JP4606135B2 - Liquid crystal display device - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device capable of efficiently supplying light to an observer.

  2. Description of the Related Art Conventionally, a surface light emitting device that illuminates a liquid crystal display panel, for example, a front light, is known as an illumination unit of a display device, mainly a liquid crystal display device. Conventional frontlights are usually mainly composed of a light source and a light guide plate that emits light from the light source to a liquid crystal display panel.

  FIG. 5 is a diagram showing a configuration of a conventional liquid crystal display device. The liquid crystal display device shown in FIG. 5 includes a liquid crystal display panel 4, a front light disposed thereon, and a cover 5 disposed on a light guide plate of the front light. The front light has a light guide plate 1. The light guide plate 1 has a flat plate shape, has a pair of main surfaces facing each other and a pair of end surfaces facing each other, and a plurality of prisms 1a on one main surface (main surface close to an observer). Is formed. A bar light guide 3 is disposed in the vicinity of one end surface of the pair of end surfaces, and a light source 2 is disposed at one end of the bar light guide 3.

  In this front light, light from the light source 2 enters from the end face of the light guide plate 1 and propagates inside the light guide plate 1. The light reflected by the prism 1a in the light guide plate 1 is directed toward the liquid crystal display panel 4 as shown by the arrow in the figure, reflected by the liquid crystal display panel 4, and transmitted through the light guide plate 1 and the cover 5. Directed toward the viewer.

JP-A-11-109347

  However, in the light guide plate 1 shown in FIG. 5, the light is reflected by the prism 1a and directed toward the liquid crystal display panel 4 side. Thus, when light is reflected by the prism 1a having the shape as shown in FIG. 5, light inevitably leaks from the main surface having the prism 1a. The light reflected by the liquid crystal display panel 4 passes through the light guide plate 1 and then through the cover 5. At this time, a part of the light transmitted through the light guide plate 1 is reflected by the cover 5 as indicated by the arrow in FIG. Thus, the light guide plate having the configuration shown in FIG. 5 cannot efficiently supply light to the observer.

  The present invention has been made in view of such a point, and an object thereof is to provide a liquid crystal display device capable of efficiently supplying light to an observer.

The liquid crystal display device of the present invention is disposed in the vicinity of the end surface of the light guide plate, and a light guide plate having a pair of main surfaces facing each other, an end surface that receives light from a light source, and a light output surface that emits light . A light source, a liquid crystal display panel disposed to face one main surface of the pair of main surfaces of the light guide plate, and a refractive index adjustment layer sandwiched between the liquid crystal display panel and the light guide plate One of the pair of principal surfaces of the light guide plate facing the liquid crystal display panel has a plurality of prisms, and each of the prisms is relative to the end surface. relatively gently with sloping first surface, relatively steep inclined with respect to the horizontal reference plane of the relatively far rather the light emitting surface from the end surface with respect to the horizontal reference plane of the near rather the light exit surface a second surface which is positioned between the first surface and the second surface Is composed of a flat third surface relative to the horizontal reference plane of the serial light emitting surface, below 5 ° angle is 0.5 ° or more between the first surface and the horizontal reference plane, the first The angle formed between the second surface and the third surface is 40 ° or more and 60 ° or less.

  According to this configuration, light leaking from the main surface having the prism can be suppressed as much as possible, and light can be efficiently directed to the liquid crystal display panel. In addition, since the antireflection effect is exhibited by the presence of the refractive index adjustment layer, reflection is performed for both the light directed from the third surface toward the liquid crystal display panel and the light directed from the liquid crystal display panel toward the third surface. Can be suppressed. Thereby, the contrast can be improved.

  According to this configuration, since the light emitted from the main surface that emits light is directly supplied to the liquid crystal display panel, the light can be supplied from the light guide plate to the liquid crystal display panel without loss of light quantity. In addition, since the reflectance on the third surface is kept low, the visibility of the observer can be improved. The main surface having the prism is opposed to the liquid crystal display panel, and the main surface opposite to the main surface having the prism of the light guide plate is a flat surface. For this reason, a cover for protecting the prism of the light guide plate is not necessary, and an optical element can be easily arranged on the flat main surface of the light guide plate as necessary. Further, even when an external force is applied to the liquid crystal display device, the refractive index adjustment layer absorbs the external force, so that it is possible to reduce the load on the liquid crystal display device.

