Display device, lightguide plate, and manufacturing method thereof

According to one embodiment, a display device includes a display panel, a light source, a lightguide, and reflective elements. The lightguide includes a first end facing the light source, a first surface opposed to the display panel, and a second surface. The reflective elements are disposed inside the lightguide, the elements configured to reflect light passing through the first end to spread in the lightguide and to transmit the light through the first surface. Reflective elements are arranged to be apart from the first or second surface with a certain distance and has a reflective surface facing the first surface and projects toward the second surface, the reflective surface is inclined such that the light from the first end can be irradiated to the first surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2015-081014, filed Apr. 10, 2015, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a display device, a lightguide plate, and a manufacturing method thereof.

BACKGROUND

Reflective display devices which display an image by controlling the reflection of external light have advantages such as less power consumption as compared to transmissive display devices including a backlight unit.

Some reflective display devices include a surface emission illumination device in the display surface side of the display panel. The illumination device includes, for example, a light source and a lightguide plate which receives light from the light source and transmits the light through a surface opposed to the display panel. With the illumination device, auxiliary light for image display can be produced and the visibility of image can be increased. The illumination device is often referred to as a frontlight.

The illumination device as above transmits the light spreading in the lightguide plate within a suitable range of angles. Thus, the light can be used more efficiently and the visibility of the display device can be improved.

DETAILED DESCRIPTION

In general, according to one embodiment, a display device includes a display panel, light source, lightguide member, and a plurality of reflective elements. The display panel includes a display area on which an image is displayed. The lightguide member includes a first end which faces the light source, second end which is opposite to the first end, first main surface which is arranged along the first and second ends to be opposed to the display panel, and second main surface which is opposite to the first main surface and arranged along the first and second ends. The reflective elements are disposed inside the lightguide member, and the reflective elements reflect light passing through the first end to spread in the lightguide member, and transmit the light through the first main surface. Furthermore, each of the reflective elements is arranged to be apart from the first main surface or the second main surface with a certain distance in a thickness direction of the lightguide member and has a curved reflective surface which faces the first main surface and projects toward the second main surface, the curved reflective surface is inclined such that the light from the first end can be irradiated to the first main surface.

Furthermore, according to an embodiment, an illumination device includes the above light source, the above lightguide member, and the above reflective elements. Furthermore, according to an embodiment, a lightguide plate includes the above lightguide member, and the above reflective elements.

Furthermore, according to an embodiment, a manufacturing method of a lightguide plate includes forming a plurality of projecting patterns each having a curved surface on a main surface of a base material, forming a plurality of reflective elements at least partly covering the projecting patterns, and forming an overcoat layer formed of a material having a refractive index substantially same as that of the projecting pattern, the overcoat layer formed on the main surface of the base material to cover the reflective elements.

Embodiments will be described with reference to the accompanying drawings.

Note that the embodiments described hereinafter are merely examples, and any other embodiments which are conceivable by a person having ordinary skill in the art without departing from the substantial concept of the invention are encompassed in the scope of the invention of the present application. Furthermore, the drawings are presented such that a dimension and a shape of each component are drawn more schematically as compared to the actual model for the sake of clear explanation. However, such depiction is merely an example and interpretation of the present invention is not limited thereby. In each figure, if elements are arranged continuously, the reference number of those which are the same as or similar to the one already depicted will be omitted. Furthermore, in the description and the figures, structural elements which function the same as or similarly to the one already described or depicted in the preceding will be referred to by the same reference numbers and descriptions considered redundant will be omitted.

In the first embodiment, an example of an illumination device and a lightguide plate will be explained. The illumination device may be used as a frontlight of a display device such as a liquid crystal display device, micro-electro mechanical systems (MEMS) applied display device, and electronic paper display device using electrophoresis or the like.

FIG. 1is a perspective view which shows a schematic structure of an illumination device LD of the present embodiment. The illumination device LD includes a lightguide plate LG and a light source LS. The lightguide plate LG includes a plate-like lightguide member1having a predetermined thickness and a plurality of reflective elements2(first reflective elements) disposed inside the lightguide member1.

The lightguide member1includes a first end E1, second end E2which is opposite to the first end E1, first main surface F1reaching the first end E1and the second end E2, and second main surface F2reaching the first end E1and the second end E2at the opposite side of the first main surface F1. The first end E1and the second end E2are parallel with a first direction X, and correspond to side surfaces connecting the first main surface F1and the second main surface F2.

In the example ofFIG. 1, the first main surface F1and the second main surface F2of the lightguide member1have a rectangular shape. The first end E1and the second end E2are side surfaces connecting the corresponding short sides of the first main surface F1and the second main surface F2. The long sides of the first main surface F1and the second main surface F2extend along the second direction Y which is orthogonal to the first direction X. The thickness direction of the lightguide member1is defined as the third direction Z. The third direction Z crosses the first direction X and the second direction Y, and for example, the third direction Z is orthogonal to the first direction X and the second direction Y. Each of the first main surface F1and the second main surface F2is parallel with an XY plane which is defined by the first direction X and the second direction Y. The shape of the lightguide member1is not limited to the above described shape, and the first end E1and the second end E2may connect the long sides of the rectangular first main surface F1and second main surface F2, or the first main surface F1and the second main surface F2may have a square shape or other shapes.

The thickness of the lightguide member1may be less than that of the light source LS. In that case, the lightguide member1may include a main lightguide which is formed thinner than the light source LS in the third direction Z and a light receiver disposed between the main lightguide and the light source LS. For example, in the main lightguide, the first main surface F1and the second main surface F2are parallel. The main lightguide and the light receiver may be integrally formed using the same material, or may be formed separately and then connected together. The side surface of the light receiver which opposed to the light source LS corresponds to the first end E1. The thickness of the light receiver in the third direction Z increases from the main lightguide to the first end E1. For example, the reflective elements2are disposed on the main lightguide but not on the light receiver. Since the first end E1has wide width in the third direction Z, light from the light source LS suitably enters the light receiver. Furthermore, with the lightguide member1structured as above, the main lightguide can be formed thin.

The light source LS faces the first end E1. The light source LS may be a luminescent diode or an organic electroluminescence device. In the example ofFIG. 1, three or more light sources LS are arranged along the first end E1; however, the number thereof may be two or one. The light source LS may be linear to be arranged along the first end E1.

