Display device and portable terminal

The present invention relates to a display device and a mobile terminal that are suitable for application when, for example, a scene on the back surface of a display is transparently displayed on a display surface while images, characters, and the like are also displayed on the display surface.

Conventionally, a display device including a transparent display in which information such as figures and characters can be displayed on the display surface of the display and the scene on the back of the display can be seen through has been developed. As a result of advanced development competition using various materials, a display device using a polymer-dispersed liquid crystal (polymer network liquid crystal) inside a transparent display is being put into practical use. The polymer-dispersed liquid crystal is suitable for transparent display applications because it disperses the incoming light when the applied voltage is turned off and transmits the light as it is when the voltage is turned on.

FIG. 5 shows a simplified example of using the transparent display 100. The transparent display 100 is provided in a display device (not shown), and displays a background, a figure, characters, and the like in a rectangular frame of the display area 102. When the transparent display 100 is used to transmit the background 101, the transparent mode is set by applying a voltage to the polymer-dispersed liquid crystal 112 (see FIG. 6 described later), and the background 101 is transmitted and displayed in the transparent mode display area 104. Will be done. Further, when displaying figures, characters, etc. on the transparent display 100, the dispersion mode is set by not applying a voltage to the polymer dispersed liquid crystal, and the figures, characters, etc. are displayed in the dispersion mode display area 103.

FIG. 6 shows a configuration example of each layer of the transparent display 100 when viewed in cross section, and an example of a change in light rays due to mode switching.

FIG. 6A shows an example of a ray in transmission mode. The transparent display 100 is configured by laminating a first glass plate 111, a polymer-dispersed liquid crystal 112, and a second glass plate 113. The first glass plate 111 and the second glass plate 113 are provided with a first electrode 110a and a second electrode 110b, and each electrode is connected to a power source 114 via a conducting wire. A switch 115 for switching the voltage on or off is provided between the power supply 114 and the lead wire of the first electrode 110a. When the switch 115 is turned on, a voltage is applied to the polymer-dispersed liquid crystal 112, and the liquid crystals are aligned. Therefore, the light beam 116 incident from the outside passes through the transparent display 100. At this time, when the user looks at the transparent display 100 from the side of the second glass plate 113, the background on the side of the first glass plate 111 can be seen.

FIG. 6B shows an example of light rays in distributed mode. When the switch 115 is turned off, the voltage applied to the polymer-dispersed liquid crystal 112 becomes zero, and the liquid crystal is dispersed. Therefore, the light beam 116 incident from the outside is dispersed to the surroundings as the dispersed light 117 in the polymer-dispersed liquid crystal 112. At this time, when the user looks at the transparent display 100 from the side of the first glass plate 111, the second glass plate 113 becomes opaque.

Patent Document 1 discloses a technique for illuminating a polymer-dispersed liquid crystal so as to eliminate uneven brightness by sandwiching a substance having no difference in refractive index between the polymer-dispersed liquid crystal and a light guide plate.

<p><patcit num="1"><text>Jikkenhei 6-28837 Gazette</text></patcit></p>

<p> By the way, in a place where the outside light is strong such as outdoors, a large amount of light enters the display, and the light is easily dispersed. At this time, the user can easily see the information such as figures and characters displayed on the display surface of the display. However, when the surrounding environment becomes dark, the amount of light entering is reduced and it becomes difficult for the light to be dispersed in the display, so that the user feels that the information such as figures and characters displayed on the display surface is difficult to see.</p><p> In order to make the displayed information easier to see even in a dark environment, it is necessary to illuminate the polymer-dispersed liquid crystal with a lighting fixture, and generally, a backlight or a front light is provided in the display body. .. However, since the backlight itself is opaque, a transparent display cannot be realized simply by providing a backlight on the back surface of the display. Further, when a front light is used, an optical design is required, so that the manufacturing cost tends to be high.</p><p> Further, although Patent Document 1 discloses a technique for making information displayed on a display surface easy to see by using a plain acrylic plate having no optical design, an opaque black plate is arranged on the display. Therefore, it is not suitable for use as a transparent display. Further, in this device, the light of the light emitting portion escapes from the surface opposite to the light input surface of the light guide plate, so that the light efficiency deteriorates.</p><p> The present invention has been made in view of such a situation, and an object of the present invention is to make it easier for the user to recognize figures, characters, etc. displayed on the display surface while transmitting the background even in a dark environment. And.</p>

