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Abstract:

An input pen (60) of the present invention is an input pen used for
performing an input to a touch-panel-integrated liquid crystal display
device (100) (display device). The liquid crystal display device (100)
includes a plurality of photosensitive elements (30) that senses light
transmitted through a panel surface. The photosensitive elements (30)
detect a position of input by sensing an image on a surface of a display
panel. The input pen (60) includes a retroreflective element (61) at its
tip that is to be in contact with the display panel. The retroreflective
element (61) is made up of a spherical glass (62) (spherical transparent
member) and an elastic reflective element (63). In this way, it is
possible to provide an input pen which is to be used with a
touch-panel-integrated display device and which makes it possible to
perform a more accurate position detection.

Claims:

1. An input pen for performing an input to a touch-panel-integrated
display device,the touch-panel-integrated display device comprising:a
plurality of photosensitive elements for sensing light transmitted
through a panel surface,the touch-panel-integrated display device
detecting a position of input by having the plurality of photosensitive
elements sense an image on a surface of a display panel,the input pen
comprising:a retroreflective member being provided at a tip of the input
pen that is to be in contact with the display panel.

2. The input pen according to claim 1, wherein the retroreflective member
is a retroreflective bead.

3. The input pen according to claim 2, wherein:the retroreflective bead
comprises a spherical transparent member and an elastic reflective
member,the spherical transparent member being fixed at the tip of the
input pen, andthe elastic reflective member being provided to cover at
least a part of a surface of the spherical transparent member, upon
contact of the input pen with the surface of the display panel.

4. The input pen according to claim 2, wherein the retroreflective bead is
made of a material having a refraction coefficient of at least 1.41.

5. The input pen according to claim 4, wherein the retroreflective bead is
made of a material having a refraction coefficient of 1.9 or above.

6. A touch-panel input system comprising:a touch-panel-integrated display
device including a plurality of photosensitive elements for sensing light
transmitted through a panel surface, the touch-panel-integrated display
device detecting a position of input by having the plurality of
photosensitive elements sense an image on a surface of a display panel;
andan input pen as set forth in claim 1, for performing an input to the
touch-panel-integrated display device.

Description:

TECHNICAL FIELD

[0001]The present invention relates to an input pen used for performing an
input to a touch-panel-integrated display device that has a touch-panel
function, and to a touch-panel input system including the input pen.

BACKGROUND ART

[0002]Touch-panel-integrated display devices having a touch-panel function
are being developed among display devices such as liquid crystal display
devices. These touch-panel-integrated display devices can detect a
position of contact on a panel surface touched by using an input pen.

[0003]Dominant types of input pens used in conventional
touch-panel-integrated display devices include resistance-film-type input
pens (i.e. a type of input pen in which a position of input is detected
by having an upper conductive substrate be in contact with a lower
conductive substrate, due to application of pressure) and electrostatic
capacity input pens (i.e. a type of input pen in which a position of
input is detected by detecting a change in capacitance of a touched
location).

[0004]In recent years, technology has been progressing which is related to
liquid crystal display devices in which photosensitive elements such as
photodiodes and phototransistors are provided for each pixel (or for each
group of pixels) inside an image display area (e.g., see Patent
Literature 1). By embedding photosensitive elements for each pixel in
this way, it has become possible to achieve scanner functions and
touch-panel functions in standard liquid crystal display devices. In
other words, by having the photosensitive elements function as area
sensors, it is possible to achieve the touch-panel-integrated liquid
crystal display devices.

[0007]In a case where a liquid crystal display device including such
photosensitive elements is used as a display device having a touch-panel
function, the photosensitive elements pick up, as an image, a pen or a
finger displayed on a display panel of the display device. Then, the
liquid crystal display device performs a position detection by sensing a
position of a tip of the pen or the finger.

[0008]In the touch-panel-integrated display devices configured as above, a
proposal has been made of a configuration in which a light source such as
a light-emitting diode is provided in the input pen, in order to enable
the photosensitive elements to sense a position of a pen input more
precisely. Such input pens provided with a light source are called "LED
penlights".

