JPH05156246A - Far infrared emitting phosphor for cathode-ray tube - Google Patents

Abstract

PURPOSE: To provide the title novel phosphor which has a spectral output matched with the response of α-silicon in use in combination with a liquid crystal valve containing a photosensitive layer comprising α-silicon as a phosphor for the cathode ray tube of a liquid crystal display element.

CONSTITUTION: There is provided a phosphor represented by the formula (wherein x is 0-5; y is 0-3; and A is Cr, Fe, Co, Ni, Ti or the like). The lightest phosphor is desirably Y₃Al₅O₁₂:Cr. The phosphor having the shortest degradation time is desirably Gd₃Ga₅O₁₂:Cr, and the most lightest and shortest degradation time phosphor is desirably Y₃Al₂Ga₃O₁₂:Cr. For example, the phosphor can be obtained by mixing oxides of Y, Al, Ga and Cr with each other, grinding the mixture with a ball mill, pulverizing and drying the obtained homogeneous mixture and firing the dried mixture at 1,500-1,600°C in an oxidizing atmosphere.

COPYRIGHT: (C)1993,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor used in a cathode ray tube for a liquid crystal display device, and more particularly to a new phosphor having a yttrium aluminum garnet structure.

Liquid crystal light valve manufactured by Hughes (LCL
The phosphor used for directing to V) amorphous silicon has the following conditions: spectral output that matches the response of amorphous silicon (α-Si) as much as possible, maximum radiant energy output in the spectral range of interest, 100%. To less than about 10 ms, measured to levels of 10% to 10%, an average particle size suitable for high resolution of less than about 6 μm, and high resistance to decay caused by either heat or lifetime. I won't.

The spectral responsivity of α-silicon used in LCLV has a peak at about 740 nm. Therefore, for optimum sensitivity, the incident light used to activate the α-silicon photosensitive layer should match the response curve as closely as possible.

Many phosphors have been investigated in an attempt to find phosphors with suitable properties in terms of spectral emission, decay time, efficiency and small particle size. Such phosphors include aluminum oxide: Cr, cadmium sulfide: Ag,
Lead cadmium sulfide: Ag, lead Mn phosphate, yttrium oxysulfide: Eu, yttrium aluminum oxide: E
Including u etc.

An existing far-infrared light-emitting phosphor used for a fluorescent lamp (here, "far-infrared" means 600 to 80).
(Meaning 0 nm) indicated a good match for α-silicon responsiveness. This far infrared emitting phosphor is
Iron-activated lithium oxide aluminum (LiAlO _2: F
e). In commercially available materials, the iron concentration is about 0.5.
%. However, such a phosphor is a CRT
Has a disintegration time of about 30 milliseconds, which is longer than acceptable.

Yttrium aluminum garnet (YAG) phosphors are well known in the art.
The yttrium aluminum garnet (YAG) phosphor has various activators such as terbium, cerium and europium.

In YAG: Eu, the energy is 59
Distributed between the 1, 608, 630 and 710 nm lines,
It has low peaks at about 649 and 692 nm. Due to this spectral output, this phosphor does not efficiently light the light valve.

No commercial phosphors have met the requirements of α-silicon LCVCs.

According to the present invention, a new type of phosphor having a yttrium aluminum garnet crystal structure is provided. The general formula of the phosphor of the present invention is Y _3-y Gd _y Al _5-x
Ga _x O ₁₂ : A, where x is in the range of 0 to 5, y is in the range of 0 to 3, and A is chromium, iron, vanadium, neodymium, dysprosium, cobalt, nickel, titanium. , And combinations thereof.

Phosphors having the above general formula exhibit bespoke changes in spectral output, emission and persistence characteristics within the requirements set by the requirements of the α-silicon photosensitive layer in liquid crystal light valves.