<p> In the display device according to the present invention, a first electrode connected to a power source is formed and a first glass plate that transmits light is formed, and a second electrode connected to the power source is formed and transmits light. It is sealed between the second glass plate and the first and second glass plates, and when the voltage supplied from the power supply via the first and second electrodes is turned on, light is transmitted and the voltage is turned off. A light dispersion part that disperses light in such a case, a transparent part that is laminated on a second glass plate and has a predetermined refractive index and transmits light, and a transparent part that is laminated on the transparent part and has a lower refractive index than the transparent part. A light guide plate that emits light on the side that is visible to the user, a light emitting unit that is arranged on the side of the light guide plate and emits light, and a display that switches on or off the voltage applied to the first and second electrodes. It includes a control unit.</p><p> Further, in the portable terminal according to the present invention, a first electrode connected to a power source is formed to form a first glass plate that transmits light, and a second electrode connected to the power source is formed to transmit light. It is sealed between the second glass plate and the first and second glass plates, and when the voltage supplied from the power supply via the first and second electrodes is turned on, light is transmitted and the voltage is transmitted. A light dispersion part that disperses light when turned off, a transparent part that is laminated on a second glass plate and has a predetermined refractive index and transmits light, and a transparent part that is laminated on the transparent part and has a lower refraction than the transparent part. A light guide plate that has a rate and emits light on the side that is visible to the user, a light emitting unit that is arranged on the side surface of the light guide plate and emits light, and turns on or off the voltage applied to the first and second electrodes. It includes a display control unit for switching and a communication unit for communicating by a predetermined communication method.</p><p> By doing so, it is possible to display the information displayed in the opaque portion while transmitting the background light through the transparent portion.</p>

<p> According to the present invention, light entering from the side surface of the light guide plate laminated on the first and second glass plates sandwiching the light dispersion portion is transmitted to the transparent plate having a higher refractive index than the light guide plate. Light reaches from the light guide plate to the light dispersion part. Therefore, even in a dark environment, the background is transmitted through the light dispersion part and displayed on the display surface, and figures, characters, etc. are clearly displayed on the display surface, which has the effect of improving the visibility of the user. There is.</p>

<figref num="1">It is a block diagram which shows the internal structure example of the mobile terminal in one Embodiment of this invention.</figref><figref num="2">It is explanatory drawing which shows the example which made the cross-sectional view of the transparent display in one Embodiment of this invention.</figref><figref num="3">It is explanatory drawing which shows the example which took the cross-sectional view of the transparent display which removed the adhesive sheet in one Embodiment of this invention.</figref><figref num="4">It is explanatory drawing which shows the example of cross-sectional view of the transparent display provided with the reflective sheet in one Embodiment of this invention.</figref><figref num="5">It is explanatory drawing which shows the use example of the conventional transparent display.</figref><figref num="6">It is explanatory drawing which shows the composition example of each layer in the cross-sectional view of the conventional transparent display, and the example of the change of the light ray by the mode switching.</figref>

Hereinafter, the best mode for carrying out the invention (hereinafter referred to as the embodiment) will be described. The explanation will be given in the following order. 1. Embodiment (example of a mobile terminal equipped with a transparent display) 2. Modification example

&lt;1. First Embodiment&gt; [Overall configuration example of mobile terminal]

FIG. 1 shows an example of the internal configuration of the mobile terminal 1 according to the present embodiment. In the example of the present embodiment (hereinafter referred to as this example), a wireless telephone line is set up with the base station by various wireless communication methods such as a CDMA method (Code Division Multiple Access). This is an example applied to the mobile terminal 1 that performs wireless communication. The mobile terminal is built in a small housing so that the user can always carry it. The mobile terminal 1 of this example includes a power source 17 that supplies electric power to each part. For the power source 17, for example, a secondary battery (lithium battery) is used.

