Patent Application
20050009434
1. Field of the Invention
The present invention relates to a method for manufacturing an image display device having a pair of substrates arranged opposite each other, the image display device, and a TV apparatus.
2. Description of the Related Art
An image display device, which is provided with a plurality of plate-shaped spacers or columnar spacers arranged between a pair of substrates arranged opposite each other, is known in the related art (as referred to JP-A-07-302560 or JP-A-2000-260353, for example).
In
By using the drive method and the drive circuit disclosed in JP-A-2003-173159, for example, electron beams are emitted to irradiate fluorescent elements by matrix-arranged electron emitting devices so that images are displayed.
With a variation in the heights of the spacers disposed in the vacuum container, the spacers and the substrates may vary in their contact state or may increase in their non-contact portions. Thus, the vacuum container has its mechanical strength lowered. With the variation in the spacer heights, moreover, many point contacts occur between the spacers and the substrates. These point contacts are desired to be as few as possible, because they cause discharges.
The method of the related art for manufacturing the image display device has endeavored to homogenize the heights of the individual portions of each spacer and to suppress the variation in the heights of the spacers. An image display device having less deformation as the vacuum container has been realized by those endeavors. However, it is followed by technical difficulties to mass-produce the spacers having such mechanical precision stably. Moreover, a number of spacers, if any, dissatisfying predetermined standards will cause a rise in the resultant cost for the image display device.
An object of the invention is to stabilize a mechanical strength without demanding the spacers for a high mechanical precision.
Another object of the invention is to suppress discharges, as might otherwise occur between the spacers and the substrates, without demanding the spacers for the high mechanical precision.
Still another object of the invention is to lower the cost while keeping a high quality.
In order to achieve the objects thus specified, the following constructions are adopted according to the invention.
According to an aspect of the invention, there is provided a method for manufacturing an image display device including: a rear plate having a plurality of electron emitting devices arranged thereon; a face plate arranged opposite the rear plate and having image forming members arranged for forming images when irradiated with electron beams emitted from the electron emitting devices; and a plurality of spacers arranged between the face plate and the rear plate, comprising:
Here: the spacers are plate-shaped spacers;
On the other hand: the spacers are plate-shaped spacers;
On the other hand: the spacers are plate-shaped spacers;
Moreover, the predetermined threshold value is determined depending on the characteristics of at least either of the rear plate and the face plate.
On the other hand: the spacers are columnar spacers; and
Moreover, the arranging step arranges the spacers between the face plate and the rear plate sequentially in a diagonal direction in the order from the end portion according to the magnitudes of the measured values.
According to another aspect of the invention, there is provided an image display device comprising:
According to still another aspect of the invention, there is provided a TV apparatus comprising:
Embodiments of the invention will be described in detail in the following.
[First Embodiment]
In this embodiment, plate-shaped spacers are used as support members.
Here, the plate-shaped spacers 4S can be prepared by a heating drawing. According to this heating drawing, it is possible (as referred to JP-A-2000-311608, for example) to easily prepare the plate-shaped spacers 4S which can suppress scattering of secondary electrons.
This embodiment is provided with measurement means for measuring the heights H (as referred to
In the case of the example illustrated in
Here in this embodiment, the measured values of the heights of the spacers obtained by the measurement means are used so they are arranged in the sequential order from the larger one.
According to this embodiment, it was possible to manufacture an image display device which had a sectional shape controlled into a wedge shape reflecting the spacer height order. As a result, the maximum value of variation in the heights between the adjoining spacers could be reduced from Δ=0.002 mm to Δ=0.001 mm. Thus, it was possible to reduce the variation in the height between the adjoining spacers. Accordingly, the variation in the contact state between the spacer and the substrate (i.e., the rear plate 1 or the face plate 2) could be suppressed to suppress the occurrence of portions failing to contact with each other. Thus, the mechanical strength of the vacuum container could be stabilized without any strict management of the mechanical precision of the spacers. Moreover, the mechanical precision did not need to be strictly managed, but the number of spacers, which might otherwise have failed to satisfy the standards and be discarded, could be reduced to lower the cost. It was further possible to reduce the point contacts, as might otherwise have caused discharges, between the spacers and the substrates.
Here will be briefly described how to manufacture the image display device.
First of all, the rear plate 1 carrying electron emitting devices (although not shown) is set on a hot plate with its electron emitting devices being directed upward. Then, spacers 4 are arranged on the rear plate 1. At this time, the spacers 4 are arranged on the basis of the measured height values H, as described hereinbefore.
In case the spacers 4 are to be adhered to the side of the rear plate 1, frit glass is applied beforehand with a dispenser to at least portions of the positions, at which the spacers 4 are to be arranged. Then, the spacers 4 are arranged on the frit glass with a dedicated jig and are then heated so that they are adhered to the rear plate 1. Here, the positions, to which the frit glass is applied, can be only partially of the non-image areas of the faces of the substrate, with which the spacers 4 are to contact. Moreover, the frit glass may be applied to only one-side faces (as located on the side of the rear plate 1 or the face plate 2) or to both-side faces (as located on both the side of the rear plate 1 and the side of the face plate 2) of the spacers 4.