The liquid crystal light valve (LCLV) is, for example, SID, International Symposium, Digest of Technica.
l Papers (International Symposium Industrial Paper Digest) 1
Vol. 11, 327-328 (1990), R. D. Sterling et al., "Video Speed Liquid Crystal Light Valve With Amorphous Silicon Photoconductor". Figure 1 is taken from this document and shows the basic LCLV
FIG. 3 is a diagram showing a projector 10. The LCLV projector includes a cathode ray tube (CRT) 12. The cathode ray tube 12 provides an input image that is combined with a liquid crystal light valve 14 typically through a fused optical fiber faceplate (not shown). The xenon arc lamp 16 provides the output light. This output light is L
Before reaching the CLV 14, it is filtered by a UV filter 18 and linearly polarized by a pre-polarization filter 20. Next, the image passes through a polarizing mirror 22 and a prism window 24, and then passes through a light projecting lens 26, where it is projected on a screen (not shown).

The projectors described above are LCVC and CR.
It is an example of an apparatus that employs a combination of T. Also, LC
Other combinations of VC and CRT are also known. Such combinations are well known to those skilled in the art, but their CRTs do not use the phosphors of the present invention.

The LCLV, as is well known, uses a hydrogenated amorphous silicon photoconductor (α-Si: H), as shown in the above mentioned references. The spectral response of the α-Si photoconductor is shown in FIG. In order for the phosphor to perform energy coupling efficiently, it is necessary to match this curve as closely as possible.

The phosphor composition of the present invention has the general formula Y _3-y G
d _y Al _5-x Ga _x O ₁₂ : A, where x is in the range 0 to 5, y is in the range 0 to 3, and A is chromium, iron, vanadium, neodymium, It is selected from the group consisting of dysprosium, cobalt, nickel, titanium, and combinations thereof.

Preferably, at least one of chromium, neodymium and iron is used. Chromium is most preferably used, especially in the range of about 0.33 to 2%. Outside this range, the write output is reduced and unacceptable.

The preferred composition depends especially on the desired properties. For example, the brightest composition (highest relative power) is
Chrome Activated Yttrium Aluminum Garnet, Y ₃
Al ₅ O ₁₂ : Cr (YAG: Cr) provides the shortest decay time with chromium activated gadolinium gallium garnet Gd ₃ Ga ₅ O ₁₂ : Cr (GGG: Cr). The most reasonable composition for obtaining the brightest and shortest disintegration time is Y ₃ Al ₂ Ga ₃ O ₁₂ : Cr.
Is. The results are shown below.

Composition Relative Output Decay YAG: Cr 100 5-6 ms GGG: Cr 45 1 Y ₃ Al ₂ Ga ₃ O ₁₂ : Cr 76 2 The production of the garnet-based phosphor of the present invention is industrially used. Follow normal process. The starting material consists of oxides of each component. These are mixed in stoichiometric ratio and ground in a ball mill to produce a well blended homogeneous mixture.
After pulverizing and drying the reactants, it is usually calcined in an oxidizing atmosphere such as air at about 1500 to 1600 ° C. for about 2 to 8 hours in a one step process.

Further, this oxide is fired in a two-step process in which it is fired in an oxidizing atmosphere such as air at about 1500 ° C. to 1600 ° C. for 2 to 8 hours and then again at about 1200 for 1 to 4 hours. can do.

Alternatively, about 1200 ° C. for 1 to 4 hours, about 1550 ° C. for 1 to 4 hours, and 1590 ° C.
You may use the three-step process which performs baking for 1 to 4 hours.

These procedures are well known and do not form a feature of the present invention. The luminescent properties of the phosphor are improved by reducing the particle size and therefore have to be adapted to the production of particles with an average size of less than about 6 μm.

The sol-gel method can also be used for the production of the phosphor. The starting components in this case consist of either nitrides or chlorides of Y, Al and Cr. These are dissolved in deionized water in a stoichiometric ratio. The next step is to precipitate all the metal hydroxides by adding ammonium hydroxide solution in excess of the stoichiometrically required amount. After suitable aging and stabilization of the precipitate, it is filtered, washed thoroughly and dried. At this time, in order to obtain a desired phosphor, the above-mentioned firing operation can be used as a starting material. Such steps are also known and do not form part of the features of the method of the invention.