FIG. 2is a schematic cross-sectional view of the illumination device LD in the Y-Z plane defined by the second direction Y and the third direction Z. The lightguide member1includes a transparent base material10having a first main surface10aand a second main surface10bwhich is opposite to the first main surface10aand an overcoat layer11which is provided with the second main surface10bof the transparent base material10. The transparent base material10and the overcoat layer11both possess high light transmissivity. The transparent base material10may be formed of glass or a resin material, for example. The overcoat layer11may be formed of a resin material, for example. The lightguide member1may include an additional layer other than the transparent base material10and the overcoat layer11.FIG. 2schematically shows the thickness of the transparent base material10and the overcoat layer11, and the transparent base material10may be made thicker in the actual use. As an example, the transparent base material10may have a thickness of 0.5 mm and the overcoat layer11may have a thickness of several to a few tens of micrometers.

In the example ofFIG. 2, the first end E1and second end E2include ends of the transparent base material10and the overcoat layer11. Furthermore, the first main surface F1of the lightguide member1corresponds to the first main surface10aof the transparent base material10and the second main surface F2of the lightguide member1corresponds to the outer surface of the overcoat layer11(the surface of the overcoat layer11which does not contact the transparent base material10).

The reflective elements2are, for example, each formed in the same shape and arranged inside the overcoat layer11along with the second main surface10bof the transparent base material10. In the present embodiment, each reflective element2is formed in a curved half dome-like shape projecting toward the second main surface F2, in other words, a curved and a partly removed bowl-like shape projecting toward the second main surface F2(a half of the bowl at the first end E1side is removed in this example). Each reflective element2includes a high-reflectivity layer20which suitably reflects light spreading in the lightguide member1and a low-reflectivity layer21(or light shielding layer) the reflectivity of which is lower than that of the high-reflectivity layer20. The high-reflectivity layer20may be formed of a metal material such as aluminum or silver. The low-reflectivity layer21may be formed of a metal material or a metal oxide film of which reflectivity is relatively low.

The high-reflectivity layer20covers a part of a projecting pattern PT1arranged on the second main surface10bof the transparent base material10.

Projecting pattern PT1is, for example, half spherical or partial spherical. Note that, in each embodiment, the term half spherical and the term partial spherical mean not only a part of a sphere but also a part of a sphere-like shape such as an ellipse. The low-reflectivity layer21covers the surface of the high-reflectivity layer20in the second main surface F2side. The overcoat layer11covers the reflective elements2, projecting patterns PT1uncovered by the reflective elements2, and the second main surface10bof the transparent base material10. Projecting pattern PT1and the overcoat layer11can be formed such that their refractive indices become substantially the same, that is, they may be formed of the same material. Thus, in the boundary between each projecting pattern PT1and the overcoat layer11, light going from projecting pattern PT1to the overcoat layer11and light going oppositely hardly make refraction or reflection. Thus, no adversely optical effect occurs. The light linearity is maintained regardless of the boundary between projecting pattern PT1and the overcoat layer11. If projecting pattern PT1and the overcoat layer11are formed of the same material, they are substantially integral and the boundary therebetween is almost invisible.

In the example ofFIG. 2, the transparent base material10and the overcoat layer11have a substantially same thickness from the first end E1to the second end E2. Therefore, each reflective element2is arranged to be apart from the first main surface F1and the second main surface F2with a certain distance in the thickness direction of the lightguide member1(in third direction Z).

A light emitter EP of the light source LS faces the first end E1(an end of the transparent base material10). InFIG. 2, an example of a passage of the light from the light emitter EP is depicted by dotted lines. The light from the light emitter EP enters the lightguide member1through the first end E1spreads toward the second end E2while being totally reflected by the first main surface F1and the second main surface F2. However, part of the light is loosed from the total reflection by the first main surface F1when being reflected by the high-reflectivity layer20(reflective surface20awhich will be described later) of the reflective element2, and passes outside through the first main surface F1.

InFIG. 3, an example of the shape of the reflective element2is schematically shown.FIG. 3(a)shows the reflective element2and projecting pattern PT1in an X-Y plan view.FIG. 3(b)shows the structure including reflective element2, projecting pattern PT1, and the like in a cross-sectional view of the Y-Z plane. As inFIGS. 3(a) and 3(b), the reflective element2covers the half of the surface of projecting pattern PT1in the second end E2side (the left half of the figure), that is, the other half of the surface of projecting pattern PT1in the first end E1(the right half of the figure) is uncovered. In this state, the barycenter C1of the reflective element2and the barycenter C2of projecting pattern PT1are shifted in the X-Y plane. The barycenter C1is more distant from the light source LS than is the barycenter C2(is farther left than the barycenter C2in the figure).

From a different standpoint, the reflective element2is, in a three-dimensional view, shaped to be asymmetrical with respect to an axis parallel to the normal of the first main surface F1or the second main surface F2(the third direction Z). For example, the shape of the reflective element2is rotationally asymmetrical with respect to the axis extending in the third direction Z passing through the barycenter C1or C2.

The surface of the high-reflectivity layer20in the first main surface F1side is a reflective surface20aalong the surface of projecting pattern PT1. The reflective surface20afaces the first main surface F1side and the light source LS side (the right side of the figure), and projects curving toward the second main surface F2. The reflective element2is thus arranged such that the reflective surface20ais inclined to irradiate the light from the first end E1to the first main surface F1. In the present embodiment, the center of curvature C3of the reflective surface20ais at a position closer to the first main surface F1than is the center of the reflective surface20ain the third direction Z. In the example ofFIG. 3(b), the reflective surface20ais a surface of the radius of curvature R of which center is a single center of curvature C3; however, if there are centers of curvature of the reflective surface20avarying at different positions, the reflective surface20ais arranged such that most or all centers of curvatures can be positioned to be closer to the first main surface F1than are the corresponding parts of the reflective surface20a.

The reflective element2having the reflective surface20aformed as above can control the angle of the light reflected by the reflective surface20aand passing outside through the first main surface F1to be within a specific range. That is, the angle of light passing outside through the first main surface F1can be set within a range narrower compared to a case where the reflective surface20ais flat and a case where the reflective surface20ais curved but positioned such that its center of curvature C3is set closer to the second main surface F2.

Furthermore, since the barycenter C1of the reflective element2and the barycenter C2of projecting pattern PT1are shifted on the X-Y plane, the reflective element2can apply anisotropy to the angle of light passing outside through the first main surface F1. For example, in the example ofFIGS. 2and3, the reflective element2can control the angle of light passing outside through the first main surface F1to be inclined to the first end E1side.

An example of a manufacturing method of a lightguide plate LG will be explained with reference toFIGS. 4 to 6. In each figure, item (a) is a partial perspective view of the lightguide plate LG during the manufacturing process, and item (b) is a partial cross-sectional view of the lightguide plate LG in the Y-Z plane.

