Display apparatus

Performance of a display apparatus is improved. The display apparatus includes: a substrate having a side surface (first side surface); a backlight unit (light supply portion) having a side surface (second side surface); a flexible wiring board having a wiring electrically connected to a terminal (first terminal) and having an insulating film with flexibility covering the wiring; and a double-sided tape. The flexible wiring board is bonded to the side surface of the backlight unit through the double-sided tape.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent Application No. 2019-142267 filed on Aug. 1, 2019, the content of which is hereby incorporated by reference into this application.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a technique of a display apparatus.

BACKGROUND OF THE INVENTION

Each of a Patent Document 1 (Japanese Patent Application Laid-Open Publication No. 2009-272457), a Patent Document 2 (Japanese Patent Application Laid-Open Publication No. 2005-122078) and a Patent Document 3 (Japanese Patent Application Laid-Open Publication No. 2019-124829) describes a display apparatus that is obtained by bonding a substrate of the display apparatus and a wiring board connected to this substrate by using a paste-form resin, and then, curing this resin.

SUMMARY OF THE INVENTION

As a part of performance improvement of each display apparatus, the inventors of the present application have studied a technique of reducing a frame region of each display apparatus. To a substrate included in the display apparatus, a flexible wiring board is connected. The flexible wiring board is curved so as to be bent from a front surface side of the substrate to a back surface side of the substrate, and is housed in an enclosure. In view of reduction of an area of a peripheral region around an effective display region of the display apparatus, it is preferable to reduce a gap between the curved part of the flexible wiring board and the substrate or a light supply portion on the back surface side of the substrate.

A purpose for the present invention is to provide a technique of improving the performance of the display apparatus.

A display apparatus according to one embodiment of the present invention includes: a first substrate having a first front surface having a first terminal formed thereon, a first back surface positioned on an opposite side of the first front surface and a first side surface crossing the first front surface and the first back surface; a light supply portion having a second front surface facing the first back surface, a second back surface positioned on an opposite side of the second front surface and a second side surface crossing the second front surface and the second back surface; a flexible wiring board having a wiring electrically connected to the first terminal and having an insulating film with flexibility covering the wiring; and a double-sided tape having a base film and a pasting layer formed on each of both surfaces of the base film. The flexible wiring board is bonded to the second side surface of the light supply portion through the double-sided tape.

DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

The following is explanation for each embodiment of the present invention with reference to drawings. Note that disclosure shows only one example, and appropriate modification with keeping the concept of the present invention which can be easily anticipated by those who are skilled in the art is obviously within in the scope of the present invention. Also, in order to make the clear description, a width, a thickness, a shape, and others of each portion in the drawings are schematically illustrated more than those in an actual aspect in some cases. However, the illustration is only one example, and does not limit the interpretation of the present invention. In the present specification and each drawing, similar elements to those described earlier for the already-described drawings are denoted with the same or relative reference characters, and detailed description for them is appropriately omitted in some cases.

A liquid crystal display apparatus is roughly classified into the following two types depending on a direction of application of an electric field for use in changing alignment of liquid crystal molecules of a liquid crystal layer. In other words, as the first classification, so-called vertical electric field mode in which the electric field is applied in a thickness direction (or an out-of-plane direction) of the display apparatus is cited. As the vertical electric field mode, for example, a TN (Twisted Nematic) mode, a VA (Vertical Alignment) mode and others are cited. As the second classification, so-called horizontal electric field mode in which the electric field is applied in a planar direction (or an in-plane direction) of the display apparatus is cited. As the horizontal electric field mode, for example, an IPS (In-Plane Switching) mode, a FFS (Fringe Field Switching) mode that is one of the IPS modes and others are cited. A technique described below is applicable to both the vertical electric field mode and the horizontal electric field mode.

