An upper area over an element substrate is sealed by a sealing
substrate to which a desiccant is fixed on an internal surface of
the sealing substrate. A substance prepared by dispersing moisture
absorbent grains into an adhesive made of resin is used as the desiccant.
Further, the size of the moisture absorbent grains is defined to
be equal to or smaller than 10 .mu.m. In this manner, the desiccant
can be prevented from cracking due to temperature variations.
What is claimed is:
1. A display apparatus in which display operation is carried out
by controlling emission of each pixel arranged in a matrix, the
apparatus comprising: an element substrate on which a luminous element
is formed for each of the pixels; a sealing substrate on which a
protrusion is formed in a surrounding area thereof, the protrusion
being adhered to the periphery of said element substrate so as to
seal an upper space over said element substrate, and a desiccant
fixed on an internal surface of the sealing substrate opposed to
the element substrate so as to make the upper space located over
the element substrate dry, wherein said desiccant consists of an
adhesive made of resin and moisture absorbent grains dispersedly
mixed into the adhesive, and the size of said moisture absorbent
grains is equal to or smaller than 10 .mu.m.
2. A display apparatus according to claim 1 wherein said moisture
absorbent grains are CaO grains.
3. A display apparatus according to claim 1 wherein said adhesive
is a thermoplastic resin.
4. A display apparatus according to claim 3 wherein said thermoplastic
resin is an acrylic resin or an epoxy resin.
5. A display apparatus according to claim 1 wherein the size of
said moisture absorbent grains is between 0.1 .mu.m and 10 .mu.m.
6. A display apparatus according to claim 1 wherein said desiccant
is formed in the shape of a spiral on a surface of the sealing substrate
opposed to the element substrate.
7. A desiccant which absorbs moisture consisting of: an adhesive
of resin, and moisture absorbent grains dispersedly mixed into the
adhesive, wherein the diameter of said moisture absorbent grains
is equal to or smaller than 10 .mu.m.
8. A desiccant according to claim 7 wherein said moisture absorbent
grains are CaO grains or BaO grains.
9. A desiccant according to claim 7 wherein said adhesive is any
one of a thermoplastic resin, thermosetting resin and UV setting
10. A desiccant according to claim 9 wherein said thermoplastic
resin is an acrylic resin or an epoxy resin.
11. A desiccant according to claim 7 wherein the size of said
moisture absorbent grains is between 0.1 .mu.m and 10 .mu.m.
BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a display apparatus in
which display operation is executed by controlling emission of each
pixels disposed in a matrix, and more particularly to a desiccant
which is suitable for the display apparatus.
 2. Description of the Related Art
 Organic electroluminescence display panels (organic EL panels)
are one known type of flat display panel. Because, unlike a liquid
crystal display (LCD) panel, an organic display panel is self-emitting,
there is growing expectation that organic electroluminescence displays
will become widely used as well-lit, high-viewability flat display
 An organic EL panel is typically configured by arranging
a plurality of organic EL elements as pixels in a matrix. A passive
type and an active type driving method, similarly to LCDs, are available
as a method for driving the organic EL elements, and an active matrix
type driving method is considered to be more preferable, as in the
case of LCDs. More specifically, because display with high resolution
can be realized by the active matrix driving method in which switching
elements (usually, two switching elements: one for switching and
one for driving) are provided for every pixel and display on each
pixel is controlled by controlling the switching elements, the active
matrix driving method is more preferable to a passive driving method
in which there is no switching element provided on a pixel-by-pixel
 Here, the organic EL elements are emitted by the passage
of a current through an organic emitting layer. However, these organic
layers are prone to degradation due to moisture.
