JP5184240B2 - Display device - Google Patents

Description

  The present invention relates to a display device used for portable information devices such as mobile phones and mobile computers, and large-sized image devices such as desktop computers and home televisions.

  2. Description of the Related Art Conventionally, as color image display devices used for portable information devices such as mobile phones and mobile computers, liquid crystal display devices that are small and thin and have low power consumption have been widely used. Also, high-definition and low-power-consumption liquid crystal display devices are rapidly spreading in large image devices such as desktop computers and home televisions.

  In general, a liquid crystal display device includes a backlight as a light source. As a backlight, an edge light type illumination device is known in which light from a light source is incident from a side surface of a light guide and is emitted from an upper surface of a light guide plate (hereinafter referred to as an emission surface). As the light source, a line light source such as a cold cathode tube or a point light source such as a light emitting diode (LED) is used. On the surface opposite to the light exit surface of the light guide plate (hereinafter referred to as an opposing surface), there are a large number of grooves and dots. A pattern is formed. In addition, a diffusion pattern having an effect of diffusing light is often formed on the exit surface. A prism is formed on the light incident surface of the light guide (that is, the surface that faces the light source and the light from the light source enters), and has a function of diffusing the light from the point light source into a surface light source. . As a material for the light guide plate, a transparent resin such as polycarbonate (PC) or acrylic (PMMA) having a higher refractive index than air is used. In addition, a configuration in which a diffusion sheet and a prism sheet are arranged on the light exit surface side of the light guide is the mainstream. Further, a reflection sheet is disposed below the light guide.

In addition, an edge light type illumination device that uses a line light source such as a cold cathode tube instead of a point light source is also known (see, for example, Patent Document 1). A black matrix, TFT wiring, and the like exist inside the color TFT liquid crystal. Therefore, the aperture ratio cannot be 100% and is about 60 to 70%. A low-temperature polysilicon liquid crystal has a high aperture ratio, but it is still about 80%.
Japanese Patent Laid-Open No. 9-292531 (FIGS. 1 and 2)

  In the configuration of the conventional backlight, the light hitting the opening of the liquid crystal panel can be emitted, but the light hitting the other wiring of the TFT and the black matrix is absorbed or scattered. As a result, a liquid crystal display device with very low utilization efficiency of light from the backlight is obtained.

  In order to solve the above problems, a display device of the present invention includes a light guide plate having a light source, an incident surface on which light from the light source is incident, an exit surface that emits illumination light, and a facing surface opposite to the exit surface. A display device including a display element on an output surface of an illumination device including the display device, wherein an output region is provided on an opposite surface of the light guide plate corresponding to an opening of the display element (a portion through which illumination light passes). It was set as the structure where illumination light is irradiated only to the opening part of an element.

  In addition, a plurality of prisms are arranged on the facing surface of the light guide plate only in a region facing the opening of the display element.

  Here, the shape of the prism may be a polyhedron having four or more surfaces or a dome shape. In addition, the size of the prism is arranged so as to increase as the distance from the light source increases. Alternatively, the number of prisms is arranged to decrease as the distance from the light source increases.

  In addition, the angle of the reflecting surface of the prism was set to 40 ° to 50 ° with respect to a surface parallel to the traveling direction of light from the light source. Alternatively, the prism has a convex shape and is arranged so as to protrude to the lower part of the opposing surface of the light guide plate. The prism is arranged perpendicular to the straight line where the reflecting surface of the prism connects the light source and the prism pattern.

  Further, a diffusion layer is arranged on the display surface of the display element. Furthermore, a reflective layer having a transmissive region formed in a portion facing the opening of the display element is provided between the light guide plate and the display element.

  According to the present invention, the entire exit surface of the light guide does not shine, but when the display elements are stacked, the light exits only from the area that overlaps the opening of the display element. did it. With the configuration of the present invention, a display device with high light utilization efficiency of a light source can be realized.

  The display device of the present invention is a display device in which a display element is disposed on a backlight, and an emission region is provided in the backlight in accordance with the opening of the display element, and only the opening is formed by light emitted from the emission region. It was set as the structure irradiated. The backlight has an incident surface on which light from the light source is incident, an emission surface from which illumination light is emitted, and a facing surface opposite to the emission surface. On the emission surface, an emission region corresponding to the opening of the display element and a non-emission region that does not emit light are formed. That is, the entire exit surface of the light guide is not illuminated, and illumination light is emitted only from the exit area of the exit surface. When the openings of the display elements are arranged in a matrix, this emission region is also arranged in a matrix. And between these emission area | regions, it is a non-emission area | region which does not radiate | emit (pass) light.

