of the phosphor ceramic pieces 6R, 6G, 6B is preferably 0.02 to 0.5 mm. The reason why the thickness of the phosphor ceramic pieces 6R, 6G, 6B is in the range of 0.02 to 0.5 mm is that if the thickness is smaller than this range, the mechanical strength of the phosphor ceramic pieces 6R, 6G, 6B is reduced and manufactured. This is because the handling of the time becomes difficult, and if it is thicker than this range, the light emission output decreases.

  The aluminum layer is formed for the purpose of increasing the light output by reflecting the light emitted backward (electron beam incident side) and preventing the electrification as in the case of CRT. It is also possible to do. The thickness of the aluminum layer is preferably such that there is little hindrance to the incidence of the electron beam and sufficient reflectivity for light emission, and is set to 50 to 100 nm in this embodiment. The aluminum layer 9 prevents the phosphor ceramic pieces 6R, 6G, 6B from falling off.

The phosphors constituting the phosphor ceramic pieces 6R, 6G, and 6B are blue light emitting silver activated zinc sulfide (ZnS: Ag, Al), known as a color CRT phosphor, and green light emitting copper activated Zinc sulfide (ZnS: Cu, Al), red-emitting europium activated yttrium oxysulfide (Y ₂ O ₂ S: Eu), rare earth phosphor europium activated yttrium oxide (Y ₂ O ₃ : Eu), with terbium Phosphors known for electron beam excitation such as activated yttrium silicate (Y ₂ SiO ₅ : Tb) and cerium-activated yttrium silicate (Y ₂ SiO ₅ : Ce) can be used. A ceramic other than a cubic material and having a low porosity is preferable in terms of improving the light emission output. That is, a part of the light emitted near the surface facing the electron source 2 of the phosphor ceramic is totally reflected inside the phosphor ceramic and leaks in the lateral direction where the black matrix is provided, thereby reducing the light emission output. However, if a material having a crystal system other than the cubic system is used, this lateral leakage can be reduced by light scattering. As an example of a preferable phosphor material, the general formula is represented by Ln ₂ O ₂ S: R (where Ln is at least one element selected from the group consisting of Y, La, Gd, and Lu, and R is a rare earth element). Rare earth oxysulfide phosphors or hexagonal zinc sulfide phosphors. More preferably, Eu-activated rare earth oxysulfide for red light emission, Tb or Pr-activated rare earth oxysulfide for green light emission, blue, for the purpose of obtaining sufficient luminance and a clear emission color. For light emission, Tm-activated rare earth oxysulfide or Ag-activated hexagonal zinc sulfide is suitable.

  The phosphor ceramic pieces 6R, 6G, and 6B can be manufactured by a hot isostatic pressing method. The hot isostatic pressing method is a method of obtaining phosphor ceramics by encapsulating phosphor powder in a metal capsule and raising the temperature and raising the pressure at about several hundreds of degrees Celsius and several tens of MPa. The manufacturing method of the phosphor ceramic pieces 6R, 6G, and 6B is not limited to the hot isostatic pressing method, and other manufacturing methods such as a hot pressing method in which a phosphor powder is pressed from above and below are used. it can.

  The phosphor ceramic produced by the hot isostatic pressing method is diced and polished to obtain a phosphor ceramic piece having a size corresponding to the pixel and a predetermined thickness.

  As a method of fixing the phosphor ceramic pieces 6R, 6G, 6B thus produced after being placed at a predetermined position on the glass substrate 7, an inorganic substance that can be melted at a low temperature is used as the phosphor ceramic pieces 6R, 6G. , 6B and the glass substrate 7 or around the phosphor ceramic pieces 6R, 6G, 6B and overheating. Specifically, for example, the step of installing the phosphor ceramic pieces 6R, 6G, 6B after applying the frit glass powder on the glass substrate 7, or the water glass or the water solution after the phosphor ceramic pieces 6R, 6G, 6B are installed. This can be achieved by performing a heat treatment after the step of dripping and drying the functional binder solution.

  The light reflecting layer 11 or the black matrix between the pixels can be formed by filling a predetermined substance by printing between the phosphor ceramic pieces 6R, 6G, and 6B. By filling the light reflecting layer 11 or the black matrix, the phosphor ceramic pieces 6R, 6G, and 6B are not easily dropped off.

  The aluminum layer 9 is obtained by forming an organic film layer on the surface of the phosphor ceramic pieces 6R, 6G, 6B fixed on the glass substrate 7, vapor-depositing aluminum, and then removing the organic film by baking.

  In addition, the image display device 1 according to the present embodiment is a field emission type in which the face plate 8 in which the phosphor layer 6 is formed on the transparent glass substrate 7 as described above, and the same pitch as the pixel pitch of the phosphor layer 6. The rear plate 4 provided with the electron source array can be arranged to face each other with a predetermined interval by a spacer, and the inside of the panel is evacuated and sealed with frit glass or the like. In the field emission type electron source 2 provided on the rear plate 4, a transparent cathode electrode 12 is provided on the glass substrate 3, and a triangular pyramid-shaped cathode 13 is placed on the top of the cathode electrode 12. It is scattered at positions corresponding to the pixel positions so as to face the phosphor layer 6. Between each cathode 13, a gate electrode 15 is provided on the cathode electrode 12 via an insulating material 14.

