JP2005148440A - Illumination light control sheet and display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device on which a bright display video is visualized to an observer and a built-in light source (such as back-light) is efficiently utilized, by providing a display screen with such directivity as the display video light is made to exit downward where the observer is located without installing the display screen in the state directed to the observer below but even in a normal installation state, when the display device is used in the state of being installed on a high place. <P>SOLUTION: When parallel light is made to incident to the flat surface of a lens sheet which has a lens part with unit lenses arranged on one side and has a flat surface on the opposite side of the lens part in the neighborhood of the focal length by the lens part, an illumination light control sheet of such a configuration is employed, as a shade pattern is formed at the sections corresponding to non-condensation parts of the lens part from the lens part side at a non-vertical angle to the lens sheet main surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical member capable of suitably controlling the optical path of display video light, which is applied to a display device represented by a transmissive liquid crystal display device including a backlight system that irradiates a liquid crystal panel from the back side.

  In recent years, liquid crystal display devices using a liquid crystal panel made of TFT or STN are being commercialized mainly in (color) notebook PCs (personal computers) in the OA field.

  In such a liquid crystal display device, a so-called backlight method, in which a light source is disposed on the back side of the liquid crystal panel and the liquid crystal panel is irradiated with light from the light source, has been conventionally employed.

  Such a backlight system is roughly classified by attaching a light source lamp such as a cold cathode fluorescent lamp (CCFT) along a side end portion of a flat light guide plate made of acrylic resin or the like having excellent light transmittance. There are a light guide plate light guide method (so-called edge light method) in which light from the multiple light is reflected in the light guide plate and a direct type method without using the light guide plate.

  Recently, a light guide light guide type backlight system has become mainstream because it is easy to reduce the thickness.

  As a liquid crystal display device on which a light guide plate light guide type backlight system is mounted, for example, one having a configuration as shown in FIG. 1 is generally known. In this, a liquid crystal panel 72 sandwiched between polarizing plates 71 and 73 is provided at the top, and a light guide plate 79 made of a substantially rectangular plate-like PMMA (polymethyl methacrylate) or the like is disposed on the lower surface side thereof. A diffusion film (diffusion layer) 78 is provided on the upper surface (light emitting surface) of the light guide plate. Further, on the lower surface of the light guide plate 79, a scattering reflection pattern portion 82 for efficiently scattering and reflecting the light introduced into the light guide plate 79 in the direction of the liquid crystal panel 72 is provided by printing or the like. In addition, a reflection film (reflection layer) 77 is provided below the scattering reflection pattern portion 82.

  In addition, a light source lamp 76 is attached to the light guide plate 79 along the side end portion. Further, in order to make light from the light source lamp 76 enter the light guide plate 79 efficiently, the rear side of the light source lamp 76 is arranged. A lamp reflector 81 having a high reflectivity is provided so as to cover it.

  The scattering reflection pattern portion 82 is a mixture of white titanium dioxide (TiO2) powder mixed in a solution such as a transparent adhesive, printed in a predetermined pattern, for example, a dot pattern, dried, and formed. This is a means for providing directivity to the light incident on the light guide plate 79 and guiding the light toward the light exit surface, thereby increasing the brightness.

  Furthermore, in order to increase the light utilization efficiency and increase the brightness, prism films (prism layers) 74 and 75 having a light condensing function between the diffusion film 78 and the liquid crystal panel 72 as shown in FIG. Has been proposed. The prism films 74 and 75 are for condensing the light emitted from the light emitting surface of the light guide plate 45 and diffused by the diffusion film 78 on the effective display area of the liquid crystal panel 72 with high efficiency.

  As the prism film, a brightness enhancement film (BEF), which is a trademark of 3M USA, is widely used.

  BEF is a film that contains a repetitive array of prisms. The prism is large compared to the wavelength of light. BEF collects light from “off-axis” and redirects this light “on-axis” or “recycle” towards the viewer. To do.

