Electronic device and display unit

An electronic device includes: a first circuit board on which a first circuit is mounted; a second circuit board on which a second circuit is mounted; a supporter; a flexible flat cable disposed on the supporter and connecting the first circuit board and the second circuit board to each other, the flexible flat cable transmitting signals between the first circuit and the second circuit. The flexible flat cable is provided with a crease. The flexible flat cable is disposed such that the crease is in contact with the supporter.

TECHNICAL FIELD

The present disclosure relates to an electronic device in which a plurality of circuit boards are electrically connected to each other by a flexible flat cable.

BACKGROUND ART

Patent Literature 1 discloses a technique relating to a flexible flat cable (hereinafter abbreviated as an “FFC”).

In an electronic device in which two circuit boards are electrically connected to each other by an FFC, a differential data transmission scheme may be used in a case where signals of a great information volume, such as video signals, are transmitted.

One representative scheme belonging to the differential data transmission scheme is the LVDS (Low Voltage Differential Signaling). The LVDS is a technique that realizes high-speed digital interface, and used, for example, in a case where video signals are transmitted between circuit boards in a display apparatus. The transmission rate of the LVDS is several hundred Mbps per channel.

In recent years, display panels of higher resolution are available. For example, there is a display panel having about 4000×2000 pixels (hereinafter referred to as a “4k2k panel”). With a display apparatus having such a high-resolution display panel, the information volume of an image is greater than with a conventional display apparatus, and therefore the transmission volume of video signals becomes greater than with the conventional display apparatus. Accordingly, with such a display apparatus, even when the LVDS is used for transmitting video signals, it is difficult to suppress an increase in the number of signals (i.e., the number of channels) required to be transmitted. Then, when the number of signal lines (i.e., the number of channels) included in one FFC is increased in order to address the increase in the number of signals, various restrictions and difficulties may arise in designing circuit boards.

When the signal transmission volume per channel can be increased, the number of signal lines (i.e., the number of channels) included in one FFC can be reduced. Here, transmission schemes that realize the transmission volume per channel at gigabit rates (Gpbs) are proposed as techniques replacing the LVDS. The transmission schemes include, for example, the V-BY-One (registered trademark) HS providing the maximum transmission rate of 3.75 Gbps, and the eDP (embedded Display Port) providing the maximum transmission rate of 5.4 Gbps.

As a cable for transmitting high frequency signals based on such transmission schemes between circuit boards, generally, an FFC which is impedance-matched and capable of keeping the quality of the transmission signals is used. Such an FFC is generally structured as follows. A wiring conductor through which signals flow is covered by an insulator. On one surface (a shield surface) of the wiring conductor, a dielectric, a conductor metal foil for GND and an insulator are layered in order to prevent leakage or entry of electromagnetic noises. In the following, the one surface (the shield surface) of an FFC is referred to as the “shield surface of the FFC”, and the other surface thereof is referred to as the “signal surface of the FFC”.

With an electronic device having circuit boards connected to each other by the FFC, in some cases, when the signal surface of the FFC is brought into surface contact with a metal-made member (a metal material), a low-pass filter (LPF) may be formed by the capacitance occurring at the contact portion and the resistance component of the wire resistance and the like. This LPF may attenuate high frequency signals flowing through the FFC. This capacitance becomes greater in proportional to the contact area between the signal surface of the FFC and the metal material. As the capacitance is greater, the attenuation amount of the high frequency signals flowing through the FFC tends to increase.

For example, with a display apparatus including a liquid crystal panel as a display panel, circuit boards are generally disposed on a metal material (a supporter that supports the display unit of the liquid crystal panel) covering the back surface side of the liquid crystal panel. In order to prevent leakage or entry of electromagnetic noises, an FFC is disposed such that the shield surface is opposed to the rear cover of the display apparatus. Accordingly, when a “sag” or the like occurs at the FFC, the signal surface of the FFC may be brought into surface contact with the metal material.

Then, with an electronic device in which high frequency signals are transmitted and received between internal circuit boards at gigabit rates, when the metal material and the signal surface of an FFC are brought into surface contact with each other, the signals transmitted through the FFC attenuate, and the circuit board on the reception side may not be able to normally receive the signals.

CITATION LIST

Patent Literature

SUMMARY

The present disclosure provides an electronic device and a display apparatus capable of reducing the attenuation amount of high frequency signals transmitted and received between a plurality of circuit boards, when the frequency signals are transmitted through an FFC.

