JP6290928B2 - Electronic device and translucent cover substrate for electronic device - Google Patents

Description

  The present invention relates to an electronic device and a translucent cover substrate for the electronic device.

  2. Description of the Related Art Conventionally, electronic devices such as digital cameras and mobile phones that incorporate image display devices such as so-called liquid crystal panels and organic EL panels have been used. In recent years, portable electronic devices referred to as so-called smartphone terminals and tablet terminals that display a relatively large image and include an input device such as a touch panel have been rapidly spreading. The characteristics required for image display devices used in such electronic devices are that the size of the image display surface is relatively large, the thickness in the direction perpendicular to the image display surface is thin, and inexpensive. Yes. In recent electronic devices, so-called tempered glass made of, for example, aminosilicate glass is mainly used as a translucent cover substrate that protects the image display surface of an image display device.

  In an image display device having an image display surface in which pixels are periodically arranged such as a liquid crystal panel, a mesh-like black portion called a black matrix exists in a gap between pixels for constituting an image. When a relatively large liquid crystal panel is manufactured by a relatively inexpensive manufacturing process, the size of the pixels constituting the image and this mesh-like black portion called a black matrix tends to increase.

  In such a large and inexpensive image display device, the black matrix between pixels becomes large enough to be confirmed by the observer of the image display device, and the quality (image quality) of the image visually recognized by the observer is degraded by this black matrix. easy. Conventionally, in order to suppress the deterioration of image quality due to such a black matrix, a diffraction grating, a lenticular lens, or the like is provided between a display device such as a liquid crystal panel and the viewer side to disperse one light into a plurality of optical paths. In addition, a technique for making the black matrix inconspicuous by forming an image of the dispersed light on the black matrix portion is also used. For example, Patent Document 1 below discloses an image display device including a plurality of optical filters that diffuse light from each pixel on an image display surface of a liquid crystal panel in a plurality of directions using diffraction and refraction.

JP 2002-107540 A

  However, as in Patent Document 1, for example, when a plurality of optical filters are arranged between the liquid crystal panel and the translucent cover substrate, the thickness of the image display device itself (thickness in the direction perpendicular to the image display surface). ) Is relatively large, and as a result, there is a problem that the electronic device becomes large.

In order to solve the above-described problem, the present invention includes an image display device having an image display surface in which a plurality of pixels are disposed via inter-pixel regions, and one main surface disposed to face the image display surface. an electronic device and a light-transmitting cover substrate having the light-transmitting cover substrate is made from a single crystal body mainly composed of alumina (Al 2 _{O 3),} the one main surface is the single The refractive index of the translucent cover substrate with respect to ordinary light L ′ which is inclined with respect to the C-plane (0001) of the crystal and is perpendicular to the c-axis of the single crystal is denoted by no, and the single crystal Flat against the c-axis
The refractive index of the translucent cover substrate with respect to extraordinary light L ″ having a linear polarization is represented by ne,
When the inclination angle of the one main surface with respect to the C plane (0001) of the body is θ, the thickness of the translucent cover substrate is t, and the width of the adjacent inter-pixel region on the image display surface is W ( The present invention provides an electronic device characterized by satisfying the relationship of no ² −ne ² ) tan θ / (no ² tan ² θ + ne ² ) × t <W .

  According to the present invention, it is possible to configure a relatively small electronic device in which deterioration in image quality due to the black matrix is suppressed.

(A) It is a perspective view which shows the external appearance of an electronic device, (b) is a perspective view of the translucent cover board | substrate for electronic devices with which the electronic device shown to (a) is equipped. It is a top view which shows the external appearance of an electronic device. It is a back view which shows the external appearance of an electronic device. It is sectional drawing which shows an electronic device. It is a figure which extracts and shows a part of image display device 52 and the translucent cover board | substrate 1 for electronic devices among the structural members of the electronic device 100, (a) is a perspective view, (b) is sectional drawing. It is. It is a fragmentary sectional view explaining other embodiment of electronic equipment. It is a block diagram which shows the electric constitution of an electronic device. It is a top view which shows a piezoelectric vibration element. It is a side view which shows a piezoelectric vibration element. It is a figure which shows a mode that a piezoelectric vibration element bends. It is a figure which shows a mode that a piezoelectric vibration element bends. It is the top view which looked at the translucent cover board | substrate for electronic devices provided with a piezoelectric vibration element from the one main surface side. It is a figure for demonstrating an air conduction sound and a conduction sound.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Appearance of electronic equipment>
FIG. 1A is a perspective view showing an external appearance of an electronic device 100 of the present invention, and FIG. 1B is a translucency for the electronic device of the present invention provided in the electronic device shown in FIG. It is a perspective view of a cover substrate. FIG. 2 is a front view showing the appearance of the electronic device 100, and FIG. 3 is a rear view of the electronic device 100. The electronic device 100 according to the present embodiment is a mobile phone, for example. FIG. 4 is a cross-sectional view of the electronic device 100. FIG. 5 is a diagram showing a part of the components of the electronic device 100 extracted from the image display device 52 and the translucent cover substrate 1 for electronic devices (also simply referred to as translucent cover substrate 1). (A) is a perspective view and (b) is a cross-sectional view. In FIG. 5, a touch panel 53 described later is omitted for simplification of description.

