JP2005338680A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device which can obtain a favorable display form by suppressing the luminance decline in a display image formed by a transmission type display element. <P>SOLUTION: A display device 12 at least has a light source 19; a transmission type display element 18 which is illuminated by a light from the light source 19, which is placed at the forward side of the light source 19 with a prescribed spacing; a light guiding member 22 which is placed between the transmission type display element 18 and the light source 19. The light guiding member 22 has an incident part 22a on which the light is incident from the light source 19, and an emission part 22e which emits the light from this incident part 22a to the transmission type display element 18 side. The incident part 22a consists of a first incident part 22b on which the light emitted along an optical axis L3 of the light source 19 is incident, and a second incident part 22c on which a light emitted to the region deviated from the optical axis L3 is incident. In the illumination path from the second incident part 22c to the emission part 22e, a reflection part 22d to reflect the light comes into the light guiding member 22 in the optical axis L3 direction through the second incident part 22c is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a display device, and more particularly to a display device having a light source that illuminates a transmissive display element (for example, a transmissive liquid crystal display element) from behind.

Conventionally, in this type of display device, for example, a display device used for a head-up display device that displays a virtual image by reflecting a display image emitted from a liquid crystal display element with light emission of a light source is known (for example, the following). Patent Document 1). The head-up display device described in Patent Document 1 displays a virtual image by reflecting the display image projected by a display device disposed on a dashboard of a vehicle in the direction of a user with a windshield of the vehicle. is there.
JP 11-310055 A

  An example of a display device which is a backlight illumination means used in such a head-up display device will be described with reference to FIG. The display device A includes a liquid crystal display element 1 in which a polarizing member is attached to the front and back surfaces of a liquid crystal cell in which liquid crystal is sealed between a pair of translucent substrates, an illumination unit 2 that illuminates the liquid crystal display element 1 from behind, The lens array 3 is interposed between the liquid crystal display element 1 and the illumination unit 2.

  The illumination unit 2 includes a light source group 2b composed of a plurality of LEDs 2a that illuminate the liquid crystal display element 1, a circuit board 2c on which a predetermined wiring pattern for supplying power to each LED 2a is formed, and the circuit board 2c. And a metal plate 2d for collecting heat generated from each LED 2a.

  Each LED 2a is formed of a chip-type light emitting diode, and is mounted on the surface of the circuit board 2c at equal intervals. In this case, a light source group 2b is constituted by five LEDs 2a arranged in a row. Moreover, the light irradiation area | region angle of each LED2a is each set to the range of 120 to 180 degree | times, for example. This means that each LED 2a has a directivity of about 60 degrees to about 90 degrees to the left and right with respect to the light irradiation direction. The circuit board 2c and the metal plate 2d are electrically insulated by an insulating member (not shown) and bonded via an adhesive layer (not shown). The lens array 3 is configured by integrally forming a plurality of lenses 3a corresponding to the respective LEDs 2a arranged in a row, and light from each LED 2a is irradiated to the liquid crystal display element 1 side through the lens 3a. It was supposed to be.

  In the case of the display device A, a plurality of (five) LEDs 2a having a light irradiation region angle (directivity) of 120 to 150 degrees are mounted in a row on the circuit board 2c, and light emitted from each LED 2a. Is made incident on a plurality of lenses 3a facing each LED 2a.

However, the light emitted by the two LEDs arranged at both ends of the five LEDs 2a is not incident on the lens 3a because the directivity of the LEDs is set from 120 degrees to 150 degrees. Is emitted as leakage light to the outside of the lens 3a, it is difficult to irradiate the light emitted from each LED 2a to the transmissive display element side which is the liquid crystal display element 1 through the lens 3a without waste. The luminance of the display image emitted from the transmissive display element is lowered, and there is a problem that a good display form cannot be obtained.
In view of the above-described problems, an object of the present invention is to provide a display device capable of obtaining a favorable display mode by suppressing a decrease in luminance of a display image emitted from a transmissive display element. Is.

  The present invention includes a light source, a transmissive display element that is disposed on the front side of the light source with a predetermined interval and is illuminated by light from the light source, and is disposed between the transmissive display element and the light source. The light guide member includes an incident portion that receives light from the light source and emits light from the incident portion toward the transmissive display element. A first incident part for incident light emitted along the optical axis of the light source, and a second incident for incident light emitted in a region off the optical axis. And a reflection part for reflecting light taken into the light guide member through the second incident part in the direction of the optical axis in the illumination path from the second incident part to the emitting part. It is characterized by that.

  In the invention, it is preferable that the emitting portion has a waveform shape.

  According to the present invention, a lens is disposed between the transmissive display element and the light guide member.

