JP2012099392A - Display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display capable of suppressing deterioration of an incoming light reflection reduction effect due to pasting of a prism sheet 15, and securing excellent visibility even in outdoor use.SOLUTION: A display 10 at least includes: a light-emitting device 12; a phase difference film 13; a polarizing film 14; and a prism sheet 15, on a substrate 11 having a reflective layer. An average refractive index of the phase difference film 13 is configured to be larger than a refractive index of the prism sheet 15.

Description

  The present invention relates to a display device, and more particularly to an image display device such as an organic electroluminescence (EL) display device.

  When a display device is used in a very bright place such as outdoors, display interference occurs due to reflection of external light. As a technique for reducing display interference due to reflection of external light, a technique is known in which a circularly polarizing film, which is a laminated film of a retardation film and a polarizing film, is installed on the surface of a display device. According to this technology, it is possible to reduce display disturbance that may occur when external light that has entered the display device is reflected inside the display device and is emitted to the outside of the display device again.

  For the purpose of reducing such display interference, a circularly polarizing film having a phase difference λ / 4 with respect to the light wavelength λ is used. As general λ, 550 nm, which has high human visual sensitivity, is used, and in this case, λ / 4 = 137.5 nm. Moreover, as an optical member used for a retardation film and a polarizing film, an optical member having a refractive index of about 1.5 is generally used. This is because by using an optical member close to the refractive index of the optical glass member to which the film is attached, reflection at the bonding boundary between the film and the optical glass member is reduced, and the transmittance is kept high.

  In addition, for the purpose of improving the display quality of a display device, a technology is known in which a sheet having a plurality of uneven structures on the surface of a prism sheet or the like is installed on the surface of the display device to control refraction and reflection on the sheet surface. Yes. For example, a technique is known in which light emitted from a display device is condensed in a front direction using a sheet having a large number of triangular prisms and microlenses as a surface having a concave-convex structure, thereby increasing the luminance in the front direction and improving display quality. . Furthermore, a technique has been proposed in which a sheet having a large number of retroreflective structures such as corner cubes is provided on the surface to reduce surface reflection of external light and improve display quality (see Patent Document 1). .

  An optical material having a refractive index of about 1.5 is generally used for a sheet having a plurality of uneven structures on the surface. This is because the reflection at the bonding boundary is reduced by matching with the refractive index of the optical glass member on which a sheet having a plurality of uneven structures on the surface is bonded, as in the case of the retardation film or polarizing film described above.

  Furthermore, a technique combining these two techniques is disclosed (see Patent Document 2). According to this technique, a circularly polarizing film is installed on the viewer side of the light emitting element, and a microlens sheet is installed as a sheet having a plurality of uneven structures on the surface of the viewer on the circularly polarizing film. Thereby, both external light reflection prevention by a circularly-polarizing film and front luminance improvement by a microlens can be compatible.

JP-A-11-316552 JP 2002-216947 A

  By the way, in the external light reflection of the display device, the case where the light incident from the normal direction of the display device is reflected inside the display device and emitted in the normal direction of the display device to reach the observer has the most influence on the display quality. To do. Therefore, in order to reduce the influence of external light reflection of the display device, it is necessary to reduce the light incident from the normal direction of the display device and reflected inside the display device.

  When a sheet having a plurality of uneven structures on the surface is installed on the circularly polarizing film as in Patent Document 2, light incident from the normal direction of the display device is reflected from the normal direction by the sheet having a plurality of uneven structures on the surface. It is incident on the circularly polarizing film at an inclined angle. However, generally used circularly polarizing films are optimized for light incident from the normal direction, and are not optimized for light incident from an angle inclined from the normal direction. Therefore, the light incident from a sheet having a plurality of uneven structures on the surface and passing through the circularly polarizing film can become elliptically polarized light without being completely circularly polarized. Therefore, the effect of reducing external light reflection by the circularly polarizing film may be reduced.

  Accordingly, the present invention suppresses a decrease in the effect of reducing external light reflection caused by sticking a sheet having a plurality of uneven structures on the surface thereof, such as a prism sheet, and can ensure good visibility even when used outdoors. The purpose is to provide.

  The configuration of the present invention made to achieve the above object is as follows.

That is, the display device according to the present invention is a display device including a light emitting element, a circularly polarizing film, and a sheet having a plurality of uneven structures on the surface in order on a substrate including a reflective layer,
The display device is characterized in that an average refractive index of a retardation film constituting the circularly polarizing film is larger than a refractive index of a sheet having a plurality of the uneven structures.

  According to the present invention, the average refractive index of the retardation film is set larger than the refractive index of the sheet having a plurality of uneven structures. Therefore, the fall of the external light reflection reduction effect resulting from sticking of the sheet | seat which has two or more uneven structures is suppressed, and the outstanding effect that favorable visibility can be ensured also at the time of outdoor use is exhibited.