  As shown in FIGS. 1 to 5, the electronic device 100 includes an image display device 52 having an image display surface 52 a in which a plurality of pixels 521 are arranged via inter-pixel regions 522, a translucent cover substrate 1, A case portion 2 is provided. The translucent cover substrate 1 is a rectangular substrate in plan view. The translucent cover substrate 1 and the case portion 2 are combined to form a device case 3.

  The translucent cover substrate 1 has one main surface 1A facing the image display surface 52a and the other main surface 1B opposite to the one main surface 1A. The translucent cover substrate 1 has one main surface 1 </ b> A arranged in parallel to the image display surface 52 a of the image display device 52. The translucent cover substrate 1 is provided with a display portion 1a on which various information such as characters, symbols and figures are displayed. The display portion 1a has, for example, a rectangular shape in plan view. The peripheral part 1b surrounding the display part 1a in the translucent cover substrate 1 is black by applying a light shielding film or the like, for example, and is a non-display part where information is not displayed. A touch panel 53, which will be described later, is attached to one main surface 1A of the translucent cover substrate 1, and the operator of the electronic device 100 uses a finger or the like to display the display portion 1a on the other main surface 1B of the translucent cover substrate 1. By operating with, various instructions can be given to the electronic device 100.

The translucent cover substrate 1 is a single crystal body (hereinafter sometimes simply referred to as a single crystal body) containing alumina (Al ₂ O ₃ ) as a main component, and one main surface 1A and the other main surface 1B have a single crystal body. Inclined with respect to the C-plane (0001) of the crystal. A single crystal containing alumina (Al ₂ O ₃ ) as a main component is generally called sapphire, and is less likely to be scratched and harder to crack than tempered glass. In the present specification, when it is contained as a “main component”, it specifically means that it is contained at least 50% by mass, preferably 70% by mass. The purity (content) of Al ₂ O ₃ of the translucent cover substrate 1 is 99 in that it is more difficult to scratch, more reliably suppresses cracking and chipping, and is highly transparent with little coloring. It is preferable that it is mass% or more.

  Sapphire is a so-called birefringent crystal, and the c-axis of sapphire is parallel to an axis (so-called optical axis) along a direction in which light does not separate even when light enters the sapphire (an optical path does not branch). The C-plane (0001) of sapphire perpendicular to the c-axis of sapphire is a plane perpendicular to the optical axis.

  In the translucent cover substrate 1, one main surface 1A facing the image display surface 52a is parallel to the image display surface 52a, and the one main surface 1A is a C surface (0001) perpendicular to the optical axis (C axis) of sapphire. ). In this specification, the one main surface 1A and the other main surface 1B are inclined with respect to the C plane (0001) of the single crystal body. The angle θ formed with the C plane (0001) is 0 ° <θ <90 °.

  In the present embodiment, the one main surface 1A and the other main surface 1B are parallel to the R surface (1-102) of sapphire, and the inclination angle θ with respect to the C surface (0001) of sapphire is about 57.6 °. Yes. In this specification, the term “surface is parallel to the surface” refers to a state where the angle between the surface and the surface is less than 20 °, and is preferably less than 5 °. In the present embodiment, the one main surface 1A and the other main surface 1B are parallel to the R surface of sapphire, but the one main surface 1A and the other main surface 1B are surfaces inclined with respect to the R surface. There is no limitation. The R plane (1-102) is one of the crystal orientations of sapphire, and is one of crystal planes in which aluminum atoms and oxygen atoms are regularly arranged. If the main surface of the translucent cover substrate 1 is parallel to the crystal plane such as the R plane, the flatness of the translucent cover substrate 1 can be made relatively high by mechanical polishing or the like, and stable quality can be achieved at low cost. It is preferable at the point which can manufacture the translucent cover board | substrate 1 of this.

  As described above, the electronic apparatus 100 includes the image display device 52 therein. The image display device 52 is controlled by the control unit 50 to be described later, and displays image information representing characters, symbols, figures, and the like on the image display surface 52a. The image display device 52 is a so-called liquid crystal display panel, and includes a backlight unit (not shown), an optical filter (not shown) including a refraction filter and a color filter, and a liquid crystal layer 520.

  The liquid crystal layer 520 has a planar image display surface 52 a in which a plurality of pixels 521 are arranged via inter-pixel regions 522. As the LED lamp of the backlight unit, an LED lamp that emits white light in which a phosphor is combined with a blue LED element is mainly used. The image information displayed on the image display surface 52a of the image display device 52 is formed by the white light emitted from the LED lamp of the backlight unit being partially colored by passing through the pixels 521 of the liquid crystal layer 520. Has been. Thus, the light L representing the image information displayed on the image display surface 52a is incident from the one main surface 1A of the translucent cover substrate 1 and is emitted from the other main surface 1B to be used by the operator (use of the electronic device 100). The operator recognizes characters, symbols, graphics, and the like represented by the image information.

  The inter-pixel region 522 on the image display surface 52a is a region called a so-called black matrix where the pixels 521 are not arranged, and a data transmission line or the like (not shown) is arranged. The size of the pixel 521 and the inter-pixel region 522 in the liquid crystal layer 520 depends on the pattern formation accuracy in the manufacturing process of the liquid crystal layer 520. If many processes are performed using an expensive device, the size of the pixel 521 and the inter-pixel region 522 can be reduced. However, if these are sufficiently reduced, the manufacturing cost of the liquid crystal layer 520 increases, and as a result The manufacturing cost of the image display device 52 and thus the entire electronic device 100 is increased. In addition, as the size of the image display surface 52a of the liquid crystal layer 520 increases, the pattern formation accuracy in the manufacturing process tends to decrease. As the image display surface 52a increases, the size of the pixel 521 and the inter-pixel region 522 decreases. It is difficult. The liquid crystal layer 520 has a relatively large image display surface 52a, but is manufactured through a relatively low-cost manufacturing process, and the size of the pixels 521 and the inter-pixel regions 522 is relatively large.

