JP2007148185A - Light diffusion sheet, transmission screen, rear projection type display device, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusion sheet which can smooth light diffusion characteristics of a transmission screen when mounted on the transmission screen as a light diffusion sheet. <P>SOLUTION: The light diffusion sheet has at least a light diffusion part 12 which diffuses part of video light incident from one thickness-directional surface (incident surface 1a) by total reflection and projects it from the other surface (projection surface 1b). The light diffusion part 12 is formed by providing a wedge sectioned light reflection part 2 where a groove 15 tapered from the projection surface 1b to the incident surface 1a is filled with resin and a nearly trapezoidal sectioned light transmission part 4 which is provided between light reflection parts 2 and 2 and transmits the video light successively and alternately. Each light reflection part 2 is characterized in that the resin charged in the groove 15 has a lower refractive index than the light transmission part 4 and opposite surface forming the groove 15 of the light reflection part 2 each has an inclined plane 3 including a first inclined surface 3a which is disposed on the side of the incident surface 1a and has an angle for totally reflecting video light and a second inclined plane 3b which is disposed for connecting the first inclined plane 3a and projection surface 1b and has an angle for refracting and transmitting the video light. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light diffusing sheet, a transmissive screen, a rear projection display device, and a liquid crystal display device. More specifically, the light diffusing characteristic of the transmissive screen is gently reduced when the light diffusing sheet is mounted on the transmissive screen. The present invention relates to a light diffusing sheet that can be used, a transmissive screen including the light diffusing sheet, a rear projection display device, and a liquid crystal display device.

  A large-screen display device such as a rear projection display device often sees images projected on a transmissive screen (hereinafter simply referred to as “screen”) by a plurality of people, compared to a small display device. A wide viewing angle is required. For example, a projection television, which is a rear projection display device, includes a transmissive screen that projects video light emitted from a light source. In general, this transmissive screen diffuses the substantially parallel light and a Fresnel lens sheet that is a lens member for deflecting the image light projected from the light source to the observer side into substantially parallel light (including parallel light). And a lenticular lens sheet which is a light diffusion sheet for widening the viewing angle of the image.

  By the way, regarding the light diffusion sheet, when the light diffusion sheet is viewed in plan, (1) a refractive type lenticular lens sheet in which cylindrical lenses extending in the vertical direction are juxtaposed in the horizontal direction, and (2) an observer. A light reflecting portion having a substantially wedge-shaped cross-section in which a groove tapering from the side surface toward the light source side is filled with a resin, and a light having a substantially trapezoidal cross-section that is provided between the light reflecting portions and transmits image light. A total reflection type lenticular lens sheet in which incident portions are totally reflected on an inclined surface forming a light reflection portion, which are alternately arranged in parallel, is known.

  FIG. 17 is a schematic cross-sectional view showing an example of a total reflection type lenticular lens sheet among the lenticular lens sheets (see, for example, Patent Document 1). As shown in FIG. 17, the total reflection type lenticular lens sheet 201 usually has a base material 211, a light diffusion part 212, an adhesive layer 213, and a support plate 214 in that order. A light reflecting portion 202 filled with a resin containing a light absorbing material in a plurality of substantially V-shaped grooves 215 tapering toward the material side, and a cross section provided between the light reflecting portions to transmit image light The light transmitting portion 204 has a substantially trapezoidal shape.

The upper base 216 side of each light transmission portion 204 is an emission surface, and the light reflection portion 202 on the emission surface side is a black stripe pattern (BS pattern) having light absorption. In the light transmitting portion 204, in the region A where the upper base 216 and the lower base 217 overlap in plan view, the light parallel to the optical axis is transmitted as it is and emitted from the emission surface, but in the other regions B, the optical axis Is totally reflected at the interface between the light transmitting portion 204 and the light reflecting portion 202, and the upper base 216 of the light transmitting portion 204 and a medium layer (on the adhesive layer 213 or The light is refracted at the interface with the support plate 214). In the total reflection type lenticular lens sheet 201, since the light reflecting portion 202 is usually formed of a resin material including a light absorbing material, the light reflecting portion 202 functions as a BS pattern and is reflected on the transmissive screen. It works to improve the contrast of the displayed image.
JP 2004-4148 A

  In recent years, in a rear projection type display device, a single-tube type light source using LCD (Liquid Crystal Display) and DLP (Digital Light Processing) (hereinafter referred to as “ Single light source ") has been used. When this single light source is used, there is an advantage that the still image and the character display become clearer by the pixel display which is a feature of the single light source, but on the other hand, such an advantage causes a lack of contrast which has not been a problem so far. It is a problem. Therefore, there is a demand for a transmission screen that can further improve contrast and display a tightened image.

  18 shows a ray path diagram (FIG. 18A) and a light diffusion characteristic graph (FIG. 18B) of a transmission type screen using the conventional total reflection type lenticular lens sheet shown in FIG. It is an example. As shown in FIG. 18A, the light incident on the region A where the upper base and the lower base overlap in plan view is output as it is from the output surface of the light transmitting portion 204, but has the width of the light reflecting portion 202. The light incident on the region B is totally reflected at the interface between the light transmission unit 204 and the light reflection unit 202 and is emitted from the emission surface of the light transmission unit 204. As shown in FIG. 18 (B), the light diffusion characteristic does not have a parabolic shape with the front of the screen having a viewing angle of 0 ° as the apex, but peaks in the region a having a peak at the viewing angle of 0 ° and on the left and right. This is a graph in which regions b1 and b2 having The peak of the region a appears due to the light transmitted through the region A as it is, and the two peaks of the regions b1 and b2 appear due to the light totally reflected at the interface between the light transmitting portion 204 and the light reflecting portion 202. The light diffusion characteristics are measured with a minute declination luminance meter, and the front of the lenticular lens sheet is 0 °, the horizontal axis is the observation angle, and the vertical axis is the gain (referred to as gain).

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide light that can smoothen the light diffusion characteristics of a transmissive screen when it is mounted on the transmissive screen as a light diffusion sheet. An object of the present invention is to provide a diffusing sheet, a transmissive screen including the light diffusing sheet, a rear projection display device, and a liquid crystal display device.