  As described above, in order to emit illumination light only from the emission region, a plurality of prisms are arranged only in the area corresponding to the opening of the display element on the opposite surface opposite to the emission surface of the light guide plate. . That is, a plurality of prisms are formed in a region corresponding to the emission region on the opposing surface of the light guide plate. At this time, the area where the prism is formed, the exit area of the exit surface, and the size of the opening of the display element may be the same, the thickness of the light guide plate, the thickness of the display element, the arrangement relationship, the individual shape of the prism, etc. It may be optimized by changing the size in consideration of various factors.

  Further, the prisms are arranged so that the line where the reflecting surface of the prism intersects with the opposing surface of the light guide plate is perpendicular to the straight line connecting the light source and the prism pattern.

  In addition, a reflective layer having a transmission region is provided between the light guide plate and the display element at a portion corresponding to the opening of the display element. As a result, even if there is light reaching other than the opening, the light is reflected by the reflective layer toward the light guide plate and is incident on the light guide plate again. That is, even if there is light that is irradiated outside the opening, this light is re-entered into the light guide plate without being absorbed by the display element, and as a result, the light utilization efficiency is improved. .

  Hereinafter, the display device of the present invention will be specifically described with reference to the drawings, taking a display device using a liquid crystal panel as a display element as an example.

  The display device of this embodiment will be described with reference to FIGS. 1, 2, 7, and 8. FIG. FIG. 1 is a cross-sectional view of the display device of this embodiment. As shown in the drawing, the liquid crystal panel 13 has a configuration in which a liquid crystal layer 8 is sealed in a gap between a glass substrate 5a and a counter substrate 5b. A lower ITO 7a and a TFT area 6 are formed on the glass substrate 5a, and a lower alignment film 9a is further formed thereon. On the other hand, a red color filter 10R, a green color filter 10G, and a blue color filter 10B are formed on the opposing substrate 5b. A black matrix 11 is formed between these color filters. The formation region of the red color filter 10R, the green color filter 10G, the blue color filter 10B, and the black matrix 11 is flattened by the flattening layer 14. On the surface of the planarization layer 14, an upper ITO 7b for forming a pixel electrode is provided so as to face the lower ITO 7a. An upper alignment film 9b is also formed on the upper ITO 7b. The glass substrate 5a and the counter substrate 5b having such a surface structure are bonded to each other with a predetermined gap through the spacer 12 so that the film formation surfaces face each other. Although not shown, in order to form this gap, beads having a predetermined particle diameter are often scattered inside the spacer or between the substrates. A liquid crystal layer 8 is sealed in the substrate gap. The initial alignment of the liquid crystal molecules in the liquid crystal layer 8 is regulated by the vertical alignment films 9a and 9b. A lower polarizing plate 4a is disposed on the glass substrate 5a, and an upper polarizing plate 4b is disposed on the counter substrate 5b. The pixel area of the liquid crystal panel 13 is provided with an invalid display area that overlaps the black matrix 11 and the TFT area 6 and an effective display area. In this embodiment, the effective display area is defined as an opening. And Note that this opening corresponds to each dot on the liquid crystal panel 13.

  An illumination device is provided to illuminate the liquid crystal panel 13. In FIG. 1, a backlight is used as the illumination device. In this embodiment, a white LED package is used as the light source 1 of the backlight. The white LED package is a type in which a yellow phosphor is potted on a blue LED. A light guide plate 2 that guides light emitted from the light source 1 is disposed in front of the light source 1. In the present embodiment, the light source 1 is a point light source, and a side view type white LED is assumed, but it may be a top view, a bullet type, or a color other than white. The light guide plate 2 is a molded product of a transparent resin such as ZEONOR, PMMA, or PC. The light emitted from the light source 1 propagates through the transparent light guide plate 2 and is irradiated to the liquid crystal panel 13 side from the light emitting surface which is the upper surface of the light guide plate 2. Further, a reflecting plate 3 for improving the light irradiation efficiency is provided on the opposite surface side opposite to the exit surface of the light guide plate 2. Depending on the position and shape of the prism formed on the opposing surface of the light guide plate 2, the reflector 3 can be omitted. A light diffusion sheet may be provided between the light guide plate 2 and the liquid crystal panel. The light diffusing sheet has a fine concavo-convex shape formed on the surface, or beads are applied, thereby providing a function of diffusing light.