[0009]In this way, because light of the light-emitting diode is irradiated
from the pen tip on a liquid crystal display panel, the input pens
provided with the light source enable the photosensitive elements
provided inside the liquid crystal display panel to recognize the
position of the pen more easily.

[0010]However, with the input pens configured as above, a problem occurs
that the position of input is incorrectly detected at a shifted position.
Reasons for this problem are as follows.

[0011]Usually, when a user uses a pen to touch a panel, a panel surface is
not touched from directly above the display panel (that it to say, from a
direction perpendicular to the panel surface), but rather touched at an
angle of about 45° (for example) with respect to the liquid
crystal display panel surface.

[0012]As a result, with the above configuration, because the light
irradiated from the light source that is provided in the pen is incident
on the liquid crystal display panel surface by having an oblique
directivity with respect to the liquid crystal display panel surface, a
problem occurs that the input is erroneously sensed as being an input at
a position slightly shifted from an actual position of the input.

[0013]FIG. 6 shows a typical example of a pen input performed on a panel
surface of a liquid crystal display device including photosensitive
elements, by using an input pen that includes a light source. As shown in
FIG. 6, a light source 161 such as a light-emitting diode mounted in an
input pen 160 has a directivity as indicated in FIG. 6 by an arrow.
Accordingly, if the pen is put in contact obliquely with the panel
surface, the light irradiated from the input pen is detected as having a
higher amount of light by a photosensitive element 30b that is disposed
at a slightly shifted location, rather than being detected by a
photosensitive element 30a, which is disposed directly under the actual
position of input. In this way, with the input pen provided with the
light source, such a problem occurs that the input is erroneously sensed
at a position slightly shifted from the actual position of input.

[0014]The present invention is attained in view of the above problems. An
object of the present invention is to provide an input pen to be used
with a touch-panel-integrated display device, which enables a more
accurate position detection.

[0015]In order to solve the above problems, an input pen in accordance
with the present invention is an input pen for performing an input to a
touch-panel-integrated display device, the touch-panel-integrated display
device including a plurality of photosensitive elements for sensing light
transmitted through a panel surface, and the touch-panel-integrated
display device detecting a position of input by having the plurality of
photosensitive elements sense an image on a surface of a display panel,
the input pen including a retroreflective member being provided at a tip
of the input pen that is to be in contact with the display panel.

[0016]An input pen in accordance with the present invention is used for
performing an input to a touch-panel-integrated display device, which
touch-panel-integrated display device is a display device having a
touch-panel function by including photosensitive elements that are used
as area sensors.

[0017]So that the photosensitive elements can detect the position of the
pen input, it is necessary for the pen tip of the input pen to be easily
detectable by the photosensitive elements. Several configurations are
possibly considered to achieve this feature: for example, a configuration
in which the pen tip itself is luminous, or a configuration in which a
reflectivity of the pen tip is enhanced. However, if a light-emitting
diode and the like is mounted in the pen tip so that the pen itself is
luminous, directivity of the light emitted from the input pen varies
depending on an angle of inclination of the pen with respect to the
surface of a liquid crystal panel, which causes the position where the
input pen is in contact with the panel to be detected at a position
slightly shifted from the actual position of input. Further, merely
providing the pen tip with a material having a highly reflective mirrored
surface does not make it possible to enhance reflectivity in a
satisfactory way, as a problem occurs that it is not possible to control
a direction of reflection of the light; for example, in a case where the
panel surface is touched by the pen in an inclining manner, the light is
reflected in a direction shifted from the actual position of input. This
makes it impossible to accurately detect the position of input.

[0018]In this regard, the present invention has a retroreflective member
provided in the pen tip of the input pen as described above. A
retroreflective member is a member that has a function to reflect
incident light to mainly a direction from which the light is incident.