  In the electronic device 100, the translucent cover substrate 1 that protects the image display surface 52 a disperses the light transmitted through the pixels 521 of the liquid crystal layer 520 into a plurality of optical paths, and the dispersed light corresponds to the inter-pixel region 522. Since the image is formed on the portion (that is, the black matrix portion), the black matrix can be made inconspicuous, and deterioration in image quality due to the black matrix can be suppressed.

  More specifically with reference to FIG. 5, the translucent cover substrate 1 is inclined with respect to the C plane (0001) perpendicular to the sapphire optical axis (C axis). The light L that has passed through the pixel 521 of the liquid crystal layer 520 and entered perpendicularly to the main surface 1A passes through the translucent cover substrate 1 made of sapphire, which is a birefringent crystal, and is abnormal as normal light L ′. The light L ″ is divided into two polarized light beams. This extraordinary light L ″ forms an image in a region corresponding to a so-called inter-pixel region 522 called a black matrix, so that a user who observes the image display surface 52a can make a black matrix. Also, the user feels light corresponding to the adjacent pixel 521 (light having a color and brightness similar to those of the adjacent pixel 521). This makes it difficult for an observer (an operator of the electronic device 100) to perceive a mesh-like black portion called a black matrix in the observed image. That is, the black matrix becomes inconspicuous for the operator who observes the other main surface 1B of the translucent cover substrate 1, and the deterioration of the image quality due to the black matrix is suppressed.

  In the electronic device 100, the translucent cover substrate 1 itself that protects the image display surface 52a functions as a birefringent substrate, and therefore, a diffraction grating, a lenticular lens, or the like is provided between the translucent cover substrate 1 and the image display device 52. Without providing an optical component, the black matrix can be made inconspicuous and image quality deterioration due to the black matrix can be suppressed. In the electronic device 100, the width of the inter-pixel region 522 between the image display device 52 and the translucent cover substrate 1 is relatively small, and consequently the thickness of the entire electronic device 1 is relatively small. As described above, the electronic device 100 is a relatively small electronic device (thickness is small) in which deterioration of image quality due to the black matrix is suppressed.

  In addition, the liquid crystal layer 520 has a relatively large image display surface 52a, but is manufactured through a relatively low cost manufacturing process, and the size of the pixel 521 and the inter-pixel region 522 is relatively large. Since the black matrix is made inconspicuous by the optical cover substrate 1 and the deterioration of the image quality due to the black matrix is suppressed, the deterioration of the image quality due to the black matrix is sufficiently suppressed. The electronic device 100 is a relatively small (thickness) electronic device that is relatively inexpensive, has a relatively large image display surface, suppresses deterioration in image quality due to a black matrix, and is relatively small. By using the translucent cover substrate 1 as described above, a relatively inexpensive liquid crystal layer 520 having a relatively large inter-pixel region 522 corresponding to the black matrix may be used as the liquid crystal layer 520 of the image display device 52. The operator of electronic device 100 that is an observer can visually recognize a relatively clean image.

  The vibration directions of the two polarized lights of ordinary light L ′ and extraordinary light L ″ shown in FIG. 5B are perpendicular to each other, and the polarization direction of ordinary light L ′ is perpendicular to the c-axis. The polarization direction is parallel to the optical axis c-axis. Here, the refractive index of the translucent cover substrate 1 for each of ordinary light L ′ and extraordinary light L ″ is no, ne, and one main surface 1A of the translucent cover substrate 1 for the C plane (0001) of the single crystal. , The separation width d due to each refraction can be expressed by the following formula (1), where t is the thickness of the translucent cover substrate 1. The difference between no and ne is the degree of birefringence. It can be seen that a material having a large difference in birefringence can be obtained with a thin substrate to obtain the same separation width.

d = (no ² −ne ² ) tan θ / (no ² tan ² θ + ne ² ) × t (1)
The translucent cover substrate 1 is made of sapphire, and one main surface 1A and the other main surface 1B are parallel to the R plane (1-102) of the single crystal. The light transmitting cover substrate has a refractive index no of 1.768,
ne is about 1.760, and the birefringence difference is about 0.008. The translucent cover substrate 1 made of sapphire can have a separation width d of about 2.15 μm even if the thickness perpendicular to the one main surface 1A is relatively thin, for example, about 0.4 mm. it can.

  The refractive index no of the translucent cover substrate 1 with respect to the ordinary light L ′ and the refractive index ne of the translucent cover substrate 1 with respect to the extraordinary light L ″ are so-called spectroscopic ellipsometers (manufactured by Otsuka Electronics, FTM7700W). It can be measured using an ellipsometer.