  When using the display (when observing), the BEF increases the on-axis brightness by reducing the off-axis brightness. Here, “on-axis” refers to a direction that matches the visual direction of the viewer, and is generally the normal direction (front) to the display screen.

  When the repetitive array structure of prisms is arranged in only one direction, only the direction change or recycling in the parallel direction is possible, and in order to control the luminance of the display light in the horizontal and vertical directions, the parallel direction of the prism groups Are stacked and used in combination so that they are substantially orthogonal to each other.

  However, in these methods, the control of the visual field range is left only to the diffusibility of the diffusion film 78, which is difficult to control, and the characteristic that the central part in the diffusion direction becomes brighter and darker as it goes to the peripheral part is unavoidable. For this reason, when the liquid crystal screen is viewed from the side, the luminance is greatly reduced, which causes a reduction in light use efficiency.

  Furthermore, in the method using a prism film, since the number of prism films is two, the amount of light is greatly reduced due to absorption of the film, and the cost increases as the number of optical members increases. It was.

  By the way, in such a liquid crystal display device, there is a strong demand as a market need to be thin, low power consumption and high brightness, and accordingly, the backlight system mounted on the liquid crystal display device is also thin. In addition, low power consumption and high luminance are required.

  In particular, in a color liquid crystal display device that has recently made remarkable progress, the panel transmittance of the liquid crystal panel is significantly lower than that of a monochrome-compatible liquid crystal panel. It has become an indispensable issue for obtaining power consumption.

  However, in the conventional configuration as described above, it is difficult to say that the demand for high luminance and low power consumption is sufficiently met today, where the liquid crystal display device is further reduced in thickness. The development of a backlight system capable of realizing a liquid crystal display device with high brightness, high display quality, and low power consumption has been awaited.

  Therefore, in view of the above problems, the present applicant has shown the following for the purpose of providing a low-cost, high-brightness, high-display quality, and low-power consumption liquid crystal display device that can meet the user's request. A liquid crystal display device having a configuration has been proposed.

A liquid crystal panel and a light source means for irradiating the liquid crystal panel with light from the back side are provided. The light source means is provided with a lens layer for guiding the light from the light source to the liquid crystal panel, and is opened near the focal plane of the lens layer. It has the light-shielding part which has. (Patent Document 1)
A configuration example of the liquid crystal display device according to Patent Document 1 is shown in FIG.

  A liquid crystal panel 12 sandwiched between polarizing plates 11 and 13 is provided on the upper side, and a light guide plate 79 made of a substantially rectangular plate-like PMMA (polymethyl methacrylate) or the like is disposed on the lower surface side thereof. A scattering reflection pattern portion 82 for efficiently scattering and reflecting the light introduced into the light guide plate 79 so as to be uniform in the direction of the liquid crystal panel 12 is provided on the lower surface of 79 by printing or the like. A reflective film (reflective layer) 77 is provided below the portion 82.

  A light source lamp 76 is attached to the light guide plate 79 along the side end portion. Further, the light source lamp 76 covers the back side of the light source lamp 76 so that the light from the light source lamp 76 is efficiently incident on the light guide plate 79. A high-reflectance lamp reflector 81 is provided.

The scattering reflection pattern part 82 is formed by printing a mixture of white titanium dioxide (TiO2) powder in a solution such as a transparent adhesive in a predetermined pattern, for example, a dot pattern. Light scattered by the scattering pattern portion 82 and the like is emitted from the upper surface of the light guide plate 79. A lens layer 15 composed of a plurality of lenses is disposed on the light emission side, and a light shielding layer 18 having an opening corresponding to each lens is disposed in the vicinity of the focal plane of the lens constituting the lens layer 15. The light emitted from the light guide plate 79 passes only through the opening of the light shielding layer 18 and enters the lens layer 15. Since the light shielding layer is disposed in the vicinity of the focal point, the light emitted from one point of the light shielding layer 18 is emitted from the lens layer 15 as light in a certain direction by the lens. Therefore, the direction of light emitted from the lens layer can be determined by the size of the opening of the light shielding layer 18.
JP 2000-284268 A

