News Column

Patent Issued for Liquid Crystal Display Device and a Method of Manufacturing the Same

August 5, 2014



By a News Reporter-Staff News Editor at China Weekly News -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventors Koito, Takeo (Kanagawa, JP); Noguchi, Koji (Kanagawa, JP), filed on August 3, 2009, was published online on July 22, 2014.

The patent's assignee for patent number 8786571 is Japan Display West Inc. (Aichi, JP).

News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates to a liquid crystal display device, having a touch sensor function, in which one of two sensor electrodes is disposed across a liquid crystal enclosed between first and second substrates from the other thereof, and a method of manufacturing the same.

"A liquid crystal display device has advantages such as thinning, weight saving, and low power consumption. For this reason, the liquid crystal display device is applied to a large number of electronic apparatuses for mobile applications such as a mobile phone and a digital camera.

"The liquid crystal display device has a liquid crystal panel in which a liquid crystal is enclosed between a pair of substrates. In the liquid crystal display device, a light radiated from a planar surface light source such as a backlight provided on a back surface of the liquid crystal panel is modulated by the liquid crystal panel. Also, the display of an image is carried out on a front surface (a side of viewing a display surface) of the liquid crystal panel by the modulated light.

"In recent years, a liquid crystal display device having a sensor function called 'a touch panel' with which data representing contents instructed by a user is directly inputted by utilizing an icon or the like displayed on a screen of the liquid crystal display device has been realized.

"The touch panel is installed on the display surface side of the liquid crystal display device so that the instructed contents shown on the screen of the liquid crystal display device can be selected with a hand of a human being or an object (for example, a stylus pen). When the hand of the human being or the object directly touches the touch panel, the touch panel detects a position within the panel surface which the hand of the human being or the object touches. The liquid crystal display device receives the instructed contents in the form of an input signal in accordance with the position where the contact is detected, and carries out an operation based on the input signal.

"When the liquid crystal display device including the touch panel is used in a computer or the like, there is no need for providing an input unit as an attached accessory, outside a main body and a display device, such as a keyboard or a mouse. Alternatively, the touch panel provides another input unit which assists such an input unit. In addition, when the touch panel is used in a mobile product such as a mobile phone, there is no need for providing an input unit such as a keypad, or the number of keys is reduced.

"From the above, when the touch panel is mounted to the liquid crystal display device, the number of special attached accessories is reduced. For the product provider side, when the number of attached accessories is less, there is provided an advantage that the degree of freedom of the product design increases, and thus the miniaturization and the convenience enhancement are progressed, thereby increasing the product power. This provides the advantages such as the price-reduction, high functionality and convenience enhancement of the product for the user side as well. For this reason, the use of the touch panel has a tendency to increase yearly.

"A liquid crystal display device in which a touch panel is added to a display surface side of a liquid crystal display panel is known in terms of a method of mounting the touch panel.

"However, it is disadvantageous to the thinning of the display device that the touch panel is externally added, which becomes a primary factor of an increase in manufacturing cost. In addition, in the liquid crystal display device to which the touch panel is externally added, the optical characteristics in a phase of image display changes due to an influence of a refractive interface, so that the visibility of the image is reduced. For this reason, it is studied that the liquid crystal display panel and the touch panel are formed integrally with each other.

"A resistance film system, an electrostatic capacitance system, and an optical system are known as a detection system in the touch panel. Of these systems, in the touch panel utilizing the resistance film system, one point detection is a principle. Thus, the use of the application of the touch panel utilizing the resistance film system is limited.

"It is studied in the systems to form the liquid crystal display panel and the touch panel integrally with each other.

"In particular, when the liquid crystal display panel and the touch panel are formed integrally with each other in the resistance film system, a pixel array drive wiring for display can be effectively used as a wiring as well for detection of a change in resistance. Therefore, the resolution for display is prevented from being reduced, and the precision of position detection by a sensor is high. Also, an additional function such as a multi-point detecting function can be obtained.

"There is known a liquid crystal display device, with a touch sensor, in which paired electrodes (hereinafter referred to as either 'first and second sensor electrodes' or 'touch electrodes') which contact each other when the user presses a panel surface with his/her finger or the like are formed on two substrates, respectively, through which a liquid crystal layer is sandwiched for the purpose of forming the liquid crystal display panel and the touch panel integrally with each other in the resistance film system. This liquid crystal display device, for example, is described in Japanese Patent Laid-open No. 2001-75074.

"In the liquid crystal display device having the touch sensor function utilizing the resistance film system and having the structure as described above, the two sensor electrodes need to be formed contactably each other so as to hold the liquid crystal layer between the two sensor electrodes.

"In general, however, the liquid crystal layer is located so as to contact an alignment film for determining an alignment direction of a liquid crystal molecule. For this reason, in order to apply the structure described above, the first and second sensor electrodes are obliged to contact the alignment film with the alignment film being held between the first and second sensor electrodes. For this reason, since a part of the alignment film which the first and second sensor electrodes contact is shaved, and as a result, there is a possibility that the imperfect alignment is caused, or the alignment film shaved floats in the liquid crystal to cause the imperfect display. Therefore, in the liquid crystal display device, utilizing the resistance film system, having such a structure, it is feared from the reason described above that the display grade can not be maintained by repetitively using the touch sensor.