  The light diffusing sheet of the present invention for solving the above-described problem has at least a light diffusing portion for diffusing a part of video light incident from one surface in the thickness direction by total reflection and emitting it from the other surface side. The light diffusing portion is provided between the light reflecting portion and the light reflecting portion having a substantially wedge-shaped cross section in which a groove tapering from the other surface toward the one surface is filled with the resin. In the light diffusing sheet in which light transmitting portions having a substantially trapezoidal cross section that transmits light are alternately arranged, the refractive index of the resin filled in the groove is lower than the refractive index of the light transmitting portion, A facing surface forming a groove of the light reflecting portion is located on the one surface side so as to connect the first inclined surface having an angle for totally reflecting the image light, and the first inclined surface and the other surface. A slope including a second slope having an angle at which the image light is refracted and transmitted. Thus it is formed, characterized in that is (also referred to as the light diffusing sheet and "light diffusion sheet I".).

  According to the present invention, the opposing surface forming the groove of the light reflecting portion is located on one surface side and has a first inclined surface having an angle that totally reflects the image light, and the first inclined surface and the other surface. The light diffusion characteristic of the image light diffused by this light diffusion sheet (particularly the light diffusion of horizontal diffusion) (Characteristic) graph can be made gentle. Such an improvement in the light diffusion characteristics is attributed to the discontinuity of the diffusion angle on the second inclined surface that refracts and transmits the image light.

  In the light diffusing sheet I of the present invention, the light reflecting portion is characterized in that the groove is filled with a resin containing light absorbing particles (this light diffusing sheet is also referred to as “light diffusing sheet II”). .)

  According to the present invention, the light reflecting portion filled with the resin containing the light absorbing particles has light absorptivity, so that the light reflecting portion can absorb the refracted light without being totally reflected. As a result, contrast can be improved.

  In the light diffusion sheet II of the present invention, it is preferable that the average particle diameter of the light absorbing particles is larger than the height from the other surface to the intersection where the first slope and the second slope meet. .

  According to this invention, since the average particle diameter of the light-absorbing particles is larger than the height from the other surface to the intersection where the first inclined surface and the second inclined surface intersect, it is formed at an angle that refracts and transmits the image light. There are few light-absorbing particles existing in the vicinity of the two slopes. As a result, the image light refracted on the second slope can be transmitted without being absorbed by the light absorbing particles in the vicinity of the second slope.

  In the light diffusing sheet I of the present invention, a light absorption layer is formed on the other surface of the light reflecting portion and on a region overlapping the first inclined surface facing in the groove of the light reflecting portion in plan view. It is formed (this light diffusion sheet is also called "light diffusion sheet III").

  According to this invention, the light absorption layer formed on the region overlapping the first inclined surface facing in the groove of the light reflecting portion in plan view absorbs the refracted light without being totally reflected by the light reflecting portion. Contrast can be improved.

  A transmissive screen according to the present invention for solving the above-described problems includes the light diffusion sheet according to the present invention. According to the present invention, since the light diffusion sheet of the present invention is provided, a transmission screen having a gentle graph of light diffusion characteristics of image light (particularly, light diffusion characteristics of horizontal diffusion) can be obtained.

  In the transmissive screen of the present invention, it is preferable that a Fresnel lens sheet is disposed or a Fresnel lens portion is bonded to the side on which the image light is incident. Furthermore, it is preferable that the Fresnel lens sheet or the Fresnel lens part has a total reflection Fresnel lens.

  In the transmissive screen of the present invention, a support plate may be disposed or joined on the side from which the image light is emitted.

  In the transmissive screen of the present invention, a touch panel may be provided on the outermost surface on the side from which the image light is emitted. According to this invention, since the touch panel is provided, a multifunctional rear projection display device can be configured.

  The rear projection display device of the present invention for solving the above-mentioned problems has the light diffusion sheet of the present invention as a constituent member of the transmissive screen in the rear projection display device equipped with the transmissive screen. It is characterized by. According to the present invention, it is possible to provide a rear projection display device having good light diffusion characteristics and a wide viewing angle.

  Moreover, the liquid crystal display device of the present invention for solving the above-described problems is a liquid crystal display device having a display liquid crystal panel, wherein the viewing angle enlarging member disposed or bonded on the display surface of the display liquid crystal panel is It has the light-diffusion sheet of this invention, It is characterized by the above-mentioned. At this time, a touch panel may be provided on the outermost surface of the display surface. According to the present invention, it is possible to provide a liquid crystal display device having good light diffusion characteristics and a wide viewing angle.

  According to the light diffusion sheet of the present invention, since the graph of the light diffusion characteristics of image light (particularly, the light diffusion characteristics of horizontal diffusion) can be made smooth, the viewing angle characteristics can be improved. In addition, according to the transmissive screen of the present invention, the graph of the light diffusion characteristics of image light (particularly, the light diffusion characteristics of horizontal diffusion) becomes smooth, and the viewing angle characteristics can be improved. Further, according to the rear projection display device and the liquid crystal display device using the light diffusion sheet of the present invention as a constituent member, it is possible to provide a rear projection display device or a liquid crystal display device having good light diffusion characteristics and a wide viewing angle. .

  Hereinafter, a light diffusion sheet, a transmissive screen, a rear projection display device and a liquid crystal display device of the present invention will be described with reference to the drawings. The technical scope of the present invention is not limited to the following embodiments.

(Light diffusion sheet)
FIG. 1 is a schematic cross-sectional view showing an example of the light diffusion sheet of the present invention. The light diffusing sheet 10 of the present invention diffuses part of video light incident from one surface in the thickness direction (hereinafter referred to as an incident surface 1a) by total reflection, and diffuses the other surface (hereinafter referred to as an output surface 1b). .)) At least a light diffusing unit 12 that emits light from the side. As a specific example, as shown in FIG. 1, from the light source side, a base material 11 and a light diffusing unit that is provided on the base material 11 and diffuses a part of video light from the base material side by total reflection. 12 and a support plate 14 bonded via an adhesive layer 13 provided on the light diffusion portion 12 can be illustrated, but the base material 11 and the support plate 14 are not necessarily bonded. They are not necessarily provided, and they are provided arbitrarily.