Initially, as inFIGS. 4(a) and 4(b), a plurality of projecting patterns PT1are formed on the second main surface10bof the transparent base material10. Projecting patterns PT1are formed through, for example, a photolithography process. Here, projecting patterns PT1after development may be heated such that they are at least partially melted to round the corners. Projecting patterns PT1can be finished to have a spherical surface as shown inFIG. 4(b). Note that the formation process of projecting patterns PT1is not limited to the photolithography process, and may be an inkjet printing process or the like. Projecting patterns PT1may be arranged regularly or randomly.

Then, as inFIGS. 5(a) and 5(b), a plurality of reflective elements2which at least partially cover projecting patterns PT1are prepared. In this process, for example, the high-reflectivity layer20and the low-reflectivity layer21are formed in this order on the second main surface10bof the transparent base material10with projecting patterns PT1formed thereon. Here, the high-reflectivity layer20and the low-reflectivity layer21are formed through an evaporation or sputtering process, and then patterned by etching to form the reflective elements2shown inFIGS. 5(a) and 5(b). Then, as inFIGS. 6(a) and 6(b), the overcoat layer11is formed on the second main surface10bof the transparent base material10to cover the reflective elements2and projecting patterns PT1. The lightguide plate LG is manufactured as above.

Then, an example of the shape of the reflective surface20aof the high-reflectivity layer20will be explained. In a cross-sectional view of the lightguide member1taken along the direction from the first end E1to the second end E2(cross-section along the Y-Z plane), the reflective surface20ais formed such that an angle formed by the reflective surface20aand the first main surface F1or an imaginary surface parallel with the first main surface F1can be set within a certain distribution of angle of inclination. If the illumination device LD is used as a frontlight of a reflective display device of a device such as a smartphone or a tablet as in the fifth embodiment which is described later, the distribution of angle of inclination is set such that the peak of the angle falls between 10 and 50°, preferably between 30 and 45°, and more preferably between 37 and 43° to improve the visibility of the display image.

The distribution of angle of inclination and measurement methode of the angle peak of the reflective surface20awill be described with reference toFIGS. 7 and 8. In the measurement process, a profile of the reflective surface20ais initially measured.FIG. 7schematically shows a profile PF of the reflective surface20ain the Y-Z plane. The profile PF corresponds to the shape of the reflective surface20ain the Y-Z plane passing the barycenter of the reflective element2, for example.

To measure the distribution of angle of inclination, the profile PF is divided into a plurality of areas at regular intervals in the third direction Z. In the example ofFIG. 7, the profile PF is divided into six areas A0to A5using lines L0to L5arranged along the third direction Z at regular intervals.

Angles θ0to θ5of the profile PF in respective areas A0to A5are measured to obtain the distribution of angle of inclination. For example, inclination of the profile PF between the first main surface F1(the lower side of the figure) and a contact point with line L0with respect to the axis Y is angle θ0.

Furthermore, inclination of the profile PF between the contact point with line L0and a contact point with line L1with respect to the axis Y is angle θ1. Angles θ2to θ5can be measured in the same manner.

Note that the profile PF is divided into six areas of A0to A5inFIG. 7for the sake of simplification; however, ten or more areas should be provided in the actual measurement of angles. The graph ofFIG. 8shows an example of distribution of angle of inclination measured as above. In this graph, the horizontal axis shows angle (degree) and the vertical axis shows distribution ratio (%). The distribution of angle of inclination is depicted by bars where a unit of a bar is five degrees. The distribution ratio is percentage of the length corresponding to the angles of the horizontal axis of the entire length of the profile PF. The angle of each divided area is assumed to be constant in each area. In the distribution of angle of inclination ofFIG. 8, angles are focused around 40 degrees. The graph shows than the above-mentioned angle range between 37 and 43° is satisfied.

Now, an example of the arrangement of reflective elements2of the lightguide member1will be explained.

FIG. 9shows an example of the arrangement of the reflective elements2in which the arrangement of the reflective elements2in the lightguide member1in the X-Y plane is the upper figure and a cross-sectional view thereof in the Y-Z plane is the lower figure. The reflective elements2are arranged in the X-Y plane in such a manner that the density thereof increases from the first end E1to the second end E2. In other words, the number of the reflective elements2per unit area increases from the first end E1to the second end E2. Furthermore, in the example ofFIG. 9, the lightguide plate LG includes a plurality of dummy reflective elements3(second reflective elements) inside the lightguide member1. The dummy reflective elements3are arranged in the X-Y plane in such a manner that the density thereof decreases from the first end E1to the second end E2. In other words, the number of the dummy reflective elements3per unit area decreases from the first end E1to the second end E2. For example, the density of the reflective elements2and the dummy reflective elements3on the X-Y plane is substantially uniform.

The dummy reflective element3includes, as in the reflective element2, a high-reflectivity layer30arranged in the first main surface F1side and a low-reflectivity layer31covering the high-reflectivity layer30. The reflective elements3are formed directly on the second main surface10bof the transparent base material10without projecting patterns PT1interposed therebetween. Therefore, a reflective surface30aof the high-reflectivity layer30faces the first main surface F1and is substantially flat. The dummy reflective elements3can be formed through the same manufacturing process as that of the reflective elements2. The outer shape of the dummy reflective element3is the same as that of the reflective element2in the plan view with respect to the third direction Z. Light from the light source LS enters the first end E1and part of the light is totally internally reflected on reaching the reflective surface30aof the dummy reflective element3. Since the reflective surface30ais flat, the reflected light cannot acquire an angle that allows it to pass through the first main surface F1and is totally internally reflected thereat. On the other hand, the light reaching the reflective surface20aof the reflective element2acquires an angle that does not produce total internal reflection at the first main surface F1since the reflective surface20ais curve, and passes through the first main surface F1.

In the illumination device LD of the present embodiment explained as above, the lightguide plate LG includes a plurality of reflective elements2each of which faces the first main surface F1and includes a curved reflective surface20having the center of curvature in the first main surface F1side. Thus, the light spreading in the lightguide member1can pass through the first main surface F1within a specific angle range.

Furthermore, the reflective element2includes a low-reflectivity layer21covering the high-reflectivity layer20. Thus, the reflection of light incoming from the second main surface F2side by the high-reflectivity layer20can be prevented. By preventing such reflection, glaring in display when viewing the lightguide plate LG from the second main surface F2side can be suppressed. For example, if the illumination device LD is used as a frontlight of a display device as explained later in the fifth embodiment, the visibility of the image on the display device will be improved by such glaring suppression.