  FIG. 2 is a schematic diagram of the lighting device. A plurality of prisms are disposed on the light guide plate 2 only in an area corresponding to the opening of the liquid crystal panel 13. That is, the prism is arranged only on the back of the dot of the liquid crystal panel 13. A non-emission area is formed on the emission surface of the light guide plate 2 so as to correspond to the black matrix 11 and the TFT area 6 of the liquid crystal panel 13. In this embodiment, the prism has a pyramid shape. The shape of the prism is not limited to a pyramid, and may be a dome shape or a polyhedron having four or more surfaces. The light guide plate 2 is attached to the liquid crystal panel 13 via a double-sided tape. The pitch between the openings of the liquid crystal panel 13 is about 40 to 300 μm. The width and height of each prism are about 2 to 10 μm. Accordingly, several tens to several thousand prisms are arranged in an area facing one opening. In the present embodiment, the prism in the area close to the light source 1 is small and is configured to increase as the distance increases. With such a configuration, the light emitted from the light guide plate 2 can be controlled and made uniform.

  The liquid crystal panel 13 and the light guide plate 2 are each provided with an alignment mark. After the alignment mark is recognized with a camera or the like and aligned, it is fixed via a double-sided tape called a rim sheet. In general, the double-sided tape is white on the light guide plate 2 side and black on the liquid crystal panel 13 side. However, the double-sided tape may be black on both sides in order to prevent problems such as the eyeball of the light source.

  FIG. 7 shows a cross section of the light guide plate 2 of this embodiment. The operation of the prism will be described with reference to FIG. The reflecting surface of the prism facing the light source 1 has an angle of 40 to 50 ° with respect to the facing surface of the light guide plate 2 parallel to the light traveling direction from the light source 1. Since the light guide 2 is a transparent resin, it generally has a higher refractive index than air. Therefore, the light hitting the prism is totally reflected and emitted vertically from the emission surface.

  A case where a convex prism is used will be described with reference to FIG. As shown in the figure, unlike FIG. 7, the prism has a convex shape and is formed to protrude downward from the facing surface of the light guide plate 2. In FIG. 7, since the prism has a concave shape, the light in the oblique direction out of the light from the light source 1 hits the opposing surface of the light guide plate, and then hits the prism to emit light, thereby reducing the light utilization efficiency. . Further, when producing a concave prism by injection molding, it is necessary to make the mold convex, which is difficult to produce. The convex prism shown in FIG. 8 is easier to manufacture.

  An illumination device applicable to the present invention is schematically shown in FIG. The first embodiment and the present embodiment are the same in that the prism is arranged corresponding to each dot of the liquid crystal panel 13, but the size and quantity of the arranged prism are different. That is, in the first embodiment, the number of prisms arranged in the area corresponding to each dot of the liquid crystal panel 13 is the same, but the prism size is changed according to the distance from the light source 1. On the other hand, in this embodiment, the size of prisms in each area corresponding to each dot of the liquid crystal panel 13 is the same, but the number of prisms arranged in each dot is changed according to the distance from the light source 1. . With such a configuration, the light from the emission surface is uniformly controlled. The basic idea is the same in both cases, and the total area of the prisms formed in the area close to the light source 1 is reduced. For this reason, in this embodiment, the number of prisms is small in the area close to the light source 1 and increases as the distance increases. When creating a fine pattern as in the present invention, it may be difficult to change the pattern size for each area. In such a case, an illumination device configured as in this embodiment is preferable.

  A lighting device applicable to the present invention is schematically shown in FIG. In this embodiment, the reflecting surface of the prism that reflects the light emitted from the light source is perpendicular to the bright line of light. That is, the reflecting surface facing the light source is perpendicular to the straight line connecting the light source 1 and the prism. If the prism has a substantially fan shape in which donuts are cut into individual sides, light can be more efficiently guided to the light exit surface.