Next, the frame 3, in which the frit glass has been applied in advance to the portions to be contacted by the rear plate 1 and the portions to be contacted by the face plate 2, is set on the rear plate 1. Moreover, the face plate 2 carrying fluorescent elements (although not shown) is so positioned and fixed that the fluorescent elements may confront the electron emitting devices. Moreover, a hot plate is placed on the assembly and is heated to the adhering temperature of the frit glass while being loaded. After this, the assembly is cooled down to prepare a gas-tight container. After this, the internal air is discharged to a vacuum of about 10×10−6 [Pa] through a discharge tube, for example, by an external vacuum pump. Thus, the vacuum container is manufactured.
In case surface conduction type electron emitting devices are used as the electron emitting devices, they are connected with an external drive circuit so that they are subjected to a forming, an activation and a power running such as a test run before the image display device is manufactured. When an image is to be displayed, the drive voltage is applied to the electron emitting devices, and a voltage as high as 3 KV to 15 KV is applied to an anode electrode arranged on fluorescent elements. As a result, the electron beam emitted from the electron emitting devices are accelerated to irradiate the fluorescent elements. Thus, the image display device functions with the emitting fluorescent elements.
[Second Embodiment]
This embodiment is identical to the first embodiment excepting that the method of measuring the heights of the spacers is different, and the description of its similar construction will be omitted.
In this embodiment, the measured values of the heights of the individual plate-shaped spacers were measured at multiple points in the plate-shaped spacers, and their average value was used. Specifically, the individual plate-shaped spacers were arranged on the basis of the average value.
By arranging the plate-shaped spacers in the sequential order of the larger average values (AVE), the arrangement of the plate-shaped spacers was determined, as illustrated in
[Third Embodiment]
The fundamental construction of the image display device is identical to that of the first embodiment, and the description of a similar construction will be omitted.
Moreover, it is identical to the second embodiment that the heights of the individual plate-shaped spacers are measured at multiple points in the individual plate-shaped spacers so that their average value is determined. Therefore, the description of the identical point will be omitted. In this embodiment, the arrangement of the plate-shaped spacers is controlled by considering the in-plane distribution of the image display device due to the height irregularity with respect to the longitudinal direction of the plate-shaped spacers.
In this embodiment, the plate-shaped spacers are arranged at first on the basis of the average value, and a one-dimensional threshold value curve is then prepared on the basis of the average value. Next, an arbitrary offset value is given to that threshold value curve to determine an upper limit threshold value and a lower limit threshold value. In case the individual measurement points are not between the lower limit threshold value and the upper limit threshold value, the arrangement of the plate-shaped spacers is then adjusted. Thus, this embodiment is different from the first embodiment and the second embodiment in that the arrangement order is changed even after the plate-shaped spacers were once arranged (actually or virtually) in the sequential height order.
At first, the plate-shaped spacers are arranged like the second embodiment according to the average values. Then, an approximate curve is calculated according to a polynomial approximation method, for example, as illustrated in
y=1E−0.5X2+0.0007X+1.577.
On the basis of the approximate curve thus calculated, curves (i.e., a curve for determining the lower limit threshold value and a curve for determining the upper limit threshold value), as illustrated in
In this embodiment, the value ΔZ is set at 0.0047 mm.
Next, the measurement points, at which the measured height values at the individual portions of the plate-shaped spacers are deviated from the range between the lower limit threshold value and the upper limit threshold value, are detected from the aforementioned curves illustrated in
Here, the arrangement of the plate-shaped spacers is further changed in case a measured value is outside of the range between the lower limit threshold value and the upper limit threshold value. Specifically, in case a measured value exceeds the upper limit threshold value, for example, the position of the plate-shaped spacer is interchanged with the position of such one of the adjoining plate-shaped spacers as has a higher average value. In case a measured value falls short of the lower limit threshold value, on the contrary, the position of the plate-shaped spacer is interchanged with the position of such one of the adjoining plate-shaped spacers as has a lower average value. These permutations are repeated till no measured value deviates the range between the lower limit threshold value and the upper limit threshold value.
In the case of the aforementioned example, the arrangements of the spacer 4S3 and the spacer 4S2 are interchanged, for example. As a result, the order of the average values is reversed at the spacer 4S2 and the spacer 4S3, as illustrated in
The in-plane height distribution at this time is illustrated in
According to this embodiment, the variation in the heights between the adjoining spacers could be reduced while considering the height distribution in the longitudinal direction. As a result, the in-plane height distribution of the spacers could be made gentle without any protrusion. Therefore, it was possible to attain effects similar to those of the cases of the foregoing individual embodiments.
[Fourth Embodiment]
This embodiment draws a method for calculating the threshold values at the time of controlling the arrangement of the plate-shaped spacers while considering the characteristics of the substrates, too.