Alternatively, the starting material may consist of stoichiometric nitrides of yttrium, gadolinium, aluminum and gallium. These dissolve in the aqueous solution and the hydroxide is precipitated by ammonium hydroxide. After washing, the desired percentage of activator hydroxide is ball milled into the material. After pulverization with the ball mill as described above, the mixture is dried and calcined under the same conditions as above. Such steps are also known and do not form part of the features of the method of the invention.

Alternatively, starting with the yttrium, gadolinium, aluminum and gallium nitrides and activators, the hydroxides are precipitated with the above ammonium hydroxide and treated as described above.

A method for producing a garnet-containing phosphor based on the idea of the present invention will now be described. This two-step method itself is not considered novel and does not form part of the features of the present invention.

If it is desired to make 10 g of the phosphor starting with the hydroxide, the required amount (see formulation below) of the oxide is placed in a 2 ounce ball mill along with calcined alumina spheres of approximately 9 mm particle size. Add 15 ml deionized water, close mill and place on roller. As is well known, making large quantities of phosphors requires proper scale-up.

During rolling, the oxide is intimately mixed to reduce its size somewhat and after 2 hours of rolling the mill is removed from the rolls and the contents are thrown into a wash container.
Rinse water is added to the main sediment from the mill. After drying in an oven at about 110 ° C., the powder is sieved through a 70 stainless steel mesh. The sieved product is placed in a sintered alumina boat and placed in a furnace at 400 ° C. After raising the temperature to 1200 ° C. and maintaining it for 2 hours, the temperature is lowered to 400 ° C. and the boat is removed from the furnace. The furnace atmosphere during firing is usually air. The material is screened again and the particle size is measured. Then, the material was returned to the furnace, the temperature was raised to 1600 ° C., and the state was maintained for 2 hours. The furnace was cooled to 400 ° C and the boat was removed. The final material is crushed with a pestle in a mortar, sieved, particle size measured and prepared for use.

[0027]

EXAMPLES A number of compositions were prepared using the method described above. Table 1 shows the effect of some compositions on various properties.
Shown in. The relative power is determined by measuring its radiance with a spectrophotometer in the wavelength range 600 to 800 nm. This data is then converted to relative output by dividing each value by the maximum radiance value. The disintegration time was measured in milliseconds. The firing temperature was 1200 ° C and then 1600 ° C. The spectral distribution as a function of composition is shown in FIGS.

Table 1. Effect of composition on properties Y Gd Al Ga Cr Relative output decay time diagram at% ms 2.97 5 − − 1 100 5-6 3 2.97 4 1 1 49 2 4 2.97 3 2 1 48 2 5 2.97 2 3 1 76 2 6 2.97 1 4 1 71 2 7 2.97 5 5 1 60 2 8 −− 2.97 −− 5 1 45 1-1 1/2 9 −− 2.97 5 −− 1 63 35 10 1.485 1.5 2.5 2.5 1 63 2 --Characteristics Table 2 shows the effect of firing temperature on the. In all cases, the firing time is 2 hours at that temperature. The effect of firing temperature on the spectral distribution is shown in FIGS.

Table 2. Effect of firing temperature on characteristics Y Gd Al Ga Cr Relative output Firing temperature diagram at% ℃ 2.97 −− 5 −− 1 18 800 11 2.97 −− 5 −− 1 62 800/1200 12 2.97 −− 5 −− 1 100 800 / 1200/1600 13 −− 2.97 −− 5 1 35 1200 14 −− 2.97 −− 5 1 64 1200/1600 15 Table 3 shows the effects of various additive compositions on the relative output. The spectral distributions of two of these compositions are shown in FIGS. 16 and 17.