In the liquid crystal display device of the present invention, the refractive index adjustment layer is interposed between the liquid crystal display panel and the third surface, and the first surface, the second surface, and the refraction of the prisms adjacent to each other. it is preferred to have the air layer between the rate adjustment layer.

  According to this configuration, the light propagating through the light guide plate is emitted from only the third surface of the prism to the liquid crystal display panel via the refractive index adjustment layer. For this reason, the light propagating through the light guide plate can be emitted to the liquid crystal display panel, and the light can be propagated to a position farther from the light source in the light guide plate.

  In the liquid crystal display device of the present invention, the refractive index adjustment layer is made of a material having a refractive index difference between the material constituting the light guide plate and / or the material constituting the liquid crystal display panel of 0.1 or less. It is preferable that

  In the liquid crystal display device of the present invention, the difference between the refractive index of the material constituting the light guide plate and the refractive index of the refractive index adjustment layer is the difference between the refractive index of the material constituting the light guide plate and the refractive index of air. The difference between the refractive index of the material constituting the liquid crystal display panel and the refractive index of the refractive index adjusting layer is smaller than the difference between the refractive index of the material constituting the liquid crystal display panel and the air. It is preferable that the absolute value is smaller than the difference between the refractive index and the refractive index.

  According to these configurations, light can be emitted to the liquid crystal display panel in a state substantially perpendicular to the surface of the liquid crystal display panel 20 without being largely refracted by the third surface of the light guide plate.

In the liquid crystal display device of the present invention, the angle formed between the second surface and the third surface is such that light incident from the end surface is reflected by the second surface, and the reflected light is reflected by the first surface. The angle is preferably such that the light is emitted from the surface 3 to the outside. Thereby, the light guide plate can reflect the light incident from the light source and propagating through the inside of the light guide by the second surface, and direct the reflected light to the third surface.

  According to the present invention, a light guide plate having a pair of main surfaces facing each other and an end surface for receiving light from a light source, a light source disposed in the vicinity of the end surface of the light guide plate, and the prism of the light guide plate A liquid crystal display panel disposed so as to face the main surface, and a refractive index adjustment layer sandwiched between the liquid crystal display panel and the light guide plate, wherein the light guide plate includes the pair of main surfaces. One main surface of the surface has a plurality of prisms, and each of the prisms has a relatively gentle first surface relatively near to the end surface and a relatively steep surface relatively far from the end surface. An angle formed between the second surface and the third surface, the second surface and a third surface located between the first surface and the second surface. Because of the acute angle, light directed from the third surface toward the liquid crystal display panel and directed from the liquid crystal display panel toward the third surface Reflection can be suppressed for both light, thereby improving the contrast.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a perspective view showing a configuration of a liquid crystal display device including a front light according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the liquid crystal display device shown in FIG. The liquid crystal display device shown in FIG. 1 mainly includes a front light 10 which is a surface light emitting device and a liquid crystal display panel 20 disposed on the back side (the lower surface side in FIG. 1).

  As shown in FIG. 1, the front light 10 includes a substantially flat transparent light guide plate 12 having a pair of opposed main surfaces 12b and 12c, and a long bar disposed along the end surface 12a. The light guide body 13 and the LED 13a which is a light emitting element disposed in the vicinity of the end face of the bar light guide body 13 are mainly configured. That is, in the front light 10 according to the present embodiment, the LED 13a and the bar light guide 13 constitute a light source, and the end surface 12a of the light guide plate 12 constitutes the light incident surface of the light guide plate.

  As shown in FIG. 2, the light guide plate 12 of the front light 10 is disposed on the display area of the liquid crystal display panel 20, and light from the LEDs 13 a is emitted from the light emission surface 12 b to the liquid crystal display panel 20. The light guide plate 12 is made of a transparent resin material such as an acrylic resin, a norbornene resin, a cyclic polyolefin resin, or a polycarbonate resin.