The mobile terminal 1 is a wireless communication unit for performing wireless communication with a base station for wireless telephones, and includes a communication circuit 13 for wireless telephones that communicates by a predetermined communication method. An antenna 11 is connected to the radiotelephone communication circuit 13. Although not shown, a communication circuit for relatively short-range wireless communication for Bluetooth (registered trademark) or wireless LAN (Local Area Network) may be provided in addition to the communication circuit for this wireless telephone.

The wireless communication in the wireless telephone communication circuit 13 is executed under the control of the control unit 12 of the mobile terminal 1, and the control unit 12 functions as a communication control unit. The control unit 12 also controls processing such as wireless connection with the base station. The control unit 12 exchanges control data with each unit in the mobile terminal 1 via the control switch 2 and controls each function in the terminal other than wireless communication.

Further, the mobile terminal 1 includes a display unit 14 composed of a liquid crystal display panel or the like, and displays various information under the control of the control unit 12. The display here includes display of outgoing and incoming calls, display of registered information such as phonebook and e-mail address list, display of received and sent e-mails, display of images downloaded by connecting to the Internet, etc. is there.

The display unit 14 of this example includes a transparent display 14a that switches between transparent and opaque depending on whether the voltage supplied from the power supply 17 is turned on or off, and a display control unit 14b that controls the on or off of the voltage applied to the transparent display 14a. A light emitting unit 14c that illuminates the transparent display 14a is provided. The transparent display 14a includes a polymer-dispersed liquid crystal 22 (see FIG. 2 described later) that switches between transparent and opaque depending on whether the voltage is turned on or off, and the display control unit 14b turns on or off the voltage applied to the polymer-dispersed liquid crystal 22. It is equipped with a switch 28 for switching (see FIG. 2 described later). For the light emitting unit 14c, for example, a light emitting diode (LED: Light Emitting Diode) or an organic EL (Electro Luminescence) is used.

The control unit 12 controls a transmission mode in which light is transmitted to the transparent display 14a or a dispersion mode in which light is not transmitted and is opaque. When the control unit 12 is set to the transmission mode, the voltage is turned on by the display control unit 14b, the transparent display 14a becomes transparent, and light is transmitted. At this time, the background can be seen through the transparent display 14a. On the other hand, when the control unit 12 is set to the distributed mode, the voltage is turned off by the display control unit 14b, the transparent display 14a becomes opaque, and light is reflected. At this time, icons, images, characters, etc. are displayed on the transparent display 14a.

Further, the mobile terminal 1 includes an operation unit 15, and the control unit 12 performs various processes based on the operation by the operation unit 15. For example, transmission by wireless telephone communication, transmission / reception of e-mail, start / end of data communication such as access to the Internet, etc. are executed by operating a key prepared as the operation unit 15.

Further, in the mobile terminal 1, the storage unit 16 is connected to the control switch 2 and the data switch 3, and for example, data that needs to be received and stored from the outside is stored in the storage unit 16. Further, the program required for the control process in the control unit 12 is also stored in the storage unit 16. For the storage unit 16, for example, a flash memory, a hard disk drive, or the like is used.

If the packet received by the radiotelephone communication circuit 13 contains voice data, the voice data is taken out. The audio data extracted from the received packet is supplied to the audio processing unit 20 via the data switch 3, demodulated into an analog audio signal, and the demodulated analog audio signal is supplied to the speaker 18 to output audio. Let me.

Further, the mobile terminal 1 includes a microphone 19 into which voice is input, the voice signal picked up by the microphone 19 is modulated into voice data for transmission by the voice processing unit 20, and the modulated voice data is used for radiotelephone communication. Supply to circuit 13. In the radiotelephone communication circuit 13, the supplied voice data is arranged in a packet to be transmitted to the base station and wirelessly transmitted.

FIG. 2 shows an example of a cross-sectional configuration of the transparent display 14a.