[0019]With the above configuration, it is possible to retroreflect for
example light irradiated from a backlight and transmitted through a
display panel, by use of the retroreflective member provided in the pen
tip of the input pen. In this way, an amount of light irradiated from the
pen tip is markedly higher than an amount of light irradiated from other
positions, thereby making it possible to perform position detection more
easily and more accurately.

[0020]Further, light originating from a light source and the like of the
backlight which is irradiated and transmitted through the display panel
has a directivity perpendicular to the surface of the display panel. As a
result, since the retroreflective member is provided on an extremity of
the input pen, it is similarly possible to reflect this light having the
directivity perpendicular to the surface of the display panel as light
which also has a directivity perpendicular to the surface of the display
panel. In this way, even if the input pen is put in contact with the
panel at an inclined angle, the photosensitive elements disposed directly
under the position of input are able to sense a high amount of light,
thereby making it possible to perform a more accurate detection of the
inputted position.

[0021]Further, no light source and power supply for the light source is
necessarily provided in the input pen as in the conventional technology.
This makes it possible to obtain a lightweight and low-cost input pen.

[0022]In an input pen in accordance with the present invention, the
retroreflective member may be a retroreflective bead. The retroreflective
bead may for example be made of (i) a spherical transparent member (for
example glass) and (ii) a reflective member such as metal that covers a
part of a surface of the spherical transparent member.

[0023]Further, the input pen as above is preferably configured so that the
retroreflective bead includes a spherical transparent member and an
elastic reflective member, the spherical transparent member being fixed
at the tip of the input pen, and the elastic reflective member being
provided to cover at least a part of a surface of the spherical
transparent member, upon contact of the input pen with the surface of the
display panel.

[0024]When a touch panel input is performed using a conventional input pen
having the light source, there are no major variations in an amount of
light received by the photosensitive elements mounted inside the liquid
crystal display device because an amount of light outputted from the
light source does not vary depending on whether or not a pen tip is in
contact with the panel surface. As a result, it is difficult to clearly
distinguish between a situation where the input pen is in contact with
the display panel and a situation where the input pen is not in contact
with the display panel.

[0025]In contrast, with the above configuration, when the input pen is in
contact with the display panel surface, at least a part of a surface of a
spherical transparent member is covered with a reflecting member, thus
causing the spherical transparent member to be retroreflective. In this
way, with the above configuration, characteristics of the tip are changed
depending on whether or not the input pen is in contact with the display
panel; the tip of the pen is not retroreflective when the input pen is
not in contact with the surface of the display panel, and on the other
hand, the tip of the pen is retroreflective when the input pen is in
contact with the surface of the display panel.

[0026]When the tip of the pen is retroreflective, it is possible to
efficiently irradiate the light of the backlight on the photosensitive
element. As a result, at a time when the input pen touches the liquid
crystal display panel, an output of the photosensitive element disposed
towards the liquid crystal display panel markedly increases as compared
to at a time when the input pen is not in contact with the liquid crystal
display panel.

[0027]Accordingly, with the above configuration, it is possible to more
accurately distinguish between a situation in which the input pen is in
contact with the display panel and a situation in which the input pen is
not in contact with the display panel.

[0028]Glass, for example, may be used as material for the transparent
member.

[0029]With the input pen as above, the retroreflective bead is preferably
made of a material having a refraction coefficient of at least 1.41.

[0030]With the above configuration, the retroreflective beads are capable
of retroreflecting more incident light.

[0031]With the input pen as above, the retroreflective bead is preferably
made of a material having a refraction coefficient of 1.9 or above.

[0032]With the above configuration, in a case where the input pen is put
in contact with the panel surface at an angle of 45° with respect
to the panel surface, it is possible to retroreflect the incident light.

[0033]Further, in order to solve the above problems, a touch-panel input
system in accordance with the present invention includes (i) a
touch-panel-integrated display device including a plurality of
photosensitive elements for sensing light transmitted through a panel
surface, the touch-panel-integrated display device detecting a position
of input by having the plurality of photosensitive elements sense an
image on a surface of a display panel, and (ii) any one of the above
input pens for performing an input to the touch-panel-integrated display
device.

