LIQUID CRYSTAL DISPLAY WITH BUILT-IN TOUCH SCREEN

• US 20110080358A1
• Filed: 07/12/2010
• Published: 04/07/2011
• Est. Priority Date: 10/06/2009
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Mobile Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: YOSHIMURA, Hideo, JEON, Mu-Kyung, HWANG, Hee-Chul, PARK, Jin-Woo, Kim, Sang-Uk
• Granted Patent: US 8,847,917 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 2203/04106 Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/042 by opto-electronic means
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

A liquid crystal display (LCD) with a built-in touch screen includes: a first substrate including a sensor area having a plurality of photosensors; a second substrate positioned over the first substrate, and including a color filter, a light receiving portion, and a transparent electrode layer and a front polarizing plate; an LCD panel including a liquid crystal layer interposed between the first and second substrates; a touch screen driver circuit to measure a capacitance variation sensed through a first sensing line connected to the transparent electrode layer and to calculate a touch area using optical information sensed through a second sensing line connected to the photosensors when a contact object is in contact with the LCD panel, and to output position information of the contact object, sensed by determining whether a touch occurs and whether a multi-touch occurs using the capacitance variation and the touch area.

Claims

1. A liquid crystal display (LCD) with a built-in touch screen, the LCD comprising:

a first substrate comprising a pixel area having a plurality of pixels to display an image, and a sensor area adjacent to the pixel area and having a plurality of photosensors to sense a position of a contact object;

a second substrate positioned over the first substrate, the second substrate comprising a color filter in an area corresponding to the pixel area on a first surface of the second substrate facing the first substrate, a light receiving portion, onto which external light is incident, in an area of the first surface corresponding to the sensor area, and a transparent electrode layer and a front polarizing plate sequentially stacked on a second surface of the second substrate opposite to the first surface;

an LCD panel comprising a liquid crystal layer interposed between the first and second substrates; and

a touch screen driver circuit to measure a capacitance variation sensed through a first sensing line connected to the transparent electrode layer and to calculate a touch area using optical information sensed through a second sensing line connected to the plurality of photosensors when the contact object is in contact with the LCD panel, and to output position information of the contact object, sensed by determining whether a touch of the contact object on the LCD panel occurs and whether a multi-touch occurs using the measured capacitance variation and the calculated touch area.

2. The LCD as claimed in claim 1, wherein the touch screen driver circuit determines that the touch occurs and outputs the position information of the contact object, sensed using the optical information, when the measured capacitance variation is greater than or equal to a predetermined threshold value.

3. The LCD as claimed in claim 1, wherein, when the calculated touch area includes a plurality of touch points sensed using the optical information, the touch screen driver circuit determines that the multi-touch occurs and outputs the position information of the contact object by selecting some of the sensed touch points when the measured capacitance variation is greater than or equal to a predetermined threshold value and within a multi-touch range and the calculated touch area and the plurality of touch points is included in the multi-touch range.

4. The LCD as claimed in claim 3, wherein the touch screen driver circuit selects the some of the plurality of touch points based on the touch area and/or a light quantity variation.

5. The LCD as claimed in claim 3, wherein the touch screen driver circuit determines a number of sensed touch points to select by comparing the measured capacitance variation to a plurality of multi-touch ranges respectively corresponding to a plurality of numbers of touch points such that the determined number corresponds to the multi-touch range, of the plurality of multi-touch ranges, within which the measured capacitance variation lies.

6. The LCD as claimed in claim 1, wherein the touch screen driver circuit comprises:

a capacitance measurer to measure the capacitance variation provided through the first sensing line;

a touch area calculator to calculate the touch area sensed using the optical information provided through the second sensing line;

a controller to control a control signal to be output by determining whether the touch occurs and whether the multi-touch occurs using the capacitance variation and the touch area; and

a position sensor to output the position information of the contact object according to the control signal received from the controller.

7. The LCD as claimed in claim 6, wherein, when the measured capacitance variation is less than a multi-touch range and greater than or equal to a predetermined threshold value, the controller determines the touch occurs as a single touch and outputs the control signal accordingly.

8. The LCD as claimed in claim 7, wherein the position sensor outputs the position information of the contact object as a single point in response to the control signal when the measured capacitance variation is less than the multi-touch range and greater than or equal to the predetermined threshold value.

9. The LCD as claimed in claim 6, wherein the control signal received by the position sensor includes the optical information, used by the position sensor to determine the position information.

10. The LCD as claimed in claim 6, wherein the position sensor receives the optical information, used by the position sensor to determine the position information, from the touch area calculator.

11. The LCD as claimed in claim 6, wherein the position sensor receives the optical information, used by the position sensor to determine the position information, from the second sensing line.

