JP4559791B2 - Display device - Google Patents

Description

The present invention relates to a display device such as a liquid crystal display element .

  In recent years, liquid crystal display devices are frequently used in portable information devices and flat panel displays, and in many liquid crystal display devices, a backlight unit is used for video display. The backlight unit is required to have high brightness for high image quality and power saving.

  The backlight unit has a light source such as a cold cathode tube or an LED as its light source, and a light guide plate is used to make light from these light sources into a planar shape.

  For example, in Patent Document 1, a lens sheet for improving the front luminance is used to increase the luminance of the backlight unit. This lens sheet has a structure in which triangular prisms are arranged. Of the light emitted from a line light source such as a cold cathode tube or an LED or a point light source and passed through a light guide plate and diffused as a planar light source, the lens sheet is guided. Light emitted in an oblique direction with respect to the light plate is directed in the front direction of the liquid crystal display element.

  On the other hand, an attempt has been made to apply an electroluminescence element (hereinafter referred to as “EL element”) as a surface light source that can be used in a backlight unit. This EL element is a light-weight and thin surface-emitting element. The EL elements can be broadly classified by applying a DC voltage to the organic material to recombine electrons and holes to emit light, and applying an AC voltage to the inorganic material to cause collisional excitation of electrons in the luminescent material. Inorganic EL elements that emit light. Furthermore, the latter inorganic EL element is a light-emitting layer by dispersing thin-film inorganic EL elements having an insulating layer on both sides or one side of a thin-film light-emitting layer having a film pressure of about 1 μm, and phosphor particles dispersed in an organic binder. A distinction is made between dispersed inorganic EL elements.

  The advantage of applying such an EL element to a backlight unit is that the EL element can be used as a surface light source, and therefore the surface is obtained using light from a linear light source such as the aforementioned cold cathode tube or LED, or a point light source. It is mentioned that the light guide plate required for realizing the light source is unnecessary.

  However, for example, the dispersion type inorganic EL element has insufficient luminance. Therefore, it is only used for some mobile phones at present. In addition, for example, organic EL elements have been rapidly developed in recent years, but the brightness and the lifetime are not compatible. There is a demand for further improvement in luminance of EL elements as surface light sources.

Although it is possible to use the above-described lens sheet for improving brightness as a means for improving the brightness of the EL element, this lens sheet is diffused from a line light source or a point light source through a light guide plate for use as a surface light source. When the EL device is a surface light source, the light component in the oblique direction is directed to the front direction, and its effect is weak because the light component in the oblique direction is relatively small. Therefore, a lens sheet has been devised in which convex or concave conical lenses as shown in Patent Document 2 are arranged.
JP 2004-004970 A JP 2003-059641 A

  Improvement of the luminance of the above-described EL element itself is an important issue, but at the same time, improvement of light utilization efficiency is also an important issue. In a liquid crystal display device, light from a backlight unit is normally transmitted to a liquid crystal display element to display an image. However, each display pixel on the liquid crystal display element is formed with a wiring and a transistor, and not all light passes through the liquid crystal display element. Of the light incident on the liquid crystal display element, the ratio of the transmitted light is indicated by the aperture ratio. In the case of a transmissive liquid crystal display element, the aperture ratio is usually about 10% to 50%. That is, more than half of the light emitted from the backlight unit is irradiated to the non-transmissive portion, and most of the light irradiated to the non-transmissive portion is absorbed. Therefore, the light use efficiency is lowered, which is one of the factors that hinder the improvement of the luminance of the liquid crystal display element. The lens sheet for improving the luminance of the EL element as in Patent Document 2 is not a solution to the above problem of low utilization efficiency, and still remains in a state of low utilization efficiency.

  The present invention has been made in view of the above problems, an EL element with improved light use efficiency than before, a lens sheet that improves light use efficiency using a light source such as an EL element, and the like, and An object of the present invention is to provide a display device with high brightness using these light sources.

The present invention is a display device having a lens sheet that is arranged between a display element and a backlight unit and transmits light incident from the backlight unit and emits the light to the display element. A scattering lens portion having an opening provided corresponding to a display pixel and a non-opening that does not transmit light, and the lens sheet has an effect of scattering incident light in a direction substantially parallel to the lens sheet And a directional lens portion having an effect of directing incident light in a direction substantially perpendicular to the lens sheet, and the directional lens portion of the lens sheet is parallel to the opening of the display element, It is provided in the position which overlaps substantially by planar view .

The lens sheet has a structure in which a scattering lens portion and a directional lens portion are regularly arranged with a predetermined periodicity .