[0034]With the touch-panel input system in accordance with the present
invention, because the touch panel input is performed by using any one of
the above input pens, the photosensitive elements provided in the display
device are capable of detecting the position of the pen tip that is put
in contact with the panel surface more easily and more accurately. As a
result, it becomes possible to perform a more accurate position detection
in the touch-panel input system.

[0035]A fuller understanding of the other objectives, characteristics and
merits of the present invention can be obtained through the ensuing
description. Further, the advantages of the present invention will become
obvious by referring to the following description taken in conjunction
with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0036]FIG. 1 is a sectional view of a configuration of an input pen in
accordance with one embodiment of the present invention.

[0037]FIG. 2 is a sectional view of a configuration of a
touch-panel-integrated liquid crystal display device in accordance with
one embodiment of the present invention.

[0038]FIG. 3 is a schematic view of a configuration of a touch-panel input
system in accordance with one embodiment of the present invention,
illustrating a situation in which an input is performed to the
touch-panel-integrated liquid crystal display device shown in FIG. 2 by
using the input pen shown in FIG. 1.

[0039]FIG. 4 is a graph illustrating a relation between (i) a distance
from a pen tip of an input pen to a surface on which a photosensitive
element (photosensor) is positioned and (ii) an output of the
photosensitive element.

[0040]FIG. 5 is a schematic view of a structure in a situation where a tip
of the input pen is in contact with a flat surface.

[0041]FIG. 6 is a schematic view of a situation in which an input is
performed to the touch-panel-integrated liquid crystal display device by
using a conventional input pen in which a light source is mounted.

[0061]The following is an explanation of one embodiment of the present
invention, with reference to FIGS. 1 to 5. It must be noted that the
present invention is not limited to the following description.

[0062]The present embodiment describes a touch-panel input system
including: a touch-panel-integrated liquid crystal display device that
has a touch-panel function; and an input pen that is used for inputting
information by having the input pen be in contact with a panel surface of
the touch-panel-integrated liquid crystal display device.

[0063]First, the following is an explanation of a touch-panel-integrated
liquid crystal display device in accordance with the present embodiment,
with reference to FIG. 2. A touch-panel-integrated liquid crystal display
device 100 (also called the liquid crystal display device 100) has a
touch-panel function that detects a position of input by having
photosensitive elements provided for each pixel sense an image on a
surface of a display panel.

[0064]As shown in FIG. 2, the touch-panel-integrated liquid crystal
display device 100 includes a liquid crystal display panel 20 and a
backlight 10. The backlight 10 is provided on a backside of the liquid
crystal display panel and irradiates light on the display panel.

[0065]The liquid crystal display panel 20 includes (i) an active matrix
substrate 21 including a plurality of pixels disposed in a matrix
configuration, (ii) a counter substrate 22 disposed so as to face the
active matrix substrate 21, and (iii) a liquid crystal layer 23
sandwiched between the two substrates. The liquid crystal layer 23 serves
as a display medium.

[0066]A front wave plate 50a and a back wave plate 50b are provided as
optical compensation elements, respectively on an outer side of the
active matrix substrate 21 and on an outer side of the counter substrate
22. In a case where a liquid crystal material contained in the liquid
crystal layer is of a vertical alignment type for example, the front wave
plate 50a and the back wave plate 50b are disposed so as to improve
transparency or angle characteristics. It should also be noted that
display is performable even when such wave plates are not provided.

[0067]Further, a front polarization plate 40a and a back polarization
plate 40b are additionally provided on an outer side of the front wave
plate 50a and on an outer side of the back wave plate 50b, respectively.