First Embodiment

First, a configuration example of the display apparatus will be explained.FIG. 1is a planar view on a display surface side showing one example of the display apparatus according to the present embodiment. InFIG. 1, a boundary between a display region DA and a peripheral region PFA is shown with a dashed double-dotted line. InFIG. 1, a region where a sealing member SLM is arranged is shown with a dot pattern.FIG. 2is a cross-sectional view taken along a line A-A ofFIG. 1. As shown inFIG. 4described later, in addition to the liquid crystal layer LQ, a plurality of conductive layers and insulating layers exist between a substrate10and a substrate20. However, these elements are omitted inFIG. 2.FIG. 3is a circuit diagram showing a circuit configuration example around a pixel included in the display apparatus shown inFIG. 1.FIG. 4is an enlarged cross-sectional view of the display region of the display apparatus shown inFIG. 2. InFIG. 4, in order to exemplify a positional relation between a scan signal line GL and an image signal line SL in a thickness direction of the substrate10(a Z direction shown inFIG. 4), a scan signal line GL formed on a different cross section from that ofFIG. 4is shown with a dotted line.FIG. 5is an enlarged cross-sectional view showing a configuration example of a transistor shown inFIG. 3.

As shown inFIG. 1, a display apparatus DSP1of the present embodiment includes the display region DA. In the display region DA, images are formed in accordance with an input signal supplied from outside. The display region DA is an effective region where the display apparatus DSP1displays the images in a plan view in which the display surface is viewed. The display apparatus DSP1includes a peripheral region (non-display region) PFA around the display region DA in a plan view. While the display apparatus DSP1includes the peripheral region PFA around the display region DA, a display apparatus including the display region DA even on an edge portion is also cited as a modification example. The technique described below is also applicable to the display apparatus of the type including the display region DA even on the edge portion. Although the display region DA of the display apparatus DSP1shown inFIG. 1has a rectangular shape, the display region may have a shape such as a polygonal shape, a circular shape and others other than the rectangular shape.

As shown inFIG. 2, the display apparatus DSP1includes the substrate10and the substrate20that are pasted so as to face each other through the liquid crystal layer LQ. The substrate10and the substrate20face each other in the thickness direction (Z direction) of the display apparatus DSP1. The substrate10has a front surface (main surface, surface)10ffacing the liquid crystal layer LQ (and the substrate20) and a back surface (main surface, surface)10bpositioned on an opposite side of the front surface10f. The substrate10has a side surface10scrossing the front surface10fand the back surface10b. The substrate20has a back surface (main surface, surface)20bfacing the front surface10fof the substrate10(and the liquid crystal layer LQ). The substrate10is an array substrate in which a plurality of transistors (transistor elements) Tr1(seeFIG. 3) serving as switching elements (active elements) are arranged in an array form. The substrate20is a substrate formed on the display surface side. The substrate20can be also reworded as an opposite substrate meaning a substrate that is opposite to the array substrate.

The liquid crystal layer LQ is between the front surface10fof the substrate10and the back surface20bof the substrate20. The liquid crystal layer LQ is an electrooptic layer for use in controlling a visible light penetrating state. The liquid crystal layer LQ has a function of modulating the light penetrating itself by controlling a state of an electric field formed around the liquid crystal layer LQ through the switching element (the transistor Tr1shown inFIG. 3). The display regions DA of the substrate10and the substrate20overlap the liquid crystal layer LQ as shown inFIG. 2.

The substrate10and the substrate20are bonded to each other through the sealing member (bonding member) SLM. As shown inFIG. 1, the sealing member SLM is arranged in the peripheral region PFA so as to surround the periphery of the display region DA. As shown inFIG. 2, the liquid crystal layer LQ is inside the sealing member SLM. The sealing member SLM plays a role as a sealing material that seals the liquid crystal between the substrate10and the substrate20. Also, the sealing member SLM plays a role as a bonding material that bonds the substrate10and the substrate20.

The display apparatus DSP1includes an optical element OD1and an optical element OD2. The optical element OD1is arranged between the substrate10and the backlight unit40. The optical element OD2is arranged on the display surface side of the substrate20, in other words, an opposite side of the substrate10across the substrate20. Each of the optical element OD1and the optical element OD2includes at least a polarizer, and may include a phase shift plate (waveplate) if needed. The backlight unit40has a front surface40ffacing the back surface10bof the substrate10and a back surface40bpositioned on an opposite side of the front surface40f. Also, the backlight unit40includes a side surface40scrossing the front surface40fand the back surface40b.