An electronic device of the present disclosure includes: a first circuit board on which a first circuit is mounted; a second circuit board on which a second circuit is mounted; a supporter; and a flexible flat cable. The flexible flat cable is disposed on the supporter and connects the first circuit board and the second circuit board to each other. The flexible flat cable transmits a signal between the first circuit and the second circuit. The flexible flat cable is provided with a crease. The flexible flat cable is disposed such that the crease is in contact with the supporter.

A display apparatus of the present disclosure includes: a display panel having a display unit displaying an image and a supporter supporting the display unit; a first circuit board on which a first circuit is mounted; a second circuit board on which a second circuit is mounted; and a flexible flat cable. The flexible flat cable is disposed on the supporter, and connects the first circuit board and the second circuit board to each other. The flexible flat cable transmits a signal between the first circuit and the second circuit. The flexible flat cable is provided with a crease. The flexible flat cable is disposed such that the crease is in contact with the supporter.

DESCRIPTION OF EMBODIMENTS

In the following, with reference to the drawings as appropriate, a description will be given of an exemplary embodiment in detail. However, an unnecessarily detailed description may be omitted. For example, a detailed description of an already well-known matter or a repeated description of a substantially identical structure may be omitted. This is to avoid the following description from becoming unnecessary redundant, and to facilitate understanding of a person skilled in the art.

Note that, the accompanying drawings and the following description are provided for a person skilled in the art to fully understand the present disclosure, and they are not intended to limit the subject matter stated in the scope of claims.

First Exemplary Embodiment

In the following, with reference toFIGS. 1 to 6, a description will be given of a first exemplary embodiment. Note that, in the present exemplary embodiment, though a display apparatus including a liquid crystal panel as a display panel is shown as an example of an electronic device including an FFC, the present disclosure is not limited to the display apparatus. The present disclosure is applicable to an electronic device in which a plurality of circuit boards are connected to each other by an FFC, and high frequency signals which are transmitted and received between the circuit boards are transmitted via the FFC.

FIG. 1is a rear view of display apparatus100according to the first exemplary embodiment.FIG. 1schematically shows a plan view of display apparatus100from which a rear cover is removed as seen from the back surface side. Note that, in the present exemplary embodiment, in display apparatus100, the side where a surface for displaying images is provided (the image display side) is the front, and the side opposite to the image display surface (on the rear cover side) is the back.

Display apparatus100includes a display panel, signal circuit board110, timing controller board (hereinafter referred to as “TCon board”)120, power supply circuit board102, a plurality of speakers103outputting sounds, a plurality of module units104, and FFCs200.

The display panel includes a display unit having two glass substrates between which a plurality of display elements for displaying images are formed, and chassis unit101supporting the display unit (the glass substrates). Chassis unit101is one example of a supporter. The glass substrates are disposed on the front side of display apparatus100, and chassis unit101is disposed on the back side of display apparatus100. Accordingly, inFIG. 1, chassis unit101of the display panel is shown and the display unit is not shown. Though chassis unit101is formed by metal such as aluminum for example, chassis unit101may be formed by other materials.

Signal circuit board110is a circuit board on which a signal processing circuit (not shown) that processes signals (input video signals and the like) received from an external video signal generating apparatus, a broadcast station or the like and outputs the processed signals is mounted. The signal processing circuit is one example of a first circuit, and signal circuit board110is one example of a first circuit board.

TCon board120is a circuit board on which a drive circuit (not shown) is mounted. The drive circuit receives video signals output from the signal processing circuit mounted on signal circuit board110, and generates signals for displaying an image based on the video signals on the display unit of the display panel. The drive circuit is one example of a second circuit, and TCon board120is one example of a second circuit board.

Power supply circuit board102is a circuit board on which a power supply circuit (not shown) that converts AC household power supply into DC power supply is mounted. In display apparatus100, the circuit boards, i.e., signal circuit board110, TCon board120, and power supply circuit board102are disposed on chassis unit101. With display apparatus100, though the circuit boards are fixed to chassis unit101, the present exemplary embodiment does not limit the arrangement position or fixing method of the circuit boards. The circuit boards may be fixed to any member other than the supporter (for example, a housing or the like), or may not be disposed immediately above chassis unit101.

Module units104are, for example, a light receiving unit that receives infrared signals from a remote controller, a Wi-Fi (registered trademark) connecting unit, a Bluetooth (registered trademark) connecting unit and the like. However, module units104are not limited thereto.

Between speakers103and signal circuit board110, and between module units104and signal circuit board110, are electrically connected by wire harnesses300.

FFCs200are disposed on chassis unit101to connect signal circuit board110and TCon board120to each other, thereby transmitting high frequency signals between the signal processing circuit and the drive circuit.