  As shown in FIG. 1, the present invention is characterized by the structure of a light diffusing unit 12 in which light reflecting units 2 and light transmitting units 4 are alternately arranged in parallel. The light reflecting portion 2 has a substantially wedge shape in which a groove 15 tapered from the exit surface 1b toward the entrance surface 1a is filled with a resin, and the light transmitting portion 4 is interposed between the light reflecting portions 2 and 2. It is provided and has a substantially trapezoidal cross section that transmits image light. A feature of the present invention is that a first inclined surface 3a having an angle at which the opposing surface forming the groove 15 of the light reflecting portion 2 is located on the incident surface 1a side and totally reflects the image light, and the first inclined surface 3a It is formed by the slope 3 including the second slope 3b that is positioned so as to connect to the emission surface 1b and has an angle that refracts and transmits the image light. As shown in FIG. 1, the light transmitting portion 4 has a substantially trapezoidal cross-sectional shape represented by an upper base 16 on the emission surface 1 b side connecting the tips of the grooves 15 and a lower base 17 on the incident surface 1 a side. It is.

  When the light diffusing sheet 10 is viewed from the observer side or the light source side (hereinafter referred to as a plan view), in the region A where the upper base 16 and the lower base 17 of the light transmission portion 4 overlap in a plan view, the optical axis OA. The light parallel to is transmitted as it is and emitted from the emission surface 1b. On the other hand, in the regions B1 and B2 corresponding to the first inclined surface 3a, the light parallel to the optical axis OA is totally reflected by the first inclined surface 3a and passes through the light transmitting portion 4 and is emitted from the emitting surface 1b. In the regions C1 and C2 corresponding to the second inclined surface 3b, the light parallel to the optical axis OA is refracted by the second inclined surface 3b, passes through the light reflecting portion, and is emitted from the emission surface 1b. Since the light diffusion sheet 10 of the present invention can transmit, totally reflect, and refract the incident image light as described above, the image light can be diffused at various angles as compared with the prior art. The graph of light diffusion characteristics (particularly light diffusion characteristics of horizontal diffusion) can be made gentle. In the present invention, “a part of the image light is diffused by total reflection” means that the light incident on the light diffusion sheet passes through the region A as it is, and is refracted and transmitted through the regions C1 and C2. This is because the light diffused by total reflection is incident on the regions B1 and B2 corresponding to the first inclined surface 3a.

  Hereinafter, each component of the light diffusion sheet of the present invention will be described in detail. In each drawing explaining the present application, hatching (hatched lines) representing a cross section is omitted as appropriate.

(Base material)
The substrate 11 is a film-like or sheet-like transparent member, and for example, a polyethylene terephthalate film or a polycarbonate film is used. Although the thickness of the base material 11 is not specifically limited, Usually, it is about 0.1 mm-0.5 mm.

(Light diffusion part)
The light diffusing unit 12 is formed by alternately arranging the light reflecting units 2 and the light transmitting units 4, and is normally provided on the substrate 11 as shown in FIG. 1. The light reflecting portions 2 are arranged at a constant pitch in the width direction on the surface on the observer side that becomes the emission surface 1b and in a plurality of grooves 15 having a substantially V-shaped cross section extending in the vertical direction in plan view. It is formed by filling a resin having a refractive index lower than the refractive index of the light transmitting portion 4 and has a substantially wedge-shaped cross section as a whole. The light reflecting portions 2 are arranged in the width direction at a pitch in the range of, for example, 50 to 150 μm. On the other hand, the light transmitting portion 4 is formed of a resin having a refractive index higher than that of the light reflecting portion 2 and has a substantially trapezoidal cross section.

FIG. 2 is a detailed explanatory view of the light reflecting portion. As shown in FIG. 2, the light reflecting portion 2 includes a first inclined surface 3a having an angle θ1 at which the opposing surface forming the groove 15 is located on the incident surface 1a side and totally reflects the image light, and the first inclined surface 3a. It is formed by the inclined surface 3 and a second inclined surface 3b consisting of angle theta ₂ which refracts and transmits the image light located so as to connect the exit surface 1b and.

The first inclined surface 3a is an inclined surface constituting the interface between the light reflecting portion 2 made of a low refractive index material and the light transmitting portion 4 made of a high refractive index material, and is an image incident parallel or substantially parallel to the optical axis OA. It is formed at an angle θ ′ ₁ (unit: “degree (°)”) exceeding the critical angle with respect to the normal line CL ₁ of the first slope 3 a so as to totally reflect light.

An inclination angle θ _{1 with} respect to a plane including the emission surface 1b of the first inclined surface 3a (a plane orthogonal to the optical axis OA) is a point P at which the extension line L ₁ of the first inclined surface 3a intersects the plane. point the point of incidence of the first inclined surface 3a of the parallel image light VR ₁ in the axial OA Q, when the intersection of the perpendicular L ₂ and the plane passing through the point Q out of the normal to the plane and a point R, the angular QPR It is represented by At this time, since the value of the angle PQR is (90−θ ₁ ) °, the inclination angle θ ₁ of the first inclined surface 3a is the same value as the incident angle θ ′ ₁ of the image light VR ₁ at the point Q. Therefore, the incident angle theta _'1 of the image light VR ₁ to the first inclined surface 3a is to exceed the critical angle, the inclination angle theta ₁ of the first inclined surface 3a is formed at an angle greater than the critical angle.

Similarly to the first inclined surface 3a, the second inclined surface 3b is an inclined surface constituting an interface between the light reflecting portion 2 made of a low refractive index material and the light transmitting portion 4 made of a high refractive index material. 3b is an angle θ ′ ₂ (unit of less than a critical angle) with respect to the normal line CL ₂ of the second inclined surface 3b so that the image light incident parallel or substantially parallel to the optical axis OA is refracted and transmitted without being totally reflected. Are formed in degrees (°). The inclination angle θ _{2 with} respect to the plane including the exit surface 1b of the second inclined surface 3b (the plane orthogonal to the optical axis OA) is the same as the first inclined surface 3a, and the image incident on the second inclined surface 3b. is the same value as the angle of incidence theta _'2 light VR _2. Accordingly, as the incident angle theta _'2 of the image light VR ₂ of the second inclined surface 3b is less than the critical angle, the inclination angle theta ₂ of the second inclined surface 3b is formed at an angle less than the critical angle.