The display apparatus DSP1includes a cover member CVM (seeFIG. 2) covering the display surface side of the substrate20. The cover member CVM faces the front surface20fthat is on the opposite side of the back surface20bof the substrate20. In other words, the cover member CVM faces the front surface10fthat is on the opposite side of the back surface10bof the substrate10. The substrate20is between the cover member CVM and the substrate10in the Z direction. The cover member CVM is a protection member that protects the substrates10and20and the optical element OD2, and is arranged on the display surface side of the display apparatus DSP1. However, a case without the cover member CVM may be also applicable as a modification example of the present embodiment.

Each of the substrate10and the substrate20is a transparent plate having visible-light transmissivity (that is a property allowing the visible light to be transmitted). Asa substrate that is the transparent plate, a glass substrate can be exemplified. As a constituent material of the substrate10and the substrate20, a resin material containing polymer such as polyimide, polyamide, polycarbonate, polyester or others (a resin material having the visible-light transmissivity) can be also used.

In a case of the present embodiment, the flexible wiring board50is connected to the peripheral region PFA of the substrate10. A terminal TM1is formed on the front surface10fof the substrate10. The terminal TM1is formed between the side surface10sand the display region DA. The flexible wiring board50includes a wiring51connected to the terminal TM1and an insulating film52that covers the wiring51and that is formed so as to be bendable and deformable.

In the case of the present embodiment, a semiconductor chip CP1is mounted in the peripheral region PFA of the substrate10. A terminal TM2is formed on the front surface10fof the substrate10. The terminal TM2is formed between the terminal TM1and the display region DA. The semiconductor chip CP1is mounted on the terminal TM2. The terminal TM2and the semiconductor chip CP1are electrically connected to each other.

One end of the flexible wiring board50is connected onto the front surface10fof the substrate10, and the other end is arranged on the back surface40bside of the backlight unit40. The flexible wiring board50is bent so as to cover the side surface10sof the substrate10and the side surface40sof the backlight unit40. The flexible wiring board50is bonded to the backlight unit40through a double-sided tape60. Details of a structure that bonds the flexible wiring board50and the backlight unit40will be described later.

The light that is supplied from the backlight unit40reaches the cover member CVM through the optical element OD1including the polarizer, the substrate10, the liquid crystal layer LQ, the substrate20and the optical element OD2. An optical filter layer although not illustrated is arranged between the substrate20and the liquid crystal layer LQ. The optical filter layer includes a light blocking film that blocks the visible light and a plurality of types of color filter films.

As shown inFIG. 3, a plurality of pixels PX are arranged in the display region DA. In an example shown inFIG. 3, each of the plurality of pixels PX includes a plurality of subpixels PXs. The plurality of subpixels PXs include subpixels PXs for use in, for example, a red color, a blue color and a green color, and a color image can be displayed by control of color gradation of the plurality of subpixels PXs. As the number of types of the subpixels PXs configuring one pixel PX, not only the three types exemplified inFIG. 3but also various modification examples are applicable.

Each of the plurality of subpixels Pxs is provided with the transistor Tr1that is a switching element that controls turning ON/OFF of the electric field applied to the liquid crystal layer LQ. The transistor Tr1controls an operation of the subpixel PXs. The transistor Tr1is a thin film transistor (TFT) formed on the substrate10as described later.

As shown inFIG. 3, in the display region DA, the display apparatus DSP1includes a plurality of scan signal lines GL extending in an X direction and a plurality of image signal lines SL extending in a Y direction crossing (inFIG. 3, being orthogonal to) the X direction. The scan signal line GL is a gate line connected to a gate of the transistor Tr1. The image signal line SL is a source line connected to a source of the transistor Tr1. The plurality of scan signal lines GL extend in the X direction and are arrayed in the Y direction at, for example, an equal distance therebetween. The plurality of image signal lines SL extend in the Y direction and are arrayed in the X direction at, for example, an equal distance therebetween.

