JP2009198360A - Optical touch panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumption and simplify the routing of wiring by utilizing a backlight of a liquid crystal cell as a light source for a touch panel, in place of a light source to be installed at the periphery of a display surface. <P>SOLUTION: The optical touch panel 10 includes: a flat light source 2 installed at a back surface of the liquid crystal cell 1, for irradiating the liquid crystal cell 1 with light; a reflective part 3a installed along one side of the liquid crystal cell 1; and a light receiving part 4a disposed along another side of the liquid crystal cell 1. The light emitted from the flat light source 2 is incident on the reflective part 3a, and the reflective part 3a reflects the light to a direction parallel to the surface of the liquid crystal cell 1. The light receiving part 4a receives the light reflected from the reflective part 3a, and converts it into an electric signal. Further, the liquid crystal cell includes a liquid crystal shutter, and can transmit or shield the irradiation light by the unit of cell. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical touch panel. More specifically, the present invention relates to an optical touch panel that performs position detection using light from a backlight provided at a lower portion of a liquid crystal display element.

  FIG. 3 shows a top view of a conventional optical touch panel (see Patent Document 1). A display screen 101 made of a liquid crystal display element or the like has a rectangular shape. A plurality of light emitting elements 102 are provided on two adjacent sides 101 a and 101 b of the display screen 101. A plurality of light receiving elements 103 are provided on two adjacent sides 101c and 101d facing each other. Light emission of the light emitting element 102 is controlled by the control circuit 109. A signal detected by the light receiving element 103 is processed by the processing circuit 110. The light L111 emitted from the uppermost light emitting element 102 on the left side is received by the light receiving element 103 located at the uppermost part on the opposite right side. The light L110 emitted from the light emitting element 102 at the right end of the upper side is received by the light receiving element 103 at the right end of the lower side. Therefore, when a finger touches any position on the display screen 101, light at any position from the left side toward the right side is blocked. Similarly, light at any position from the upper side to the lower side is blocked. By specifying the position where the light is blocked by the light receiving element 103, the xy coordinates of the position are specified.

  In the above example, the plurality of light receiving elements 103 and the plurality of light emitting elements 102 have a one-to-one relationship. Therefore, the number of light receiving elements 103 equal to the number of light emitting elements 102 is provided. In Patent Document 1, a method for reducing the number of light receiving elements 103 is shown. That is, instead of the plurality of light receiving elements 103, the light receiving elements are provided at the corners of the right side 101c and the lower side 101d. A reflecting surface is provided at the position of each light receiving element 103 on the right side 101c and at the position of each light receiving element 103 on the lower side 101d. From each reflecting surface, the light emitted from the light emitting element 102 is reflected toward the light receiving element provided at the corner. Then, the control circuit 109 scans each light emitting element 102 to emit light, and detects the position where the light is blocked by detecting the timing at which the light receiving element receives light.

As another optical touch panel, one using polarized light is known in order to distinguish external light and detection light (see Patent Document 2). In this method, as shown in FIG. 3, a plurality of light emitting elements and a plurality of light receiving elements corresponding to the light emitting elements are installed around the display screen. Further, a polarization axis adjusting device including a polarizing plate and a Faraday element is installed in the vicinity of the light emitting portion of each light emitting element. A similar polarization axis adjusting device is also installed in the light receiving portion of the corresponding light receiving element. Then, a magnetic field is generated in the Faraday element, and the polarization axis is electrically rotated so that it can be distinguished from extraneous light, and the position where the light is blocked is detected.
Japanese Patent Laid-Open No. 06-309100 JP 2005-135329 A

  However, in the conventional optical touch panel described above, a large number of light emitting elements, for example, a large number of light emitting diodes, are provided around the display screen. As a result, current consumption increases, wiring is complicated, and the number of assembly steps increases. In addition, there is a problem that the position resolution is limited depending on the size of the light receiving element.

  In order to solve the above-described problems, the present invention provides a liquid crystal cell having a rectangular surface, a flat light source installed on the back surface of the liquid crystal cell and for irradiating the liquid crystal cell with light, A reflection unit disposed along one side; and a light receiving unit disposed along the other side of the liquid crystal cell, wherein the reflection unit receives light emitted from the planar light source and receives the liquid crystal The light is reflected in a direction parallel to the surface of the cell, and the light receiving unit is an optical touch panel that receives light reflected from the reflecting unit and converts it into an electric signal.