In order to realize a transparent display, which has begun to attract attention as an unusual display in recent years, it is effective to adopt a polymer-dispersed liquid crystal (polymer network liquid crystal). However, when the environment becomes dark, the amount of light entering is reduced, and it becomes difficult for the polymer-dispersed liquid crystal to disperse the light, which makes it difficult for the user to see the information displayed on the display surface. Therefore, when the polymer-dispersed liquid crystal is used as a transparent display, making it easy to see in any environment can give a great advantage to the user.

Therefore, in the transparent display 14a of this example, the method of illuminating the light irradiating the polymer-dispersed liquid crystal 22 has been improved. This makes it easier to see images, characters, etc. displayed on the opaque display surface even in a dark environment.

The transparent display 14a of this example is formed with an emphasis on the following points. (1) Form the transparent display 14a with as few members as possible. (2) By arranging a mirror sheet around the light guide plate, loss of light entering from the light emitting part is prevented. (3) It can be realized at low cost by using a light guide plate that is not optically designed.

Further, in a dark environment, lighting is required to recognize the image on the display surface. In order to make a part of the display surface transparent, the members arranged on the front surface and the back surface of the display unit 14 must be transparent members and smooth members that do not deform the displayed image or the like. Is desirable.

The transparent display 14a of this example satisfying the above conditions was incident from the first glass plate 21, the polymer-dispersed liquid crystal 22, the second glass plate 23, the transparent adhesive sheet 24, and the light emitting unit 14c. It is formed by stacking light guide plates 25 that spread light over the entire surface. Each member laminated on the polymer-dispersed liquid crystal 22 has a smooth surface. Further, the transparent display 14a is installed on the side surface of the light guide plate 25, and includes a light emitting unit 14c that allows light to enter the light guide plate 25.

The first glass plate 21 and the second glass plate 23 that transmit light are provided with a first electrode 27a and a second electrode 27b, and each electrode is connected to a power source 17 via a conducting wire. However, a switch 28 for switching the voltage on or off is provided between the power supply 17 and the lead wire of the first electrode 27a. Therefore, the display control unit 14b can switch on or off the voltage applied to the first electrode 27a and the second electrode 27b.

Light is transmitted between the first glass plate 21 and the second glass plate 23 when the voltage supplied from the power supply 17 is turned on via the first electrode 27a and the second electrode 27b. The light dispersion portion that disperses the light when the voltage is turned off is sealed. In this example, the polymer liquid crystal 22 is used as the light dispersion part. The polymer-dispersed liquid crystal 22 is sealed between the first glass plate 21 and the second glass plate 23 to prevent deterioration.

The adhesive sheet 24 has a second glass plate 23 and a light guide plate 25 bonded together. The adhesive sheet 24 is laminated on the second glass plate 23, has a predetermined refractive index, and is used as a transparent portion that transmits light. It is desirable that the refractive index of the pressure-sensitive adhesive sheet 24 is close to the refractive index of the polymer-dispersed liquid crystal 22 and the light guide plate 25.

The light guide plate 25 that surface-emits the light incident from the light emitting unit 14c is made of a transparent member such as acrylic resin or glass that is not optically designed, and is laminated on the adhesive sheet 24. The refractive index of the light guide plate 25 is lower than that of the adhesive sheet 24. Therefore, the light that passes through the light guide plate 25 and reaches the pressure-sensitive adhesive sheet 24 passes through the pressure-sensitive adhesive sheet 24 at a predetermined refraction angle and reaches the second glass plate 23 and the polymer-dispersed liquid crystal 22.

When the switch 28 is turned on, a voltage is applied to the polymer-dispersed liquid crystal 22, the internal liquid crystals are aligned, and the light incident from the outside is transmitted through the transparent display 14a. At this time, when the user looks at the transparent display 14a from the side of the light guide plate 25, the background on the side of the first glass plate 21 can be seen. On the other hand, when the switch 28 is turned off, the liquid crystal of the polymer-dispersed liquid crystal 22 is disturbed. Therefore, the light incident from the outside is dispersed in the polymer-dispersed liquid crystal 22.

Here, an operation example of the transparent display 14a when the adhesive sheet 24 is removed will be described with reference to FIG.