12. The LCD as claimed in claim 1, further comprising:

a backlight assembly positioned below the LCD panel to provide light to the LCD panel,

wherein a light shielding layer to prevent the provided light from being incident directly onto the plurality of photosensors is provided on a surface of the first substrate corresponding to the sensor area.

13. The LCD as claimed in claim 1, wherein, when the calculated touch area includes a plurality of touch points sensed using the optical information, the touch screen driver circuit determines the touch occurs as a single touch and outputs the position information of the contact object by selecting one of the sensed touch points when the measured capacitance variation is greater than or equal to a predetermined threshold value and less than a multi-touch range.

14. The LCD panel as claimed in claim 13, wherein the touch screen driver circuit selects the one sensed touch point that is broader than other sensed touch points in the touch area.

15. The LCD panel as claimed in claim 13, wherein the touch screen driver circuit selects the one sensed touch point that has a greater capacitance variation than other sensed touch points in the touch area.

16. A liquid crystal display (LCD) with a built-in touch screen, the LCD comprising:

a first substrate comprising a pixel area having a plurality of pixels to display an image, and a sensor area adjacent to the pixel area and having a plurality of photosensors to sense a position of a contact object;

a second substrate positioned over the first substrate, the second substrate comprising a transparent electrode layer;

an LCD panel comprising a liquid crystal layer interposed between the first and second substrates; and

a touch screen driver circuit to measure a capacitance variation sensed through a first sensing line connected to the transparent electrode layer and to calculate a touch area using optical information sensed through a second sensing line connected to the plurality of photosensors when the contact object is in contact with the LCD panel, and to output position information of the contact object, sensed by determining whether a touch of the contact object on the LCD panel occurs and whether a multi-touch occurs using the measured capacitance variation and the calculated touch area.

17. The LCD as claimed in claim 16, wherein the touch screen driver circuit determines that the touch occurs and outputs the position information of the contact object, sensed using the optical information, when the measured capacitance variation is greater than or equal to a predetermined threshold value.

18. The LCD as claimed in claim 16, wherein, when the calculated touch area includes a plurality of touch points sensed using the optical information, the touch screen driver circuit determines that the multi-touch occurs and outputs the position information of the contact object as the plurality of touch points when the measured capacitance variation is greater than or equal to a predetermined threshold value.

19. The LCD as claimed in claim 16, wherein, when the calculated touch area includes a plurality of touch points sensed using the optical information, the touch screen driver circuit determines the touch occurs as a single touch and outputs the position information of the contact object by selecting one of the sensed touch points when the measured capacitance variation is greater than or equal to a predetermined threshold value and less than a multi-touch range.

20. A touch screen driver circuit of a liquid crystal display (LCD) with an LCD panel, a plurality of photosensors on a first substrate to sense a position of a contact object in contact with the LCD panel, and a transparent electrode layer on a second substrate, the touch screen driver circuit comprising:

a capacitance measurer to measure a capacitance variation provided through a first sensing line connected to the transparent electrode layer;

a touch area calculator to calculate a touch area using optical information provided through a second sensing line connected to the plurality of photosensors when the contact object is in contact with the LCD panel;

a controller to control a control signal to be output by determining whether a touch occurs and whether a multi-touch occurs using the measured capacitance variation and the calculated touch area; and

a position sensor to output position information of the contact object according to the control signal received from the controller.

21. The touch screen driver circuit as claimed in claim 20, wherein the controller determines that the touch occurs and the position sensor outputs the position information of the contact object, sensed using the optical information, when the measured capacitance variation is greater than or equal to a predetermined threshold value.

22. The touch screen driver circuit as claimed in claim 20, wherein, when the calculated touch area includes a plurality of touch points sensed using the optical information, the controller determines that the multi-touch occurs and the position sensor outputs the position information of the contact object as the plurality of touch points when the measured capacitance variation is greater than or equal to a predetermined threshold value.

23. The touch screen driver circuit as claimed in claim 20, wherein, when the calculated touch area includes a plurality of touch points sensed using the optical information, the controller determines the touch occurs as a single touch and the position sensor outputs the position information of the contact object by selecting one of the sensed touch points when the measured capacitance variation is greater than or equal to a predetermined threshold value and less than a multi-touch range.

24. The touch screen driver circuit as claimed in claim 20, wherein the control signal received by the position sensor includes the optical information, used by the position sensor to determine the position information.

25. The touch screen driver circuit as claimed in claim 20, wherein the position sensor receives the optical information, used by the position sensor to determine the position information, from the touch area calculator.

26. The touch screen driver circuit as claimed in claim 20, wherein the position sensor receives the optical information, used by the position sensor to determine the position information, from the second sensing line.