In the display device of the present invention , the lens sheet has a scattering lens portion having an effect of scattering incident light in a direction substantially parallel to the lens sheet, and an effect of directing incident light in a direction substantially perpendicular to the lens sheet. The directional lens portion of the lens sheet is parallel to the opening of the display element, and is provided at a position that substantially overlaps in plan view. a is possible that the condensing lens having a light directing effect can be light use efficiency to realize a display device which is improved than before.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic cross-sectional view of an electroluminescence element (EL element) 1 according to the present invention. The EL element 1 includes a lens sheet 11, a transparent substrate 12, a transparent electrode 13, a light emitting layer 14, and a back electrode 15.

  In the EL element 1 of the present embodiment, the light emitting layer 14 emits light when a predetermined driving voltage is applied between the transparent electrode 13 and the back electrode 15 by a driving power source (not shown), and light from the light emitting layer 14 is emitted. Is emitted upward of the EL element through the transparent electrode 13, the transparent substrate 12, and the lens sheet 11.

  The lens sheet 11 of this embodiment is formed integrally with the transparent substrate 12, and has a lens 11a having a light scattering effect (hereinafter referred to as "scattering lens") and a lens having a light directing effect (hereinafter referred to as "directing lens"). The two types of lenses 11b are formed on the surface.

  As shown in FIG. 2, the scattering lens 11a and the directional lens 11b are arranged at a specific period d, for example, at an interval of 100 μm per one lens 11a or 11b. In the EL element 1, both the lenses 11a and 11b are alternately arranged both vertically and horizontally. In the present embodiment, a quadrangular pyramid-shaped lens is used for both the lenses 11a and 11b. The scattering lens 11a and the directional lens 11b are alternately arranged in a cycle of two or two in the width direction and two or three in the length direction. Is arranged. Moreover, the height of the scattering lens 11a is formed lower than that of the directional lens 11b. The height of the scattering lens 11a is preferably ½ or less of the height of the directional lens 11b. Further, the apex angle of the lens is preferably 120 degrees or more in the scattering lens 11a, and is preferably 120 degrees or less in the directional lens 11b.

  Examples of the material of the lens sheet 11 include polymer materials such as acrylic resin, polystyrene, polyolefin, polycarbonate, and polyester, and glass.

  The material and thickness of the transparent substrate 12 are not particularly limited as long as the transparent substrate 12 is a material and thickness that transmits at least a desired band of light. For example, the material is a high material such as polyethylene terephthalate, polyethylene, polypropylene, polyimide, and polyamide. Molecular materials, glass, quartz and the like can be used.

  As long as the transparent electrode 13 is conductive and has a thickness and a material that transmits light in a desired band, the material and thickness are not particularly limited. For example, the material is a metal such as ITO or ZnO. Oxides, metals such as Au, Ag, and Al, polymer materials such as polyaniline, polypyrrole, PEDOT / PSS, and polythiophene can be used.

  The light emitting layer 14 is composed of, for example, a single layer or multiple layers of an inorganic compound such as zinc sulfide or an organic compound such as Alq3. In the case of being composed of multiple layers, a layer that does not contribute to light emission, for example, an insulating layer made of an inorganic ferroelectric material, a hole transport layer made of an organic compound such as NPD, or the like may be included.

  The back electrode 15 is not particularly limited as long as it is conductive. For example, the material is a metal oxide such as ITO or ZnO, a metal such as Au, Ag, Al, or Cu, or a polymer such as polyaniline, polypyrrole, or PEDOT / PSS. A material, carbon, etc. can be used. Moreover, when taking out light from the back electrode 15 side, you may comprise with the electrode material transparent with respect to light emission wavelength, for example, the material similar to the transparent electrode 12, for example.

  Next, the operation of this embodiment will be described.

  FIG. 3 is a schematic cross-sectional view similar to FIG. 1, and in order to show the effect of the present invention, two optical paths of light emitted upward from the inner light emitting layer 14 are represented by solid and broken arrows. It represents using. Since the light emitting layer 14 emits light in all directions, the light emitted from the layer 14 is incident on the prism sheet 11 with any directionality. However, the light having an optical path other than that shown in the drawing is similarly applied to the present invention. The effect is demonstrated. In the optical path shown in the figure, the refraction at the boundary surface of the layer inside the element 1 is omitted, but it should be understood that refraction may occur inside the element 1. Even in that case, the effect of the present invention is exhibited in the same manner.

  Lights 31 and 32 incident on the transparent substrate 12 from the light emitting layer 14 pass through the transparent substrate 12 and enter the lens sheet 11 above the transparent substrate 12. Of these lights, the light 31 incident on the scattering lens 11a of the lens sheet 11 is refracted at the boundary surface with the outside above the scattering lens 11a (hereinafter referred to as the output at the interface between the scattering lens 11a and the outside of the EL element 1). The refracting action of the incident light is particularly referred to as a “scattering effect”. At this time, a part of the light 31 is incident on the inside of the lens, and the remaining light 31a is reflected by the directional lens 11b and reflected upward of the lens sheet 11. On the other hand, the light 32 incident on the directional lens 11b of the lens sheet 11 is refracted at the boundary surface with the outside above the directional lens 11b (hereinafter, the refracting action of the emitted light at the interface between the directional lens 11b and the outside of the EL element 1). The light reflecting action at the interface is particularly referred to as “directing effect”), and the light 32 is emitted above the lens sheet.