Furthermore, since the barycenter C1of the reflective element2and the barycenter C2of projecting pattern PT1are shifted in the X-Y plane, the reflective element2can apply anisotropy to the angle of light passing outside through the first main surface F1. Specifically, as shown inFIG. 3, the barycenter C1is positioned to be more distant from the light source LS than is the baricenter C2. In this case, the light from the light source LS is reflected by the reflective element2and mostly passes outside through the first main surface F1inclining toward the light source LS side as passages depicted in dotted lines inFIG. 2. That is, in the present embodiment, the light passing through the first main surface F1can possess the anisotropy mostly inclining to the light source LS side. The illumination device LD as above can be used in various uses where emission light needs to possess anisotropy.

The intensity of the light from the light source LS decreasing toward the second end E2. However, since the density of the reflective elements2are increased toward the second end E2, the luminosity of the light passing outside through the first main surface F1can be uniformed.

Furthermore, with the dummy reflective elements3arranged as above, the luminosity of the light passing through the lightguide plate LG from the first main surface F1to the second main surface F2can be substantially uniformed in the X-Y plane. The function of the dummy reflective elements3is effective in a case where the illumination device LD is used as a frontlight of the display device as explained later in the fifth embodiment.

Furthermore, through the manufacturing method of the lightguide plate LG of the present embodiment, the lightguide plate LG including the reflective elements2inside thereof and the illumination device LD including the lightguide plate LG can easily be manufactured.

Along with the above advantages, various other advantages can be achieved by the present embodiment.

Now, the second embodiment will be explained. In the present embodiment, another structure applicable to a lightguide plate and an illumination device will be explained. The following explanation will be focused on technical differences from the first embodiment, and the same or similar elements as in the first embodiment will be referred to by the same reference numbers and description considered redundant will be omitted.

FIG. 10shows an illumination device LD of the present embodiment and is a schematic cross-sectional view of the illumination device LD in the Y-Z plane. The illumination device LD in the figure includes a lightguide plate LG which includes, as in the first embodiment, a lightguide member1including a transparent base material10and an overcoat layer11, and reflective elements2. The overcoat layer11includes a first overcoat layer11aand a second overcoat layer11b. The structure of the reflective element2is similar to that of the first embodiment.

The first overcoat layer11ais formed on the second main surface10bof the transparent base material10. The first overcoat layer11aincludes a plurality of concave patterns PT2. The concave pattern PT2is half spherical or partial spherical. Along the inner surface of the concave pattern PT2, the reflective elements2are disposed inside the overcoat layer11. Similarly to the relationship between the reflective elements2and projecting pattern PT1of the first embodiment, the barycenter of the reflective element2and the barycenter of the concave pattern PT2are shifted in the X-Y plane. The barycenter of the reflective element2is more distant from the light source LS than is the concave pattern PT2(to be farther left of the figure).

The second overcoat layer11bcovers the reflective elements2, concave patterns PT2uncovered by the reflective elements2, and first overcoat layer11a. The second overcoat layer11bfills in each concave pattern PT2. The first overcoat layer11aand the second overcoat layer11bcan be formed such that their refractive indices become substantially the same, that is, they may be formed of the same material.

Thus, in the boundary between the first overcoat layer11aand the second overcoat layer11b, light going from the first overcoat layer11ato the second overcoat layer11band light going oppositely hardly make refraction or reflection. Thus, no adversely optical effect occurs. If the first overcoat layer11aand the second overcoat layer11bare formed of the same material, they are substantially integral and the boundary therebetween is almost invisible.

In the example ofFIG. 10, the first main surface F1of the lightguide member1corresponds to the outer surface of the second overcoat layer11b(the surface not contacting the first overcoat layer11a), and the second main surface F2of the lightguide member1corresponds to the first main surface10aof the transparent base material10.

As depicted by dotted lines inFIG. 10, light from a light emitter EP of the light source LS enters the lightguide member1through the first end E1and spreads toward the second end E2therein while being totally internally reflected at the first main surface F1and the second main surface F2. Part of the light is reflected by the high-reflectivity layer20of the reflective element2(reflective surface20a) and reaches the first main surface F1. There, the light acquires an angle that does not produce total internal reflection, and passes through the first main surface F1.

An example of a manufacturing method of the lightguide plate LG of the present embodiment will be explained with reference toFIGS. 11 to 13. In each figure, item (a) is a partial perspective view of the lightguide plate LG during the manufacturing process, and item (b) is a partial cross-sectional view of the lightguide plate LG in the Y-Z plane.

Initially, as inFIGS. 11(a) and 11(b), a first overcoat layer11ais formed on a second main surface10bof a transparent base material10, and a plurality of concave patterns PT2are formed on the first overcoat layer11a. The concave patterns PT2may be formed by mechanically hollowing the first overcoat layer11a, for example. Alternatively, the concave patterns PT2may be formed by preparing a photosensitive resin material resist as the first overcoat layer11aand removing parts corresponding to the concave patterns PT2from the resist by a photolithography process. Here, the concave patterns PT2after development may be heated such that they are at least partially melted to round the corners. The concave patterns PT2can be finished to have a spherical surface as shown inFIG. 11(b). The concave patterns PT2may be arranged regularly or randomly.

Then, as inFIGS. 12(a) and 12(b), a plurality of reflective elements2which at least partially cover the concave patterns PT2are formed. In this process, for example, a high-reflectivity layer20and a low-reflectivity layer21are formed in this order on the first main surface11awith the concave patterns PT2formed thereon. Here, the high-reflectivity layer20and the low-reflectivity layer21are formed through an evaporation or sputtering process, and then patterned by etching to form the reflective elements2shown inFIGS. 12(a) and 12(b).

Then, as inFIGS. 13(a) and 13(b), the second overcoat layer11bis formed on the first overcoat layer11ato cover the reflective elements2and the concave patterns PT2. The lightguide plate LG is manufactured as above.

The same advantages as in the first embodiment can be achieved by the lightguide plate LG of the present embodiment.

Now, the third embodiment will be explained. In the present embodiment, another structure applicable to a lightguide plate and an illumination device will be explained. The following explanation will be focused on technical differences from the first embodiment, and the same or similar elements as in the first embodiment will be referred to by the same reference numbers and description considered redundant will be omitted.

FIG. 14shows an illumination device LD of the present embodiment and is a schematic cross-sectional view of the illumination device LD in the Y-Z plane. The illumination device LD in the figure includes a lightguide plate LG which includes, as in the first embodiment, a lightguide member1including a transparent base material10and an overcoat layer11, and reflective elements2. The structure of the reflective element2is similar to that of the first embodiment.