FIG. 3 shows an example of a cross-sectional view of the transparent display 14a from which the adhesive sheet 24 has been removed. When the adhesive sheet 24 disappears, there is an air layer between the light guide plate 25 and the polymer-dispersed liquid crystal 22. In this case, (refractive index of the light guide plate 25)&gt; (refractive index of the air layer), so that the light having an incident angle exceeding the critical angle is reflected before reaching the polymer-dispersed liquid crystal 22, and the user can disperse the polymer. It is difficult to recognize the figures, characters, etc. displayed on the display surface by the liquid crystal 22. Therefore, the transparent display 14a is required to include the adhesive sheet 24.

According to the mobile terminal 1 according to the present embodiment described above, light is received from the side surface of the light guide plate 25 laminated on the first glass plate 21 and the second glass plate 23 sandwiching the polymer-dispersed liquid crystal 22. In order to transmit the light through the pressure-sensitive adhesive sheet 24 having a refractive index higher than that of the light guide plate 25, the light reaches from the light guide plate 25 to the polymer-dispersed liquid crystal 22. Further, the light guide plate 25 disperses the light over the entire surface and surface-emits the light incident from the light emitting unit 14c. Therefore, even in a dark environment, the polymer-dispersed liquid crystal in a dispersed state while allowing the background to pass through clearly displays figures, characters, and the like, which has the effect of improving user visibility.

&lt;2. Modification example&gt; In addition, in order to increase the amount of light when the light guide plate 25 emits light from the surface, the light guide plate 25 may be provided with a reflecting portion that reflects light. FIG. 4 shows an example of a cross-sectional view of a transparent display 14a provided with a reflective sheet 26 that reflects light as a reflecting portion.

The transparent display 14a of this example is arranged on the side surface of the light guide plate 25 facing the light emitting unit 14c, and includes a reflective sheet 26 that reflects light transmitted through the light guide plate 25. The reflective sheet 26 is formed of a material that reflects light, such as an ESR (Enhanced Specular Reflector) sheet. Then, the reflective sheet 26 is brought into close contact with the side surface of the light guide plate 25, and the light transmitted through the light guide plate 25 is returned to the light guide plate 25 along the optical path 29, so that the loss of light is reduced and the amount of light on the display surface is increased. Therefore, even if the low-brightness light-emitting unit 14c is used, it is possible to illuminate the figures, characters, etc. displayed on the display surface with the same brightness as the transparent display 14a without the reflective sheet 26, and the user's visibility. Is improved.

Further, each plate shown in FIG. 2 may be laminated on the side where the user views the light guide plate 25 to form a transparent display. As a result, even if the transparent display is turned inside out, the same functions and effects as those of the transparent display 14a according to the above-described embodiment can be obtained.

Further, the transparent display 14a according to the above-described embodiment displays the background as it is on the display surface when a voltage is applied to the polymer-dispersed liquid crystal 22, but the lower layer of the polymer-dispersed liquid crystal 22 (for example, A reflective sheet or a colored sheet may be arranged on the interface) between the first glass plate 21 and the polymer-dispersed liquid crystal 22).

Further, the transparent display 14a according to the above-described embodiment is designed to display information by using the polymer-dispersed liquid crystal 22, but is also applied to a display device that reflects light such as a reflective liquid crystal and electronic paper. it can.

Further, instead of the adhesive sheet 24, an adhesive that becomes transparent when cured may be used. Further, as the light emitting unit, another lighting device may be used in addition to the LED.

1 ... Mobile terminal, 2 ... Control switch, 3 ... Data switch, 11 ... Antenna, 12 ... Control unit, 13 ... Radiotelephone communication circuit, 14 ... Display unit , 14a ... transparent display, 14b ... display control unit, 14c ... light emitting unit, 15 ... operation unit, 16 ... storage unit, 17 ... power supply, 18 ... speaker, 19 ... Microphone, 20 ... Audio processing unit, 21 ... 1st glass plate, 22 ... Polymer dispersion liquid crystal, 23 ... 2nd glass plate, 24 ... Adhesive sheet, 25 ... light guide plate, 26 ... reflective sheet, 27a ... first electrode, 27b ... second electrode, 28 ... switch, 29 ... optical path