Signal circuit board110has terminal group112. Terminal group112is made up of, for example, an HDMI (registered trademark) terminal, a USB (Universal Serial Bus) terminal, a YUV terminal, a tuner and the like. However, the present disclosure is not limited thereto. Mounted on signal circuit board110is an LSI (Large Scale Integrated circuit, not shown) in which a signal processing circuit configured to perform signal processing such as demodulation of video signals and sound signals input from terminal group112or a noise removing process is integrated.

The signal processing circuit mounted on the signal circuit board110is configured to convert input video signals into video signals suitable for the display unit of the display panel, and to output the converted video signals (digital video signals). The signal processing circuit provides various signal processes to input video signals based on the drive scheme of the display unit of the display panel, the number of pixels and the like. Further, the signal processing circuit is also configured to control speakers103and module units104.

Note that, in place of the signal processing circuit, a processor may be mounted on signal circuit board110, to cause the processor to execute a program created to realize operations similar to those of the signal processing circuit.

Mounted on TCon board120is an IC (Integrated Circuit, not shown) in which a drive circuit configured to receive digital video signals output from the signal processing circuit on signal circuit board110and to convert the video signals into signals conforming to the specification of the display unit of the display panel is integrated. The drive circuit mounted on TCon board120is configured to receive video signals output from the signal processing circuit mounted on signal circuit board110, and to convert the video signals into a format suitable for the display unit of the display panel and output the converted signals at proper timing, in order for an image based on the video signals to be displayed on the display unit of the display panel. Then, in order for an image based on the video signals output from the signal processing circuit to be displayed on the display unit of the display panel, the drive circuit outputs signals for driving the display elements (liquid crystal cells) of the display unit based on the video signals.

Note that, in place of the drive circuit, a processor may be mounted on TCon board120, to cause the processor to execute a program created to realize operations similar to those of the drive circuit.

Signal circuit board110and TCon board120are electrically connected to each other by two FFCs200. On signal circuit board110, two receptacle connectors111for electrically connecting FFCs200to the signal processing circuit on the signal circuit board110are provided. Further, on TCon board120also, two receptacle connectors121for electrically connecting FFCs200to the drive circuit on TCon board120are provided. In the following, the receptacle connectors are simply referred to as the “connectors”.

To connectors111, one ends of FFCs200are connected. To connectors121, the other ends of FFCs200are connected. Thus, the signal processing circuit on signal circuit board110and the drive circuit on TCon board120are electrically connected to each other. Between the signal processing circuit on signal circuit board110and the drive circuit on TCon board120, high-frequency digital video signals are exchanged at high-speed (for example, at gigabit rates) via FFCs200.

Note that, the number of FFCs200connecting between the signal circuit board110and TCon board120is not limited to two. The number of FFCs200may be one or three or more.

Signal circuit board110has connector113that electrically connects wire harnesses300to the signal processing circuit. Wire harnesses300having their one ends connected to connector113and their other ends connected to module units104or speakers103transmit signals between the signal processing circuit on signal circuit board110and module units104or speakers103. Wire harnesses300are disposed such that FFCs200are interposed between wire harnesses300and chassis unit101of the display panel. Accordingly, as shown inFIG. 1, wire harnesses300cross FFCs200. Since wire harnesses300are relatively long and different from one another in length, they tend to be spread. Therefore, at display apparatus100, in order to prevent wire harnesses300from spreading, wire harnesses300are gathered and fixed to chassis unit101of the display panel by adhesive tapes400. In display apparatus100, FFCs200are pressed against chassis unit101by wire harnesses300fixed to chassis unit101by adhesive tapes400.

Signal circuit board110has connector114for connecting cables350. Power supply circuit board102has connector115for connecting cables350. By cables350having their one ends connected to connector114and their other ends connected to connector115, power supply and ground potential on signal circuit board110are electrically connected to power supply and ground potential of the power supply circuit on power supply circuit board102, respectively. Thus, from the power supply circuit on power supply circuit board102, properly set voltage is supplied to the signal processing circuit on signal circuit board110.

Note that, since operations of circuits included in display apparatus100are substantially the same as those of a generally used display apparatus of a liquid crystal television set or the like, detailed description thereof is omitted.

FIG. 2is a schematic diagram of FFC200according to the first exemplary embodiment.FIG. 2shows one example of FFC200before being connected to connector111of signal circuit board110and connector121of TCon board120.

FFC200has a front surface and a back surface. In the present exemplary embodiment, the front surface of FFC200is shield surface206, and the back surface is signal surface207. FFC200is formed to have certain flexibility and durability withstanding repeated folding. Therefore, FFC200can keep the state folded into any shape. For example, FFC200can keep creases provided to FFC200. The creases will be described later.