Each of the plurality of scan signal lines GL is connected to a scan driving circuit (gate driving circuit) GD. A scan signal Gsi that is output from the scan driving circuit GD is input to the gate of the transistor Tr1through the scan signal line GL. Each of the plurality of image signal lines SL is connected to an image signal driving circuit SD. An image signal Spi that is output from the image signal driving circuit SD is input to the source of the transistor Tr1through the image signal line SL.

Each of the plurality of image signal line SL is connected to a pixel electrode PE trough the transistor Tr1. More specifically, the image signal line SL is connected to the source of the transistor Tr1, and the pixel electrode PE is connected to a drain of the transistor Tr1. When the transistor Tr1is turned ON, an image signal Spic is supplied from the image signal line SL to the pixel electrode PE. The pixel electrode PE is connected to a common electrode CE through a dielectric layer (a capacitive element CS shown inFIG. 3). To the common electrode CE, a fixed potential is supplied from a common potential supply circuit CD. The fixed potential that is supplied to the common electrode CE is a common potential among the plurality of subpixels PXs. In a display period, the electric field is formed in each subpixel PXs in accordance with a potential difference between a potential supplied to the common electrode CE and a potential supplied to the pixel electrode PE, and the liquid crystal molecules contained in the liquid crystal layer LQ are driven by this electric field.

Each of the scan driving circuit GD, the image signal driving circuit SD and the common potential supply circuit CD shown inFIG. 3is formed in, for example, a semiconductor chip CP1mounted in the peripheral region PFA of the substrate10shown inFIG. 2. However, as a modification example, a case of mounting the semiconductor chip CP1in the flexible wiring board50connected to the peripheral region PFA shown inFIG. 2is cited. As another modification example, a case of formation of a part or all of the scan driving circuit GD, the image signal driving circuit SD and the common potential supply circuit CD serving as built-in circuits in the substrate10is cited.

<Bonding of Flexible Wiring Board>

FIG. 4is an enlarged cross-sectional view around a bonding portion between the backlight unit and the flexible wiring board50shown inFIG. 2.

As shown inFIG. 2, the display apparatus DSP1of the present embodiment is provided with the backlight unit40serving as a light supply portion that supplies light to the liquid crystal layer LQ. The backlight unit40includes, for example, a light source element41, a light guiding panel42that supplies the light supplied from the light source element41toward the liquid crystal layer LQ, and an optical element43serving as a functional film having an optical function. As one example, the optical element43is made of a first optical sheet43a(diffusion sheet) and a second optical sheet42b(prism sheet), and the first optical sheet43ais arranged between the light guiding panel42and the second optical sheet43b. A reflective sheet45is arranged on a lower surface of the light guiding panel42, and the light guiding panel42and the light source element41are fixed to each other by a fixing tape46. The portion around the backlight unit40is covered with a light blocking member44for use in suppressing light leakage toward the side surface40sof the backlight unit40. The light blocking member44may be a light blocking tape pasted on a case of the backlight unit40or be the light-blocking case itself. The case may be reworded as other expressions such as an enclosure, a housing, a frame, and a bezel.

The double-sided tape60is provided with a base film61having flexibility and a plurality of sticking layers62arranged on both sides of the base film61. One sticking layer62is boned to the backlight unit40. The other sticking layer62is bonded to the flexible wiring board50. The double-sided tape60is bonded to at least the side surface40sof the backlight unit40.

In order to reduce an area of the peripheral region PFA shown inFIG. 1, it is necessary to reduce a distance from an outer edge of the display apparatus DSP1to the substrate10(seeFIG. 2) and reduce a distance from the outer edge of the display apparatus DSP1to the backlight unit40. Therefore, for example, during an assembly step of housing the display apparatus DSP1in the enclosure not illustrated, it is preferable to bond the flexible wiring board50to at least the side surface40sof the backlight unit40in view of avoidance of the contact between the flexible wiring board50and the enclosure.

In the present embodiment, the flexible wiring board50is bonded to the backlight unit40through the double-sided tape60. As a study example for the present embodiment, a method of using a paste-from resin bonding member as the bonding material for use in bonding the backlight unit40and the flexible wiring board50is cited. However, when the paste-form bonding member is used, it is difficult to control a thickness of the applied resin. Therefore, a gap distance between the backlight unit40and the flexible wiring board50easily varies.

