JP2008009308A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device having high contrast, in which a light control means is used in place of a light diffusion layer and the failure in the case when the light diffusion layer is used is eliminated. <P>SOLUTION: The display device (10) has a light source (30), a display part (20) having an electro-optical conversion element (23), and a light control means (24) having a plurality of reflection faces (50) for conducting light made incident from the light source into the display part, and the reflection faces diffuse the light emitted to the visually recognizing side from the light control means so that the haze ratio may be 5-40%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a display device, and more particularly to a display device with high contrast over the entire display area.

  In a reflective liquid crystal device, it is known to use a front light that makes light incident from a side surface of the reflective liquid crystal device (see, for example, Patent Document 1).

  FIG. 1 is a diagram showing an outline of an example of the reflective liquid crystal device as described above.

  As shown in FIG. 1A, the reflective liquid crystal device 1 encloses the first transparent substrate 2, the second transparent substrate 3, the liquid crystal 4 sandwiched between the first and second transparent substrates, and the liquid crystal 4. In order to bond the first transparent substrate 2 to the first transparent substrate 2, the sealing member 8, the reflector 5 disposed inside the second transparent substrate 3, the prism 7 disposed on the first transparent substrate 2, and the prism 7. The adhesive light diffusion layer 6 and the light source 30 functioning as a front light are provided. The adhesive light diffusing layer 6 is provided for expanding the viewing angle and increasing the contrast particularly when displaying using external light without using the front light.

  The light emitted from the light source 30 is configured to illuminate the entire reflective liquid crystal device 1 while reflecting between the reflector 5 and the prism 7. However, the light incident from the light source is scattered in the adhesive light diffusion layer 6 (for example, point P1 and point P2 in FIG. 1A), and the scattered light leaks from the reflective liquid crystal device 1. Since light leaks due to such light scattering, the light does not spread over the entire reflective liquid crystal device 1, and the amount of light decreases in a region away from the light source, resulting in a decrease in contrast. there were.

  As shown in FIG. 1B, a reflective liquid crystal device 1 ′ is a modification of the reflective liquid crystal device 1 shown in FIG. 1A, and includes a first transparent substrate 2, a second transparent substrate 3, The liquid crystal 4 sandwiched between the first and second transparent substrates, the seal member 8 for enclosing the liquid crystal 4, the reflector 5 disposed outside the second transparent substrate 3, and the reflector 5 It has an adhesive light diffusion layer 6 for bonding to a transparent substrate, a prism 7 disposed on the first transparent substrate 2, and a light source 30 that functions as a front light. The difference between the first (a) and FIG. 1 (b) is that the reflecting plate 5 and the adhesive light diffusion layer 6 are provided outside the second transparent substrate 3 in FIG. . The adhesive light diffusing layer 6 is provided for expanding the viewing angle and increasing the contrast particularly when displaying using external light without using the front light.

  The light emitted from the light source 30 is configured to illuminate the entire reflective liquid crystal device 1 while reflecting between the reflector 5 and the prism 7. However, the light incident from the light source is scattered in the adhesive light diffusion layer 6 (for example, the point P3 in FIG. 1B), and the scattered light leaks from the reflective liquid crystal device 1 ′. Since light leaks due to such light scattering, the light does not spread over the entire reflective liquid crystal device 1, and the amount of light decreases in a region away from the light source, resulting in a decrease in contrast. there were.

JP 2002-189108 A

  As described above, in the conventional reflection type liquid crystal display device exhibiting the specular reflection characteristic, the light diffusion layer is provided for widening the viewing angle and increasing the contrast when the front light is not used. When the front light is used, there is a problem that it causes a decrease in contrast.

Therefore, an object of the present invention is to provide a high-contrast display device.
Another object of the present invention is to provide a display device that solves the problems caused by using a light diffusion layer by using a light control means instead of the light diffusion layer.

  In order to solve the above-described problems, a display device according to the present invention includes a light source, a display unit including an electro-optic conversion element, and a light control including a plurality of reflecting surfaces that guide light incident from the light source into the display unit. And the reflecting surface diffuses the light emitted from the optical control means to the viewing side so that the haze ratio is 5 to 40%. In addition, the range of the haze ratio defines an optimum range in which the light control unit can improve visibility and function as a light guide member.

  Furthermore, the light control means is preferably a light guide prism.