FIG. 2shows, as one example, FFC200being repeatedly folded by a length of about X mm (millimeters, for example, about 50 mm). Since FFC200can keep such a folded state, a volume required for storage or transportation, for example, can be reduced.

FIG. 3is a partial enlarged view of the cross section of an end of FFC200according to the first exemplary embodiment.FIG. 3shows a partial cross-sectional view of the area indicated by a broken line inFIG. 2.

FFC200according to the present exemplary embodiment is formed by a plurality of stacked substance layers, and has a thickness of about 0.5 mm to 1 mm. For example as shown inFIG. 2, FFC200is structured by six layers of insulating coat202a, conductor201, insulating coat202b, dielectric203, conductor204, and insulator205being stacked in order from the back surface (signal surface207). Accordingly, one surface of insulating coat202ais exposed outside as the back surface (signal surface207), and one surface of insulator205is exposed outside as the front surface (shield surface206). Insulating coat202a, insulating coat202b, and insulator205are formed by materials exhibiting relatively high insulation, such as synthetic resin.

Conductor201is a transmission path of signals, and is formed by a material exhibiting relatively high conductivity such as copper, so as to be capable of transmitting high frequency signals. Signals transmitted between signal circuit board110and TCon board120(for example, high-frequency digital video signals and the like) pass through this conductor201. Note that, conductor201is divided into a plurality of lines, and FFC200is capable of passing signals corresponding to the number of the lines. In display apparatus100according to the present exemplary embodiment, two FFCs200respectively having 51 and 41 pieces of conductors201are employed. However, the number of lines of conductor201is not limited to such values.

The other surface of insulating coat202ais in intimate contact with one surface of conductor201, and the other surface of conductor201is in intimate contact with one surface of insulating coat202b. Thus, the opposite surfaces of conductor201are respectively covered by insulating coat202aand insulating coat202bexhibiting relatively high insulating performance.

One surface of dielectric203is in intimate contact with the other surface of insulating coat202b. One surface of conductor204is in intimate contact with the other surface of dielectric203. Conductor204is formed by a material exhibiting relatively high conductivity such as copper, and connected to ground potential (the ground line, hereinafter also referred to as “GND”). Then, the other surface of conductor204is in intimate contact with the other surface of insulator205.

Note that, ends208of FFC200are not covered by insulating coat202aand insulator205so as to be capable of being electrically connected to connectors111and121, and the regions where conductor201, insulating coat202b, dielectric203, and conductor204are stacked are exposed. By one end208being connected to connector111and the other end208being connected to connector121, conductor201and connector111as well as connector121are electrically connected, and conductor204and connector111as well as connector121are electrically connected. Thus, the ground potential of signal circuit board110and the ground potential of TCon board120become substantially identical, and signals can be transmitted and received between the signal processing circuit on signal circuit board110and the drive circuit on TCon board120.

In FFC200, the materials and thickness of dielectric203and (or) conductor204are adjusted, to match the impedance of conductor201and conductor204to100Ω(ohm). Note that, FFC200is not limited to the six-layer structure, and the thickness and the impedance are not limited to the above-noted values.

In the present exemplary embodiment, since FFC200has the above-described structure, shield surface206and signal surface207differ in the performance of shielding the electromagnetic noises (the performance of preventing leakage and entry of electromagnetic noises) from each other. The distance from shield surface206to conductor201being the transmission path of signals is greater than the distance from signal surface207to conductor201. Further, between conductor201and shield surface206, a plurality of physical layers including conductor204connected to the ground potential are interposed. This conductor204functions as a shield layer that shields electromagnetic waves. On the other hand, between conductor201and signal surface207, only insulating coat202ais present. Therefore, shield surface206is greater in the electromagnetic noise shielding performance than signal surface207.

With display apparatus100according to the present exemplary embodiment, FFC200is disposed such that shield surface206is positioned on the back surface side of the display apparatus100and such that signal surface207is positioned on the chassis unit101side of the display panel. This is to prevent the electromagnetic noises generated by high frequency signals passing through FFC200from leaking outside display apparatus100.

FIG. 4Ais a plan view of ends208of FFC200according to the first exemplary embodiment as seen from the signal surface207side. InFIG. 4A, part of FFC200is omitted. Further, inFIG. 4A, conductor201routed under insulating coat202ais represented by broken lines.

As described above, with display apparatus100, two FFCs200differing in the number of lines of conductor201(for example, 51 pieces and 41 pieces) from each other are used. FFC200is shaped such that its one end208can be connected to connector111and the other end208can be connected to connector121. Then, as described above, at ends208of FFC200, conductor201is not covered by insulating coat202a, and conductor204is not covered by insulator205. Accordingly, as shown inFIG. 4A, conductor201and insulating coat202bare alternately exposed on signal surface207at ends208. The regions where insulating coat202bis exposed are portions where conductor201is not provided.