Table 3. Effect of Other Compositions on Relative Power Composition Burning Temperature Relative Power Diagram Y _2.97 Al ₅ O ₁₂ : 1% Cr 1600-2 hours 96 --Y _2.88 Al ₅ O ₁₂ : 0.5% Cr 1600-2 hours 100- Y _2.94 Al ₅ O ₁₂ : 1% Cr, 1% Nd 1500-4 hours 87 16 Y _2.97 Al ₅ O ₁₂ : 1% Nd 1500-5 hours 8 17 Fluorescence having the preferred composition and prepared as described above. The particle size distribution of the body is shown in Figures 18 and 19. FIG. 18 shows GGG.
And with 1.0% Cr activator. The average particle size is 6.31 μm, 10% of the particles
Is less than 1.32 μm and 10% of the particles are 21.1
Greater than 5 μm. FIG. 19 is for YAG,
This is the case with 0.5% Cr activator. The average particle size is 6.54 μm and 10% of the particles are 1.76 μm
10% of the particles are above 14.12 μm.

Thus, substantially Y _3-y Gd _y Al
_5-x Ga _x O ₁₂ : A, where x is 0 to 5
, Y is in the range of 0 to 3, and A is chromium, iron, vanadium, neodymium, dysprosium,
A far-infrared emitting phosphor selected from the group consisting of cobalt, nickel, titanium, and combinations thereof has been disclosed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a liquid crystal light valve projector that can use the phosphor of the present invention.

FIG. 2 is a graph plotting the response of an amorphous silicon (α-Si) photoconductor on the coordinates of normalized radiance and wavelength (nm).

FIG. 3 shows the action of the composition on the coordinate of normalized radiance and wavelength (nm) as Y _3-y Gd _y Al _5-x Ga.
_x O _12: Cr (where, y = 0 and x = 0) graph plotting the optical output of the.

FIG. 4 shows the action of the composition on the coordinate of normalized radiance and wavelength (nm) as Y _3-y Gd _y Al _5-x Ga.
_x O _12: Cr (where, y = 0 and x = 1) graph plotting the optical output of the.

FIG. 5 shows the effect of the composition on the coordinates of normalized radiance and wavelength (nm), Y _3-y Gd _y Al _5-x Ga
_x O _12: Cr (where, y = 0 and x = 2) graph plotting the optical output of the.

FIG. 6 shows the effect of the composition on the normalized radiance and wavelength (nm) coordinates as Y _3-y Gd _y Al _5-x Ga.
_x O _12: Cr (where, y = 0 and x = 3) graph plotting the optical output of the.

FIG. 7 shows Y _3-y Gd _y Al _5-x Ga as the effect of the composition on the coordinate of normalized radiance and wavelength (nm).
_x O _12: Cr (where, y = 0 and x = 4) graph plotting the optical output of the.

FIG. 8 shows Y _3-y Gd _y Al _5-x Ga as a function of the composition on the coordinate of normalized radiance and wavelength (nm).
_x O _12: Cr (where, y = 0 and x = 5) graph plotting the optical output of the.

FIG. 9 shows the effect of the composition on the coordinates of normalized radiance and wavelength (nm), Y _3-y Gd _y Al _5-x Ga
_x O _12: Cr (where, y = 3 and x = 5) graph plotting the optical output of the.

FIG. 10: Y _3-y Gd _y Al _5-x G as a function of composition on the coordinates of normalized radiance and wavelength (nm).
a _x O _12: Cr (where, y = 3 and x = 0) graph plotting the optical output of the.

FIG. 11 shows Y _3-y Gd _y Al _5-x as a function of manufacturing conditions on the coordinates of normalized radiance and wavelength (nm).
Ga _x O _12: Cr (where, y = 0 and x = 0) graph plotting the optical output of the.

FIG. 12: Y _3-y Gd _y Al _5-x as a function of manufacturing conditions on the coordinate of normalized radiance and wavelength (nm)
Ga _x O _12: Cr (where, y = 0 and x = 0) graph plotting the optical output of the.