[0068]Each of the polarization plates 40a and 40b serve as polarizers. For
example, in a case where a liquid crystal material contained in the
liquid crystal layer is of a vertical alignment type, the front
polarization plate 40a and the back polarization plate 40b are disposed
so that polarization directions of the front polarization plate 40a and
the back polarization plate 40b have a crossed Nicols relationship, in
order to achieve a normally black mode liquid crystal display device.

[0069]The active matrix substrate 21 includes a TFT, an alignment film
(not shown), photosensitive elements 30 and the like. The TFT and
alignment film serve as a switching element for driving each pixel.

[0070]Further, in the counter substrate 22, a color filter layer 24, a
counter electrode, an alignment film (both not shown) and the like are
provided. The color filter layer 24 includes colored sections whose
respective colors are red (R), green (G) and blue (B), and a black
matrix.

[0071]As described above, in the touch-panel-integrated liquid crystal
device 100 in accordance with the present embodiment, photosensitive
elements are provided in each pixel area, thus making area sensing
possible. In this way, when the input pen touches a specific location on
a surface of the liquid crystal display panel 20, the photosensitive
elements 30 perceives this location, inputs information into a device and
makes it possible for an intended operation to be performed. Accordingly,
the photosensitive elements 30 make it possible to achieve the
touch-panel functionality in the touch-panel-integrated liquid crystal
device 100 in accordance with the present embodiment.

[0072]In the present invention, it is not absolutely required to provide a
photosensitive element for each single pixel, and it is possible to
employ a configuration in which a photosensitive element is provided for
each pixel having a color filter of any color among R, G and B.

[0073]Further, possible configurations of the touch-panel-integrated
liquid crystal display devices are not strictly limited to the
configurations described above, and it is possible to employ
configurations similar to that of conventionally known liquid crystal
display devices that include the photosensitive elements.

[0074]Next is an explanation of a configuration of an input pen used to
perform a touch-panel input to the touch-panel-integrated liquid crystal
display device 100. FIG. 1 shows a sectional view of a configuration of
an input pen 60 in accordance with the present embodiment.

[0075]As shown in FIG. 1, a retroreflective member 61 is provided on a tip
of the input pen 60. The retroreflective member 61 is a member that
reflects incident light mainly to a direction from which the light is
incident.

[0076]The input pen 60 in accordance with the present embodiment includes
a retroreflective member 61, which is made from a spherical glass 62
(spherical transparent member) and a reflective member 63. The spherical
glass 62 may be made of another transparent member, such as resin.
Concrete examples of the transparent member include polycarbonate, epoxy,
acrylic, and polyolefin. The reflective member 63 is an elastic body in
which a metallized film of aluminum or the like is provided on a surface
of contact with the spherical glass 62. Silicon rubber and the like may
be used as material for the elastic body.

[0077]Further, as shown in FIG. 1, the input pen 60 includes, in addition
to the retroreflective member 61, a pointed component 64 and a holding
component 65. The pointed component 64 is externally shaped as a cylinder
and becomes shaped narrower towards a direction of a tip of the input pen
60. Further, the spherical glass 62 is fixed to the tip of the pointed
component 64. The holding component 65 is a part held by a user when the
user grips the input pen 60. Each of the above-described components is
made of a material such as plastic or the like.

[0078]As shown in FIG. 1, the holding component 65 includes a holding
section 65a for the user to hold the input pen 60 and a protruding
section 65b that is narrower than the holding component 65a. The
reflective member 63, which has a thickness substantially similar to that
of the protruding section 65b, is attached to an extremity of the
protruding section 65b. Further, the protruding section 65b of the
holding component 65 is inserted inside a hollow space inside the
cylindrical pointed member 64. When the input pen 60 is not in use, a gap
65c exists between the pointed component 64 and the holding section 65a
of the holding component 65, as shown in FIG. 1.