"There is known a liquid crystal display devices, having the touch sensor function utilizing the resistance film system, in which in order to avoid such inconvenience, a portion of an alignment film which sensor electrodes contact is removed. This liquid crystal display devices, for example, is described in Japanese Patent Laid-open No. 2007-52368."

As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "Japanese Patent Laid-open No. 2007-52368 discloses the technique with which during the manufacture of the liquid crystal display device having the touch sensor function and utilizing the resistance film system, a solvent is locally applied from a minute nozzle used in ink jet to the alignment film to dissolve the local portion of the alignment film, thereby exposing a surface of the touch electrode.

"However, in the case of adoption of such a process, the throughput is estimated to be low, and thus the manufacturing cost increases. In addition, it is difficult to perfectly, locally remove the alignment film deposited once, and thus reduction of the yield is feared. Also, the application of the ink jet technique means that it is necessary to invest in normal equipment. Thus, the manufacturing cost increases in terms of this respect.

"Moreover, with the technique for locally applying the solvent, it is feared to suppose that the alignment film is partially dissolved even in the circumference of the touch electrode the surface of which is desired to be exposed. Thus, since a margin is required in terms of an area so as to prevent the removal of the alignment film from exerting an influence on the display, an extra area other than the area substantially contributing to the display increases within a pixel. This, for example, gives the same disadvantage as that in the case where an aperture ratio (a rate at which a light transmitting portion occupies a pixel area) in a transmission type liquid crystal display device is reduced. For this reason, an increase in area margin due to the removal of the alignment film results in the high possibility that the disadvantage of the reduction of a luminance of the picture is provided.

"The present invention has been made in the light of the circumstances described above, and it is therefore desirable to provide a highly reliable liquid crystal display device which requires no process resulting in an increase in manufacturing cost, which has a high sensitivity, and with which a touch sensor function utilizing a resistance film system is provided integrally so as not to exert an influence on a display performance, and a method of manufacturing the same.

"In order to attain the desire described above, according to an embodiment of the present invention, there is provided a liquid crystal display device including: a first substrate on a display surface side; a second substrate on a back surface side; a liquid crystal layer formed between the first and second substrates; an alignment film formed on one of the first and second substrates so as to contact the liquid crystal layer; a first sensor electrode formed on a surface, of the alignment film, contacting the liquid crystal layer; and a second sensor electrode formed on the other of the first and second substrates, and adapted to either contact or approach the first sensor electrode when the first substrate is pressed from the display surface side.

"With the structure described above, the first sensor electrode is formed on one of the first and second substrates through the alignment film. The alignment film is a base film for the first electrode, and thus the surface of the first sensor electrode is not covered with the alignment film. In addition, the second sensor electrode is disposed in the position, where the second sensor electrode faces the first sensor electrode with the liquid crystal layer being held between the first and second electrodes, on the side of the other of the first and second electrodes.

"When one of the first and second electrodes on the display surface side is pressed in this state, the one of the first and second electrodes is bent by application of an external pressure. When the one of the first and second electrodes is bent by application of the external pressure, the first sensor electrode contacts the second sensor electrode, and as a result, a potential of at least one of the first and second sensor electrodes changes from that before the contact. Or, since the first sensor electrode approaches the second sensor electrode although the first sensor electrode does not come to contact the second sensor electrode, an electrical change, for example, a capacitance change occurs between the first sensor electrode and the second sensor electrode. Such an electrical change is drawn to the outside to be detected, or is detected by a built-in detecting section, whereby the position where the one of the first and second substrates is pressed is detected.

"With regard to the more detailed structure, it is possible to adopt a structure in which the second sensor electrode is also used as a pixel electrode (first structure), the case where detection areas different from pixels are disposed in accordance with a predetermined rule (second structure), and the case where the second sensor electrode different from the pixel electrode is disposed within the pixel (third structure). Also, it is possible to adopt the case where the first sensor electrode and the second sensor electrode are formed lengthwise in directions perpendicularly intersecting with each other in long patterns common to a plurality of pixels, and a resistance change due to the contact is read out (fourth structure).

"According to another embodiment of the present invention, there is provided a method of manufacturing a liquid crystal display device including: a first step of forming a predetermined functional film on a first substrate; a second step of forming a predetermined functional film on a second substrate; and a third step of disposing the first substrate and the second substrates on a display surface side and on a back surface side, respectively, to fix the first substrate and the second substrates to a panel frame, and injecting a liquid crystal between the first substrate and the second substrates to seal the liquid crystal between the first substrate and the second substrates. The second step includes the step of forming a second sensor electrode on a partial area of the second substrate. The first step includes the steps of: forming an alignment film on the first substrate; forming a first sensor electrode on a partial area on the alignment film in a position where the first sensor electrode faces the second sensor electrode through a layer of the liquid crystal formed in the third step; and rubbing the alignment film in one direction in a state in which the first sensor electrode is formed.

"According to the present invention, it is possible to provide the highly reliable liquid crystal display device which requires no process resulting in the increase in manufacturing cost, which has a high sensitivity, and with which the touch sensor function utilizing the resistance film system is provided integrally so as not to exert the influence on the display performance, and the method of manufacturing the same."

For additional information on this patent, see: Koito, Takeo; Noguchi, Koji. Liquid Crystal Display Device and a Method of Manufacturing the Same. U.S. Patent Number 8786571, filed August 3, 2009, and published online on July 22, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8786571.PN.&OS=PN/8786571RS=PN/8786571

Keywords for this news article include: Asia, Japan Display West Inc.

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Source: China Weekly News


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