The transparent base material10includes a plurality of concave patterns PT3on the second main surface10b. The concave pattern PT3is half spherical or partial spherical. Along the inner surface of the concave pattern PT3, the reflective elements2are disposed. Similarly to the relationship between the reflective elements2and projecting pattern PT1of the first embodiment, the barycenter of the reflective element2and the barycenter of the concave pattern PT3are shifted in the X-Y plane. The barycenter of the reflective element2is more distant from the light source LS than is the concave pattern PT3(to be farther left of the figure).

The overcoat layer11covers the reflective elements2, concave patterns PT3uncovered by the reflective elements2, and second main surface10bof the transparent base material10. The overcoat layer11fills in each concave pattern PT3.

In the example ofFIG. 14, the first main surface F1of the lightguide member1corresponds to the outer surface of the overcoat layer11(the surface not contacting the transparent base material10), and the second main surface F2of the lightguide member1corresponds to the first main surface10aof the transparent base material10.

As depicted by dotted lines inFIG. 14, light from a light emitter EP of the light source LS enters the lightguide member1through the first end E1and spreads toward the second end E2therein while being totally internally reflected at the first main surface F1and the second main surface F2. Part of the light is reflected by the high-reflectivity layer20of the reflective element2(reflective surface20a) and reaches the first main surface F1. There, the light acquires an angle that does not produce total internal reflection, and passes through the first main surface F1.

An example of a manufacturing method of the lightguide plate LG of the present embodiment will be explained with reference toFIGS. 15 to 17. In each figure, item (a) is a partial perspective view of the lightguide plate LG during the manufacturing process, and item (b) is a partial cross-sectional view of the lightguide plate LG in the Y-Z plane.

Initially, as inFIGS. 15(a) and 15(b), a plurality of concave patterns PT3are formed on the second main surface10bof the transparent base material10. The concave patterns PT3may be formed by mechanically hollowing the transparent base material10, for example. Alternatively, the concave patterns PT3may be formed by masking the second main surface10bof the transparent base material10excluding the parts to be the concave patterns PT3and eroding the second main surface10bwith, for example, a hydrofluoric acid solution. The concave patterns PT3may be arranged regularly or randomly.

Then, as inFIGS. 16(a) and 16(b), a plurality of reflective elements2which at least partially cover the concave patterns PT3are formed. In this process, for example, a high-reflectivity layer20and a low-reflectivity layer21are formed in this order on the second main surface10bof the transparent base material10with the concave patterns PT3formed thereon. Here, the high-reflectivity layer20and the low-reflectivity layer21are formed through an evaporation or sputtering process, and then patterned by etching to form the reflective elements2shown inFIGS. 16(a) and 16(b).

Then, as inFIGS. 17(a) and 17(b), the overcoat layer11is formed on the second main surface10bof the transparent base material10to cover the reflective elements2, the concave patterns PT3and the second main surface10b. The lightguide plate LG is manufactured as above.

The same advantages as in the first embodiment can be achieved by the lightguide plate LG of the present embodiment.

Now, the fourth embodiment will be explained. In the present embodiment, another structure applicable to a lightguide plate and an illumination device will be explained. The following explanation will be focused on technical differences from the first embodiment, and the same or similar elements as in the first embodiment will be referred to by the same reference numbers and description considered redundant will be omitted.

In the proximity of the light source LS, light enters the lightguide member1through the first end E1partially fails to satisfy the requirement for total internal reflection, and passes outside through the second main surface F2. In this embodiment, a structure to reduce such light leakage will be presented.

FIG. 18shows an illumination device LD of the present embodiment and is a schematic cross-sectional view of the illumination device LD in the Y-Z plane. The illumination device LD in the figure includes a lightguide plate LG which includes, as in the first embodiment, a lightguide member1including a transparent base material10and an overcoat layer11, and reflective elements2. The structure of the transparent base material10, overcoat layer11, and reflective element2is similar to that of the first embodiment.

The lightguide member1further includes a low refractive index layer12covering the outer surface of the overcoat layer11(the surface not contacting the transparent base material10). The low refractive index layer12is formed of, for example, a resin material of which refractive index is lower than that of the overcoat layer11.

The lightguide plate LG further includes an auxiliary reflective element4(third reflective element) disposed inside the lightguide member1in the proximity of the light source LS. The auxiliary reflective element4is, for example, disposed to be closer to the first end E1than is each reflective element2and extends in the first direction X along the first end E1. The auxiliary reflective element4may extend continuously from one end to the other end of the lightguide member1in the first direction X, or a plurality of auxiliary reflective elements4may be arranged separately between the ends in the first direction X.

The auxiliary reflective element4includes a high-reflectivity layer40which suitably reflects the light spreading in the lightguide member1and a low-reflectivity layer41(or light shielding layer) of which reflectivity is lower than that of the high-reflectivity layer40. The high-reflectivity layer40may be formed of a metal material such as aluminum or silver. The low-reflectivity layer41may be formed of a metal material or a metal oxide film of which reflectivity is relatively low.

The high-reflectivity layer40covers a part of a projecting pattern PT4arranged on the second main surface10bof the transparent base material10. The low-reflectivity layer41coves the surface of the high-reflectivity layer40in the second main surface F2side. Projecting pattern PT4includes a plurality of projections extending in the first direction X and arranged in the second direction Y. The cross-sectional shape of the surface of each projection is an arc of which curvature is generally lower than that of the surface of projecting pattern PT4. The surface of the high-reflectivity layer40in the first main surface F1side is a reflective surface40aof which shape is the same as that of the surface of projecting pattern PT4. The reflective surface40ahas a curvature which is generally lower than that of the reflective surface20aof the reflective element2in the cross-section taken along the direction from the first end E1to the second end E2(cross-section in the Y-Z plane).

The overcoat layer11covers the reflective elements2, projecting patterns PT1uncovered by the reflective elements2, the auxiliary reflective elements4, projecting patterns PT4uncovered by the auxiliary reflective elements4, and the second main surface10bof the transparent base material10. Projecting pattern PT1, projecting pattern PT4, and overcoat layer11can be formed such that their refractive indices become substantially the same, that is, they may be formed of the same material. Thus, in the boundary between each projecting pattern PT1or projecting pattern PT4and the overcoat layer11, light going from projecting pattern PT1or projecting pattern PT4to the overcoat layer11and light going oppositely hardly make refraction or reflection. Thus, no adversely optical effect occurs. If projecting pattern PT1, projecting pattern PT4, and overcoat layer11are formed of the same material, they are substantially integral and the boundary therebetween is almost invisible.