  Further, the inclination angle θ of the one main surface 1A of the translucent cover substrate 1 with respect to the C-plane (0001) of sapphire can be measured using a crystal orientation measuring device using an X-ray diffraction method. In the crystal orientation measuring device, the translucent cover substrate 1 is set so that the one main surface 1A is at a predetermined angle at a predetermined position, and then the translucent cover substrate 1 is irradiated with X-rays to transmit the translucent light. Measuring the so-called X-ray diffraction intensity representing the state of the single crystal crystal lattice of the cover substrate 1, and measuring the inclination angle direction and inclination direction of the main surface 1A with respect to sapphire based on the X-ray diffraction intensity. Can do. For this measurement, for example, an automatic X-ray crystal orientation measuring device (model 2991F2) manufactured by Rigaku Corporation may be used.

When the width of the two intervals 522 pixel 521 adjacent to is W, so that the amount of separation width d of the black matrix portion corresponding to the picture Motokan region 522 enters the optical path of the extraordinary light L ". Separation width d is preferably larger than ½ of the width W of the inter-pixel region 522 of the pixel 521. That is, it is preferable to satisfy the following formula (2).

W / 2 ≦ (no ² −ne ² ) tan θ / (no ² tan ² θ + ne ² ) × t (2)
In general, the width W of the inter-pixel region 522 is the same over the entire image display surface, but the separation width in the portion where the width W is the largest, such as when the width W of the inter-pixel region 522 is partially different. The thickness t and the tilt angle θ of the translucent cover substrate 1 may be adjusted so that d ≧ W / 2 is satisfied.

  Further, since sapphire is very hard and difficult to break compared with a general transparent material such as glass, for example, even when the translucent cover substrate 1 is relatively thin, cracks and chips are hardly generated. Although the electronic device 100 according to the present embodiment is relatively small, image quality deterioration due to the black matrix is suppressed, and cracks and chips of the translucent cover substrate 1 are suppressed.

  In addition, the electronic device 100 may provide a light transmission layer having a refractive index different from that of sapphire on the other main surface 1B of the translucent cover substrate 1. When such a transmissive layer is provided on the other main surface 1B of the translucent cover substrate 1, the visibility according to the direction in which the translucent cover substrate 1 is viewed can be characterized. FIG. 6 is a partial cross-sectional view illustrating an embodiment in which a light transmissive layer different from sapphire is provided on the other main surface 1 </ b> B of the translucent cover substrate 1. For example, so-called smartphones and tablet terminals are larger in screen size than conventional mobile phone terminals, and it is easy for others close to the operator to see the image displayed on the image display surface, and close to the operator. There are many requests from other people who want to make the image displayed on the image display surface difficult to see. The embodiment shown in FIG. 6 is preferable when it is difficult for others to see the image displayed on the image display surface.

In the embodiment shown in FIG. 6, a light transmission layer 11 made of, for example, diamond-like hard carbon, which is bonded to the other main surface 1 </ b> B of the translucent cover substrate 1 is provided. Refractive index of the light transmission layer 11 N _beta is higher than the refractive index N _alpha of the translucent cover substrate 1. A touch panel 53 is bonded to one main surface 1 </ b> A of the translucent cover substrate 1 via an adhesive layer 59. The adhesive layer 59 has a refractive index _NG ( _NG is approximately 1.45) equivalent to that of the glass member that constitutes the touch panel 53. As an adhesive for joining the touch panel mainly using glass and the translucent cover substrate 1, the refractive index is adjusted to about 1.45 according to the glass like the adhesive layer 59. It is preferable to use an adhesive. Diamond-like hard carbon has an amorphous structure mainly composed of carbon. Diamond having a regular crystal structure, cubic boron nitride (cBN), and hexagonal boron nitride (hBN) Different. When this amorphous diamond-like hard carbon is examined using a Raman spectroscopic analyzer often used for identification of graphite and diamond, the peak position of diamond is 1333 cm ⁻¹ and the vicinity of graphite peak position is 1550 cm ⁻¹ . Each has a peak. In the diamond-like hard carbon film of the present embodiment, the peak may be biased to either diamond or graphite, and is preferably biased to the diamond peak position. Such diamond-like hard carbon has a very hard universal hardness of 20 to 50 GPa and a high wear resistance. For the amorphous diamond-like hard carbon film, thin film forming means such as sputtering, ion plating, PVD, and CVD can be used.

The light transmission layer 11 of the present embodiment is the refractive index N _beta made diamond-like hard carbon is about 2.42. The refractive index N _α of the translucent cover substrate 1 made of sapphire is different between ordinary light and extraordinary light, but is 1.76 here. The refractive index _{N 0} of the air is about 1.00. In FIG. 6, an example of an optical path of light (external light) reaching the other main surface 1B of the translucent cover substrate 1 is indicated by an arrow. This external light corresponds to external environmental light during operation of the electronic device 1 such as sunlight or illumination.

  Reflection and refraction of light passing through this boundary portion occurs at the boundary portion of the layers having different refractive indexes. In particular, it is known that light that has entered at an angle equal to or greater than a certain angle (critical angle) corresponding to the refractive index is totally reflected when the refractive index proceeds from the large refractive index side to the small refractive index side. In the translucent cover substrate 1, external light is transmitted at two places, a boundary portion D 1 between the translucent cover substrate 1 and the light transmission layer 11 and a boundary portion D 2 between the translucent cover substrate 1 and the adhesive layer 59. Total reflection occurs.