On the other hand, as described in the present embodiment, when the backlight unit40and the flexible wiring board50are bonded to each other by the double-side tape60, it is easy to control a thickness of the double-sided tape60. In other words, a margin for the gap distance between the backlight unit40and the flexible wiring board50that are bonded can be reduced. As a result, the gap between the enclosure and the substrate10can be reduced, and therefore, the area of the peripheral region PFA shown inFIG. 1can be reduced.

As shown inFIG. 4, in a thickness direction of the backlight unit40(a Z direction shown inFIG. 4), the side surface10sof the substrate10and the side surface40sof the backlight unit40do not overlap each other. A part of the front surface40fof the backlight unit40(more specifically, a part including the side surface40s) does not overlap the substrate10. In other words, a part of the backlight unit40protrudes outward from an end of the substrate10. A gap G1between the side surface10sand the side surface40sis, for example, about 200 μm.

When a modification example ofFIG. 4has a structure in which the side surface10sand the side surface40soverlap each in the Z direction, the flexible wiring board50is sharply bent on the side surface105of the substrate10. In this case, a bending stress is applied to a wiring51of the flexible wiring board50. Particularly, since the side surface10sof the substrate10is close to the terminal TM1connected to the wiring51, the wiring51of the flexible wiring board50is exposed at a position overlapping the side surface10sfrom an insulating film52protecting the wiring51. Therefore, the position at which the wiring51is exposed from the insulating film52has a possibility of damage on the wiring51depending on a degree of the bending stress applied to the wiring51. On the other hand, when the part of the front surface40fof the backlight unit40, the part including the side surface40s, has the structure not overlapping the substrate10as shown inFIG. 4, a bend radius of the curved portion at which the flexible wiring board50is bent can be increased. As a result, since the stress applied to the wiring51of the flexible wiring board50can be reduced in a portion near the connecting portion with the terminal TM1, the damage on the wiring51can be suppressed.

In view of improvement of bonding strength between the flexible wiring board50and the backlight unit40, it is preferable to increase a bonding area between the double-sided tape60and the backlight unit40. A thickness T1of the backlight unit40shown inFIG. 4(a distance between one of the front surface40fand the back surface40bto the other) is, for example, about 1 mm. Therefore, when the double-sided tape60is bonded to only the side surface405of the backlight unit40, it is difficult to increase the bonding area between the double-sided tape60and the backlight unit40. In the case of the bonding method using the double-sided tape60, the bonding strength tends to be smaller than that of a bonding method of curing the paste-form bonding member. Therefore, it is particularly preferable to increase the bonding area between the double-sided tape60and the backlight unit40. In the present embodiment, as shown inFIG. 4, the flexible wiring board50is bonded to the side surface40sand the back surface40bof the backlight unit40through the double-sided tape60.

In the example shown inFIG. 4, a bonding area between the double-sided tape60and the back surface40bis larger than a bonding area between the double-sided tape60and the side surface40s. When the double-sided tape60is bonded also to the back surface40bof the backlight unit40as described above, the bonding area can be increased. As a result, each of the bonding strength between the backlight unit40and the double-sided tape60and the bonding strength between the double-sided tape60and the flexible wiring board50can be enhanced, so that the double-sided tape60can be prevented from peeling off.

<Bonding Method of Flexible Wiring Board>

Next, as shown inFIG. 4, the method of bonding the flexible wiring board50to the backlight unit40will be explained. Each ofFIGS. 5 to 9is a planar view showing the assembly step of bonding the flexible wiring board to the backlight unit.

In the assembly steps of the display apparatus DSP1shown inFIG. 4, the double-sided tape60is pasted first on the back surface of the flexible wiring board50as shown inFIG. 5. At this time, while one sticking layer62(seeFIG. 4) of the double-sided tape60is pasted on the flexible wiring board50, a separator sheet shown inFIG. 5is pasted on the other sticking layer62(seeFIG. 4). On the back surface10bof the substrate10, the optical element OD1including the light polarizer is pasted.