In the example ofFIG. 18, the first main surface F1of the lightguide member1corresponds to the first main surface10aof the transparent base material10, and the second main surface F2of the lightguide member1corresponds to the outer surface of the low-reflective-index layer12(the surface not contacting the overcoat layer11).

As depicted by dotted lines inFIG. 18, light from a light emitter EP of the light source LS enters the lightguide member1through the first end E1and partly spreads toward the second end E2therein while being reflected by the high-reflectivity layer40(reflective surface40a) of the auxiliary reflective element4. Without the auxiliary reflective element4, the light may possibly pass outside through the second main surface F2avoiding total internal reflection at the second main surface F2. Since the curvature of the reflective surface40ais set suitably large, the light reflected by the reflective surface40adoes not easily acquire an angle that does not produce total internal reflection at the first main surface F1. The light spreading toward the second end E2is partly reflected at the boundary between the overcoat layer11and the low-reflective-index layer12. If the light enters the low-reflective-index layer12, it goes to the second main surface F2at a relatively shallow angle by the refraction at the above boundary. Thus, such light is easily totally internally reflected at the second main surface F2. The light reflected by the high-reflectivity layer20(reflective surface20a) of the reflective element2partly acquires an angle that does not produce total internal reflection at the first main surface F1and passes outside through the first main surface F1.

An example of a manufacturing method of a lightguide plate LG will be explained with reference toFIGS. 19 to 22. In each figure, a partial cross-sectional view of the lightguide plate LG corresponding to each manufacturing process is shown.

Initially, as shown inFIG. 19, a photosensitive resin material resist R is formed on a second main surface10bof a transparent base material10. Then, as shown inFIG. 20, the resist R is exposed by ultraviolet (UV) using a halftone mask M. The halftone mask M includes first parts P1which pass substantially all of ultraviolet ray, second parts P2which shield substantially all of ultraviolet ray, and third parts P3which partly pass ultraviolet ray. The first parts P1are, for example, arranged to avoid the positions of projecting patterns PT1and PT4. The second parts P2are, for example, arranged to correspond to the positions of projecting patterns PT1and the position of each of the projections of projecting patterns PT4. The third parts PT3are, for example, arranged to put second parts P2therebetween, which correspond to each of the projections of projecting patterns PT4.

When the unnecessary part is removed by development of the exposed resist R, an isolation pattern PT1awhich is a base of projecting pattern PT1and a continuous pattern PT4awhich is a base of projecting pattern PT4are formed as shown inFIG. 21. The continuous pattern PT4ais formed in a concave/convex shape in which the part of the halftone mask M corresponding to the third parts PT3is thinner than the part thereof corresponding to the second parts P2.

As shown inFIG. 21, heat from a heat source HS is applied to the patterns PT1aand PT4afor burning thereof. By burning, the patterns PT1aand PT4aare melt to round their corners, and as shown inFIG. 22, the isolation pattern PT1abecomes projecting pattern PT1which is half spherical or partial spherical, and the continuous pattern PT4abecomes projecting pattern PT4having a plurality of curved projections extending in the first direction X. Since the wettability of the transparent base material10is kept appropriately, deformation by stress becomes different between the patterns PT1aand PT4a, and furthermore, the thickness of the continuous pattern PT4achanges alternately in the thin and thick parts. Therefore, the curvature of projecting pattern PT1increases and the curvature of each projection of projecting pattern PT4decreases.

Then, a high-reflectivity layer20and a low-reflectivity layer21are disposed on projecting pattern PT1to form a reflective element2, and a high-reflectivity layer40and a low-reflectivity layer41are disposed on projecting pattern PT4to form an auxiliary reflective element4. The high-reflectivity layers20and40can be formed of the same material at the same time, and the low-reflectivity layers21and41are formed of the same material at the same time.

Furthermore, an overcoat layer is formed to cover the reflective elements2, auxiliary reflective element4, projecting pattern PT1uncovered by the reflective element2, projecting pattern PT4uncovered by the auxiliary reflective element4, and second main surface10bof the transparent base material10, and then, a low refractive index layer12is formed on the overcoat layer11. Through the above process, the lightguide plate LG is obtained.

The lightguide plate LG disclosed in the present embodiment can achieve the same advantages obtained form the first embodiment. Furthermore, with the auxiliary reflective element4, light leakage from the second main surface F2of the lightguide member1in the proximity of the light source LS can be reduced.

Now, the fifth embodiment will be explained. In the present embodiment, a reflective liquid crystal display device will be explained as an example of a display device including an illumination device which functions as a frontlight. The liquid crystal display device can be used in various devices such as a smartphone, tablet, mobile phone, personal computer, television receiver, in-car device, and gaming device. Note that the display device is not limited to a liquid crystal display device, and may be other display devices including a MEMS display device and an electronic paper display device.

FIG. 23is a schematic perspective view which shows a display device DSP of the present embodiment. The display device DSP include a display panel PNL and an illumination device LD. The illumination device LD includes a lightguide plate LG and a light source LS, and is applicable to the illumination devices LD of the first to fourth embodiments.

The display panel PNL includes an array substrate AR and a countersubstrate CT. In the example ofFIG. 23, both the array substrate AR and the countersubstrate CT are formed in a plate-like rectangular having short sides along the first direction X and long sides along the second direction Y. The array substrate AR and the countersubstrate CT are attached such that one short side and two long sides of each substrate match one another. The size of the array substrate AR is larger than that of the countersubstrate CT in the second direction Y, and the array substrate AR includes an interconnection area LA exposed from the countersubstrate CT. For example, interconnections and terminals used for external connection are provided with the interconnection area LA. The display panel PNL includes a display area DA on which an image is displayed.

The illumination device LD is arranged such that a first main surface F1faces the countersubstrate CT and a first end E1and a light source LS of the lightguide member1are disposed in the interconnection area LA side. For example, the light source LS and the interconnection area LA overlap in the X-Y plane. For example, the first main surface F1overlaps the entirety of the display area DA in the X-Y plane.

As depicted by dotted lines in the figure, light from the light source LS spreads in the lightguide member1and partly passes outside from the first main surface F1as being reflected by the reflective elements2, and then, enters the display panel PNL. Using this light the display panel PNL displays an image on the display area DA. The display panel PNL may display an image by using external light passing in the lightguide member1from the second main surface F2to the first main surface F1in addition to the above light or may display an image using such external light alone.

FIG. 24is a schematic cross-sectional view of the display device DSP in the Y-Z plane. Here, a case where one main pixel PX includes subpixels PR, PG, and PB will be explained. The display device DSP includes an array substrate AR, countersubstrate CT, liquid crystal layer LC, and optical element OD.