 Accordingly, with respect to an element substrate on which
the organic EL elements are provided in an organic EL display panel,
upper space located over a display region where the organic EL elements
are to be disposed (where pixels are existing) is covered with a
cap (a sealing substrate) which is adhered to the element substrate
at the perimeter of the cap for establishing the upper space as
hermetic space, and a desiccant is placed in the space, to thereby
preclude moisture. In other words, by fixing the desiccant on an
inner surface of the sealing substrate, moisture contained in the
upper space over the organic EL elements is eliminated through the
 It should be noted that such a desiccant is described in
Japanese Patent Laid-Open Publication No. Hei 11-312581 etc.
 Conventional organic EL display panels such as described
above, however, suffer from a problem that the desiccant could come
unstuck and the unstuck desiccant damages the element substrate.
SUMMARY OF THE INVENTION
 According to the present invention, the size of moisture
absorbent grains to be dispersed into an adhesive is defined to
be equal to or smaller than 10 .mu.m. This definition can minimize
the risk of producing cracking of a desiccant due to temperature
variations, which results in the solution of the problem caused
by, for example, the unstuck desiccant.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1 shows a structure of a display apparatus according
to an embodiment;
 FIG. 2 shows an adhered state of a desiccant;
 FIG. 3 shows cracks on the desiccant, and
 FIG. 4 is a diagram showing a relationship between grain
size of a moisture absorbent and occurrence of a crack on the desiccant.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Referring to drawings, an embodiment of the present invention
will be described below.
 FIG. 1 is a schematic diagram showing a structural overview
of a display apparatus according to the present embodiment. An element
substrate 10 is made of a glass substrate, and on the element substrate
10 a great number of TFTs, wiring, and organic EL elements disposed
in a matrix are formed. In particular, the organic EL elements and
a pixel circuit for driving the organic EL elements are provided
for every pixel.
 A peripheral driver circuit placed at the periphery of a
pixel region on which pixels are formed generates a predetermined
signal according to display data supplied from the outside, which
causes the organic EL elements for each pixel to emit according
to the display data, to thereby carry out desired display.
 On the periphery of the element substrate 10 a sealing
substrate 14 is adhered by a sealant 12. The sealing substrate 14
is made of, for example, glass and hollowed out leaving a surrounding
area so as to take on the shape of a cap. Accordingly, the sealing
substrate 14 has, in the surrounding area, a protrusion 14a which
is adhered to the periphery of the element substrate 10 using the
 Further, a desiccant 16 is formed adhering to an internal
surface of the sealing substrate 14 which is opposed to the element
substrate 10. The desiccant 16 is shaped, for example, in a spiral
as shown in FIG. 2 having a thickness of approximately 10 to 150
.mu.m and a width of approximately 1000 to 2000 .mu.m.
 Here, the sealing substrate 14 should be prepared in a state
where the desiccant 16 is formed before the element substrate 10
is completed. This preparation is made in a dry environment. Then,
the sealant 12 is adhered to either the sealing substrate 14 or
the element substrate 10 also in the dry environment, for example,
in a depressed atmosphere of nitrogen, and then the sealing substrate
14 is pressed against the element substrate 10 for joining.
 In this manner, internal space 18 formed by the element
substrate 10 and the sealing substrate 14 is sealed and dried. Further,
the desiccant 16 takes up moisture introduced from the elements
or other components on the element substrate 10 and moisture that
enters into the internal space from the outside via the sealant
12. As a result, decrease of lifespan of an organic layer etc. on
the element substrate 10 can be prevented effectively.
 Here, it should be noted that the desiccant 16 in this embodiment
is a thermoplastic resin (an adhesive) of, for example, acrylic
into which moisture absorbent (for example, CaO) grains are dispersedly
introduced. Although the desiccant 16 contains a solvent therein,
thereby being in a slightly fluidized state when it is formed and
adhered to the sealing substrate 14 the solvent is vaporized afterward
so that the desiccant 16 is hardened.
 The size of the moisture absorbent grains in this embodiment
is specified to 10 .mu.m or smaller. With this specification, the
thermoplastic resin is prevented from cracking due to, for example,
temperature variations during use of the display apparatus, and
thereby prevented from coming unstuck or falling off from the sealing
substrate 14 which enables effective avoidance of detrimental effects
on the components of the sealing substrate 14.