  The reflection part and the light receiving part are formed on the surface of the translucent substrate.

In addition, the light receiving unit includes a second reflecting unit that further reflects the light reflected from the reflecting unit, and a plurality of light receiving elements that receive the light reflected from the second reflecting unit and convert the light into electric signals. And the reflection part and the second reflection part are formed on the surface of the translucent substrate, and the light receiving element is formed on the back surface of the translucent substrate, and is reflected from the second reflection unit. In addition, the light receiving unit includes a second reflecting unit that further reflects light reflected from the reflecting unit, and light reflected from the second reflecting unit. And a plurality of light receiving elements for converting the light into electrical signals, and the light receiving elements are formed in the liquid crystal cell.

  In addition, a filter substrate is inserted between the reflection unit and the second reflection unit and the liquid crystal cell, and the filter substrate is a first unit for introducing light from the planar light source into the reflection unit. A slit and a second slit for introducing light from the second reflecting portion to the light receiving element are provided.

  In addition, the liquid crystal cell blocks and transmits light between a plurality of first liquid crystal shutters that can block and transmit light between the planar light source and the light reflecting unit, and light between the second reflecting unit and the light receiving unit. A plurality of second liquid crystal shutters that can be provided are provided.

  Further, a light shielding film for shielding light from the planar light source is inserted between the light receiving section and the planar light source.

  Further, the first liquid crystal shutter further comprising: a position detection circuit for inputting an electric signal from the light receiving unit and detecting a position where the light reflected from the reflection unit to the light receiving unit is blocked. The transmission frequency includes a modulation circuit for driving the planar light source by superimposing a predetermined frequency component excluding the frequency of commercial power and the scanning frequency of the liquid crystal cell or an integral multiple of the frequency. It was decided that

  In the present invention, a reflection part installed along one side of the liquid crystal cell and a light receiving part arranged along the other side of the liquid crystal cell are provided. The reflection unit receives light emitted from a planar light source for irradiating the liquid crystal cell with light and reflects the light in a direction parallel to the surface of the liquid crystal panel. The light receiving unit is reflected from the reflection unit. Received light and converted it into an electrical signal. As a result, it is not necessary to provide a light source for the touch panel separately from the light source for liquid crystal display, so that it is possible to reduce power consumption, and it is not necessary to form a light emitting element in the vicinity of the display surface. It has the advantage of becoming. In addition, the light emitted from the planar light source can be irradiated and shielded by the liquid crystal cell, and the light received by the light receiving unit can be irradiated and shielded by the liquid crystal cell. Therefore, the position resolution can be increased.

  FIG. 1 is a view for explaining an embodiment of an optical touch panel 10 according to the present invention, FIG. 1 (a) and FIG. 2 are schematic sectional views of the optical touch panel 10, and FIG. 1 is a schematic top view of an optical touch panel 10. FIG.

  In FIG. 1A, the liquid crystal cell 1 includes an upper light transmitting substrate 8a, a lower light transmitting substrate 8b, and a liquid crystal layer (not shown) sandwiched between the both substrates. Between the liquid crystal cell 1 and the planar light source 2, a lower polarizing plate 17b from the liquid crystal cell 1 side and an optical film 21 for adjusting the direction of light emitted from the planar light source 2 are inserted. Further, a filter substrate 18 and an upper polarizing plate 17a are inserted between the liquid crystal cell 1 and the reflecting portion 3a and the second reflecting portion 9a. The light receiving element 16a is formed under the lower polarizing plate 17b.

  The filter substrate 18 has a first slit 19a for passing the emitted light 5a emitted from the planar light source 2 to the reflecting portion 3a and a second slit 19b for passing the reflected light 15a from the second reflecting portion 9a. Is formed. That is, the outgoing light 5a emitted from the planar light source 2 passes through the first liquid crystal shutter 8d and the first slit 19a and enters the reflecting portion 3a. The reflection part 3a reflects the emitted light 5a and emits it as parallel light 6a. The second reflecting portion 9a receives the parallel light 6a and emits it as reflected light 15a. The reflected light 15a passes through the second slit 19b and the second liquid crystal shutter 8c and is received by the light receiving element 16a.