  As shown in FIG. 2, a plurality of prisms 14 are formed on the main surface of the light guide plate 12 on the liquid crystal display panel 20 side (the lower main surface in FIG. 2, the light emitting surface) 12 b. The individual prisms 14 include a relatively gentle first surface (slow slope) relatively close to the end surface 12a, a relatively steep second surface (steep slope) relatively far from the end surface 12a, and a first A third surface (flat surface) located between the surface and the second surface, and an angle formed between the second surface and the third surface is an acute angle. Accordingly, the plurality of prisms 14 are positioned in stripes parallel to each other as shown in FIG. 1, and have a substantially saw-toothed cross section as shown in FIG.

  The liquid crystal display panel 20 includes an upper substrate 21 and a lower substrate 22 that are arranged to face each other, and a liquid crystal layer 23 is sandwiched between the upper substrate 21 and the lower substrate 22. The liquid crystal layer 23 is sealed with a sealing material 24 provided along the inner peripheral edge of the upper substrate 21 and the lower substrate 22. A liquid crystal control layer 26 is formed on the main surface on the inner side (lower substrate 22 side) of the upper substrate 21, and the front light 10 is formed on the main surface on the inner side (upper substrate 21 side) of the lower substrate 22. A reflective layer 27 for reflecting light and external light is formed. A liquid crystal control layer 28 is formed on the reflective layer 27.

  The liquid crystal control layers 26 and 28 include an electrode for driving and controlling the liquid crystal layer 23, an alignment film, a semiconductor element for switching the electrode, and the like. Further, a color filter for color display is included as necessary. The reflective layer 27 includes a reflective thin film made of a metal such as aluminum or silver having high reflectivity in order to reflect external light incident on the liquid crystal display panel 20 and light of the front light 10. The reflective layer 27 preferably includes light scattering means in order to prevent the reflected light from becoming strong in a specific direction and reducing the visibility of the liquid crystal display device. As the light scattering means, a reflection thin film formed in a concavo-convex shape, a scattering film in which beads made of a resin material having a refractive index different from that of the resin matrix material are dispersed in a resin matrix, or the like is used. be able to.

  In the present embodiment, the liquid crystal display panel 20 is a reflective liquid crystal display panel. In FIG. 1, a rectangular area 20D indicated by a broken line of the liquid crystal display panel 20 is a display area. A large number of pixels are formed in a matrix in the display region 20D. The light guide plate 12 of the front light 10 is disposed on the display region 20D via the refractive index adjustment layer 15. At this time, the front light 10 is disposed such that the light emitting surface 12 b (the surface having the prism 14) of the light guide plate 12 faces the liquid crystal display panel 20. Therefore, the refractive index adjustment layer 15 is interposed between the liquid crystal display panel 20 and the flat surface (third surface) of the prism 14.

FIG. 3 is a partial cross-sectional view for explaining a light guide state of the front light shown in FIG. As shown in FIG. 3, the prism 14 formed on the light emitting surface 12b is configured by a pair of inclined surfaces formed to be inclined with respect to the horizontal reference plane z of the light emitting surface 12b as described above. There are a gentle slope 14a relatively close to the end face 12a, a steep slope 14b relatively far from the end face 12a, and a flat face 14c located between the gentle slope 14a and the steep slope 14b, and the steep slope 14b and the flat face 14c. The angle (tilt angle) θ ₂ formed between the _two is an acute angle. Further, the gentle slope 14a is formed at an inclination angle θ ₁ with respect to the horizontal reference plane z of the light exit surface 12b.