 In order to verify that the display apparatus is resistant
to the temperature variations during use, the display apparatus
is subjected to a test, for example, to determine reliability by
placing the display apparatus in an environment at temperatures
of from -30.degree. C. to 80.degree. C. It should be noted that
there is a significant difference in coefficients of thermal expansion
between the moisture absorbent grains themselves and the desiccant
containing the moisture absorbent grains.
 Table 1 shows coefficients of thermal expansion for three
moisture absorbents of CaO, BaO, and silica gel and an acrylic thermoplastic
resin (an adhesive).
1 TABLE 1 Coefficient of thermal expansion Moisture Absorbent CaO
5 .times. 10.sup.-6 to 25 .times. 10.sup.-6 BaO 5 .times. 10.sup.-6
to 25 .times. 10.sup.-6 Silica Gel 1 .times. 10.sup.-6 to 15 .times.
10.sup.-6 Adhesive Acrylic thermoplastic resin 100 .times. 10.sup.-6
to 200 .times. 10.sup.-6
 As can be seen from the table, the coefficient of thermal
expansion of the adhesive is two orders of magnitude greater, compared
with the coefficients of thermal expansion of the moisture absorbents.
Such a significant difference in the coefficients of thermal expansion
increases separation between the adhesive 16a and the moisture absorbent
grains 16b at their interface based on the difference in the coefficients
of thermal expansion when the temperature varies, which could often
manifest itself in the form of, for example, cracks 16c as shown
in FIG. 3.
 However, by conducting various experiments, a remarkable
relationship between the size of the moisture absorbent grains and
the probability of occurrence of cracking was found. More specifically,
as shown in FIG. 4 the probability of occurrence of cracking increases
sharply after the size of the moisture absorbent grains exceeds
10 .mu.m, whereas almost no cracks appear when the size is equal
to or smaller than 10 .mu.m. Therefore, by using a desiccant prepared
by dispersing moisture absorbent grains which are of the size equal
to or smaller than 10 .mu.m into an adhesive, the occurrence of
cracking can be prevented in an efficient manner. It should be noted
that although FIG. 3 shows an example in which CaO is used as the
moisture absorbent and an acrylic thermoplastic resin is used as
the adhesive, the above-listed three substances may be used for
the moisture absorbent in general, or other moisture absorbents
basically made of an inorganic substance and having a similar coefficient
of thermal expansion may be employed. Regarding the coefficients
of thermal expansion of thermoplastic resins which can be used as
the adhesive, the difference between the thermoplastic resins is
not so significant compared with the difference between the thermoplastic
resin and the moisture absorbent. Therefore, it can be said that
the grain size of the moisture absorbent may preferably be defined
to be equal to or smaller than 10 .mu.m.
 Although there is no lower limit to the grain size of the
moisture absorbent as long as the grain size does not exceed 10
.mu.m, it is preferable that the grain size is greater than 0.1
.mu.m because the moisture absorbent whose grain size is 0.1 .mu.m
or smaller has difficulties in, for example, dispersing into the
adhesive. In other words, the grain size of from 0.1 to 10 .mu.m
is most amenable to the moisture absorbent grains.
 When moisture absorbent grains having the coefficient of
thermal expansion of approximately from 1.times.10.sup.-6 to 25.times.10.sup.-6
are dispersed into the adhesive having the coefficient of thermal
expansion of approximately from 100.times.10.sup.-6 to 200.times.10.sup.-6
it can be said that the grain size of the moisture absorbent is
preferably defined between approximately 0.1 to 10 .mu.m.
 In the above explanation, thermoplastic resin is used as
the adhesive, however thermosetting resin or UV setting resin can
also be used as the adhesive. The thermosetting resin and the UV
setting resin also have the coefficient of thermal expansion of
approximately from 100.times.10.sup.-6 to 200.times.10.sup.-6.