At the boundary portion D1 between the translucent cover substrate 1 and the light transmission layer 11, external light incident at an incident angle of θ ₁ or more that satisfies sin θ ₁ = N _α / N _β causes total reflection at the boundary portion D _1. . The refractive index N _beta as described above was about 2.42, the refractive index N _alpha is approximately 1.76, the critical angle (the first critical angle) theta ₁ is around approximately 47 °. The observer viewed from perpendicular from 47 ° or more oblique angle range of the image display surface 52a (the region shown in FIG. 6 E1), reach many reflected light of external light due to total reflection at the boundary portion D _1. When the light spreading from one point of the image display surface 52a is considered, the reflected light of this external light is given to an observer viewed from an angle range (region E1 shown in FIG. 6) inclined by 47 ° or more from the perpendicular of the image display surface 52a Since (reflected light due to total reflection) becomes relatively large, it is difficult to recognize the image information represented by the light from the image display surface 52a.

Electronic device 100 in addition, the boundary portion D2 of the translucent cover substrate 1 and the adhesive layer _{59, sinθ 2 = N G /} N satisfy _beta theta ₂ or more of the light incident at an incident angle of the boundary portion D ₂ Causes total reflection. The refractive index N _beta as described above is about 1.76, the refractive index _{N G} is about 1.45, the critical angle (second critical angle) theta ₂ is approximately 55 ° about. The observer viewed from perpendicular from 55 ° or more oblique angle range of the image display surface 52a (the region shown in FIG. 6 E1), reach many reflected light of external light due to total reflection at the boundary portion D _2. When the light spreading from one point of the image display surface 52a is considered, the reflected light of the outside light is not observed to an observer viewed from an angle range (region E1 shown in FIG. 5) inclined by 55 ° or more from the perpendicular of the image display surface 52a. Since (reflected light due to total reflection) becomes relatively large, it is difficult to recognize the image information represented by the light from the image display surface 52a.

  As described above, in the electronic device 100 having the translucent cover substrate 1, the light (external light) reaching the other main surface 1 </ b> B of the translucent cover substrate 1 is totally reflected in two steps of the boundary portion D <b> 1 and the boundary portion D <b> 2. Occurs. That is, in the electronic device 1 including the translucent cover substrate 1, the image information displayed on the image display surface 52a is visually recognized from the region E1 illustrated in FIG. 6 due to the influence of the total reflected light of the external light at the boundary portion D1. hard. Furthermore, from the area E2 shown in FIG. 6, in addition to the total reflected light of the external light at the boundary portion D1, the total reflected light of the external light at the boundary portion D2 overlaps, and the image information shown on the image display surface 52a is further visually recognized. It is hard to do. That is, in the electronic device 1, the image displayed on the image display surface 52 a is difficult to see from, for example, another person near the operator who is at a relatively large angle with respect to the translucent cover substrate 1. . In particular, in an environment where the intensity (illuminance) of external light such as sunlight or illumination is relatively large compared to the light emitted from the image display device 52, the image displayed on the image display surface 52a becomes significantly less visible. Yes.

  As shown in FIG. 6, when a light transmission layer 11 having a refractive index larger than that of the translucent cover substrate 1 is provided on the other main surface 1B of the translucent cover substrate 1, external light is transmitted from the boundary portion D1 and the boundary portion D2. Is preferable in that the image is more invisible to others. The light transmission layer 11 is not limited to being a diamond-like hard carbon film. For example, zirconia (Zr₂O₃) As a main component, titania (TiO₂), Hafnium oxide (HfO) ₂), Niobium pentoxide (Nb)₂O₅), Tantalum pentoxide (TaO)₅), Zinc oxide (ZnO), and tungsten oxide (WO₃Etc.), for example, as long as it has a relatively high refractive index as compared with sapphire. A diamond-like hard carbon film is preferable in terms of high hardness and high wear resistance. In addition to the embodiment shown in FIG. 6, for example, a light transmissive layer having a refractive index smaller than that of the translucent cover substrate 1 may be provided on the other main surface 1 </ b> B of the translucent cover substrate 1. A light transmission layer may be provided on the one main surface 1A side of the substrate 1. Even in such a case, by adjusting the thickness, refractive index, and the like of the light transmissive layer 11, it is possible to give a characteristic to the visibility according to the direction in which the translucent cover substrate 1 is viewed. Thus, by joining the translucent cover substrate 1 and the light transmissive layer 11 to form an integral substrate member, the strength of the entire substrate member is increased, and the translucent cover substrate 1 is further damaged. It can also be suppressed.

  FIG. 7 is a block diagram showing an electrical configuration of the electronic device 100. As shown in FIG. 7, the electronic device 100 includes a control unit 50, a wireless communication unit 51, an image display device 52, a touch panel 53, a piezoelectric vibration element 55, an external speaker 56, a microphone 57, an imaging unit 58, and a battery 59. These components are housed in the device case 3.

  The control unit 50 includes a CPU 50a (also illustrated in FIG. 4), a storage unit 50b, and the like, and comprehensively manages the operation of the electronic device 100 by controlling other components of the electronic device 100. To do. The storage unit 50b includes a ROM, a RAM, and the like. Various functional blocks are formed in the control unit 50 when the CPU 50a executes various programs in the storage unit 50b. The control unit 50 receives various and large amounts of information from each component, and processes (information processing) these information in a relatively short time. During this information processing, the CPU 50a generates a relatively large amount of heat. If the heat generated by the CPU 50a stays in the device case 3, the temperature in the device case 3 rises, and the operation of the CPU 50a may be slowed or malfunctioned. Component malfunction may also occur.