[0079]This gap 65c makes it possible to push down the holding section 65a
in a direction of the arrow indicated in FIG. 1. The gap 65c is sized so
that at least a part of a surface of the spherical glass comes in contact
with the reflective member 63 when the holding section 65a is pushed down
in the direction of the arrow. The pushing down of the holding section
65a causes the holding section 65a and the pointed component 64 to be in
contact with each other, which causes the elastic reflective member 63 to
be compressed and be sunk downwards. The spherical glass 62 located at
the tip of the input pen 60 is fixed to the pointed component 64. Hence,
when the holding section 65a is pushed down in a direction indicated by
the arrow in FIG. 1, the compressed reflective member 63 is pressed
against the surface of the spherical glass 62, without causing any shift
in the position of the spherical glass 62. The retroreflective member 61
is obtained by having the reflective member 63 be pressed against the
surface of the spherical glass 62 as above.

[0080]In this way, in the present embodiment, the retroreflective member
61 is achieved as a retroreflective bead. However, the present invention
is not necessarily limited to such a configuration.

[0081]Next is an explanation, conducted with reference to FIG. 3, of a
method to perform a touch panel input to the touch-panel-integrated
liquid crystal display device 100 by using an input pen 60 having a
configuration as above.

[0082]Light having a directivity substantially perpendicular to the panel
surface of the liquid crystal display device 100 (i.e. a directivity
corresponding to arrow A1) is irradiated from the backlight 10. When the
input pen 60 is in contact with the panel surface of the liquid crystal
display device 100, the holding section 65a of the input pen 60 moves in
the direction of the arrow indicated in FIG. 1, in such a manner that the
elastic reflective member 63 is compressed and sinks down so as to cover
the surface of the spherical glass 62. FIG. 3 illustrates a situation in
which the reflective member 63 is sunk down as a result of a
counteraction caused by having the spherical glass 62 located on the tip
of the input pen 60 be in contact with the panel surface of the liquid
crystal display device 100.

[0083]In this way, by touching the panel surface with the input pen 60, it
is possible to obtain a retroreflective member 61 which is made up of the
spherical glass 62 and the reflective member 63. Light from the backlight
and incident on the spherical glass 62 is retroreflected by the
retroreflective member 61. As a result, light reflected by the reflective
element 63 is incident on the liquid crystal display device 100 with a
directivity substantially perpendicular to the panel surface of the
liquid crystal display device 100 (i.e. a directivity corresponding to
arrow A2).

[0084]For comparison purposes, the following is an explanation of a case
where a touch-panel input into the touch-panel-integrated liquid crystal
display device 100 is performed using a conventional input pen provided
with a light source. FIG. 6 illustrates a situation in which an input is
performed to the touch-panel-integrated liquid crystal display device 100
by using an input pen 160 including a light source. The input pen 160
illustrated in FIG. 6 is provided with a light source 161 such as a
light-emitting diode. The light source 161 has a directivity like a
directivity indicated by the arrow in FIG. 6, and irradiates light from a
tip of the input pen 160.

[0085]Thus, as shown in FIG. 6, if the pen is put in contact obliquely
with the panel surface, the light irradiated from the input pen is
detected as having a higher amount of light by the photosensitive element
30b that is disposed at a slightly shifted location, rather than being
detected by the photosensitive element 30a that is disposed directly
under the actual position of input. As a result, when a touch panel input
is performed to the liquid crystal display device 100 by using the input
pen 160, the input is detected as being performed directly above the
photosensitive element 30b that is disposed at a slightly shifted
location, and not detected as being performed directly above the
photosensitive element 30a that is disposed at the actual position of
input. In this way, with the input pen provided with the light source,
input is erroneously sensed as being performed at a position slightly
shifted from the actual position of input.

[0086]In contrast, in a case where the input pen 60 in accordance with the
present embodiment is used, the input pen 60 has the retroreflective
member 61 provided at its tip, as shown in FIG. 2. This retroreflective
member 61 allows the light from the backlight whose directivity
(indicated by the arrow A1 in FIG. 3) is substantially perpendicular to
the panel surface of the liquid crystal display device 100 to be
irradiated from the tip of the input pen 60 also as a light whose
directivity (indicated by the arrow A2 in FIG. 3) is substantially
perpendicular to the panel surface. In other words, the light irradiated
from the backlight and the light reflected by the retroreflective member
61 are parallel to each other however oriented in opposite directions to
each other.