  Further, the present invention is characterized in that the incident portion is formed in a substantially concave shape.

  Further, the invention is characterized in that a display image emitted from the surface side of the transmissive display element is projected on a display unit through a concave reflector.

  ADVANTAGE OF THE INVENTION According to this invention, the initial objective can be achieved and the display apparatus which can obtain a favorable display form can be provided by suppressing the luminance fall of the display image which a transmission type display element emits.

(First Embodiment) Hereinafter, an embodiment in which the embodiment of the present invention is applied to a vehicle head-up display for displaying vehicle speed, engine speed, etc. will be described as an example with reference to the accompanying drawings.

  FIG. 1 shows a vehicle head-up display mounted on a vehicle. A display image (display light) L1 projected by a display device 12 provided on an upper portion of a dashboard 11 of a vehicle 10 is displayed on a windshield (display unit). ) 13 is reflected in the direction of the user 14. The user 14 can observe the display image L1 as a virtual image V superimposed on the landscape.

  In addition, the display device 12 according to the present embodiment includes an illumination unit 17 made of various members such as a concave mirror (concave reflector) 16 and a liquid crystal display in a housing 15 provided so as to be embedded in the upper part of the dashboard 11. This will be described with reference to FIG.

  The housing 15 is made of a light-shielding synthetic resin material, and is provided with an opening 15a that opens an upper portion (on the windshield 13 side) where the concave mirror 16 is disposed. The housing 15 is provided with a translucent cover 15b made of a translucent synthetic resin material (for example, acrylic resin) so as to close the opening 15a. In addition, 15c is an opening part for exposing the fin of the heat radiating member mentioned later to the housing 15 exterior, and this opening part 15c is provided in the wall part located in the right side of the housing 15 in FIG.

  The concave mirror 16 reflects a display image L1 projected from a liquid crystal panel (to be described later) of the illumination unit 17 toward the windshield 13 and is provided so that the user 14 can easily adjust the angle so that the user 14 can easily view the display image L1. ing. The concave mirror 16 is formed of a reflective surface having a predetermined curvature in order to enlarge and display the display image L1 emitted from the liquid crystal panel on the windshield 13.

  The illumination unit 17 includes a liquid crystal panel (transmissive display element) 18, a light source 19 that illuminates the liquid crystal panel 18, a circuit board 20 that supplies power for lighting to the light source 19, and a back surface of the circuit board 20. A heat dissipating member 21, a light guide member 22 disposed in an illumination path from the light source 19 to the liquid crystal panel 18, and a diffusion member 23 interposed between the light guide member 22 and the liquid crystal panel 18. ing.

  The liquid crystal panel 18 is obtained by attaching polarizing members to the front and back surfaces of a liquid crystal cell in which liquid crystal is sealed in a pair of translucent substrates, for example. The liquid crystal panel 18 includes an arithmetic circuit (not shown) that measures the vehicle speed and the engine speed based on output signals from a vehicle speed sensor and an engine rotation sensor provided in the vehicle 10 and a liquid crystal drive that drives the liquid crystal based on the calculation result. A circuit (not shown) can display the measured value of the speed of the vehicle 10 or the engine speed as a numerical value. Note that the liquid crystal panel 18 is disposed at a substantially central portion of the housing 15 in FIG.

  The liquid crystal panel 18 projects the display image L1 onto the windshield 13 via the concave mirror 16, and as shown in FIG. 2, the light from the light source 19 disposed on the back side of the liquid crystal panel 18 is The display image L1 illuminated by passing through the liquid crystal panel 18 through the light guide member 22 and the diffusion member 23 is configured to be emitted toward the concave mirror 16 side.

  The light sources 19 are composed of, for example, chip-type light emitting diodes, and are mounted on a circuit board 20 disposed on the back side of the liquid crystal panel 18 at a predetermined distance from the liquid crystal panel 18 at equal intervals. A light emitter for causing the optical member 22 to emit light. Each light source 19 may have a light irradiation area angle narrower than 180 degrees. In this embodiment, the light source 19 has a directivity of about 60 degrees to about 75 degrees to the left and right with the optical axis L3 of the light source 19 as the center. The one with the characteristic is adopted. This means that each light source 19 in the present embodiment has a light irradiation region angle of approximately 120 degrees to approximately 150 degrees.

  The circuit board 20 is made of, for example, an aluminum board provided with a predetermined wiring pattern, and each light source 19 is mounted on the wiring pattern.