In the present invention, the angle θ ₂ is preferably an angle at which light incident from the end surface 12a is reflected by the steep slope 14b and the reflected light is emitted from the flat surface 14c to the outside. For example, the inclination angle θ ₂ of the steep slope 14b is preferably in the range of 40 ° to 60 °. In addition, the inclination angle θ ₁ of the gentle slope 14a is preferably in the range of 0.5 ° to 5 ° with respect to the horizontal reference plane z. Further, the pitch P of the prisms 14 (the interval between the apexes X or the apex Y of the prisms 14) is constant within the light exit surface 12b of the light guide plate, and the height h of the prisms 14 (the horizontal reference plane z and the prisms 14). The distance from the top Y of the light source) changes so as to increase with distance from the light source in the light exit surface 12b. Note that the pitch P of the prisms 14 does not necessarily have to be constant within the light emitting surface 12b, and may be changed as appropriate within the light emitting surface 12b. Further, the height h of the prism 14 does not necessarily change in the light emitting surface 12b, and may be constant in the light emitting surface 12b. Further, the inclination angles θ ₁ and θ ₂ of the respective prisms 14 may be appropriately changed within the light exit surface 12b.

  In addition, in the Japanese Patent Application No. 2004-150286 filed by the present applicant, the present inventors verified that the amount of illumination of the front light 10 can be increased by optimizing the inclination angle of the steep slope 14b as described above. ing. All this content is included here.

  In the present invention, as shown in FIG. 4, the refractive index adjustment layer 15 is sandwiched between the light guide plate 12 and the upper substrate 21 of the liquid crystal display panel 20. More specifically, the refractive index adjusting layer 15 is interposed between the flat surface 14c of the prism 14 on the light emitting surface 12b and the upper substrate 21. Therefore, the air layer 16 composed of the gentle slope 14a and the steep slope 14b basically has no refractive index adjustment layer 15. For this reason, light is emitted to the liquid crystal display panel 20 through the refractive index adjustment layer 15 only from the flat surface 14c. In the region of the air layer 16, since there is an interface between the gentle slope 14 a and the air layer 16 or an interface between the steep slope 14 b and the air layer 16, light propagating through the light guide plate 12 is emitted from the light guide plate 12. Therefore, it is possible to propagate light to a position farther from the light source in the light guide plate 12. As described above, according to this configuration, since the prism 14 has the flat surface 14 c and the air layer 16, the light emission surface 12 b can be formed, and the light is refracted between the liquid crystal display panel 20 and the light guide plate 12. Even if the rate adjustment layer 15 is interposed, light can be propagated to a position farther from the light source in the light guide plate 12.

  Here, although there is no restriction | limiting in particular as a material which comprises the refractive index adjustment layer 15, The material which comprises the light-guide plate 12, for example, the transparent resin material mentioned above, and / or the material which comprises a liquid crystal display panel, for example, a polarizing plate, for example A material having a refractive index difference of 0.1 or less is preferable. Examples of such materials include silicone resins and acrylic resins. According to such a material, light can be emitted to the liquid crystal display panel 20 in a state substantially perpendicular to the surface of the upper substrate 21 without being largely refracted by the flat surface 14c of the light guide plate 12.

  In addition, regarding the relationship between the refractive indexes, the difference between the refractive index of the material constituting the light guide plate 12 and the refractive index of the refractive index adjustment layer 15 is the difference between the refractive index of the material constituting the light guide plate 12 and the refractive index of air. The difference between the refractive index of the material constituting the liquid crystal display panel 20 and the refractive index of the refractive index adjustment layer 15 is smaller than the difference between the refractive index of the material constituting the liquid crystal display panel 20 and air. It is preferable that the absolute value is smaller than the difference between the refractive index and the refractive index. In addition, as a material which comprises a liquid crystal display panel, the material of optical elements, such as a polarizing plate arrange | positioned on the glass substrate of a liquid crystal display panel, is included.

  The thickness of the refractive index adjusting layer 15 is preferably 0.2 mm to 4 mm in consideration of impact resistance of the product. Further, the method for forming the refractive index adjustment layer 15 depends on the material constituting the refractive index adjustment layer 15. For example, a filler is applied and printed on the liquid crystal display panel 20, and the light guide plate 12 is disposed thereon. Examples thereof include a method of curing the filler, a method of sandwiching a sheet or film composed of the filler between the liquid crystal display panel 20 and the light guide plate 12, and heating or pressurizing.