First of all, the calculation method is described with reference to
Plate-shaped spacers SP1, SP2 and SP3 have heights L1, L2 and L3, respectively, in relations of L1<L2<L3. Moreover; the plate-shaped spacers SP1, SP2 and SP3 are individually arrayed at a pitch of length a.
The difference in height between the virtual line joining the crests of SP1 and SP3 and SP2 is designated by ΔH.
As the difference ΔH becomes larger, the spacer SP2 may fail to contact with the substrates constructing the sealed container, when the sealed container arranging the plate-shaped spacers becomes vacuum.
In this embodiment, therefore, the array of the plate-shaped spacers is so selected that the difference ΔH may satisfy the following inequality:
ΔH≦C1·a4/h3.
Here: characters C1 designates a constant depending on the material of the substrates (i.e., the face plate and the rear plate) or the like; letter a designates the interval (or pitch) of the plate-shaped spacers; and letter h designates the thickness of the substrates (i.e., the face plate and the rear plate).
The righthand side designates the value which corresponds to the maximum deformation when the substrates are pressed by the atmospheric pressure.
If the height difference ΔH satisfies the above-specified inequality, it is possible to prepare the vacuum sealed container, in which the oppositely arranged substrates and all the plate-shaped spacers contact.
This embodiment used a glass substrate (PD200 made by Asahi Glass Kabushiki Gaisha) having a thickness of 2.8 mm, for example, for the face plate (or the front plate) and the rear plate (or the back plate).
The plate-shaped spacers were prepared by arranging glass substrates worked to have a width of 0.2 mm, a height of 1.6 mm and a length of 800 mm, at a pitch of 24.6 mm.
At this time, the array of the plate-shaped spacers was so determined from the aforementioned inequality that the height difference ΔH might be 20 microns or less. Thus, it was possible to manufacture the image display device, in which all the plate-shaped spacers contact with the glass substrates (i.e., the faceplate and the rear plate) arranged opposite each other, as shown in
[Fifth Embodiment]
In this embodiment, another example will be described on the method for calculating the threshold values at the time of controlling the arrangement of the plate-shaped spacers.
Like the fourth embodiment, the plate-shaped spacers SP1, SP2 and SP3 have the heights of L1, L2 and L3, respectively, in the relations of L1<L2<L3, as shown in
If the height difference ΔH becomes larger, a stress value to occur on the substrate surfaces just above the plate-shaped spacers may become larger. In this embodiment, therefore, the array of the plate-shaped spacers is so selected that the height difference ΔH may satisfy the following inequality:
ΔH≦C2·a2/h{σ0−C3(a/h)2}.
Here: characters C2 and C3 designate constants depending on the materials of the substrates (i.e., the face plate and the rear plate) or the like; characters σ0 designate an allowable stress value; letter a designates the interval (or pitch) of the plate-shaped spacers; and letter h designates the thickness of the substrates (i.e., the face plate and the rear plate).
If the height difference ΔH satisfies the above-specified inequality, a stress at an allowable value or higher does not occur at the oppositely arranged substrates, so that a vacuum sealed container having no breakage can be prepared.
This embodiment used a glass substrate (of float sheet glass) having a thickness of 2.8 mm for the face plate and the rear plate.
The plate-shaped spacers were prepared by arranging glass substrates worked to have a width of 0.2 mm, a height of 1.6 mm and a length of 800 mm, at a pitch of 26 mm. The allowable stress value used was 6.9 MPa, which corresponded to the long-term breakage stress of the general float sheet glass. Moreover, the array of the plate-shaped spacers was so determined from the aforementioned inequality that the height difference ΔH might be 5.2 microns or less. Thus, it was possible to manufacture the image display device of no breakage, in which all the plate-shaped spacers contacted with the glass substrates (i.e., the face plate and the rear plate) arranged opposite each other, as shown in
[Sixth Embodiment]
In this embodiment, columnar spacers are used as the support members for supporting the face plate and the rear plate.
A columnar spacer 4 is exemplified by a spacer of a cylindrical shape having a circular section (of a radius R) and a height H, as shown in
A construction diagram of an image display device using the columnar spacers thus far described will be explained with reference to
In
In this embodiment, the columnar spacers are arranged in the sequential order of the larger heights H based on the data of the heights H. Here, the array rule of this case is that the columnar spacers are arranged at one corner in the plane and then sequentially at 1 to 9 in the diagonal directions from the larger ones as shown in
Thus, the variation in the heights between the adjoining columnar spacers could be reduced to provide effects like those of the foregoing individual embodiments.
[Seventh Embodiment]
The receiving circuit C20 and I/F unit C30 may be put in a different case than that of the image display device C10 as a set top box (STB) or the case of the image display device C10.
This application claims priority from Japanese Patent Application No.2003-293956 filed Aug. 15, 2003, which is hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-293956 | Aug 2003 | JP | national |