  When the lens element 11 has such a shape, when the EL element 1 is viewed from above, the EL element 1 has a high luminance portion and a low luminance portion repeated at a specific cycle. FIG. 4 is a partial plan view of the EL element 1 in a light emitting state as viewed from above, that is, the lens sheet 11 from above. When the lens sheet 11 is viewed from above, light is emitted with high luminance in the region R1 where the directional lens 11b is formed on the surface, and in the other region R2 where the scattering lens 11a is formed on the surface, Luminescence with a relatively low luminance is recognized compared to the luminance in the region R1. In FIG. 4, the difference in luminance is indicated by hatching.

  In the region R2 where the scattering lens 11a is disposed, the emitted light is scattered in a direction substantially parallel to the lens sheet 11, so that when viewed from above, the region has a low luminance, and the directional lens 11b is disposed. In the region R1, the light is directed in a direction substantially perpendicular to the lens sheet 11, and the light diffused in the horizontal oblique direction from the lens 11a having a light scattering effect is also directed upward, thereby being condensed. When viewed from above, the region has a relatively high luminance.

  Thus, by giving the scattering effect and the directing effect to the surface of the lens sheet 11 using the scattering lens 11a and the directional lens 11b, it is possible to give the EL element 1 a distribution of the intensity of the desired light intensity. Therefore, the light use efficiency of the entire EL element 1 is improved by concentrating light energy in a region where strong luminance is required and using the light.

In the embodiment described above it has been described using an example of using a lens convex upwardly as the lens sheet, may be concave. Further, although an example using a quadrangular pyramid shape as the lens shape has been described, the present invention is not limited to this, and a lens having a curved surface shape such as a polygonal pyramid, a cone, or a hemisphere may be used. . Furthermore, although the case where the arrangement of the lenses is alternately arranged in both the vertical and horizontal directions is shown, the arrangement may be given only in one direction. In this case, the lens shape is not limited to the above shape, as shown in FIG. At least two types of triangular prism lenses 11c and 11d whose longitudinal directions are arranged in parallel to the surface of the lens sheet 11 can be used. Further, in the present embodiment, only two types of lenses, one type of scattering lens 11b and one type of directional lens 11a, have been described. However, for example, there may be a plurality of types of scattering lenses and a plurality of types of directional lenses. Furthermore, there may be a plurality of types. Moreover, although the lens sheet 11 has a structure formed integrally with the transparent substrate 12, it may be formed separately and overlaid, and may be further laminated with an adhesive or the like.

  In addition, the lens sheet of this embodiment can also be used for the conventional light source which used the light-guide plate etc. other than the planar light source comprised with an electroluminescent element.

6 (a) and 6 (b) show the configuration of the display device according to the present invention, and FIG. 6 (a) is a schematic cross-sectional view taken along line AA of the perspective view of FIG. 6 (b). is there. The display device 4 includes an EL element 41, a lens sheet 411, and a liquid crystal display element 42.

The EL element 41 is substantially the same as the part excluding the lens sheet 11 in the EL element 1 described in the above embodiment, and is arranged to emit light at least upward in the drawing. Unlike the above embodiment, the lens sheet 411 is configured separately from the EL element 41. The lens sheet 411 is substantially equivalent to the lens sheet 11 of the above-described embodiment, and includes a scattering lens 411a having a scattering effect and a directional lens 411b having a directing effect.

  The lens sheet 411 is disposed between the EL element 41 and the display element 42. The EL element 41 and the lens sheet 411 function as a backlight unit for the display element 42.

  The display element 42 is a transmissive or transflective matrix-driven liquid crystal display element. For example, a TN liquid crystal display element, an STN liquid crystal display element, a DSTN liquid crystal display element, a TFT liquid crystal display element, or an MIM liquid crystal. A display element or the like can be used, and a TFT type liquid crystal display element is particularly preferable.

  As described above, such a transmissive or transflective matrix-driven liquid crystal display element 42 includes wirings, transistors, and a black matrix between display pixels. Is not transmitted. That is, the opening (translucent portion) 421 that is a portion through which light can be transmitted in the liquid crystal display element 42 is limited.