As a usage form of the display device, a relatively large (large screen) TV, a monitor, or the like is installed on the upper side in order to provide a display image to a large number of observers, and the observer looks up from below. There is a method. (See Figure 9)
In the above method in which the display device is installed above, many observers over a wide range can see the screen of the display device. However, if the display device is simply installed at the upper position, the screen is an observer. In the case of a liquid crystal display device having a built-in light source (such as a backlight), the display image light does not have directivity so that the display image light is emitted downward toward the observer's position. The projected light is not used effectively.

  In order to install the display device with the screen facing the viewer below, it is necessary to stabilize and fix the display device so that it does not fall.

  In the use of the display device in the above-described method, the present invention does not install the display device with the screen facing the viewer below, and the display image light is located below the viewer's position even in a normal installation state. An object of the present invention is to provide a display device having a configuration in which a bright display image is visually recognized for an observer by having directivity that emits light toward the viewer, and a built-in light source (backlight, etc.) of the display device is effectively used. And

  In the present invention, even when the display device is used in a normal installation state, the display video light is not configured to be emitted in a direction centered on a perpendicular to the screen (that is, a direction centered on the horizontal direction), but the perpendicular The above object is realized by adopting a configuration in which display image light is emitted centering on the lower side.

  In a liquid crystal display device having a backlight, it is necessary to improve the illumination light for the liquid crystal panel so that the irradiation component at a non-vertical angle centered on the lower side is increased.

The illumination light control sheet of the present invention according to the invention of claim 1
It has a lens part in which unit lenses are arranged on one side, and the lens sheet has a flat surface on the side opposite to the lens distance near the focal length by the lens part. When parallel light is incident at a non-perpendicular angle, a light-shielding pattern is formed at a position corresponding to a non-condensing portion by the lens portion.

  It is preferable that at least one of the surfaces of the light shielding pattern on the lens portion side and the anti-lens portion side has light reflectivity.

In the present invention, it is desirable that the formation location of the light shielding pattern is defined by the following relationship.
-Refractive index of the material constituting the lens sheet: n
The angle at which incident light from the center of the opening of the light shielding pattern propagates through the lens sheet when it exits from the top of the corresponding unit lens: α
・ An angle at which the above incident light exits from the top of the unit lens: β
Lens sheet thickness (distance from the top of the unit lens to the flat surface on the side opposite to the lens): T
Under the above conditions, when the shift amount from the point where the perpendicular to the lens sheet from the top of the unit lens intersects the flat surface on the side opposite to the lens to the center of the opening is s,
s = Ttan (arcsin (sin (β) / n))
A display device to which the illumination light control sheet of the present invention is applied,
A transmissive image display element in which a display image is defined according to selective transmission / non-transmission in pixel units, and light source means for irradiating light to the display element,
The illumination light control sheet of the present invention is arranged between the light source means and the display element.

As a general display device,
The display element is a liquid crystal panel,
The light source means functions to illuminate a large amount of components at non-vertical angles over the entire surface of the liquid crystal panel,
The light shielding pattern formed on the illumination light control sheet of the present invention is formed so that the portion corresponding to the non-light-collecting portion when the parallel light is incident at an angle corresponding to the above angle becomes the light shielding portion.

  Without having to place the screen of the display device facing the viewer below, even in a normal installation state, the display image light has directivity so that it emits downward toward the viewer's position. For a person, a bright display image is visually recognized, and a display device having a configuration in which a built-in light source (backlight or the like) of the display device is effectively used is provided.

  The display device according to the present invention is very suitable for installing a display image to a large number of observers by installing the display device above (high place).

  Hereinafter, embodiments of the present invention will be described.

  FIG. 4 is an explanatory diagram conceptually showing the main part of an example of the display device according to the present invention.

