The present application claims priority from Japanese Patent Application JP 2013-54519 filed on Mar. 18, 2013, the content of which is hereby incorporated by reference into this application.
The present invention relates to a display device, and more particularly to a display device including a protective plate provided in the front surface of a display panel to protect the display panel.
In portable information terminals such as a mobile phone with a liquid crystal display device as a display device, the liquid crystal display device is formed by a liquid crystal display panel and a backlight device for emitting illumination light to the liquid crystal display panel. In general, the display device has a module structure in which a protective plate (front window) is fixed to the front surface (observer side surface) of the liquid crystal display device to protect the liquid crystal display panel formed of a glass substrate.
In the display device with the module structure, a frame-like light shielding film is printed on the back surface of the protective plate, namely, on the surface facing the liquid crystal display panel so as to surround the display area of the liquid crystal display panel. In particular, in order to prevent leakage of illumination light emitted from the backlight device to the outside from the periphery of the liquid crystal display module, the back surface of the protective film is recoated with the light shielding film to improve the light shielding performance.
Further, in the liquid crystal display module with this configuration, the protective plate is fixed to the liquid crystal display panel by an adhesive of thermosetting resin or photocurable resin. In this case, the adhesive is dropped on the front surface of the liquid crystal display panel, and the protective plate is placed on the top surface of the adhesive. Then, the adhesive is cured to form an adhesive layer between the liquid crystal display panel and the protective plate. In this way, the protective plate is fixed to the liquid crystal display panel.
However, the back surface of the protective plate has a difference in level due to the printing of the light shielding film. This leads to a problem that bubbles are generated in the step portion when the adhesive is applied over the back surface of the protective film, and thus the product quality is significantly reduced.
As a method for solving this problem, for example, there is a display device described in Japanese Unexamined Patent Application Publication No. 2011-7830. In the display device described in Japanese Unexamined Patent Application Publication No. 2011-7830, when the light shielding film is formed by recoating, the light shielding film is printed to form a step on the inner peripheral side of the light shielding film, to reduce the difference in level between the area where the light shielding film is not formed and the area recoated with the light shielding film, in order to prevent bubbles from forming in the step portion.
In recent years, there has been a significant increase in the number of display pixels in the portable information terminal in order to improve the display quality of the liquid crystal display device in a housing of a limited size. At the same time, it is desirable to reduce the peripheral portion of the display area, which does not contribute to image display, a so-called narrow frame. It is also desirable to make the liquid crystal display device thinner while further increasing the transmittance. In order to achieve these requirements, the film thickness of the adhesive layer is made very thin with a very small amount of adhesive applied to bond the liquid crystal display panel and the protective plate.
In particular, as shown in
The present invention has been made in view of the above problems, and an object of the present invention is to provide a display device that can prevent bubbles from forming also in the corner portion of the light shielding film printed on the protective plate.
To solve the above problems, the present invention provides a display device including: a display panel; a protective plate provided in a front surface of the display panel to protect the display panel; and a light shielding film formed along a peripheral portion of the protective plate. The protective plate is fixed to the front surface of the display panel by a transparent adhesive that is applied to an area between the display panel and the protective plate.
The light shielding film is formed so as to surround a display area of the display panel. The light shielding film includes a first light shielding film formed in a frame shape, and a second light shielding film deposited on the first light shielding film.
The second light shielding film has a cut-out portion where the second light shielding film is not formed in at least one or more corner portions of the protective plate.
A concave portion is formed in the corner portion of the light shielding film from an inner peripheral edge to an outer peripheral edge.
According to the present invention, it is possible to prevent bubbles from forming also in the corner portion of the light shielding film printed on the protective plate.
These and other advantages of the present invention will be apparent from the description of the present specification.
Hereinafter, embodiments to which the present invention is applied will be described with reference to the accompanying drawings. However, the same components are identified by the same reference numerals and the repetitive description thereof will be omitted in the following description.