[0087]As a result, when a touch panel input into the liquid crystal
display panel 100 is performed by using the input pen 60, the
photosensitive element 30a located directly under the position of the
touch-panel input detects a highest amount of light. As a result, it is
possible to detect the position of the touch-panel input more precisely.

[0088]Further and as has been explained above, the input pen 60 in
accordance with the present embodiment has the surface of the spherical
glass 62 not covered by the reflective member 63, as shown on FIG. 1,
while the tip of the input pen 60 is not in contact with a flat surface
such as a panel surface of a liquid crystal display device. In such a
case, the light incident on the spherical glass 62 is not retroreflected.
On the other hand, when the tip of the input pen 60 is in contact with
the panel surface of the liquid crystal display device (as shown in FIG.
3), the surface of the spherical glass 62 is covered by the reflective
member 63. This allows the light incident on the spherical glass 62 to be
retroreflected.

[0089]As a result, the input pen 60 causes the amount of light received by
the photosensitive elements 30 and an output of the photosensitive
elements 30 to remarkably vary, depending on whether or not the tip of
the pen is in contact with the panel surface. FIG. 4 is a graph
illustrating a relation between (i) a distance from the pen tip of the
input pen 60 to a surface on which the photosensitive elements 30 are
disposed and (ii) an output of the photosensitive elements 30. In FIG. 4,
the broken line represents the output of the photosensitive elements 30
at a time when the input pen 60 is not in contact with the panel surface
(no contact), and the solid line represents an output of the
photosensitive elements 30 at a time when the input pen 60 is in contact
with the panel surface (contact).

[0090]At the time when the input pen 60 is not in contact with the panel
surface (no contact), the output of the photosensitive elements increases
gradually as the distance from the tip of the pen to the photosensitive
elements (i.e. moving from right to left along the line in FIG. 4)
shortens. Then, when a point is reached where the distance from the tip
of the pen to the photosensitive elements is equal to d1, the output of
the photosensitive elements 30 increases markedly. In the embodiment, d1
is a distance from a top surface of the liquid crystal display device 100
to a surface on which the photosensitive elements 30 are located (see
FIG. 3). In this way, the output of the photosensitive elements 30
changes significantly depending on whether the tip of the input pen 60 is
in contact or is not in contact with the panel surface. As a result, it
is possible to more clearly distinguish between a situation where the
input pen 60 is in contact with the surface of the liquid crystal display
panel and a situation where the input pen 60 is not in contact with the
surface of the liquid crystal display panel.

[0091]The "distance from the pen tip to the photosensitive elements"
represented by the horizontal axis in the graph of FIG. 4 does not in
reality become smaller than d1. In the graph of FIG. 4, a theoretical
value is indicated for the distance from the tip of the pen to the
photosensitive element in a hypothetical case where the distance from the
tip of the pen to the photosensitive element is lower than d1.

[0092]Further, with the input pen in accordance with the present
invention, when using a retroreflective bead as the retroreflective
element, a refraction coefficient of the spherical glass 62 (bead) is
preferably at least 1.41. If the refraction coefficient is at least 1.41,
the spherical glass has retroreflective characteristics. Further, a
higher reflection coefficient makes it possible to accurately
retroreflect incident light even if the input pen is used obliquely. If
the refraction coefficient is 1.9 or above, it is possible to
retroreflect the incident light even if the input pen is put in contact
with the panel surface at an angle of 45°. Further, with a
refraction coefficient of 2.0, it is possible to retroreflect the
incident light even if the contact is performed with the input pen
inclined to the degree that the input pen is substantially parallel to
the panel surface.

[0093]Moreover, the reflective element 63 further preferably includes the
following configuration.