FFC200according to the present exemplary embodiment is provided with a plurality of creases210. Creases210are formed to be valley-folded on the shield surface206side and mountain-folded on the signal surface207side. Accordingly, in FFC200provided in display apparatus100, a region projecting in an arc-shaped manner toward the shield surface206side (the rear cover side of display apparatus100) between crease210and crease210is produced. In the present exemplary embodiment, nine creases210are provided to FFC200at an interval (represented by “Wa” inFIG. 4A) of about 50 mm to 70 mm.

FIG. 4Bis a cross-sectional view showing crease210of FFC200according to the first exemplary embodiment in a partially enlarged manner. Note that,FIG. 4Bshows chassis unit101of the display panel, and does not show the display unit.

As shown inFIG. 4B, crease210is provided with a fold-back which is set to have a width of about 5 mm to 40 mm (represented by “Wd” inFIG. 4B). In the present exemplary embodiment, FFC200is disposed at display apparatus100such that the folded back portion (the portion of signal surface207being mountain-folded) of crease210is in contact with chassis unit101of the display panel.

Note that, the number of creases210provided to FFC200, an interval of creases210, and a width of the fold-back described above are merely an example, and the present disclosure is not limited to the above-described values. The number of creases210provided to FFC200, an interval of creases210, a width of the fold-back and the like are desirably appropriately set according to the specification or size of an electronic device (or a display apparatus) in which FFC200is used, and the material or size of FFC200and the like.

Note that, the area of signal surface207of FFC200being in contact with chassis unit101of the display panel formed by metal is desirably the smallest as possible. Accordingly, the number of creases210provided to FFC200is preferably smaller, and the width of the fold-back is preferably also smaller.

FIG. 5Ais a cross-sectional view taken along line A-A inFIG. 1.FIG. 5Bis a plan view of a portion around FFC200of display apparatus100according to the first exemplary embodiment in a partially enlarged manner.FIGS. 5A and 5Bare a cross-sectional view and a plan view showing the state where FFC200is connected to signal circuit board110and TCon board120.FIG. 5Ashows chassis unit101of the display panel, and does not show the display unit.

Note that, inFIGS. 5A and 5B, the spaced-apart distance between signal circuit board110and TCon board120is represented by “Wb”.

As shown inFIGS. 5A and 5B, FFC200electrically connecting between signal circuit board110and TCon board120is disposed on chassis unit101of the display panel. The length of FFC200is set to be longer than spaced-apart distance Wb between signal circuit board110and TCon board120. Accordingly, to FFC200having its ends208respectively connected to signal circuit board110and TCon board120, stress toward the center from both ends208is applied by the elastic force of FFC200. This stress serves as force pressing creases210of FFC200against chassis unit101of the display panel.

Thus, creases210of FFC200are pressed against chassis unit101of the display panel. FFC200is in contact with chassis unit101of the display panel, with the fold-backs of creases210being at interval We which is shorter than interval Wa between creases210. That is, FFC200is disposed such that interval We of contact portions of the fold-backs of creases210and chassis unit101becomes shorter than interval Wa between adjacent creases210. Thus, between crease210and crease210, by the elastic force of FFC200, a region projecting in an arc-shaped manner toward the back surface side originating from crease210being in contact with chassis unit101is formed (i.e., shield surface206is convex-shaped).

For example, it is assumed that the FFC electrically connecting signal circuit board110and TCon board120is set to have a length substantially equal to spaced-apart distance Wb between connector111and connector121without having any creases210. With this structure, the FFC is less likely to be brought into contact with chassis unit101of the display panel and hence ideal. However, actually, during manufacture of the FFC, the length of the FFC may be varied, and the FFC being shorter than spaced-apart distance Wb between connector111and connector121may be manufactured. Such an FFC cannot be used for display apparatus100. In order to prevent an occurrence of such a problem, the FFC must be longer than spaced-apart distance Wb between connector111and connector121. However, when signal circuit board110and TCon board120are electrically connected to each other by the FFC being simply greater in length and having no creases210, a “sag” may occur. Then, unexpected surface contact may occur between the FFC and chassis unit101of the display panel.

In the present exemplary embodiment, FFC200is set to be longer than spaced-apart distance Wb, and to be provided with creases210. Thus, it becomes possible to avoid the problem that a short FFC that cannot electrically connect between the connectors is manufactured because of variations during manufacture. Further, when signal circuit board110and TCon board120are electrically connected to each other by FFC200, by the elastic force of FFC200, the force pressing creases210against chassis unit101of the display panel can be produced at FFC200. Thus, at FFC200, the region projecting in an arc-shaped manner toward the back surface side originating from creases210is formed between crease210and crease210, and the fold-back of crease210is pressed against chassis unit101of the display panel. Accordingly, with display apparatus100, by being supported by creases210, FFC200can be kept in a stable state on chassis unit101of the display panel.