  At the cathode 13, electrons are generated due to a potential difference with the gate electrode 15. The electrons are emitted from the cathode 13 by field emission, accelerated by an acceleration voltage applied to the aluminum layer 9 of the face plate 8, and collide with the fluorescent ceramic pieces 6R, 6G, or 6B facing the cathode 13. Thereby, the fluorescent ceramic pieces 6R, 6G, and 6B can emit light.

  As shown in FIG. 2, the phosphor screen is manufactured by first producing phosphor ceramics by hot isostatic pressing (step S1), and dicing and polishing the produced phosphor ceramics to obtain phosphors. The ceramic is divided into phosphor ceramic pieces 6R, 6G, and 6B having a size corresponding to the pixel (step S2). Then, after the produced phosphor ceramic pieces 6R, 6G, and 6B are fixed on the glass substrate 7 with an inorganic substance that melts at a low temperature (step S3), each phosphor ceramic piece fixed on the glass substrate 7 is used. The material of the light reflection layer 11 (or black matrix) is filled between 6R, 6G, and 6B (step S4). Then, an aluminum layer (metal back layer) 9 is deposited on the surfaces of the phosphor ceramic pieces 6R, 6G, 6B and the light reflecting layer 11 (or black matrix) (step S5). In this way, a phosphor screen can be manufactured.

(Comparative Example 1)
Y ₂ O ₂ S: Eu phosphor powder as red and ZnS: Cu as green by a method in which slurry coating, exposure, and development are sequentially repeated on a glass substrate, which is generally performed when forming a CRT phosphor screen. A pattern of Al phosphor powder, cubic ZnS: Ag, Al phosphor powder as blue was formed. At this time, the phosphor layer has a thickness of about 20 μm, the pixel pitch is 0.6 mm in the vertical direction, 0.28 mm in the horizontal direction, and a stripe pattern in which red, green, and blue are sequentially repeated in the horizontal direction. After this, the phosphor screen was impregnated with water, sprayed with lacquer to form an organic film, and after drying, 100 nm thick aluminum was vacuum evaporated and baked at 450 ° C. to form an aluminum layer. The phosphor screen of Example 1 was produced.

Next, a rear plate in which an array of field emission electron sources is formed at a position facing each pixel on the phosphor screen is manufactured and sealed with a spacer facing the phosphor screen of Comparative Example 1 at a distance of 2 mm, A 10-inch diagonal display was produced. Time to apply 10 kV acceleration voltage to the phosphor screen (anode), set the driving conditions of the electron source array so that the initial luminance of the screen is 500 cd / m ^2, and decrease the phosphor luminous efficiency to 50% Was 2000 hours. After that, when the acceleration voltage was increased by 1 kV, discharge did not occur even if the acceleration voltage was maintained at 12 kV for 1 hour, but discharge was generated when driving at 13 kV for about 10 minutes.

(Comparative Example 2)
The phosphor screen of Comparative Example 2 was produced in the same manner as Comparative Example 1 except that Y ₂ O ₂ S: Tb phosphor powder was used as green and La ₂ O ₂ S: Tm phosphor powder was used as blue. Next, a 10-inch diagonal display was produced in the same manner as in Comparative Example 1, and the lifetime was evaluated by setting the driving conditions of the electron source array so that the initial luminance of the screen was 500 cd / m ² . The time required for the phosphor luminous efficiency to drop to 50% was 9000 hours. Further, when the acceleration voltage was increased by 1 kV thereafter, discharge was generated when driving at 12 kV for about 30 minutes.

Example 1
Ceramics of Y ₂ O ₂ S: Eu, Y ₂ O ₂ S: Tb, and La ₂ O ₂ S: Tm were produced by hot isostatic pressing using a metal capsule, and 0.5 mm in length from each ceramic A phosphor ceramic piece having a width of 0.25 mm and a thickness of 0.05 mm was cut out. The phosphor ceramic pieces of Y ₂ O ₂ S: Eu, Y ₂ O ₂ S: Tb, and La ₂ O ₂ S: Tm are sequentially repeated in the horizontal direction at a pitch of 0.6 mm in length and 0.28 mm in width. Then, a water glass aqueous solution was dropped, and after standing and drying, each piece of ceramic was fixed by baking at 450 ° C. Next, white titanium oxide powder was filled between ceramic pieces by a printing method. Further, in the same manner as in Comparative Example 1, after forming an organic film with lacquer, aluminum was vapor-deposited, followed by baking to form an aluminum layer having a thickness of 100 nm, and the phosphor screen of Example 1 was produced. This was opposed to a rear plate on which the same electron source array as that in Comparative Example 1 was formed at a distance of 2 mm and sealed to produce a 10-inch diagonal display. When the lifetime was evaluated by setting the driving conditions of the electron source array so that the initial luminance of the screen would be 500 cd / m ² , the time until the phosphor luminous efficiency decreased to 50% was 32000 hours. Significant improvement was seen compared to Examples 1 and 2. Further, when the acceleration voltage was increased by 1 kV thereafter, no discharge was generated even when driving was performed at 13 kV for 1 hour, and it was confirmed that the discharge was hardly generated.