  By selectively controlling transmission / non-transmission on a pixel-by-pixel basis, on the back side of the liquid crystal panel 7 which is an image display element that defines a display image (on the side opposite to the observer, left side in the figure) On the other hand, the backlight system irradiates the illumination light in a planar shape, and the illumination light control sheet 4 of the present invention is arranged on the front side (observer side) of the system.

  In the backlight system illustrated in FIG. 4, when light incident from a light source lamp 1 such as a cold cathode fluorescent lamp (CCFT) propagates downward in the figure while repeating total reflection in the light guide plate 2, The light 3 is emitted from the light guide plate 2 in the right direction in FIG.

  The exit location and the light amount of the light 3 are controlled by the formation location and area of the scattering reflection pattern portion 82 as described in the prior art.

  In the figure, the emission direction of the light 3 is indicated by a right-down arrow. However, in the case of only the edge light type light guide plate, the in-plane of the light guide plate corresponding to the display screen is formed by the method of forming the scattering reflection pattern portion 82. It is possible to make the luminance distribution of the light 3 uniform, but it is difficult to control the emission direction, and in the case of FIG.

  In the edge light system, there is a difference in the emission angle of the light 3 depending on the design of the light guide plate, but in the case of the figure, the light is often emitted in the range of 50 ° to 80 ° clockwise with respect to the perpendicular to the main surface. The center is about 70 °.

  As described in the prior art, the light whose luminance distribution is made uniform in the plane by the light guide plate is emitted substantially perpendicularly to the display screen (in the figure, horizontally from left to right). A prism film such as BEF is used, but in the present invention, the display device is installed at a high place so that the viewer can view the display image at a lower place. Light 3 is preferred.

  Next, the light 3 enters the illumination light control sheet 4.

The illumination light control sheet 4 of the present invention is
It has a lens unit 6 in which unit lenses are arranged on one side, and the lens surface from the lens unit side to the main surface of the lens sheet is the flat surface of the lens sheet that has a flat surface on the side opposite to the lens by the lens unit. When the parallel light is incident at a non-perpendicular angle, the light shielding pattern 5 is formed at a position corresponding to the non-light condensing part by the lens part.

  The “angle non-perpendicular with respect to the lens sheet main surface” referred to here corresponds to the angle of the light 3 centered at approximately 70 °.

  In the case of the figure, the light incident from the non-light-shielding part (opening part) on the flat surface of the lens sheet receives the lens action and is emitted to the liquid crystal panel 7.

  Of course, the opening corresponds to a condensing part by the lens part when parallel light is incident from the lens part side of the lens sheet at a non-perpendicular angle (centered at 70 °) with respect to the lens sheet main surface. It becomes.

  FIG. 5 is an explanatory diagram showing an enlarged behavior of the light 3 incident on the illumination light control sheet 4.

  The light 3 emitted from the light guide plate 2 is incident from a non-light-shielding portion (opening portion) on the flat surface of the lens sheet at an angle having a spread around 70 °.

  In the same figure, the incident light from the upper end of a certain opening and the incident light from the lower end are emitted as two parallel light beams having a difference of θ in the emission angle by the lens action.

  The light 3 naturally has a component light that does not reach the opening of the lens sheet, but the surface of the light shielding pattern 5 (on the side opposite to the lens portion in the figure) has light reflectivity, so that it strikes the light shielding pattern 5. The reflected light returns to the light guide plate (light source) side and repeats various behaviors (reflection at the interface of the light guide plate, incidence inside the light guide plate, etc.), and component light that enters from the opening of the lens sheet Therefore, the light from the light source is effectively used as illumination light.

  That is, in the present invention, the prism film represented by BEF functions to emit light that is incident non-perpendicularly to the film main surface in a direction substantially perpendicular to the film main surface, whereas illumination light The light that enters the main surface of the control sheet non-perpendicularly functions so as to be emitted in a non-perpendicular direction accordingly.