  FIG. 5 shows a cross-sectional view of the display device of this embodiment. The difference from the above-described embodiment is that an upper diffusion layer 15 is disposed above the liquid crystal panel 13. By providing the upper diffusion layer 15 on the liquid crystal panel 13, the light from the emission surface is diffused, and compared with the configuration of the first embodiment, the observer can easily see the image even when viewed obliquely. As the simplest configuration of the upper diffusion layer 15, there is one in which the upper polarizing plate 4b is subjected to AG treatment. However, the effect of diffusion is low, and it is reflected by external light and becomes whitish. Therefore, it is conceivable to dispose a film such as a diffusion film using a diffusion bead or a lens sheet. Alternatively, it is conceivable to use a diffusion paste having a high light diffusibility as an adhesive for fixing the upper polarizing plate 4b and the counter substrate 5b.

  FIG. 6 shows a cross-sectional view of the display device of this embodiment. A difference from the above-described embodiment is that a perforated reflection sheet 16 is disposed between the liquid crystal panel 13 and the light guide plate 2. In the above-described embodiment, the arrangement, angle, and size of the prisms of the light guide plate 2 are adjusted so that light is emitted only to the opening of the liquid crystal panel 13, but it is extremely difficult to align 100% of all light in an arbitrary direction. Have difficulty. A part of the light is emitted toward an area other than the opening and becomes useless light. Therefore, in this embodiment, the holes of the perforated reflection sheet 16 are arranged so as to be aligned with the openings of the liquid crystal panel 13 so that the light emitted outside the openings returns to the inside of the light guide plate.

  The perforated reflective sheet 16 is obtained by partially depositing a reflective film such as a silver thin film or a highly reflective metal thin film such as silver or aluminum on a transparent film such as a PET film. It need not be a perfect mirror surface of metal or the like, and may be a diffuse reflector such as white ink. The perforated reflective sheet 16 is provided with a transmission region corresponding to the opening of the liquid crystal panel 13, and no reflective film is deposited on this transmission region. In this embodiment, this transmissive region is referred to as a hole. In order to create a film having the above-described structure, masking vapor deposition, screen printing, ink jet printing, or a technique of etching the reflective layer in a photolithography process after vapor deposition once is conceivable.

  Further, the perforated reflective sheet 16 does not need to be an independent member, and the same effect can be obtained by forming a perforated reflective layer on the light exit surface of the light guide plate 2. With the above configuration, a display device with higher light utilization efficiency can be provided.

It is sectional drawing of the display apparatus by this invention. It is a schematic diagram of the illuminating device used for this invention. It is a schematic diagram of the illuminating device used for this invention. It is a schematic diagram of the illuminating device used for this invention. It is sectional drawing of the display apparatus by this invention. It is sectional drawing of the display apparatus by this invention. It is sectional drawing of the illuminating device used for this invention. It is sectional drawing of the illuminating device used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Light guide plate 3 Reflector 4a Lower polarizing plate 4b Upper polarizing plate 5a Glass substrate 5b Opposite substrate 6 TFT area 7a Lower ITO
7b Top ITO
8 Liquid crystal layer 9a Lower light distribution film 9b Upper light distribution film 10R Red color filter 10G Green color filter 10B Blue color filter 11 Black matrix 12 Spacer 13 Liquid crystal panel 14 Flattening layer 15 Upper diffusion layer 16 Perforated reflection sheet

Claims (5)

A display element having an opening area and a light shielding area on the display screen;
A light source;
In a display device comprising: an incident surface on which light emitted from the light source is incident; an exit surface that guides the emitted light and exits the display screen as illumination light; and a light guide plate having a facing surface facing the exit surface. ,
The exit surface corresponds to the opening region and emits the illumination light, and has a non-exit region that corresponds to the light shielding region and does not emit the illumination light.
On the facing surface, a plurality of prisms are arranged only in the area facing the emission region,
The plurality of prisms are arranged for each area facing the emission region,
The display device, wherein the opening area is illuminated only by light emitted from the emission area. The prism has a reflecting surface that reflects the light emission,
The reflecting surface, the line of intersection intersecting the opposing surface is perpendicular to the straight line connecting the prism and the light source, a display device according to claim 1, characterized in that a generally fan shape. The prism has a reflecting surface that reflects the light emission,
The display device according to claim 1 , wherein the reflection surface has an inclination angle with respect to the facing surface of 40 to 50 ° with respect to a traveling direction of light from the light source.   The display device according to claim 1, wherein a diffusion layer is disposed on a display screen of the display element.   The display device according to claim 1, wherein a reflective layer having an opening corresponding to the opening region is provided between the light guide plate and the display element.

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