The inclination angle θ ₁ of the first inclined surface 3a is within a range of about 72 to 86 ° depending on the difference in refractive index between the light transmitting portion 4 made of a high refractive index material and the light reflecting portion 2 made of a low refractive index material. It can be selected as appropriate. Also, the inclination angle θ ₂ of the second inclined surface 3b is about 60 to 70 ° depending on the difference in refractive index between the light transmitting portion 4 made of a high refractive index material and the light reflecting portion 2 made of a low refractive index material. It is preferable to select appropriately within the range. In addition, the inclination angle θ ₁ of the first inclined surface 3 a and the inclination angle θ ₂ of the second inclined surface 3 b in such a range are such that the refractive index of the high refractive index material constituting the light transmitting portion 4 is the light reflecting portion, as will be described later. 2 is preferably applied when the refractive index is 1.02 to 1.25 times the refractive index of the low refractive index material constituting 2. At the interface having such a refractive index difference, by setting the first inclined surface 3a within the range of about 72 to 86 °, the image light incident on the first inclined surface 3a can be totally reflected, and the second inclined surface 3b is set to 60 to 60 °. By setting the angle within the range of about 70 °, the image light incident on the second inclined surface 3b can be refracted and transmitted.

  As the resin material constituting the light transmission part 4, for example, acrylate resins such as urethane acrylate and epoxy acrylate are preferably used. As this resin material, one having a refractive index higher by 1.02 to 1.25 times than the resin material constituting the light reflecting portion 2 is selected. For example, a urethane acrylate or epoxy acrylate radiation curable resin having a refractive index of 1.55 is preferably used.

  On the other hand, as a low refractive index resin material constituting the light reflecting portion 2, for example, an acrylic, epoxy or urethane radiation curable resin is preferably used. As this resin material, a material having a low refractive index of about 1.46 to 1.50 satisfying the ratio in the above range as compared with the resin material constituting the light transmitting portion 4 is selected. For example, a urethane acrylate or epoxy acrylate radiation curable resin having a refractive index of 1.48 is preferably used.

  The light reflecting portion 2 may contain a light absorbing material. The light reflecting portion 2 containing the light absorbing material absorbs stray light that has entered the light diffusing sheet 10 or stray light generated in the light diffusing sheet 10 and absorbs external light that has entered the light diffusing sheet 10 to increase the contrast. It works to improve and functions as a so-called black stripe pattern (BS pattern). As the light absorbing material, light absorbing particles such as carbon black, and achromatic materials such as black and gray such as black pigments or black dyes are preferably used. A material that selectively absorbs a specific wavelength in accordance with the characteristics may be used. Examples of the light absorbing particles include metal salts such as carbon black, graphite, and black iron oxide, colored organic fine particles, colored glass beads, and the like. Examples of the light absorbing dye include xanthene organic dyes such as Acid Red, and organic acid neodymium such as neodymium carboxylate.

FIG. 3 is a schematic ray path diagram showing how incident parallel light is diffused by the light diffusing unit 12. Figure 3 is six parallel light PR ₁ to PR ₆ at an incident angle of 0 ° on the incident surface 1a of the light diffusing portion 12 is described, of which the upper base and the lower base of the light transmitting portion 4 The parallel lights PR ₁ and PR _{2 that} have entered the region A (see FIG. 1) that overlap with each other in plan view are transmitted through the light transmission part 4 as they are and emitted from the emission surface 1b.

Regions B1, parallel light incident on the B2 _PR 3, PR ₄ corresponding to the first inclined surface 3a is the incident angle theta ₁ to the first inclined surface 3a exceeds the critical angle, it is totally reflected by the first inclined surface 3a The light exits from the exit surface 1b. At this time, when the adhesive layer 13 and the support plate 14 as shown in FIG. 1 are provided on the emission surface 1b, the light is refracted by the adhesive layer 13 and the support plate 14 and emitted to the viewer side.

The parallel lights PR ₅ and PR ₆ incident on the regions C1 and C2 corresponding to the second inclined surface 3b are refracted by the second inclined surface 3b because the incident angle θ ₂ to the second inclined surface 3b is less than the critical angle. The light is transmitted through the light reflecting portion 2 and emitted from the surface of the light reflecting portion 2 on the emission surface 1b side.

  In addition, about the refractive transmission in the 2nd slope 3b of the parallel light which injected into this area | region C1, C2, the various forms shown below can be mentioned in relation to a light absorber.

As a 1st form, the case where light-absorbing particles, such as carbon black mentioned above, are contained in the light reflection part 2 and the light reflection part 2 is given light absorption can be mentioned. As shown in FIG. 4, the light reflecting portion 2 of this form is formed by filling the grooves 15 with a low refractive index translucent resin including the light absorbing particles 5. In this form, it is preferable that the average particle diameter of the light-absorbing particles 5 to be contained is larger than the height h from the emission surface 1b to the intersection S where the first inclined surface 3a and the second inclined surface 3b intersect. Thus, the second inclined surface 3b less light absorbing particles 5 that are present in the vicinity of which are formed at an angle theta ₂ to refract transmitted image light, as a result, image light refracted at the second slope 3b, the second inclined surface 3b It can be easily transmitted without being absorbed by the nearby light-absorbing particles 5. Since the height h from the exit surface 1b to the intersection S is usually in the range of 3 to 8 μm, the average particle diameter of the light-absorbing particles is in the range of 6 to 20 μm and larger than the height h. It is desirable that

  As a second mode, when the light reflecting portion 2 is made to contain achromatic material such as black or gray such as the black pigment or black dye described above, the light reflecting portion 2 has light absorption. Can be mentioned. The light reflecting portion 2 in this form is formed by filling the groove 15 with a light-transmitting resin mixed with a light-absorbing achromatic material. In this embodiment, the image light is refracted by the second inclined surface 3b and absorbed by the light absorbing material contained when passing through the light reflecting portion 2, but the height h from the exit surface 1b to the intersection S is set. By setting it within the range of 3 to 8 μm as described above, the degree of absorption can be reduced, and the light diffusion characteristics can be improved.