(Example 2)
The phosphor screen of Example 2 was produced in the same manner as in Example 1 except that Gd 2 O 2 S: Pr phosphor ceramic pieces were used as green and hexagonal ZnS: Ag, Al phosphor ceramic pieces were used as blue. Next, a 10-inch diagonal display was produced in the same manner as in Comparative Example 1, and the lifetime was evaluated by setting the driving conditions of the electron source array so that the initial luminance of the screen was 500 cd / m ² . The time required for the phosphor luminous efficiency to drop to 50% was 22,000 hours. Even in this case, a significant improvement was seen compared to Comparative Examples 1 and 2. Further, when the acceleration voltage was increased by 1 kV thereafter, no discharge was generated even when driving was performed at 13 kV for 1 hour, and it was confirmed that the discharge was hardly generated.

(Effect of embodiment)
In the thin field emission type image display device 1 in which the distance between the rear plate 4 provided with the electron source 2 and the face plate 8 provided with the phosphor layer 6 is several mm, it is provided between the cathode and the phosphor layer side. Is smaller than that of the CRT, the acceleration voltage of the electron beam for causing the phosphor on the screen to emit light is lower than that of the CRT, and conversely, the current density thereof is high. The phosphor screen coated with body powder is likely to be deteriorated due to collision of electron beams. In particular, in a low energy cathode ray display with a low acceleration voltage such as a field emission type image display device, the screen energy and energy efficiency of the screen are reduced. Must be applied to the phosphor at a high density. Further, in the thin field emission image display device 1 in which the distance between the rear plate 4 provided with the electron source 2 and the face plate 8 provided with the phosphor layer 6 is several mm, the acceleration voltage is used for the purpose of obtaining high luminance. Is increased, discharge tends to occur on the phosphor screen coated with the conventional phosphor powder.

  In the image display device 1 according to the present embodiment, the phosphor screen is formed by arranging the phosphor ceramic pieces 6R, 6G, and 6B, so that the phosphor screen (phosphor ceramics 6R, 6G, and 6B) due to the collision of the electron beams. Can be reduced and the occurrence of discharge can be suppressed.

  Therefore, it is possible to realize a phosphor screen that is less deteriorated and generates less discharge even when driven at high brightness, and a field emission type image display device incorporating the phosphor screen.

(Other embodiments)
In the above-described embodiment, the case where the phosphor screen composed of the phosphor ceramic pieces 6R, 6G, and 6B is applied to the image display device 1 having the field emission type electron source 2 has been described. It can also be applied to an image display device called SED). In this case, an element called surface conduction electron emission (SCE: surface conduction electron emitter) having a crack-like electron emission portion in a conductive thin film is provided as an electron source, and FIG. A phosphor layer in which the above-described phosphor ceramic pieces are arranged may be provided.

It is sectional drawing which shows the image display apparatus which concerns on embodiment. It is a flowchart which shows the manufacturing process of the fluorescent screen of the image display apparatus of a figure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Electron source 3, 7 Glass substrate 4 Rear plate 6 Phosphor layer 6R, 6G, 6B Phosphor ceramic piece 8 Rear plate 9 Aluminum layer 11 Light reflecting material 12 Cathode electrode 13 Cathode 14 Insulating material 15 Gate electrode

Claims (5)

Phosphor ceramic pieces having a size corresponding to pixels arranged on an inorganic transparent substrate;
A metal back layer formed on the surface of the phosphor ceramic piece;
A phosphor screen characterized by comprising:   The phosphor screen according to claim 1, wherein the phosphor ceramic piece is made of a material other than a cubic system. The phosphor ceramic piece is a rare earth oxysulfide represented by Ln ₂ O ₂ S: R (where Ln is at least one element selected from the group consisting of Y, La, Gd, and Lu, and R is a rare earth element). The phosphor screen according to claim 1, wherein the phosphor screen is a phosphor.   The phosphor ceramic pieces are Eu-activated rare earth oxysulfides for red light emitting pixels, Tb or Pr activated rare earth oxysulfides for green light emitting pixels, and Tm activated rare earth oxysulfides for blue light emitting pixels. 4. The phosphor screen according to claim 3, wherein the phosphor screen is Ag-activated hexagonal zinc sulfide. A face plate in which the phosphor screen according to any one of claims 1 to 4 is incorporated;
A rear plate disposed facing the face plate and having a plurality of electron sources that emit electrons to each pixel of the phosphor screen;
An image display device comprising:

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