  According to the present invention, light incident on the liquid crystal panel from the side is efficiently guided to the electro-optic conversion element by the light guide prism, and light emitted from the light guide prism to the viewing side of the liquid crystal panel is diffused well. As a result, a high-contrast display device can be provided.

  Hereinafter, a display device according to the present invention will be described with reference to the drawings.

  2 and 3 are diagrams showing a schematic configuration of the display device 10 according to the present invention.

  FIG. 2 shows a case where the LED light source 30 is used as a front light, and FIG. 3 shows a case where outside light is used.

  As shown in FIG. 2, the display device 10 includes a liquid crystal panel 20, an LED light source 30, a driving IC circuit 40 for the liquid crystal panel 20, and the like. The liquid crystal panel 20 includes a first transparent substrate 21, a second transparent substrate 22, a liquid crystal 23 sandwiched between the first and second transparent substrates, a sealing member 26 for enclosing the liquid crystal 23, and a first member. The first transparent electrode 29 disposed inside the transparent substrate 21, the light guide prism 24 disposed on the first transparent substrate 21, and the polarization disposed on the light guide prism 24 via the support member 31. A plate 27, a second transparent electrode 28 disposed inside the second transparent substrate 22, a reflecting plate 25 disposed outside the second transparent substrate 22, and the like.

  The first and second transparent electrodes 28 and 29 are arranged in a matrix inside the first and second transparent substrates 21 and 22, and the intersection of the first and second transparent electrodes 28 and 29 is the liquid crystal panel 20. Corresponds to the display pixels.

  As the liquid crystal 23, STN liquid crystal is used, but other liquid crystals such as CBLC (polymer network type polymer diffusion type liquid crystal), polymer dispersion type liquid crystal, OCB (Optical Compensated Birefringence) using nematic liquid crystal, IPS ( Other modes such as In Plane Switching (PVA), Patterned Vertical Alignment (PVA), SSFLC (Surface Stabilized Ferroelectric Crystal) using smectic liquid crystal, AFLC (Anit-FLC), PDLC, etc. can also be used. .

  The light guide prism 24 has a plurality of reflection surfaces, and has a function of spreading light incident on the liquid crystal panel 20 from the side surface to the entire liquid crystal panel 20 by the reflection surfaces. That is, the light incident from the side surface to the liquid crystal panel 20 from the LED light source 30 spreads throughout the display panel 20 while being repeatedly reflected between the light guide prism 24 and the reflection plate 25. However, since the light guide prism 24 itself uses a material that does not have the function of scattering light, the light incident on the light guide prism 24 from the LED light source 30 is at the angles of the plurality of reflection surfaces of the light guide prism 24. Total reflection is made accordingly. Therefore, unlike the light diffusion layer described in the related art, there is no problem that scattered light leaks to the outside of the display device 10 and the amount of light on the side far from the light source 30 of the liquid crystal panel 20 decreases. That is, as shown in FIG. 2, it is possible to display brightly without reducing the amount of light on the side closer to or far from the LED light source 30.

  As shown in FIG. 3, the external light B incident from the front direction enters the liquid crystal layer via the polarizing plate 27 and the light guide prism 24. The light guide prism 24 has a plurality of reflecting surfaces, and on the reflecting surface where the incident angle becomes large, the refraction angle becomes large and the traveling direction of the light is different from other parts (that is, the same effect as diffusion occurs). In this way, a large number of reflecting surfaces (in which the traveling direction of light is changed) are made by making the prism pitch fine, and the incident light is easily diffused in many different directions. Accordingly, since the external light B incident on the liquid crystal panel 20 is diffused in a number of different directions, it is reflected back to the viewing side by the reflecting plate 25 at different angles, thereby improving visibility such as an increase in viewing angle. Can be increased. In addition, the light that has entered the light guide prism 24 not only from the front direction but also from the front direction is diffused in many directions by the reflecting surface of the light guide prism 24. That is, in the display device 10 according to the present invention, the light emitted to the viewing side of the liquid crystal panel 20 can be favorably diffused to realize a high-contrast display device.

  Thus, in the display device 10 according to the present invention, the reflection surface (prism) of the light guide prism is made fine so that the external light B is easily diffused in many different directions. Unlike the reflective liquid crystal display device, it is not necessary to use a light diffusion layer. Therefore, in the display device 10 according to the present invention, when the front light is used, the light diffusion layer does not scatter the light from the front light and the contrast is not lowered.