[0094]In concrete terms, two spots on the surface of the spherical glass
62 which are located in a longitudinal direction x of the input pen 60
with respect to a center G of the spherical glass 62 are set as poles.
Among these two poles, the one pole which is farthest from the tip of the
input pen is called pole P, and a position of pole P is considered to be
0°. When the input pen is put in contact with the surface of the
display panel, the reflective member 63 is preferably in contact with the
surface of the spherical glass 62 at an angle in a range from 10°
to 90° where the 0° pole is a point of reference, so as to
cover part of the spherical glass surface. FIG. 5 illustrates a situation
in which the tip of the input pen 60 is in contact with a surface S of a
liquid crystal panel and the like, in a substantially perpendicular
manner.

[0095]In a case where the tip of the input pen is in contact with the
surface S of a liquid crystal display panel and the like in a
substantially perpendicular manner, as long as the reflective member 63
covers the surface of the spherical glass 62 at a range of at least
10°, most of the light incident on the spherical glass 62 is
reflected within such a range. As a result, the light incident on the
spherical glass 62 is irradiated from the spherical glass 62 towards the
same direction as the incident direction, after the incident light is
reflected by the reflection member 63. In this way, it is possible to
retroreflect incident light more accurately when the input pen is in
contact with the surface of the display panel.

[0096]Further, the spherical glass 62 is connected to the pointed
component 64 at a location corresponding to an angle of 90° with
respect to the pole P that serves as reference. As a result, when the tip
of the pen is put in contact with the surface S of the liquid crystal
display panel and the like, the elastic reflective member 63 covers a
maximal range of 90° of the spherical glass 62 surface.

[0097]The present invention is not limited to the above-described
embodiments, and various modifications are possible within the scope of
the following claims. Embodiments obtained by combining the technical
means disclosed here as appropriate are also included within the
technical scope of the present invention.

[0098]As above, an input pen in accordance with the present invention is
an input pen used to perform an input into a touch-panel-integrated
display device, wherein the touch-panel-integrated display device (i)
includes a plurality of photosensitive elements sensing light transmitted
from a surface of a panel and (ii) detects a position of input thanks to
the photosensitive elements sensing pixels of the surface of the panel, a
retroreflective member being provided on a tip of the input pen in
contact with the display panel.

[0099]Accordingly, with the above configuration, it is possible to
retroreflect for example light irradiated from a backlight and passed
through a display panel, by use of the retroreflective member provided on
the pen tip of the input pen. In this way, an amount of light irradiated
from the pen tip is markedly higher than an amount of light irradiated
from other positions, thereby making it possible to perform a position
detection more easily and more accurately.

[0100]Further, even if the input pen is put in contact with the panel at
an inclined angle, the photosensitive elements that are disposed directly
under the position of input are able to sense a high amount of light. As
a result, it is possible to perform a more accurate detection of the
inputted position.

[0101]Further, a touch-panel input system in accordance with the present
invention includes (i) a touch-panel-integrated display device including
a plurality of photosensitive elements for sensing light transmitted
through a panel surface, the touch-panel-integrated display device
detecting a position of input by having the plurality of photosensitive
elements sense an image on a surface of a display panel, and (ii) any one
of the above input pens, for performing an input to the
touch-panel-integrated display device.

[0102]With the above configuration, it is possible to achieve a
touch-panel input system that is capable of detecting a more accurate
position detection.

[0103]The detailed explanations of the invention which were given above in
connection with concrete embodiments and examples are merely intended to
clarify the technical contents of the present invention. The present
invention should not be construed to be limited to these examples and
embodiments, and various modifications can be exercised within the spirit
of the invention and the scope of the following claims.

INDUSTRIAL APPLICABILITY

[0104]By performing an input to a touch panel by use of the input pen in
accordance with the present invention, a touch-panel-integrated liquid
crystal display device is capable of detecting a position more
accurately. The input pen in accordance with the present invention is
usable in touch-panel input systems.