It is the schematic which shows the cross-section of one Embodiment of the display apparatus which concerns on this invention. It is an isoluminance diagram which shows the reflectance characteristic of the circularly-polarizing film in this embodiment. It is an isoluminance diagram which shows the reflectance characteristic of the conventional circularly-polarizing film.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. In addition, the well-known or well-known technique of the said technical field is applied regarding the part which is not illustrated or described in particular in this specification.

  First, an embodiment of a display device according to the present invention will be described with reference to FIG. FIG. 1 is a schematic view showing a cross-sectional structure of an embodiment of a display device according to the present invention.

  As shown in FIG. 1, the display device 10 of the present embodiment is a sheet having at least a light emitting element 12, a retardation film 13, a polarizing film 14, and a plurality of concave and convex structures on a substrate 11 having a reflective layer. The prism sheets 15 are sequentially stacked.

  As the substrate 11 for a display device including the light emitting element 12 as in the present invention, a reflective layer such as a silver alloy or an aluminum alloy is formed on a glass substrate, a stainless steel (SUS) substrate, or the like by a sputtering method, a vapor deposition method, or the like. A film formed by the above method is generally used. The reflective layer can also be a part of the light emitting element 12 (also serves as an electrode), and an electrical wiring (not shown) and a drive circuit for driving the light emitting element 12 may be connected to the reflective layer. . In addition, a transparent insulating layer may be disposed between the reflective layer and the light emitting element 12 so that the reflective layer and the light emitting element 12 are not electrically connected.

  As the light emitting element 12 laminated on the substrate 11, an organic EL light emitting element, an inorganic EL light emitting element, a quantum dot light emitting element, an LED light emitting element, or the like is generally used.

  On the light emitting element 12, a retardation film 13 and a polarizing film 14 are attached. That is, a circularly polarizing film is configured by bonding the retardation film 13 and the polarizing film 14 together. It is generally known that when the retardation film 13 and the polarizing film 14 are bonded together, the optical axes of the retardation film 13 and the polarizing film 14 are bonded to each other with a shift of 45 °. The optical axis here may be either a transmission axis or an absorption axis in the case of the polarizing film 14, and may be either a slow axis or a fast axis in the case of the retardation film 13.

As the material of the retardation film 13, for example, a stretched transparent resin such as a polycarbonate resin or a cycloolefin resin is generally used. It is also common to adjust the refractive index of the transparent resin using methods such as adjusting the monomer structure before polymerizing these transparent resins and adding a refractive index adjusting agent based on metal oxide particles. It is. The average refractive index of the retardation film 13 in this embodiment is set larger than the refractive index of the prism sheet 15 described later. Here, the average refractive index referred to here, when the refractive indices n _x with respect to extraordinary light of the anisotropic medium of the retardation in the film, the refractive index for ordinary light and with n _y, in _{(n x + n y) /} 2 It is expressed.

  As the material of the polarizing film 14, for example, a film obtained by stretching a polyvinyl alcohol film and holding it with a triacetyl cellulose film is used. In the case of a small display device such as a head-up display, an optical crystal having birefringence may be used instead of the transparent resin.

  On the polarizing film 14 of the circularly polarizing film, a prism sheet 15 is attached as a sheet having a plurality of uneven structures on the surface. Here, a sheet having a plurality of uneven structures on the surface means a prism structure such as a triangular prism, a microlens structure, a retroreflective structure such as a corner cube, etc. on the surface in order to control refraction and reflection on the sheet surface. This is a sheet on which many uneven structures are installed. It is generally known that the pitch of the concavo-convex structure provided on the prism sheet 15 can prevent display interference such as moire by making it sufficiently smaller than the pitch of the light emitting elements 12. Alternatively, it is preferable that the pitch is set to 1 / integer of the pitch of the light emitting elements 12.

  Next, the effect of the display device 10 of the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 2 is an isoluminance diagram showing the reflectance characteristics of the circularly polarizing film in the present embodiment. FIG. 3 is an isoluminance diagram showing the reflectance characteristics of a conventional circularly polarizing film.

  In the display device 10 according to the present embodiment shown in FIG. 1, external light incident on the prism sheet 15 from the normal direction is refracted by the prism sheet 15 at an angle inclined from the normal direction. The refracted outside light passes through the polarizing film 14 and then enters the retardation film 13. At that time, since the average refractive index of the retardation film 13 in this embodiment is set to be larger than the refractive index of the prism sheet 15, external light enters the retardation film 13 at an angle close to the normal direction. Re-refracted and incident. Due to this refraction effect, the incident angle of external light is closer to the normal direction than when it was in the prism sheet 15, so that the influence of the angle dependency of the retardation film 13 can be reduced. That is, in the display device 10 of the present embodiment, the disturbance of circularly polarized light due to the influence of refraction on the slope on the prism sheet 15 can be reduced. As a result, it is possible to suppress a decrease in the external light reflection reduction effect of the circularly polarizing film, and it is possible to achieve good visibility outdoors.