  In the liquid crystal display device having the above configuration, an observer can visually recognize the display on the liquid crystal display panel 20 through the light guide plate 12. Further, in a dark place where outside light cannot be obtained, the LED 13a of the front light 10 is turned on. The light emitted from the LED 13 a is introduced into the light guide plate 12 from the end surface 12 a of the light guide plate 12 through the bar light guide 13, propagates through the light guide plate 12, and the light is transmitted through the light guide plate 12. The light exits from the light exit surface (lower surface in the drawing) 12 b toward the liquid crystal display panel 20. By illuminating the liquid crystal display panel 20 in this way, an observer can visually recognize the display on the liquid crystal display panel 20 through the light guide plate 12 even in a dark place.

  When the LED 13a of the front light 10 is turned on, specifically, as shown in FIG. 4, the light (arrow A) propagated through the light guide plate 12 is reflected by the steep slope 14b, and the reflected light (arrow B) is reflected. It faces the flat surface 14c. The light indicated by the arrow A is incident on the steep slope 14b at an angle exceeding 45 ° with respect to the normal line (dashed line) of the steep slope 14b. This makes it possible to prevent light (arrow A) incident on the steep slope 14b from transmitting through the steep slope 14b as much as possible. As a result, the amount of light reflected by the steep slope 14b increases, and the brightness of the front light 10 is improved. The light reflected by the steep slope 14b reaches the flat surface 14c at a substantially right angle to the flat surface 14c. Since the flat surface 14 c is in contact with the refractive index adjustment layer 15, the light reaching the flat surface 14 c is incident on the upper substrate 21 of the liquid crystal display panel 20 through the refractive index adjustment layer 15.

  Thus, the front light 10 of the present embodiment can efficiently direct light to the liquid crystal display panel 20, and can efficiently supply light to the observer. In particular, in the light guide plate 12 in the front light 10 of the present embodiment, the light emission surface 12b having the prism 14 faces the liquid crystal display panel 20, and the light emitted from the light emission surface 12b is directly applied to the liquid crystal display panel as described above. Therefore, light can be supplied from the light guide plate 12 to the liquid crystal display panel 20 without loss of light quantity.

  The light propagating through the light guide plate 12 is emitted from only the flat surface 14 c of the prism 14 to the liquid crystal display panel 20 through the refractive index adjustment layer 15, and in the region of the air layer 16, Since there is an interface between the air layer 16 or an interface between the steep slope 14 b and the air layer 16, light propagating through the light guide plate 12 is not emitted from the light guide plate 12. For this reason, the light propagating through the light guide plate 12 can be emitted to the liquid crystal display panel 20, and the light can be propagated to a position farther from the light source in the light guide plate 12.

  In addition, since the antireflection effect is exhibited by the presence of the refractive index adjustment layer 15, both the light directed from the flat surface 14 c toward the liquid crystal display panel 20 and the light directed from the liquid crystal display panel 20 toward the flat surface 14 c are reflected. Can be suppressed. Thereby, the contrast can be improved.

  Further, the light emitting surface 12b having the prism 14 faces the liquid crystal display panel 20, and the main surface 12c opposite to the light emitting surface 12b having the prism 14 of the light guide plate 12 is a flat surface. Therefore, a cover for protecting the prism 14 of the light guide plate 12 as shown in FIG. 5 is not necessary, and an optical element can be easily disposed on the main surface 12c of the light guide plate 12 as necessary. . Further, even when an external force is applied to the front light 10, the refractive index adjustment layer 15 absorbs the external force, so that the load on the liquid crystal display device can be reduced.

Next, examples performed for clarifying the effects of the present invention will be described.
A light guide plate substrate was prepared by injection molding using a norbornene-based heat-resistant transparent resin, Arton (trade name, manufactured by JSR) as a transparent resin material. As shown in FIG. 2, the obtained light guide plate substrate has a plurality of prisms 14 on one main surface (light emitting surface) 12b, and the other main surface 12c is a flat surface. The plurality of prisms 14 are positioned between a relatively gentle gentle slope 14a that is relatively close to the end face 12a, a relatively steep slope 14b that is relatively far from the end face 12a, and the gentle slope and the steep slope. And an angle formed between the steep slope 14b and the flat surface 14c is an acute angle. Arton has a refractive index of 1.52.