(Overall configuration)
As shown in
For example, the liquid crystal display panel is configured such that a first substrate (TFT substrate) in which a thin film transistor and the like are formed as described below, and a second substrate (color filter substrate (CF substrate)) in which color filters of red (R), green (G), and blue (B) are formed corresponding to the pixels, are arranged to face each other with a liquid crystal interposed therebetween. The first substrate includes multiple image signal lines (drain lines), not shown, extending in the long side direction in the figure, as well as multiple scan signal lines (gate lines) extending in the short side direction. An area surrounded by the drain lines and the gate lines forms a pixel area. Further, a thin film transistor, which is turned on and off by the scan signal from the gate line, is provided in the vicinity of the intersection of the drain and gate lines. When the thin film transistor is turned on, an image signal from the drain line connected to the drain electrode is output to the pixel electrode connected to the source electrode. The second substrate is configured such that the RGB color filters, each of which corresponds to each pixel, form unit pixels for color display. Further, at least one side of the second substrate is made smaller than the first substrate. Then, a known flexible wiring substrate for inputting image signals from the outside, as well as a drive circuit for generating image signals and scan signals are mounted on the opposite surface of the first substrate that is exposed from the second substrate. In other words, the flexible wiring substrate and the drive circuit are mounted on the surface on the side of the liquid crystal display layer.
In the liquid crystal display panel with this configuration, the second substrate is provided on the side of the image display surface, namely, on the side of the observer. Thus, in the liquid crystal display device according to the first embodiment, the protective plate FW is bonded to the surface of the second substrate. In the bonding between the display panel PNL and the protective plate FW according to the first embodiment, for example, a predetermined amount of adhesive (for example, a translucent adhesive of a known thermosetting resin) AD is dropped on the front surface of the display panel PNL at multiple locations corresponding to the display area AR in a matrix. Then, the protective plate FW on which the light shielding film PM is printed is deposited on top surface to spread the adhesive AD between them. Then, the adhesive AD is heated and cured to cover the front surface of the display panel PNL by the layer of the transparent adhesive AD, while fixing the protective plate FW to the display panel PNL. At this time, the protective plate FW and the display panel PNL are bonded so that the adhesive AD is not applied to the drive circuit and the connection terminal portion.
In the protective plate FW provided (bonded) to the front surface of the display panel PNL, the frame-like light shielding film PM is formed by screen printing along the peripheral edge of the protective plate FW, which will be described in detail below. Further, the light shielding film PM is formed so as to surround the display area AR of the display panel PNL. Note that the formation method of the light shielding film PM is not limited to screen printing. Other printing techniques and formation techniques such as vapor deposition may be used.
The light shielding film PM according to the first embodiment is formed by two layers of the light shielding films PM1, PM2 with different outer shapes as described in detail below. With this configuration, even if the cause of the leakage of light, such as backlight beam, occurs due to the formation of a pinhole and the like on one light shielding film, the other light shielding film can prevent the light leakage. At this time, the light shielding film PM according to the first embodiment is configured such that the first light shielding film PM1, which is one of the light shielding films, has a frame-like outer shape that is circularly printed along the peripheral edge of the protective plate FW. Further, the second light shielding film PM2, which is the other light shielding film, is formed by four linear films along each of the peripheral edges of the protective plate FW. The linear light shielding films are separated from each other in each of the corner portions.
In other words, in the configuration of the light shielding film PM according to the first embodiment, the first light shielding film PM1 is formed around the display area AR of the display panel PNL, similarly to the conventional light shielding film. The second light shielding film PM2, which is formed on the top surface of the first light shielding film PM1, is formed in the side edge except the area of the corner portions of the protective film FW. In other words, the second light shielding film PM2 is formed in the side edge, which is the area except the area of the corner portions of the top surface of the first light shielding film PM1.
As a result, in the second light shielding film PM2 according to the first embodiment, a cut-out area RM, which is the area where the second light shielding film PM2 is not formed (printed), is formed in each corner portion of the protective plate FW. Note that each of the linear light shielding films forming the second light shielding film PM2 is also referred to as the second light shielding film PM2 in the following description.