  The difference in the above functions is that the incident light to the prism film is designed to cause total reflection at the interface between the unit prism and the exit side air layer, whereas in the illumination light control sheet of the present invention, This is because, in principle, total reflection does not occur at the interface between the unit lens and the exit-side air layer.

  The main feature of the present invention is the shift (displacement) of the formation location of the light shielding pattern formed on the illumination light control sheet.

  As described above, the opening portion of the light shielding pattern is formed by the lens portion when parallel light is incident at a non-perpendicular angle (centered at 70 °) with respect to the lens sheet main surface from the lens portion side of the lens sheet. It becomes a location corresponding to a condensing part.

  In order to accurately form such a light shielding pattern on the side opposite to the lens portion of the lens sheet, the aperture corresponding to the condensing portion / non-condensing portion is utilized by utilizing the condensing characteristic of the lens portion of the lens sheet itself. A so-called self-alignment method for defining the part / light-shielding part is preferably used.

  In the self-alignment method, a photopolymer layer that undergoes some modification due to light exposure is formed on the entire surface of the lens sheet on the side opposite to the lens, and light rays that modify the photopolymer layer are irradiated at an angle of 70 ° from the lens unit. This is done by defining the modified / non-modified parts.

  In forming the light-shielding pattern having high surface reflectivity as described above, a technique such as transferring an Al foil to the adhesive part of the photopolymer layer that has been made adhesive / non-adhesive by modification is employed. .

  FIG. 6 is an explanatory diagram showing the design concept of the illumination light control sheet.

The location where the light shielding pattern is formed is defined so as to satisfy the following relationship.
-Refractive index of the material constituting the lens sheet: n
The angle at which incident light from the center of the opening of the light-shielding pattern is emitted from the top of the corresponding unit lens and propagates inside the lens sheet: α (70 ° in the case of FIGS. 4 and 5)
・ An angle at which the above incident light exits from the top of the unit lens: β
Lens sheet thickness (distance from the top of the unit lens to the flat surface on the side opposite to the lens): T
Under the above conditions, when the amount of shift from the point where the perpendicular to the lens sheet from the top of the unit lens intersects the flat surface on the side opposite to the lens to the center of the opening is s,
From Snell's relationship
n sin (α) = sin (β) (1)
tan (α) = s / T (2)
(1) From equation (2)
s = Ttan (arcsin (sin (β) / n))
FIG. 7 is an explanatory view of the illumination light control sheet as viewed from the light shielding pattern side. The position where the light shielding pattern is formed is defined by the shift amount s at the center of the opening shown in the figure, and the emission direction of the display light is controlled. Will be.

  Furthermore, the optical characteristics can be controlled by the width of the opening.

  FIG. 8 is a graph showing luminance characteristics corresponding to the width of the opening.

  When the opening is narrow, the brightness is very high in a narrow range before and after the center of the opening (“up and down” in the usage mode of the display device).

  When the opening is wide, the luminance is high (lower than that in the above case) in a wider range than in the above case before and after the center of the opening.

  The reason why the former shows high brightness in a narrow range is that, as described with reference to FIG. 5, there are many components that behave such that the light reflected by the light shielding pattern is incident on the opening again (the degree of reuse). Is high).

  The smaller the width of the opening, the stronger the directivity of the backlight. On the other hand, increasing the width reduces the directivity and increases the degree of diffusion.

  Even if the lens sheet constituting the illumination light control sheet 4 is a lenticular sheet in which convex cylindrical lens groups are arranged in parallel, a lens sheet (microlens, fly-eye lens, etc.) in which unit lenses are two-dimensionally arranged May be used).

  In the former case, the opening is linear (parallel to the vertical direction that is the parallel direction of the unit lenses), but in the latter case, the opening is spot-like, and the direction can be changed by changing the shape of the opening. It is also possible to change the diffusivity.

  For example, if an opening that is large in the horizontal direction and small in the vertical direction is used, a wide observation area can be taken in the horizontal direction with respect to the vertical direction.