  Here, in order to evaluate the external light antireflection performance of the circularly polarizing film in the present embodiment, the polar angle / azimuth angle characteristics of the external light reflectance when the circularly polarizing film is attached to the substrate having the reflective layer are shown in FIG. It is shown in 2. In the present embodiment, the average refractive index of the retardation film is 1.76. In addition, for comparison with the conventional external light reflectance characteristic, the polar angle / azimuth angle characteristics of the external light reflectance when the average refractive index is 1.5, which is a representative value of the refractive index of the prism sheet, are shown in FIG. 3 shows. Comparing FIG. 2 and FIG. 3, by increasing the average refractive index of the retardation film, the external light reflectance at an angle (80 degrees) deviating from the polar angle of 0 degrees (that is, the normal direction of the display device) is significantly reduced. I understand that That is, due to the effect of setting the average refractive index of the retardation film 13 to be larger than the refractive index of the prism sheet 15, the display device 10 of the present embodiment can reduce external light reflection of the circularly polarized film due to refraction of external light by the prism sheet 15. Can be suppressed. 2 and 3, concentric circle lines and azimuth lines that share the center point represented by the broken line are auxiliary lines, and do not represent measured values.

  The principle that outdoor visibility is improved by refraction when external light enters the retardation film 13 described above depends only on the relationship between the refractive index of the prism sheet 15 and the average refractive index of the retardation film 13. This is because the angles of light rays in the prism sheet 15 and the retardation film 13 are determined only by the respective refractive indexes according to Snell's law. Therefore, the basic effect of the present invention basically does not depend on the refractive index of the optical member between the prism sheet 15 and the retardation film 13.

  However, there is some reflection due to the difference in refractive index at each optical interface from the prism sheet 15 to the retardation film 13. In order to further reduce this reflection, the refractive index of at least one optical member A existing between the prism sheet 15 and the retardation film 13 is determined based on the refractive index value of the prism sheet 15 and the average refractive index of the retardation film 13. More preferably, it gradually increases to between the rate values.

  In the display device 10 of the present embodiment, a polarizing film 14 is present as the optical member A between the prism sheet 15 and the retardation film 13. The refractive index of the polarizing film 14 is more preferably set to be larger than the refractive index of the prism sheet 15 and smaller than the average refractive index of the retardation film 13. In this way, by setting the refractive index of the polarizing film 14 between the refractive indexes of the prism sheet 15 and the retardation film 13, in addition to the basic effect of the present invention, there is a further effect of reducing external light reflection. be able to.

  Further, the display device 10 of the present embodiment may have a configuration in which the transparent member B is provided between the prism sheet 15 and the circularly polarizing film 14. In the case of the configuration, the refractive index of the member B is preferably set to be larger than the refractive index of the prism sheet 15 and smaller than the refractive index of the circularly polarizing film 14. Further, the display device 10 of the present embodiment may have a configuration in which the member C is provided between the circularly polarizing film 14 and the retardation film 13. In the case of this configuration, the refractive index of the member C is preferably set to be larger than the refractive index of the circularly polarizing film 14 and smaller than the average refractive index of the retardation film 13.

  As described above, according to the display device 10 of the present embodiment, it is possible to suppress a decrease in the effect of reducing external light reflection caused by the attachment of the prism sheet 15, and thus it is possible to ensure good visibility even when used outdoors. .

  The preferred embodiment of the present invention has been described above. However, this is merely an example for explaining the present invention, and various embodiments different from the above-described embodiment may be implemented without departing from the gist of the present invention. Can do.

DESCRIPTION OF SYMBOLS 10 Display apparatus, 11 Substrate, 12 Light emitting element, 13 Phase difference film, 14 Polarizing film, 15 Prism sheet

Claims (4)

A display device comprising a light emitting element, a circularly polarizing film, and a sheet having a plurality of uneven structures on the surface in order on a substrate having a reflective layer,
An average refractive index of a retardation film constituting the circularly polarizing film is larger than a refractive index of a sheet having a plurality of the uneven structures. Between the retardation film and the sheet having a plurality of the uneven structure, comprising at least one optical member,
2. The display according to claim 1, wherein the refractive index of the optical member gradually increases from a refractive index value of the sheet having a plurality of the uneven structures to an average refractive index value of the retardation film. apparatus.   The optical member is a polarizing film, and the refractive index of the polarizing film is larger than the refractive index of the sheet having a plurality of the uneven structures, and smaller than the average refractive index of the retardation film. Item 3. The display device according to Item 2.   The display device according to claim 1, wherein the reflective layer is a part of the light emitting element.

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