(Detailed Configuration of the Light Shielding Film)
Next,
In general, when the light shielding film PM is formed (printed) by screen printing, the edge on the print end side is raised from the printed surface. In other words, a concave portion is formed in the normal line direction of the printed surface. Here, in the liquid crystal display device according to the first embodiment, the light shielding film PM is formed by printing a light shielding material (black paint, and the like) from the left side to the right side in
Thus, in the difference in level between the area where the light shielding film PM is not printed (the opening area) and the area where the light shielding film PM is formed, the edge on the side of the display area AR is the print end side in the light shielding film PM formed along the side edge on the left side in
As is apparent from
In the cut-out area RM where the second light shielding film PM2 is not formed, as is apparent from
In other words, as shown in
In particular, in the configuration of the light shielding film PM according to the first embodiment, the cut-out area RM, which is the area where the second light shielding is removed, is formed in all four corner portions of the protective plate FW. With this configuration, the adhesive AD can easily flow into the four corner portions, namely, the four corners of the protective plate FW. This makes it possible to reduce the bubble formation and the squeeze-out of the adhesive AD at the same time. As a result, it is possible to significantly reduce operations such as repair of the display device associated with a defective product due to the bubble formation and the squeeze-out of the adhesive AD. Thus, the yield and workability can be improved.
In the side portion of the light shielding film PM according to the first embodiment, the light shielding film PM is configured such that the first light shielding film PM1 and the second light shielding film PM2 are formed along the side portion of the protective plate FW. In other words, as shown in
Further, as shown in
In particular, the first light shielding film PM1 according to the first embodiment has a thickness with sufficient light shielding performance to block the light, such as the backlight beam, only by the first light shielding PM1. Note that the second light shielding film PM2 is the light shielding film for preventing the cause of the reduction in the light shielding performance due to the pinhole and the like formed in the first light shielding film PM1. Thus, in the configuration according to the first embodiment, the film thickness of the second light shielding film PM2 is smaller than the film thickness of the first light shielding film PM1. However, it is also possible that the first light shielding film PM1 and the second light shielding film PM2 have the same film thickness, or the film thickness of the second light shielding film PM2 is greater than the film thickness of the first light shielding film PM1.
Further, as is apparent from
In other words, in the corner portion of the display device according to the first embodiment, the adhesive AD can be accumulated more than in the side portion by the volume corresponding to the second light shielding film PM2. As a result, the amount of the adhesive AD applied to the vicinity of the corner portion can be increased more than the conventional one. Thus, the formation of bubbles can be prevented more effectively. Further, a greater amount of adhesive AD can be accumulated, so that the amount of adhesive AD squeezed out of the peripheral portion can be significantly reduced. As a result, when the display device according to the first embodiment is used in a portable information terminal such as a mobile phone, the peripheral portion called a bezel of the particular mobile information terminal can be made thin (narrow).
Note that in the display device according to the first embodiment, the second light shielding film PM2 is continuously formed from one corner portion to the other corner portion along the side portion of the protective plate FW. However, the present invention is not limited to the exemplary embodiment. For example, one or more areas where the second light shielding film PM2 is not formed may be formed at least along the side portion of the protective plate FW. It is also possible to form the second light shielding film PM2 in dotted lines.
Also in the display device according to the second embodiment, similarly to the first embodiment, the drive circuit of the liquid crystal display panel is mounted on the lower edge of the display panel not shown (on the lower side of the display panel in the figure). Then, the flexible wiring substrate is connected to the drive circuit to input control signals. At this time, the width of the light shielding film PM formed along the lower peripheral portion, which is the side on which the drive circuit and other components are mounted, is made larger than the width of the light shielding film PM formed along the other three peripheral portions. However, it is also possible that the width of the long sides of the light shielding film PM, which are the sides crossing the side on which the drive circuit is mounted, is smaller than the width of the side on which the drive circuit and other components are mounted and the opposite side, namely, the short sides of the light shielding film PM. Note that, similarly to the first embodiment, the width of the light shielding film PM may be the same in all sides.