  The translucent cover substrate 1 made of sapphire has a thermal conductivity of about 42 W / (m · K), for example, thermal conductivity as compared with quartz glass or the like having a thermal conductivity of about 1 W / (m · K). Is big. For this reason, in the electronic device 100, the heat generated from the CPU 50 a can be efficiently released to the outside of the device case 3 through the translucent cover substrate 1. In the electronic device 100 including the translucent cover substrate 1, the heat generated by the CPU 50 a is quickly released to the outside of the device case 3, so that the temperature rise in the device case 3 is suppressed, and the CPU 50 a and other components are Malfunctions are also suppressed.

  As shown in FIG. 3, a speaker hole 20 and a microphone hole 21 are formed in the back surface 101 of the electronic device 100, in other words, the back surface of the device case 3. An imaging lens 58 a included in an imaging unit 58 described later is exposed from the back surface 101 of the electronic device 100.

  The wireless communication unit 51 receives a signal from a communication device such as a mobile phone or a web server connected to the Internet, which is different from the electronic device 100, via the base station by the antenna 51a. The wireless communication unit 51 performs amplification processing and down-conversion on the received signal and outputs the result to the control unit 50. The control unit 50 performs demodulation processing or the like on the input reception signal, and acquires a sound signal indicating voice or music included in the reception signal. The wireless communication unit 51 performs up-conversion and amplification processing on the transmission signal including the sound signal generated by the control unit 50, and wirelessly transmits the processed transmission signal from the antenna 51a. A transmission signal from the antenna 51a is received through a base station by a mobile phone different from the electronic device 100 or a communication device connected to the Internet.

  As described above, the image display device 52 is, for example, a liquid crystal image display device, and displays various information such as characters, symbols, and graphics on the image display surface 52a by being controlled by the control unit 50. The information displayed on the image display device 52 is displayed on the display portion 1 a of the translucent cover substrate 1, so that the information can be visually recognized by the user of the electronic device 100.

  The touch panel 53 is, for example, a projected electrostatic capacitance type touch panel, and detects a user's operation on the display portion 1 a of the translucent cover substrate 1. The touch panel 53 is affixed to the inner main surface of the translucent cover substrate 1 and includes two sheet-like electrode sensors arranged to face each other. The two electrode sensors are bonded together with a transparent adhesive sheet.

  One electrode sensor is formed with a plurality of elongated X electrodes that extend along the X-axis direction (for example, the left-right direction of the electronic device 100) and are arranged in parallel to each other. The other electrode sensor is formed with a plurality of elongated Y electrodes that extend along the Y-axis direction (for example, the vertical direction of the electronic device 100) and are arranged in parallel to each other. When a user's finger comes into contact with the display portion 1a of the translucent cover substrate 1, the capacitance between the X electrode and the Y electrode under the contact portion changes, so that the translucent light is transmitted through the touch panel 53. An operation on the display portion 1a of the conductive cover substrate 1 is detected. The capacitance change between the X electrode and the Y electrode that occurs in the touch panel 53 is transmitted to the control unit 50, and the control unit 50 applies to the display portion 1 a of the translucent cover substrate 1 based on the capacitance change. The content of the operation that has been performed is specified, and the corresponding operation is performed.

  The piezoelectric vibration element 55 is for transmitting the received sound to the user of the electronic device 100. The piezoelectric vibration element 55 is vibrated by a drive voltage supplied from the control unit 50. The control unit 50 generates a drive voltage based on the sound signal indicating the received sound, and applies the drive voltage to the piezoelectric vibration element 55. The piezoelectric vibration element 55 is vibrated by the control unit 50 based on the sound signal indicating the reception sound, whereby the reception sound is transmitted to the user of the electronic device 100. Thus, the control unit 50 functions as a drive unit that vibrates the piezoelectric vibration element 55 based on the sound signal. The piezoelectric vibration element 55 will be described in detail later.

  The external speaker 56 converts the electrical sound signal from the control unit 50 into sound and outputs the sound. Sound output from the external speaker 56 is output to the outside from the speaker hole 20 provided on the back surface 101 of the electronic device 100.

  The microphone 57 converts sound input from the outside of the electronic device 100 into an electrical sound signal and outputs the electrical sound signal to the control unit 50. Sound from the outside of the electronic device 100 is taken into the electronic device 100 through the microphone hole 21 provided on the back surface 101 of the electronic device 100 and input to the microphone 57.

  The imaging unit 58 includes an imaging lens 58 a and an imaging element, and captures still images and moving images based on control by the control unit 50.

  The battery 59 outputs a power source for the electronic device 100. The power output from the battery 59 is supplied to each electronic component included in the control unit 50, the wireless communication unit 51, and the like included in the electronic device 100.

<Details of piezoelectric vibration element>
8 and 9 are a top view and a side view showing the structure of the piezoelectric vibration element 55, respectively. As shown in FIGS. 8 and 9, the piezoelectric vibration element 55 has a long shape in one direction. Specifically, the piezoelectric vibration element 55 has a rectangular elongated plate shape in plan view. The piezoelectric vibration element 55 has, for example, a bimorph structure, and includes a first piezoelectric ceramic plate 55a and a second piezoelectric ceramic plate 55b that are bonded to each other via a shim material 55c. There may be a laminated piezoelectric vibration element in which the shim material 55c is not provided, and piezoelectric ceramic plates and electrodes are alternately laminated, and the polarization directions are different between the upper ceramic ceramic plate and the lower ceramic plate.