The array substrate AR includes, for example, a first insulating substrate100, switching elements SW1, SW2, and SW3, interlayer insulating film101, pixels electrodes (reflective electrodes) PE1, PE2, and PE3, and first alignment film102. The switching elements SW1to SW3are formed on the first insulating substrate100to be opposed to the countersubstrate CT. The switching element SW1is disposed within the subpixel PR, the switching element SW2is disposed within the subpixel PG, and the switching element SW3is disposed within the subpixel PB. The interlayer insulating film101covers the switching elements SW1to SW3and first insulating substrate100. The pixel electrodes PE1to PE3are formed on the interlayer insulating film101to be opposed to the countersubstrate CT. The pixel electrodes PE1to PE3each include a reflective layer formed of a light reflective metal material such as aluminum and silver. The pixel electrodes PE1to PE3or the reflective layers have a substantially flat surface (specular surface). The pixel electrode PE1is disposed in the subpixel PR and is electrically connected to the switching element SW1. The pixel electrode PE2is disposed in the subpixel PG and is electrically connected to the switching element SW2. The pixel electrode PE3is disposed in the subpixel PB and is electrically connected to the switching element SW3. The first alignment film102covers the pixel electrodes PE1to PE3and interlayer insulating film101.

The countersubstrate CT includes, for example, a second insulating substrate200, light shielding layer BM, color filters CFR, CFG, and CFB, overcoat layer201, common electrode CE, and second alignment film202. The light shielding layer BM is formed on the second insulating substrate200to be opposed to the array substrate AR. The color filters CFR, CFG, and CFB are formed on the second insulating substrate to be opposed to the array substrate AR, and partly overlap the light shielding layer BM. The color filter CFR is a red color filter disposed in the subpixel PR and opposed to the pixel electrode PE1. The color filter CFG is a green color filter disposed in the subpixel PG and opposed to the pixel electrode PE2. The color filter CFB is a blue color filter disposed in the subpixel PB and opposed to the pixel electrode PE3. Note that, if the main pixel PX includes an additional subpixel of a different color, a color filter corresponding to the different color is disposed in the additional subpixel. As such a color filter different from red, green, and blue, a color filter of yellow, pale blue, or pale red may be adopted, or a substantially transparent or white color filter may be adopted. The color filters CF are arranged to correspond to the subpixels of their respective colors. The overcoat layer201covers the color filters CF.

The common electrode CE is formed on the overcoat layer201to be opposed to the array substrate AR. The common electrode CE is, for example, formed on the entirety of the main pixel PX to be opposed to the pixel electrodes PE1to PE3. Alternatively, a plurality of band-like common electrodes CE may be arranged in the first direction X or in the second direction Y. The common electrode CE is formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The second alignment film202covers the common electrode CE.

The array substrate AR and the countersubstrate CT are attached such that the first alignment film102and the second alignment film202are opposed to each other. The liquid crystal layer LC includes liquid crystal molecules LM and is held between the first alignment film102and the second alignment film202.

The optical element OD is disposed on a surface of the countersubstrate CT which does not contact the liquid crystal layer LC. The optical element OD includes, for example, a retardation plate RT and a polarizer PL. The retardation plate RT is, for example, adhered to the second insulating substrate200. For example, the retardation plate RT is composed of a one-fourth wavelength plate and a half wavelength plate layered one another, and the retardation plate RT reduces wavelength dependency and achieves desired phase difference within the wavelength range used for the color display. The polarizer PL is layered on the retardation plate RT.

The lightguide plate LG further includes an anisotropy scattering layer6having scattering anisotropy corresponding to incident angles of light. The anisotropy scattering layer6is, for example, adhered to the first main surface F1of the lightguide member1. The anisotropy scattering layer6passes the light incident from specific directions while diffusing the light incident from other specific directions.

As depicted by solid lines in the figure, light of the specific direction passing through the first main surface F1of the lightguide member1or external light of the specific direction passing through the lightguide member1is not diffused and passes through the anisotropy scattering layer6to enter the display panel PNL. The light is reflected by the pixel electrode PE1to PE3, again reaches the anisotropy scattering layer6and diffused thereby, and passes through the lightguide member1. The light passing through the lightguide member1is recognized as an image. The anisotropy scattering layer6is arranged between the polarizer PL and the countersubstrate CT.

For example, a user of the display device DSP sees the display area DA while keeping the interconnection area LA side of the display as shown inFIG. 23closer to himself/herself. In such a state, the visibility of the displayed image can be improved by setting the distrbution of angle of inclination of the reflective elements2to the above mentioned ranges, that is, between 10 and 50°, preferably 30 and 45°, and more preferably 37 and 43° to suit the angle of light passing through the first main surface F1and the angle of light reflected by the pixel electrodes PE1to PE3for the anisotropy scattering layer6.

Furthermore, as explained with reference toFIG. 9, with dummy reflective elements3, the luminosity of the light passing through the lightguide member1is substantially uniformed on the X-Y plane by pixel electrodes PE1, PE2, and PE3, and a good display image without unevenness can be achieved.

The same advantages obtained by the other embodiments can be achieved by the present embodiment.

Now, the sixth embodiment will be explained. In the present embodiment, an example of a display device including an illumination device as a frontlight and having a function as a touch sensor (touch panel, or touch screen).

FIG. 25is a schematic perspective view which shows a display device DSP of the present embodiment.

The display device DSP includes a display panel PNL and an illumination device LD. The display device DSP is, for example, a liquid crystal display device, and the display panel PNL therein has a structure similar to that of the fifth embodiment. The illumination device LD includes a lightguide plate LG and a light source LS, and may be of any example of the first to fourth embodiments.

The display device DSP includes a drive electrode TX and a detection electrode RX. The drive electrode TX and the detection electrode RX are opposed to each other. The drive electrode TX and the detection electrode RX compose a capacitance touch sensor which can detect an object contacting or approaching the display device DSP on the basis of a change in detection signals obtained from the detection electrode RX when supplying drive signals to the drive electrode TX.

In the example ofFIG. 25, a plurality of drive electrodes TX are provided with the display panel PNL, and they extend in the second direction Y and are arranged in the first direction X in the display area DA. Each drive electrode TX is formed of a transparent conductive material such as ITO or IZO. The drive electrodes TX may be disposed on a main surface of the display panel opposed to the illumination device LD, or may be disposed inside the display panel PNL. In the latter case, the common electrode CE shown inFIG. 24may be used as the drive electrodes TX. Or, the drive electrodes TX may be formed on the first main surface F1of the illumination device LD. In that case, the drive electrodes TX may still be formed in a band-like shape extending in the second direction Y and arranged in the first direction X to cross the detection electrode RX.