  The first liquid crystal shutter transmits light at the timing of scanning parallel light in time series along the liquid crystal screen. On the other hand, the second liquid crystal shutter transmits light at the same timing as the first liquid crystal shutter so that the light transmitted through the first liquid crystal shutter is transmitted to the light receiving element.

  When the parallel light 6a is blocked by a finger or a pen by an operator's operation, a change occurs in the electric signal output from the light receiving element 16a that receives the blocked parallel light 6a. By detecting this change by a position detection circuit (not shown), the position of the blocked parallel light 6a can be specified.

  As shown in FIG. 1 (b), if the reflecting portions 3a and 3b are provided on the two adjacent sides of the rectangular liquid crystal cell 1 and the light receiving portions 4a and 4b are provided on the other two opposite sides, they are blocked. The plane coordinates of the parallel lights 6a and 6b can be specified, and two-dimensional information can be input.

  Next, a more specific description will be given with reference to FIG. The liquid crystal cell 1 includes an upper light-transmitting substrate 8a, a lower light-transmitting substrate 8b, and a liquid crystal layer (not shown) sandwiched between the two substrates. A driver IC 7 for driving the liquid crystal cell 1 is mounted on the lower side of the lower translucent substrate 8b in the figure. The liquid crystal cell 1 is sandwiched between polarizing plates (not shown) to form a liquid crystal panel. Reflecting portions 3b and 3a are provided in the vicinity of the right side and the upper side of the upper transparent substrate 8a of the liquid crystal cell 1. The reflecting portions 3a and 3b are formed of a rod-like transparent member having a right triangle shape in cross section. The reflectors 3a and 3b receive the emitted light emitted from the planar light source 2 from its right side, totally reflect on the inclined surface, and emit as parallel light 6a and 6b from the other right side.

  In the vicinity of the left side and the lower side of the upper transparent substrate 8a of the liquid crystal cell 1, light receiving portions 4a and 4b are installed. Each of the light receiving portions 4a and 4b includes a plurality of second light receiving portions (not shown) and a plurality of light receiving elements 14a and 14b. As the light receiving elements 14a and 14b, photodiodes or phototransistors can be used. In FIG. 1B, ten light receiving elements 14a and 14b are arranged. The light receiving unit 4a transmits the parallel light 6a reflected from the reflecting unit 3a through a second liquid crystal shutter (not shown), and the light receiving unit 4b receives the parallel light 6b reflected from the reflecting unit 3b. Light is transmitted through the shutter. When the operator moves a finger, a pen or the like near the surface of the liquid crystal cell 1 to block the parallel light 6a, 6b, the output of the light receiving elements 14a, 14b corresponding to the blocked parallel light 6a, 6b changes. Arise. This is detected by a position detection circuit (not shown), and the coordinates of the blocked position are specified. In this way, the operator can input information from the display surface.

  Although the reflecting members 3a and 3b are rod-like members having a regular triangle cross section, they may be separately provided corresponding to the light receiving elements 14a and 14b of the corresponding light receiving portions 4a and 4b.

  Furthermore, as shown in FIG. 2, lenses (22 and 23) can be provided on the incident surfaces or the exit surfaces of the reflecting portions 3a and 3b so that the parallel lights 6a and 6b are not diffused. In general, the emitted light 5a emitted from the planar light source 2 is diffused light. Therefore, it is preferable to install a rod-shaped collimator lens between the planar light source 2 and the reflecting portion 3a to convert it into parallel light. The reflecting portions 3a and 3b can be formed by injection molding using a transparent synthetic resin made of acrylic or polycarbonate. A lens function can be imparted simultaneously with the injection molding. The shape of the lens may be spherical or cylindrical. Moreover, since the cross-sectional area of the parallel light is determined by the size of the liquid crystal shutter, it can be made smaller than the size of the light receiving element. For this reason, the position of the pen tip on the screen is also correctly detected.