  In FIG. 6B, each of the openings 421 is a pixel that constitutes the display device 4. In addition, the arrangement of the pixels included in the liquid crystal display element 42 and the arrangement of the directional lenses 411b included in the lens sheet 411 are arranged so as to substantially match. Therefore, the positions of the opening 421 and the directional lens 411b substantially coincide with each other in plan view. At the same time, the portion of the liquid crystal display element 42 that does not transmit light, that is, the non-opening portion (non-light transmitting portion) 422, and the scattering lens 411a included in the lens sheet 411 substantially coincide with each other in plan view.

  In the present embodiment in which the lenses 411a and 411b are configured in a quadrangular pyramid shape, a quadrilateral that defines the periphery of the opening 421 that is a quadrilateral, and a quadrilateral four sides that define the peripheral edge of the directional lens 411b group located immediately below It is desirable that they substantially overlap in plan view. When the lenses 411a and 411b have shapes other than the quadrangular pyramid shape, the lenses 411a and 411b are virtually formed by connecting the vertices of the directional lens 411b located on the outermost side of the directional lens 411b group located directly below the opening 421. The first side of the quadrilateral that is virtually formed as described above, in a position that is completely included in the quadrangle that defines the opening 421 immediately above in plan view, The second side, the third side, and the fourth side may be parallel to the first side, the second side, the third side, and the fourth side of the quadrangle that defines the periphery of the opening. desirable.

  In addition, it is desirable that the area of the opening region of each opening 421 and the area of the region on the lens sheet 411 in which the group of directional lenses 411b located immediately below are the same. This is because, when the areas are not the same, in particular, when the area of the directional lens 411b group is larger than the opening area of the opening 421 immediately above the area, there is a possibility that the light use efficiency may be reduced. This is because when the area of the region of the 411b group is smaller than the opening region of the opening 421 immediately above it, the luminance of the liquid crystal display device may be lowered.

  The operation of the display device configured as described above will be described. The EL element 41 emits light when a voltage is applied from a driving power source (not shown), and the emitted light is irradiated to the liquid crystal display element 42 through the lens sheet 411. In the lens sheet 411, the incident light is scattered by the scattering lens 411a, thereby being condensed on the directional lens 411b, and directed upward by the directional lens 411b. Since the opening 421 of the liquid crystal display element 42 is disposed on the directional lens 411b, the light condensed by the directional lens 411b is incident on the opening 421 and is transmitted therethrough, so that the display surface 4a of the display device 4 is displayed. Is emitted. Therefore, the utilization efficiency of the light emitted from the EL element 41 is improved.

In the present embodiment, the lens sheet 411 can take various shapes and arrangements as in the embodiments described with reference to FIGS . The lens sheet 411 is configured separately from the EL element 41, but may be configured integrally with the EL element 41. Conversely, it may be formed integrally with the liquid crystal display element 42.

  The electroluminescence element of the present invention can increase the brightness with a specific pattern by partially condensing and directing light. Therefore, it is particularly useful as a light source for a backlight unit of a display device using a liquid crystal display element. Furthermore, the display device of the present invention can display a high luminance image by using this electroluminescence element, and is particularly useful as a display device for a portable information terminal or a flat panel display.

1 is a schematic cross-sectional view of an electroluminescent device according to an embodiment of the present invention. 1 is a perspective view of the electroluminescence element shown in FIG. Schematic diagram showing the optical path and emission direction of light transmitted through the lens sheet shown in FIG. Partial plan view of the lens sheet shown in FIG. The perspective view which shows the modification of embodiment of this invention (A): cross-sectional schematic view of a display device according to an embodiment of the present invention, (b): a perspective view of a display device according to an embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electroluminescent element 11 Lens sheet 11a Scattering lens 11b Directional lens 12 Transparent substrate 13 Transparent electrode 14 Light emitting layer 15 Back electrode 31 Optical path of light passing through scattering lens 32 Optical path of light passing through directional lens 4 Display device 41 Electroluminescent element 411 Lens sheet 411a Scattering lens 411b Directional lens 42 Liquid crystal display element 421 Opening (translucent part) of liquid crystal display element
422 Non-opening part (non-translucent part) of liquid crystal display element

Claims (2)

A display device having a lens sheet that is disposed between a display element and a backlight unit and transmits light incident from the backlight unit and emits the light to the display element, the display element corresponding to a display pixel And a non-opening that does not transmit light, and the lens sheet has an effect of scattering incident light in a direction substantially parallel to the lens sheet, and a lens sheet A directional lens portion having an effect of directing incident light in a substantially vertical direction, and the directional lens portion of the lens sheet is parallel to the opening of the display element and is substantially in plan view A display device characterized in that the display device is provided at an overlapping position . The display device according to claim 1, wherein the lens sheet has a structure in which a scattering lens unit and the directional lens unit are regularly arranged with a predetermined periodicity .

Images