  As a third mode, after the light reflecting portion 2 is formed by filling the groove 15 with a low refractive index translucent resin without containing a light absorbing material in the light reflecting portion 2, the light reflecting portion 2 A mode in which a light absorption layer is formed on the plane on the emission surface 1b side and overlapping with the first inclined surface 3a facing in the groove 15 of the light reflecting portion 2 in a plan view can be given (see below). 7). In this embodiment, the image light is refracted by the second inclined surface 3b, passes through the light reflecting portion 2, and exits from the plane on the exit surface 1b side. On the other hand, stray light entering the light diffusion sheet 10 or stray light generated in the light diffusion sheet 10 is absorbed by a light absorption layer formed on a region overlapping the first inclined surface 3a in plan view. The light absorption layer absorbs external light that has entered the light diffusion sheet 10. Such a light absorption layer acts to improve contrast and functions as a so-called black stripe pattern (BS pattern).

Thus, six parallel light _PR 1 to PR incident on the light diffusing portion 12 _6, except that two parallel light _PR 1, PR ₂ is transmitted through the light transmitting portion 4 as it is, total reflection by the light reflecting portion 2 Alternatively, the light is refracted and transmitted at different angles. As a result, the graph of the light diffusion characteristic of the image light (particularly the light diffusion characteristic of horizontal diffusion) can be made gentler than that of the conventional light diffusion sheet in which the second slope 3b is not formed.

(Other forms of light diffusion part)
5 to 7 are schematic cross-sectional views showing other forms of the light diffusion portion. The light diffusion part 12a shown in FIG. 5 has the light reflection part 2 in which the tip 18 of the groove 15 that tapers toward the incident surface 1a has a flat shape. The light diffusing portion 12b shown in FIG. 6 has a form in which the resin filling the groove 15 is formed as a thin layer 19 on the emission surface 1b. At this time, the thickness of the layer 19 is preferably 2 μm or less.

  In addition, the light diffusing portion 12c shown in FIG. 7 is formed on a region having a width W that overlaps the first inclined surface 3a facing in the groove 15 of the light reflecting portion 2 on a plane on the emission surface 1b side. The absorbent layer 20 is formed. Since the light absorption layer 20 acts as a BS pattern when a transmissive screen is formed using a light diffusion sheet, the contrast of an image can be improved. The light absorption layer 20 can be provided in a belt shape by applying and curing a black paint or black ink by a method such as a printing method or an ink jet method. As described above, even in the light diffusion sheet having the light diffusion portions having the respective forms shown in FIGS. 5 to 7, the graph of the light diffusion characteristics can be made gentle.

(Adhesive layer)
The adhesive layer 13 is formed by applying a resin composition for forming an adhesive layer on the light diffusion portion 12 and acts to adhere the light diffusion portion 12 and the support plate 14. As the resin composition constituting the adhesive layer 13, various resin compositions can be used. Specifically, a radiation curable resin composition is preferably used. For example, urethane (meth) acrylate is used as a prepolymer. Can be mentioned.

(Support plate)
The support plate 14 is a rigid plate-like member provided on the adhesive layer 13, and is preferably provided to support the light diffusion portion 12. As the support plate 14, an acrylic resin plate, an MS (methacryl-styrene copolymer) resin plate, a polycarbonate resin plate, or the like having a thickness range of 0.5 to 5.0 mm can be preferably used.

(Other configurations)
As mentioned above, although the main structure of the light-diffusion sheet of this invention was demonstrated, the following structures may further be added to the light-diffusion sheet of this invention.

  The light diffusing sheet 10 of the present invention can contain a light diffusing material for controlling light diffusibility. Specifically, it can be contained in one or more of the substrate 11, the light transmission part 4, the adhesive layer 13, and the support plate 14. The light diffusing material that can be contained may be a light diffusing material such as light diffusing fine particles generally used for optical sheets. Styrene resin fine particles, silicone resin fine particles, acrylic resin fine particles, MS resin (methacrylic- Styrene copolymer resin) Organic fine particles such as fine particles, barium sulfate fine particles, glass fine particles, aluminum hydroxide fine particles, calcium carbonate fine particles, silica (silicon dioxide) fine particles, titanium oxide fine particles, glass beads, and other inorganic fine particles. These 1 type (s) or 2 or more types can be contained in the resin. By including such a light diffusing material, the light diffusing property can be further improved, and as a result, the viewing angle can be expanded.

  Further, an antireflection layer, a low reflection layer, a hard coat layer, an antistatic layer, an antiglare layer, and contamination prevention are provided on the viewer side surface of the light diffusion sheet 10 of the present invention, that is, the viewer side surface of the support plate 14. A layer, a polarizing filter layer, an electromagnetic wave shielding layer, or the like may be provided as needed, or one or more layers. Further, the surface roughness of the surface on the viewer side of the support plate 14 may be adjusted to have an antireflection function or an antiglare function. The support plate 14 provided with such a functional layer or functional surface acts as a front plate located at the forefront on the viewer side of the projection television.

  Moreover, the uneven | corrugated shape may be provided in the light source side surface of the light-diffusion sheet of this invention, ie, the light source side surface of the base material 11. As the uneven shape, for example, an optical element 21 as shown in FIG. 8 can be cited. The optical element 21 is provided with a chevron-shaped inclined surface on the light source side surface of the base material 11, and the incident light incident from the light source side of the base material 11 is refracted by the optical element 21, and its refraction. The light passes through the light transmission part 4 at an angle different from that of the parallel light, and a part of the light is totally reflected by the first inclined surface 3a and emitted from the emission surface 1b. Therefore, the light diffusing sheet shown in FIG. 8 is preferable as a constituent member of a transmission screen having a wide viewing angle because the angular distribution of outgoing light emitted to the viewer side is wider than when the optical element 21 is not provided. Used. Note that the optical element 21 is not limited to the embodiment shown in FIG. 8, and a conventionally known element that exhibits the same effect can be applied.

  As described above, according to the light diffusion sheet of the present invention, the graph of the light diffusion characteristics of video light (particularly the light diffusion characteristics of horizontal diffusion) can be made smooth, so that the viewing angle characteristics are improved. be able to. In particular, it can be preferably used in a rear projection type display device using a single light source that clearly displays still images and characters.

(Production method of light diffusion sheet)
Next, the manufacturing method of a light-diffusion sheet is demonstrated. FIG. 9 is a process diagram showing an example of a method for producing a light diffusion sheet of the present invention.