Further, as is apparent from
At this time, in the side portion in which the drive circuit and other components are mounted, it is necessary to provide the area for mounting the drive circuit as well as the area for forming the connection terminal portion of the flexible wiring substrate. In general, the width of the frame area, namely, the width of the light shielding film PM in the side portion in which the drive circuit and other components are mounted, is made larger than the width in the other side portions. Thus, in the display device according to the second embodiment, it is configured such that the second light shielding film PM2 is not formed on the side portion in which the drive circuit is mounted. In other words, by increasing the accumulation of adhesive, it is possible to obtain a remarkable effect of preventing the applied adhesive from being squeezed out into the area where the drive circuit and the connection terminal portion are formed. As a result, it is possible to significantly improve the reliability of the display device. Note that when the protective plate FW is bonded to the front surface of the display panel PNL, the protective plate FW and the display panel PNL are bonded with the adhesive AD which is not applied to the drive circuit and the connection terminal portion. In other words, the protective plate FW is bonded with the adhesive applied to the front surface of the second substrate.
Further, the configuration in which the flexible wiring substrate is connected to one side of the protective plate FW is the same in the display panel in which a touch panel (coordinate input device) is provided on the front surface of the display panel. In other words, a signal line for inputting and outputting signals for touch position detection to/from the touch panel (in general, the flexible wiring substrate is used) is also connected to the connection terminal portion formed at the side edge on the same side on which the drive circuit and other components of the display panel are mounted. Thus, when the protective plate FW is bonded by applying the adhesive to the front surface of the display panel, namely, the front surface of the touch panel, the adhesive is generally applied so as to avoid the connection terminal portion of the touch panel. Thus, by applying the present invention, it is possible to obtain the above effect, in addition to same effect as the first embodiment also in the configuration in which the touch panel is provided on the back surface side of the protective plate FW.
Note that in the configuration of the light shielding film PM according to the second embodiment, also in one or both of the corner portions of the short side on the upper side of the figure, similarly to the first embodiment, it is possible to form the cut-out area RM which is the area where the second light shielding film PM2 is not printed. In this case, it is possible to obtain the effect described in the first embodiment, in addition to the effect of the second embodiment. Thus, the formation of bubbles can be prevented more effectively.
Note that in the display device according to the first and second embodiments of the present invention, the light shielding film PM is formed such that the frame-like first light shielding film PM1 is printed in a circular form, and then the second light shielding film PM2 is printed so that the width of the second light shielding film PM2 is smaller than the first light shielding film PM1. However, the present invention is not limited to this configuration. For example, the light shielding film PM may be formed such that the second light shielding film PM2 is first printed on the back surface of the protective plate FW, and then the first light shielding film PM1 is printed.
Further, in the display device according to the first and second embodiments of the present invention, the light shielding film PM is formed by two layers of light shielding films (the first light shielding film PM1 and the second light shielding film PM2). However, the present invention is not limited to this configuration. The light shielding film PM may be formed by three or more layers of light shielding films. In this case, of the light shielding films except the light shielding film formed on the layer closest to the protective plate FW, at least one layer of light shielding film is not formed in the corner portion of the protective plate FW. In this way, the above effect can be obtained.
Further, in the display device according to the first and second embodiments, it is desirable to form the cut-out area RM, which is the area where the second light shielding film PM2 is not formed, in at least two corner portions sharing the side on which the end of the screen printing of the first and second light shielding films PM1 and PM2 is the inner peripheral edge of the light shielding film PM. In this case, in the formation of the projection associated with the screen printing, the difference in level caused by the formation of the light shielding film PM is greater than the film thickness, so that bubbles are more likely to occur.
It is to be understood that, while the present invention has been described in conjunction with the preferred specific embodiments thereof, the present invention is not limited to the specific embodiments and various changes and modifications can be made without departing from the scope of the present invention.
Number | Date | Country | Kind |
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2013-054519 | Mar 2013 | JP | national |
Number | Name | Date | Kind |
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20100245707 | Harada | Sep 2010 | A1 |
20120200796 | Harayama et al. | Aug 2012 | A1 |
20120235048 | Kim | Sep 2012 | A1 |
Number | Date | Country |
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2011-7830 | Jan 2011 | JP |
Number | Date | Country | |
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20140267989 A1 | Sep 2014 | US |