FIG. 13: Y _3-y Gd _y Al _5-x as a function of manufacturing conditions on the coordinates of normalized radiance and wavelength (nm)
Ga _x O _12: Cr (where, y = 0 and x = 0) graph plotting the optical output of the.

FIG. 14 shows Y _3-y Gd _y Al _5-x as a function of manufacturing conditions on the coordinate of normalized radiance and wavelength (nm).
Ga _x O _12: Cr (where, y = 3 and x = 5) graph plotting the optical output of the.

FIG. 15 shows Y _3-y Gd _y Al _5-x as a function of manufacturing conditions on the coordinate of normalized radiance and wavelength (nm).
Ga _x O _12: Cr (where, y = 3 and x = 5) graph plotting the optical output of the.

FIG. 16: Y _2.94 Al ₅ O as a function of other compositions on the normalized radiance and wavelength (nm) coordinates.
_The graph which plotted the optical output of ₁₂ : 1% Cr, 1% Nd.

FIG. 17: Y _2.97 Al ₅ O as a function of other compositions on the normalized radiance and wavelength (nm) coordinates
_The graph which plotted the light output of ₁₂ : 1% Nd.

FIG. 18 is a graph diagram in which the particle size distribution of an example of the phosphor of the present invention is plotted on the coordinates of percentage and particle size (μm).

FIG. 19 is a graph diagram in which the particle size distribution of an example of the phosphor of the present invention is plotted on the coordinates of percentage and particle size (μm).

[Explanation of symbols]

10 ... LCLV projector, 12 ... Cathode ray tube, 14
… Liquid crystal light valve, 16… Xenon arc lamp, 1
8 ... UV filter, 20 ... Pre-polarization filter, 22
... Polarizing mirror, 24 ... Prism window, 26 ... Projection lens

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Mary A. Lemoin, USA 92054, California 92054, Oceanside, Marshall Street 1421 (72) Inventor Kenneth Earl Hesse United States, California 92026, Escondido, LA・ Paloma Glen 1221

Claims (6)

[Claims] 1. A combination comprising a liquid crystal light valve including a photosensitive layer consisting essentially of α-silicon, and a far-infrared emitting phosphor functionally combined with the α-silicon, wherein the phosphor is , Substantially the general formula Y _3-y Gd
_y Al _5-x Ga _x O ₁₂ : A, wherein x is in the range of 0 to 5, y is in the range of 0 to 3, and A is chromium, iron, vanadium, neodymium, dysprosium A combination selected from the group consisting of, cobalt, nickel, titanium, and combinations thereof. 2. A method for efficiently coupling energy from light emitted from a red phosphor to a hydrogenated amorphous silicon photoconductor, wherein the red phosphor is substantially represented by the general formula Y _3-y. Gd _y Al _5-x Ga _x O ₁₂ , where x is in the range 0 to 5 and y is 0.
To 3 and A is selected from the group consisting of chromium and neodymium, said chromium being 0.33 to 2 at.
%, And said neodymium comprises providing a compound having a value of about 1 at%. 3. A screen comprising a red phosphor,
An improved method of manufacturing a cathode ray tube for efficiently coupling energy from light emitted from the red phosphor to a hydrogenated amorphous silicon photoconductor, wherein the red phosphor is substantially General formula Y _3-y Gd
_y Al _5-x Ga _x O ₁₂ , where x is in the range 0 to 5, y is in the range 0 to 3, and A
Is selected from the group consisting of chromium and neodymium, said chromium having a value in the range of 0.33 to 2 at%, and said neodymium providing a compound having a value of about 1 at%. how to. 4. The invention according to claim 1, 2 or 3, wherein x = 0, y = 0 and A in the general formula are chromium. 5. The invention according to claim 1, 2 or 3, wherein x = 5, y = 3 and A in the general formula are chromium. 6. The invention according to claim 1, 2 or 3, wherein x = 2, y = 0 and A in the general formula are chromium.