In the present exemplary embodiment, furthermore, as shown inFIG. 5B, wire harness300is disposed at the position of crease210of FFC200, whereby crease210is clamped between chassis unit101of the display panel and wire harness300. In order to keep this state, wire harness300may be fixed to chassis unit101by adhesive tape400or the like. Thus, to FFC200, the force pressing crease210against chassis unit101of the display panel is applied by wire harness300, and crease210of FFC200is prevented from floating upward from chassis unit101. Accordingly, FFC200can be kept on chassis unit101in more stable state.

In connection with display apparatus100structured as described above, the relationship between the frequency of signals transmitted through FFC200and the attenuation amount will be described.

FIG. 6is a diagram showing the relationship between the frequency of signals flowing through FFC200provided to display apparatus100according to the first exemplary embodiment and the attenuation amount. InFIG. 6, the horizontal axis indicates the frequency of signals (GHz). The vertical axis indicates the attenuation amount of signals (dB), and shows that as the position is lower (as the negative value is greater), the attenuation amount is greater.

Note that, the graphs shown inFIG. 6are a collection of results of experiments in which signal circuit board110and TCon board120are electrically connected to each other with FFC200having a length of about 400 mm, and the amplitude ratio between input signals and output signals is measured while varying the frequency of the signals transmitted through FFC200. Further,FIG. 6shows graphs Q, R1, and R2for comparison with graph P representing the experimental result based on the structure according to the present exemplary embodiment.

InFIG. 6, graph P is a graph showing the relationship between the frequency of signals flowing through FFC200and the attenuation amount, in the case where five creases210are provided to FFC200at an interval of about 50 mm, with fold-back width Wd of each crease210being set to several mm (about 5 mm), and the five creases210are brought into contact with chassis unit101of the display panel with the structure similar to that described above.

Graph Q is a graph showing the relationship between the frequency of signals flowing through FFC200and the attenuation amount, in the case where no creases210are provided to FFC200and FFC200is fixed to chassis unit101of the display panel by adhesive tapes having a length of 40 mm at five sites at a certain interval. That is, with this structure, five discrete sites in FFC200(the total region: 5×40 mm=200 mm) are in contact with chassis unit101by the adhesive tapes.

Graph R1is a graph showing the relationship between the frequency of signals flowing through FFC200and the attenuation amount, in the case where no creases210are provided to FFC200and FFC200is caused to have a “sag”. Further, in FFC200, a continuous region having a length of about 200 mm is brought into surface contact with chassis unit101of the display panel using the elastic force of FFC200.

Graph R2is a graph showing the relationship between the frequency of signals flowing through FFC200and the attenuation amount, in the case where no creases210are provided to FFC200and FFC200is fixed to chassis unit101of the display panel by an adhesive tape having a length of 200 mm.

The experiments relating to graphs Q, R1, and R2are identical to one another in that a region of about 200 mm in FFC200is in contact with chassis unit101of the display panel.

Note that, inFIG. 6, a broken line represents the base line showing the lower limit of the attenuation amount that does not substantially influence the image displayed on the display unit of display apparatus100. Accordingly, from the graphs ofFIG. 6, it can be seen that, when the attenuation amount is greater than the base line (when a graph is positioned lower than the base line), the image displayed on the display unit may be influenced in any manner; and when the attenuation amount is smaller than the base line (when a graph is positioned higher than the base line), the image displayed on the display unit is not substantially influenced.

As shown inFIG. 6, in graph Q, the attenuation amount does not fall below the base line at any frequency (i.e., the graph is positioned higher than the base line). On the other hand, in both of graph R1and graph R2, there are regions where the attenuation amount falls below the base line (i.e., the regions being positioned lower than the base line).

It is considered that the difference between the experimental result represented by graph Q and the experimental results represented by graphs R1and R2is attributed to whether FFC200and chassis unit101of the display panel are in contact discretely (graph Q) or continuously (graphs R1and R2). In each of the experiments of graphs Q, R1, and R2, the sum of the lengths of FFC200being in contact with chassis unit101is equally 200 mm. However, from a comparison between graph Q and graphs R1and R2, it can be seen that the attenuation amount of signals becomes greater when FFC200and chassis unit101are continuously in contact with each other, and the attenuation amount of signals becomes smaller when they are discretely in contact with each other.