  Next, after providing a triacetyl cellulose layer having a refractive index of 1.49 as a polarizing plate on the surface of the liquid crystal display panel, the refractive index is adjusted between the light exit surface of the obtained light guide plate substrate and the liquid crystal display panel. A silicone resin layer having a refractive index of 1.42 was interposed as a layer, and a light guide plate base material was disposed on the liquid crystal display panel as shown in FIG. Therefore, it can be seen that the silicone resin is a material having a refractive index difference of 0.1 or less between the material constituting the light guide plate (Arton) and the material constituting the liquid crystal display panel (triacetyl cellulose).

Further, in the same manner as described above, a light guide plate substrate having the configuration shown in FIG. 2 was produced. Liquid crystal display panel After a triacetyl cellulose layer having a refractive index of 1.49 is provided as a polarizing plate on the surface of the liquid crystal display panel, an ultraviolet curable resin having a refractive index of 1.49, Photolek (Sekisui Fine Chemical) is formed on the triacetyl cellulose layer. Co., Ltd., trade name) was applied at a thickness of 3 μm by spin coating. And the ultraviolet curable resin was hardened by irradiating the ultraviolet-ray of irradiation energy 4.5J / cm < ² > from the flat surface 12c side of a light-guide plate base material. A silicon resin layer having a refractive index of 1.42 is interposed as a refractive index adjusting layer between the light exit surface of the obtained light guide plate base material and the liquid crystal display panel, so that the liquid crystal display panel is mounted as shown in FIG. A liquid crystal display device of Example 2 was configured by disposing a light guide plate substrate. Therefore, it can be seen that the silicone resin is a material having a refractive index difference of 0.1 or less between the material constituting the light guide plate (Arton) and the material constituting the liquid crystal display panel (ultraviolet curable resin).

Further, in the same manner as described above, a light guide plate base material having the structure shown in FIG. 2 is manufactured, and SiO ₂ and TiO are used as antireflection materials by vapor deposition on the light emission surface (prism formation surface) of the light guide plate base material. ₂ was deposited to a thickness of 0.5 μm to form an antireflection film. The obtained light guide plate substrate was placed on a liquid crystal display panel as shown in FIG. 2 to constitute a liquid crystal display device of Comparative Example 1.

  Further, in the same manner as described above, a light guide plate substrate having the configuration shown in FIG. 5 was produced. Next, after providing a triacetyl cellulose layer having a refractive index of 1.49 as a polarizing plate on the surface of the liquid crystal display panel, the light emitting surface (surface opposite to the prism forming surface) of the obtained light guide plate substrate and the liquid crystal In the comparative example 2, a silicone resin layer having a refractive index of 1.42 is interposed as a refractive index adjusting layer between the display panel and a light guide plate substrate is disposed on the liquid crystal display panel as shown in FIG. A liquid crystal display device was constructed.

  In these liquid crystal display devices, lighting was turned on to measure luminance, luminance uniformity, and display contrast. The brightness is obtained from the brightness at the center of the liquid crystal display panel when displaying white, and the brightness uniformity is determined by the ratio between the minimum brightness and the maximum brightness of 25 points in the liquid crystal display panel surface in the white display of the liquid crystal display panel The obtained contrast was obtained by measuring the luminance of each of the white display and the black display of the liquid crystal display panel and calculating the luminance ratio. In addition, as a luminance meter, BM-5 (Topcon company make, brand name) was used. The results are shown in Table 1 below.

  As can be seen from Table 1, the liquid crystal display devices (Examples 1 and 2) of the present invention are substantially equivalent in luminance and luminance uniformity to Comparative Example 1 in which an antireflection film is formed by vapor deposition, and the contrast is Comparative Example 1. Was better than. Further, the liquid crystal display devices (Examples 1 and 2) of the present invention are considerably superior in luminance and luminance uniformity as compared with the comparative example 2 of the conventional configuration. This is considered to be because light is emitted to the liquid crystal display panel without sufficiently propagating through the light guide plate to the end away from the light source in the configuration of Comparative Example 2.