  In general, since the viewing area in the vertical direction is small as the liquid crystal characteristics, the light utilization efficiency can be further improved by setting the backlight characteristics to be narrow in the vertical direction in advance.

Explanatory drawing which shows the structural example of the liquid crystal display device by which the backlight system of a light-guide plate light guide system is mounted. Explanatory drawing which shows the structural example of the liquid crystal display device by which the backlight system which employ | adopted the prism film was mounted. Explanatory drawing which shows the structural example of the liquid crystal display device by which the backlight system which employ | adopted the lens layer which has a light-shielding part was mounted. Explanatory drawing which shows notionally the principal part about an example of the display apparatus by this invention. Explanatory drawing which expands and shows the behavior of the light which injects into an illumination light control sheet. Explanatory drawing which shows the design concept of an illumination light control sheet. Explanatory drawing which looked at the illumination light control sheet from the light-shielding pattern side. The graph which shows the luminance characteristic according to the size of the width | variety of an opening part. Explanatory drawing which shows the usage pattern which installs and visually displays a display apparatus in a high place.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,76 ... Light source lamp 2, 79 ... Light guide plate 3 ... Light 4 ... Illumination light control sheet 5 ... Light-shielding pattern 7, 72 ... Liquid crystal panel 15 ... Lens layer 18 ... Light shielding layers 71, 73 ... Polarizing plate 72 ... Liquid crystal panels 74,75 ... Prism film (prism layer)
77 ... Reflective film (reflective layer)
78 ... Diffuse film 81 ... Lamp reflector 82 ... Scattered reflection pattern

Claims (7)

  It has a lens part in which unit lenses are arranged on one side, and the lens sheet has a flat surface on the side opposite to the lens distance near the focal length by the lens part. An illumination light control sheet having a configuration in which a light-shielding pattern is formed at a position corresponding to a non-condensing portion by the lens portion when parallel light is incident at a non-vertical angle.   The illumination light control sheet according to claim 1, wherein at least one of the surfaces of the light shielding pattern on the lens portion side and the anti-lens portion side has light reflectivity. The lens unit is a configuration in which convex cylindrical lens groups are arranged in parallel.
3. The illumination according to claim 1, wherein the light-shielding pattern is a striped pattern having a light-reflecting surface on a surface other than a stripe-shaped condensing portion formed by a convex cylindrical lens group as an opening. 4. Light control sheet. The lens unit is configured by two-dimensionally arranging unit convex lens groups,
3. The illumination light control sheet according to claim 1, wherein the light shielding pattern has a light reflecting surface other than a spot-like light condensing portion formed by the unit convex lens group as an opening. 4. The illumination light control sheet according to any one of claims 1 to 4, wherein the formation position of the light shielding pattern is defined by the following relationship.
-Refractive index of the material constituting the lens sheet: n
The angle at which incident light from the center of the opening of the light shielding pattern propagates through the lens sheet when it exits from the top of the corresponding unit lens: α
・ An angle at which the above incident light exits from the top of the unit lens: β
Lens sheet thickness (distance from the top of the unit lens to the flat surface on the side opposite to the lens): T
Under the above conditions, when the shift amount from the point where the perpendicular to the lens sheet from the top of the unit lens intersects the flat surface on the side opposite to the lens to the center of the opening is s,
s = Ttan (arcsin (sin (β) / n)) A transmissive image display element in which a display image is defined according to selective transmission / non-transmission in pixel units, and light source means for irradiating light to the display element,
A display device having a configuration in which the illumination light control sheet according to claim 1 is disposed between the light source means and the display element. The display element is a liquid crystal panel,
The light source means functions to illuminate a large amount of components at non-vertical angles over the entire surface of the liquid crystal panel,
The light-shielding pattern formed on the illumination light control sheet according to any one of claims 1 to 5 is formed at a location corresponding to a non-condensing portion when parallel light is incident at an angle corresponding to the above-described angle. The display device according to claim 6.

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