From the foregoing, it can be seen that, in order to suppress the attenuation amount of signals transmitted through FFC200, when FFC200and chassis unit101are brought into contact with each other, it is desirable that the contact portions are provided so as to be discrete from one another rather than to be continuous.

Note that, it is considered that the difference between the experimental result represented by graph R1and the experimental result represented by graph R2is attributed to whether FFC200and chassis unit101are in contact with each other by the elastic force or the like of FFC200(graph R1) or by the adhesive tape (graph R2). From a comparison between graph R1and graph R2, it can be seen that the attenuation amount becomes greater when FFC200is fixed to chassis unit101using the adhesive tape. From the foregoing, it can be seen that it is desirable not to use an adhesive tape or the like in bringing FFC200and chassis unit101into contact with each other.

Next, graph P will be described. As shown inFIG. 6, comparing graph P and graph Q against each other, graph Q is slightly greater in the attenuation amount than graph P.

It is considered that the difference between the experimental result represented by graph P and the experimental result represented by graph Q is attributed to the difference in the contact area between FFC200and chassis unit101of the display panel. In the experiment of graph P, the width of the fold-back provided to crease210is several mm (about 5 mm). On the other hand, in the experiment of graph Q, the width of the fold-back provided to crease210is about 40 mm. From a comparison between graph P and graph Q, it can be seen that the attenuation amount becomes smaller as the contact area between FFC200and chassis unit101is smaller.

However, in both of graph P and graph Q, the attenuation amount does not fall below the base line (the graphs are positioned higher than the base line). Therefore, it is considered that the structure used at the experiment of graph P and the structure used at the experiment of graph Q pose substantially no problem in displaying the image. Accordingly, it is considered that the acceptable width of the fold-back provided to crease210is up to about 40 mm (posing substantially no problem to the displayed image).

From the foregoing, in the present exemplary embodiment, creases210are provided to FFCs200electrically connecting between signal circuit board110and TCon board120, and FFCs200are disposed at display apparatus100such that the fold-backs provided to creases210are discretely in contact with chassis unit101of the display panel. In this manner, the contact portions between FFC200and chassis unit101are discretely disposed, and the contact area is relatively reduced. Thus, even when signals which are transmitted and received between the circuit boards are high-frequency signals (several GHz), the attenuation amount of the high frequency signals while being transmitted through FFC200can be reduced.

Note that, as described above, the width of the fold-back provided to each crease210is desirably as narrow as possible. However, it cannot physically be “0”. The lower limit of the width of the fold-back provided to crease210is determined based on the physical property or the like of the material of FFC200. From the foregoing, though the width of the fold-back provided to crease210is about 5 mm to 40 mm herein, the present exemplary embodiment does not limit the width of the fold-back provided to crease210to such values.

[1-3. Effect and Others]

As described above, in the present exemplary embodiment, an electronic device includes: a first circuit board on which a first circuit is mounted; a second circuit board on which a second circuit is mounted; a supporter; and a flexible flat cable. The flexible flat cable is disposed on the supporter and connects the first circuit board and the second circuit board to each other. The flexible flat cable transmits a signal between the first circuit and the second circuit. The flexible flat cable is provided with a crease. The flexible flat cable is disposed such that the crease is in contact with the supporter.

The flexible flat cable may be disposed such that a region projecting in an arc-shaped manner originating from the crease being in contact with the supporter is formed.

The flexible flat cable may have a plurality of creases. The flexible flat cable may be disposed such that an interval between adjacent ones of contact portions is smaller than an interval between adjacent ones of the creases, each of the contact portions is a portion where the crease is in contact with the supporter.

The flexible flat cable may include a shield surface and a signal surface. The crease may be formed such that the shield surface is valley-folded and the signal surface is mountain-folded.

Further, in the present exemplary embodiment, a display apparatus includes: a display panel having a display unit displaying an image and a supporter supporting the display unit; a first circuit board on which a first circuit is mounted; a second circuit board on which a second circuit is mounted; and a flexible flat cable. The flexible flat cable is disposed on the supporter and connects the first circuit board and the second circuit board to each other. The flexible flat cable transmits a signal between the first circuit and the second circuit. The flexible flat cable is provided with a crease. The flexible flat cable is disposed such that the crease is in contact with the supporter.

Note that, in the present exemplary embodiment, display apparatus100is one example of the above-described electronic device or display apparatus; chassis unit101is one example of the above-described supporter; the signal processing circuit is one example of the above-described first circuit; the drive circuit is one example of the above-described second circuit; signal circuit board110is one example of the above-described first circuit board; TCon board120is one example of the above-described second circuit board; FFC200is one example of the above-described flexible flat cable; crease210is one example of the above-described crease; interval We is one example of the above-described “interval between adjacent ones of contact portions”; interval Wa is one example of the above-described “interval between adjacent ones of the creases”; shield surface206is one example of the above-described shield surface; and signal surface207is one example of the above-described signal surface.

