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Patent Issued for Liquid Crystal Display Having a Built-In Touch Screen Using Capacitance and Optical Information for Detecting a Touch Position

May 7, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- Samsung Display Co., Ltd. (Yongin-si, KR) has been issued patent number 8704784, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Park, Jin-Woo (Yongin, KR); Kim, Sang-Uk (Yongin, KR); Hwang, Hee-Chul (Yongin, KR); Jeon, My-Kyung (Yongin, KR); Yoshimura, Hideo (Yongin, KR).

This patent was filed on July 12, 2010 and was published online on April 22, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "Aspects of the present invention relate to a liquid crystal display (LCD) with a built-in touch screen, and more particularly, to an LCD with a built-in touch screen of a photosensor type, which has an operational reliability improved by combining a capacitance type with the photosensor type.

"A touch screen is provided on a front face of an image display device so that a user can select an instruction content displayed on a screen of the image display device using a user's hand or an object. The touch screen is in direct contact with the user's hand or the object. The touch screen senses a contact position, and the image display device receives a content instructed at the contact position as an input signal so as to be driven based on the input signal.

"An image display device having a touch screen does not require a separate input device (such as a keyboard or mouse) connected to the image display device to operate. Hence, its application fields have been gradually extended. Recently, touch screens have been widely used in liquid crystal displays (LCDs). An LCD having a touch screen includes an LCD panel to display images and a touch screen panel positioned over the LCD panel to sense position information through a touch input from a user. At this time, a frame or adhesive is used to allow the touch screen panel to be positioned over the LCD panel, in which an air layer is formed between the LCD panel and the touch screen panel. In this case, a layer having a different refractive index from those of the LCD panel and the touch screen panel is formed between the LCD panel and the touch screen panel, and therefore, the optical characteristic of the entire LCD is deteriorated. Furthermore, since a separate touch screen panel is manufactured and then attached to the LCD panel, manufacturing cost is raised, and the thickness of the LCD is increased. Therefore, to solve such and/or other problems, an LCD with a built-in touch screen implemented by integrating a touch screen panel and an LCD panel is required.

"Meanwhile, a photosensor or the like may be used to sense position information through a touch input from a user. In this case, a touch position is sensed by distinguish a portion covered by a contact object (such as a finger or touch stick) from a portion onto which external light is incident through the photosensor.

"However, in the case of the touch screen of a photosensor type, if the illuminance of external light is low, a difference in illuminance between a portion onto which the external light is incident through a photosensor and a portion covered by a contact object is slight when a touch occurs. Therefore, the recognition rate of the touch may be lowered. On the other hand, if the illuminance of the external light is high, the portion onto which the external light is incident and the portion covered by the contact object are almost recognized as black and white when the touch occurs. Hence, the photosensor may erroneously recognize a shadow as a touch even when a user's finger or object is not touching a touch screen panel, but is located over the touch screen panel. Therefore, operational reliability may be lowered.

"Accordingly, there is a need to secure the operational reliability of the touch screen by precisely recognizing a touch event."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "Aspects of the present invention provide a liquid crystal display (LCD) with a built-in touch screen of a photosensor type, which has photosensors provided in an LCD panel and has an operational reliability improved by combining a capacitance type with the photosensor type.

"According to an aspect of the present invention, there is provided an LCD with a built-in touch screen, the LCD including: a first substrate including 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 including 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 including a liquid crystal layer interposed between the first and second substrates; and a touch screen driver circuit to sense a capacitance variation provided through a first sensing line connected to the transparent electrode layer when an object is in contact with the LCD panel, and to output position information of the contact object, sensed by using optical information sensed through a second sensing line connected to the plurality of photosensors when the capacitance variation is greater than or equal to a predetermined threshold value.

"The touch screen driver circuit may include a controller to determine determining whether a touch of the contact object on the LCD panel, using the capacitance variation provided through the first sensing line, and to output the optical information provided through the second sensing line when the touch occurs; and a position sensor to output the position information of the contact object, sensed by using the optical information provided from the controller.

"The touch screen driver circuit may include a controller to determine whether a touch of the contact object on the LCD panel occurs, using the capacitance variation provided through the first sensing line, and outputting a control signal according to whether the touch occurs; and a position sensor driven in response to the control signal provided from the controller to output the position information of the contact object, sensed by using the optical information sensed through the second sensing line.

"The touch screen driver circuit may include a controller to determine whether a touch of the contact object on the LCD panel occurs, using the capacitance variation provided through the first sensing line, and outputting a control signal according to whether the touch occurs; a position sensor to output the position information of the contact object, sensed by using the optical information sensed through the second sensing line; and a switch to selectively output the position information of the contact object, received from the position sensor, in response to the control signal, received from the controller.

"The LCD may further include a back light 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 may be provided on a surface of the first substrate corresponding to the sensor area

"The plurality of pixels may be arranged in pixel units, each pixel unit having pixels respectively corresponding red , green (G) and blue (B).

"A ratio of a number of the plurality of photosensors to a number of the pixel units may be 1:1 or less.

"According to another aspect of the present invention, there is provided a liquid crystal display (LCD) with a built-in touch screen, the LCD including: a first substrate including 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 including a transparent electrode layer; an LCD panel including a liquid crystal layer interposed between the first and second substrates; and a touch screen driver circuit to sense a capacitance variation provided through a first sensing line connected to the transparent electrode layer when the contact object is in contact with the LCD panel, and to output position information of the contact object, sensed by using optical information sensed through a second sensing line connected to the plurality of photosensors when the capacitance variation is greater than or equal to a predetermined threshold value.

"According to another aspect of the present invention, there is provided 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 including: a controller to sense a capacitance variation provided through a first sensing line connected to the transparent electrode layer when the contact object is in contact with the LCD panel; and a position sensor to output position information of the contact object, sensed by using optical information sensed through a second sensing line connected the plurality photosensors when the capacitance variation is greater than or equal to a predetermined threshold value.

"According to aspects of the present invention, an LCD with a built-in touch screen of a photosensor type is implemented by providing photosensors on a lower substrate of an LCD panel, thereby improving optical characteristics of the LCD, improving its manufacturing cost, and providing a thin LCD. Furthermore, it is precisely determined whether or not a touch event occurs through a capacitance type using a transparent electrode layer formed on the front face of the LCD panel, thereby improving an operational reliability of the LCD with the built-in touch screen.

"Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention."

For the URL and additional information on this patent, see: Park, Jin-Woo; Kim, Sang-Uk; Hwang, Hee-Chul; Jeon, My-Kyung; Yoshimura, Hideo. Liquid Crystal Display Having a Built-In Touch Screen Using Capacitance and Optical Information for Detecting a Touch Position. U.S. Patent Number 8704784, filed July 12, 2010, and published online on April 22, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=64&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=3193&f=G&l=50&co1=AND&d=PTXT&s1=20140422.PD.&OS=ISD/20140422&RS=ISD/20140422

Keywords for this news article include: Samsung Display Co. Ltd.

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Source: Journal of Engineering