  The light emitted from the planar light source 2 is restricted by the first slit 19a, and the reflected light 15a reflected from the second reflecting portion 9a is restricted by the second slit 19b. Thereby, the noise light incident from the planar light source 2 or the outside can be removed.

  Transparent glass is used as the filter substrate 18. As the first slit 19 a and the second slit 19 b formed on the filter substrate 18, a polymer film or a metal film that blocks light by mixing a black pigment or the like can be used. Further, a color filter layer can be formed in the display area of the filter substrate 18 so that the image displayed on the liquid crystal cell 1 can be colored. In this case, the upper light-transmitting substrate 8a is interposed between the surface of the liquid crystal layer as the display surface and the filter substrate 18. The upper translucent substrate 8a usually has a thickness of 0.2 mm to 0.5 mm. For this reason, when one pixel displayed on the liquid crystal layer and one pixel of the color filter on the filter substrate 18 are viewed obliquely, a shift is likely to occur. Therefore, it is preferable to make the outer shape of the pixel relatively large.

  The light scanning frequency, that is, the driving frequency of the first and second liquid crystal shutters is a frequency obtained by removing the frequency of commercial power, the scanning frequency of the liquid crystal cell 1 or an integer multiple thereof. Accordingly, the position detection circuit 48 can exclude light from outside light and light emitted from the liquid crystal panel 12, and can suppress occurrence of position detection failure due to noise light.

  The frequency of commercial power can be 50 Hz and 60 Hz. Since a fluorescent lamp or the like emits light with commercial power of 100 V, these frequency components are included in the ambient light on the touch panel.

It is a figure for demonstrating the optical touch panel which concerns on this invention. It is a typical sectional view of the optical touch panel concerning the present invention. It is a figure for demonstrating the optical touch panel which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal cell 2 Planar light source 3a, 3b Reflection part 4a, 4b Light reception part 5a, b Output light 6a, b Parallel light 7 Driver IC
8a Upper translucent substrate 8b Lower translucent substrate 9a Second reflective portion 10 Optical touch panel

Claims (5)

A liquid crystal cell having a rectangular surface;
A planar light source installed on the back surface of the liquid crystal cell for irradiating the liquid crystal cell with light;
A first reflecting portion that receives light emitted from the planar light source installed along one side of the liquid crystal cell and reflects the light in a direction parallel to the surface of the liquid crystal cell;
A light receiving portion disposed along the other side of the liquid crystal cell;
With
The light receiving unit receives the light reflected from the first reflecting unit, converts the light into an electrical signal, and further reflects the light reflected from the reflecting unit, and the second reflecting unit. A plurality of light receiving elements that receive the light reflected from the part and convert it into an electrical signal,
The liquid crystal cell blocks and transmits light between the plurality of first liquid crystal shutters that can block and transmit light between the planar light source and the light receiving unit, and light between the second reflecting unit and the light receiving unit. A plurality of second LCD shutters that can
The first reflecting portion and the second reflecting portion are formed on the surface of the translucent substrate, and the plurality of light receiving elements are formed on the back surface of the translucent substrate, and from the second reflecting portion An optical touch panel, wherein reflected light is received through the liquid crystal shutter.   2. The optical according to claim 1, wherein the plurality of second liquid crystal shutters are controlled to transmit and block at the same timing so as to receive light from the plurality of first liquid crystal shutters. Touch panel.   The plurality of first liquid crystal shutters transmit a light beam from the planar light source in a time-series manner so as to scan at a certain frequency, and a light beam reflected by the first reflection unit is transmitted to the second liquid crystal shutter. An optical touch panel that receives light reflected by the reflecting portion and reflected from the second reflecting portion through the plurality of second liquid crystal shutters.   The optical film for adjusting the direction of the light from the said planar light source is inserted between the said light-receiving part and the said planar light source, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. The optical touch panel as described. A position detection circuit for inputting an electrical signal from the light receiving unit and detecting a position where the light reflected from the reflecting unit to the light receiving unit is shielded,
5. The frequency of the scanning light is superimposed with a frequency of commercial power and a predetermined frequency component excluding the scanning frequency of the liquid crystal cell or an integral multiple of the scanning frequency. The optical touch panel according to any one of the above.

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