  First, the light diffusion sheet of the present invention includes a mold roll 111 and a base material 112 that advances along the peripheral surface of the mold roll 111 while rotating the mold roll 111 in which the shape of the groove is formed on the peripheral surface. In the meantime, a radiation curable resin composition 113 for forming a light transmission part is supplied from a supply device 123, and then a light transmission part is formed by irradiating ultraviolet rays with a radiation source, for example, a UV lamp 114, and then a mold roll 111. Then, the intermediate member 115 is formed. Next, for example, a radiation curable resin composition 116 containing light-absorbing particles is supplied from the supply device 124 to fill the grooves of the intermediate member 115, and further irradiated with ultraviolet rays from a radiation source such as a UV lamp 117 to reflect light. Forming part. At this time, filling of the groove of the intermediate member 115 with the radiation curable resin composition 116 including the light-absorbing particles is performed by scraping off the excess resin composition using the doctor 118. Although not shown in FIG. 9, a support plate is further bonded thereon via an adhesive layer, and cut into a predetermined size to produce the light diffusion sheet of the present invention.

  Reference numeral 119 denotes a film-like or sheet-like base material wound up in a roll shape, and reference numeral 120 denotes a nip roll for pressing the radiation curable resin composition 113 for forming a light transmission part against the mold roll surface. Reference numeral 121 denotes a peeling roll for peeling the intermediate member 115 having a cured light transmission portion, and reference numeral 122 denotes a backup roll for efficiently removing an excess resin composition by the doctor 118.

(Transparent screen)
10 and 11 are schematic perspective views showing examples of the transmission screen of the present invention. The transmission screen of the present invention has the light diffusion sheet of the present invention described above. Specifically, a Fresnel lens member that deflects light from a single light source into substantially parallel light is provided on the image light source side, and a light diffusion sheet that diffuses the deflected substantially parallel light and adjusts the viewing angle is provided on the viewer side. It is to be prepared.

  More specifically, the transmissive screen 40 shown in FIG. 10 includes a refractive type circular Fresnel lens member 30 having a Fresnel center on the sheet surface and the above-described light diffusion sheet 10 of the present invention. In addition, the transmission type screen 50 shown in FIG. 11 has a total reflection type circular Fresnel lens member 31 that does not have a Fresnel center on the sheet surface and the above-described light diffusion sheet 10 of the present invention attached via an adhesive layer. It is a combination. The transmissive screen may have a form in which a total reflection type Fresnel lens member 31 is disposed so as to face the base material 11 of the light diffusion sheet 10 (without an adhesive layer) (not shown). .

  The Fresnel lens member used in the transmission type screen of the present invention is formed with a fine pitch corresponding to a recent single light source, and the formation material thereof is the same radiation curable type as described in the above light diffusion sheet. Resin compositions, specifically radiation curable prepolymers such as urethane (meth) acrylate, polyester (meth) acrylate or epoxy (meth) acrylate, as appropriate, radiation curable monomers and photopolymerization initiators as reactive diluents A radiation curable resin composition blended with is preferably used. Such a Fresnel lens member is formed by casting the radiation curable resin composition into a shaping mold for a Fresnel lens and irradiating the substrate film placed thereon with radiation (for example, ultraviolet rays or electron beams). It can be carried out by curing the curable resin composition. Thereafter, the sheet is peeled from the shaping mold to produce a sheet-like Fresnel lens member.

  According to such a transmissive screen of the present invention, since the light diffusing sheet of the present invention is provided, a graph of light diffusing characteristics of image light (particularly horizontal light diffusing characteristics) can be made smooth. Angular characteristics can be improved. In particular, it can be preferably used in a rear projection type display device using a single light source that clearly displays still images and characters.

(Rear projection display)
12 and 13 are configuration diagrams showing an example of a rear projection display device equipped with the transmission screen of the present invention. FIG. 12 shows an example of a rear projection display device equipped with a transmissive screen having a circular Fresnel lens with the Fresnel center in the sheet plane. FIG. 13 shows a total reflection type with the Fresnel center outside the sheet plane. It is an example of a rear projection type display device equipped with a transmission type screen having a circular Fresnel lens.

  The rear projection display devices 60a and 60b are provided with transmissive screens 40 and 50 having the light diffusing sheet of the present invention as constituent members in the front-side window, and have relatively thin casings 61a and 61b. Light sources 62a and 62b are disposed at the bottom, and mirrors 63a and 63b that reflect light from the light sources 62a and 62b toward the transmission screens 40 and 50 as image light 64 are disposed on the inner surfaces of the rear walls of the casings 61a and 61b. Has been. The light sources 62a and 62b at this time are single tube type single light sources using LCD (Liquid Crystal Display) or DLP (Digital Light Processing). Since the light diffusing sheet of the present invention is used as a constituent member for the transmissive screens 40 and 50, an image having excellent viewing angle characteristics can be displayed on the transmissive screen. Reference numeral 65 denotes outgoing light.

(Liquid crystal display device)
Next, the liquid crystal display device of the present invention will be described. The liquid crystal display device of the present invention has the light diffusion sheet of the present invention as a viewing angle widening member disposed or bonded on the display surface of a display liquid crystal panel.

  FIG. 14A is a schematic cross-sectional view showing an example of the liquid crystal display device of the present invention. The illustrated liquid crystal display device 71 is electrically connected to the display liquid crystal panel 75, the backlight unit 76 disposed behind the display liquid crystal panel 75, and the display liquid crystal panel 75 and the backlight unit 76. And a control circuit 77 for controlling these operations. The display liquid crystal panel 75, the backlight unit 76, and the control circuit 77 are accommodated in a housing 79 having a stand unit 78. A light diffusion sheet 10 that is a viewing angle diffusion member is disposed on the entire surface of the housing 79.

  The display liquid crystal panel 75 includes, for example, a liquid crystal cell 81 having a large number of pixels, a polarizer 82 disposed on the back surface of the liquid crystal cell 81, and an analyzer 83 disposed on the front surface of the liquid crystal cell 81. Is done. The liquid crystal cell 81 is, for example, an injection port after injecting liquid crystal between a first transparent substrate 85 and a second transparent substrate 86 which are arranged in a state of being spaced apart from each other and whose periphery is sealed with a sealant 84. It is formed by sealing. The liquid crystal cell 81 may be of a vertical electric field type that controls the alignment of liquid crystal molecules by applying a voltage to electrodes disposed on the inner side surfaces of the first transparent substrate 85 and the second transparent substrate 86. In addition, a lateral electric field type that controls the alignment of liquid crystal molecules by applying a voltage to a plurality of electrodes disposed on the inner surface of the second transparent substrate 86 may be used.