  In the piezoelectric vibration element 55, when a positive voltage is applied to the first piezoelectric ceramic plate 55a and a negative voltage is applied to the second piezoelectric ceramic plate 55b, the first piezoelectric ceramic plate 55a extends along the longitudinal direction. The second piezoelectric ceramic plate 55b extends and contracts along the longitudinal direction. As a result, as shown in FIG. 10, the piezoelectric vibration element 55 bends in a mountain shape with the first piezoelectric ceramic plate 55a outside.

  On the other hand, in the piezoelectric vibration element 55, when a negative voltage is applied to the first piezoelectric ceramic plate 55a and a positive voltage is applied to the second piezoelectric ceramic plate 55b, the first piezoelectric ceramic plate 55a is in the longitudinal direction. The second piezoelectric ceramic plate 55b extends along the longitudinal direction. Accordingly, as shown in FIG. 11, the piezoelectric vibration element 55 bends in a valley shape with the second piezoelectric ceramic plate 55b facing outside.

  The piezoelectric vibration element 55 performs flexural vibration by alternately taking the state of FIG. 10 and the state of FIG. 11. The controller 50 flexes and vibrates the piezoelectric vibration element 55 by applying an alternating voltage in which a positive voltage and a negative voltage appear alternately between the first piezoelectric ceramic plate 55a and the second piezoelectric ceramic plate 55b. Let

  Note that the piezoelectric vibration element 55 shown in FIGS. 9 to 10 is provided with only one structure including the first piezoelectric ceramic plate 55a and the second piezoelectric ceramic plate 55b bonded together with the shim material 55c interposed therebetween. However, a plurality of such structures may be stacked.

<Arrangement position of piezoelectric vibration element>
FIG. 12 is a plan view when the translucent cover substrate 1 is viewed from the one main surface 1A side. The piezoelectric vibration element 55 is attached to the one main surface 1A of the translucent cover substrate 1 with an adhesive such as a double-sided tape. The piezoelectric vibration element 55 is located on one main surface 1A of the translucent cover substrate 1 so as not to overlap the image display device 52 and the touch panel 53 in a plan view when the translucent cover substrate 1 is viewed from the one main surface 1A side. Is arranged.

<Generation of incoming call sound due to vibration of piezoelectric vibration element>
In the present embodiment, the piezoelectric vibrating element 55 vibrates the translucent cover substrate 1 so that air conduction sound and conduction sound are transmitted from the translucent cover substrate 1 to the user. In other words, air conduction sound and conduction sound are transmitted from the translucent cover substrate 1 to the user by transmitting the vibration of the piezoelectric vibration element 55 itself to the translucent cover substrate 1.

  Here, the airway sound is a sound that is recognized by the human brain by sound waves (air vibrations) entering the ear canal hole (so-called “ear hole”) vibrating the eardrum. On the other hand, the conduction sound is sound that is recognized by the human brain when the auricle is vibrated and the vibration of the auricle is transmitted to the eardrum and the eardrum vibrates. Hereinafter, the air conduction sound and the conduction sound will be described in detail.

  FIG. 13 is a diagram for explaining air conduction sound and conduction sound. FIG. 13 shows the structure of the ear of the user of electronic device 100. In FIG. 13, a wavy line 400 indicates a conduction path of a sound signal (sound information) when an airway sound is recognized by the brain, and a solid line 410 indicates a conduction path of the sound signal when a conduction sound is recognized by the brain. Is shown.

  When the piezoelectric vibration element 55 attached to the translucent cover substrate 1 is vibrated based on an electrical sound signal indicating a received sound, the translucent cover substrate 1 vibrates, and the translucent cover substrate Sound waves are output from 1. When the user holds the electronic device 100 in his hand and brings the translucent cover substrate 1 of the electronic device 100 close to the user's auricle 200, or the translucent cover substrate 1 of the electronic device 100 is When hitting the user's pinna 200, sound waves output from the translucent cover substrate 1 enter the ear canal hole 210. Sound waves from the translucent cover substrate 1 travel through the ear canal hole 210 and vibrate the eardrum 220. The vibration of the eardrum 220 is transmitted to the ossicle 230, and the ossicle 230 vibrates. Then, the vibration of the ossicle 230 is transmitted to the cochlea 240 and converted into an electric signal in the cochlea 240. This electrical signal is transmitted to the brain through the auditory nerve 250, and the received sound is recognized in the brain. In this way, air conduction sound is transmitted from the translucent cover substrate 1 to the user.

  Further, when the user holds the electronic device 100 in his hand and touches the translucent cover substrate 1 of the electronic device 100 to the user's auricle 200, the auricle 200 is vibrated by the piezoelectric vibration element 55. The translucent cover substrate 1 is vibrated. The vibration of the auricle 200 is transmitted to the eardrum 220, and the eardrum 220 vibrates. The vibration of the eardrum 220 is transmitted to the ossicle 230, and the ossicle 230 vibrates. The vibration of the ossicles 230 is transmitted to the cochlea 240 and converted into an electric signal in the cochlea 240. This electrical signal is transmitted to the brain through the auditory nerve 250, and the received sound is recognized in the brain. In this way, the conduction sound is transmitted from the translucent cover substrate 1 to the user. FIG. 13 also shows an auricular cartilage 200a inside the auricle 200.