Next, onto the optical element OD1pasted on the back surface10bof the substrate10, the backlight unit40is pasted as shown inFIG. 6. As shown inFIG. 6, in a plan view obtained by viewing the apparatus from the back surface10bof the substrate10(seeFIG. 5), the side surface10sof the substrate10is covered with the backlight unit40.

Next, as shown inFIG. 7, the separator sheet63(seeFIG. 6) that is pasted on one sticking layer62of the double-sided tape60is peeled off so that the sticking layer62is exposed. Next, as shown inFIG. 8, an eternal force64is applied while the flexible wiring board50pasted with the double-sided tape60is stretched upward (in a direction from the front surface10fto the back surface10bof the substrate10shown inFIG. 2), and the double-sided tape60is bonded to the side surface40sof the backlight unit40. Although methods of applying the external force64include various modification examples, it is preferable to, for example, use a jig capable of pressing entire part of the double-sided tape60, the part facing the side surface40sof the backlight unit40.

Next, as shown inFIG. 9, the flexible wiring board50is boned to the back surface40bof the backlight unit40through the double-sided tape60. As shown inFIG. 4, this manner can provide the display apparatus DSP1including the flexible wiring board50being bonded to the side surface40sand the back surface40bof the backlight unit40through the double-sided tape60.

Next, modification examples will be explained.FIG. 10is a planar view showing a modification example ofFIG. 7. A display apparatus DSP2shown inFIG. 10is different from the display apparatus DSP1shown inFIG. 7in that the double-sided tape60is provided with an opening65.

The double-sided tape60included in the display apparatus DSP2includes a region66facing the side surface405of the backlight unit40and a region67facing the back surface40bof the backlight unit40in a state of the bonded double-sided tape60. The region67is provided with the opening65. In an example shown inFIG. 10, the region67of the double-sided tape60is formed so as to have a frame shape, and a through hole is formed at center of the frame. In this case, the bonding area of the double-sided tape60is smaller than that of the example shown inFIG. 7. In the case of the display apparatus DSP2, when recovery work (repair) is necessary after the double-sided tape60is pasted, an effect of easiness of the peeling off is exerted by local force application. When the double-sided tape60is formed so as to have the frame shape, even if the bonding area of the double-sided tape60is small, an area surrounded by the region bonded with the double-sided tape60is large. In this case, even if the bonding area is small, the bonding strength of the entire double-sided tape60can be improved. In other words, in the present modification example, it is easy to peel off the double-sided tape60if needed while it is difficult to peel off the double-sided tape60if the double-sided tape is not intendedly peeled off. When the resin bonding material is used in place of the double-sided tape60, it is difficult to peel off the flexible wiring board50from the cured resin bonding material, and therefore, the usage of the double-sided tape60is more advantageous than the usage of the resin bonding material even in view of easiness of the repair.

As a modification example ofFIG. 10, the double-sided tape60is pasted on only the region66while the double-sided tape60is not pasted on the region67in some cases although illustration is omitted. As another modification example, the semiconductor chip CP1shown inFIG. 4is mounted on the flexible wiring board50in some cases. When the semiconductor chip CP1is mounted on the flexible wiring board50, a support strength of the mounted semiconductor chip CP1is improved by increasing the thickness of the flexible wiring board50. The larger the thickness of the flexible wiring board50is, the larger the elasticity of the insulating film52is. Therefore, it is easy to peel off the flexible wiring board50from the backlight unit40. Therefore, it is preferable to increase each of the bonding area between the double-sided tape60and the flexible wiring board50and the bonding area between the double-sided tape60and the backlight unit40.

In the scope of the concept of the present invention, various modification examples and alteration examples could have been easily anticipated by those who are skilled in the art, and it would be understood that these various modification examples and alteration examples belong to the scope of the present invention. For example, the ones obtained by appropriate addition, removal, or design-change of the components to/from/into each of the above-described embodiments by those who are skilled in the art or obtained by addition, omitting, or condition-change of the step to/from/into each of the above-described embodiments are also within the scope of the present invention as long as the ones include the concept of the present invention.

The present invention can be utilized for a display apparatus.