  The heat radiating member 21 is disposed so as to penetrate the front and back of the opening 15 c of the housing 15, and has a role for releasing the heat of each light source 19 transmitted to the circuit board 20 to the outside of the housing 15 when each light source 19 is turned on. Plays. Moreover, the heat radiating member 21 is provided with many fins 21a. Note that a heat radiating sheet (not shown) made of, for example, silicon rubber is interposed between the heat radiating member 21 and the circuit board 20.

  The light guide member 22 is made of a translucent acrylic resin, for example, and is formed in a substantially flat plate shape. As shown in FIG. 3, the light guide member 22 is provided with a concave portion 22a formed of a groove surrounding the upper end portion (light emitting surface) of each light source 19 at the bottom thereof.

  The concave portion 22a constitutes an incident portion capable of receiving all the light of the light source 19 emitted from the light irradiation region angle. In FIG. 3, 22b is a bottom wall surface of the concave portion 22a facing the light emitting surface of the light source 19. , A first incident part that mainly emits light emitted along the optical axis L3. In addition, the first incident portion 22b slightly protrudes toward the light emitting surface of the light source 19, and the light taken into the light guide member 22 through the first incident portion 22b is guided as straight light, and the light guide member 22, which will be described later. In addition, you may form the 1st incident part 22b in flat, without raising to the said light emission surface side as needed.

  In FIG. 3, reference numeral 22c denotes an inner wall surface (side wall surface) of the recess a, which is a second incident portion that mainly emits light from the light source 19 emitted in a region off the optical axis L3. And 22d is formed in the illumination path | route from the 2nd incident part 22c to the said radiation | emission part, and is inclined and extended in the surface side (the said emission part side) of the light guide member 22 so that the recessed part 22a may be surrounded. This is a reflecting portion that reflects the light introduced into the light guide member 22 through the second incident portion 22c toward the emitting portion side (in the direction of the optical axis L3). The reflected light reflected by the reflecting portion 22d is guided so as to surround the straight light, and reaches a later-described emitting portion of the light guide member 22. Note that the shape of the reflecting portion 22d is not limited to the dish shape, and any shape can be adopted, and for example, a linear inclined surface may be used. Reference numeral 22e denotes an emitting portion that irradiates the light that has been introduced into the light guide member 22 through the incident portions 22b and 22c, that is, the straight traveling light and the reflected light, onto the diffusing member 23 (liquid crystal panel 9) side.

  The diffusing member 23 is disposed along the back surface of the liquid crystal panel 18, diffuses the irradiation light L <b> 2 irradiated from the emitting portion 22 e of the light guide member 22, and evenly displays the display image L <b> 1 emitted from the liquid crystal panel 18. It has a function as a light diffusion plate for illuminating substantially uniformly (see FIG. 2).

  In such a configuration, when each light source 19 is turned on, the light emitted from each light source 19 is radiated into the incident portion 22a formed of a substantially concave portion so as to have the light irradiation region angle. The light along the axis L3 enters the light guide member 22 through the first incident portion 22b which is the bottom surface of the recess facing the light emitting surface of the light source 19. Further, light emitted from the radiated light in a direction deviating from the optical axis L3, for example, a direction inclined by 45 degrees with respect to the optical axis L3, enters the light guide member 22 through the second incident portion 22c.

  And the incident light which entered into the light guide member 22 by the 1st incident part 22b goes straight through the light guide member 22 as it is, and this straight advance light reaches the output part 22e. On the other hand, incident light that has entered the light guide member 22 by the second incident portion 22c is reflected through the reflecting portion 22d, and the reflected light is bent in the direction of the optical axis L3 so that the reflected light surrounds the straight light. The light is guided to the 22e side.

  Further, the straight traveling light and the reflected light that have reached the emission part 22e by the light emission of each light source 19 are irradiated as irradiation light L2 on the surface side (the diffusion member 23 side) of the emission part 22e, and this irradiation light L2 is the diffusion member. The liquid crystal panel 18 is illuminated by the light diffused by the light 23 and reduced in luminance unevenness. The light that illuminates the liquid crystal panel 18 is emitted as a display image L1 on the surface side of the liquid crystal panel 18, and this display image L1 is projected onto the windshield 13 through the concave mirror 16 and the translucent cover 15b. Thus, the user 14 can visually recognize the virtual image V by the display image L1.

  As described above, in the present embodiment, the light source 19 whose light irradiation region angle is approximately 120 degrees to approximately 150 degrees, the liquid crystal panel 18 illuminated by the light from the light source 19, the liquid crystal panel 18 and the light source 19 The light guide member 22 is provided between the light guide member 22 and the light guide member 22. The light guide member 22 is incident on the liquid crystal panel 18 side. A first incident portion 22b on which the incident portion 22a emits light emitted along the optical axis L3 of the light source 19, and light emitted in a region off the optical axis L3. The light incident on the light guide member 22 through the second incident portion 22c in the illumination path from the second incident portion 22c to the emitting portion 22e is formed in the direction of the optical axis L3. Reflecting part 22d to reflect Those digits.