  When the liquid crystal cell 81 is of the vertical electric field type, it does not appear in FIG. 14A, but on the inner side surface of the first transparent substrate 85, for example, one micro color filter corresponds to one pixel. Thus, the color filter array is formed, and the common electrode is formed so as to cover the color filter array and overlap with all the pixels in plan view. An alignment film is provided so as to cover the common electrode. Further, on the inner side surface of the second transparent substrate 85, for example, a large number of pixel electrodes are arranged in a matrix, and one signal line is provided corresponding to one column of pixel electrodes. One scanning line is provided corresponding to one row. Further, one switching element for controlling conduction between the signal line and the scanning line and the pixel electrode is arranged corresponding to one pixel electrode so as to cover the pixel electrode, the signal line, the scanning line, and the switching element. Thus, an alignment film is provided.

  The light diffusion sheet 10 is for improving the viewing angle characteristics in the horizontal direction in the liquid crystal display device 71, and is arranged such that the exit surface of the light diffusion portion faces the viewer. The light reflecting portion of the light diffusion sheet 10 extends in the vertical direction of the liquid crystal display device 71.

  FIG. 14B is a schematic cross-sectional view showing another example of the liquid crystal display device of the present invention. The liquid crystal display device 72 shown in FIG. 14 is shown in FIG. 14A in that the light diffusion sheet 10 is integrally joined on the display surface (on the analyzer 85) of the liquid crystal panel 75 for display. Other than 71, the other configuration is the same.

  FIG. 15 is a schematic cross-sectional view showing still another example of the liquid crystal display device of the present invention. The illustrated liquid crystal display device 73 is different from the liquid crystal display device 72 shown in FIG. 14B in that a touch panel 87 is provided on the exit surface of the light diffusing portion constituting the light diffusing sheet 10. Since the other structure in the liquid crystal display device 73 is the same as the structure of the liquid crystal display device 72 shown in FIG.14 (b), the description is abbreviate | omitted. The touch panel 87 is preferably a highly transparent one that does not interfere with the transmission of image light as much as possible. Since the liquid crystal display device 73 has the touch panel 87, it is easy to obtain a multi-function device.

  According to the liquid crystal display device using the light diffusing sheet of the present invention as a constituent member, it is possible to provide a rear projection display device or a liquid crystal display device having good light diffusion characteristics and a wide viewing angle.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1
A shaping roll having projections (convex portions) for forming grooves 15 having a pitch of 65 μm and a depth of 150 μm is prepared, and an epoxy acrylate-based UV curable resin is supplied to the shaping mold roll from a feeder. Supply and paste the 188μm thick PET film with a nip roll so that the resin is sandwiched between the shaping rolls, and then cure the UV curable resin by irradiating UV rays from the PET film side. Thus, a light transmission part having a refractive index of 1.55 (measured at a wavelength of 540 nm) was formed. After removing the cured intermediate member from the shaping roll, the intermediate member contains 20% by weight of light-absorbing particles (urethane filler added with carbon black, average particle diameter of 8 μm, standard deviation of particle diameter of 2 μm). The urethane acrylate-based ultraviolet curable resin was supplied from the supply device, and the excess resin was scraped off by a doctor, whereby the resin was filled in the groove 15 having a substantially V-shape (opening width: 35 μm). Subsequently, ultraviolet rays were irradiated from the PET film side to cure the ultraviolet curable resin to form a light reflecting portion having a refractive index of 1.48 (measured at a wavelength of 540 nm).

  The light reflecting portion has an average height of 150 μm and an output surface side width of 35 μm, the first slope has an average inclination of 80 °, the second slope has an average inclination of 60 °, the first slope and the second slope The average height h to the intersection with the slope is 5 μm. Further, the light transmission portion has a thickness of 185 μm in the region A (see FIG. 1), and a width of an emission surface through which light is transmitted is about 30 μm.

  An acrylic UV curable resin material having adhesive properties is applied on the light exit surface of the light diffusing section, and a support plate is placed thereon, followed by irradiation with UV light from the support plate, and a refractive index of 70 μm in thickness. The support plate was bonded through the 1.48 adhesive layer. The support plate used was a 2 mm thick molded resin material made of MS (methacryl-styrene copolymer) resin by an extrusion molding method. Thus, a light diffusion sheet having a length of 600 mm and a width of 800 mm was produced.

(Comparative Example 1)
In the light diffusion sheet of Example 1, the light diffusion sheet of Comparative Example 1 was produced in the same manner as in Example 1 except that the first slope and the second slope were changed to a straight line having an inclination angle of 80 °.

(Evaluation of light diffusion characteristics)
The light diffusion sheets of Example 1 and Comparative Example 1 were combined with a Fresnel lens sheet having a pitch of 0.112 mm and mounted on a 50-inch projection television (HLM 5065W, manufactured by Samsung Electronics Co., Ltd.) equipped with a 50 W-DLP light source. Observation was performed from a position 2.5 m away from the screen, and a horizontal diffusion characteristic and a vertical diffusion characteristic were measured every 10 ° from an outgoing light angle of 0 ° to 60 ° using a minute declination luminance meter.

  In Example 1, the vertical viewing angle was 12 ° up and down, and the horizontal viewing angle was 25 ° left and right. A graph of the light diffusion characteristics of Example 1 is shown in FIG. As can be seen from this figure, in this transmissive screen, it was confirmed that when the viewing angle was changed along the horizontal direction, the luminance changed gently and the viewing angle characteristics in the horizontal direction were improved. . On the other hand, since the comparative example 1 has optical characteristics having three peaks as shown in FIG. 18B, band-like unevenness was observed depending on the observation angle in the horizontal direction.