In conventional techniques, in an electronic device in which a plurality of circuit boards are connected to each other by an FFC, for the purpose of preventing surface contact between a supporter formed by a metal material and the FFC, generally measures for providing a clearance gap between the supporter and the FFC are taken, for example by supporting the FFC with a resin clamper or the like, or inserting an insulating member such as a sponge between the supporter and the FFC. Alternatively, for the purpose of preventing attenuation of signals even when surface contact occurs, measures may be taken by using a double-sided shield type FFC provided with shield layers for shielding electromagnetic noises at respective opposite surfaces, or a micro-coaxial cable. However, such measures are not desirable, because they may invite an increase in the number of components of the electronic device or in the cost of the components.

However, according to the present disclosure, as shown in the exemplary embodiment as one example, creases210provided to FFCs200are in contact with chassis unit101to thereby support FFCs200. Therefore, without employing the structures of the conventional techniques, FFCs200can be kept on chassis unit101in a stable state while surface contact between FFCs200and chassis unit101is prevented. Furthermore, the contact portions between FFCs200and chassis unit101are discretely disposed, and the contact area is also relatively small. Therefore, even when signals which are transmitted and received between the circuit boards are high-frequency signals (several GHz), the attenuation amount of the high frequency signals while being transmitted through FFC200can be reduced.

Thus, even with an electronic device in which high frequency signals are transmitted and received between circuit boards and in which the spaced-apart distance between the circuit boards is relatively great, such as a liquid crystal television set including a large-screen 4k2k panel, the attenuation amount of high frequency signals transmitted through an FFC can be reduced. Accordingly, without employing the structures of the conventional techniques described above, high frequency signals can be stably transmitted and received between circuit boards via an FFC.

Other Exemplary Embodiments

In the foregoing, as an example of the technique disclosed in the present application, the first exemplary embodiment has been described. However, the technique of the present disclosure is not limited thereto, and the present technique can be applicable to exemplary embodiments obtained through modification, replacement, addition, omission and the like of the first exemplary embodiment. Further, it is also possible to obtain a new exemplary embodiment by combining the constituent elements described in the first exemplary embodiment.

Therefore, in the following, other exemplary embodiments will be exemplarily shown.

In the first exemplary embodiment, as one example of the electronic device, display apparatus100has been described. However, the electronic device is not limited to display apparatus100. The electronic device is just required to include a plurality of circuit boards connected to each other by an FFC, wherein signals are transmitted and received between the circuit boards via the FFC. Accordingly, the electronic device may be a display apparatus including a panel other than liquid crystal panel (for example, an EL (Electro Luminescence) panel or the like), a video signal recording apparatus such as a video camera, a mobile terminal apparatus, a measuring apparatus, a manufacturing apparatus, a personal computer, a server computer or the like.

Further, in the first exemplary embodiment, as one example of the supporter, chassis unit101has been described. However, the supporter is not limited to chassis unit101. With the electronic device including a plate-like element formed by a metal material (a metal plate or the like) as the supporter, the effect similar to that described in the present exemplary embodiment can be obtained.

Still further, with an FFC whose both the surfaces are the signal surfaces (that is, an FFC without the shield layer), by employing the structure similar to that described in the first exemplary embodiment, the effect similar to that described in the first exemplary embodiment can be obtained.

Still further, the signals transmitted through the FFC may not be high frequency signals of a GHz band. The signals transmitted through the FFC may be signals of a MHz band or a kHz band.

Still further, the first circuit may be a circuit other than the signal processing circuit, and the second circuit may be a circuit other than the drive circuit.

Note that, the numerical values described in the present exemplary embodiment such as the number of creases210provided to FFC200, the interval of creases210, and the width of the fold-back are merely an example, and the present disclosure is not limited to such numerical values. The number of the creases provided to the FFC, the interval of the creases, and the width of the fold-back and the like are desirably properly set according to the specification and size of the electronic device (or the display apparatus) in which the FFC is used, the material or size of the FFC and the like.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to an electronic device in which high frequency signals transmitted and received between circuit boards are transmitted through an FFC. Specifically, the present disclosure is applicable to a display apparatus such as a television receiver or a monitor apparatus, a video signal recording apparatus such as a video camera, a mobile terminal apparatus, a measuring apparatus, a manufacturing apparatus, a personal computer, a server computer and the like.

REFERENCE MARKS IN THE DRAWINGS