  Therefore, when the light source is lit within the light irradiation region angle when the light source is turned on as in the prior art, a part of the radiated light is not radiated as leakage light outside the lens. Since all the light emitted radially can be incident on the incident portions 22b and 22c, the amount of the irradiation light L2 irradiated on the liquid crystal panel 18 side through the emission portion 22e can be sufficiently supplemented, thereby The decrease in luminance of the display image L1 emitted from the liquid crystal panel 18 is suppressed, and the user can visually recognize a good display form.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. 4. The same or corresponding parts as those in the first embodiment described above will be denoted by the same reference numerals and detailed description thereof will be given. Description is omitted. The second embodiment is different from the first embodiment in that the entire light emitting portion 22e of the light guide member 22 has a waveform shape. Thus, even when the user 14 moves slightly from a position where the virtual image V can be visually recognized, for example, and sees the virtual image V from the moved position, the waveform is provided in the emission portion 22e. Since the luminance change of the image L1 (virtual image V) is suppressed, it becomes possible for the user to visually recognize a good display form.

  In each of the above embodiments, the example in which the user 14 visually recognizes the virtual image V using the light guide member 22 having the three light sources 19 and the concave-shaped incident portions 22a corresponding to the respective light sources 19 has been described. One or two or more light sources 19 may be used to cause the user 14 to visually recognize the virtual image V.

  In each of the above embodiments, the case where the irradiation light L2 irradiated from the emission part 22e of the light guide member 22 is supplied to the diffusion member 23 has been described. However, for example, the clearance between the emission part 22e and the diffusion member 23 is increased. In the case where it cannot be ensured sufficiently, by disposing a lens on the back surface of the diffusing member 23, it is possible to obtain the same effects as those of the above embodiments. Furthermore, in this case, since the thickness of the illumination unit 8 in the direction of the irradiation light L2 is reduced, the illumination unit 8 itself can be made thinner.

  Further, in each of the above embodiments, the display device 12 is used as a head-up display device that reflects the display image L1 on the windshield 13 of the vehicle 10 toward the user 14 and displays the virtual image V. Without being limited, for example, the present invention is applied to a head-up display device that reflects the display image L1 in the direction of the user 14 using a projection member different from the windshield 13 that reflects the display image L1 in the direction of the user 14. May be. The display device according to the present invention may be used not only as a head-up display device but also as a backlight unit of a display device that allows a user to directly view a display image using a liquid crystal panel.

  In each of the above-described embodiments, the example in which the liquid crystal panel is used as the transmissive display element has been described. However, the present invention is not limited to this, and for example, electrochromic may be used as the transmissive display element.

1 is a schematic view of a head-up display device according to a first embodiment of the present invention. It is sectional drawing of the display apparatus by the same embodiment. It is a principal part enlarged view which expands and shows the B section in FIG. It is a principal part enlarged view of the display apparatus by 2nd Embodiment of this invention. It is sectional drawing which shows the conventional display apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Vehicle 11 Dashboard 12 Display apparatus 13 Windshield (display part)
15 Housing 16 Concave mirror (concave reflector)
17 Illumination unit 18 Liquid crystal panel (transmission type display element)
DESCRIPTION OF SYMBOLS 19 Light source 20 Circuit board 21 Heat radiating member 22 Light guide member 22a Incident part 22b 1st incident part 22c 2nd incident part 22d Reflective part 22e Output part 23 Diffusion member L1 Display image (display light)
L2 outgoing light L3 optical axis V virtual image

Claims (5)

A light source;
A transmissive display element disposed on the front side of the light source with a predetermined interval and illuminated by light from the light source;
A display device comprising at least a light guide member disposed between the transmissive display element and the light source,
The light guide member has an incident part for incident light from the light source, and an emission part for emitting light from the incident part to the transmissive display element side,
The incident part comprises a first incident part for incident light emitted along the optical axis of the light source, and a second incident part for incident light emitted in a region off the optical axis,
In the illumination path from the second incident part to the emission part, a reflection part is provided for reflecting light taken into the light guide member through the second incident part in the optical axis direction. Display device. The display device according to claim 1, wherein the emitting portion has a waveform shape. The display device according to claim 1, wherein a lens is disposed between the transmissive display element and the light guide member. The display device according to claim 1, wherein the incident portion is formed in a substantially concave shape. 5. The display device according to claim 1, wherein a display image emitted from the surface side of the transmissive display element is projected on a display unit through a concave reflecting plate. 6. .

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