  In order to allow the light guide prism 24 to satisfactorily spread the light from the light source as the light guide member over the entire liquid crystal panel 20 and to exhibit the function of diffusing outside light as the light diffusion member. It is preferable that the reflection surface of the light guide prism is formed at such a pitch that the haze value of the light emitted to the viewing side is 5% or more and 40% or less. When a light guide prism whose light haze value is less than 5% is used, it has the same function as the light diffusion layer in the conventional device (see FIG. 1). It disappears and visibility decreases. The upper limit of the haze ratio varies depending on the screen size, the liquid crystal material, the luminance of the light source, etc., but if a light guide prism is used in which the haze value of the light emitted to the viewing side is greater than 40%, the light is transmitted in the lateral direction. The function of propagating to the screen is reduced, and it becomes gradually difficult to uniformly illuminate the entire screen. For example, when an LED having a general light emission intensity is used in an STN liquid crystal panel of about 1 inch, it becomes difficult to uniformly illuminate the entire screen when the haze ratio is larger than 40%.

  FIG. 4 is a graph showing an example of the relationship between the pitch of the light guide prism and the haze ratio, and FIG. 5 is a diagram showing an example of a cross section of the light guide prism.

  FIG. 5A is a diagram showing a cross-section of the light guide prism 24 used in the above-described embodiment. The pitch s1 of the triangular microprism 51 having the reflecting surface 50 is 50 μm, the angle θ1 is 1 degree, and the angle θ2 is set to 46 degrees. FIG. 5B shows another light guide prism 24 ′ that can be used in the present invention. The triangular microprism 53 having the reflecting surface 52 has a pitch s 2 of 25 μm, an angle θ 1 of 1 degree, and an angle θ 2 of It is set to 46 degrees. The substrate thickness w of the light guide prism shown in FIG. 5 was both set to 10 μm. Here, the microprism 51 of the light guide prism 24 shown in FIG. 5A and the microprism 53 shown in FIG. 5B have similar shapes.

  FIG. 4 is a diagram in which the haze ratio in each case is measured by varying the pitch of micro prisms similar in shape to the micro prism 51 as shown in FIG. Since the pitch s1 of the minute prisms 51 in the light guide prism 24 shown in FIG. 5A is 50 μm, the haze ratio in that case is about 10% as shown in FIG. In addition, since the pitch s2 of the micro prisms 53 in the light guide prism 24 ′ shown in FIG. 5B is 25 μm, the haze ratio in that case is about 20% as shown in FIG. As shown in FIG. 4, the light guide prism having an appropriate haze ratio (5% to 40%) can be manufactured by changing the pitch of the micro prisms having the reflecting surface of the light guide prism.

  Note that the relationship between the pitch and the haze ratio shown in FIG. 4 and the shape of the light guide prism shown in FIG. 5 are merely examples, and the present invention is not limited to this. That is, the relationship between the pitch and the haze ratio varies depending on the material of the light guide prism as shown in FIG. 5 and the cross-sectional shape of the microprism, so that the light guide prism to be adopted has an optimum haze ratio. What is necessary is just to set suitably the cross-sectional shape of a raw material or a microprism.

  In the above embodiment, the display device 10 using the liquid crystal panel 20 using PNCL has been described. However, a display unit having an electro-optic conversion element such as a liquid crystal element in another mode or a micro electro mechanical system (MEMS) element is provided. It can also be used in the present invention.

  In the above embodiment, the light guide prism is used as the light control means for guiding light from the light source well and diffusing the light from outside light. However, other optical elements are used in the present invention. It can also be used.

It is a figure which shows schematic structure of the conventional liquid crystal display device. It is a figure which shows schematic structure of the display apparatus 10 which concerns on this invention. It is a figure which shows schematic structure of the display apparatus 10 which concerns on this invention. It is a figure which shows an example of the relationship between the pitch in a light guide prism, and a haze rate. It is a figure which shows an example of the cross-sectional shape of a light guide prism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 21, 22 Transparent substrate 23 Liquid crystal 24, 24 'Light guide prism 25 Reflector 30 LED light source 50, 52 Reflecting surface 51, 53 Micro prism

Claims (2)

In the display device,
A light source;
A display unit having an electro-optic conversion element;
A light control means having a plurality of reflecting surfaces for guiding the light incident from the light source into the display unit;
The said reflecting surface diffuses the light radiate | emitted to the visual recognition side from the said optical control means so that a haze rate may be 5 to 40%.   The display device according to claim 1, wherein the light control unit is a light guide prism.

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