  The conduction sound here is different from the bone conduction sound (also referred to as “bone conduction sound”). Bone conduction sound is sound that is recognized by the human brain by vibrating the skull and directly stimulating the inner ear such as the cochlea. In FIG. 13, for example, when the mandible 300 is vibrated, a sound signal transmission path when a bone conduction sound is recognized by the brain is indicated by a plurality of arcs 420.

  As described above, in the electronic device 100 according to the present embodiment, the piezoelectric vibrating element 55 appropriately vibrates the translucent cover substrate 1 on the front surface, so that the user of the electronic device 100 can transmit the translucent cover substrate 1. Air conduction sound and conduction sound can be communicated to it. In the piezoelectric vibration element 55 according to the present embodiment, the structure is devised so that air conduction sound and conduction sound can be appropriately transmitted to the user. Various merits are generated by configuring the electronic device 100 so that air conduction sound and conduction sound can be transmitted to the user.

  For example, since the user can hear a sound when the translucent cover substrate 1 is applied to the ear, the user can make a call without worrying about the position of the electronic device 100 where the ear is applied.

  In addition, when the ambient noise is large, the user can make the surrounding noise difficult to hear while increasing the volume of the conduction sound by strongly pressing the ear against the translucent cover substrate 1. Therefore, the user can make a call appropriately even when the ambient noise is high.

  Further, even when the user attaches earplugs or earphones to his / her ear, the user can receive a reception sound from the electronic device 100 by placing the translucent cover substrate 1 on his / her ear (more specifically, the auricle). Can be recognized. Further, the user can recognize the received sound from the electronic device 100 by applying the translucent cover substrate 1 to the headphones even when the headphones are attached to the ears.

<About the earpiece hole (receiver hole)>
In an electronic device such as a cellular phone, an earpiece is provided on the front translucent cover substrate 1 in order to extract sound output from a receiver (receiving speaker) provided inside the electronic device to the outside of the electronic device. May be drilled.

In the electronic device 100 according to the present embodiment, since the reception sound is generated by the vibration of the translucent cover substrate 1, the user can appropriately receive the reception sound even if the electronic device 100 has no earpiece hole. Can tell. The translucent cover substrate 1 is a single crystal body mainly composed of alumina (Al ₂ O ₃ ), and is extremely hard as compared with tempered glass or the like. Furthermore, the resistance to various chemicals is very high. When processing such a single crystal having alumina (Al ₂ O ₃ ) as a main component and processing a hole for an earpiece, for example, an expensive manufacturing apparatus such as a laser processing apparatus is required. Or the time required for processing becomes long, and the manufacturing cost may be relatively high. Since the translucent cover substrate 1 of this embodiment does not have a hole for the earpiece, the cost for the hole processing does not occur, and the manufacturing cost of the electronic device 100 is low. Moreover, since the translucent cover substrate 1 does not have a hole for the earpiece, the translucent cover substrate 1 is maintained at a relatively high strength. Further, in the present embodiment, since there is no earpiece hole on the surface of electronic device 100, there is no problem of water or dust entering from the earpiece hole. Therefore, the electronic device 100 does not require a waterproof structure or a dust-proof structure for this problem, and the cost of the electronic device 100 can be further reduced.

  In the above example, the case where the present invention is applied to a mobile phone has been described as an example, but the present invention can also be applied to an electronic device other than a mobile phone. For example, the present invention can be applied to game machines, notebook personal computers, portable navigation systems, and the like.

  In addition, the present invention is not limited to the above-described embodiments, and various improvements and modifications may be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Translucent cover board | substrate 1A One main surface 1B The other main surface 50 Control part 52 Image display device 52a Image display surface 53 Touch panel 55 Piezoelectric vibration element 100 Electronic device

Claims (7)

An electronic apparatus comprising: an image display device having an image display surface in which a plurality of pixels are disposed via inter-pixel regions; and a translucent cover substrate having one main surface disposed to face the image display surface. Because
The translucent cover substrate is made of one single crystal composed mainly of alumina (Al 2 _{O 3),} the one main surface is tilted the relative C-plane of the single crystal (0001),
The refractive index of the translucent cover substrate with respect to ordinary light L ′ having a polarization perpendicular to the c-axis of the single crystal is represented by no,
The refractive index of the translucent cover substrate with respect to extraordinary light L ″ having polarization parallel to the c-axis of the single crystal body is represented by ne,
The inclination angle of the one principal surface with respect to the C plane (0001) of the single crystal is θ,
The thickness of the translucent cover substrate is t,
When the width of the adjacent inter-pixel region on the image display surface is W,
(no ² −ne ² ) tan θ / (no ² tan ² θ + ne ² ) × t <W
An electronic device characterized by satisfying the above relationship .   The electronic apparatus according to claim 1, wherein the one main surface is parallel to an R plane (1-102) of the single crystal body. W / 2 ≦ (no ² −ne ² ) tan θ / (no ² tan ² θ + ne ² ) × t
The electronic device according to claim 1, wherein the relationship is satisfied.   The electronic apparatus according to claim 1, further comprising a piezoelectric vibration element disposed on the translucent cover substrate.   The electronic apparatus according to claim 4, wherein the piezoelectric vibration element vibrates when a driving voltage based on a sound signal is applied thereto.   6. The electronic apparatus according to claim 4, wherein the piezoelectric vibration element has a rectangular and long plate shape in plan view. When viewed in plan the translucent cover substrate, the piezoelectric vibrating element, electronic device according to any of claims 4-6, characterized in that it is disposed in a position that does not overlap the image display device .

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