  As described above, the liquid crystal display device of the present invention is excellent in luminance, luminance uniformity, and contrast, and further, an antireflection structure is not required on the liquid crystal display panel side or the light guide plate side, so that the cost can be reduced. It becomes.

  The present invention is not limited to the embodiment described above, and can be implemented with various modifications. For example, in the said embodiment, optical components like a light-guide plate are not limited to a plate-shaped body, You may implement by changing into a film-form body and a sheet-like body suitably. Moreover, in the said embodiment, although the case where the light source is comprised by LED and bar light guide which are light emitting elements is demonstrated, in this invention, a light source is other than LED and bar light guide It may consist of. Moreover, although the case where the liquid crystal display device is a reflective liquid crystal display device has been described in the above embodiment, the present invention can be similarly applied to a transflective liquid crystal display device. In addition, various modifications can be made without departing from the scope of the object of the present invention.

It is a perspective view which shows the structure of the liquid crystal display device which concerns on one embodiment of this invention. It is sectional drawing of the liquid crystal display device shown in FIG. It is a fragmentary sectional view for demonstrating the light guide state of the front light in the liquid crystal display device shown in FIG. It is an enlarged view which shows the structure of the prism of the light-guide plate shown in FIG. It is a figure which shows the structure of the conventional liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Front light 12 Light-guide plate 12a End surface 12b Light-emitting surface 12c Main surface 13 Bar light guide 13a LED
14 prism 14a gentle slope 14b steep slope 14c flat surface 15 refractive index adjustment layer 16 air layer 20 liquid crystal display panel 21 upper substrate 22 lower substrate 23 liquid crystal layer 24 sealant 26, 28 liquid crystal control layer 27 reflective layer

Claims (6)

A light guide plate having a pair of main surfaces opposed to each other, an end surface that receives light from the light source, and a light output surface that emits light, a light source disposed in the vicinity of the end surface of the light guide plate, and the light guide plate A liquid crystal display panel disposed so as to face one main surface of the pair of main surfaces, and a refractive index adjustment layer sandwiched between the liquid crystal display panel and the light guide plate,
One main surface facing the liquid crystal display panel of the pair of main surfaces of the light guide plate has a plurality of prisms, each of the prism, relatively near rather the light emitted from the end face a first surface which is relatively gently inclined relative to the horizontal reference plane of the surface, a second surface which is relatively steeply inclined to the horizontal reference plane of the relatively far rather the light emitting surface from the end face and A third surface that is located between the first surface and the second surface and is flat with respect to a horizontal reference surface of the light exit surface , the first surface and the horizontal reference surface The angle between the second surface and the third surface is 40 ° to 60 °, and the liquid crystal display device is characterized in that the angle between the second surface and the third surface is 40 ° to 60 °. .   The refractive index adjustment layer is interposed between the liquid crystal display panel and the third surface, and an air layer is formed between the first surface and the second surface of the prisms adjacent to each other and the refractive index adjustment layer. The liquid crystal display device according to claim 1, comprising:   The refractive index adjusting layer is made of a material having a refractive index difference of 0.1 or less between a material constituting the light guide plate and / or a material constituting the liquid crystal display panel. Item 3. A liquid crystal display device according to item 1 or 2.   The difference between the refractive index of the material constituting the light guide plate and the refractive index of the refractive index adjustment layer is an absolute value than the difference between the refractive index of the material constituting the light guide plate and the refractive index of air. The difference between the refractive index of the material constituting the liquid crystal display panel and the refractive index of the refractive index adjustment layer is smaller than the difference between the refractive index of the material constituting the liquid crystal display panel and the refractive index of air. 4. The liquid crystal display device according to claim 1, wherein the absolute value of the liquid crystal display device is also small.   The angle formed between the second surface and the third surface is such that light incident from the end surface is reflected by the second surface and the reflected light is emitted from the third surface to the outside. The liquid crystal display device according to claim 1, wherein the liquid crystal display device has a wide angle.   The said light guide plate reflects the light which injects from the said light source, and propagates the inside of the said light guide with the said 2nd surface, and directs reflected light to the said 3rd surface. The liquid crystal display device according to claim 5.

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