It is a schematic cross section which shows an example of the light-diffusion sheet of this invention. It is detailed explanatory drawing about a light reflection part. It is a typical ray path diagram which shows a mode that the incident parallel light diffuses in a light-diffusion part. It is explanatory drawing of the relationship between the average particle diameter of a light absorptive particle, and the height from the output surface to the intersection where a 1st slope and a 2nd slope cross. It is a schematic cross section which shows the other form of a light-diffusion part. It is a schematic cross section which shows the other form of a light-diffusion part. It is a schematic cross section which shows the other form of a light-diffusion part. It is a schematic cross section which shows another example of the light-diffusion sheet of this invention. It is process drawing which shows an example of the manufacturing method of the light-diffusion sheet of this invention. It is a schematic perspective view which shows an example of the transmission type screen of this invention. It is a schematic perspective view which shows another example of the transmission type screen of this invention. It is a block diagram which shows an example of the rear projection type display apparatus with which the transmission type screen of this invention was mounted | worn. It is a block diagram which shows another example of the rear projection type display apparatus with which the transmission type screen of this invention was mounted | worn. It is a schematic cross section which shows the example of the liquid crystal display device of this invention. It is a schematic cross section which shows another example of the liquid crystal display device of this invention. 3 is a graph of light diffusion characteristics of Example 1. It is a schematic sectional drawing which shows an example of the conventional total reflection type lenticular lens sheet. It is an example of the light ray path | route figure of the transmissive screen using the conventional total reflection type lenticular lens sheet, and the graph of a light-diffusion characteristic.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Incident surface 1b Output surface 2 Light reflection part 3 Slope 3a 1st slope 3b 2nd slope 4 Light transmission part 5 Light-absorbing particle 10 Light diffusion sheet 11 Base material 12, 12a, 12b, 12c Light diffusion part 13 Adhesive layer 14 Support plate 15 Groove 16 Upper base 17 Lower base 18 Groove tip 19 Layer on exit surface 20 Light absorption layer 21 Optical element 30, 31 Fresnel lens member 32 Adhesive layer 40, 50 Transmission type screen 60a, 60b Rear projection type display device 61a, 61b Case 62a, 62b Light source 63a, 63b Mirror 64 Video light 65 Emission light 71, 72, 73 Liquid crystal display device 75 Liquid crystal panel for display 76 Backlight part 77 Control circuit 78 Stand part 79 Case 81 Liquid crystal cell 82 Polarization Element 83 Analyzer 84 Sealant 85 First transparent substrate 86 Second transparent substrate 87 Touch panel 111 type B 112 Base material 113 Radiation curable resin composition 114 UV lamp 115 Intermediate member 116 Radiation curable resin composition containing light-absorbing particles 117 UV lamp 118 Doctor 119 Film-like or sheet-like base material 120 Nip roll 121 Peeling roll 122 Backup roll 123 Supply device 124 Supply device B1, B2 Area corresponding to the first slope C1, C2 Area corresponding to the second slope OA Optical axis A Area where the upper and lower bases of the light transmission part overlap in a plan view CL ₁ Normal of the first slope CL ₂ Normal of the second slope θ ₁ Inclination angle of the first slope with respect to the plane including the exit surface θ ₂ Inclination angle of the second slope with respect to the plane including the exit surface θ ′ exceeding _one critical angle the angle theta _'2 perpendicular VR ₁ first slope passing through the point Q out of the normal to the critical angle following the angle L ₁ first slope of the extension line L ₂ plane Extension parallel image light P first inclined surface to the optical axis incident on the parallel image light VR ₂ second inclined surface to the optical axis of morphism is the first slope of the parallel image light to Q optical axis that intersects the plane Incident point R Intersection of the plane perpendicular to the plane Q passing through the point Q and the plane PR _{1 to} PR ₆ Parallel light incident at an incident angle of 0 ° on the incident surface of the light diffusing section S First slope and second slope Intersection point h Height to intersection point S where the first and second slopes meet W The width of the light diffusion part overlapping in plan view with the first slope facing in the groove of the light reflecting part

Claims (12)

At least a light diffusing portion for diffusing a part of the image light incident from one surface in the thickness direction by total reflection and emitting it from the other surface side, and the light diffusing portion from the other surface to the one side Alternating between a light-reflecting portion having a substantially wedge-shaped cross-section in which a groove tapering toward the surface is filled with a resin and a light-transmitting portion having a substantially trapezoidal cross-section provided between the light reflecting portions and transmitting the image light In the light diffusion sheet formed side by side,
The refractive index of the resin filled in the groove is lower than the refractive index of the light transmission part,
A facing surface forming a groove of the light reflecting portion is located on the one surface side so as to connect the first inclined surface having an angle for totally reflecting the image light, and the first inclined surface and the other surface. The light diffusion sheet is formed by an inclined surface including a second inclined surface having an angle at which the image light is refracted and transmitted.   The light diffusion sheet according to claim 1, wherein the light reflecting portion is formed by filling the groove with a resin containing light absorbing particles.   The light diffusion sheet according to claim 2, wherein an average particle diameter of the light-absorbing particles is larger than a height from the other surface to an intersection where the first slope and the second slope intersect. .   A light absorption layer is formed on a region of the other surface of the light reflecting portion that overlaps the first inclined surface facing in the groove of the light reflecting portion in plan view. Item 4. A light diffusion sheet according to Item 1.   A transmissive screen comprising the light diffusion sheet according to claim 1.   The transmissive screen according to claim 5, wherein a Fresnel lens sheet is disposed or a Fresnel lens portion is bonded to the side on which the image light is incident.   The transmissive screen according to claim 6, wherein the Fresnel lens sheet or the Fresnel lens unit includes a total reflection Fresnel lens.   The transmission screen according to any one of claims 5 to 7, wherein a support plate is disposed or joined to a side from which the image light is emitted.   The transmissive screen according to any one of claims 5 to 8, wherein a touch panel is provided on the outermost surface on the side from which the image light is emitted.   5. A rear projection display device equipped with a transmissive screen, comprising the light diffusing sheet according to claim 1 as a constituent member of the transmissive screen. apparatus.   In the liquid crystal display device having a display liquid crystal panel, the light diffusion sheet according to any one of claims 1 to 4 is provided as a viewing angle widening member disposed or bonded on a display surface of the display liquid crystal panel. A liquid crystal display device characterized by the above. The liquid crystal display device according to claim 11, wherein a touch panel is provided on an outermost surface of the display surface.

Images