On the other hand, in the example ofFIG. 25, a plurality of detection electrodes RX are provided with the lightguide plate LG, and they extend in the first direction X and are arranged in the second direction Y in an area opposed to the display area DA. Each detection electrode RX may be formed of a transparent conductive material such as ITO or IZO. Alternatively, each detection electrode RX may be a metal fine line. In that case, an arrangement pattern of detection electrodes RX may include one or more waveform detection lines or may include mesh-like detection lines. Electrically floating dummy detection lines may be provided between detection electrodes RX to uniform the distribution density of the detection lines within the display area DA. The metal fine lines may possibly block light, and by setting the distribution density of the detection lines uniform, the optical affection of the light to the image displayed on the display area DA can be reduced.

The detection electrodes RX may be disposed on the second main surface F2of the lightguide member1, or may be disposed inside the lightguide member1. In the latter case, the detection electrodes RX may be disposed in the same layer where the reflective elements2are disposed such that the detection electrodes RX and the reflective elements2are manufactured in the same manufacturing process.

An example of this manufacturing process will be explained with reference toFIGS. 26 to 28. Here, a case where the lightguide plate LG is structured as in the first embodiment except for the detection electrodes RX will be given. In each figure, item (a) is a partial perspective view of the lightguide plate LG during the manufacturing process, and item (b) is a partial cross-sectional view of the lightguide plate LG in the Y-Z plane.

Initially, as shown inFIGS. 26(a) and 26(b), a plurality of projecting patterns PT1are formed on a second main surface10bof a transparent base material10.

Then, as inFIG. 27(a), a detection line7is formed on the second main surface10bof the transparent base material10. In the example ofFIG. 27(a), the detection line7extends substantially parallel with the first end E1, and overlaps a part of projecting patterns PT1on the second main surface10b. In this process, the detection line7and the reflective elements2with respect to projecting patterns PT1not overlapping the detection line7are formed at the same time. The diameter of projecting pattern PT1is made greater than the width of the detection line7to increase a margin in the overlapping part. Thus, the accuracy requirements in the manufacturing process can be eased. The detection line7partly covers projecting patterns PT1, for example. In the example depicted, the detection line7is formed such that projecting patterns PT1can be exposed in the first end E1side. The reflective elements2may not be formed on projecting patterns PT1not overlapping the detection line7. If a dummy detection line is formed as mentioned above, such a detection line may be formed to overlap projecting patterns PT1. As inFIG. 27(b), the detection line7includes a high-reflectivity layer70and a low-reflectivity layer71. If a foundation film for the high-reflectivity layers20and70and a foundation film for the low-reflectivity layers21and71are formed in this order, the reflective elements2and the detection line7can be formed at the same time by patterning the foundation films into the shape of the reflective elements2and the detection line7. If the high-reflectivity layers20and70are formed of aluminum or silver, good reflectivity and good touch operation detectability can be achieved.

After the formation of the reflective elements2and the detection line7, as inFIGS. 28(a) and 28(b), an overcoat layer11is formed on the second main surface10of the transparent base material10to cover the reflective elements2, detection lines7, and projecting patterns PT1. The lightguide plate LG is achieved as above.

The above manufacturing process has been explained with the lightguide plate LG structured as in the first embodiment. However, the reflective elements2and the detection line7can be manufactured through the same manufacturing process in the same layer even if the lightguide plate LG is structured as in any of the second to fourth embodiments.

By forming the detection line7to expose projecting patterns PT1in the first end E1side, the part of the detection line7overlapping projecting patterns PT1can function as the reflective elements2such that the light reflected by the high-reflectivity layer70of the detection line7and passing through the first main surface F1can have anisotropy.

Note that the function of the touch sensor may be applied to the display device DSP by a different method from the method used in the present embodiment. For example, both drive electrodes TX and detection electrodes RX may be disposed in the display panel PNL. In that case, the detection electrodes RX may be disposed on the outer surface of the countersubstrate CT (the surface opposed to the illumination device LD) and a common electrode CE may be used as the drive electrodes TX. Or, drive electrodes TX and detection electrodes RX may be arranged alternately on the same plane. Or, drive electrodes TX may be disposed on a main surface of a substrate which is provided separately from a display panel PNL and an illumination device LD, and detection electrodes RX may be disposed on the other main surface, and the substrate may be disposed on the lightguide member1in the second main surface F2side or may be interposed between the first main surface F1and the display panel PNL.

In theFIGS. 27 and 28, the detection line7overlaps a part of projecting pattern PT1such that the overlapping part of the detection line7functions as a reflective element2. However, the detection line7may be disposed to avoid projecting patterns PT1. In that case, the drive electrodes TX may extend in the first direction X and be arranged in the second direction Y, and the detection electrodes RX may extend in the second direction Y and be arranged in the first direction X.

Furthermore, in the present embodiment, a mutual capacitance detection touch sensor using both drive electrodes TX and detection electrodes RX has been described; however, the detection method of the touch sensor is not limited thereto. For example, a self capacitance detection touch sensor using detection electrodes RX alone may be adopted. In this detection method, an object contacting or approaching the display device DSP can be detected on the basis of a change in the self capacitance of the detection electrodes RX.

Several embodiments have been described above which are merely examples and do not limit the scope of the invention. Above novel embodiments can be achieved in various models, and various omission, substitution, and modification of the embodiments can be performed within the spirit of the invention. Such embodiments and their variations are encompassed by the description of the invention, and abstract, and are encompassed within the scope of the claims of the present application and their equals.

For example, the structured of the above embodiments can be combined arbitrarily.

Furthermore, in each embodiment, to apply anisotropy to the light passing through the first main surface F1of the lightguide member1, the barycenter of the reflective element2and the barycenter of each pattern PT1, PT2, and PT3is shifted on the X-Y plane. However, the barycenter of the reflective element2and the barycenter of each pattern PT1, PT2, and PT3may be matched on the X-Y plane to avoid anisotropy. In that case, the center of curvature of the reflective surface20ais positioned closer to the first main surface F1side than if the reflective surface20ato set the angle of light reflected by the reflective surface20aand passing through the first main surface F1within a specific range.

In the above embodiments, an additional element such as a cover glass may be provided with the lightguide member1in the second main surface F2side. Such an element may be considered as a part of the lightguide plate LG or may be considered as a part of the illumination device LD. Or, it may be considered as a part of the display device DSP.